BUILD A VIDEO TELEPHONE! ;Jj 48783 CHNOLOGY - VIDEO - STEREO - COMPUT UILD A MA IETER- X v etermine your exi otentially harirTf-iii Eb lagnetic radiationvs\ C-FIELD SUILD A 40-WATT POWEIT MVERTER ' 'ower 120-volt AC devices ^om 12 volts DC! XPERIMENTS IN VOICE , EECOGIMITION Jingle IC can be used in an ssortment of projects APRIL 1991 WITCHING EGULATORS he basics of switching lower supply design UILD A STEPPER 10TOR ROBOT 'ased on the 8748 licrocon trailer II $2.95 U.S. $3.75 CAN GERNSBACK ~ FLUKE AND PHILIPS - THE GLOBAL ALLIANCE IN TEST & MEASUREME FLUKE philif High Resolution Digital Meter: 4000 count digital readout; 30,000 counl mode (Fluke 87) lor 4ra digit resolution Back I It display: Makes il easy lo read the DMM in dark, cramped quarters. Automatically shuts_ oft after 68 seconds lo save the battery. Analog Meter: High-speed analog display updates 40 times/ second— as last as the eye can follow; XIO Zoom bargraph mode [Fluke 83 and 85) makes high resolution offset measurements a snap. Recorder; records mrniinurre and maximums, plus Hue arithmetic average; audible Uin Max Alert; selectable response limes— 1 second and 100 ms [all models) plus 1 ms Peak Min Max (Fluke 87) Holster with Flex Stand": Protects meter and provides lest lead storage. Flexible leg allows meter lo be hung from peg, bent around a pipe, or used almost anywhere. FLUKE 83 FLUKE 85 FLUKE 87 Wstts r ohms. am?s. diodtelesl , aud-blecotti nui ly. I >eq uEncyand duty cycle ciwacilanti'lbuciiiHold? relative; prDtecti whoisJer wilh F lex-Sland ""■ A J199" 1229" 0.3%- basic dc accuracy O.l^basLCdcac^ra^ SkHiacv 20ktaacV Analog uargraph Aiaisg airgraph and loom and Joorr Three yea r warranty Three year warranty S289- C iH, basic dc«ccu'3;.> .::-■-■., Htgfl istf uliw KtfOg panlEr tfUMroat TO PEAK Mi N MAX 4 : digd mode Bjiik-Mpny Three year warranty •Suqsbm US usuries Frequency counter: Accurate down to 0.5 Hz; also measures duty cycle Capacitance meter: Autoranging, wilh manual ranging at the touch of a button i ulti-Me^ Meet the meter that brings an entire test bench to your job. The versatile Fluke 80 Series do-just-about- everything "Multi" Meter. It offers everything you'd expect from an advanced handheld DMM, plus a lot you'd find only in dedicated instruments. Plus Fluke-exclusive features you can't buy any- where else. All built with the most advanced surface mount design and single-chip ASIC technology for a thinner, tougher, more reli- able package. There's a fully annunciated display for clear operation, Duty cycle function, High-speed analog indicator. A protective holster with innovative Flex-Stand™ for easy, adaptable operation. Audible Input Alert'" to reduce the risk of damage to the meter, the user, and the unit being tested. Plus the strongest warranty in the business. All good reasons to move up lo the truly- multi Fluke 80 Series today, You'll find 80 Series DMMs at your Fluke distributor. For immediate, off-the-shelf delivery. Call CIRCLE 121 ON FREE INFORMATION CARD 1-8Q.0-44-FLLIKE, ext. 33 tor the name of your nearest distributor, John Flute Mlj. Co. ire. PO. Ben 3090 NVS Z50C Ewwi WA 98206 US (206) 347-5400 CANADA 416^0-7600 OTK3 COKTBtS B06) 356-S500 © Copyright 19K John Flute Mfc Co., toe All ritfm resenea ft M).M ■ mil ■■■ *__,.ta_ _•_, PAGE 43 PAGE 45 98 Advertising and Sales Offices 98 Advertising Index 12 Ask RE 13 Letters 88 Market Center 26 New Lit 22 New Products 4 What's News > J) ON THE COVER w o z o cc & LU o □ < If you've been worrying that just about everything in your life can cause cancer, at least you can stop worrying that you're paranoid. Be- sides smog, red meat, cigarettes, radon gas, etc, studies have shown an increase in cancer rates in those who are exposed to even low-level magnetic fields. Electro-magnetic fields (ELF) are created by the gen- eration, distribution, and use of elec- tricity and electronic devices — meaning that you're exposed to it at home from everything ranging from your blow dryer to your microwave, as well as at work. Those who live close to power-distribution substa- tions and power lines are consid- ered to be particularly at risk. To find out if you and your family and co- workers are being exposed to po- tentially hazardous ELF levels, build the portable ELF gaussmeter shown on page 33. THE MAY ISSUE GOES ON SALE APRIL 3. BUILD THIS RAM TESTER Verify that your memory is working properly and at the rated speed. BUILD THE PHOIM-COM Turn your telephones into a home intercom system. MICROCELL Is the "poor man's cellular network" the phone network of tomorrow? BUILD THE PULSE MATE A handheld pulse generator makes a handy troubleshooting tool. As a service to readers, RADIO -ELECTRONICS publishes available plans or information relating to newsworthy products, techniques and scientific and technological developments. Because of possible variances in the quality and condition of materials and workmanship used by readers, RADIO-ELECTRONICS disclaims any responsibility for the safe and proper functioning of reader-built projects based upon or from plans or information published in this magazine. Since some of the equipment and circuitry described in RADIO- ELECTRO NIGS may relate to or be covered by U.S. patents. RADIO- ELECTRONICS disclaims any liability for the infringement of such patents by the making, using, or sailing of any such equipment or circuitry, and suggests lhat anyone interested in such projects consult a patent attorney, RADIO-ELECTRONICS. (ISSN 0O33-7B62) April 1991. Published monthly by Gomsback Publications. Inc.. 500-8 Bi -County Boulevard. Farmingdsle, NY 11 735 Second-Class Postage paid at Farmingdale, NY and additional mailing offices. Second-Class mail registration No. 9242 authorized at Toronto. Canada. One-year subscription rata U.S.A. and possessions SI 7.97, Canada $23-97, all other countries $26.97. All subscription orders payable in U.S.A. funds only, via international postal money order or check drawn on a U.S.A. bank. Single copies $2.95. 1991 by Gernsback Publications, Inc. All rights reserved. Printed in U.SA POSTMASTER; Pleasn send address changes to RADIO-ELECTRONICS. Subscription Dept.. Box 55115, Boulder, CO B0321-5I15. A stamped self-addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return is desired should they he rejected. We disclaim any responsibility for the loss or damage of manuscripts and/or artwork or photographs while in our possession or otherwise - aciEEtronics H ugo G ernsback (1 8B4- 1 967) found er Larry Stockier, EHF, CET, editor-in-chief and publisher EDITORIAL DEPARTMENT Brian C. Fenton, editor Marc Spiwak, associate editor Kim Dunleavy, assistant technical editor Teri Scaduto, assistant editor Jeffrey K. Holtzman computer editor Robert Gross Matt, circuits editor Larry Klein, audio editor David Lachenbruch contributing editor Don Lancaster contributing editor Kathy Terenzi, editorial assistant ART DEPARTMENT Andre Duzant, art director Injae Lee, illustrator Russell C. True) son, illustrator PRODUCTION DEPARTMENT Ruby M. Yee, production director Janice Box, editorial production Karen S. Brown advertising production Marcetla Amoroso production assistant CIRCULATION DEPARTMENT Jacqueline P. Cheeseboro circulation director Wendy Alanko circulation analyst Theresa Lombardo circulation assistant Michele Torrillo. reprint hookstore Typography by Mates Graphics Cover photo by Jack McConnell and Diversified Photo Services Radio-Electronics is indexed in Applied Science & Technology Index and Readers Guide to Periodical Liter- ature, Microfilm & Microfiche editions are available. Contact circulation depart- ment for details. Advertising Sales Offices listed on page 98. Radio -Electronics Executive and Administrative Offices 1 516-293 3000. SubscriberCustomerService: 1-800-288-0652. Order Entry for New Subscribers: 1 800-999 7139. £1 Ji^m AudJi \^J Bureau ol Circulation Talking Multimeter. Press a but- ton on the probe and this meter calls out the reading while display- ing it on a high-contrast LC display. Full auto-ranging, continuity sounder, diode-check mode. Low- battery and over-range indicators. #22-164 99.95 "HOTLINE" SPECIAL-ORDER SERVICE Your nearby Radio Shack stocks over 1000 popular electronic parts and can special-order many items from our main warehouse— ICs, tubes, semiconduc- tors, phono cartridges and styii. even SAMS" manuals. We can also supply replacement batteries for cordless phones, computer memory, transceivers, pagers and more. Service is fast and there is no postage charge. (1) Universal Breadboard. Our best! Molded 2'/* x 6V2" board on 7x 4" steel base with rubber teel and three binding posts. #276-169 19.95 (2) Breadboard Jumper Wire Kit. Our 140-piece set of ready-to-use hookup wires. #276-173 4.95 (1) High-Speed 12VDC Motor. Up to 15,200 RPM at no load. About 2" long (with shaft). #273-255 . . 2,99 {2) 12VDC Brushless Micro Fan. For cooling mobile equipment and hum-sensitive circuits. Rated 4.6 CFM. 150 mA. #273-244 . . . 17.95 *S- [1] A (D [4) (1) Adjustable Project Holder. Our extra-sturdy "Helping Hands" holder sim- plifies soldering, gluing and assembly work. #64-2093 B.19 (2) Dual -Wattage Soldering Iron. Go from 15 to 30 watts with the flick of a switch. 8 33 VIDEO NEWS What's new in the fast-changing video industry. DAVID LACHEHBRUCH • HDTV Goes Digital. It now seems fairly certain that the high-defi- nition TV system chosen for the United States will be digital. Zenith is the latest to develop a digital trans- mission system, the third atl-digital system to be proposed for testing by the Advanced Television Test Center. While Zenith's earlier HDTV system was the first to be partially digital (it digitized low-Frequency signals), General Instrument actually pro- posed the first all-digital system last spring. That was followed by a sec- ond digital system, proposed by the Advanced TV Research Consortium consisting of NBC, Philips, David Sarnoff Research Center, and Thom- son Consumer Electronics. Zenith's new digital HDTV system was developed jointly with AT&T's Bell Telephone Laboratories and was said to be more compatible with dig- ital telecommunications, computers, and interactive systems. Zenith said digital circuitry will increase the cost of receivers perhaps "a few hundred dollars" over the $500 premium it had originally estimated HDTV sets for, because of the hybrid system stan- dard NTSC receivers would be using. * Interactive Dispute. Format battles are a fact of life in consumer electronics, and the next one proba- bly will be in the CD-based interactive video field. Commodore Dynamic Total Vision (CDTV) system, based on the Amiga computer, apparently will be the first compact disc-based interactive system to reach the mar- ketplace. The hardware, to be priced less than $1,000, is scheduled to be in some stores this spring, and up to 100 software programs are promised this year. CDTV combines audio and limited-motion video with computer technology to give consumers ac- cess to such things as encyclope- dias, games, atlases, and cook- books. But as usual, there will be competi- tion from a non-compatible system. Compact Disc-Interactive (CD-I), sponsored by Philips, Matsushita and Sony, is the best-known interac- tive system, but unfortunately it will require a different player and different discs from CDTV, CD-I is scheduled to hit the marketplace next fall. Like CDTV, it will provide limited video ac- tion — either half-screen full-motion or full-screen motion at half the normal TV frame rate — but Philips promises that a 1992 version will provide full- frame full-motion video. Philips prom- ises to supply add-ones to adapt the first machines to full-motion full- frame when the new system is avail- able, and says all programs will be "forward compatible" from the start. There is considerable confusion as to whether the new interactive media will open up a large new field combin- ing audio, video and books — or whether they will be just another con- sumer product to lay an egg. Almost certainly, we'll know the answer be- fore 1991 is out. • Interchangeable Camcorder Lenses. Four of Japan's largest camcorder manufacturers have agreed on a system of lenses for so- phisticated high-end camcorders. The system can be applied to any format— VHS, VHS-C, 8mm, and Beta — and is designed for the ad- vanced videophile or professional camcordist. It's called Video Lens CVL) and involves standard contact points on the camcorder body and lens, and microprocessors in each part of the combination, so that infor- mation on iris, exposure speed, auto- focus and so on can be communi- cated between the lens and cam- corder body. The system was developed jointly by Canon, Hitachi, Matsushita and Sony. The first version has been un- veiled by Canon in an ultra-sophisti- cated high-band 8mm (Hi8) model equipped with a 15 x zoom lens. Op- tions offered are an 8 x zoom lens and a 2 x extender, which will double the focal length of either lens. Because Canon is also a major manufacturer of 35mm still cameras, it's offering something extra — an adaptor which will permit the use of any autofocus lens made for its EOS single- lens reflex cameras with its camcorder. The new VL mount sys- tem will eventually permit the sepa- rate selection of camcorder bodies and lenses, mixing different brands and bringing so-called "home" video up to the sophistication level of film photography. • Scratch One, Add One. Despite the softening of the televi- sion set market in the U.S. last year, the picture tube boom goes on, but there has been one defection from the ranks of tube plant expansion. Philips, which had planned a new pro- duction facility in Saline, Michigan, abandoned the idea after the founda- tion had boon dug, citing economic conditions. But Mitsubishi, which builds big 35-inch tubes in Japan, said it was looking for a site to build them in the United States. Thomson Consumer Electronics recently com- pleted an expansion of its Indiana plant to make 35- and 31-inch tubes. Other new and expanded tube plants were completed orstarted in the U.S. last year by Matsushita, Toshiba, Hitachi and Sony. R-E CANON'S NEW 8mm camcorder with interchangeable lenses. Ma SYWI 1 ^ e£ i 1 i NTE specializes in "replacetivityr the science of getting things up and running again-fast! After all, downtime is costly, so no one can wait weeks on end for an OEM part to come in. With NTE, no one has to! One call gives you access to 3,550 top of the line universal replacement semiconductors that are cross-referenced to more than 240,000 original devices! Included in the NTE line are: bipolar transistors, integrated circuits, rectifiers, diodes, thyristors, optoelectronic devices, varistors, resistors, capacitors, and much, much more All are hacked by NTE's exclusive two-year warranty. For your copy of the NTE Technical Guide contact your local NTE distributor, or simply fill in the coupon below and send it to us today with a check or money order for S3.25 each. NTE ft WORLDWIDE REPUTATION FOR QUALITY, SERVICE AND VALUE Please rush me NTE Technical Guide and Cross Reference manual at $3.25 each. I have enclosed | my check or money order for a j total of $ | Name . I Company , Address _ City State Mail to: NTE. 44 T Fatrand St., Bloomfield, NJ 07003 . copies of the For the name of your nearest NTE distributor, call NTE: Toll Free: 1-800-631-1250 (incl. Canada) Tel: (201) 748-5089 • FAX: (201) 748-6224 CIRCLE 71 ON FREE INFORMATION CARD What's you ewi-B.eau •■fc 1U T81iJ3«e.U0 T^r= 15, SRCf II. fl SAUt wwv A A A A Analyzing TV and complex video signals? Testing telecommunications signals? Uncovering elusive glitches? 10 .. tpi 2. it U UE*> * lOflnt J. V> n - i nm - **'- ■ '■'- i ,,, Finding abeiratioiis buried within a signal? You can't depend on banner specs alone to solve problems like these. Whether you're trying to measure waveform parameters or analyze long data streams, identify infrequent events or track down glitches as narrow as 2 ns — there's all the difference between the depth of Tek troubleshooting and the trade-offs in other DSOs that compromise your results. Spec for spec, feature for feature, no other company offers the credentials Tek does to Capturing single-shot events? :OB)ii 3.72 U? UEIT Krl l.ee U 280)11 Automatic PASS/FAIL testing? effectively match DSO performance to your application needs. Whatever your criteria, you'll find a perfect solution in our line of problem-solving portable DSOs, from 10 to 500MS/S. Select the features to support your application. Tek DSOs offer a diverse set of capabilities including peak detect to uncover elusive glitches. Fast update rate for live signal display. Combined analog/digital operation for real-time verification of your Copyright <&- J 990. Tektronix, Inc. All rights reserved. BOB- 125 I problem? flUNB.'riMu Riiii-B.eec- ii=ij.aos»is ;REr ? sflUE SREF ! A SftUE ACCPEjK 8.5»s Chapcierizing signal noise? pehde i c e.a»s Capturing and analyzing long data streams? Measuring timing relationship between signals? chi gta.u 5»*» S3J.U Ut( lJD.io.it VIHDOW ■ CHI WIBIJl ■ «.«»• ferfoiming (iomplex measurements automatical!)'? Expanding glitches for close analysis? CU*30* FUHCTlOlt «OLTJ 2IMJ UtT SLOft »'TI» Windowing in on signal details? signal. Or Gave on Delta to automatically verify that all parts rf your si^ial fall within prescribed limits. Best of all, M's line of 100 MS/s digitizing scopes start at just $3995. To find out which Tek scope is right for you, contact pour Tek representative, return the card or call Tek direct. We can answer your questions and show you a scope that doesn't just look good on paper. It makes your oughest troubleshooting challenges routine. 1-800426-2200 One company measures up. Tfektronix CXJMWTTED ITl EXCELLENT CIRCLE 92 ON FREE INFORMATION CARD I ASK R-E Write to Ask R-E, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale. NY 11733 __ 1 WIND-SPEED READ I recently built a 2-digit LED counter using a 7490 decade counter and a 7447 display driver. I want to use it for an anemometer but I don't know what to use to make the dis- play read up and down as the wind speed changes. Any ideas? — L. Fiedler, Garden Grove, CA You haven't sent me the schematic or block diagram for the circuit you want to build, so I'm not sure exactly what you have in mind. There are, however, a few things you can try. The most straightforward thing to do is to replace the 7490 with a 74190. That counter is similar to the one you're using, but it can count both up and down. The count direc- tion is determined by putting either a low or a high on the down/up pin (pin 5). A low will make the 74190 count up and a high will make it count down. A pinout diagram of the 74190 is shown in Fig. 1. Since the chip can only handle a maximum count of ten, you might consider using two of them cascaded together. That would give you a max- imum count of 99 and, should the wind speed exceed that, the circuit will more than likely be the least of your worries. The 74192 is another up/down de- cade counter that can be used in your circuit. It has the advantage of a mas- ter clear input and is a bit easier to use when you want to cascade two chips to increase the counting range. Both the 74190 and the 74192 are cheap and available so it's a good idea to get a few of each to experi- ment with. You're going to have to come up with a way to control the signal on the direction pin but, since you're using a mechanical ane- mometer, there are several mechan- ical ways to get the job done. Get yourself a data book and do some brain stretching exercises at the test bench. The design problems you have in front of you are interesting ones and you should have a good time working out the right solution. /to 1 I r i t t I I i i D*rA A/PPL.^ MAX/ £>ATX £>A7?i A CLOCK ao« 41 /M Z^*5 C J3 X X -L JL 1 1 1 */£*- - - -t/#i (J3) 1 OUTPUT Li'/)— £X4TA s ■ 4 2S- — —i 3>- -tVl isi -4 Vl -4 7* t Y Y Y Y Y <*s JF/VA3LM. UP &r FIG. 1— THE 74190 CAN COUNT both up and down. The count direction is determined by putting either a low or a high on pin 5. A low will make the 74190 count up and a high will make it count down. FLYBACK SQUEAL I'm just getting started in electronics and I'm having trouble with a minor repair problem. The flyback trans- former in a TV always gives off an annoying squeal and I need some way to eliminate the noise or at least drop it to a more tolerable level. I don't have access to a lot of parts, and money is also a problem. Is there anything at all you can suggest 4 ? — L. Leduc, Ab- botsford, Canada Before we get started, let me tell you that, as far as I'm concerned, transformer squeal is one of the world's most annoying sounds. The only absolutely sure way to solve the problem is to replace the transformer. There's no way to take the old one apart. Every time I've tried to quiet a transformer without actu- ally changing it. I've only managed to make the sound go away for a short while. It always comes back. If there's no way you can replace the transformer, there are some other things you can do. I've done all of them at one time or another. Before you even think of doing any- thing to the transformer, pull the pug and properly discharge all capacitors to ground. And don't forget that eten wood can serve as a conductor for high voltages. That's a long wayj of saying that you can still get a napty continued on page 76 FLYBACK FIG. 2— TYPICAL FLYBACK transformer. You can try to eliminate the squealing noise, or at least cut it down a bit, by covering the transformer with RTV high- voltage putty or hot-melt glue. 12 LETTERS Write to Letters, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735 AMIGA AMIGO I could not help but feel a bit disap- pointed when I read Computer Con- nections in the January issue of Radio-Electronics. The author, Jeff Holtzman, speculates on the fu- ture of personal computers, predict- ing: CD a (preemptive) multitasking operating system; (2) an NTSC-com- patible video system; I/O sub- systems based on coprocessors; a graphical operating environment (with command-line mode for power users); and multimedia. Gee! That's funny! The Amiga's been doing ail that for five years! You mean,,. MS-DOS machines might have all that in the future! Wow, that's great! Then they'll only be fen years behind! Perhaps the column's name should be changed to "MS-DOS Connec- tions." The current title is misleading, because a reader might mistakenly think that the column provides an un- biased look at computer technology. Of course, in the October 1990 issue of Radio-Electronics, Mr. Holtzman calls himself a "PC chau- vinist." Oh, I see — that makes it OK to ignore the rest of the computer world! What I'd love to see is more Amiga coverage, Mr. Holtzman may be a PC chauvinist, but I'm a hot-blooded Amiga evangelist from the bowels of Hell. (Amiga — it's not just a comput- er, it's a religion!) He could at least mention my favor- ite machine, couldn't he? Surely no- body could have such a severe case of tunnel vision. But, alas, this letter is undoubtedly in vain. Nobody pays attention to us Amiga users... but thanks for reading this far! By the way my original letter was typeset blazing ly fast on a bottom-of- the-line Amiga 500, with AmigaT E X, of course. You know what they say — "The best way to accelerate an MS- DOS machine is at 32 m/s 2 " (Larry Phillips). RAYMOND CHENG Mississauga. Ontario, Canada Jeff Holtzman s response appears in this month's Computer Connec- tions. — Editor. MAC-HACK ATTACK Thank you for the information on hacking a Macintosh ("Build Your Own Macintosh-Compatible Com- puter." Radio-Electronics, Janu- ary 1990). I've been doing that kind of idiocy for a while, but believe me, it's not worth it. Add it up: Clone case $ 90,00 Fujitsu 800K floppy drive ... 104.00 Mouse (Samurai) 50.00 Monitor 50.00 Video/sync processor ..... 59.00 PUT THE PC10 EV YOUR PC FOR MORE COUNTER POWER OPTOELECTRONICS does it again - phenomenal power, performance and price. This is what sets our PC Based Universal Counter apart from any other counter available on the market today... • Instant Direct Tune - Set a communications receiver such as ICOM R7000 to frequency detected by counter. Patent pending. • Data logging and data (tie creation to keep records or measure frequency drift. • Men u select ion for Un us includes CPM/RPM , Hz. KHz. MHz. GHz, Sec. mS. uS and nS, • Software limebase calibration of I ppm TCXO timebase. Model PC 10 Universal Counter Timer Board for the PC. Introductory Price $3 '39, The PC 10 has mt hoard 50 ohm RF input i with amplifiers and presenters to operate as a stand alone I MHz tti 24GHz RF counter. TFL level input signals can be eimnerletl directly In the miniature 25 pin D connector on the mounting bracket. For low frequency, high impedance inputs, the Model 'API OH companion amplifier must be used. Model A ft 01 1 Dual High Impedance Amplifier Head L' nit t not shown). Introductory Price $299. The API0H is the companion head unit that supports ail PC10 Universal Counter functions from 10Hz to 100MHz with I megohm inputs. Input attenuators, tow pass fitters and trigger levels ace software selectable. Optiom: TCXO 10 Precision Temperature Compensated time Base $195. ± 0.2ppm 20 9 -40°C. I ppm - year tiding. • Windows 3,0 operating environment with fully developed operating and signal conditioning controls accessible through pull down menus. In addition to these unique features, PC 10 is a down right high performance counter... • 10 digit 10Hz to 2.4GHz. frequency range. ■ Measurement Period (Gate Ti me) eontinuousl y variable from 1 milli-sccond to 28 seconds. ■ Reciprocal Counting for high resolution measurement. • Input sensitivity is less than lOmV from 10Hz to over 1.6GHz. • Direct count frequencies over 200MHz with 1Hz resolution in 1 sec. VI IVbU.\.l I1WI1I\J Toll Free Order Line: 1-800-327-5912 FL(305)771-2050 * FAX(305)771-2052 5821 NE 14[h Avenue • Fort Lauderdale, Florida 33334 > TJ 3D 13 CIRCLE 183 ON FREE INFORMATION CARD o z o QC I- o LU O D < Assorted cables 30.00 Fan 8.00 Memory/SCSI board 150.00 New ROM's 100.00 Motherboard 50.00 Used keyboard 50.00 Power supply 13.00 AC filter 3.00 Power cord 1 .00 Battery 4.50 2 Meg RAM 80.00 Your time (10 hours at least) 250.00 TOTAL $1092.50 You might as well go out and buy a packaged Mac from a dealer, be- cause the above expenditures give you a bare-bones 8-MHz unit with a dinky screen and no hard disk! ALEX FUNK Durham, NC MORE ON MACINTOSH BUILDING I read with interest the article "Build A Macintosh-Compatible Computer" (Radio-Electronics. January 19911 Having purchased a Mac 128K in 1984 and upgrading the 128K motherboard (I'm still using it) to its current 2MB RAM, 128K ROM, and SCSI drives, I noticed a few critical points that were over- looked. I hope this letter will help clear up some issues that could cause problems for your readers. First, not every Mac is compatible with all software! Software written for the Mac II (68020 CPU) will not run on a Mac 128K, 51 2K, Plus, etc. There are a lot of programs that are written for System 6.0.x and these programs will not run on a Mac with the older 64K ROM. It is very difficult to find any software that will run on a 128K Mac today! You really must have the 128K ROM and 512K of RAM to use most Mac software. Second, there is a significant dif- ference between a 128K and 51 2K motherboards that have the 128K ROM's added along with more RAM and the Mac Plus motherboard. Those early motherboards had 20 bytes of Parameter RAM (battery backed). From the Mac Plus on, Ap- ple used 256 bytes of parameter RAM called XPRAM. Under System 6.0.x. the sound and Map Control Panel programs will not work unless you have the 256 bytes of XPRAM. The term "512KE" is often used to identify 51 2K. 64K ROM mother- boards that have been upgraded with 128K ROM, which is not correct. Ap- ple issued 512KE motherboards that had 128K ROM and 256 bytes of pa- rameter RAM, and those are the true "512KE" motherboards. I have found a simple solution to the XPRAM problem. My mother- board has only 20 bytes of parameter RAM but I am using a System 6.0.x with no problems. I am using Scott Armitage's XPRAM INIT software that uses disk space to replace XPRAM memory. Best of all, the soft- ware is free (you can download it from GEnie) and it works great! Finally on page 36 of the article it said that with 64K ROM you can use only 400K floppy drives, yet the parts list on page 32 states that you can use an 800K floppy with a 128K or a 51 2K motherboard. That is con- fusing, but there is a solution. You can use an 800K floppy-disk drive with a motherboard that has 64 K ROM only if you have Apple's Hard Drive 20 system file in the system folder That file was intended for Apple's original hard drive that plugged into the flop- py-disk-drive port and worked with the 51 2K machines. It also lets you use 800K floppies. The file is avail- able on GEnie. In case your readers don't have ac- cess to GEnie, for$5 and a formatted blank disk, I will send them the XPRAM and Hard Drive 20 files ($7 without a disk). (No phone calls after 9:30 PM CST. please.) There are a number of vendors out there with products for making your own Macintosh and upgrading older 128K and 512K motherboards that were omitted from your article. Less Hall (P.O. Box 5732, Raleigh, NC 27650) supplies Macintosh parts and information; Atlanta Technical Spe- cialists (3550 Clarkston Ind. Blvd., Suite F, Clarkston. GA 30021) sells cases, video cards, and kits; mother- board upgrades, SIMMS and SCSI, can be obtained from both Computer Care (Ford Center, Suite 1180, 420 North Fifth Street, Minneapolis, MN 55401) and Newbridge Micro- systems, 603 March Rd., Kanata, Ontario, Canada K2K 2M5): Soft So- lutions (907 River Road, Suite #98, Eugene, OR 97404) provides Macin- tosh parts and repairs; and Maya Computer (1-800-541-2318) offers Macintosh motherboards and all kinds of parts. ANTHONY J. ORESTEEN 452 Orion Road Batavia, IL 60510 (708) 879-5608 A RAVE REVIEW Just a brief note to let you know that Robert W. Ramirez's article, "Putting a New Scope to Work" (Ra- dio-Electronics, January 1991), was one of the best I have ever read. It was explicit and well planned, and written in clear and concise English. Thanks for a great article. SIDNEY GOLDHER San Leandro, CA FAX-MATE FIX-UP It has been brought to our attention that the "Fax- Mate" project (Radio- Electronics, October 1990) has an unwanted switching problem to the fax mode for some speech situa- tions. A closer study of the sche- matics showed that the Silicon Systems' DTMF decoder (IC2, SSI 204) is used incorrectly. Please ad- vise your readers of the correct im- plementation of the Silicon Systems' DTMF decoder IC. As reflected in the device's data sheet, the detected DTMF digit (pins 14, 13, 1, and 2) are guaranteed valid when the Data Valid (pin 12) is high. The author of the project has not used the DV pin. One way to correct the problem is to use a 3-input and gate C74LS11) instead of IC3-a and connect the DV pin to it. Another problem with the circuit is a phenomenon called "talk off," which is defined as detection of the DTMF tone in the presence of speech. As the human voice does include the frequencies of DTMF tones, a false detection is inevitable. One method to prevent this is to use two DTMF tone sequences instead of one. For instance, a two-digit code of "1" would reduce the false detec- tion problems. REN A MOATTAR Senior Applications Engineer Silicon Systems Inc. Tustin, CA LCD MODULE UPDATE I enjoyed very much the articles on LCD modules that appeared in the June and July 1990 issues of Radio- Electronics. I can find fault with only one aspect, which I have also seen perpetuated elsewhere. The problem is with the idea of using fixed delays after each operation on the LCD. The idea of performing an opera- tion on a device, then waiting for a fixed delay in software for the device 14 Cable TV Descrambler Article Parts We stock the exact Parts for several articles published in Radio-Electronics magazine on building your own Cable TV Descrambler. February 1984 SB-3 Type 701 Parts Pkg. ....$19.00 Includes all original parts. 702 PC Board .7.95 Original 3X4 etched, drilled and Silk-Screen pc board: — 704 AC Adaptor.. ...7.95 12 to 18 Volt DC @ 200ma. 701, 702 & 704.. ...29. 00 All three for special saving. February 1987 Tri-Mode 301 Parts Pkg 29.00 Includes all original parts. 302 PC Board 7.95 Original 5X8 etched, drilled and Si Ik- Screen pc board. 304 AC Adaptor 7.95 12 to 1 8 Volt DC @ 200ma. 301, 302 & 304.. ...39.00 Ail three for special savings. Tri-Mode Tutorial.. 7. 95 26 pages of in-depth info. May 1990 Universal 901 Parts Pkg $49.00 Includes all 902 PC Board. 9.95 Improved 4X7 etched, drilled and Silk-Screened pc board. 904 AC Adaptor 8.95 12 to 18 Volts AC @ 350ma. 901, 902 & 904 59.00 All three for special savings. Snooper Stopper.. .$39. 00 Prevent Descrambler detection with snooper stopper/data blocker and protect your privacy. Includes free article on Cable Snooping. Macrovision Kit. ..$29.00 Macrovision now you see it, now you don't with our macro-scrubber kit. Originally Published in Radio-Electronics . Signal Eliminator (tunable notch filters) ....$29.95 Model number & channel; #713 (channel 7 to 13) #23 (channel 2 & 3) #1417 (channel 14 to 17) #46FM (channel 4 to 6 & FM) #1822 (channel 7 8 to 22) 1 remote replaces 3... The MAC 20 wireless remotes replaces any three combinations; TV, VCR, Cable Converter, Stereo, CD or other entertainment system. MAC 20..... ..$59.95 A VCR in every room.. with the first FCC approved wireless home broadcast system. 120 ft. range. VC2000 ...$99.95 70 Channel Cable TV Converter .......$89.95 * 6 Function Infra-Red remote. * Compatible with all External Descram biers. * Fine Tuning. * Channel 3 or 4 switchable output. * Memory & Recall. * STD, HRC & IRC compatible. CALL TOLL FREE 1-800-332-3557 Outside USA Call 1-508-699-6935 Visa, MasterCard and COD. Add $4.00 S&H, $6.50 Outside USA. D & D Electronics, Inc. PO Box 3310, N. Attleboro, Ma. 02761 VISA MC > ■o CIRCLE 185 ON FREE INFORMATION CARD 15 o o DC h- o UJ _i LU o < rr 16 LISTING 1 DISLET BCLR 0. PORTB ENABLE OFF BSET 1, PORTB SET RAW TO READ BCLR 2, PORTB SETRS = BSET 0, PORTB ENABLE ON BRSET 7, PORTA, 3ISLET BUSY7-LOOP BCLR 0, PORTB ENABLE OFF BCLR 1, PORTB SET RAW TO WRITE BSET 2, PORTB SET RS = 1 STA PORTA OUTPUT CHAR LDA #$FF REVERSE DATA LINES STA DORA (DATA DIRECTION REGISTER FOR PORTA) BSET 0, PORTB ENABLE ON BCLR 0, PORTB ENABLE OFF CLR DDRA DISABLE DATA LINES RTS to finish, is always a very poor one. First of all, there is always some pro- cessing to do before you use the de- vice again, and possibly the device wiil have finished by the time you get back to it, thereby making the delay unnecessary. Furthermore, the exact question of time delays gets more complicated. Are the figures on the specifications sheet average times or worst-case times? What if the device gets replaced with a slower one, or the clock rate of the processor gets changed. What if, as in the LCD, the device takes a long time to power up? The best solution, specifically for the LCD, is to use the busy flag pro- vided to you by reading the MSB of the data with RS = 0. That can always be read in the basic cycle time of the LCD (approximately 1 u^s). Depending on your hardware, that might require some changes to make the data bus bidirectional. The software would, before each LCD operation, check the busy flag and loop until it was clear, then go ahead with the operation. That would For quality, cost-effective test instruments. B&K-PRECISION is your one-stop source! Our line includes digital and analog oscilloscopes, multi- meters, frequency counters, power supplies, generators, digital and IC testers, semi- conductor and other component testers. Thev all offer famous B&K-PRECISION quality, plus immediate delivery from a distributor near you. FREE BUYING GUIDE For a 68-page guide with detailed specifications on all our products, contact your local distributor or: 4J MA \TEC IBTTERNATIONAL CORP. Domestic and International Sales f>470 \V. Cortland St., Chicago, IL 6063S 31&88S-1448 • [-'AX: 312-794-9740 Canadian Sales, Atlas Klcctronics, Ontario take care of the power-up delay and the variable delays associated with different operations. If you wanted to be extra careful, you could make the software timeout after 100 ms, so that the processor would not "hang" if the LCD was disconnected or broken. Listing 1 (and, similarly, Listing 2) of the June article could be rewritten as shown here: Good luck! RUSS HOBBS Worcester. MA THEFT OF CABLE SERVICES In the July 1990 issue of Radio- Electronics, in his Drawing Board column, Robert Grossblatt defended the theft of cable TV pay services on philosophical grounds that are appar- ently shared by those who write to your Letters column. That philosophy is also shared by the "phone phre- aks" and power-meter bypassers who have spent time in jail for their beliefs. Those people are no less thieves than those who drive off from a gas station without paying. ft is fortunate that the majority of the population does not subscribe to that philosophy. The honest majority must pay higher prices for their goods and services to subsidize those who choose not to pay. If every- one stole all services, the services would cease to exist. I believe that a magazine that pub- lishes material describing methods and equipment clearly intended to defraud legitimate businesses is as guilty as the authors who write and the readers who use that material. If a magazine must resort to that sort of sensationalism to boost readership, perhaps another line of business is indicated. JIM SPENCER Fern Park, FL TELEPHONE LINE CONTROLLER I've received so many questions concerning my article "Telephone Line Controller" (Radio-Elec- tronics. September 1990) that I've put together a "Question-and-An- swer" flyer. It answers the most com- monly asked questions, and is available at no charge by writing to AC&C. 717 East Jericho Turnpike, Suite 101, Huntington Station, NY 11746. MORDECHAI SAAD R-E CIRCLE 77 ON FREE INFORMATION CARD Build your own laser printer at a fraction of the cost of those expensive store-bought units. PAUL RENTON A LASER PRINTER CAN REALLY ADD that extra touch to your printouts. The superb graphics resolution gives your printouts a professional look, and the fast text output (8 pages per minute) can really speed up your print- ing. Although laser-printer prices have dropped drastically in the last few years, they are still a little too expensive for the aver- age person. However, you can now build your own laser printer at home and save thousands of dollars! How it works Laser printers are essentially souped-up copy machines. They FIG. 1— THE MONITOR CAN BE SECURED to the copier surface using C clamps, super- glue, or even large rubber bands. The exact method you use depends on your particular copier monitor combination. use a photosensitive drum which is exposed to a laser beam. The laser beam can be turned on and off while spinning mirrors sweep the laser beam across the drum selectively discharging it. Toner is transferred to the drum in the charged places and then onto pa- per to produce the final image. Since a copy machine already has the paper feed, the photosen- con tinned on page 84 Add comfort, convenience, fun to your home with these ^nJnnovative electronics. Hundreds of easy innovations. Your home will do more for you with Heath products. Simple to install. Affordable. Guaranteed. Play a tape on the living room VCR and watch it on your bedroom TV. Turn on and adjust your TV, VCR, music system, lamps, fans and more with just one remote control. Plug in an extra phone jack without messy cutting and drilling. Get a complete home status report via phone from anywhere in the world. (If the electricity goes off, this electronic "house sitter" calls you.) Automatically water your lawn at a fraction of the cost of a built-in system. Call home and turn on your lights, appliances ... even a window air conditioner. Affordable security for your home or car, Protect your home or car with a professional-quality security system for as little as $100. Program lights to go on or off, so your home looks lived-in when you're away. Get your FREE CATALOG. Heath's new Home Automation catalog features the latest in home control. For over 100 ways to make your home comfortable and convenient, call 1-800-44-HEATH or send the coupon below. HOAE , Automation / \ EV HEATH Never again return to a dark house. Motion sensor lighting rums on your outdoor lights as soon as you approach. 100% satisfaction ... the Heath guarantee for over 40 years. Try any Heath product at no risk. If you aren't completely satisfied, simply return the item within six months for credit or full refund. CIRCLE 86 ON FREE INFORMATION CARD Heath Benton Harbor, Michigan Please send me the NEW Home Automation catalog. Name Address Apt. . City_ State . Zip. Maii to Heath Company, Dept. 020-040, Benton Haibor, MI 49022 > 13 17 EQUIPMENT REPORTS Hewlett Packard 54601 A Portable Digital Oscilloscope As weary as test-equipment manufacturers are of battling the competetition — which comes from both on- and off-shore — they continue to wage a valiant fight. And we continue to be the benefici- aries. The latest examples of the trend are two new scopes from Hewlett Packard (1900 Garden of the Gods Road, Colorado Springs. CO 80907-3483): the two-channel HP 54600 and its 4-channel sister, the 54601A. Both of the scopes (we examined the 54601 A) feature a 100-MHz bandwidth with a sampling rate of 20 megasamples per second (8- bit stor- age). Vertical sensitivities range from 2 mV/div to 5 V/div (on the first two channels; the third and fourth offer sensitivities of 0,1 and 0.5 V/div). The timebase can range from 2 ns/div-5 s/div. Because they are digital, they offer a number of other features that are inherent benefits of DSO's. Since these scopes are targeted at techni- cians and engineers who may never have purchased a digital scope, we'll review some of those benefits. Why digital? The first benefit, of course, is the ability to store waveforms. The 54601A has two trace memories, which can store two complete sets of waveforms; that is, each set can con- tain signals from all four channels. Unlike analog storage scopes, the signals can be retained indefinitely in memory, so measurements made in the field can be viewed later. Traces on digital scopes can be easier to view and thus they can be more informative. Low-frequency sig- nals will remain steady and bright in- stead of flashing. Signals with low repetition rates will be displayed at the same brightness as any other sig- nal. Transients can be captured with- out the need for a scope camera, and signals that occur before a trigger can be viewed. Digital oscilloscopes have the rep- utation of being difficult for an analog- scope user to adjust to. However, that's not the case here. The front panel offers a clean layout that is easy to use even for those used to analog scopes. The only main-panel controls that aren't normally found on analog scopes are the run. stop, autostore and erase buttons for trace storage, and the trace and setup store/recall buttons. The rest of the controls are equally scarce — or so they seem. The main panel can be kept so open and easy to use because most functions are controlled by six "soft key" pushbut- tons below the CRT. Those keys take on the functions as displayed above the keys. For example, when the channel i button is pressed on the main panel, the soft keys below the CRT let you select the input coupling, signal inversion, etc. Using the scope A push of a single button can set the scope up even if you don't know what signal you are expecting to view. Alternatively, if you routinely perform certain measurements again and again, you can store up to sixteen complete front-panel setups in mem- ory. Interpreting the signals shown on the CRT can be extremely easy. The voltage, (peak-to-peak, average, and rms value), frequency, period, and duty cycle of the signals on each channel can be displayed automat- ically. On-screen cursors can be moved manually to make voltage and time measurements. The display-update time is quite fast, and gives the scope the feel that you'd expect from an analog scope One of the reasons for that is that Hewlett Packard uses custom ac- quisition-processor and display-pro- cessor IC's that don't rely on the scope's CPU to handle data acquisi- tion or display management. Do all these features make the scope easier to use? We have to an- swer, "Yes, definitely." Because we were examining an early prototype (the scopes won't be available for al- most two months as we write this report, but will be available when you read it) we didn't have an opportunity to examine an operating manual — not even a preliminary draft. Nonethe- less, we encountered no problems that we weren't able to answer with a bit of experimentation. Optional interfaces (which we didn't examine) can increase the ver- satility of the 54601 A, Serial RS-232, parallel, and HP-IB (IEEE-488) inter- faces can provide hardcopy output to plotters and printers. Optional soft- ware allows you to easily convert waveforms into popular MS-DOS graphics and data formats. In addi- tion, the scope is fully programmable via the serial and HP-IB interfaces. The HP 54600A and 54601A 100- MHz digital oscilloscopes aren't the lowest priced or the most fully fea- tured 100-MHz DSO's on the market. However, with prices of $2395 and $2895. they are a bargain that will be hard to resist for engineers and tech- nicians involved in everything from R&D to field service. R-E Start a money-making career in video/audio servicing! Only NRI gets you started fast with real-world training designed around state-of-the-art equipment you keep! NRI's newly expanded training cov- ers all the latest advances in home entertainment electronics, then takes you inside today's high-tech equip- ment as you learn to troubleshoot, diagnose, and service the complete home entertainment system included in your course: 1 3" color TV, pro- grammable VCR, and integrated audio rack system. Only NRI makes it so easy to start a new career, earn part-time income, even start a video/audio servicing business of your own! Billions of dollars of video/audio equipment means big opportunity for you There's never been a better time to get involved in home entertainment electron- ics. Experts predict that consumers of vicleo/audio equipment will spend over S26 billion by 1995 as product manufacturers race to fill the demand for increasingly sophisticated technology. This explosive acceleration of new product innovation means new opportu- nities for you in video/audio servicing. And NRI prepares you to take advantage of those opportunities by giving you the skills to troubleshoot and service a full range of TV, video, and audio equip- ment. The most advanced, most complete video/audio training ever offered! You start with lessons thai give, you a strong foundation in electronics funda- mentals, mastering the basic circuits and components at the heart of today's video/audio equipment. Then you build on that foundation as you explore the high technology of digi- tal controls, CDs and digital audio tape players, advanced TV systems, cable TV, VCRs and camcorders, even microprocessors. Best of all, you're pre- pared for the technology of today and tomorrow with hands-on train- ing designed to give you invalu- able practical experience. State-of-the-art equipment included in your training makes theory come to life Only NRI gives you so much real-world equipment ... all yours to train with and keep! Get hands-on experience as you work with a complete, high-tech home entertainment system: a 13'' color TV with remote, a programmable VCR. anil an integrated remote-controlled audio system including AM/ KM tuner, 100 watt amplifier, CD player, dual cassette play- er, turntable, speakers, anil audio rack cabinet. Theory conies to life as you learn to perform component-level diagnosis and service on advanced technology audio equipment ... conduct in-set demonstca- tiims of TV circuits and components ... and discover first-band how to maintain and service today's commercial VCRs. Plus, NRI custom-produced videos show you in close-up detail how to test, troubleshoot, and service TVs and VCRs like a pro. No experience necessary ... NRI builds it in You need no previous experience in elec- tronics lo succeed with NRI. Step by step, you accumulate the knowledge and practi- cal experience that will make you unique- ly qualified for today's opportunities in home entertainment electronics. You learn at your own pace and on your own time. And all throughout your training, you have the full support of your personal NRI instructor and the entire NRI technical staff. FREE catalog tells more If the coupon is missing, write to NRI Schools, McGraw-Hill Continuing Education Center, 4401 Connecticut Avenue, N\V. Washington, DC 20008. SEND TODAY FOR FREE NRI CATALOG 4401 Hands-on training with this incredi- ble array of home entertainment equipment gives you the skills you need for success. Schools raw- Hill Continuing Education Center Connecticut Avenue, NW, Washington, DC 20008 H Check, one FREE cutalo^ only D T V/Y ide o/A u xl i o Sc r vi c nip P Microcomputer Servicing □ Computet Programming □ Telecommunications DPC Systems Analysis □ PC Software Engineering Using C Fur Career Opportunities approved umlerGl Bill G ehrek fur tin mils □Desktop Publishing & Design □ Electronic Music Technology n Word Processing Home Business □ Automotive Servicing □ Basic Electronics □ Bookkeeping & Accounting Name (PI Rasp pi-int) Agr Address City Stale Zip 3 041 > 21 U5 Q z □ X I— '3 JJ _J JJ ■ □ < MONOSCOPE/TV PAT- TERN GENERATOR. De- signed for testing the higher-resolution large- screen television sets, Leader Instruments' model 435B generates mono- scope patterns with a reso- lution of 1000 lines, as well as color bars, Crosshatch, pulse and bar, and character patterns. Color bars can be superimposed on the monoscope pattern to check resolution and color simultaneously. The instrument includes RF out for evaluating TV and VCR circuits. Frequency re- sponse can be evaluated with the line-sweep signal, and transient response can be checked with the win- dow pattern. A five-step staircase is provided for lu- - LEADER mtc teit mmi OMUutftM 435 ■*&3fsra L " sis— ' js. *ar ■ ■»«- —ag llllllliii ! * V — a m CIRCLE 16 ON FREE INFORMATION CARD minance linearity, and a 1 .5- kHz signal is provided for evaluation of audio. The model 435B pattern gener- ator offers a total of 21 pat- terns, including two types of color bars, five rasters, line sweep, and five-step staircase. It can evaluate high-voltage stability and character reproduction as well as linearity. The model 435B TV pat- tern generator costs $3.100.00— Leader In- struments Corpora- tion. 380 Oser Avenue, Hauppauge,NY11788;Tel: 1-800-645-5104 (in NY, 516-231-6900). FOUR-IN-ONE INSTRU- MENT. Combining a 100-MHz frequency counter, a 2-MHz function generator, an auto- ranging digital multimeter, and a 0-50VDC/0-2A power sup- ply in one compact case. Bel MERIT'S MT-100 provides a cost-effective way to acquire a comprehensive test laborato- ry lhat won't crowd a work- bench. The MT-100 is de- signed for use in education, production lines, hobby elec- tronics, inspection work, or design engineering. The MT-100 frequency counter/function generator/ DMM/power supply has a CIRCLE 17 ON FREE INFORMATION CARD suggested list price of $595 00 —Bel MERIT Cor- poration, 14775 Carmenita Road. Norwalk, CA 90650; Tel: 213-802-3666; Fax; 213-802-3298. DC/DC CONVERTER. With its wide input range of 20 to 72 volts DC. Calex's model 48S5.5000XW DC-to-DC converter eliminates the need for separate converters for dif- ferent voltage requirements within that range. The unit can be used for either 24-volt or 48-volt powered systems, and is designed for use in a wide variety of industrial control systems. The model 48S5.5000XW provides an output of 5 amps at 5 volts DC with an 80% effi- ciency, with switching tech- nology used to regulate the output voltage. Key specifica- tions are 0.05% line and load regulation; 10 mV peak-to- peak output noise; and -25 CIRCLE 18 ON FREE INFORMATION CARD to + 80°C operating tempera- ture range. The converter has input-to- output isolation of 500 volts. Internal transient suppressor devices guard the input and output against high-voltage spikes. Filters provide protec- tion against conducted noise from both the input and the output, the shielded case pro- vides RF1 protection, and the unit is also short-circuit pro- tected. The output voltage can be trimmed ±10% with a po- tentiometer, voltage source, or DAC. For remote battery or solar-powered applications, a logic-shutdown pin, which al- lows the unit to be toggled on and off to conserve energy, is especially convenient. The model 48S5.5000XW DC/DC converter has a list price of $160.00.— CALEX Mfg. Co., Inc.. 3355 Vin cent Road. Pleasant Hill. CA 94523; Tel: 800-542-3355: Fax: 514-932-6017. ESD-SAFE SMT VACUUM PICK-UP PENCIL. For safely handling static-sensitive sur- face-mount components, OK Industries' VP 150 Series vac- uum pick-up pencil is uniquely designed and manufactured using static-dissipative mate- rials. The tool allows manual- placement users to handle SMT IC's without worrying about static discharge. The VP-150 provides two user-selectable vacuum-deac- tivation modes. A two-posi- tion switch allows for both "continuous' vacuum opera- tion, in which vacuum deac- tivation is achieved when the user lifts his finger off the handpiece's bleed-hole, and "foot-pedal" operation, in which the vacuum is deacti- vated electrically by pressing a foot pedal. The vacuum pick- up pencil can be used with OK Industries' SMT-810 board holder and SMT-815 compo- nent carousel. The VP-150 vacuum pick-up pencil has a suggested list price of $176.00.— OK In- dustries. Inc.. 4 Executive Plaza. Yonkers, NY 10701 ; Tel: 914-969-6800. CIRCLE 19 ON FREE INFORMATION CARD 22 SELECT 5 BOOKS for only $ 4^ (values to $127.70) J " CNCHli^Mti '■ ELECTRONIC J -H'lXC) K* wvjvi CIRCUITS ' 10010P 519,95 Your most complete source for electronics books for over 25 years. 2B26P $16.95 3279 53G.9E Counts as :: |d| How to fl**d ■ Ivctranlc Circuit IP 3259 327.95 Counlt as 2 lOW-COST ELECTRONIC CIRCUITS 3107P 51 fl, 95 2B6SP SH.95 3219 S27.9S Counts is 2 3445 S21.95 2995 925.95 ' * ELECTRONIC CIRCUITS tM&UTtxil J ^/ V v ^ Q N/ V ^ V V ^ -' V s V V V ^ s/ 303 IP S 17.95 2BS0P 514.95 Brtsbtess E Matirs ■ 1 ■ fill lim«> 1 UK M 3267P S1S.9S 33« S25.9S Counls as 2 23D0P S16.SS 2613P S17.9S All books are hardcover unless number is followed by a "P" lor paperback. Membership Benefits • Big savings, in addition to this introductory offer, you keep saving substantially with msmbars' prices of up to 50% off the publishers' prices. * Bonus Books. Starting immediately, you will be eligible for our Bonus Book Plan, with savings of up to 80% off publishers' prices. • Club News Bulletins. 15 times per year you will receive the Book Club News, describ- ing all the current selections— mains, alternates, extras— plus bonus offers and special sales, with scores of titles to choose from. • Automatic Order. If you want the Main Selection, do nothing and it will be sent to you automatically. If you prefer another selection, or no book at all. simply Indicate your choice on the reply form provided. You will have at least 10 days to decide. As a member, you agree to purchase at least 3 books within the next 12 months and may resign at any time thereafter. • Ironclad No-Risk Guarantee. If not satisfied with your books, return them within 10 days without obligation! • Exceptional Quality. All books are qual- ity publishers' editions especially selected by our Editorial Board. Electrons BqqkClJb Blue Ridge Summit, PA 17294*0810 Please accept my membership in the Electronics Book Club and send the 5 volumes listed below, billing me £4.95. It not satisfied, I may return Ihe books within len days without obliga- tion and have my membership cancelled. I agree to purchase at least 3 books al regular Club prides- during- Ihe next 12 months and may resign anytime (hereafter. A shippjngThandling charge and sales tax will be added to all orders. 3138 S 6 0,00 Counts as 3 [alarms if 239GP S13.95 the __ GET EXAM BOOK 295QP $13.95 rtv: IF-..U ANTENNA IIIVSi r!.-k Solid-Slate I.I t H 1 Kl >\l! S mt.oin "j •ffl ■ ^1 :~Jr» 3270 S32.9S Counts a* 2 2325 325.95 Name . Address City _ State Zip Phone Valid r« new members only. Foreign applicants will feccivo special ordering ansirucijons. Canada must rernii »n U.S currency This order gubj&cl lo Beceplence Ijy ihe Efeccromcs Book Club RPIE491 ELECTRONICS FIX !T BOOK > -a 3Q I89TP $15.35 2B83P SI 7.95 (Publishers' Prices Shewn) -,1991 ELECTRONICS BOOK CLUB 23 to o LU _l LU 6 D < LX VOLT-OHM-AMMETER. A.W. Sperry's Digisnap DSA-7610A 3'/2 digit, snap- around volt-ohm-ammeter is designed to live up to heavy- duty use in portable electrical- service applications. The compact, battery-operated in- strument measures AC volt- age (0-500V), AC current (0-30QA), and resistance C0-2K ohms). It provides auto- ranging, an instant audible From expensive, complex hybrid devices. Its perfor- mance is achieved by laser- trimming high-stability, thin- film resistors to correct for CIRCLE 20 ON FREE INFORMATION CARD continuity buzzer, and an auto- matic power-off feature. Other features include safety-styled test leads, recessed safety- designed input jacks, current transformer jaws that open si- multaneously, electronic over- load protection, and a data- hold switch. One set of test leads, two batteries, and a car- rying case are included with the instrument. The Digisnap DSA-76WA volt-ohm-ammeter costs $119.95.— A.W. Sperry In- struments, Inc., 245 Mar- cus Boulevard. Hauppauge. NY 11788; Tel: 516-231-7050. PRECISION MONOLITHIC ±10V REFERENCE. Analog Device's AD688, claims to be the industry's first precision monolithic ±10V reference, has a maximum tracking error of 1.5 mV, initial error of 2.0 mV. and a temperature drift of only 1 .5 ppm/°C. The device's absolute accuracy perfor- mance matches that available CIRCLE 21 ON FREE INFORMATION CARD drift. Applications include robotic, avionic, and instru- mentation designs, as well as 12- to 16-bit data-acquisition systems. The AD688 offers 1 2-bit ab- solute accuracy without any user adjustments or trims. For extremely precise applica- tions, the reference can be calibrated using the "gain" and "balance adjust" pins. Force and sense connections (Kelvin connections) are used to correct for the effects of voltage drops in circuit wires by forcing the reference out- put of the device to a value that precisely compensates for the voltage error. The reference cell consists of an ion-implanted buried Zener diode and three low- drift amplifiers that facilitate Kelvin connections. It is pack- aged in a machine-insertable, 16-pin cerdip with three grades specified by accuracy and temperature range. The AD688AQ is specified over the -40 to + 85°C industrial temperature range and the AD688SQ over the - 55 to + 125°C range. Both of those precision references have an initial output error of ±5 mV and a tracking error of ± 3 mV. The AD688BQ is specified over the - 40 to 85°C temper- ature range with an initial error of ±2 mV and a ±1.5-mV tracking error. The AD688 ± 10V refer- ence is priced starting at $12.75 in hundreds. — -Ana- log Devices, Inc., Applica- tions Assistance, 181 Bal- lardvale Street, Wilmington, MA 01 887; Tel; 617-837-1428. DIGITAL MULTIMETER. Of fering high-performance and easy operation, Global Spe- cialties' model 735 SVa-digit LCD-readout multimeter with autoranging capability is suit- able for professionals, schools, and hobbyists. Its measurement functions in- clude DC and AC voltage. DC and AC current up to 10 amps, resistance, diode check, and continuity check. Advanced features include data hold, which provides hands-free op- eration by retaining the last measurement value even after the test probes have been re- moved from the circuit, and memory mode, which allows CIRCLE 22 ON FREE INFORMATION CARD deviations and relative mea- surements to be made by sub- tracting the latest measure- ment from the stored value. The model 735 DMM costs $59.95— Global Spe- cialties, 70 Fulton Terrace, New Haven, CT 06512; Tel: 1-800-572-1028. PORTABLE IBM PS/2. For those who require desktop power, storage, and expan- dability in a laptop computer, the IBM Personal System/2 model P75 486, based on Micro Channel architecture, features a 33-MHh i486 micro- processor and comes stan- dard with either a 160-MB or a 400-MB fixed-disk drive. The portable computer has a 10- inch gas plasma display and VGA resolution, 8 MB [expan- dable to 1 6 MB) of high-speed (70 ns) memory, and a full 1 01 - key PC keyboard. The P75 486's integrated design makes it easily expan- dable. It offers an external small computer system inter- face (SCSI) port and an exter- nal video port of IBM's extended graphics array (XGA) video subsystem, both integrated on the system CIRCLE 23 ON FREE INFORMATION CARD board. Users can connect to a variety of SCSI peripherals and support for 1024x768 resolution on an external monitor without using any of the system's two full-size (32- bit) and two half-size (16-bit) expansion slots. The system is supported by OS/2 Ex- tended and Standard Editions 1.2 and 1.3. DOS 3. 3 and high- er, and DOS with Microsoft Windows 3.0. Some of the available options include a molded-plastic travel case with wheels that fits under air- plane seats or in overhead lug- gage compartments. The P75 486 costs $ 1 5,990 for the 160-MB hard-drive ver- sion and $18,890 for the 400- MB version, — IBM Corpo- ration, US Marketing & Ser- vices, 1 1 33 Westchester Ave- nue. White Plains. NY 10604. THERMISTOR/COMPUTER INTERFACE MODULES. Of fering a combination of wide- range analog input-signal con- ditioning, analog-to-digital conversion, and on-off control features, DCH Corporation's D' J5 '/m52 modules make it easy to link 2252-ohm ther- mistors to any computer with a serial port. They communi- cate in ASCII over an RS-232C or RS-485 link. using an 8-bit CMOS micro- 24 computer to perform all seat- ing, linearization, and calibra- tion tasks. That eliminates the need for potentiometers, switches, or any kind of ad- justment hardware. The sin- gle-channel data-acquisition modules also eliminate multi- plexing problems, by putting the hardware at the input source. As many as 124 mod- ules can be strung on a single set of wires. The measurement tempera- ture range is to 100°C. mea- surement resolution is O.Q1°C or F, and accuracy is ±0.1°C (25° ambient). The conversion rate is 8/s, and input isolation is 500V rms. Communication features include channel ad- dress, 300 to38.4K baud rate, parity, line feed, byte-time de- lays, echo, and checksum. Communications setups are stored in nonvolatile memory to prevent accidental erasure. The thermistor/computer in- terface modules are packaged in 3. 6X2. 45x0. 85-inch CIRCLE 24 ON FREE INFORMATION CARD cases with captive hardware and a plug-in screw terminal connector. The D' 4S, /i4s2 thermistor/ computer interface modules cost $250.00 in single quan- tities. — DGH Corporation, P.O. Box 5638, Manchester. NH 03108; Tel: 603-622-0452; Fax: 603-622-0487. POWER SUPPLY. With two analog meters, the model 161 1 0— 50-volt. 2-amp DC power supply from B&K-Precision provides simultaneous monitoring of voltage and cur- rent output. For precise output settings, two current ranges are selectable, with coarse and fine voltage controls also provided. The compact bench-top in- strument has 0.01% regula- tion and less than 1-mV RMS ripple, and is conservatively rated for continuous operation and maximum power output without overheating. De- signed to withstand accidental abuse, the power supply is equipped with reverse -polarity CIRCLE 25 ON FREE INFORMATION CARD protection from an external DC source, overload protec- tion, thermal protection, short-circuit protection, and current limiting. The model W11 provides fully isolated positive and negative outputs, so either polarity can be floated or grounded. It offers both con- stant-voltage and constant- current operation, with auto- matic mode selection. In con- stant-voltage applications, a current limit can be preset. If variations in the load cause the current to reach the pres- ent value, the unit automat- ically switches to constant- current operation. Two 1611 units can be connected in par- allel to double the current out- put, or in series to double the voltage output. The model 1611 power sup- ply, that comes complete with hook-up leads, spare fuse, parts list, schematic diagram, and instruction manual, has a suggested retail price of $295 00— B&K-PRECI- SION, 6470 West Cortland Street. Chicago, ll_ 60635; Tel: 312-889-1448. R-E CABLE - TV SIGNAL REA4DVERS ■FOR ELIMINATION OF SEVERE INTERFERENCE ■FOR -CENSORING' OF ADULT BROADCASTS ,«,] K ■ ATTENUATION - 45 dB TYPICAL ■ BA»,n WIDTH - 4 MHz AT 5 dB POINTS ■ INSERTION LOSS - 2 dB MODEL for GH4MNEL5 PASSEANO prke SMIPPIHS 23H S4W! MHz 2.3 |or 6 ma1#r turn) 50-350 MHl ',":", NO SHIPPING or C.O.Q CHARGES 46 FM 86-10S MHz <56lonnvFMS 50-300 Mi- 1 130 1417 130-144 MHz UtK 15[B1 16(C) 17) D| 50. 4D0 Mhti (30 ISM 141 174 MHl urEl '9(f) 20(G) 2i|h i 22 l"i 50-400 MHz 130 713 174-216 MHz 7.S.$.10.11.12.13 50-400 MHz S30 3 for $75 - 10 for $200 - mix or match CALL TOLL FREE FOR C.O.D OR SEND CKECKTO ORDER FASTDELIVERY 30 D A Y M ON E Y BACK G U AR ANTE E [3 F ILTE R L IM IT) Star Circuits P. O, Box 94917 Las Vegas, NV 89193-4917 1-800-433-6319 CRAMOUN DeOxidizer IMPROVES CONDUCTIVITY DEOXIDIZES • CLEANS • PRESERVES • LUBRICATES Foi Alt Metals, including Gold! CRAMOUN 5 DeOxidizer improves conductivity by dis- solving oxides Ihot form or meiai connector nnd con- tort surfaces, eliminating unwonted resistance Ihot impedes eleclrical performance. CRAMOUN® is on active ingredient thai does not rely on solvent; for performance. Due to ihe excel- lent migration properties, CRAMOUN 3 cools the entire metal surface nnd ptoterts it from future oxidation. CRAMOUN'J' continues to be tlie most effective end economical product for improving ond maintaining electrical component reliability. FOR MANUFACTURE, MAIMCNANCC AND SERVICE OF: • Smithes I Belays ■ Coble Connectors 8 Adopters • Edge Connectors • Terminal Strips • Plugs & Sockets • Gold Floted Connectors • Potentiometers • Battery Contacts USED BY THOSE WHO DEMAND THE BEST; • Sell & Howell • Capilol Records • Dolby Laboro lories * Hewlett Pockord » John Fluke Mfg. • Mcintosh Labs • MCI (Sony) • Motorola • NASA • Notomichi * RCA • Smithcraft • ond Mony More. PO.BoxJ 0xid izer WffS,ftH J^r*. c:r/.k,::^: I LABORATORIES, INC. 'Envtronmentalfy Conscious-' Escc«tdo,CAv203Mi79 (619)743-7143 FAX;1619) 743-2140 CIRCLE 50 ON FREE INFORMATION CARD > 3 25 NEW LIT Use The Free Information Card for fast response. o o £ h- o 111 _l Lit 6 Q < GREAT RADIO READS CATALOG #5; from Tiare Publications, P.O. Box 493, Lake Geneva, Wl 53147; Tel: 414-248-4845; $1.00. Expanded to 20 pages, this catalog features a wide variety of books and other items designed to help you get more out of your radio hobby — whether you're into SWL. ham, scanning, m&£® EflffiB© EEAiRS Ffer Hrw TLbt fjeit% i "** >'lu hfB 1\Mtf 1 . -.1, ^-1" L^l t-*l,, TV. VdlU) I 1 lw '" I EUViSlrt^L***** " J*" ! 1—' rn *« «» 1 1.1. hH M UHT UJ^ « - Hit ... - ■ "■ . CIRCLE 27 ON FREE INFORMATION CARD or CB's. New books in- clude Coast Guard Radio and Radio Communica- tions Software Directory. Besides books, the catalog offers items such as SWL forms, software, globes and maps, and even a "Ra- dio for Peace" T-shirt. HDTV: ADVANCED TELEVISION FOR THE 1990's; by K. Blair Ben- son and Donald G. Fink. McGraw-Hill Book Com- pany, 11 West 19th Street, New York, NY 10011; Tel. 1-800-2- MCGRAW; $39.95 (hard- cover). The advent of high-defi- nition television has cre- ated dozens of questions for which America's high- technology industries must find reliable, realistic an- swers. This book strives to answer such questions as: Which of the HDTV sys- tems now being developed will become the standard? How can broadcasters take part in HDTV? Will con- sumers be willing to pay the price for improved per- formance? What effect will recent FCC rulings have on HDTV development? The book features tech- nical overviews of the vari- ous competing HDTV and ATV (advanced TV) sys- tems currently under de- velopment — including a de- tailed analysis of Zenith's spectrum-compatible sys- tem — and carefully as- sesses the strengths and weaknesses of each. It ex- amines all aspects of the 1125-line system, from its equipment and color- imetric standards, to trans- mission and modulation considerations, and meth- ods for coping with noise l^BbAII^BENSQNl [DONALD G. FiNKl CIRCLE 28 ON FREE INFORMATION CARD and other problems. The book explores a wide range of topics, including signal compression, digitization, fiber-optical tests, and tape recording. An in-depth dis- cussion of pertinent man- agement issues that must be resolved is included. The book also provides a practical look at tech- niques for simulcasting, re- ceiver design specifica- tions, the distribution and transmission of the picture signal, and the impact of HDTV technology on pro- gram production. TMT-1 TRANSMISSION MEDIUM TESTER; from Beckman Industrial, 3883 Ruffin Road, San Diego, CA 92123-1898; Tel: 619-495-3200; Fax: 619-268-0172; free. McGrowilill W-l Transit Milium u-itr I Ml "l InsJMttiv-iiui CIRCLE 29 ON FREE INFORMATION CARD This six-page, full-color brochure describes Beck- man's TMT-1 transmission medium tester, an instru- ment used in local area net- works (LAN's) certifica- tion. The TMT-1 is a lightweight portable instru- ment designed to verify the capability of installed LAN's to conduct high-re- liability information traffic. The brochure explains the series of tests performed by the TMT-1 either auto- matically or under manual control. The literature is free from Beckman upon request. Digital Video? second carrion ■■■*> CIRCLE 30 ON FREE INFORMATION CARD DIGITAL VIDEO IN THE PC ENVIRONMENT: Second Edition; by Arch C. Luther. McGraw-Hill Book Company, 11 West 19th Street, New York, NY 10011; Tel. 1-800-2- MCGRAW; $29.95. Digital Video Interactive, or DVI. technology is an exciting new field that brings together audio, vid- eo, and personal comput- ers to create a system with vast storage capacity that is user friendly and can de- liver multimedia presenta- tions. This book is written for those who are inter- ested in learning about DVI and the special skills re- quired for practical applica- tions of the technology. The second edition has been fully revised and up- dated, and includes a thor- ough examination of the i750, an inexpensive DVI chip from Intel that prom- ises to make DVI tech- nology economically feasi- ble for a wide range of PC applications. Also covered are the latest writable and erasable optical storage media, and new C lan- guage software. R-E 26 FCC APPROVES NO-CODE A codeless Amateur Radio license class has just been granted by the FCC! MIKE STONE WBOQCD IF YOU'VE EVER THOUGHT ABOUT GET- ting an Amateur Radio license, but shied away from it because of the Morse code test, here's your chance. For the first time in U.S. Amateur Radio Service history, it will be possible to obtain a Tech- nician class Amateur Radio li- cense without passing a Morse code test. The Federal Communications Commission (FCC) Docket number 90-55, passed on De- cember 13, 1990, eliminates the 5 wo rd-per- minute (WPM) prereq- uisite for the new Technician class license. The relaxed re- quirements for the Technician li- cense will take effect February 1, 1991. The FCC took this action in re- sponse to numerous petitions and public comments. Among the organizations who petitioned the FCC was the American Radio Relay League (ARRL). They be- lieve the codeless Technician li- cense will open the door to Amateur Radio for qualified per- sons who find the international Morse code for continuous wave (CW) telegraphy to be a barrier. At a press conference held shortly after the Commission's meeting, the FCC's Private Radio Bureau Chief Ralph Hafler W4RH said "The Amateur Service is not growing as it should relative to what it has to offer." The FCC be- lieves that passing Docket 90-55 will keep the U.S. at the forefront of communications research and development, and help to recruit new qualified people into the Am- ateur Radio Service. In addition to the above, the FCC has also passed Docket 90-356, which will affect licens- ing requirements for handicap- ped individuals. The high-speed CW code test will now be waived for some handicapped individu- als if their physical condition makes it impossible to learn the code at the required speeds. A physicians certificate will be re- quired to determine eligibility of this waiver. FCC license grades There are currently five levels of FCC Amateur "Ham" Radio li- cense grades, in ascending order: Technician, Novice, Gener- al, Advanced, and Extra. Each grade of license carries with it specific operating privileges and assigned frequency areas in which the user may transmit sig- nals over-the-air. Presently, Ama- teur Radio license grade require- ments include: • Technician — No Morse code, a 55-question test is required in- volving electronics and radio the- ory operation. • Novice— 5-WPM CW. • General— 13-WPM CW. • Advanced— 13-WPM CW • Extra— 20-WPM CW, ' All license grades require a writ- ten theory test. The Novice and Technician written tests are the same. The General, Advanced, and Extra written exams get in- creasingly difficult. Privileges for the new Techni- cian-grade license are 30 MHz and above with all mode, voice and repeater privileges. That in- cludes the 50-MHz, 6-Meter band (in which worldwide DX is possi- ble), the popular 2-Meter band (144-148 MHz) , which features lo- cal FM simplex, repeater, satel- lite, radio teletype and packet or computer activity. The 222 to 224-MHz, 420 to 450 MHz (voice, satellite and ATV), 900- and 1200- MHz bands and above are also in- cluded within the operating priv- iliges of the Technicians license. The present Novice class cate- gory grants CW and limited "voice talk" privileges on 28-MHz worldwide open HF bands which can be obtained by passing a 5 WPM-code exam and theory test. The General, Advanced and Ex- tra class licenses offer unre- stricted "talk" and mode HF privileges as well as more fre- quency space. The recruit for radio hobbyists Ham Radio has lost quite a number of significant pioneers who first began hobby operations back in the 1920s and 30 s. Many of those "true" Hams began tin- kering with radio, TV and elec- tronics as kids in their teens and early twenties which now puts them well into their seventies and eighties. All Hams mourn the loss of those talented individ- uals, many of whom actually changed the world as we know it today with their innovations, in- ventions and spirit. Currently, there are approxi- mately 495,166 Ham-radio li- cense holders in the U.S. As of 1990, the number of operators by license class are: • Technician— 104,771 • Novice— 53,219 • General— 119,393 • Advanced— 126,050 • Extra— 91,733 The American Ham Radio com- munity has been making serious efforts to recruit new members since about 1980. Amateur Radio has captured the interest and li- censed many young people with- in its ranks. Yet, we need more new increased active numbers to sustain the operating frequen- cies that the FCC has granted us. We also realize that we want to be selective in those that we want to bring into our fraternal ranks. Amateur Radio hobbyists are interested in attracting a clien- tele of technically qualified elec- tronic hobbyists that, as a group, will contribute and advance the hobby even further. With a little t> help and guidance, those people f= would make excellent additions g to the overall Ham Radio com- 2 27 en o cc LU 6 Q < EC munity. Radio Electronics read- ers are just such a targeted after group. Now's your chance to join us! Getting to know Ham Radio The fastest way to get ac- quainted with Ham Radio is to subscribe to some of the indus- try's best publications. By far, the largest Ham organization in the country is the (ARRL). They have been around a long time and have a vast organization set up to help interested or new Hams. AARL has many publications about nearly every facet of the hobby. They also publish the most widely read Ham monthly publication QST magazine. Call or write for more information. (The names and addresses of all organizations and publications we mention are listed in the ac- companying sidebar.) Other recommended Ham Ra- dio publications include 73 Ama- teur Radio Today, published monthly at $24.97 per year and CQ Magazine, published monthly at $22.95 per year. CQ also has a 1991 Amateur Radio Equipment Buyers Guide of more than 1.000 Ham products, and a separate Antenna Buyers Guide, both priced at $4.95 each, $6.00 foreign. Worldradio is pub- lished monthly at $13.00 per year. Spec-Corn is a specialized Ham Radio-based technical publica- tion that's available for those in- terested in fast- and slow-scan television, facsimile, radi- oteletype (Baudot, ASCII and AM- TOR), packet radio. Orbiting Satellite Carrying Amateur Radio (OSCAR), space and TVRO com- munications, lasers, microwave and computers. (The new Techni- cian-grade codeless Amateur Ra- dio license now allows those mode-operating privileges!) Spec-Corn supports a growing USATVS national ham-TV organ- ization and sponsors one of the best dedicated Ham Radio com- puter telephone landline BBS's in the country. The Spec-Corn Jour- nal is published bi-monthly, at $20.00 per year in the U.S.; $25.00 per year in Canada and Mexico; $30.00 foreign. A special V'i year trial subscription is avail- able for just $10.00 (3 issues). A good source of available ama- teur equipment is contained in the Amateur Electronic Supply catalog. FCC testing and study materials can be obtained from either the ARRL or the W5YI Group. Ham Radio computer software for the Radio Shack TRS80 color computer, IBM, Commodore, Apple, AmIGA, and other systems is available from Ham Radio Software. Ask for their current catalog and state the type of computer you own. A special multi-page "Get Ac- quainted with Ham Radio" pack- age of useful information is NAMES AND NUMBERS The American Radio Relay League (ARRL) 225 Main St.-Dept. RE Newington, CT 06111 (203) 665-0161 BBS: (203) 665-0161 73 Amateur Radio Today Wayne Green Enterprises WGE Center-Dept. RE Hancock, NH 03449 1-800-289-0388 Colorado: (303) 447-9330 CQ Magazine CQ Communications, Inc. 76 North Broadway-Dept. RE Hlcksville, NY 11801 (516) 681-2922 Worldradio Worldradio Inc. 201 Lathrop Way, Ste. D-Dept. RE Sacremento, CA 95815 (916) 457-3665 The Spec-Corn Journal Spec-Corn Communications & Publishing Group, Ltd. P.O. Box 1002-RE Dubquque, IA 52004 (319) 557-8791 Electronic Cottage Computer BBS: (319) 582-3235 (300-2400 baud at 8-N-1) Amateur Electronic Supply 5710 West Good Hope Road Milwaukee, Wl 53223 (414) 358-0333 The W5YI Group P.O. Box565101-RE Dallas, TX 75356 1 -800-669- W5YI (9594) Ham Radio Software R2 Box 86-RE Clarence, I A 52216 Amateur Radio Data Systems & Research C/O Connie Marchik 1007 Cedar Street Tipton, IA 52772 available to Radio Electronics readers for just $5.00. Include three 25-cent postage stamps to help with return mailing. This package offers money-saving val- ues, listings of Amateur Radio dealers and equipment sup- pliers, other trade magazine sources, frequency-operating charts, dedicated Ham Radio computer BBS's around the country and a full report on the new FCC Docket 90-55 codeless license! You can order from Amateur Radio Data Systems & Research. The 1991 Dayton Hamvention If you've ever been to a "ham- fest", you know it's like a gigantic flea market of new and used sur- plus goodies with talks and lec- tures and, yes, FCC license testing. There are hundreds around the country held each year. The biggest grand-daddy of them all is coming up the last weekend in April! The Dayton, Ohio Hamvention draws nearly 30,000 Hams from all over the world. There are many good forums you can attend for free, covering just about all facets of the Ham Radio hobby. If you do attend, be sure to stop by the Ramada Inn North (170/175 Little Creek road exit) on either Friday or Saturday night. Spec-Corn Communications & Publishing Group, Ltd. will be holding its 6th annual Ham-TV Workshops there. On Friday April 26, the en- tire evening will be devoted to "Early Radio & TV" nostalgia, with actual scanning-disk dem- onstrations and equipment. Sev- eral speakers are lined up to reminisce about the good old days. This will be a real treat if you're an Antique Wireless collec- tor or hobbyist as well. Saturday nights session covers ATV and WEFAX image systems. Information on the Dayton Hamvention will be in the "Get Acquainted with Ham Radio" package mentioned earlier. If you're in the area that weekend, come over and say heilo! We hope this good news moti- vates many of you to take full ad- vantage of such a rare oppor- tunity! Amateur Radio is an interesting, educational and fun hobby. The FCC has now relaxed their rules, so go for it before they change their mind! R-E 28 CIE Gives You The Training You Need to Succeed, At Your Own Pace... & In Your Own Home! Discover Your Career Potential In The Fast-Growing Field Of High-Tech Electronics! If you're anxious to get ahead ...and build a real career.. .you owe it to yourself to find out about the Cleveland Institute of Electronics! CIE can help you discover your career potential in the fast growing field of high-tech electronics. A career that will challenge and excite you every day... reward you with a powerful feeling of personal accomplishment... and deliver a level of financial security you may have only dreamed of before! As the leading school in home-study electronics, CIE has helped over 150.000 students in the U.S.A. and over 70 foreign countries get started in this exciting field. To find out how CIE could be helping you... read on... then send for a CIE catalog TODAY! A Growing Need For Trained Professionals! The career opportunities shown here are only a few of the challenging, high- paying careers you could enjoy as an electronics technician. You could be the "brains" behind the scenes of an exciting TV broadcast... trouble-shoot life-saving medical equip- ment... design exotic new aeronautics systems... CI E's job-oriented programs offer you the quickest possible path to the career of your dreams! And CIE also features military and union re-training, to build on what you already know. Dozens Of Fascinating Careers To Choose From! Even if you aren't sure which career is best for you, CIE can get you started with core lessons applicable to all areas of electronics. As you advance, CIE makes job opportunities available to you through the bimonthly school paper, The Etectmn. Data Communications Automotive Electronics I **. % y mt - -'- B S 1 ■ j /ii ilea 6- - i F ■ TltvP Compu -' ^BR Mr % Avionics 'er- Assisted Manufacturing Consumer Electronics Military Electronics Personal Training From A Renowned Faculty. Unlike the impersonal approach of large class- room study, CIE offers you one-on-one instructional help 6 days a week, toll-free. Each CIE lesson is authored by an independent specialist, backed by CIE instructors who work directly with you to answer your questions and provide technical assis- _ _ „ tance when you need it . Practical Training... At Your Own Pace. Through CIE, you can train for your new career while you keep your pres- ent job. Each course allows a gener- ous completion time, and there are no limitations on how fast you can study. Should you already have some electronics experience, CIE offers several courses which start at the intermediate level. "State-Of-The-Art" Facilities & Equipment In 1969, CIE pioneered the first elec- tronics laboratory course, and in 1 984, the first Microprocessor Laboratory. Today, no other home study school can match CIEs state-of-the-art equipment. And all your laboratory equipment is included in your tuition cost, There is no extra charge— it's yours to use while you study at home and on the job after you complete your course! Earn Your Degree To Become A Professional In Electronics! Every CIE course you take earns you credit towards the completion of your Associate in Applied Science Degree, so you can work towards your degree in stages. And CIE is the only school that awards you for fast study, which can save you thousands of dollars in obtaining the same electronics education found in four-year Bachelors Degree programs! Send For Your Catalog Today! CIE World Headquarters ® Cleveland Institute of Electronics, Inc. 1776 East 17th St., Cleveland, Ohio 44114 p YES! Please send me your independent study catalog (For your convenience, CIE will have a representative contact you— there is no obligation.) Apt* Area Codei Phcre No. Check box for G, I. Bill bulletin on educational benefits: d Veteran □ Active Duty Mail This Coupon Today AE07 > 33 31 HOW MUCH SHOULD YOU PAY FOR 10 INSTRUMENTS, 39 FUNCTIONS AND 4000 COUNT ACCURACY? Just $139.95 if you say PROTOMETER "I XI DC VOLTMETER X) AC VOLTMETER [3] OHMMETER [T) 20A AMPMETER XI DIODE/LED TESTER XI TRANSISTOR TESTER X) CAPACITANCE TESTER XI FREQUENCY COUNTER X| LOGIC PROBE [10) CONTINUITY TESTER GLOBAL SPECIALTIES 4000 O Z o B UJ a < PROTOMETER™ 4000 is the Professional Multi-Function Por- table Instrument System. Ten test instruments in a 3-3/4 Digit, 4000 count handheld package. Pack- ing the power of our complete instrument line. Combining a digi- tal multimeter, frequency counter, transistor/capacitance tester, and more into a durable no-nonsense Call Toil-Free For Details 1-800-572-1028 drop-resistant case. Plus standard features like a large LCD display, peak hold, and a unique high-volt- age warning indicator. Looks like the competition's DMM and priced like one too! GLOBAL SPECIALTIES' CIRCLE 182 ON FREE INFORMATION CARD But PROTOMETER™ 4000 is much more than a DMM. Com- pare for yourself. Clearly the best value in portable instruments. Why pay just as much for a DMM, when you can get ten test instruments forone low price. How much should you pay? Just $1 39.95, if you say PROTO METER™ 4000. Order Yours Today!! $1 09.30 Global Specialties* A028 70 Fulton Terrace, New Haven, CT 06512 Telephane:[2u3)624-3103. clnlerplei Electronics, 1991. 32 BUILD THIS MAGNETIC FIELD METER Determine your exposure to line-frequency magnetic-fields with our easy-to-build portable ELF gaussmeten ^^H REINHARD METZ IF YOU ARE ONE IN A GROWING number of people who are con- cerned about the potentially harmful effects of exposure to magnetic fields, you will be Inter- ested in this important con- struction project. Now you can build your own gaussmeter, and determine the magnitude of magnetic flux densities in and around your home. Our hand- held, battery-operated magnetic- field meter is sensitive from 0.1 micro tesla (is.T) to 20 milliteslas (mT), and has a frequency range from 50 Hz to 20 kHz. Why all the worry? Magnetic fields arc all around us- They occurr from the genera- tion, distribution, and use of 50 and 60- Hz electricity, electronic equipment, and even from Ear- th's magnetic field, which has al- ways been present throughout Man's evolution. Man has been "tuned" into Earth's steady mag- netic field of about 30 ^T [at sea level) for millions of years. Some sources of excessive magnetic fields that have caused the great- est public concern include power-distribution substations, power lines, CRT terminals, and use of appliances. Magnetic field intensities can vary greatly, depending on the ex- posure source and the distance from that source. The rate at which the field intensity falls off with distance can vary from one source to another, depending on how well the current-carrying lines are balanced, or how well the opposing lines of magnetic flux cancel each other out. Fields from coils, magnets, or transformers drop off rapidly with distance by a factor of 1/r 3 , In power lines, if currents flow in opposite directions, the drop-off is 1/r 2 because of partial field can- celing. When unbalanced cur- rent exists, the field intensity falls off less rapidly as 1/r. Figure 1-a, -b. and -c show drop-off rates of 1/r. 1/r 2 , and 1/r 3 , respectively. Figure 2 lists some of the many sources of magnetic field exposure, with their range of intensities and drop-off rates. Although a great deal of contro- versy still prevails, many people in the scientific community be- lieve that exposure to magnetic fields of extremely-low frequency (ELF fields of 1-100 Hz) may pose a risk to human health. Some disturbing findings of exposure to ELF fields include a significant increase in serum triglycerides (a possible stress indicator) In hu- mans, dis- orientation of chicks (a result suggesting that bird migration could be affected), and a slowed reaction time in monkeys. A study conducted by epi- demiologist Nancy Wertheimer and physicist Ed Leeper, found that exposures to magnetic fields as small as 0.25 |xT correlated with a rise in cancer rates. In the study, the researchers examined wiring and transformers in the neighborhood of birth homes of children who had died of leuke- mia between 1950 and 1975, along with those of a control group of children who did not have the disease. The results of their studies were published in The American Journal of Epi- demiology (March. 1979). Some experts argue that other factors, such as pollution and exposure to chemical carcinogens, make interpretation of those findings very difficult. Standards for acceptable ex- posure to ELF fields are emerg- ing, as are results of studies FIG. 1— MAGNETIC FIELD drop-offs. A fast drop-off of 1/r 3 (a), %flfl (b), and a slow drop-off of 1/r (c) Is typical of many sources of magnetic fields. describing possible hazard lev- els. If you are more interested a detailed account of scientific findings and the political history of the effects of magnetic- field ra- diation, we suggest a three-part series of articles by Paul Brodeur, The New Yorker [June 12, 19, and 26. 1989). "60-Hz and The Human Body", IEEE Spectrum, Parts 1-3, Volume 27, Number 9, pages 22-35 (August, 1990) is also a good source for technical information. The Environmental Protection Agency (EPA) has pub- lished a report titled "The Evalua- tion of the Potential Car- cinogenicity of Electromagnetic Fields", publication number EPA/600/6-90/005B. This report contains analyses of 64 scientific studies, and is currently under review by the Scientific Advisory Committee. Well, that's enough back- ground for now. Let's examine some of the theory behind how the ELF meter works. Theory The quantity of magnetic flux density, B, is in units of webers/ meter 2 , or tesla (T). The magnetic flux, (J), is defined by the integral /dti Note that the value of N x d

equals 2itx60 = 377 For a coil size of 3 l / 2 " x 3", the area is .0068 m 2 , and therefore E = 2.56Nxa For the I2-turn pickup coil that we'll use, the sensitivity is 30 u,V per |xT. Circuit description The meter's 12- turn field pick- up is integrated into the unit's circuit board. For remote sens- - 3 ! ,'i( INCHES CO o z o UJ 6 o < COMPONENT SIDE OF THE PC BOARD. SOLDER SIDE OF THE PC BOARD. 34 SOURCES OF MAGNETIC FIELD EXPOSURE POWER GENERATING STATION (20KV). 3.0mT STEP-UP TRANSFORMER 5-20 M T TRANSMISSION LINES (69-765KV) S-70nT, WITH MAGNETIC FIELD DROP-OFF AT 1/r 2 STEP-DOWN TRANSFORMER 5-20nT PRIMARY DISTRIBUTION LINES (4-35KV) 1-5jiT, WITH MAGNETIC FIELD DROP OFF AT 1/r* DISTRIBUTION STEP-DOWN TRANSFORMER 0.1 - UtT, WITH A FAST MAGNETIC FIELD DROP-OFF AT 1/r* SECONDARY DISTRIBUTION LINES (115/230V) 0.1-lnT WITHASLOW MAGNETIC FIELD DROP-OFF OF 1/r (DUE TO UNBALANCED PHASE AMD NEUTRAL LINES) I REFRIGERATOR 0.1 -1uT. SOURCE OF MAGNETIC FIELD IS FROM MOTOR IN BACK OF THE APPLIANCE, SO EXPOSURE IS LOW, DROP-OFF IS 1/r' ELECTRIC UTILITY GROUND HOUSEHOLD WATER PIPES CARRY RETURN CURRENT AND CREATE UNBALANCED FIELDS. GROUND CURRENTS CAN BE A PRIMARY SOURCE OF CONTINUOUS EXPOSURE IN SOME HOMES, WITH A SLOW DROP-OFF AT 1/r ELECTRIC RANGE 6 -200M.T MAJOR SOURCE OF MAGNETIC FIELD IS RESISTIVE HEATING ELEMENTS, DROP-OFF IS 1/r 3 TELEVISION 2-50^T, MOSTLY RF FIELDS BUT POWER TRANSFORMER AND VERTICAL SWEEP PRODUCE MAGNETIC FIELDS, DROP-OFF IS 1/r 3 ELECTRIC BLANKET 1-5ut, HEATING ELEMENTS ARE CLOSE TO BODY, AND FIELD EXPOSURE CAN LAST OVERNIGHT, DROP-OFF IS 1/r 2 VACUUM 200-1000fil DROP-OFF IS 1/r 3 MIXER 5D-600pT, DROP-OFF IS 1/r 3 HAIR DRYER 10-2000nT, DROP-OFF IS 1/r 3 > J} FIG. 2— HERE ARE SOME PRIMARY SOURCES of magnetic field exposure with the range of field intensity in teslas, and drop-off rates. 35 FIG. 3— SCHEMATIC OF THE MAGNETIC FIELD METER. The magnetic field is picked up by L1 and appears as a voltage that is proportional to the field strength at the input of IC3- a, which amplifies the signal to 100 jj.V per ^T. The signal is then further amplified by IC3-b and IC3-c to achieve the three tesla ranges. g z o o UJ O Q < EC All resistors are IV watt, 1%, unless otherwise indicated. R1, R3, R1 2— 10.000 ohms R2, R11, R15— 33,200 ohms R4— 10 ohms R5-R7, R22-R24, R27— 1 megohm R8, R29 — 464,000 ohms R9. R13, R2S— 100,000 ohms R10, R14— 1000 ohms R16, R20— 42,200 ohms R17 — 2 megohms R18— 51,100 ohms R19-^t6,400 ohms R21— 1-megohm potentiometer, 5% R25— 22,100 ohms R26— 20.000-ohm potentiometer, 5% Capacitors CI, C8— 4,7 ^F, 10 volts, electrolytic C2, C14 — 0.1 |j.F, electronic or polyester PARTS LIST C3, C7, C15— 0.1 (xF, polyester C4, C6, C10— 10 m.F. electrolytic C5, C9 — 6.5 pF, ceramic disc or mica C1 1—100 p.F, 10 volts, electrolytic C12— 22 u.F, 10 volts, electrolytic C13— 330 pF, polyester C16 — 0.047(j.F, polyester or ceramic disc C17— 0.68 m-F, polyester Semiconductors D1, D2— 1N4148 switching diode Q1, Q2— 2N4124 NPN transistor IC1— !CL 7106 A/D converter IC2— 4070 or 4030 quad 2-input exclusive-OR gate IC3 — LF347 quad JFET input op -amp DISP1— LCD-002 liquid crystal display Other components S1— MSS1200, SPST (Alco) S2— MSS4300. SPDT (Alco) L1— 18 turns, 3" diameter remote-sensing coil (optional, see text) B1— 9-volt alkaline battery, with connector Case— Pac-Tec, HPS-9VB NOTE:The following items are avail- able from A & T Labs, P.O. Box 552, Warrenville, IL 60555: A kit of all parts including PC board and case, without battery, S85.00; an etched, drilled and plated through PC board with solder mask and silk-screened parts placement, $15.00; a fully as- sembled and tested unit, $109.00. Add 6.75% sales tax for Illinois resi- dents, 5% shipping and handling in U.S., 12% shipping and handling in Canada. Check or money order (UPS COD in contiguous U.S. only) is ac- cepted. 36 ing, an external field coil probe can be used. Figure 3 shows the complete schematic of the cir- cuit. The magnetic field picked up by the coil appears as a volt- age, which is proportional to field strength and frequency at the in- put of a cascaded amplifier IC3-a, -b. and -c. With a first stage am- plifier gain of 3.3 set by R12-R10, the overall sensitivity is 100 u.V per |xT, or 100 mV per mT. The meter sensitivity is nominally 2 volts full scale, leading to the lowest level sensitivity of 20 mT full scale. Op-amp IC3-a amplifies the signal to a normalized level of 100 |xV per 1 |jlT. That voltage is fur- ther amplified by 1, 100, or 10,000 by IC3-b and -c. The three amplifier stages provide the three magnetic field ranges of 2 rnT, 200 |xT. and 2 uT (full scale). Components R3-C3 and R12-C7 establish a frequency roll-off characteristic that compensates for the frequency-proportional sensitivity of the pickup coil, and set the 20-kHz cut-off point. Finally, IC3-d is a precision rec- tifier and peak detector. Its out- put drives IC1, a combination analog-to-digital (A/D) converter and LCD driver. Components R25-R29 and C13-C17 are used by IC1 to set display-update times, clock generation, and ref- erence voltages. The decimal points are driven by IC2, as deter- mined by the range-select switch S2. Transistors Ql and Q2 serve as a low-battery detector, and turn on the battery annunciator in the LCD when the battery volt- age drops below 7 volts. Assembly and checkout The finished unit shown in Fig. 4 uses a double-sided PC board, which is available from the source mentioned in the parts list. We also show the com- ponent side and solder side of the PC board if you choose to make it yourself. You can, however, build the circuit on a perforated con- struction board if you like, but remember to include the 18- turn remote sensing coil, LI, as indi- cated in the Parts List, Mount all parts below the LCD display first. It's easier to fix assembly prob- lems if a socket is used with the LCD. Install all parts as shown in Fig. 5 paying attention to compo- nent valves and capacitor polar- R21 PICK-UP COIL RANGE-SELECT SWITCH S2 FIG. 4 — THIS IS AN INTERNAL VIEW of the magnetic field meter. Assembly is easy, just install all components below the LCD first. TP4Q QTP3 TP16 6TP2 FIG. 5— PARTS PLACEMENT DIAGRAM. ities. If you are using the internal sensing coil, install jumpers be- tween L1-TP3 and L1-TP4. If you are using the case spec- ified in the parts list, raise and angle the display as necessary with wire-wrap IC sockets. Make holes in the front panel for SI and S2. Mount the finished PC board in the case using a spacer for the single screw holding the center bottom of the board, and attach the battery connector. You are now ready for power-up and checkout. With power on, adjust R26 for 1.000 volt between TP1 and TP2. Then, select the 20 mT range and short the pickup coil with a very short lead between TP3 and TP4. Adjust offset-null potentiometer R7 for a display of 0.00. Remove the jumper, and the meter is com- plete. > -o 3P to to 37 Electronics Engineers & Designersl 95 Take any 3 books for only A. 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Dept. 90 3 j P.O. Box 2824, San Francisco, CA 94126 , Please rush FREE details immediately! 421 NAME. 1 ADDRESS 1 CITV STATE ZIP 40 TURNS 16AWG 1 METER VOLTMETER B=Nxlx4it10- 7 (T) =40x4rt10- 7 x1 =5.03x1 0- 5 1 (T) 1 AMP WILL GENERATE sSOuT 60 Hz SINE-WAVE GENERATOR FIG. 6— USE THIS TEST SETUP TO accurately calibrate your meter. A known current is passed through a coil whose field intensity is known. A sine-wave generator provides the 60 Hz frequency, and an audio amplifier is coupled to the coil by an 8-ohm resistor. Measure the voltage across the resistor, and use the calculations shown. Calibration Calibration of the meter is basically determined by the pick- up-coil characteristics, amplifier gains, and meter reference-volt- age setting. The amplifier gains, as we previously discussed, are chosen to match the coil charac- teristics as closely as possible. If you desire to calibrate your meter more exactly, you will need to generate a known magnetic field intensity. One way to do that is to pass a known current through a coil configuration whose field pattern charac- teristics are known. Figure 6 shows such a calibration setup. A good controllable signal source is a sine-wave generator and an au- dio amplifier, whose output is coupled to a coil through an 8- ohm resistor. Measuring the volt- age across the resistor gives the current. Then, calculate the mag- netic field according to Fig. 6. (Note that while all references to field strength here are made in teslas, gauss are also commonly used. The conversion is easy: 1 tesla = 10,000 gauss.) Place the meter inside the coil and turn it on. Use the highest sensitivity scale that does not over range the display. An over- range is indicated by a display of 1 followed by three blanks. In most cases, the 2 uT range is sat- isfactory. Measurement interpretation A great deal of controversy ex- ists in the emerging understand- ing of potential health hazards of low-frequency magnetic fields. The International Radiation Pro- tection Association (IRPA)hasset some interim standards based on 1984 World Health Organiza- tion guidelines. Those I RPA stan- dards specify a continuouts maximum magnetic field ex- posure for the general public of 100 u,T, and 500 uT as the max- imum occupational exposure al- lowed over the entire working day. Some European countries have already adopted strict mag- netic field emission require- ments for video display termi- nals, but the United States is taking a more cautious approach about developing and enforcing such guidelines. Whatever studies and data you think are accurate, now you have a way to measure your own ex- posure and take whatever action you believe is prudent. r-e LINE POWER FROM 12 VOLTS Build a 40-watt DC-to-AC inverter, and power AC Vi WOULDjg I BEttEVE THAT THIS AKTI- cle .was written on an electric typewriter while the author was Rg next to a stream on a Bmping trip? The typewriter was powered from our 40-watt in- verter that can be plugged into an automobile's cigarette lighter socket. The unit has enough power for many items that nor- mally don't go on camping trips, such as a TV, a stereo, an electric razor, or a desk lamp. However, it also has some uses that may not be as obvious; it can be used to power items such as an os- cilloscope or soldering iron when doing electronics work in the field. On road trips, the inverter can be used to power a camcorder battery charger. The inverter draws a max- imum of 5 amps, which is com- pletely safe for an automobile cigarette lighter socket, and the no-load current is only half an amp. The output voltage is regu- lated and remains fairly constant from no-load to full-load. Figure 1 shows the output-voltage wave- form superimposed over a sine wave. The rectangular output waveform has the same RMS and peak voltage as the sine wave, so the device being powered will , n W AT1 AC INYERTliK i£U VAC ^ DAVID CUTHBERT never know the difference. The rectangle-wave operation greatly increases efficiency. The wave- form would look similar if dis- played on an oscilloscope. Operation The inverter, the schematic of which is shown in Fig. 2, is actu- ally a push-pull audio amplifier. The "input," or reference signal, is a 5-volt square wave. The out- put is 340-volt peak-to-peak AC signal. The feedback signal is rectified in order to match the DC reference signal. On one half of the AC waveform, the upper three FET's are gated on, and on the other half the lower three FET's are on. Normally, 120-volt AC outlets have one side at ground and one side that's "hot," The hot side al- ternates from -170 to +170 volts. The inverter output is a lit- tle different. On one half of the AC cycle, one side is near ground and the other is at +170 volts. During the other half of the cycle the situation is reversed. Op-amp ICl-a and its associ- ated components form a 300-Hz clock oscillator, and counter IC2 divides the clock signal by four to obtain a 75-Hz inverter frequen- apptiances from your automobile cigarette lighter. cy. The 75 Hz, rather than 60 Hz, is used to avoid transformer sat- uration. Some electric clocks ' run fast with that frequency' most electronic gear will worl just fine. Decade counter IC2 controls the timing of the refer- ence signal and the gating-on of the error-amp signal to the prop- er set of FET's. Figure 3 shows the timing rela- tionships in the inverter. When IC2 pin 3 goes high, the output of buffer ICl-c is high. That reverse biases Dl and allows the error amp signal to reach Ql, Q2, and Q3. At the same time, IC2 pin 4 is low, which causes the output of buffer ICl-d to be low. That grounds the gates of Q4, Q5, and Q6 thereby turning them off. Pins 2 and 7 of IC2 are also low, so Q7 is off. A 5-volt reference from regulator IC3 is now present at the error-amp's (ICl-b) no n- inver- ting input. The reference-signal rise time is slowed by Rl 2 and C2 in order to avoid output over- shoot, and the gain and frequen- cy response of the error amp is set by R15, R25, and C3. Next, pin 2 of IC2 goes high, which turns Q7 on and the refer- ence signal is pulled to ground. Pins 3 and 4 of IC2 are now low > 3 to CO 43 FIG. 1— BECAUSE THE OUTPUT-VOLT- AGE waveform, which is shown here su- perimposed over a sine wave, has the same RMS and peak voltage as the sine wave, the device being powered will never know the difference. and the FET gates are grounded, turning them off. Pin 4 of IC2 now goes high and the other three FET's are gated on. The ref- erence signal now rises to 5 volts, and the other half of the AC out- put waveform is generated. The next clock pulse causes IC2 pin 7 to go high; all FET's are now off and the reference is set to zero. The following clock pulse resets 1C2 and another cycle begins. A filter that protects the CMOS circuitry against alternator spikes and reversed input polar- ity is formed by R7, C8, and D7. Components R9 and C4 filter output spikes, and R18-R21 are pre-load resistors to stabilize the inverter when no load is con- nected. Although the FET's have no current-equalizing source re- sistors, they still share current fairly equally. (When a FET "hogs" current it heats up more and its on resistance increases, causing it to draw less current.) Construction The inverter circuit was built on a perforated construction board. Transistors Ql, Q2, and PARTS LIST All resistors are Vi-watt, 5%, unless otherwise noted. R1-R7 — 100 ohms R8— 1000 ohms R9— 1000 ohms, Hi-watt R10, R11— 4700 ohms R12-R16— 10,000 Ohms R17— 10,000-ohm potentiometer R18-R21— 22,000 ohms, '/j-watt R22-R26— 100,000 ohms R27, R28-™470,000 ohms R29— 1 megohm Capacitors C1— 0.001 |i.F, ceramic disc C2— 0.01 (J.R ceramic disc C3—O.0O47 (xF, ceramic disc C4 — 0.05 ixF, 200 volts, ceramic disc or metal film C5-C7— 0.1 p.F, ceramic disc C8, C9 — 470 m-F, 35 volts, electrolytic Q3 share a 1.5- by 4-inch heat- sink, and Q4. Q5, and Q6 share another; the heat sinks are made of aluminum sheet. Figure 4 shows an internal view of the in- verter. In the prototype, the FET's were not insulated from the heat- sinks because the heatsinks are isolated from ground and all other circuitry. If you use any other heatsinking configuration, continued on page 68 Semiconductors IC1 — LM324 quad op-amp IC2— 4017 CMOS decade counter IC3— LM7805 or LM340-5 +5-volt regulator D1-D7— 1N4003 diode Q1-Q6— IRF511 60-volt 3.5-amp MOSFET Q7— 2N2222 or 2N3904 NPN transistor Other components T1— 120/12.6 volt center-tapped 3-amp power transformer J1— banana jack, red J2— banana jack, black J 3— AC power receptacle F1 — 5-amp stow-blow fuse SI— SPST 6-amp switch NE1— neon indicator light with series resistor Miscellaneous: fuse holder, perforated construction board, enclosure, alumi- num for heatsinks, standoffs for mount- ing circuit board, wire, solder, etc. FIG. 2— THE INVERTER is actually a push-pull audio amplifier where, on one half of the AC waveform, the upper three FET's are gated on, and on the other half the lower three FET's are on. Build this video telephone COLBY Su/7c/ a f wo- way videophone and send and receive video pictures over standard phone lines to and from anywhere in the world! - CHARLES COLBY LAST MONTH W-. SAW I [QWTHKVlDEQ- phone operates. Now let's build the unit, hook it up. and get it working. Construction Building this project is actually very easy, because of the relatively small number of parts used. That's because the video control- ler IC takes care of many func- tions by itself, eliminating the need for several other parts. It's a good idea to use a PC board for this project for two rea- sons: one, to lessen the like- lihood of wiring mistakes, and two, so that you end up with the extremely compact unit you see pictured in this article. We have provided the foil patterns to make the double-sided board if you so desire, or you can also buy a finished board, as well as ail other required parts, from the source mentioned in the parts list. Figure 6 shows the parts-place- ment diagram for the videophone base unit. There's nothing crit- ical concerning the construction of the unit, just as long as you are careful to observe proper compo- . nent orientation, and be sure to use sockets for all of the IC's. The four LED's must be installed with the %-inch standoffs, as shown in Fig. 7, and bent over at a 90- degree angle so that they can be seen through the holes in the front panel of the unit. The two voltage reulators. IC1 and IC2, are secured to the metal bottom half of the case we used, for heat sinking. If you don't use the same case, you should consider heat sinking of some kind. After carefully inspecting the completed board for errors, you can install it in a project c the case that the prototype unit is installed in is available from the source mentioned in the parts list, as is the circular case for the small CCD camera module. Fig- ure 8-a is an actual-size label for the front panel of the unit, and Fig. 8-h is for the back. They will fit right onto the available case, but can be used for any setup. > ■v 3 45 to o z Q CE I- o HI o D < Ql 46 FIG. 6— PARTS-PLACEMENT DIAGRAM for the videophone base unit. Observe proper component orientation, and use sockets for ail of the IC's. Operation Operation of the videophone is very easy. The front-panel Freeze push button captures and holds a frame of video from the camera, and Send transmits the picture over the phone line. The Auto button automatically freezes and sends every 38 seconds. The Trim button is pressed and held until the top part of the picture straightens out {it adjusts for the difference in horizontal timing signals between different TV cameras and monitors). If you press and hold the button, it will automatically run one way through its adjustment range. If you release the button for 2 sec- onds and then press it again, it will automatically run the other way through its adjustment range. The LED above the Freeze but- ton is the power on/off indicator. The LED above the Trim button is on when the unit is receiving a video frame and off when trans- mitting. The LED above the Auto button is on when in the auto- matic send mode, and the LED above the Send button is on when you're actually transmit- ting a picture. FIG. 7— THE FINISHED BOARD should look similar to the one shown here. CBLBY POWB* 4 + + + ■+ SEND ON + VIDEOMODEM™ FREEZE TRIM AUTO SEND [pWR 12VDCIN VIDEO IN CAMPWK PHONE UNE VIDEO OUT 6V OUT] b FIG. 8 — AN ACTUAL-SIZE LABEL for the front panel of the unit is shown In a, and one for the back panel is shown in b. HISTORY OF VIDEOPHONES The first public showing of two-way vid- eophones was at the AT&T booth at the New York World's Fair in 1939. And, of course, Dick Tracy has always had a two- way videophone on his wrist. Videophones have had several false starts over the years. While videophones offer a tremendous possibility for ex- change of information, there is a certain reluctance on the part of a lot of people to use them. (Is my hair combed alright?} However, one of the main problems with videophones has been the bulky equip- ment that used to be required. That was very much the case with the videophones like Robot Research's 1978 picture phone box (see Radio-Elec- tronics, August, 1982). With the video- phone described in this article with its very small, easily aimed camera, everything (except a phone) fits in about one half the desk space as a standard telephone. Shown here is the author at age 17 with his 1961 videophone. It used a converted WWII iconoscope camera that measured about 2 feet long, afoot high and 9 inches wide, and weighed 50 pounds. In addition, a 6-foot high rack of equipment was re- quired to send and receive pictures in both slow- and fast-scan rates. Still pictures could be sent over phone lines and ama- teur radio channels using slow-scan tech- niques and regular fast-scan full-motion pictures could be sent over 450-MHz ham band TV frequencies. Slow-scan television (SSTV) was de- veloped during the late fifties to early six- ties by amateur radio operators to allow them to send pictures within the narrow bandwidth (3500 kHz) that the FCC per- mitted for transmissions below 450 MHz. In the old slow-scan format, a frame con- tained 128 lines, (Regular TV has 525 lines, and the Colby videophone has 260 lines.) The old SSTV format had a hori- zontal scan rate of a Krth of a second (versus Vi 5,734 second, or 63 microseconds for regular TV). Since there was no such thing in those days as a flash A/D converter or "frame grabber," you had to sit still for 8 to 10 seconds while the whole frame was being scanned. If you moved you would blur the picture... similar to the early days of pho- tography when the lens was required to be open for 10 seconds to get the proper "exposure. To view the picture on the re- ceiving end, the early SSTV systems used a long persistence P-7 phosphor CRT. That was required because it took 10 seconds to paint the picture on the screen. You could literally see the spot of light created by the scanning beam moving ac- cess each line, and by the time the bottom line of the screen was done, the top part of the picture was already fading. Then came analog scan converters that let you input slow-scan signals and output Msoth of a second still- video frames. They could be viewed on a regular fast-scan TV without the top fading out, but these ana- log units were bulky and expensive. The real breakthrough came in the early 701s when techniques were developed to CHARLES COLBY looks up at his partner, Jim Kennedy (on screen), to check the pic- ture quality on their gigantic 1962 video- phone system. store and retrieve images using digital techniques. The first solid-state scan con- verters used many shift registers to store data. The next step was the use of dynam- ic random access memory (ORAM) chips to store the data that was then converted to video. That's the method used in the videophone in this article. Slow-scan TV has been used for years by security companies for remote monitor- ing purposes. Also, many space vehicles still use SSTV to transmit pictures from space. The Viking and the Voyager space probes ate good examples. JPL of Pas- adena, California has been the main pro- ponent of SSTV use because it's very power efficient— an important factor on long-range space vehicles. The telephone company had a picture phone center in major cities for years where you could go and sit in a booth and talk and see someone in a similar booth. This was not only inconvenient, but also very expensive. About two years ago. several Japanese companies introduced home picture- phone units that sold for about $5GO.00-$600.00. These units are about the size of a small shoebox and have a built-in camera and monitor. One prob- lem, though, is that the camera is fixed in position, so the subject must move into the field of view of the camera. The units used an amplitude -modulated protocol which is very susceptible to noise on the phone lines. But the biggest problem, and perhaps the key element that has kept them from becoming widely accepted is the low, 96 x 96 pixel resolution. Our videophone has overcome many problems. It has a small size, an easily moved and pointed camera, high resolu- tion, 50 shades of gray, a noise-immune pulse-width modulation transmission sys- tem, and a high-tech look— it looks like it belongs on your desk! R-E PARTS LIST All resistors are Vj-watt, 5%, unless otherwise noted. R1— 510 ohms ( x 4) 8-pin SIP R2— 390 ohms ( x 5) 10-pin SIP R3— 10,000 ohms ( x 4) 8-pin SIP R4— 4700 ohms ( x 5) 10-pin SIP R5— 1000 ohms wire, project case, video camera, video J monitor, coaxial interconnecting leads f (for power and video between base unit g and monitor and camera), solder, etc. to 47 • / i • \zn.y -vi n • f • • I • • • t *•;• •-•-* ••• • •/• • • • • • • • I v. _ ^ N **«N • TV h- • 3 ! /s INCHES - ORDERING INFORMATION Note: The following items are available • 240 x 320 lineCCD camera module from Colby Systems Corporation, (XP-CCD-1)— $299,99 + $5.50 S&H 2991 Alexis Drive, Palo Alto, Califor- • Sony 2-inch monitor (Sony-2) — nia, 94304 (415) 941-9090. Fax (415) $129.99 + $4.50 S&H 949-1019. Send check or US postal • Vldeophone-to-monitor power & money order. Checks take 2-3 weeks video cable (PVC-M)— $9.95 + $3.50 to clear. California residents add S&H 7.25% sales tax. All prices FOB Palo • Videophone-to-camera power & Alto or Clovis, California. Shipping video cable (PVC-C)— $9.95 + $3.50 charges are UPS ground, continen- S&H tal US only, and insurance is in- • All of the above items ordered at cluded. Add S5.00 handling fee to one time (Kit-complete) — each order. $599.99 + $13.25 S&H • Bare PC board (PCB-VP)— • A VHS video tape showing step- $24.99 + S3.50 S&H by-step assembly and testing, in- • PMC-VP video controller IC (PMC- cluding sample pictures — U7)—$49.99 + $3.50 S&H $19.95 + $4.75 S&H • Kit of ail other IC's including pre- • An assembled and tested version programmed IC8 (Kit IC-8)— of the videophone will be available $39.99 4- $3.50 S&H as soon as FCC testing and registra- • Kit of all discrete components (re- tion are completed. Write Colby Sys- sistors, capacitors, diodes, tran- tems for price list. 3 sistors, crystal, transformer, jacks, The following Items are available from Gettys Electronics, 22018 Frontier switches, LEO's, relay) (kit-VPC)— 3 $49.99 f $3.50 S&H Road, Clovis, CA 93612 (209) L • AC adapter (VP-AC)— 299-7828. J $9.99 + $4.50 S&H • Round video camera case (Cam- J • Kit of all of the above parts (every- case-1)— $29.99 + 55.50 S&H 3 3 E thing to build one complete video- • Videophone case with metal bot- phone base unit, except case) (Kit- tom and plastic top (VP-case-1)— unit)— $169.99 + $7.50 S&H $34.99 + $5.50 S&H. - 3 ! /» INCHES - In the automatic mode, every 38 seconds the videophone con- nects to the phone line for a period of 12 seconds. Therefore, if you called a monitoring site while the videophone is con- nected, you would get a busy sig- nal. However, if you wait 12 seconds and redial, the line will not be busy since the 12 seconds will have elapsed and won't start again for another 38 seconds. In actual use, you could hang up on the remote site after you have re- ceived one good frame of video. That entire sequence could actu- ally happen in under a minute, since the total cycle time for the videophone is 50 seconds (12 sec- onds sending and 38 seconds waiting). That's all there is to it. What was once something that only Dick Tracy could afford to own, is now available to the general pub- lic. You will no doubt find many uses for the videophone, and you can be the first on your block to have one! R-E 18 Here are two simple projects that will allow you to control things using up to eight voice commands. EXPER.MEN|| m tgf.ni II IN VOICE RECOGNITION DANIEL B. COOPER SOME OF THE MOST FASCINATING things that electronics experi- menters can do are those that seem impossible. Remote control and voice synthesis are two areas of experimentation that were once nearly impossible for hob- byists and amateurs to work with, but integrated circuits have brought both within the reach of even novice tinkerers. Another area that has always been very difficult to work with is voice recognition. And now there is a new IC which brings simple speech-recognition technology within the reach of novice experi- menters. Most voice-recognition proj- ects and experiments have used personal computers as the back- bone of the recognition device. A number of voice-recognition ex- pansion cards for both Apple and IBM-compatible computers are available, but they're relatively costly and require the computer in order to be usable. The voice- recognition IC, the VCP200 speaker-independent word rec- ognizer, is a stand-alone device that provides all of the essential elements for speech recognition in a single 20-pin package. The project There are a number of applica- tions, both serious and fun, useful and merely entertaining. for the VCP200. Rather than lim- it this interesting device to a sin- gle-purpose project, we are pres- enting two separate projects: one is suitable for experimentation — and also makes a nifty science- fair project — and the other is less ideal for experimentation but better for actual use in an ap- plication of one sort or another. A variety of adjustments and inter- facing techniques will be dis- cussed, and some flexible inter- face and driver circuits will be presented. None of the parts, with the exception of the VCP200 itself, are exotic or costly, and most are probably in your junk box or parts collection. The experimenter's version is a self-contained device with a mi- crophone and eight indicator LED's. The addition of a power supply is all that's needed. The project will recognize eight words and short phrases from almost any speaker, and light the corre- sponding LED in response. Out- puts are provided for driving other circuits or devices. The "working" version of the circuit eliminates the indicator LED's and their driver IC's, and uses a much smaller PC board. However, it retains the eight out- puts and all other circuitry, and is therefore more suitable for building into a motorized model or other project. Voice recognition The basic elements of voice or speech recognition have been known for a number of years. Human speech consists of phonemes, which are the small- est individual units of sound that make up words and sentences. The "ah" sound in "father," the "t" sound in "top," and the "rr" sound in "radio" are all examples of phonemes. Any word in a par- ticular language can be created by stringing together the proper sequence of phonemes and spaces of silence. Not all lan- guages use the same phoneme sets; English, for example, lacks a glottal stop and the click found in many African languages. Electronic voice recognition consists of analyzing the ar- rangement of phonemes in a spo- ken sequence and matching them against stored patterns or templates to determine the word or phrase. There are many varia- tions in the actual processes used for each of the three steps: storing the patterns, analysis, and matching. However, the basic techniques used for voice recognition can be loosely grouped into four categories. In speaker-dependent voice recognition., the intended user of . the recognition device "trains" it } by carefully pronouncing the list i of recognized words, several i CO o Z O LU o D < IT times each. The system creates detailed templates, or patterns of that speaker pronouncing those words, and stores them. The sys- tem will have a very high success rate in recognizing that speaker pronouncing those words, but it will be less able (if at all) to recog- nize another speaker saying the same words — and, of course, it will only recognize those specific words that it has been trained to recognize. A discrete-word speech recog- nizer can only decode speech when it is a series of separately spoken words. It could not un- derstand "Move the cursor to field one," but the sequence "Goto" (pause) "Field" (pause) "One" would be understood. Speaker-dependent discrete- word recognition systems are the most common types in use. A speaker-dependent con- nected-word recognition device must be trained to recognize each different speaker's pronun- ciation. However, more powerful analysis capabilities allow decod- ing of words strung together in a long phrase or sentence. This type of recognizer could decode "Move the cursor to field one," but is typically costly and com- plex. The success rates are also typically lower than for speaker- dependent discrete-word recog- nition systems. A much more difficult process is to decode the speech of a vari- ety of speakers. No two people pronounce words in quite the same way. When analyzed elec- tronically and graphically, varia- tions, even with very similar- sounding speakers, are quite GROUND-I 1 i l Id >- RESET "l tV-l 2 1 1 19KM0OE I I. + V-I 3 i ■ 18 J- GROUND V x XTAL-( 4 i I17MV X X EXW.H 5 i 1 16 r +V VCP200 ^j' sbouwmVi i' 15V LIGHTS ,1. -I. aubioin-ij; i Hi- LEFT TORN GOIMMfiHV" I'ljV RESET I v r RiRirRi§FrnYKrt>f?H' 9 ^ 1 12 r- STOP V HEVEBSf(N<5fSUREHja; Ml J- SLOW L - J LED INDICATORS/* HiGH-GAtN CLIPPING AMP COMPARATOR FIG. 2— BLOCK DIAGRAM of the voice-recognition circuit. The VCP2Q0 contains almost all of the required circuitry, and needs only a power supply, microphone, and high-gain amplifier with clipping comparator output for operation. The LED indicators and their drivers are optional. marked. That natural variation makes it very difficult for a sys- tem to recognize, with a high suc- cess rate, the same words spoken by different people. Speaker-independent voice recognition follows the principle that all speakers have certain similarities in their pronuncia- tion. For example, nearly all speakers pronounce the word "stop" with the following sim- ilarities: an initial sibilant ('sss'), a short plosive (T), a soft vowel ('ah'), and a final plosive Cp'). By matching selected phonemes and allowing for variation in the matching algorithm, the same words can be identified and de- coded from a variety of speakers. PARTS LIST FIG. 1— THE PINOUT OF THE VCP200. The output pins 8, 9, and 10 respond to dif- ferent words or phrases, depending on the operating mode selected. All resistors are 1 A-watt, 5% R1— 2200 ohms R2— 1000 ohms R3— 10,000 ohms R4, R7— 470,000 ohms R5— 11,000 ohms R6, R8— 5600 ohms R9— 4700 ohms R10— 10 megohms R11— 100,000 ohms R1 2-1 9-^70 ohms Capacitors C1— 0.22 jjlF, 16-volts, tantalum C2, C3, C12— 0.01 ^F disc C3— 39 pF disc C5— 4.7 pF disc C6-C6— 0.1 u.F disc C9, C10— 27 pF disc C11— 10 U.F 16-volt tantalum Semiconductors D1-D8 — red light-emitting diode (optional, see text) IC1— LM324A quad op-amp IC2— LM7805T 5-volt, 1.5-amp voltage regulator IC3— VCP200 speaker-independent word recognizer IC4, IC5— CD4011B quad nand gate (optional, see text) Other components JU1 — switch or jumper (see text) MIC1 — electret microphone XTAL1— 10 MHz crystal Miscellaneous: PC board (See text), bus wire, SPST power switch, SPDT mode switch, normally open pushbutton reset switch, 9-volt bat- tery or 8-15 volt DC power supply, 9-volt battery clip, three 14-pin IC sockets, one 20-pin IC socket, mounting screws and standoffs, 4-40 x 3 /e-inch screw and nut, hookup wire, solder, aluminum sheet for heatsink. Note: The VCP200 may be avail- able from Radio Shack (it has been discontinued but many stores still stock them) as part number 276-1308, or from VCPI, 1 Willings Place, Monterey, CA 93940, for $14.95 postpaid. 50 R19 47012 -MV-O BUCKETS ■GROUND = 166 1 llddV CO g z o cr i- u LU The drawbacks to speaker- in- dependent systems are that the number of separately recogniz- able words is limited, the recog- nition success rate is generally lower than that of speaker-depen- dent systems, and the system can be easily fooled by similar words. For example, "swap," "stat," "spat," "spot," and "spit" all have phoneme patterns that are sim- ilar to "stop." Most speaker-inde- pendent word recognition sys- tems will be unable to dis- tinguish between those words. Most dedicated voice- or word- recognition systems are speaker- independent discrete-word types. Although they have some severe limitations, they excel at simple voice-control tasks involv- ing a few carefully chosen words and phrases. The VCP200 is a speaker-independent discrete- word recognizer. The dream of designers, con- trol engineers, and science-fic- tion writers is a system that can recognize normal, connected speech from a wide variety of speakers. Despite much effort, no such system yet exists. The first successful "natural speech" recognizer will almost certainly demand the resources of a dedi- cated supercomputer to handle the massive analysis and com- putational steps required. How- ever, keep in mind that speech synthesis, now achieved with single dedicated IC's, also once required a full-sized computer. The VCP200 The VCP200 speaker- indepen- dent word recognizer, from Voice Control Products. Inc. (VCPI), is a mask-programmed Motorola 6804 microprocessor. The 6804 is a 20-pin device that imple- ments most of the standard 6800-series instruction set and capabilities, and contains one kilobyte of onboard ROM. Al- though an EPROM version is available for user development, production devices such as the VCP200 use a ROM that is mask- programmed at the time of man- ufacture with the appropriate data and control information. That approach, used for many computationally-based special- purpose devices, is a viable alter- native to designing a costly sin- gle-purpose chip from scratch. The VCP200S ROM contains a phoneme analysis and matching program using a proprietary al- gorithm. The algorithm analyzes a modified voice input signal and matches it against a selection of stored word-recognition tem- plates to identify twelve different words and short phrases: Yes, No, On, Off, Lights, Left Turn, Re- set, Stop, Slow Reverse, Turn Right, and Go. The chip is switchable between On/Off and Command modes. In the On/Off mode, it recognizes only the two word pairs On/Off and Yes/No. In the Command mode, it recognizes the other eight words and phrases. A sepa- rate output for each word is pro- vided, which is latched low when the word is successfully recog- nized. If the VCP200 cannot find a close match among its word templates, all eight outputs are left high. The VCP200 is virtually a stand-alone device, requiring only a 10-MHz crystal and four passive components for opera- tion. The only outside circuitry that is required is a special input amplifier, built from a common op-amp, that delivers a sharply clipped and amplified voice sig- nal. That quasi-digital signal can be easily analyzed by the micro- processor. The VCP200's biggest disad- vantage is the limited and non- expandable word list. However, considering that the chip is inex- pensive and easy to use, that lim- itation shouldn't bother anyone who is interested in exploring voice-recognition technology without making a heavy invest- ment of time or money. Unfortunately for experimen- ters, VCPI regards the VCP200s program and word-recognition algorithm as proprietary infor- mation. Few details are available, and VCPI's literature and docu- mentation discusses the tech- nology only in general terms. An interesting exercise for the ad- vanced experimenter would be attempting to work out the es- sential elements of the al- gorithm, using standard refer- ence information on voice recog- nition, digital analysis of analog signals, and pattern matching. The pinout of the VCP200 is shown in Fig. 1. The chip is powered from a single-ended 5- volt supply, which connects to pins 3, 6. and 1, and must pro- vide about 15 milliamps. Its os- cillator crystal connects to pins 4 and 5, each of which must also be tied to ground via 27-pF capaci- tors to complete and stabilize the oscillator tank circuit. Pins 2, 16, 17, and 18 of the VCP200 are not used in a stan- dard application. They are spe- cial-purpose control pins that are usually tied to +V or ground, and are connected that way on our PC board. Generally, these pins may be ignored, as they are normally used to set the VCP200 into vari- ous test and special-application modes that are not useful to the experimenter. The reset input, pin 20, is held high for normal operation and brought low for a reset. A simple resistor-capacitor pair connected to this pin will cause a power-on reset. The VCP200 can be man- ually reset by strobing the pin low at any time, by holding it low, you can safely disable the chip's oper- ation. Pin 19 is the operation-mode select input. When this pin is high, the chip is set to the Yes/No mode, and only Yes/Off (pin 9), No/On (pin 8), and Not Sure (pin 10), which indicates a recogni- tion failure, are active. When pin 19 is low. the VCP200 is placed in the Command mode, and all eight outputs are active, with each corresponding to a different recognized word or phrase. The VCP200s audio input, pin 7, requires an input signal that is either quiescent, or swings past the digital logic thresholds. That requirement translates into a highly amplified, sharply clipped signal that is "shut off when it is not of sufficient amplitude. Such a signal is easy to achieve with a standard op-amp, as we'll see. Finally, pins 8 through 15 are the VCP200 s outputs. During or after a reset (pin 20 brought or held low), all eight outputs are held high. When the chip suc- cessfully recognizes a word or phrase in Command mode, the corresponding output will be latched low until the next recog- nition attempt occurs. If the VCP200 fails to find a match to an input signal, all eight outputs will remain high. In the Yes/No mode, during or after a reset, pins 8, 9, and 10 (as well as the five unused outputs, pins 11—15) 52 will be high. Some recognition failures in the Yes/No mode can also cause all three active outputs to go high. The circuit As said earlier, there are two versions of the circuit. A block diagram of the experimenter's version is shown in Fig. 2. The circuit contains a power supply, an input amplifier and com- parator, the VCP200, and output drivers. The power supply is quite conventional, using 1C2, an LM7805T 5-volt regulator. The input amplifier is not a conventional design; the output signal, if it were connected to a speaker, would be quite distorted and unlistenable. The purpose of the two-stage amplifier, with its overall gain of about 800, is to increase the microphone signal to a useful level. The output is then passed to a comparator that keeps the final output signal ei- ther quiescent (flat-line) or switching between the supply limits — a quasi-digital signal. The output of the amplifier is passed to the VCP200s audio in- put, where the signal can then be analyzed. The VCP200S eight outputs are made available, via current- limiting resistors, so that exter- nal interface circuits may be add- ed to control motors, solenoids, and other active elements. Eight LED's are added to give a quick and easy indication of the cir- cuit's response. The LED's are driven by CMOS buffers, which isolate the LED's from the out- puts, preventing either the in- dicators or any outlying circuits from interfering with each other. Figure 3 shows the complete schematic for the experimenter's version of the voice-recognition project. Note that the schematic of the working version would be exactly the same, except for the omission of LED's 1-8 and IC4 and IC5. Power for the voltage regulator, IC2, can be from 7.5 to 15 volts. Since the circuit draws only about 22 milliamps peak, a 9-volt battery is a good choice. Capaci- tors CIO and Cll filter and sta- bilize the regulator's output. The signal from the electret mi- crophone, MIC1, is coupled to the LM324A op-amp, IC1, through CI. The amplifier uses ICl-a and ICl-b to form a two-stage device that amplifies the microphone signals with a gain of 500-800. That transforms the weak input signal (under 5 mV) to a signal that swings from one output lim- it to the other, often with consid- erable clipping. The amplifier has a restricted bandwidth, with a more or less fiat response from about 500 Hz to 9 kHz. Signals under 300 Hz and over 15 kHz are sharply at- tenuated. That covers the FIG. 4— AMPLIFIER (a) AND COMPARATOR (b) output waveforms. The comparator con- verts the amplifier signal into a clipped, quasi-digital 4-volt p-p signal only when the amplitude of the amplifier's signal exceeds the comparator threshold. 5: w o z o IE F o W D < VCP200*s input range of 300 to 5500 Hz, with some additional headroom for the easily-lost higher frequencies. The ampli- fier's characteristics are impor- tant, because the quality of the input signal largely determines how well the voice recognizer will work. To keep the VCP200's input quiet, unless a signal of suffi- cient strength is present, and to ensure a sharply clipped signal, the output of the amplifier is passed to a comparator, ICl-c. (The fourth op-amp on the LM324A, ICl-d is not used, and its pins are left unconnected.) The comparator's output re- mains steady unless the input signal swings past its threshold. Input signals of less than 2.5 volts peak-to-peak will be ig- nored. However, all signals stron- ger than that will cause the comparator's output to swing from limit to limit, or about 4 volts peak-to-peak, which is within one-half volt of each sup- ply rail. A comparison of the am- plifier and comparator output signals is shown in Fig. 4. Since the LM324A is operated from a single-ended supply, a "false ground" or offset voltage must be provided. The offset, along with the comparator threshold voltage, is provided by the voltage divider string R5-R8- R9. The amplifier offset is pro- vided by the upper junction, and the comparator threshold by the lower; C6 and C7 stabilize those voltages. That design forces the center voltage of the op-amp's output signal to be separated by a volt or so from the comparator's threshold, and is the key to cor- rect operation. Adjusting the di- vider string is one of the ways that the circuit's performance can be modified. The output of the comparator is then routed to pin 7 of the VCP200. The 10-MHz crystal, XTAL1, provides the chip's mas- ter clock frequencies, with the oscillator tank circuit completed and stabilized by C9 and CIO. To provide a power- on reset, the RC pair Rll and C8 hold the VCP200's reset input low for a few milliseconds after power comes on. As C8 charges through Rll. the reset pin is brought high, re- setting the VCP200. The VCP200's mode input, pin + 5V OUT LIGHTS LED1 <— o LEFT TURN ^£02 'f— O RESET ,LED3 /*— O STOP ■,LED4 A-OSLOW "4— O REVERSE LED6 'A- «TURN RIGHT r LED7 '/L — oGO LED8 — °GR0UND OUT FIG. 5— THE COMPONENT LAYOUT for the experimenter's version. The "working" ver- sion parts layout is the same except for the smaller PC board that omits the LEO's and their drivers IC4 and IC5. FIG. 6— THE VOICE-RECOGNITION CIRCUIT offers eight voice-activated outputs for experimenting with voice control. 19, is controlled by setting JUL On the PC board, JU1 is actually three pads which may be con- nected to an SPDT switch, or simply jumpered. However, jum- pering is not recommended; a switch will make it easier to ex- periment with both operation modes. The eight outputs, pins 8 through 15, are left open for the experimenter to use as necessary. Since the outputs are active-low, they can sink about 10 mA and source somewhat less. That is sufficient enough to drive logic devices and transistor drivers. If high-current devices such as re- lays or motors are to be driven, a buffer/driver must be used. To prevent damage to the VCP200 from an accidental overload of an output, 470-ohm current-limit- ing resistors (R12— R19) are pro- vided. They limit the output current to about 9.5 mA, even under worst-case conditions. The eight LED indicators, LED1-LED8, are driven from CMOS drivers IC4 and IC5, which are CD4011B quad nand gates. However, several other common chips could be sub- stituted here, among them the CD4001B quad nor gate and the CD4093B quad nand Schmitt trigger. Construction Foil patterns are provided for both versions. Although a PC board is recommended, perfo- rated construction board and point-to-point wiring could also be used. If you use point-to-point construction, be sure and keep all wiring, especially in the area of the input amplifier, short. The very high gain of the amp will cause it to pick up and amplify electrical noise if excessively long connecting wires are used. You should use sockets for all the IC's to make them easier to replace if necessary. If you are going to build the experimenter's version of the project, follow the parts-place- ment diagram shown in Fig. 5. If you are going to build the smaller "working" version, simply use the smaller foil pattern; parts placement is the same as the larger version, except that the 54 LED's and their drivers. IC4 and IC5, are left out. On both, keep the wire jumpers and resistors close to the board. Insert the disc capacitors so that their bodies are seated against the board, but don't chip the dielectric material. Be careful to observe the polarity on the two electrolytic capaci- tors, CI and CI 1. The voltage regulator, IC2, re- quires special mounting. The middle lead should be bent about 0.1 inch farther from the body than the two side leads, and all three bends should be made so that the regulator's mounting hole lines up with the hole in the board (see the photo in Fig. 6 for details.) If you are going to be using the project by itself, with no outlying devices powered from the board, no heatsink is needed for the regulator. If you are going to be powering other devices from the regulator that will in- crease the load to more than 100 milliamps, a heatsink should be added to the regulator. A flat alu- minum stock heatsink can be bent into a shallow "U" shape and installed under the regulator. Be- cause there is no space for a large heatsink, the current drawn from the regulator should be lim- ited to no more than 250 mA even when using as large a heatsink as possible. For most experimenters, mounting MIC1 directly to the board will be adequate. In some cases, though, it may be better to mount the microphone remotely. In that case, light-gauge shielded cable should be used to connect the microphone to the board. Electret microphones are polar- ized, so be sure the positive ter- minal is connected to the pad that leads to CI and Rl. If you like, the eight LED in- dicators can be mounted re- motely with a length of ribbon cable. If you mount them on the board, be sure to position them all at an even height. How you finish the remaining steps de- pends on how you want to use the board. For display and experi- mentation, you'll want the input and outputs of the circuit easily accessible with test points. Oth- erwise you can hardwire driver circuits and the like directly to the board. In the prototype, the PC board and power switch are mounted to Command Pronunciation Comments Yes yeSSS Both of these words should be longer than "No" or "On," with emphasis on the final sibilant. Oft awFFF No no These words should be kept very short. You'll find that almost any short, sharp sound will be interpreted as one of these words. On on Go go Lights LytSSS Emphasize L and S. Left Turn LeFFFT Turn Emphasize F and the two T's, and separate words clearly. Reset rESSSeTT A difficult word for the VCP200 to recognize. Emphasize the first E, S, and final T Stop SSSTawPP Emphasize T and P. Keep short, but longer than "Go". Slow SSSIoh Emphasize S and vowel. Reverse rEverSSS Another difficult word for the VCP200. Emphasize first E and final sibilant, but do not separate syllables. Turn Right Turn-ryT Emphasize Ts and slur words together slightly. a thick plastic base using spacers and screws, and the battery clip is secured by smaller screws. Al- though the prototype has no re- set switch and is strapped into the Command mode, you can easily add the controls. Just use a slightly larger mounting base and mount the switches in the same manner. If you are using the working version, and will be using it as a part of a complete project or more complex setup, use your judgment as to mount- ing the board. Testing When you have the board (ei- ther style) finished, leave the IC's out of their sockets and connect the power terminals to 9^15 volts DC. Then check for +5 volts DC at pin 3 of the regulator, pin 4 of IC1. pin 2 or 3 of IC3, and (with the experimenter's unit only) pin 14ofIC4andIC5. Disconnect power, insert IC1, and then connect power again. Check for an AC voltage at pin 7 of IC1. It should vary with the level of sound up to about 2 volts peak. Check the voltage at pin 14 of IC1. When the sound level is high enough, a 2-volt signal should be present. If the com- parator is functioning correctly, pin 14 should switch between no signal and a 2-volt AC signal, with nothing in between. If you're using an oscilloscope, look for a 0—4 volt signal at pin 7, and a or 4 volt clipped signal at pin 14. Once the board has passed these tests, remove the power and insert the rest of the IC's. When you reconnect power, all LED's should remain off, or if you're using a board without the indicators, all of the outputs should be high. Say "Go. " The ap- propriate LED should light (or the output will go low). Try the other phrases to make other LED's light. Don't worry if the cir- cuit doesn't seem to respond well — it takes a little practice to speak the words and phrases clearly enough for the VCP200 to understand. Table 1 explains how to pronounce the words so that the VCP200 will understand them. Modifications The gain of the amplifier may be adjusted by changing the val- ue of R4, R7, or both. Adjusting R7 is preferred. The higher the resistor values, the higher the gain of the amplifier. Lowering the gain will lessen the circuit's > sensitivity to background noise, Ig but will require the operator to f= speak rather loudly and directly £ into the microphone. Raising the 2 55 9 SELECT FIG. 7— BASIC POWER DRIVER CIRCUIT for interfacing the project to motors, lamps, or other high-current devices. The relay must have a 5-volt coil, but can have any arrangement of contacts suitable for the application. gain will allow softer speaking from a greater distance, but at the expense of greater sensitivity to noise. The frequency response of the amplifier is about 300 to 9000 Hz. Since the VCP200 responds to frequencies from 300 to 5500 Hz, reducing the upper cutoff point of the amplifier to 6000 or 7000 Hz would probably make it less sensitive to noise. If you are familiar with op-amp circuit de- sign, a good way to improve the project would be with a high-pre- cision bandpass amplifier. It should have a nearly flat re- sponse from 500 to 6000 Hz, with a sharp rolloff (third-order or better) at each end. The flatter the bandpass response and the sharper the cutoff points, the better the overall performance is likely to be. Higher frequencies are more sharply attenuated by distance and may need extra boost (actually less cut) in order for the VCP200 to successfully decode them. The comparator threshold is set by the lower output of the re- sistor divider string R5-R8-R9. Since the artificial ground level or offset voltage of the amplifier is set by the upper output of the same string, some care is needed when adjusting either voltage so as not to disturb the other. The amplifier offset should be kept as close to +0.5 volts (or 2.5 volts) as possible, to ensure proper am- plifier operation (i.e., balanced clipping of the signal). Thus, the series value of R8 and R9 should always be the same as that of R5. If the comparator threshold is very close to the amplifier offset, very low-level sounds will be "dig- itized" by the comparator and make their way to the VCP200's input. That would permit better TOGGLED,- OUTPUT +5V* -CQ4011B to RESET OUT V-tCD4011B 5 V4CD4OT1B ■# reset ! 4 .ii^rQ_JMf 'Ljh VT«'„-, n „ reset TO rpiN WP200 PIN 20\ FIG. 8— TOGGLED, LATCHING interface circuit. The output switches states on successive occur rencesoftheassociated voice command. FIG. 9— THIS CONTROL CIRCUIT allows the project to be latched into forward or reverse motion while permitting other voice commands to be processed. -3 r /t INCHES- HERE'S THE FOIL PATTERN for the experimenter's version of the circuit, which includes the indicator LED's. FIG. 10— A "SUICIDE" RESET CIRCUIT permits the voice-recognition circuit to be reset via voice command. operation over distance or with softly-speaking users, but would make the unit prone to inter- ference from noise. If the com- parator threshold is set further from the amplifier offset, noise will be rejected but louder speech or shorter-range operation will be required. For extensive experi- conttnued on page 70 56 THE ADVANTAGES OF REGULATED switching power supplies are too great to Ignore. These versatile supplies are well known for their high efficiency, cool operation, small size, and the ability to work with a wider range of input volt- ages than their linear counter- parts. Once limited to high- power or high-efficiency applica- tions, they are now finding their way into low-power, low-cost con- sumer goods. Because the control elements used in switching regulators are always either fully on or fully off, they have low power consump- tion and require little or no heat sinking. Small-size high-fre- quency transformers can be used, and, since regulation effi- ciency is not too affected by the input-to-output voltage differen- tial, it's possible to handle two-to- one input variations, such as 115/230 volt operation. Switching regulators do, how- ever, have disadvantages. A pri- mary drawback is their complex- ity, and therefore circuit cost. They also exhibit failure modes not seen in simple linear reg- ulators, and can radiate substan- tial electromagnetic interference (EMI) if not properly designed. Fortunately, a number of IC's have been developed that not only include most of the complex circuitry, but also overcome com- mon failure modes, which we'D look at later. Now we'll concen- trate on basics. Switching regulator basics Let's begin by reviewing a lin- ear (non-switching) regulator as shown in Fig. 1. Op-Amp IC1 compares feedback voltage V FB to reference voltage V REF . If V FB is too high, Ql's base voltage de- creases or, if it's too low, the base voltage increases, until V FB equals V REF . At equilibrium, Ql's emitter-collector voltage drop equals V UNREG - V REG . The transistor power dissipation, W, equals CVunreg-Vreo) x *■ A well-designed linear reg- ulator can provide excellent reg- ulation and transient response, low noise and ripple, and com- plete freedom from EMI. It does, however, waste power in the reg- ulating transistor, especially at high load currents. Regulating widely-varying inputs is a prob- lem because power dissipation increases as V UNREG goes up. Now let's look at how pulse- width modulation (PWM) con- trols voltage. As shown in Fig. 2, Ql is alternately turned on and off by the PWM control circuitry. The output is R-C filtered to ob- tain a DC average. If Ql is always off, the output voltage will be zero; if it is always on, the output will equal the input. The output voltage will be proportional to the duty cycle, which is the ratio of the "on" time to the total period. Vqut = Vin x (Tok/Ttotal) =V| N xDuty Cycle If Ql were ideal {no voltage drop in the on state) it would dissipate no power. Actual voltage drop var- ies depending on the transistor and the current level, but is usu- ally less than or equal to one volt. (Power FET's respond better in high-current applications.) Power dissipation still occurs in filter resistor Rl , reducing overall circuit efficiency Practical circuits To reduce resistive power losses, switching regulators use L-C, rather than R-C filters, as shown in Fig. 3. When Ql is on, V UNREG is applied to inductor LI and Dl is reverse-biased. The in- ductive current supplies the load and also charges output capaci- tor C2. When Ql turns off, the induc- tive current continues, flowing through Dl. The diode conducts until the inductor current re- duces to zero, or until Ql is again turned on, whichever occurs Inside SWITCHING POWER SUPPLIES HARRY L. TRIETLEY Learn the basics of switching regulators — the heart of switching power supplies- M u z pc o LU o c < FIG. 1— A LINEAR REGULATOR CONTROLS conduction through a regulating transistor to maintain the required output. Ql's off time is not long enough to reduce the current to zero, it will build even higher during the next on cycle, raising the output even higher. Conversely, if the on time becomes very short, the cir- cuit will act as if the input is con- nected directly to the output, and the output will equal the input (no boost). Mathematically, ignor- ing losses, Vreg =Vunreg/{1 - Duty Cycle). As with the buck converter, feedback is used to control the duty cycle for the desired output. One thing to keep in mind when using a boost converter is that its input current can be much high- er than its output current. FIG. 2— PULSE WIDTH MODULATION (PWM) produces an output proportional to the duty cycle. first. Inductor LI smooths the on-off current from Ql, while C2 further evens out the load volt- age. Complex switching-reg- ulator control circuitry varies the duty cycle to keep the feedback voltage equal to the reference voltage. A circuit of that type is commonly called a "buck" con- verter because it bucks, or re- duces, the input voltage. The output current is greater than the input current because the inductive current continues while Ql is turned off. For an ide- al circuit, the regulator would be 100% efficient, meaning (V REO x I OUT ) equals (V UNREG x I IN . In reality, however, circuit efficiency is typically about 80%. Figure 4 shows a flyback, or "boost" converter. It operates much like a TV flyback, but with feedback added to control the output voltage. When Ql is on, an inductive current builds up in LI. When Ql turns off, the induc- tive current flows through diode Dl. into C2 and the load. Since LI is supplying current, its output side is positive and its voltage adds to, or "boosts" V UNREG . The output voltage is, therefore, greater than the input voltage. The longer Ql is on, the higher the inductive current becomes. If The control circuitry Let's get inside the control IC a little. To keep things simple, we'll leave out protective and problem- correcting circuitry and focus on the basic pulse-width control. Figure 5 shows a typical circuit consisting of a clock (R-C os- cillator), comparator, reference, error amplifier, flip-flop, output gate, and switching transistor. The error amplifier's output is proportional to the difference be- tween the reference and feedback voltages. IC's vary greatly in de- tail, but generally use the princi- ples discussed below. At the beginning of each clock cycle a pulse resets the flip-flop, turning Ql on, and the oscillator begins along the positive slope of the ramp. When the ramp ex- ceeds the error signal, the com- parator's output goes high, setting the flip-flop and turning Ql off. The higher the error sig- nal, the longer Ql remains on. The output voltage dividers in Figs. 3 and 4 are designed so that the feedback voltage. V FB , equals the reference voltage, V REF , when the output reaches the de- sired level. If the output voltage goes too high, the error voltage decreases, reducing the duty cy- D1 j t IMVAC SWITCHING REGULATOR CONTROL CIRCUITRY L1 m:£ R2<: -i C2s; + Vn, AoNS FIG. 3— MOST SWITCHING REGULATORS use L-C filtering to eliminate resistive power losses. + V,M-n =fe L1 + ^C1 o— ^3 D1 RI SWITCHING REGULATOR CONTROL CIRCUITRY T R2' C2; rn +v„, ^uwo'f 'UHM6 '1 -{DUTY CYCLE} FIG. 4— A FLYBACK, OR input. BOOST," converter produces an output voltage higher than Its 58 ■Manual •w^yn R1 R-C OSCILLATOR 5sC1 +V M +5V LA. CLOCK RAMP ERROR VOLTAGE REFERENCE AND REGULATOR X l_t\ *> p-|>-^ERROR V re O- Q1 COMPARATOR CLOCK JLT ERROR AMP COMPARATOR [~~i | \_ a ITLTT output _n — n — r T1T2 T1T2 FIG. 5 — THIS CIRCUIT SHOWS the heart of a pulse-width modulator, without its protective and problem-correcting circuitry. FIG. G — A "BUCK-BOOST" CONVERTER produces a negative output from a positive input. FIG. 7— IN A TRANSFORMER-COUPLED flyback converter a separate winding on the transformer allows output regulation while still maintaining input/output isolation. cle and, therefore, the output. On the other hand, if the output volt- age drops, the error voltage and duty cycle increases until the output returns to its design val- ue. Now let's examine some more circuits and explore the dif- ferences between them. A voltage inverter Figure 6 shows a "buck -boost" converter which produces a negative output from a positive input. That circuit is similar to the circuit shown in Fig. 3. In Fig. 6, however, the right side of the inductor is connected to com- mon and the feedback network is different. The name "buck- boost" comes from the fact that the output can be lower or higher than the input. When Ql turns on, the input voltage is applied to inductor LI , causing an increasing current. Unlike the "buck" regulator, that current does not flow through the load while Ql is on. When Ql turns off, the inductive current continues, flowing through Dl and charging output capacitor C2 with a negative voltage. The current continues until it re- duces to zero, or until Ql again turns on, whichever comes first. The longer the duty cycle, the higher the inductive current and, therefore, the higher the output voltage. The regulated output, V REG . ignoring power losses, is - Vunreq x [(Duty Cycle)/1 - {Duty Cycle)]. Transformer coupling Up to this point, the circuits we've seen don't provide input- to-output isolation. They also suffer a second, less obvious shortcomings — an unbalanced current in the inductor, which produces a DC flux in the core, leading to saturation at lower power levels. Unbalanced opera- tion of the power inductor re- quires larger, gapped cores to support the necessary magnetic fields. On the other hand, those circuits are simpler and use fewer components than the ones we're about to examine. Primary-to-secondary isolation can be accomplished by using a transformer as shown in Fig. 3. High-power line-frequency transformers, though, are bulky and expensive. Since the pulse- width-modulation circuitry runs at high frequencies, it's often more efficient to transformer- couple and rectify its output pulses. Figure 7 shows a simple trans- former-coupled flyback convert- er. The control circuit is the same as in Fig. 4, but the inductor has been replaced with a flyback transformer. The on-time pri- mary current builds up flux, which collapses when Ql turns off. The collapsing field induces voltages in both secondaries, one of which produces the output while the other provides an iso- lated feedback voltage. Although this is a simple circuit, it still pro- duces a net DC current in the transformer. The output voltage, V REO , can be expressed as Vunreg x N x [(Duty cycle)/1-(Duty Cycle}] where N equals the transformer turns ratio. A circuit known as a "forward > 33 59 converter" [Fig. 8} is better suited for high-power supplies. When Ql turns on, the unregulated in- put is applied to the first winding and Dl is reversed-biased. The primary current begins to rise and a voltage is induced in the output winding. Output current flows through D2 and LI. When Ql turns off, the collaps- ing field induces reverse-polarity voltages in all three windings. Since Ql is off and D3 is reverse- biased, their windings carry no current. Current flows through the middle winding, known as a "reset" winding, and D2 becomes forward-biased. During that time the inductive current in LI flows through D3. As long as D2 conducts, the re- set winding is connected to the input voltage. That condition continues until the current re- duces to zero. There are two ad- vantages of that circuit: the average primary current is zero, and the winding voltages are well-defined during the off portion of the cycle. A smaller core can be used, and high flyback voltages are not a prob- lem. To maintain zero average current, the on time must never be longer than the off time, so the duty cycle is limited to 50%. The output voltage, V REG , is Vunreg xNx Duty Cycle. The output and input grounds are tied together in Fig. 8 for proper feedback voltage. To pro- vide input-to-output isolation it is also necessary to isolate the feedback. We will discuss ways to do that in a future issue. Finally, the push-pull circuit shown in Fig. 9 is similar to a DC- to-DC inverter, but with pulse- width modulation added. That circuit provides the best efficien- cy in high-power converters. The primary winding's center o z Q tr. F o UJ _i LU Q D < tap is connected to V L . Tran- sistors Ql and Q2 are under the control of the switching regulator circuit. They are alternately pulsed on, connecting first one end of the primary and then the other to common. Raising the duty cycle increases the average applied voltage, and therefore the output voltage. Each transistor's duty cycle is limited to 50%. (we must not have both turned on at once), but since there are two, the overall duty cycle can ap- proach 100%. Again, isolated FIG. 8 — IN A FORWARD CONVERTER direct-coupled feedback provides optimum regula- tion, but no input-output isolation. o — * +V U flLJl SWITCHING REGULATOR CONTROL CIRCUITRY HULL FIG. 9— A PUSH-PULL CONVERTER, similar to a DC-DC inverter but with pulse-width modulation, provides best efficiency for high-power supplies. v ffi o- ERROR AMP RAMP -^VN^-S ToT -TLTL Q V™„2 J i i 1 i i n n r ON OFF ON OFF FIG. 10— ADDING A STEERING FLIP-FLOP and a pair of nor gates produces a pulse-width modulator with push-pull output. feedback is needed if input-to- output isolation is required. The output voltage, V REG ,is the same as the forward converter Vunreg x N x Duty Cycle. Controlling the two transistors requires a change in the control circuitry, so let's examine the IC again. Figure 10 is similar to Fig. 5, with output-steering circuitry added. The clock pulses toggle the steering flip-flop. At the start of each cycle, when the com- parator's output is low, the nor gate whose q input is low will turn on. The other remains off until the start of the next cycle toggles the flip-flop. Figure 10 60 C AVERAGE CURRENT CONTINUOUS CURRENT, a -»T C AVERAGE CURRENT DISCONTINUOUS CURRENT. 6 FIG. 11— CONTINUOUS (a) and discon- tinuous (b) inductor current. I PRIMARY WINDING RESISTANCE V/y SECONDARY WINDING RESISTANCE — -VVV O PRIMARY LEAKAGE INDUCTANCE "IDEAL" v oiff TRANSFORMER viAAj o SECONDARY LEAKAGE INDUCTANCE FIG. 12— A TRANSFORMER MODEL showing winding resistances and leakage inductances. Stray capacitances and core losses are not Included, shows the timing waveforms. An IC of that type is very ver- satile, and can be used in all the circuits we have examined. Sin- gle-output control is imple- mented by simply paralleling Ql and Q2, For forward converters, the 50% duty cycle limitation is easily provided by using only Ql as the drive. Which one should I use? We have examined six cir- cuits — three without transfor- mers (buck, boost, and buck- boost) and three with (flyback, forward, and push-pull). Let's take some time now to compare the advantages and drawbacks of those techniques. Transformer-coupled circuits are more flexible in stepping volt- ages up and down, and can pro- vide input-to-output isolation. Negative outputs require only re- versal of the rectifier diodes, and multiple secondaries can be used to provide multiple output volt- ages. The main drawback of transformer-coupled circuits is the cos^. and the size of the trans- former itself. The choice among transfor- merless circuits is often simple. Use the buck circuit (Fig. 3) for voltage stepdown, where the out- put is lower than the input; the boost circuit (Fig. 4) for step-up; or the buck-boost circuit (Fig. 6) for polarity inversion. All three use the same number of compo- nents and have similar control requirements. One performance difference is worth noting: the buck converter tends to have lower output ripple because the inductor aids in filtering the out- put current. When designing those circuits you must take into account the peak voltages and currents in the .transistors and diodes to ensure that those components operate within their specified ratings. The buck converter operates with lower peak currents than the others, due to the filtering action of the inductor. Peak currents in the transistor and diode equal the output currents, while the peak voltages equal the input voltages. In a boost converter, peak tran- sistor and diode currents, I PK , equal Ioutx(VoutA/| N ). The peak voltage equals the out- put voltage. In a buck-boost supply, the peak current, I PK , equals lour^-Duty Cycle. The peak voltage equals the sum of the input and output voltages. One drawback of the boost cir- cuit should be mentioned. Be- cause the input is directly connected to the output through the inductor and diode, it is not possible to use short-circuit lim- iting in the circuit. The flyback converter (Fig. 7) retains the advantages (cost and simplicity) and drawbacks {high peak currents, high ripple, and DC coil current) of a transformer- coupled circuit. It's the best choice when a simple, low-cost circuit is needed to regulate up to tens of watts. Peak switch cur- rent, I PK , of a flvback converter is l OUT x(NxV PN + V OUT )/V IN Forward and push-pull con- verters (Figs 8. and 9) are best for regulating higher power, whether isolation is needed or not. Both require extra wind- ings, inductors and circuitry, but both provide the transformer with a balanced current. Also, both produce lower output-ripple current than the flyback. As a re- sult, smaller transformers and filter components may be used. Input peak and output ripple cur- rents are higher in the forward converter, because its duty cycle is limited to under 50%. Both are well-suited for use at tens to hun- dreds of watts, but for highest power (especially above 1000 watts) a push-pull converter should be chosen. Discontinuous operation For most efficient operation in any of the circuits we've dis- cussed, the inductor current should flow contintiously; other- wise, ripple currents will in- crease and regulation may suffer. That effect is most apparent in transformerless circuits. Those circuits depend on energy stored during the on cycle being trans- ferred to the output when the transistor turns off. If the induc- tance is too low, all of its stored energy will be transferred to the output before the transistor turns back on. Continuous operation results when the peak-to-peak ripple current in the inductor is less than twice the inductor's load, or DC average current; in other words, when the inductance is large enough that the negative excursion of its ripple never reaches zero. Figure 11-a shows continuous operation, while Fig. 11-5 shows discontinuous opera- tion. For example, in the buck converter of Fig. 3, continuous operation means that inductor current is always flowing into the load. Maintaining continuous operation in a switching reg- ulator is usually a simple matter of choosing a large enough in- ductor. Discontinuous operation nor- mally occurs at low output loads, when the DC current is so low that the negative excursion can- not be kept above zero. For- tunately, discontinuous opera- tion is not disastrous, only annoying, if it only happens un- der abnormally light loading. A decrease in regulation and in- crease in ripple are the usual re- sult. 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The design of switch- ing-regulator magnetics is a complex subject which we can- not cover completely in this arti- cle. We will, however, briefly dis- cuss some of the more important concepts such as physical size, construction, ratings, and leak- age inductance. Our first consideration is size. The inductance of a choke or transformer must be large enough to keep ripple current within acceptable bounds and to maintain continuous operation. The core must not saturate at its highest current. Some of the de- sign tradeoffs include size, power, filtering and transient re- sponse. Larger inductances and cores provide highest power and lowest ripple, but with slow re- covery from transients. Cores should be a ferrite mate- rial or powdered iron — lamina- tions are not suitable for high- frequency operation. Toroidal cores minimize EMI because they tend to be self-shielding. Air gaps usually are needed to prevent sat- uration with unbalanced DC cur- rents. The gap reduces the core's permeability, requiring larger structures to achieve the re- quired inductance. When buying an inductor or transformer make sure it is rated for the frequencies and DC currents you will be ap- plying to it. The affect of satura- tion could be the destruction of switching transistors, control IC's or other components in the circuit. An approximate inductance value can be calculated from basic inductor theory. Inductor current increases linearly with time when a DC voltage is applied AI = ExT/L where A I is the change in current in amps, E is the applied voltage in volts, T is time in seconds, and L is inductance in henrys. If your circuit operates at a fre- quency in hertz equal to 1/T, the maximum voltage across the in- ductor is E and you want to de- sign for a peak-to-peak ripple current of AI, the inductor value can be found by L = E/2(AI)f It's best to start with a little ex- tra inductance, then optimize it experimentally. Inductor values in the medium to high microhen- ries are common. Switching regulators operate at high frequencies and fast risetimes, and switching tran- sients can produce peak voltages higher than the values given ear- lier. Transformers with switched primary currents are the main source of that problem. A major source of primary-side spikes is leakage inductance. Figure 12 shows a transformer model including winding resis- tances and leakage inductances. (Winding capacitances are not shown.) In an ideal transformer there would be perfect magnetic coupling between the primary and secondary. A voltage spike could not appear across the pri- mary unless a proportional spike was seen on the secondary. If there was a load across the sec- ondary, especially when a capaci- tor is used, spikes would not occur. In reality, a small portion of the flux produced by the primary is not coupled to the secondary. Electrically, that means that a small part of the primary's induc- tance is not coupled to the sec- ondary, and vice-versa. Trans- former leakage inductance is represented in Fig. 12. Switched primary currents produce spikes in the leakage inductance. Leakage inductance can be minimized, but not completely eliminated, by proper trans- former design. The best ap- proach is a bifilar winding, where the primary and secondary are wound together, their wires inter- mixed in the same coil. That may not be possible in transformers requiring high primary-to-sec- ondary breakdown voltages. It's sometimes necessary to add Zener diodes and/or small capac- itors, across the primary to pro- tect the switching transistors and diodes. In the second and final part of this article, we'll look at some more protective and safeguard circuitry provided in switching regulator IC's. We'll also examine some IC families with which you should be familiar. R-E PEOPLE TEND TO THINK OF ROBOTS as complex, expensive creatures designed to execute boring, re- petitive tasks, day in and day out, for eternity. And sure, there are industrial robots that work like that. But not all robots are boring drudges. In fact, it's possible to build an inexpensive experimen- tal robot that wilt perform non- repetitive tasks under program control. Our robot is called Ken. He's easy to build and fun to program: and In so doing you can learn a great deal about important Is- sues in robotics. Ken is a two- wheeled, battery-powered, free- roaming, obstacle-avoiding robot. Ken s intelligence consists of a single-component micro- controller; his propulsion is pro- vided by two stepper motors driven by a single high-current IC driver. All together, Ken's elec- trical system consists of eleven electronic and five electro-me- chanical devices. (By the way. Ken is not an abbreviation for anything in particular; the au- thor simply thought that it would be rather nice to give the robot some personality) Theory of operation Ken was designed to move free- ly on a smooth, flat surface. Using the specified stepper motors (or others with a higher torque rating], Ken rolls easily on a tile floor or tight-napped car- pet. He has a low center of gravity and is equipped with two op- positely opposed wheels, each driven by a stepper motor. The edge of Ken's smooth plastic case serves as the third point of con- tact with the floor. Ken's schematic is shown In Fig. 1. All of his nomadic habits are dictated by IC1, an 8748H mi- crocontroller, that is packaged in a standard 0.6-inch, 40-pin package. In addition to the CPU, the 8748H includes 1024 bytes of EPROM, 64 bytes of RAM, 24 bits of I/O, a crystal oscillator, and an eight-bit timer/counter. For our purposes, we configured IC1 for one 8-bit output port to drive IC2, and one 8-bit input port to monitor motion-sensing switch- es S2 and S3. Note that Ken doesn't take advantage of all the 8748HS resources, and that leaves you with lots of pos- sibilities for expansion. BUILD ^ THE STEPPER-MOTOR nUBUT FREDEADY Ken, the friendly robot, is fashioned around an 8748 microcontroller. Build him for less than $100! Crystal XTAL1 drives the 8748HS internal oscillator; the value of XTAL1 may range any- where from 1 to 11 MHz. Capaci- tors C3 and C4 help to start and stabilize the oscillator. However, the author has found that the 8748H will operate reliably with- out them. Capacitor CI is used to reset IC1. Under program control, eight of ICl's I/O ports drive IC2, a ULN2803 high-voltage, high-cur- rent octal Darlington transistor array. The ULN2803 can drive a total of eight 500-mA loads with as much as 50-volts DC per load. The ULN2803 has built-in clamp diodes that help suppress step- per-motor noise. ULN2803's can be "stacked" by wiring several of them in parallel. Although doing so was unnecessary for our pro- totype, you may wish to if you use high-current steppers. Ken's steppers have 12- volt windings that draw approximately 300 mA per winding. Stepper motor theory A stepper motor converts elec- trical pulses Into rotational motion. As shown in Fig. 2, a typ- ical stepper motor consists of a permanent-magnet (PMJ motor built around two stator cups, with each cup surrounding a separate stator winding. The stator cups form pole pairs that are mechanically displaced by l A a pole pitch. However, the stator- cup winding pairs displace each other by only !A a pole pitch. When the stator windings are en- ergized, the pole pairs are ener- gized in alternation, thus creat- ing North and South magnetic poles. The PM rotor is magne- tized, so it aligns on the pole pairs provided by the stator cups. By changing the polarity of the voltage applied to the stator windings, it is possible to force the rotor to move l A a pole pitch. The change in polarity causes op- posite poles to attract and like poles to repel, thereby compelling > X 63 en g z c X t- o the PM rotor to realign. That real- ignment is the source of the out- put shaft's rotational motion. Ken's motors contain 12 pole pairs per stator-winding section, and thus take 48 steps for a com- plete revolution (7.5 degrees/ step). Alternately energizing each winding in a predetermined pat- tern moves the rotor continually in one direction. You can run the pattern backward to reverse rotor motion. Speed of rotation is de- termined by the rate at which the pattern runs. The standard pat- tern for Ken's stepper motors is shown in Fig. 3. Now that we know what drives the steppers, let's take a look .at how to drive them. Stepper-motor driver circuit Figure 4 shows the schematic of a unipolar stepper motor with associated drive transistors. Note that four coils are shown. Each winding consists of two coils wound on the same bobbin per stator half. (By contrast. Fig. 2 depicts a two-coil or "bipolar" stepper.) You can reverse stator flux in a bipolar motor by reversing the current in the coil. However, doing so requires twice as many drive transistors as a unipolar motor. In addition, as Fig. 5 shows, you must ensure that the circuit does not turn on a series- connected pair of transistors (Ql and Q2, for example), which would in turn short the power supply. By contrast, unipolar flux may be reversed by energizing either one coil or the other using a sin- gle-ended power supply. In addi- tion, using unipolar motors eliminates the need for extra drive transistors and eliminates the possibility of accidentally shorting the power supply. As stated earlier, steppers con- vert electrical pulses into rota- tional motion. One excellent source of electrical pulses is the output port of our 8748H micro- controller. If one were to equate "on" in Fig. 3 to a binary "1," and "off to a binary "0," and then apply the pattern to the driver transistors via the micro- controller's output port, the out- put shaft of the stepper motor would rotate. It's that simple. Un- fortunately, we don't have space 26 JO C2 .1 X1W.1=L; 27pF 27pF*' r C1 IpF 35V •45V P21 * 22 IC1 8T4BH XTA1 P20 XTA2 P17 P16 P15 P14 P13 PI2 P11 P10 5j_ -a a +12V o- •f — <-£,<>- S2 LEFT MOTION SWITCH V°c sr POWER IC3 7B05 H'iT-l' — ± 12V I C5 .1(iF' S3 RIGHT 4r MOTION SWITCH + 12V 34 1 ho 33 2 32 3 31 4 30 5 29 6 28 7 27 8 1?. IC2 ULN2B03 17 1G BLK ORG ^JLWLr-»-xJiii^ RIGHT MOTOR URN + 1ZV RED YEL RED 15 14 13 VEL 12 BRN II -vM& y f \JLflJL/- LEFT MOTOR ORG RED BLK RED FIG. 1— SCHEMATIC DIAGRAM. Intelligence is provided by IC1, an 6748 single-chip microcontroller. COIL A r C01LB + Ol )±S ^^ \!7 r: a \ o o r: sj \ vy r: \ r STATOR CUP A -» ROTOR XJ f STATOR CUP B FIG. 2— MECHANICAL DIAGRAM showing the parts of a bipolar stepper motor. to print the software listing here, but it's available on the RE-BBS (516-293-2283, 300/1200, 8N1, filename: ROBOT.ASM), and I from the source mentioned in the parts tist. FIG. 7— MOUNT ALL PARTS as shown here. If you use motors other than those specified, F you may have to experiment to determine which windings connect to which outputs of ^ IC2. 2 65 -5.4* -H CIRCUIT BOARD, MOUNTS HERE h-.6G"-H .20"— H h / \ /^ .ir-* h- M" PLASTIC END PANELS TOP VIEW FIG, 8— TOP VIEW. Remove the front arid rear ends of the case and glue end panels in place as shown. FRONT FIG. 9— LEFT SIDE VIEW. The right side is a mirror image. DOME LID DOME SUPPORT BAR "^ -0.125" 00 BRASS TUBE \ SQUARE \ r 'A* x 5" BRASS STRIP (2) 3 /ia" \ SQUARE BRASS CHANNEL 4" BRASS V CHANNEL (2) O z o EC — Q LU 6 □ < EC FIG. 10— THE COVER SUPPORT is built from brass channels. Exact dimensions will vary, depending on your cover. force, we find the result to be 0.473 pounds of linear force, still more than enough. Enough of this theoretical stuff, let's roll up our sleeves and build Ken. Electronic assembly A single-sided PC board allows for convenient construction. Foil patterns are provided, although an etched and drilled board is available. FIG. 11— KEN IS SHOWN HERE with his cover removed. Using the parts layout shown in Fig. 7 as a guide, mount all electronic components. Put a thin coat of heatsink compound on the top and bottom surfaces of IC2, and then slide on a heat- sink. Double-check the parts ori- entation and all solder joints before continuing. Next connect the stepper motors and microswltches. If you use surplus steppers and cannot determine which winding is which, check the advertisement for an ohms-per-winding value. You can then determine which wires represent independent windings by measuring resis- tance between various pairs of wires. After you determine which pairs correspond to windings, use trial and error to determine how they should be connected to the PC board. With only four windings, it shouldn't take long to find the right combination. Mechanical assembly Ken is built from plastic and brass, although you can use any materials you like. However, If you deviate from our specifica- tions, be sure to recalculate the amount of force required to move your robot and select steppers ac- cordingly. The body of the prototype con- sists of a plastic instrument case obtained from a local electronics retailer. That case was selected because it was wide enough to hold both the steppers and Bl, a gel cell. We cut off the ends of the case to form a U-shaped channel, and later glued clear red acrylic panels along slots designed for mounting a PC board. You can glue the panels in place using 66 [gffg I 66000 ......... ^~ 60000060000000 _2_o_ 1000000000000000 u*o~ -3 13 /16 INCHES- FOIL PATTERN for Ken's controller board. modeling cement. The thickness of the panels matches the width of the brass U-channels, dis- cussed below. Begin assembly by forming and drilling the main body, as shown in Figs. 8 and 9. Next, mount the stepper motors and install the wheels. The wheels may come from inexpensive toys; the author has seen suitable wheels on toys costing less than four dollars. Be sure that the wheels fit the stepper-motor shafts, and that the diameter of the wheels is large enough to raise Ken's body off the floor. Also, use brass or aluminum tub- ing to shim the stepper-motor shafts, if necessary. In addition, be sure that you can screw or glue some sort of cam surface to the hubs of the wheels to sense wheel motion. The author used over- sized set screws for cams. After mounting the stepper motors and wheels, fit the mo- tion-sensing switches, SI and S2. Using an ohmmeter to mea- sure continuity, adjust each mi- cros witch to actuate on the high point of the cam surface. Cover construction We built a transparent cover for the prototype. (The cover is op- tional.) We used a lettuce crisper from a local discount department store. First we removed the bot- tom half of the body, leaving a ring about two inches high. We attached the ring to the domed top of the crisper with a couple of pop rivets. We also custom-built a brass support bar that fits inside the assembly and allows it to rest on Ken's body. Feel free to im- provise on our design, but re- member to keep the weight down. Also, to provide access to the battery, the cover should not be permanently mounted to the body. As shown in Fig. 10, the all- brass cover support consists of a long support bar, two thin strips that hold the bar in the lip of the dome, two "U" channels that slip on the end plates of the body, and a vertical tube for stability. Use solder for all mechanical connec- tions. Figure 11 shows Ken with his cover in place. Final assembly After checking all connections, connect a 12-volt gel cell to Ken and power him up. Both wheels should turn in the same direc- tion until you stop one (or both). In either case, Ken should reverse both wheels and perform a turn by rotating the wheels in op- posite directions. After perform- ing the turn sequence. Ken should again rotate both wheels in the same direction. Also, Ken should turn in opposite direc- tions, depending on which wheel you stop. Ken in the big world It's time for Ken's maiden voy- age. Just turn him on and let him go. As soon as he runs into some- thing, he should attempt to change direction. Ken is always very busy, and cats love him. Ken is a simple robot, but the principles of operation are identi- cal to those of large (and expen- sive!) robots. You can take the basic building blocks presented here and expand on them to build a large and sophisticated device. Have fun, and remember, all of Ken's "intelligence" is under software control. If you don't like the way something works — change it! r-e Earn Your B.S. Degree in ELECTRONICS or COMPUTERS By Studying at Home Grantham College of Engineering, now in our 41st year, is highly ex- perienced in "distance education" — teaching by correspondence — through printed materials, computer materials, fax, and phone. No commuting to class. Study at your own pace, while continuing on your present job. Learn from easy-to- understand but complete and thorough lesson materials, with additional help from our instructors. Our Computer B.S. Degree Pro- gram includes courses in the BASIC, PASCAL, and C languages — as well Assembly Language, MS DOS, CADD, and more. Our Electronics B.S. Degree Pro- gram includes courses in Solid-State Circuit Analysis and Design, Control Systems, Robotics, Analog/ Digital Com- munications, and more. An important part of being pre- pared to move up is holding the right college degree, and the absolutely neces- sary part is knowing your field. Grantham can help you both ways — to learn more and to earn your degree in the process. Write or phone for our free catalog. Toll free, 1-800-955-2527, or see mailing address below. Accredited by the Accrediting Commission of the National Home Study Council GRANTHAM College of Engineering 1 Grantham College Road Slidell, LA 70460 § 67 EARN YOUR B.S.E.E. 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COOK'S INSTITUTE OF ELECTRONICS ENGINEERING : 42S1 CYPRESS DRIVE • JACKSON, MISSISSIPPI 39212 CIRCLE 58 ON FREE INFORMATION CARD JAN CRYSTALS pur reliable source for a world of crystal clear communication i i -■■■■ | t£t£ 68 • Commercial Two-Way • Microprocessors • Amateur/ Experimental • Scanners/ Monitors/Pagers • Satellite-Telemetry • Plus custom applications EXPEDITED ORDER SERVICE! FOR FREE CATALOG, CALL OR WRITE; JAN CRYSTALS P.O. Box 06017 Ft. Myers, FL 33906 (813) 936-2397 TOLL FREE 1-800-526-9825 FAX ORDERS: 1-813-936-3750 VISA POWER INVERTER continued from page 44 IC1 PIN1 (CLOCKI- NG PIN 3 Jnnhjvi-Hh-rL- IC2 PIN 2 AC OUTPUT (LINE TO LINE) FIG. 3— THE TIMING RELATIONSHIPS In the inverter. When IC2 pin 3 goes high, the output of buffer IC1-c (pin 8) is high. That reverse biases D1 and allows the error amp signal to reach Q1, Q2. and Q3, At the same time, IC2 pin 4 is low, which causes the output of buffer ICl-d to be low. That grounds the gates of 04, Q5, and 06 thereby turning them off. the FET's should be insulated. Parts placement isn't critical except for the 100-ohm gate re- sistors. They prevent VHF oscilla- tions and should be placed within half an inch of the FET's. Just make sure that everything is securely mounted inside the cab- inet to prevent shorting. Also, the prototypes metal cabinet has had several half-inch holes drilled in the bottom and rear for ventilation. Power up To safely test the inverter, it should really be operated with a FIG. 4— IN THE PROTOTYPE, the FET's are not insulated from the heatsinks because the heatsinks are isolated from ground and all other circuitry. 1-amp current-limited power supply If you don't have one, sim- ply connect it to approximately 12-volts DC, and keep a look out for smoke or sudden failures. Connect an oscilloscope ground to chassis ground and the probe to the junction of D3 and D6 ; you will see an alternat- ing DC signal. The frequency should be between 70 and 90 Hz. If it isn't you can adjust it by changing the value of R27. Ad- just trimmer R17 for 180-voIts peak. If you use a DVM or a VOM. connect it across the inverter's AC outlet, and adjust R17 for 120- volts AC. Now it's time for a full-power test. You will need a 12.6 volt, 10- amp power supply or a car bat- tery. A 120-volt, 40-watt light bulb makes a good load for test- ing. With a 12.6-volt input, the inverter will deliver 150 volts peak, which will read about 105 volts on a DVM. With a 14.2-volt input, which is what an auto- mobile alternator supplies, the output will be 115-volts AC. We're sure you'll find many uses for your inverter at home or on the road. 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I The SPEC-COM Journal P.O. Box 1002, Dubuque, IA 52004 (319)557-6791 MC.'V ISA -Sin added, VCP200 cont. from page 56 mentation, try using a 10K potentiometer in place of R8, and a IK resistor in place of R9. 10K the tap of the po- tentiometer as the out- put to the comparator. That way, a steady am- plifier offset is main- tained while allowing considerable adjust- ment of the com- parator threshold. Interfacing The outputs of the VCP200 can only source and sink small amounts of current and must be protected from reverse EMF and noise. Fortunately, a variety of interface cir- cuits can be devised. One simple power driv- er is shown in Fig. 7. The desired output from VCP200 is con- nected to the SELECT input, where it drives the base of the PNP transistor. The tran- sistor supplies power to the relay which can have any type and ar- rangement of contacts necessary. In some cases, it may be handy to be able to toggle an output device on and off. The cir- cuit in Fig. 8 permits just that. Upon power-up, the output of the flip flop will be low. When an ac- tive low from the VCP200 is ap- plied to the select input, the output will latch high. The next active low will cause the flip flop output to drop low again. A more sophisticated output circuit is shown in Fig. 9. On power-up, both outputs will be high. When the go output of the VCP200 is selected, that output will be latched low. If the VCP20Os reverse output is se- lected, the go out output will be toggled high and reverse out will latch low. If a stop signal from the VCP200 is received, both flip flop outputs will be toggled high. The circuit in Fig. 10 allows a complete reset of the voice recog- nition circuit and any outlying f Uj X uwlmlmlfl WtHtIt It Wti j THE "WORKING" VERSION of Ihe project is made on this board, which omits the LED's and their drivers. circuitry with a voice command. When the reset output of the VCP200 is selected, the monosta- ble multivibrator, composed of the first two gates and the RC junction, produces a pulse that is routed back to the VCP200's reset pin, pin 20. That forces a reset of the voice-recognition circuit. The pulse can be tapped by another CMOS gate (either inverting, as shown, or noninverting, or both), and used to reset outlying circuitry Given the imperfect nature of voice control, this cir- cuit is recommended. You now have some basic building blocks on which you can base your voice-control experi- ments. Keep in mind that, even though the command words un- derstood by the VCP-200 are best suited for controlling a robot, they can be used to control vir- tually anything. R-E EMEinamEi New hackable project ideas, infrared people detectors, "i it-package" battery testers, another contest, and machine-shop resources. DON LANCASTER I have recently gone over dozens of my successful hardware hack- ing projects and hundreds of my failures over several decades, trying to fathom what worked and what did not. I'm convinced that one of the key underlying secrets is watching for and then profiting from paradigm shifts. A paradigm is just the way people perceive things to be. Any paradigm shift occurs whenever someone up- sets the apple cart — which would happen whenever any vastly new or different way of doing things be- comes obvious or when something becomes much cheaper or more widely available. In general, hardware hacking does not do well in the "business as usual" times. It is only when some sudden and dramatic change or other funda- mental shift in values takes place that new opportunities emerge. Some ancient personal examples of paradigm shifts: The low-cost sil- icon controlled rectifiers that blew the thyratron out of the saddle and opened up psychedelic lighting; tri- acs that made light dimmers and power-tool speed controls possible; and RTL digital integrated circuits that revolutionized counting and dig- ital logic. Other examples include cheap nickel-a-bit shift registers and character generators that permitted my TV Typewriter (Radio-Elec- tronics, September 1973) to be the opening round fired in the personal- computer revolution. Let's not leave out price reductions in CMOS chips: the 6502; the KIM-1 microcomputer; de-mathifying those pseudorandom sequence gener- ators; the Apple lie; the monumental new stupidities now hopelessly crip- pling all of traditional publishing: CD ROM; and that insanely great PostScript language. Your key hacker opportunity: The people who are doing the shifting of the paradigm usually do not have the slightest idea what they are doing, since they will be always rearwardly focusing on the way things were. When a paradigm shifts, all sorts of new hardware hacking opportunities immediately open up. Especially if you are able to view things from a different perspective — or if you can reduce the cost of something by 50:1, changing the market to some- thing totally foreign (and totally mis- understood) by the way things were. If there has not been any recent paradigm shift, the chances are it will be tricky to come up with a useful product. For instance, there has not been one iota of improvement in any of those Peltier thermoelectric cool- ing modules in the past two decades, owing to the inherently low efficiency of those devices. Any hacking work done the "old way" here is probably a total waste of time. Similarly, if useful computer touch screens would ever have done any- thing, they should have taken off years ago. The bottom line is that people do not like to touch computer screens, and trying to convince them otherwise is probably fruitless. The same goes for Dvorak or other "im- proved" keyboards. The whole point of this Hardware Hacker series is to try and identify paradigm shifts that you can work with and profit from. We have seen many recent examples. They include anything and everything involving PostScript, magnetic refrigeration, wavelet theory, desktop finishing, vis- ible laser diodes, direct toner printed NEED HELP? Phone or write your Hardware Hacker questions directly to: Don Lancaster Synergetics Box 809 Thatcher, AZ 85552 (602) 428-4073 circuits, and book-on-demand pub- lishing, to name just a few. For some others, see my Eminently Hackable Emerging Tech- nologies story found in that July-Au- gust 1990 Midnight Engineering. And down-loadable as GEnie PSRT file #116 EMERGOP.TXT. The opposite side of the paradigm shift is the sucker bet. That is any thoroughly plowed ground that, for one reason or another, just did not and will not ever hack it. Ratholes into which countless corporate dollars have been foolishly dumped with no visible results, or results having the exact opposite of the intended effect. Obvious sucker bets include the UNIX language, the NeXT computer, TrueType, or most anything involving 7e/erexf, Infrared people detectors Street prices on the infrared peo- ple detectors are dropping very fast, so now is a good time to review how those electronic devices work. Sev- eral important uses now include bur- glar alarms and occupancy sensors. Any object not at a temperature of absolute zero will radiate heat. At lower temperatures, a black body ra- diation pattern will be produced. A human will normally radiate at 98 degrees Fahrenheit, compared to other objects in the room which will typically radiate at a 70-degree range. A human body is a very weak radiator which becomes even more so when compared against the am- bient. Figure 1 is a typical curve of human body radiation in a normal room. As you can see, the radiated energy is centered on the eight-mi- crometer range in the far infrared. One sensor which is capable of detecting the radiation from a person is known as a pyroelecthc infrared detector. They are available at a very low cost from the Arnperex division of ^ Phillips, among others. As we'll see 2 shortly, Arnperex has lots of good ap _* notes and data sheets available. <§ 71 A pyroelectric infrared detector consists of one or two detectors that, in turn, input to a field effect tran- sistor CFET) source follower. The basic detector is a capacitor, across which several hundred microvolts DC will be generated in the presence of a warm and non-moving human body. The detectors are often used in side- by-side differential pairs that are im- aged slightly differently. They then tend to cancel out stationary sources. One very big gotcha here: The sen- sors are basically a capacitor so they cannot indefinitely produce a DC out- put. Even the tiny bias current of a FET's gate is enough to flatten any long-term DC level. Thus, the pyroelectric infrared detector is able to respond only to changing levels' of infrared energy. Stationary sources are ignored. So, the trick is to make the infrared signals appear to be rapidly chang- ing. One obvious way is to have the person run through the beam. That can produce a usable transient. But something better is clearly needed. The traditional method was to chop the beam by putting a bladed fan in RADIATION DIFFERENCE IN WATTS PER SQUARE CM PER MICROMETER 0004 - CO o z o tr i- o o Q < rx NEW FROM 1 DON LANCASTER HARDWARE HACKER STUFF Hardware Hacker Reprints II or III 24.50 Incredible Secret Money Machine 13.50 CMOS Cookbook 24.50 TTL Cookbook 19.50 Active Filter Cookbook 19.50 Micro Cookbook vol 1 or II 19.50 Lancaster Classics Library 109.50 Enhancing your Apple 1 or i! 17.50 AppleWriler Cookbook 19.50 Apple Assembly Cookbook 21.50 Absolute Reset He & lie 19.50 Enhance 1 or II Companion Disk 19.50 AppleWriler CB or Assy CB Disk 24.50 POSTSCRIPT STUFF Ask The Guru Reprints 1, II or III 24.50 LaserWriter Secrets (lie Mac PC) 29.50 PostScript Snow & Tell 39.50 Intro to PostScript VHS Video 39.50 PostScript Beginner Stuff 39.50 PostScript Cookbook (Adobe) 16.50 PostScript Ret. Manual (Adobe) 22.50 PostScript Program Design (Adobe) 22.50 Type 1 Font Format (Adobe) 15.50 LaserWriter Reference (Apple) 19.50 Real World Postscript (Roth) 22.50 PostScript Visual Approach (Smith) 22.50 Thinking in PostScript (Reid) 22.50 The Whole Works (ail PostScript) 299.50 FREE VOICE HELPLINE VISA MC 0.0003 - 0.OOO2 - 0.0001 WAVELENGTH IN MICROMETERS FIG. 1— THE FAR INFRARED SIGNATURE of a 98-degree F person in a 70-degree room environment. Note that these are extremely weak power levels. SYNERGETICS Box 809-RE Thatcher, AZ 85S52 (602) 428-4073 front of it. That would input an infrared square wave that represents the dif- ference between the body and fan blade temperatures. By knowing how fast those blades whipped past you, you could also do a synchronous de- modulation that would increase your detection sensitivity. But moving fan blades and synchronous detectors are expensive. Somehow you have to gather the infrared energy from your area and concentrate it on the detector sur- face. While mirrors are one solution, a plastic Fresnei lens is better. Now for the tricky part. Instead of making the lens operate uniformly over the surveyed area, it is purposely striped so that there are "strong" and "weak" sensing areas. A typical lens pattern is shown in Fig. 2. As the person walks through the beam or otherwise moves, they travel be- tween the strong and weak lens areas, creating more of a varying sig- nal than they would otherwise. Figure 3 shows you a schematic of a simple people detector using a dual-element pyroelectric detector and a quad op-amp. The Fresnei lens has strong and weak areas that alter the strength of the infrared signature of a moving person. That is sensed by the detector and routed to a x 600 AC amplifier. The combined frequen- cy response of the detector and the amplifier is in the 0.3- to 5-Hertz range. That is usually optimum for most people movements. The output of your amplifier is routed to a window detector or dual comparator. The detector will output a signal on any sudden change in the infrared signature. Usually, the output of the window detector is routed to a counter of some sort to minimize false alarms. In security applications, an alarm output is created. For the occupancy detectors, the lights are quickly turned on, and then left on for a se- lected number of minutes. A Fifteen- minute delay is often optimum for people who are usually sitting at a desk or bench. Each time they move, the on time gets extended. One commercial source of ready- to-go occupancy sensors is Leviton. They fit in an ordinary power outlet. Occupancy sensors can dramatically reduce the power bills in most larger commercial buildings. Another alternative to pyroelectric detectors is the Kynar Piezo Film from Atochem (formerly Pennwalt). While less sensitive to infrared and much more tuned in to motion or vibration, this approach can let you integrate your lens and sensor into one single thin assembly. While the electronics involved in people detection are both simple and straightforward, your mirror or lens design is not. Thus, you are better off using some already developed and debugged commercial lens/detector combination than trying to work one up from scratch. 72 VCV Fresnel lens and detector FIG. 2— SINCE PRYOELECTRIC INFRARED SENSORS are capacitors, they cannot hold a DC or stationary level. To emphasize changes in motion, special Fresnel lenses are often used that have "hot" and "cold" areas as shown here. +5V Fresna Lens 39K 10K 39K 'iHVM-f-^WA-t-VW^ *5V OUTPUT 47K +5V 100K 100K 330K 4.7(1 FIG. 3— A "PEOPLE DETECTOR" intended for use as an office lighting control. The output goes high on any motion detection that would increase or decrease the input far infrared signature. Pyro electric infrared detectors tor movement sensing. Technical publication #1 34, 1 384 Remote level sensing using pyroelectric infrared detectors. Technical publication #135, I960 Low cost remote sensing radiometer using the RPY89 infrared detector. Technical publication #138. 19B0 Low cost automatic light switching using passive infrared sensors. Technical publication #147 February 1985 Ceramic pyroelectric infrared sensors and their applications. Technical publication #163 Passive infrared (PIR) intruder alarms. Technical publication #213 April 1986 Movement sensing using a multi-element fresnel lens. Amperex ap note, November 1988- KRXIOdual element pyroelectric infrared sensor. Data sheet, September 1988. KRX11 dual element pyroelectric infrared sensor. Data sheet, September 1 988 RPW100 dual element pyroelectric infrared sensor. Data sheet, September 1 988 Fresnel lens data sheet and explanatory notes. Phillips data sheet, April 1 986 FIG. 4— AMPEREX AP NOTES and data sheets on pyroelectric infrared detectors. Figure 4 lists some of the more readable Amperex ap-notes and data sheets on people detecting. It is a very good starting point for picking up all the infrared sensing basics. Battery testers As all of you long-time Hardware Hackers know, I am very much a fan of elegant simplicity, or any way to do very much with very little. Those Duracell folks have finally reduced battery testing to an elegantly sim- plistic minimum. Just in case you haven't noticed, there's now a free battery tester built into their battery packaging. An incredibly sophisti- cated one, and obviously cheap. Flashlight cells do not often fail suddenly. Instead, because of cell po- larization and other effects, their in- ternal resistance slowly increases. That, in turn, drops the cell's voltage under load, eventually to the point where they can no longer be used. To test a flashlight cell, just place a power resistor across it that repre- sents a fairly heavy load for that size cell. Wait several seconds. Then measure the battery's open-circuit voltage. In the Duracell package, there is a pair of printed contacts with a printed power resistor between them. Around three ohms for the AA-stze alkaline cell. The resistor gets noticeably hot when you connect your cell to it. Now for that elegantly simple part. As Fig. 5 shows us, the printed re- sistor is not uniform. Instead it forms a wedge shape. The narrow portion of the wedge at the bottom will have a higher resistance per unit length and thus will get hotter than the upper, wider part. Thus, this particular re- sistor will set up a temperature gra- dient that is hottest at the bottom and coolest at the very top. How hot? Well, that all depends on how much current your cell puts out under load. Power equals the current squared times the total resistance. A thin liquid-crystal coating gets placed on the reverse side of the re- sistor. It's the same stuff used in clinical and desk thermometers. At a certain transition temperature, the liquid crystal will turn a bright green. Below that temperature it will remain black, and above it a dark gray. The more the available current un- der load, the higher the green spot on the display. So. a "good" cell will 73 o z o o D < IE Green liquid crystal spot will move up and down following the critical temperature set by the quality of the test cell. FIG. 5— THE LOAD RESISTOR in the Duracell battery tester is wedge shaped so that it gets hotter per unit length at the bottom than at the top. A liquid-crystal coating changes color at a critical temperature, moving a green indicating spot up with a strong cell and down with a weak one. NAMES AND NUMBERS Atochem (formerly Pennwalt) Box 799 Valley Forge, PA 19482 (215) 666-3500 CIRCLE 301 ON FREE INFORMATION CARD Burr-Brown 6730 South Tucson Blvd Tucson, AZ 85706 (602) 746-1111 CIRCLE 302 ON FREE INFORMATION CARD Circuits Assembly 500 Howard Street San Francisco, CA 94105 (415) 397-1881 CIRCLE 303 ON FREE INFORMATION CARD Duracell Berkshire Industrial Park Bethel, CT 06801 CtRCLE 304 ON FREE INFORMATION CARD Exet 2150 Commerce Drive San Jose, CA 95131 (408) 432-0500 CIRCLE 305 ON FREE INFORMATION CARD GEnie 401 North Washington Street Rockville, MD 20850 (800) 638-9636 CIRCLE 306 ON FREE INFORMATION CARD Lev iton 59-25 Little Neck Pkwy Little Neck, NY 11362 (800) 824-3005 CIRCLE 307 ON FREE INFORMATION CARD Midnight Engineering 111 East Drake Road, Ste 7041 Fort Collins, CO 80525 (303) 491-9092 CIRCLE 308 ON FREE INFORMATION CARD Motion Control 800 Roosevelt Rd, Ste E-408 Glen Ellyn, IL 60137 (708) 469-3373 CIRCLE 309 ON FREE INFORMATION CARD Newark Electronics 228 East Lake Street Addison, IL 60101 (708) 941-7200 CIRCLE 310 ON FREE INFORMATION CARD NSRA News PO Box 3724 Ann Arbor, Ml 48106 (313) 994-6088 CIRCLE 311 ON FREE INFORMATION CARD Phi Hips/Ampere x 100 Providence Pike Slatersville, Rl 02876 (401) 762-3800 CIRCLE 312 ON FREE INFORMATION CARD Phillips/Signetics 45 George Washington Hwy Smithfield, Rl 02917 (401) 232-0500 CIRCLE 313 ON FREE INFORMATION CARD Professional Glass Consultants 1409 Kuehner Drive, Ste 494 Si mi Valley, CA 93063 (805) 527-5375 CIRCLE 314 ON FREE INFORMATION CARD Synergetics Box 809 Thatcher, AZ 85552 (602) 428-4073 CIRCLE 315 ON FREE INFORMATION CARD Teltone 10801 120th Avenue NE Kirkland, WA 98033 (800) 426-3926 CIRCLE 316 Of FREE INFORMATION CARD have a "high" green spot, and a "bad" cell might have a "low" green spot, or perhaps none at all. The results surely change with the ambient temperature and the size of the cell being tested, but they as- sume you are testing your cells at room temperature, and that the cell being tested is the type and size pro- vided in the package. Basically what you have here is a three-cent to 500 DC milliamrneter. What other uses can you come up with for this great new concept? Elegant simplicity contest What else is elegantly simple? For sure the P-38 can opener, which I rank as far and away the most outstanding invention of the twentieth century, bar none. Such frivolities as automobiles, televisions, computers, aircraft, and even Hostess Twinkies should pale by comparison. Especially when you factor in bang-for-the-buck, reliability first costs, complexity, and the end- user performance. For this month's contest, just tell me about something in the P-38 can opener class that really needs further developing. We'll have a dozen or so Incredible Secret Money Machine book prizes, along with an all-ex- pense-paid (FOB Thatcher, AZ) tinaja quest for two going to the best entry of all. To get you thinking about elegant simplicity, here are some ideas: We need a sleeping-bag zipper with a "snowplow" snoot on it that doesn't jam itself on the pulled-in material at 4 am. We need a boot shoelace that works, especially in oddball lengths. Sorely needed are a line of gourmet truth-in-advertising foods, such as cream of mushroom soup with mush- rooms, or pork and beans with pork. And Detroit is at long last wiseing up to the fact that putting a plain old pin through the differential dramatically improves the handling in mud or snow. Finally, it goes without saying that we just gotta have a stainless steel potato chip, since the real ones break on the third of fourth time into the dip. Yes. you could use a P-38, but... Let's have your thoughts on ele- gant simplicity, electronic or other- wise. As usual, be certain to send all of your written entries directly to me here at Synergetics, rather than sending them to Radio-Elec- tronics editorial. 74 MACHINE SHOP RESOURCES American Machinist 826 Broadway, 4th Floor New York, NY 10003 (212) 477-6420 CIRCLE 317 ON FREE INFORMATION CARD Bordens Surplus Center 10156 West O Street Lincoln, NE 68501 (800) 228-3407 CIRCLE 318 ON FREE INFORMATION CARD C&H Sales PO Box 5356 Pasadena, CA 91117 (800) 325-9465 CIRCLE 319 ON FREE INFORMATION CARD Design News 44 Cook Street, Suite 210 Denver, CO 80206 (303) 388-4511 CIRCLE 320 ON FREE INFORMATION CARD Enco 5000 West Bloomingdale Ave Chicago, IL 60639 (800) 621-4148 CIRCLE 321 ON FREE INFORMATION CARD Home Shop Machinist 2779 Aero Park Drive Traverse City, Ml 49684 (800) 447-7367 CIRCLE 322 ON FREE INFORMATION CARD Industrial Equipment News Five Penn Plaza, 8th Floor New York, NY 10001 (212) 629-1500 CIRCLE 323 ON FREE INFORMATION CARD Industrial Products Bulletin PO Box 650 Morris Plains, NJ 07950 (201) 292-5100 CIRCLE 324 ON FREE INFORMATION CARD J&L Industrial Supply 31800 Industrial Drive Livonia, Ml 48150 (800) 521-9520 CIRCLE 325 ON FREE INFORMATION CARD KSC Tools 6300 18-Mile Road Sterling Heights, Ml 48314 (800) 521-1740 CIRCLE 326 ON FREE INFORMATION CARD Kepro 630 Axminister Drive Fenton, MO 63026 (314) 343-1630 CIRCLE 327 ON FREE INFORMATION CARD Lindsay Publications PO Box 583 Manteno, IL 60950 (815) 468-3668 CIRCLE 328 ON FREE INFORMATION CARD Machine Design 1100 Superior Avenue Cleveland, OH 44114 (216} 696-7000 CIRCLE 329 ON FREE INFORMATION CARD McMaster-Carr Box 54960 Los Angeles, CA 90054 (213) 692-5911 CIRCLE 330 ON FREE INFORMATION CARD Metal working Digest 310 Gibraltar Drive Morris Plains. NJ 07950 (201) 292-5100 CIRCLE 331 ON FREE INFORMATION CARD Metlfax 29100 Aurora Road, Suite 200 Solon, OH 44139 (216) 248-1125 CIRCLE 332 ON FREE INFORMATION CARD Model Railroader 21027 Crossroad Circle Waukesha, Wl 53187 (414) 272-2060 CIRCLE 333 ON FREE INFORMATION CARD Modeltec Box 286 Cadillac, Ml 49601 (616) 775-6296 CIRCLE 334 ON FREE INFORMATION CARD New Equipment Digest 1100 Superior Avenue Cleveland, OH 44114 (216) 696-7000 CIRCLE 335 ON FREE INFORMATION CARD Roper Whitney 2833 Huffman Blvd Rockford, IL 61103 (815) 962-3011 CIRCLE 336 ON FREE INFORMATION CARD Rutland PO Box 587 LaPuente, CA 91747 (800) 289-4787 CIRCLE 337 ON FREE INFORMATION CARD Small Parts PO Box 381966 Miami, FL 33238 (305) 751-0856 CIRCLE 336 ON FREE INFORMATION CARD Used Equipment Directory 601 Pavonia Avenue Jersey City, NJ 07306 (800) 526-6052 CIRCLE 339 ON FREE INFORMATION CARD Wholesale Tool 12155 Stephens Warren, Ml 48090 (800) 521-3420 CIRCLE 340 ON FREE INFORMATION CARD Machine shop resources What does a hardware hacker really need in the way of purely me- chanical "machine shop" stuff? Ob- viously, it depends on where you live and what you are up to. But it is super easy to pour scads of time and dol- lars into overpriced machinery that you never use and that will never pay for itself. Either in income or pleasure returned. I live in a remote rural area, so I guess I've picked up more than I'd recommend in the way of shop tools. I do have a medium-sized drill press which is still precise enough and fast enough to drill a #67 hole in a printed circuit board. I've added a rotary X-Y table to it for light milling. There is a smallish Kepro printed circuit board shear, and my Roper- Whitney hand punch. A decent vise is a necessity for sure. A hand moto- tool. Also a largely unused Atlas four- inch lathe and the essential grinder to feed it. And finally a table-mounted router. The first thing you should do is look around your neighborhood and find out what nonobvious mechanical re- sources are available to you. Is there a retired machinist down your street with a full home shop and nothing to do? A community college with open- ended shop courses? Or some firms with excess capacity who could han- dle the work? Locally, there is this trailer hitch works that has a giant shear and brake. They can instantly and cheaply cut ten-gauge steel, usually from free scrap off the floor. Other locals I've gladly used include an air-con- ditioning shop, a ranch-machinery re- pair service, a solar products factory, and a heavy-machinery rebuilder/ trader. In our resource sidebar for this month, I've tried to gather together a few important hacker machine-shop resources. By far the most important two of these are Small Parts, who stock everything your hardware store never heard of and will custom cut metal and plastic for you in tiny quan- tities; and Lindsay Publications, who have a mind boggling array of lower- priced machine-shop books in stock. One oid-line "stocks everything" distributor is McMaster Carr, See if you can't cop one of their ^ humongous 3000-page catalogs. 2 Others include Enco. KBC Tools, J & i L Industrial Supply, Rutland, and 2 75 mmmmm mmmmm fri a »'■"■'. If H|»* p^«-i' ".il o m m mm tM mmmmmm Your Ticket To SUCCESS Over 28,000 technicians have gained admit- tance worldwide as certified professionals. Let your ticket start opening doors far you. ISCET offers Journeyman certification in Consumer Electronics, Industrial, Medical, Communications, Radar, Computer and Video. For more information, contact the International Society of Certified Electro- nics Technicians, 270B West Berry Street. Fort Worth, TX 76109; 1817) 921-9101. Name Address City State .Zip. _Send material about ISCET and becoming certified, _Send one "Study Guide for the I Associate Level CETTest." En- closed is $10 (inc. postage). 76 Get A Complete Course In ELECTRONIC ENGINEERING 8 volumes, over 2000 pages, including all necessary math and physics. 29 examinations to help you gauge your personal pro- gress. A truly great learning experience. Prepare now to take advan- tage of the growing demand for people able to work at the engin- eering level. Ask for our brochure giving com- plete details of content. Use your free information card number, or write us directly. $59.95 to $119.95, Postage Included. Satisfaction guaranteed or money refunded. fYA/b V Banner Technical Books, Inc. 1203 Grant Ave. Rockford, I L 61103 Wholesale Tool. And, of course, Sears. Two useful surplus sources include Bordens and C & H Sales. My favorite two mechanical trade magazines are Design News and Machine Design. The zillions of others include American Machinist the Used Equipment Directory, and Met I fax. There's also a huge collection of oversize "ihrowaway" shoppers that include New Equipment Digest Cgreat free product samples!), Industrial Product Bulletin. Industrial Equip- ment News, and also Metalworking Digest. On the hobby side of the fence, Model Railroader obviously belongs on this list. Two others include Home Shop Machinist and Modeltec. Once again, we've got a rather long list here, but I have a hoiiow feel- ing I've missed something major. For our second contest this month, just tell me about any hacker-useful ma- chine-shop resource that I don't al- ready know about. New tech literature There is a great Telecom Design Solutions manual from Teltone this month on such neat goodies as call- progress detectors and DTMF chips. Included are some great ap notes. And from Philiips/Signetics, a new data handbook on Programmable Logic Devices for your custom work. From Newark Electronics, a new 1300-page Catalog #111 on every- thing electronic that they distribute. New trade journals for this month include Circuits Assembly on printed circuit boards and Motion Control on robotic power controls. Newsletters include Robotics Now and the NSRA News, the latter from the National Service Robot Association. Burr Brown has just introduced an applica- tions and product info BBS at (602) 741-3978. In our free samples department, Excel has borrowed a marketing ploy from the magazine clearing houses — a series of stamps. Pick any three on the return card for free samples of their non-volatile memory products. And Annulus has free samples of their 8PDT switches which are great for switching serial ports or any EPROM chips into or out of circuit. For mechanical stuff, the definitive books and videos on glass etching are available through Professional Glass Consultants. Turning to my own products, for the essentials of making your hardware hacking profitable, check out my Incredible Secret Money Machine book. I have also just released the Hardware Hacker III and Midnight En- gineering book-on-demand published reprints. I do have this great new PostScript PSRT roundtable and library up on GEnie. You'll also find lots of Hardware Hacker and all of the Mid nigh t Engineering re p ri n t s h e re . Finally, I do have a new and free mailer for you that includes dozens of insider hardware hacking secret re- sources. Write or call for info. Our usual reminder here that most of the items mentioned appear either in the Names and Numbers or in the Machine Shop Resources sidebars. As always, this is your column and you can get technical help and off- the-wall networking per that Need Help? box. The best calling times are weekdays 8—5, Mountain Standard Time. Lets hear from you, R-E ASK RE continued from page 12 shock if you use a piece of wood to poke around in the guts of a TV set. I found that out the hard way. The shock wasn't too bad but I almost got a concussion when I was thrown across the room and my head hit the wall. Your typical flyback transformer is shown in Fig, 2. You can try to elimi- nate the noise by covering the trans- former with RTV high-voltage putty. If you can't get your hands on any of that stuff, you can use hot-melt glue as a substitute. I've used both of them. If you re lucky, the chances are that the stuff will coat the transformer well enough to eliminate the noise — or at least cut it down a bit. If that doesn't work, you can try tightening the bolts or whatever is holding the transformer in the TV set. You can wedge small pieces of thin plastic between the transformer and the chassis or circuit board to keep either of them from acting as a sound- ing board and, as a result, amplifying the squeal. Whatever you try, remember to re- spect the voltages generated in the TV set. High-voltage shocks can be deadly at worst... and shocking at best. 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CIRCLE 75 ON FREE INFORMATION CARD > 33 77 ■i;fnvn:in=i»M:7 Even though some test equipment is very simple, it can still be quite useful. —HIIIIII'lllllliil 60 o 2 O £ o LU _l LU 6 5 < EC Test equipment has changed over the last ten years or so. As the general nature of elec- tronics gets more complex, so does the type and amount of equipment you need on the bench. It used to be that all you really needed was a power supply and a bunch of luck, but that's not true any more. If you have a healthy budget, you can buy almost anything you need in the way of equipment but. if you're like most of us, you have to blow most of your hard earned money on stuff like rent, food, and other foolishness. In that case, the only alternative for your home workbench is to build the equipment you need as the need for it arises. That isn't quite as dreary as it sounds since the design and con- struction of basic test gear can be a good learning experience. As with any other design project, you should have 3 clear idea of what you want before you sit down to produce it. That's not as silly as it sounds be- cause, as I can see from the mail I get, a lot of people screw up simply be- cause they get started on doing things without really knowing what they want to do in the first place. The right way to go about design- ing something is to first sit down and think things out in a logical order. First decide what it is that you need to do. Then figure out the easiest, quickest, and cheapest way to do it. Don't go crazy adding features that are not re- lated to the main function, or ones that will never get used. That will only add unnecessary expense and effort to the project. And. quite often, ex- cessive features can actually get in the way of the intended application. It is a good idea, though, to add fea- tures that will speed up or lend a hand to whatever your original goal was. Interestingly enough, one of the most useful things you can have on a bench is also something that I've nev- er seen produced by any of the large commercial manufacturers. What I'm talking about here is a good source of bounceless pulses. There are lots of pulse generators on the market, but all I frequently need is a completely debounced mechanical switch — usu- ally several of them. There's nothing complex about building something like that but. for some reason, you have to do it your- self. I've never seen anything like it available commercially Debouncing switches is a simple procedure and there are lots of ways to get it done. All we need is a circuit that produces a clean output pulse whenever it's triggered. The elec- tronics involved are minimal since you can use anything from a handful of ordinary passive components to a 555-based circuit. Since I like to keep things as simple as possible while still providing as much flexibility as I can in the final product, I used a half mono- stable multivibrator as the foundation of the circuit (see Fig. 1). The nice thing about this approach to the problem is that, since the cir- cuit only uses one inverter, I can get six switches out of a single chip. There's no reason why you can't use noninverting buffers instead of the in- verters. All that will be different is that both the input and output pulses will be in the same direction. I used an inverter because I had some spare ones lying around and you'll probably make your choice for exactly the same reason. Since I frequently need both positive- and negative-going pulses, I used two IC's to produce twelve bounceless switches. Six of them are positive-going and six of them are negative-going. The whole assembly is in a small plastic box with thirteen sets of terminals on it — twelve for the switch outputs and one for power. The resistors on the outputs of the gates are there to provide a bit of protection for the IC, They limit the current and also help isolate the cir- cuit I'm working on from the switch box. I could have used diodes (which would have been a lot better), but I didn't have any around at the Lime and. since I never had a problem, I never changed anything. It's always good practice to isolate the circuit you're working on from the test equipment you're using. You nev- er know what's going to happen and, in case you've forgotten, the reason you're using test gear is because your design is still being tested. While we're on the subject of trivial things, you should also build some FIG. 1— A HALF MONOSTABLE MULTIVIBRATOR is the foundation of the switch-de- bouncer circuit. Six switches can be made from a single chip, but since positive' and negative-going pulses may be needed, two IC's are used to produce six positive-going and six negative-going bounceless switches. 78 R-E Engineering Admart Rates; Ads are 2!4"x2 ; ,i", One insertion $995 each. Six insertions $950 each. Twelve insertions $925 each. Closing date same as regular rate card. Send order with remittance to Engineering Admart, Radio-Electronics Magazine, 500-B Bi-County Blvd., Farmingdaie, NY 11735. Direct telephone inquiries to Arline Fishman, area code-1-516-293-3000, FAX 1-516-293-3115. Only 168% Engineering ads are accepted for this Admart. Surface Mount Chip Component t Prototyping Kits— \ Only 51 CC-f Capacitor Kit contains 3&5 pieces, bea. ol every 10*4 value Irora 1pl to .33j*f. CB-1 Resislot Kit contains 1540 piBcesJQea. of every 546 value from 10fz to 10 meg®. Sizes are 0805 and 1206. Each kit Is ONLY $49.95 and available for immediate One Day Delivery! Order by toil-free phone. FAX, or mail. We accept VISA, MC, AMEX, COD, or Pre-paid orders. Company P.O.'s accepted with approved credit. Call for free detailed brochure. I COMMUNICATIONS SPECIALISTS. INC. ' 42S West Tall Ave. ■ Orange, CA 926*54296 Local (714) 998-3021 • FAX (714) 974-3420 Entire USA 1 -800-854-0547 FCC LICENSE PREPARATION The FCC has revised and updated the commercial license exam. The NEW EXAM covers updated marina and aviation rules and regulations, transistor and digital circuitry. THE GENERAL RADIOTELEPHONE OPERATOR LICENSE - STUDY GUIDE contains vital information. VIDEO SEMINAR KITS ARE NOW AVAILABLE. WPT PUBLICATIONS 979 Young Street, Suite E Woodburn, Oregon 97071 Phone (503) 981-5159 Dept. 50 Plans . . . Small Budget?? 6805 Microcomputer Development System TECIs MCPM-1 system allows your IBM PC ana Compalioles to tie used as a complete development system for the Motorola 6805 family ol single chip microcomputers. Many time saving features at an aflordable price. MCPM-t Programmer rpr Motorola MCfi87B5P3, P5, U3. 1)5. R3, RS MCPM-1 witjriver, assembler, simulaloridebupjer $449 MCPM-t wd river program only 5349 Also avaitabie— Programmer for 68HC05, in-circui! emulators and many software tools to help you. Call for a complete catalog and lei us help you select your tools. TECik TIie Engineers CollaSoritive. Inc. hi. *3 Bra EC Bjrton, VT 05860 IIS* TEl 13021 5ij.3«B nx. (BOZ] iZ5-^51 Call toll Free HOP) 33S-B3Z CIRCLE 19C ON FREE INFORMATION CARD CIRCLE 177 ON FREE INFORMATION CARD substitution boxes for yourself. Elec- tronics is a fairly exact science, and there are formulas that tell you what combination of passive components to use when you want a particular signal at the output of a circuit. From a practical point of view, formulas are good for the initial stages of a design but, as things evolve, its really handy to be able to change things quickiy and easily. The keyword here is "easily," be- cause from a practical point of view, breadboards tend to be incredibly messy. I always start out with the best of intentions — all power leads are red, ground leads are kept black, etc. — but that always falls apart half- way into the design. Substituting re- sistors and capacitors is theoretically a simple thing but it can take a long time and a lot of care to swap compo- nents on a crowded breadboard. The only way to do it without the risk of accidentally pulling out other connec- tions Cand being unaware that you've done that), is to have a substitution box that terminates in a pair of insu- lated alligator clips. AH you need is a break-before- make single-pole rotary switch with as many positions as you need for the number of resistors or capacitors you're going to use. One end of the resistors gets connected to the poles on the rotary switch and the other ends are tied together and connected to a clip lead. The only thing left to do is connect a clip lead to the selector pole on the rotary switch and you're in business. If you do the same thing with ca- pacitors, you'll have two things to worry about: one, the extra wiring and switches will change the capaci- tor values from what you might ex- pect, and two, you should have some way to watch the polarity of the elec- trolytics and be sure to discharge them before you use the substitution box in a circuit. Remember that even a medium-sized electrolytic can store a healthy charge and, if the circuit you're working on is sensitive to ca- pacitive discharges, you can do some real damage if you forget to discharge the capacitor before connecting it to the circuit. All the things we've talked about here can be built in a minimum amount of time with a minimum amount of parts and brain damage. What you'll probably find, however, is that they'll be the most frequently used items on the bench. They aren't really test equipment in the strictest sense of the word but they'll make life a lot easier when you're working and that's definitely a good thing. Beiieve me. There are iots of other, non-elec- tronic, useful things you can put to- getherthatwill make your bench time as productive as possible. Even something as simple as a bunch of LED's, each with it's own current-lim- iting resistor, can be a handy tool to have around. It can save time rum- maging through parts drawers, be- cause one of the most basic rules on the bench is: The more you need something, the more time it takes to find it. Now, I'm the first to admit that the things I've been talking about here aren't exactly of the "gee-whiz" vari- ety, but that doesn't mean that you shouldn't take them seriously. A friend of mine works for Grumman and I used to visit him at work all the time when he was working on the Lunar lander. I know from personal observation that a lot of the final checks were done using an ordinary multimeter and a test light that was made from a single LED and a 1K resistor. When we get together next month. we'll take a look at some test gear you can build that's a bit more inter- esting — electronically speaking. But keep in mind that, even though cer- tain instruments are loaded with glitz and glitter, every instrument has it's own particular jot) — while it's true that you can't watch a waveform on an LED. it's also true that you can't use an oscilloscope to clean up a trigger- | ing pulse. Don't put down the really F simple stuff just because it happens & to be simple! b-e - 79 P'\hi](ii rrTrrvTS Audio amplifiers: Do they sound different? LARRY KLEIN w o z. O a t- o LU _i u O □ < When I first became involved with audio equipment in the 1950s, everything sounded different. If fact, it was difficult to get two samples of the same model pho- no cartridge, speaker, or even pre- amplifier that sounded identical. No one thought to complain because in- consistency was a basic fact of audio life at the time. We all knew that audio equipment was "touchy" as befitted finely tuned products engaged in pushing the state of the sonic art. The truth of the matter was that many of those early consumer-level audio products were badly designed, used low-grade parts, and were marketed without benefit of adequate quality control. The sonic sixties By the 1960s, audio equipment had gotten a lot better. When you first plugged in your new component, it usually worked; and if measured, it probably came within shooting dis- tance of its rated specs. However, with the advent of transistorized equipment, quality took a nose dive. Audio buffs incautious enough tc rush into the new technology encoun- tered poor sensitivity and front-end overload in tuners; nonlinear inputs in phono preamps; overload, crossover distortion, and repeated failures in amplifiers. But after several years of solid-state travail, both reliability and sound quality substantially improved. Do transistor amplifiers sound bet- ter or worse than their tubed counter- parts? That question has been vehemently argued right up to the present by those who prefer the "warmth" of vacuum-tube sound to the sonic "sterility" of semiconduc- tors. Technical limitations of the early semiconductors and their circuits fre- quently did cause sonic problems, but these were neither as inherent nor as inevitable as the tube lovers liked to believe. Today, there's no doubt, in my mind, at least, that audio transistors can do anything tubes can do — and better! Series impedance Figure 1 shows the series imped- ance of a typical speaker hookup. Impedance Z t is the output imped- ance of the amplifier, Z 2 is the resis- tance in the speaker wire, and Z 3 is the complex impedance of a nominal 8-ohm speaker. The speaker imped- ance includes the crossover ele- ments plus the impedance of the speaker, which typically varies widely SPEAKER AMP u I FT] : *■ : (H \ FIG. 1— THE IMPEDANCES FOUND in a typical speaker connection. over the audio band. What we have, in effect, is a voltage divider where Z : and Z 2 usually add up to well under 1 ohm in contrast to Z 3 , which can vary with frequency between 3.5 and 40 ohms. Insofar as Z, and Z 2 are low, the amplifier is a constant voltage source across the audio band and the signal reaching the speaker is un- affected. But if an amplifier has a high output impedance and/or the speak- er wire is too thin, the speaker's nor- mal impedance curve will be reflected by bumps and dips in the frequency response measured at the speaker terminals. See Fig. 2. Although conventional wisdom states that a 1-dB variation is barely detectable, in reality the location and the Q (width) of ±1 dips and peaks can affect many aspects of the per- ceived sound. Subjective qualities such as depth, openness, inner de- tail, harshness, wide/deep sound staging, and so forth are the ear/ brain's responses to minor bumps and dips in various areas of the audio spectrum. Examples: A small rise in the octaves centered at 300 Hz will result in an enhanced sense of warmth and ambience because that's where ambience information is found in the concert hall and on recordings. Enhanced "definition" and "inner de- tail" result from boosts in the octaves centered around 4 kHz (as in Fig. 2) where the ear is most sensitive. And so forth. Amplifier sound Under what, if any, circumstances do amplifiers sound different from one another? Obviously, if an ampli- fier is driven into continuous clipping because of its limited power, a more powerful unit is likely to sound better. 2 3 4 5 67831 20 100 2 3 4 5 6 7 891 1000 FREQUENCY IH CYCLES PER SECOND 2 3 4 5 6 7891 2 10000 20000 FIG. 2— TYPICAL FREQUENCY RESPONSE at the speaker terminals when Z, or Z 2 are high. 80 Now NRI trains you to be today's expert security electronics technician as you install and troubleshoot state- of-the-art security systems in your own home and auto. Violent crime, theft, fire, . .they're facts of life in the U.S. today. But now there's good news, too. All across the nation people are fighting back with high-tech electronic security systems. In fact, Americans will spend over 17 billion dollars on security services and equipment by the year 1991. For you, this new consumer demand for electronic security systems means even more good news. It means a breakthrough opportunity to get in on the ground floor of a booming new industry. Now, no matter where you live, you can start a high-paying career— even a business of your own— in- stalling, servicing, and maintaining residen- tial and commercial security systems. Best of all, NRI's ready now to give you the hands-on security electronics training you need to get started fast. Make good money in a challenging career as a \ security electronics technicians- even start a profitable new business of your own Right away, you get the skills you need to install and service all security systems NRI's at-home Security Electronics training gives you solid electronics know-how, plus a complete working ^^^^^^^^^^ knowledge of popular security devices in use today. You learn how to install and service magnetic contacts and pressure mats . , . microwave, ultra- sonic, and passive in- frared detectors . , . personal identifica- tion systems and electronic listening devices. , .even cen- tral station alarm systems and today's most sophisticated fire warning equip- ment. 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I Ncjme_ | Address 1 I SCHOOL OF ELECTRONICS McGraw-Hill Continuing Education Center 4401 Connecticut Avenue, Washington, DC 20008. 3" Check one catalog only D Security Electro nits □ Robotics O Computers and O MVideoftudio Servicing Microprocessors □ Basic Eleclranics if Nil «* D Air Conditioning, Heating, ond Refrigeration □ Electrician Age_ (~J Small Engine Repair J Automotive Servicing D totlcsmithing City. . State. Accredited Member National Harm study Council For career courses approved under Gl Bill D check for details. > TJ 83 Or if an amplifier, because of poor design or malfunction, suffers from any of a number of well-understood circuit problems, it also can sound inferior to other better-designed products. But what accounts for the reported differences in sound quality among amplifiers that on the test bench are virtually distortion -free and have a ruler-flat response from in- frasonic to ultrasonic frequencies? Of course, most of the reported differences can be charged up to the overactive imaginations of devout au- diophiles for whom the ability to de- tect such differences makes life worth living. But there are sometimes good technical reasons for the "mys- terious" qualities heard by audiophile listeners. The most meaningful way to mea- sure an amplifier's frequency re- sponse is not as a black box, but as part of a system. Specifically, instead of graphing amplifier response across the standard 8-ohm resistive load (or the ElA-recommended com- plex load), measure the amplifier re- sponse across the terminals of a connected speaker system. With a typical good-quality transistor ampli- fier, the frequency response will be the same measured at the amplifier and at the speaker terminals. This assumes that: (1) the amplifier has a low output impedance, (2) the speak- er connecting wire is of heavy enough gauge to have reasonably low resis- tance for the length used, and (3) the speaker impedance curve doesn't fall into the basement at some frequen- cies. Interestingly enough, audiophile equipment sometimes fails to meet one or more of these criteria. Tube equipment, in particular, tends to have relatively high output imped- ances — up to perhaps 1.5 ohms. Amplifier listening tests How does all of the above square with the results of more than twenty published "blind" comparison listen- ing tests? Basically, the tests have demonstrated repeatedly that so- called golden-ear audiophiles are not able to differentiate among amplifiers when they did not know which they were listening to. Since the effects discussed above occur only if the am- plifier under test has a high output impedance and the reference speak- ers have a non-flat impedance curve to interact with it, the vast majority of amplifiers are going to be indis- tinguishable from each other under any reasonable listening condition. In a recent discussion with Bob Carver on the "Carver Challenge" (discussed in my December 1990 and March 1991 columns), he con- fided that the main change he made in his $700 transistor amplifier to dupli- cate the sound of a $10,000 tube unit was to add resistance in the tran- sistor amp's output stage in order to mimic the tube unit's high output im- pedance. You can try it yourself using low-value 20-watt resistors or a pair of 2-ohm power rheostats. You need to add anywhere from 0.25 to 1.5 ohms resistance to your speaker lines depending upon your speakers and room acoustics. If you hit the required value, your conventional transistor amplifier will then magically have most of the special sonic qualities that audiophiles covet in their $10,000 tube units. If you try the experiment, I'll be interested in how it works out. R-E LASER PRINTER continued from page 1 7 u z o DC H O w g < rr sitive drum, the toner, and the motors to move the paper through the copier, we can con- vert a photocopier into a "laser printer" with relative ease. To produce the image on the paper we simply need to place an image onto the copier which can be copied onto the paper. The copier will do the rest of the work for us. Since a computer monitor is capable of high-resolution graph- ics, we will use a computer monitor strapped onto the copy machine to produce our image to be transferred to the paper. Construction The system can be built using a monochrome monitor. However, a VGA monitor should be used, as it has much better graphics resolution. The better the monitor, the better the final im- age. Construction of the "laser printer" is accomplished by strapping the VGA monitor onto the copy machine. Also the light bulb inside the copier must be removed. The computer monitor must be located on the glass sur- face of the copier so that it is lined up with the 8V2- by 11-inch paper area. The monitor can be secured to the copier surface using C clam- ps, superglue, or even large rub- ber bands or Bungee cords — the kind you use to strap things to the top of the car with, not the kind you jump off bridges with. The exact method used will de- pend on the copy machine and how easy the monitor can be se- cured to it. Figure 1 shows how we did it. Be sure that the cables to the monitor are not laying be- tween the copier's glass surface and the monitor screen, and that they reach to your computer's video output. The monitor should not be glued into place until you have "laser" printed a few pages to check the alignment of the monitor on the copier glass. Once a few pages have been printed, and the monitor's align- ment has been established as correct, then the monitor can be secured to the copier. To remove the copier's light bulb, open up the copier and find the bulb. It is usually located near the copier's glass surface, and may be accessible only by remov- ing the copier's glass. The light bulb must be removed because the VGA monitor will now supply the light to expose the photosen- sitive drum. (The light is nor- mally supplied by the light bulb reflecting off of the paper of the original.) Usage To test the "laser printer, " put a graphics image onto the VGA monitor screen and simply press the COPY button. The image on the copier output paper should be a reproduction of the VGA im- age. Use several images to test the alignment of the VGA monitor, repositioning the monitor until the image is well centered. The monitor can then be secured to the copier. Both text and graphics can be printed, with the only limits being those of the VGA display. Since copy machines can easily produce eight pages per minute, the "laser printer" is a very cheap alternative to purchasing a "real" one. APR-l 84 MWH'Hl.m The evolution of standards JEFF HOLTZMAN The following is a reply to the letter from Raymond Cheng of Ontario published in this month's "Letters" column: Ten years is right. Technological in- novations typically take ten years to attain widespread acceptance. And like it or not, the latest release of Windows has done more for promot- ing advanced computing environ- ments than everything done by all the Amigas (and all the Macintoshes) put together over the past five or six years. Why don 't we provide more Amiga coverage? That's easy. Most Radio- Electronics readers use PC's. Fur- ther, electronics experimenters just don't seem to have much interest in the Amiga, so we get few article sub- missions for it. But if we did get any, and if they were any good, we would publish them. We're not anti-Amiga. We and our readers enjoy reading about alternate approaches. We have championed other "underdog'' sys- tems in the past; remember Peter Stark's series on the PT-68K? As for the Amiga, I'm sure it's a worthy computer. But — evangelism and chauvinism aside — what effect has it had on the computer industry, and what innovations has St supplied? I don't believe that preemptive multi- tasking was invented at Commodore, nor was NTSC video, coprocessor- based I/O, the GUI, multimedia, and any of several other advanced archi- tectural features. The Amiga wasn't even the first machine to combine several advanced architectural ele- ments; take a look at the Xerox Star from the early 1 980's , and many engi- neering workstations that were pro- duced since then. You might argue that the Amiga was the first low-cost computer with those features, and I'd agree with that. But so what? Here's my point about influence. The Amiga has had precious little influence thus far, and I feel certain that its position and Com- modore's will only decline. Why doesn't Commodore build a low-cost MS-DOS multimedia machine? That might save the company. The original Macintosh was inno- vative, as is Job's latest brainchild, the Next. But neither has attracted significant market share, and Apple's continues its steady decline in the marketplace. By contrast, the PC industry has seen a history of continual innovation in all facets of computer technology. The rate of innovation, combined with the concomitant lack of standards, has created many problems, some of which will be with us for many years. I'm sure Mr. Cheng would be more than willing to point out those faults for us, but he needn't bother; they're self-evident. And there are lots of very smart people working on solu- tions to those problems — more on this below. Mr. Cheng, you can bash MS-DOS and the PC architecture all you want, but together they have changed the world. At best, the Amiga has main- tained a spot on the periphery of the PC revolution. Mr. Cheng, if you want to promote the Amiga, don't write a sarcastic let- ter to the Editor. Do something inter- esting with your machine, and then share it with us. We'll then get it in print. PS. Mr. Cheng: For your informa- tion, the value of acceleration in free fall Con Earth, anyway) is 32 ft/sec 2 , not m/sec 2 . Standards and devolution Revolution, like parenthood, is messy. Every revolution starts as a radical shift away from an inadequate status quo. Then comes a period of uneasiness during which anything imaginable seems possible. The final stage is marked by the adoption of a new status quo, which thereby sets the stage for the cycle to repeat itself again. The 80*s represent the computer world's Boston Tea Party. Shots were fired, ties were broken, new powers arose and seized control. Like the best revolutions, the computer revo- lution is a grass-roots affair. Individu- als saw the power represented by the personal computer and grabbed it. Soon the world noticed that all those PC users were a force to contend with: the steady decline of the main- frame and minicomputer industries has been a shock mostly to those involved, not to those of us who've been involved with PC's from the very beginning. In the grass-roots surge for power, however, something got lost in the shuffle: standards. When the revolu- tion started, we knew only two things: that we needed personal computers and that we didn't want to do things the mainframe way. So we made things up as we went along. Doing so was good, in that it gave us a fresh slant on whatever it was that we wanted to do. But it also led to many of the difficult problems that PC and MS-DOS bashers love to use against us, A couple of years down the road, it turns out that some mainframe/mini ways aren't so bad. It turns out that the mainframe and mini industries solved certain types of problems back in the 60's and 70s, and that those problems have come back to haunt us. Things like managing pro- grams so large that they can't fit in available memory, things like running multiple programs simultaneously, things like intelligent I/O sub- systems. The difference now is one of focus. When we thought about virtual mem- ory in the past, we associated it with mainframes. Now it's becoming clear to us that PC's need virtual memory as well. Likewise with multitasking, graphical environments, and all the rest. You may think that we don't need % those things. And you're right — as p long as you think only in terms of ^ doing things the way we learned to do 2 85 R-E Computer Admart IC. PROMPT DELIVERY!!! 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Send order with remittance to Computer Admart, Radio-Electronics Magazine, 500-B Bi-County Blvd., Farmingdale, NY 11735. Direct telephone inquiries to Arline Fishman, area code-1-516-293-3Q00. FAX 1-516-293-3115. Only 106% Computer ads are accepted for this Admart, SECRETS OF THE COMMODORE 64 COMMODORE $* BP135— A beginners guide to the Commodore 64 pre- sents masses of useful data and programming tips, as well as describing how to get the best from the powerful sound and graph- ics facilities. We look at how the memory is organized, random numbers and ways of generating them, graphics-color-and sim- ple animation, and even a chapter on ma- chine code. Get your copy today. Send $5.00 plus $1.25 for shipping in the U.S. to Electronic Tec ho logy Today Inc.. P.O. Box 240, Massapequa Park, NY 11762-0240. GETTING THE MOST FROM YOUR PRINTER Getting The Most From Your Printer BP18.1— It is probable that 80% of dot-ma- trix printer users only ever use 20% of the features offered by their printers. This book will help you unlock the special features and capabilities that you probably don't even know exist. To order your copy send $6.95 plus $1.50 for shipping in the U.S. to Elec- tronic Technology Today Inc., P.O. Box 240, Massapequa Park, NY 11762-0240. CIRCLE 61 ON FREE INFORMATION CARD W 2 Z o E O LU o Q < LT them during the 80s. The problem is that the 80 s way was only a first ap- proximation, a first step toward solv- ing the real problems in our ever- changing world. It's not really very important whether F1 represents Help and F10 Exit; The real problem is how to model the real world in a useful way. The problem is not how to put italic text on screen and on paper, but how to rep- resent real documents in the full richness with which they appear in everyday life. The problem is not how to build educational software, but how to build software that is fun, and by the way educational. The problem is not how to build real-time systems with a certain response rate and throughput, but how to build real-time systems that can adapt to changing real-world conditions. Ultimately the problem is not how to do the same old things in the same old ways, but how to do them in a faster or cheaper way The real prob- lem is to learn how to focus on our real problems, which will of necessity entail inventing new ways of doing things. For example, we don't just want to learn how to make cars cheaper. We need to learn how to respond to what customers want, when they want it. and in a quality manner. Enough. All this is about the PC revolution. The next step The biggest problem facing the PC industry is not that the PC isn't an Amiga or a Mac or a SparcStation or a MicroVAX or a you-name-it. The biggest problem isn't that the PC in- dustry is ten years behind. The real problem is standards: the lack of standards, the need for standards, the difficulty of achieving meaningful standards before they become out- dated (witness the S-100 bus), stan- dards that are flexible enough to accommodate future innovation, and the difficulty of reconciling the stan- dards we need with our ability to pay for them. Until we solve those problems, things will be chaotic, so we will waste huge amounts of time and effort resolving incompatibilities. Meanwhile, Europe and Japan con- tinue their steady creep with their ad- vancing technologies. In some ways, we need standards more than innovation. In the case of competing standards, we need stan- dard ways of bridging incom- patibilities. We need simple, trans- parent ways of sharing documents, whether the source is Word, Mac- Write, PageMaker, or AmigaT e X; of sharing files across operating sys- tems; of integrating diverse platforms (PC, Mac, workstations, even Amigas) on a network; and of display- ing fonts on screen and on paper. We need to easily send Email across the office, across the country, or across the world. We need to quickly get at on-line data. We need simple, trans- parent ways of performing system backups; upgrading system soft- ware, even while it's running; and inte- grating data in all the forms that nature provides. We need a cheap multimedia machine with a megapixel display, megabytes of memory, pre- emptive multitasking, an easy-to-use operating-system shell, and enough intelligence to start doing the kinds of work computers are supposed to do, so that we can spend less time housekeeping and more time doing the kinds of work we're supposed to do. It is beyond the capability of any single U.S. company to solve most of those problems. If solutions are to be had, they must come about through a modified, cooperative form of com- petition. It's great that Lotus and Borland compete over spreadsheets like tigers in a cage. But they must remember that customers buy holes, not drill bits. In other words, custom- ers buy solutions, not technologies. Customers won't buy Quattro be- cause it's "better" than 1-2-3; they will buy it if it solves their problems better. Or they should. And that brings us to the other side of the coin: customer education. Customers are lazy, especially in 86 this country. Many people think that once they've learned one way of doing something, they should never have to learn another. They think that they should only have to pay their dues once. Because of the way tech- nology is evolving, however, that's a very unhealthy attitude. Just because you've learned 1-2-3 or WordPerfect, that doesn't give you the right to for- ever forsake learning any other pack- age. If you as an individual want to be successful, you should also take it upon yourself to learn Word, Word- Star, Quattro, Excel, and every other package you can get your hands on. Until software has become as stan- dardized as open-end wrenches, you'll only enhance your worth in the job market by learning everything you can about everything you can get your hands on — and I don't mean just word processors and spreadsheets; the same principle applies, re- gardless of the tools of your par- ticular trade. We don't have the standards we need; likely it will take another de- cade or longer for all the pieces to fall into place. In the meantime, we as a country must remain flexible enough to roll with the punches. And if that means learning WordStar today, WordPerfect tomorrow, and Word next week, so be it. The point is that we've got to get to the point where it's worth standardizing, and leave it at that. Emerging standards Several standards are lurking just beyond the horizon. What are they? How do they impact us today? How will they impact us tomorrow? Take a look at Fig. 1. That diagram goes by various names, but it is com- monly known as the "Toaster Di- agram" because of its resemblance to an old-fashioned toaster. Ad- vanced thinkers in the U.S. and Eu- rope use the Toaster Diagram as a conceptual model for the Computer Aided Software Engineering (CASE) environment of the future. The idea is to provide a basic framework of com- mon computer services into which you may drop customization modules like slices of toast. The framework consists of a base communications layer through which all the "slices" communicate. The front slice is the user interface, by means of which we communicate with the system. Parallel slices pro- FIG. 1— THIS IS COMMONLY KNOWN as the "Toaster Diagram" because of its re- semblance to an old-fashioned toaster. Advanced thinkers in the U.S. and Europe use the diagram to illustrate the basic framework of common computer services into which you may drop customization modules like slices of toast. vide data and task management; orthogonal slices provide "slots" into which special-purpose tools fit. That's the vision of where CASE tools are going, But it doesn't take a whole lot of thought to recognize that that type of model may be useful wherever disparate tools and data must work in concert. In fact, the framework-with-installa- ble-modules idea is becoming per- vasive. Windows, for example, provides a framework with a basic set of services, including a user inter- face, the ability to launch and super- vise programs, file and data manage- ment. You can install your own slices (word processors, spreadsheets, etc.), and make them work together via Dynamic Data Exchange (DDE), Never mind that Windows is flawed; the framework is what's important, DDE is weak, but it proves the princi- ple. And Microsoft is working on ex- tensions called Object Linking and Embedding COLE). You can do similar things in other environments. What's needed then is a set of standards that extends the frame- work metaphor across networks and platforms. That's when we'll reach the third stage of the revolution. That's when we'll be able to include Mr. Cheng's Amiga text file with a Mac file from the art department with some specs from the UNIX-based engineering group... Did I mention UNIX? Still think it's a dirty word? DOS + Windows is evolving to- ward OS/2. OS/2 includes by design virtually every advanced feature of vir- tually every advanced operating sys- tem, including UNIX. OS/2 is evolving toward POSIX. an IEEE stan- dard that is rapidly becoming the standard for UNIX-like operating sys- tems. Other mainframe and mini op- erating systems will be POSIX- compliant soon as well. POSIX is nothing if not an operating-system framework in the sense used above. If everything else is evolving toward POSIX, where does that leave the 60- million DOS-based PC's? And what about the Macs and Amigas? And why is Motorola's share of the CPU market expected to drop from 25% to 17% this year? I don't have answers to those -o questions. But if you think you have p some answers feel free to write c/o ^ the magazine. R-E 2 87 MARKET CENTER FOR SALE w o z o %5*Ja JpOOi Each Each Hours open 10:00 am to 4:00 pm Eastern time Minimum order 5 units 55.00 ea. Dealers wanted. We ship COD. King Wholesale 1-800-729-0036 Fax number 6173400053 'Wo one beats the King's prices!" 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I NCLUO E 1 0% SHI PPIN6. ORDERS S10J.00 A UP MIL* ADD $10.00. CATALOG St. 00 OP FREE WITH OROER. INFORMATION UNLIMITED P.O. BOX 71 B, DEPT. R3, AMHERST, NH 03031 ELECTRONIC ASSEMBLY BUSINESS Stan home, spare time. Investment knowledge or experience unnecessary. BIG DEMAND assem- bling electronic devices. Sales handled by profes- sionals. Unusual business opportunity. FREE: Complete illustrated literature BARTARE-0oBux248 Walnul Creek. Calil 94597 BEST BY MAIL nates: Write National, Box 5, Sarasota, FL 34230 BUSINESS OPPORTUNITIES LET the government finance your small business. Gran Moans to $500,000. Free recorded message: (707)449-8600, (KS1). MAKE 575,000 to 5250,000 yearly or more fixing IBM color monitors (and most brands). No invest- ment. Start doing it from your home. (A telephone required.) Information, USA, Canada $1.00 cash. US funds. Other countries 53.00 RANDALL DIS- PLAY, Box 2168-R, Van Nuys, CA 91404 USA. ANTIQUE RADIO CLASSIFIED Free Sample! 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And we guarantee 100% satisfaction. Guaranteed Low Prices State-of-the-Art technical support Top Quality Tested Products Dealer Market Support WHOLESALE CABLE SUPPLY Low Price is only the beginning 1-800-926-6836 1723 CAMINO PLAZA, STE. 108, SAN BRUNO, CA 94066 Monthly Special • TB-3 or SA-3B • 8 10 lot 48 • § 20 lot - 43 * cc 50 lot - 39 o 100 lot - 39 3 Z-TAC 6 10 lot - 149 Try the Elm-trui litis bulletin board system (RE-BBS) 516-293-2283 The more you use it the more useful it becomes. We support 300 and 1290 baud operation. Parameters: BN1 (8 data bits, no parity, 1 stop bit) or 7 El (7 data bits, even parity, 1 stop bit). Add yourself to our user Tiles to increase your access. Communicate with other R-E readers. Leave your comments on R-E with the SYS0P RE-BBS 516-293-2283 FREE NEW AUTOMOBILES AND VACATIONS FOR LIFE! Intermedia, Box 1441-(RE), Ballwln, MO 63 022-1441. __ JOB MARKET TOUGH? Consider Professional Retlrs- ment Counseling. 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DESCRAMBLERS ***** STARRING ***** JKRROLD, HAMLIN, OAK AND OTHER FAMOUS MANUFACTURERS • FINEST WARRANTY PROGRAM AVAILABLE ■ LOWEST RETAIL I WHOLESALE PRICES IN US. ■ ORDERS SHIPPED FROM STOCK WITHIN 24 HRS. ■ ALL MAJOR CREDIT CARDS ACCEPTED FOB FREE CATALOG ONLY 1-8O0-345-89Z7 FOR ALL INFORMATION 1-BIB-709-99 3 7y PACIFIC CABLE CO.. INC. 7325V: Reseda Blvd.. Dept.2101 Reseda. CA 91335 ZENITH & TOCOMS SUPER Zenith (Z-TAC) converters {(lashing)... $169.00, Zenith "turn-on" module... $49.00. Tocom 5503(A) & 5504 converters... $139.00. Tocom (addon) descramWers... $79,00, Tocom (5503-VIP & 5507) "turn-on" chips... $49.00. CIN- EPLEX VIDEO GROUP. 1 (BOO) 726-4627. INVENTORS INVENTORS! Can you patent and profit from your idea? Call AMERICAN INVENTORS CORPORA- TION for free information. Over a decade of service 1 (800) 338-5656. In Canada call (413) 568-3753. 92 WANTED INVENTIONS/ new products /ideas wanted: call TLCI for tree information 1 (800) 468-7200 24 hours; day - USA/Canada. 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STOCKS LS9200 PRICE $49.99 ■ Individually wrapped ■ Dispenser pack STOCK s DESC. PRICE SB1104 25 £1.99 SB1107 100 $4.99 ■ includes: Cleaning swabs, head- cleaning fluid, anti-stairc cleaner, screen wipes and cleaning diskette. STOCK * DESC. PRICE SB1099 3W kit S6.99 SB1100 5'." kit $6.99 EPROMS STOCK « 1-24 25-99 100* STOCK » 1-24 25-99 100» 1702 2708 1716 2716-1 TMS2716 27C16 2732 273ZA-! 2732A 2732A-4 TMS2532 TMS2S32P 27C32 2764-20 2764 2764A-20 MK40Z7 4116-120 4116-150 4116-200 4116-250 4164-100 4164-120 4164-150 (164-200 4416-120 4416-150 4.59 4.36 6.49 6.17 3.29 3.13 3.79 3.60 5.79 6.50 3.99 3.79 4.19 .3.93 3.79 3.60 3.69 3.51 3.19 3.03 5.79 5.50 199 1.89 3.79 3.60 4.29 4.03 3.99 3.79 3.92 2764A S.SS TMS2564 2.82 27064 324 27128-20 4.95 27126 3.41 271 28A 3.5B 270126 3.24 27256-20 3.16 27256 2.73 27C2S6 4 95 27512-20 1,70 27512 J.24 27C51! 3.87 27C1024 66764 66766 3.41 3.41 3.49 3.32 5.79 5.50 3.29 3.13 4.99 4,74 4.79 4.55 4.79 4.65 4 79 4.55 5.29 5.03 479 4.55 4 29 4.03 6.49 6.17 5.99 5.89 5.99 5.69 12.99 12.34 13.99 13.29 12.99 12.34 2.99 4.95 328 4.27 4.09 4.09 4.09 4.53 409 3.67 5.55 5.12 5.12 11 11 11.96 11.11 DYNAMIC RAMS 69 56 50 4464-100 1.39 1.32 1.19 4464.120 1.24 25-99 100- STOCK" 1-24 25-99 100> 299 2.84 2.56 2.79 2-65 239 229 2.13 1.96 2.99 2.E4 256 279 265 239 1.99 1.89 1.70 1.63 1.53 5.6S 5.12 5.49 1.22 4.70 39 St 59 35 4464-150 77 41256-60 50 41256-80 1.89 190 1.63 41256-100 1.69 1.61 155 41256-120 1.59 1.51 136 41256-150 139 1.32 1.19 511000-70 199 1.89 170 51100040 179 1.70 1.53 511000-100 165 1.79 1.80 1.70 6,49 6.17 5.99 5.6 ORDER Bl PHONE.' 10010 Canoga Ave.. Unit B-8 ■ Chalsworln. CA 91311 OUTSIDE CALIFORNIA: (SDO) 824-3432 (Orders Only) IN CALIFORNIA: (818) 341-S833 ORDER BY FAX: (818) 99B-797S Minimum Order $15.00 * 24-hcur ordering available > TJ 93 CIRCLE 187 ON FREE INFORMATION CARD TdonVU Vidtophont in a Chip STILL FRAME TV PICTURE TELEPHONE TRANCE1VER KIT Sonds Slow Scan TV plctur*a ov«r Th» phon* Nn* In "Tw»Ivbp S«cond9 1 Auto Mode Bllowl hAndH frat Band And rocel vo. Dlaplllyl on any TV IC Chip RnplQcnJi ISO SSI Olpa BBTClBlirfMi^.BnM .Camsra tmm^mn,. 50 Levels J&ss™.' o) Grey Scale ■ "■ Serves as: TV FAX mi «15 High R«, so.ooo P I lei ■ "* CWD "cti»d ro juua uawm weaken Vld>ophon» Chip 48P DIP .— I — | . 1 »nd Schtmillo J5B.35 ;Tll. I |Mon.[ *-| A/D, DHAM, D-RtJ. $3i00 PC Board (BARE) 50 Has. Cap. DJodi Cabinet (uncut) Power Pack WT PHCE Phanvu Til Lint < j Medullar] Ue» I vcr n^i Mod. Li-J $18.95 529.7b S 12,75 .5 8.75 $ 184.15 I FAX Orefe Etoctror S 23&00 (213) 827 18SZ Box 11 143 Ror. CA 90292 CABLE DESCRAMBLERS OAK M35B COMBO S33.95 Jerrold, Zenith, Hamlin, Sci. Atlanta, Pioneer & MORE! OUR PRICES ARE BELOW WHOLESALE! CABLE-*- PLUS 14417 Chase a. #481-A Panorama City, CA 91402 1-800-822-9955 * Other Into. 1-818-785-4500 NO CALIF SALES - DEALERS WANTED Hie One Gift That Matches Everything, Can't Be Outgrown And Doesn't Need Batteries. m&rmzs-s t'rzfjszx ii»L«>u:u«.!j;iinji*fiK.\»KBiiijfifc SERIES EE i:ooDniQDO?i:D«. ~ % t%.Z*4" j > CD000000000EE looaaooDooaoii 1 U.S. Savings Bonds are the perfect gift for any occasion. They pay competitive rates and will earn interest for 30 years- guaranteed. For more information, call 1-800 US BONDS. _ CELEBRATE AN .AMERICAN TRADITION . 50 rt ,*., 01 U.S. SAVINGS BONDS A public sc nice of this publication. 05 O z o rr h- o LU O Q < rr 2-1/2" SANYO TWEETER Paper cone with gold tone dust cap. 8 oz. magnet 8 ohm. 1 12" lerro fluid voice coil. Power handling: 50W RMS, 70 W max. Frequency re- sponse: 3K-20KKz. #RD-271-020 \-/ $1"$1™95c tt-BJ .jUr-591 |G0-up| SUPER HORN TWEETER Original piezo tweeter made by Motorola. SPL=94dB2.83V/1M. _ Response: 4KHi- 27KHz. Handles ap- proximately 50 watts. #RD-270-010 S5 30 $4 M $3" rT-Hf (10-7*1 jU^I 2" DOME MIDRANGE Textile dome midrange made by Philips. 8 ohm. SPL=90dB 1W/1M. SOW RMS. 40 W max. Response: 550-SKHz. #RD-280-210 $27™ (1-3| $25" 15" SUBWOOFER Dual voice coil. 40 02. magnet. 6 ohm imp. 100W RMS, 140W max. Response: 20-1.2KHz. Resonant frequency: 21 Hi. SPL=93dB 1W/1M. #RD-290-190 $54* $49 M i*ti« SUBWOOFER XOVER 200W RMS crossover designed specilically For use with dual voice coil sub woofers. 12 dB per octave roli-oH at isriHz #RD-260-220 $28" $24" 10" POLY WOOFER Medium duty. 60 W RMS, SOW max. 1 4 oz. magnet. Response: 25-2. 5 KHz. ls=28Hz #RD-290-096 $18 H > $16 w <1-3) (4-WP1 TITANIUM COMPOSITE TWEETER The advantages of both hard and soft dome technologies. 8 ohm. Ferro fluid cooled voice coil. SPL=90dBlW/1M SOW RMS. 70W max. 4" round. Polydax SDTW100T125. #RD- 270-047 ipiiHV SPEAKER BUILDING BOOK Revised edition of David Weems' best selling book. Learn |o build low cost speakers thai rival Ihe high priced models. #RD-500-Q21 If $16 95 j0P> Parts 340 E. FifStSt., Dayton, Ohio 45402 Local: 1-51 3 222-01 73 FAX: 513-222-4644 * 1 5 day money bat* guaraniea ■ $1 S.oo minimum order • We accepi Masiercarrj, visa. Discover, and C.O.D- orders. * 24 hour s-nipping Shipping chairjo - UPS chart rate +- $1 .00(53.00 minimum charge] Hours S-30 am- 7;QQ pft\ GST, Monday - Friday ■ Mail c«lef custom- crs. please call for shipping estimate on orders exceeding 5 ft» Foreign customers please send SB.ao U.S. funds lor catalog postage, CALL TOLL FREE 1-800-338-0531 12" CAST FRAME WOOFER ^^ t . 12" woofer made in the USA by Eminence. Paper cone and dust cap with treated cloth surround. 80 oz. magnet. 2-1/2" vented voice coil. 8 ohm. 170W RMS. 235W max 40-4. 5KHz response. #RD-290-147 94 CIRCLE 56 ON FREE INFORMATION CARD QUALITY PARTS DISCOUNT PRICES FAST SHIPPING mB ^* i jp desired nuirtoer or digits. Terminates io 1 1 pcplns (i common and 10 poles}. Each section measures .31" wide X .20" high X .78' deep. End plates can be add- ed to form a .94' high bezel. CAT#SWTH-9 $1.25 each 10 for $10.00 I END PLATES CAT* SW-9EC $1.0Q/Set MINIATURE TOGGLE Rated: 3 amps @ 120 Vac S.P.D.T. (ON-ON) P.C. mount CAT»MTS-4PC $1.00 each 1 for $9.00 - 1 00 for $80.00 S.P.D.T. (ON-Oft) sokjerlugs CAT*MTS-4 $1.35 each 101or $12.50- 100 tor $110.00 D.P.D.T. (OttON) solder lugs '^ CAT#MTS-B $1.75 ea. 10 tor $15.00 D.P.D.T. (ON-ON) P.C. mount CAT* MTS-8PC $2.00 ea. 1 for $1 7.50 POWER SUPPLIES 12 Vdc 5 AMP ACDC Electronics * 12N5 or equiv. Input: 1 00-240 Vac (wired for 115 Vac) Output: 12 Vdc @ 5 tupt! Open frame style. 7" X 4 3/4" X 3" high. Regulated. CAT* PS-125 $37.50 each 24 Vdc 2.4 AMP Power-One Inc. *HC-24-2.4 Input: 1 1 5/230 Vac (wired for 1 1 5 Vac] Output: 24 Vdc® 2.4 amps. Open frame style. 5.62" X 4.87* X 2.50" CSA listed. CAT* PS-2424 $30.00 each RECHARGEABLE \ HALL EFFECT SENSOR BATTERIES L.E.D.s E i 6 Volt 1 Amp/Hour Japan Storage Battery Co. Portalac* PE6V1 6 Volt 1 Ah rechargeable sealed lead-add (gell cell), 2" X 1.635" X 2" high. Batteries are prepped with 5" black and red leads terminat- ed with 2 pin connector, CAT#GC-6i $4.75 each 10 tor $42,50 Nickel-Cad "I AAA67ZE $1.50 each 1.2 volts 180 mAh CAT* NCB-AAA AA SIZE $2.00 each 1 .25 volts 500 mAh CAT* NCB-AA AAS1ZE $2.20 each WITH SOLDER TABS CAT* NCB-SAA CSIZE $4.25 each 1 .2 volts 1 200 mAh CAT* NCB-C DSIZE $4.50 each 1.2 volts 1200 mAh CAT* NCB-D HEAVY DUTY "C" YUASA 1800C Nekel-cad heavy duly "C" eel! 1.2 volt, 1800 mah Price reduced on 10 or more, CAT* HDNCB-C 10 tor $42.50/100 tor $375.00 Mlcroswilch*5S41 Tiny, solid state switch j \ reads Instantly to 1 I proximity of magnetic field. Operates at extremely high speeds, up to 100 khz. Case size: 0.12* X 0.1 7" X 0,06" thlck. 4.5 Vdc to 24 Vdc supply voltage. 10 ma. sink type digital output. Operating gauss - 1 5 to 40. P.C. leads. CAT! HESW-3 $1.00 each • 10 lor $9.00 1 00 for $85.00 ■ 1 000 tor $750.00 INSTRUMENT ENCLOSURES ^ High quality molded y-*^ """> AGS instrument enclosures. Integrated PC board standoffs and two sets of vertical mounting slots lor Ironl and rear sub panels. All enclosures are iv wide X 6 1/4' deep. Choice ol three hts. Includes non-skid rubber feet and hardware. Available In beige, ivory, black, and blue. ." • ■ M he. CAT* 21/4" CATKMS-A «7 50«cfi lOfef W5.W 2^S- CAT*iMD-B *7 .75 «dl 10 bf «7 50 y CATHMB-C tBOOoaai 10 tef S70.00 Pktase specify color. RG-11/U VIDEO CABLE 100 ft. or 200 ft, rolls ol RG 1 1AJ 75 ohm cable terminated to heavy duty F connectors. Includes 75 ohm terminator and F-S1 splicer on one end. New cables manufactured for IBM PC networks. IBM PAN 1501908 COM/SCOPE. CAT* RG-iM 100 ft, roll $15.00 CAT* RG -11-2 200ft.roll$27.50 Standard JUMBO Diflused T 1 -3/4 size (5 mm) RED CAT* LEO-1 10 for $1.50- 100 for $13.00 GREEN CAT#LED-2 10 lor $2,00 • 100 for $17,00 YELLOW CAT* LED -3 10 lor $2.00 • 100 tor $17.00 FLASHING LED W/ built In flashing circuit 5 volt operation. T1-3/4 (5mm) ^^^p % RED $1.00 each CAT* LED -4 10 for $9.50 GREEN $1.00 each CAT*LED-4G 10 tor $9.50 YELLOW $1.00 each CAT* LED-4Y 1 for $9.50 LED HOLDER a, rn= PS Experimenters Delight ATARI 5200 Video Game Atari video game controllers returned to the dealer because of various defects. None ol them work properly, but they have lots of great parts. A RF video modulatcr.eighl 1 6X dynamic RAMs in sockets, microprocessors and D-A converters in sockets, two voltage regulators on a heavy-duty heatslnkand lots of other ICs, capacitors, resistors, connectors and other conponent. Does not include the power transformer or controls (joysticks). CAT* A-5200 $7.50 each ■ 2 lor $1 3.50 SOLD AS-IS For Part* Only. Two piece holder. £> & CATiHLED 10 for 65* OPT0 SENSORS | * HOA 0866-N55 TTj U-shaped opto ]\ "-[ sensor. MB" gap. 4pcleads. CAT*OSU-8 75c each TRW* OPB-818 U-shaped opto switch. 0.2* gap between sensor and emitter. CAT*osu-9 75eeach TRW# OPB 822SD Reflective scanner module. U-shaped device with 4 leads each side (8 total) 0,09" gap. 0.75' mounting centers. CAT#OSO-10 75«each TRW* OPB-708 f^. Wedge-shaped / ~ \\ reftectkieopto V^J sensor. u"^ CAT#OSR-5 75ceach iJUiw'-S-W-, L.E.D. FLASHER KIT Two L.E.D.'s flash In unison when a 9 volt battery is attached. This kit includes a p.c. board, all the pans and instructions to make a simple flash, er circuit, A quick and easy project (or anyone with basic soldering skills. CAT*LEDKIT $1.75perklt LE.D. CHASER KIT Build this variable speed led chaser. lOledsllash sequentially at whatever speed you set I hem for. Easy to build kit induces pc board, parts and instructions. Ideal for special lighting effects, costumes, etc. Oper- ates on 3 to 9 volts. PCboaidis5"X 2.25". A great one hour project. CAT*AEC $6.50 each STEPPING MOTOR CONTROLLER KIT Learn about stepping motors while building this simple circuit. Includes circuit board, stepping motor and all pans except 12 Vdc power supply. CAT* SM KIT $18.00 each METRONOME KIT &r^© JK^rfS This simple device can be set to click from 20 to 1,000 beats per minute. Easy io build, include* circuit board, all components and instructions. Oper- ates on a 9 von battery {not included), CAT# METRO *3.75each PHOTO RESISTOR 1 ,000 ohms bright light 1 6K ohms dark. 0.182" dia, X ,08"hlgh. 0.18" long leads CAT#PfiE-7 2 for $1.00 100 lor $45.00 • 1000 for $400.00 7? ORDER TOLL FREE 1-800-826-5432 FAX (818) 781-2653 • INFORMATION (818) 904-0524 Call Or Write For Our Free 60 Page Catalog Outside the U.S.A. send $2.00 postage for a catalog. Minimum Order $10.00 • All Orders Can Be Charged To Visa, Mastercard Or Discovercard • Checks and Money Orders Accepted By Mail • California. Add Sales Tax ♦ Shipping And Handling $3,50 For the 48 Continental United States - All Others Including Alaska. Hawaii, PR. And Canada Must Pay Full Shipping ■ \0£1k Quantities Limited • No C.O.D. * Prices Subject to change without notice. MAIL ORDERS TO: ALL ELECTRONICS CORP • P.O. BOX 567 - VAN NUYS, CA 91408 CIRCLE 107 ON FREE INFORMATION CARD 95 Top Performance GoldStar 20MHz Oscilloscope Global Specialties Protoboard Design Station Features: • 6" rectangular CRT display, internal graticule & scale ■ Phase difference measurements between two signals using X-Y scope or Dual Trace ■ Two different scale probes: x1 and se1 ■ Bandwidth from DC to 20MHz ■ Includes: Two 40MHz probes, two fuses, power cord, operation manual, schematics and block and wiring diagrams ■ High sensitivity: 1 mV/div ■ Two-year manufacturer's warranty GS7020..., $499.95 Jameco Logic Pulser ■ Compatible with TTL. OTL. RTL. HTL. HNIL. MOS and CMOS iCs. ■ 1M!1 Sync input impedance * Pulser mode output currant: 10mA ■ Square) wave current output: 5mA * Audible lone Jameco Logic Probe ■ Max Frequency 80MHz - Minimum detectable pulse: 10ns * 120KI1 input impedance ■ Max. supply vollage: '25V ■ TTL threshold: (l_o).0.8V ±0.1 V (Hi) +2.3V ;0.2V • CMOS threshold: (Ln)30% VCC -10% (HI) 70%VCC -1D% LP540 $16.95 MS104. .$24.95 PROTOTYPING PRODUCTS Jameco Solderless Breadboards ■'jii Dim, Contact BiikJiuci No. L" x W" Point! Posts Price JE21 3.25 X 2.12S 4M $4.95 JE23 S.5x 2.125 830 $5.95 JE24 $.5x3.125 1.360 2 S12.95 JE25 6.5 1 4.25 1.660 3 S17.95 JE2G 6.875 X 5.75 2,390 4 S22.95 JE27 7.25x7,5 3.220 4 S32.95 .1 1AM IEC ;< 24 Hour Order Hotline (415) 592-8097 Metex Digital Multimeters General Specs: ■ Handheld, high accuracy ■ AC/DC vollage, AC/DC currenl, resistance, diodes, continuity, transistor hFE ■ Manual ranging w/ overload protection M3650 S M4S50 only: ■ Also measure frequency and capacitance Ma 650 only: ■ Data hold switch ■ 4.5 digil M361Q 3 5Digil!Mlimo1er..... $59.95 M36.50 3 .5 Digil MuMnwIti w. Frequent) i Capaolaiw S74.95 M4650 : : Digit w/Frsqusncy. CapacitarKK and Data HoM Smith $99.95 Features: • Ideal for analog, digital and microprocessor circuits ■ Triple DC regulated power supplies, +5V, +15V. -15V ■ 8 logic indicators • Two debounced push-button switches • Function generator with sine, square, triangle and TTL waveforms ■ Includes power supply, instrumentation and breadboarding PB503 $299.95 A.R.T. EPROM Programmer ■ Programs all current E PRO Ms in in e 2716 to 27512 range plus the X2864 EEPROM ■ RS232 port - Software included EPP UVP EPROM Eraser r ■ Erases ail EP ROM's ■ Erases 1 chip in 15 minutes and 8 chips in 21 min ■ UV intensity: 6800 UVWCM 2 .$199.95 DE4 $79.95 EPROMs - for your programming needs Part No. Price Handheld Multimeter ^M FAX; (415) 592-2503 (415) 595-2664 * Partial Listing • 3.5 dign LCD with automatic polarity indication ■ ACfOC vollage measurement up to 5G0 ve-Hs - AC'OC currenl measurement up to 20GmA • Resistance measurement up lo 20Mli • Con- tinuity checker with audfote tone ■ Diode and logic tesier * Autortnanual range and data hold Funclions * All range protection and Junction in- dications DMM905 $39.95 XY999 TMS2516 TMS2532-35 TMS2532A TMS2564 TMS2716 1702A 2708 2716 2716-1 27C16 2732 2732A-20 2732A-25 2732A-45 27C32 $4.25 9.95 7.95 5.95 5.95 3.95 4.95 3.49 3.95 4.25 4.95 3.95 3.49 2.95 3.95 Part No. Price Part No. Price 2764-20 2764-25 2764-45 2764A-20 2764A-25 27C64-15 27C64-25 271280TP 27128-20 27128-25 27128A-15 27128A-20 27128A-25 27C1 28-15 27C1 28-25 $3.95 3.75 3.49 3.95 3.25 3.95 3.25 2.95 6.95 4.95 5.95 4.49 4.25 5.95 5.75 272560TP 27256-15 27256-20 27256-25 27C256-15 27C256-20 27C256-25 2751 20TP 27512-20 27512-25 27C512-15 27C512-20 27C512-25 27C010-15 68766-35 $3.75 5.95 5.25 4.75 5.95 4.95 4.49 4.95 6.95 5.95 6.95 6.49 5.95 11.95 9.95 Soldering and Desoldering Stations 60 Watt Analog Display Soldering Station ■ Electronic temperature control from 200° to 878° F • Cartridge heat- ing element for a longer life of the soldering tip XY1683 $69.95 30 Watt Electronic Temperature Controlled Desoldering Station ■ Electronic temperature control from 212" to 842°F ■ Self contained high rotary vacuum pump .$299.95 Over 4000 Electronic and Computer Components in Stock! CIRCLE 114 ON FREE INFORMATION CARD Widest Selection n <*<£&!# X0<& av\<* £\etf Assemble Your own Computer Kit! Jameco 16MHz 80386SX Desktop Computer Kit Building your own computer provides you with a better understanding of components and their functions In-depth assembly instructions included Have your new computer assembled and running in an evening. using common tools Software included Purchase computer kits configured by Jameco or design your own Jameco 1 6 MHz 30386SX Desktop Computer Kit Includes: ■ 80386SX Motherboard with 2MB RAM (expandable to 8MB) ■ 101-key enhanced keyboard ■ Multi I/O Card ■ Toshiba 1.44MB, 3.5" DSHD floppy disk drive ■ Baby sized desktop case ■ 200 Watt power supply ■ DP, DOS 5.0 by Digital Research and Oiagsoft's OAPIus diagnostic software .95, ram** <"' Hard Drives Conner (16-bit IDE) C P3044 4 5MB 3.5' Low Profile $469.95 CP3184 BOMB 3.5'HH $649.95 CP3104 1 00MB 3.5'H H S699.95 A DP30 Host Adapter. $29.9 5 Relisys 14" VGA Color Monitor • Max resolution; 720 x 480 ■ Bandwidth: 30MHz * Input: DB1 5-pin (analog) RE9513 ..S449.95 Jameco 16-bit VGA Card ■ Supports VGA, EGA. CGA, MDA and Hercules modes • Comes with 256KB video FtAH upgradable to 512KB (eight 4 1464 -BO) • Capable ot 640 x 480 with 256 colors, BOO x 600 wild 1 6 colors VG2000 $149.95 Integrated Circuits Part No. 1-9 10+ Part No. 1-9 10+ 74LS00 $.25 $.15 74LS154 $1,29 $1.19 74LS02 .25 .15 74LS1S5 .49 .39 74LS03 .29 .19 74LS156 .49 ,39 74LS04 .25 .15 74LS157 .45 .35 74LS05 .28 .18 74LS158 .39 .29 74LS06 .59 .49 74LS166 .79 .69 74LS07 .59 .49 74LS169 .99 .89 74LS08 .28 .18 74LS173 .49 .39 74LS10 ,25 .15 74LS175 .39 .29 74LS11 .29 .19 74LS181 1.39 1.29 74LS13 .35 .25 74LS189 3.95 3.85 74LS14 .49 .39 74LS190 .59 .49 74LS20 .28 .18 74LS191 .59 .49 74LS21 .29 .19 74LS193 .69 .59 74LS27 .35 .25 74LS194 .59 .59 74LS30 .28 .18 74LS221 .69 .59 74LS32 .28 .18 74LS240 .59 .49 74LS38 .35 .25 74LS241 .59 .49 74LS42 .49 .39 74LS323 74LS541 2.49 2.25 74LS47 .85 .75 1.09 .99 74LS48 .85 .75 74LS590 5.95 5.75 74LS112 .39 .29 74LS670 .89 .79 74LS122 .55 .45 74LS688 2.19 1.95 74LS123 .49 .39 81LS95 .99 .89 74LS125 .49 .39 81LS97 .99 .89 Miscellaneous Components Potentiometers Values available (insert ohms into space marked "XX"): 500K, 1K, 5K, 10K. 20K. 50K, 100K, 1MEQ 43PXX 3 u Watt.15 Turn $.99 63PXX V2Walt, 1 Turn $.89 PN2222 PN2907 Tra $.12 12 10 25 nsistors And Diodes 1N4735 $.25 2N4401... 2N3904 12 : 1N4U8... ...$.15 07 1N40D4 1N751 15 I2N3055... 69 2N2222A .. C106B1 ... 49 1N270 25 Switches JMT1 23 SPDT, On-On (Toggle) ,.....$1 .25 206-8 SPST, 16-pin (DIP) $1.09 MPC121 SroT.OnOlt-OnfToggte) ...$1.19 MS102 SPST. Momentary (Push-Button) $.39 .$.39 D-Sub Connectors and Hoods DB25P Male. 25-pin $.65|DB25H Hood.. DB25S Female, 25 -pin... $.75 1 LEDs XC209RTl.(Red) $.14 XC5S6R T1 3 ,'*, (Rett) ...$.12 XC556GT1 3 j. (Green) ...16 XC556Y T1 3 *. [Yellow). ..16 Low Profile 8LP... 14LP. 16LP. 24LP. 28LP. 40LP. IC Sockets Wire Wrap (Gold) Leval *2 8WW S.49 14WW 65 16WW 69 24WW 1.05 28WW 1.29 40WW 1.79 ..$.11 ....12 ....13 ....19 ... .22 ... .28 24 Hours A Day! J AMECO 24 Hour Order Hotline (415)592-8097 FAX: (415) 592-2503 (415)595-2664 1355 Shore way Road Belmont, CA 94002 Look to Jameco • Wide selection oi integrated circuits and components • Quality prototype and test equipment • Computer kits and accessories Additional items that Jameco offers: ' Tools ■ Cables ■ Connectors • Data Books ■ Motherboards • Memory • Math Coprocessors • Computer Accessories ■ Power Protection Equipment ■ Much, much more ! Let us show you what we have to offer, call ot write for the latest Jameco catalog! $50.00 Minimum Order Dala Sheets - 50c each For a FREE 90-Page catalog send 52.00 to cover first Class Postage and Handling 01691 Jameco Electronics 4^91 CA Residents Add 6.00%. 6.50% or 7.00% Sales Ta* Shipping handling and insurance are additional. [Costs may vary aocot ding 10 weight and shipping method) Terms: Prices subject to change without notice. Items subject to availability and prior sale. Complete list of tetmnwajranties Is available upon fBQuMl ISM «* 'Wfttvn! tredtmartel Intrnater.*! Bu»nn» UtetMW VISA mmc 'Jhjji'LjifJ Q$ <^k Soldertail Standard & Header Plug Sockets Also Available ■ Customer Service 'Technical Assistance • Credit Department • All Other inquiries ■ (41 5) 592-8097 CIRCLE 114 ON FREE INFORMATION CARD Please refer to Mall Key 2 when ordering 7AM-4PMP.S.T. THE ELECTRONIC GOLDMINE Ttii Elittrenfc EoM'mtiw tes one d Sic greeted se- lectora d utiiojje dftfraric Vit avalatte in the woridf We hMDifl 130 kits and tua 1.-*00 unique, bargain priced, cavpooc--^ il DOT ^ijlC^ INEXPENSIVE GEIGER COUNTER KIT ProtBdy (He taest price* GeJQer coiner Id a-atole in bk waru bday! f eaues sensUrve thin waited Gefr Mm.er tube aid p«Mfcdric speaker that em'te dicks in prcpodion to !ne radMion feyet Octtcs Beta and Ganinq lays Wit dew radium dials on Did waldies, decks, batkgroijnf) rasalian, nudes ranoui, at Only 3**1^3*. DKnmfrom one JW battery {nd induded). Complete with all patt. PC board and instrudons, C6447 $39.95 4KV TRIGGER COIL Um wlh any stobe V^ tube md needs a \. ^L 3 tod IKY trigger V^ N1700 $1.25 EA. 100 fc* $80.00 iNVLiitLk TRANSFORMER (£« Small A teas Karefarraf "Ti 1 3r jh with 565 IC 10 COnVQl 12VK » 2S0V taf saroW ■'iiffDisi lutes with sdwratc NJ703 S2.00 EA 1.000 la & 1,500 PLASTIC ZIPPER CLOSE BAGS VfeiiowrtfrfrrjhaditYZMiiHiia ripper eioa toQj win while fctori to w&e en. These re- #Q5«t* bags tolm a ripper frrttirifj lop for Kinvenie.n| str^e ol small e'effrtn;; parts, lunftore, etc. We have the 1ollB*ieg sizes. Sen In rniftigles ti 100 orty 2" X 3" G663 100/$3.30 3 M X 4" G6&4 100/$3.75 3" X 5" G$&5 100/$4,00 4" X 6" G666 100/$5.50 RAEtF. I-AEHTt Strai MAGNETO Mjny brnes stronger ihan slit /^"""v rrcends, these art the worlds ifZ" ^5 mionets tor Lhis size. Small s°jb tflty ^ abMfl "l" x5W k IjE" J« can lilt 12 Ki IS i&s. Try to remove this magnsi from a steel stale art jcu'Ji find Ihi uriss you s-fidb H, yoti canH uet Ji gff_ Greai lor Kiousands d egerimenis and appiicaHiOK. (formally these sen lor £30 each, bti these are SLfrAis and have a few soct*es (nos not. etieci pertDimance}. qq^q $h qq MINERALIGHT BLACKUGiTT LAMP Pcrtabie shod wave mineral «rjhi ma*tyUVP. Mow UVG-i na- tures ijlly pcrlac* aperMnm tram four AA batteries {not induced). Tr :-s ■ ^i is mgrjed ami tas [he tjnaus 5C00 hoir £W Raisrlo cause ticure^ceni minerals to glow origffly, GB12 529.95 MINIMUM ORDER; $1 DC gjta $3 00 stirp^iing anil tiandling Wi? acoqpl MC, Visa and Money Cwdeffi SEND ORDERS TO: The Eleciiraiic Goldmine P.O. Box 5J0fl Sffltlsflale. A2 BS!61 PHONE ORDERS (602) 491-7454 FAX ORDERS (602) 451-9495 CIRCLE 176 ON FREE INFORMATION CARD ADVERTISING INDEX RADIO-ELECTRONICS does not assume any responsibility for errors that may appear in the index below. 05 g z o £E P- O LU —I EB 6 Q < DC 98 SAVE MONEY. DON'TRENT! CABLE TV DESCRAMBLERS, CONVERTERS, & ACCESSORIES. Save hundreds of dollars owning instead of renting from the cable company. Easy to order and install. Name brands — Pioneer, Oak, Panasonic, jerrold, Scientific Atlanta and more. We're famous for lowest prices, excellent service and immediate delivery. All products fully warranted. Your satisfaction is 100% guaranteed. CALL FOR FREE FULLY ILLUSTRATED i 6-PAGE COLOR CATALOG. 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Electronics 91 Microprocessors Unltd 86 NRI Schools 21.83 NTE Electronics 7 Optoelectronics 13 Parts Express 94 Perfact Cable 89 Radio Shack 3 179 SCO Electronics 62 189 Sencore CV4 — Star Circuits 25 — TEC) 79 92 Tektronix II — The SPEC -COM Journal 70 187 Unicorn 93 188 Vicjo Publications 42 180 U.S. Cable 62 177 WPT Publications 79 — Wholesale Cable 92 178 Xandi Electronics 77 ADVERTISING SALES OFFICE Gernsback Publications, Inc. 500 -B Bi -County Blvd. Farmingdale, NY 11735 1(516) 293-3000 President: Larry Stickler For Advertising ONLY 516-293-3000 Fax 1-516-293-3115 Larry Steckler publisher Arline Fishman advertising director Denise Haven advertising assistant Christina Estrada advertising associate Kelly McQuade credit manager Subscriber Customer Service 1-800-288-0652 Order Entry for New Subscribers 1-80Q-999-7139 7:00 AM - 6:00 PM M-F MST SALES OFFICES EAST/SOUTHEAST Stanley Levitan, Eastern Sales Manager Radio-Electronics 259-23 57th Avenue Little Neck. NY 11362 1-718-428-6037, 1-516-293-3000 Fax 1-718-225-8594 MIDWEST/Texas/Arkansas/Okla. Ralph Bergen, Midwest Sales Manager Radio- Electronics 540 Frontage Road— Suite 339 Northfield, IL 6O093 1-708-446-1444 Fax 1-708-446-8451 PACIFIC CO AST/Mountain States Marvin Green, Pacific Sales Manager Radio-Electronics 5430 Van Nuys Blvd. Suite 316 Van Nuys. CA 91401 1 -81 8-986-2001 Fan 1-818-986-2009 Countersurveillance Never before has so much professional information on the art of detecting and eliminating electronic snooping devices— and how to defend against experienced information thieves — been placed in one VHS video. If you are a Fortune 500 CEO, an executive in any hi-tech industry, or a novice seeking entry into an honorable, rewarding field of work in countersurveillance, you must view this video presentation again and again. Wake up! You may be the victim of stolen words — precious ideas that would have made you vety wealthy! Yes, profes- sionals, even rank amateurs, may be lis- tening to your most private con- versations. Wake tip' If you are not the victim, then you are surrounded by countless vic- tims who need your help if you know how to discover telephone taps, locate bugs, or "sweep" a room clean. There is a thriving professional service steeped in high-tech techniques that you can become a part of! Bur first, you must know and understand Countersurveilance Technology. Your very first insight into this highly rewarding field is made possi- ble by a video VHS presentation that you cannot view on broadcast television, sat- ellite, or cable. lr presents an informative program prepared by professionals in the field who know their industry, its tech- niques, kinks and loopholes. Men who can tell you mote in 45 minutes in a straightforward, exclusive talk than was ever attempted before. Foiling Informarion Thieves Discover the targets professional snoopers seek out! The prey are srock brokers, arbitrage firms, manufacrurers, high-tech companies, any competitive industry, or even small businnesses in the same community. The valuable informa- tion they filch may be marketing strat- egies, customer lists, product formulas, manufacturing techniques, even adver- tising plans. Information thieves eaves- drop on court decisions, bidding information, financial data. The list is unlimited in the mind of man — es- pecially if he is a thief! You know that the Russians secretly installed countless microphones in the concrete work of the Amet ican Embassy building in Moscow. They convetted CALL TOLL FREE 1-800-522-6260 HAVE YOUR VISA or MC CARD AVAILABLE what was to be an embassy and private residence into the most sophisticated re- cording studio the world had ever known. The building had to be torn down in order to remove all the bugs. Stolen Information The open taps from where the informa- tion pours out may be from FAX's, com- puter communications, telephone calls, and everyday business meetings and I unchti me encounters. Businessmen need counselling on how to eliminate this in- formation drain. Bask telephone use cou- pled with the user's understanding that someone may be listening or recording vital data and information greatly reduces the opportunity for others to purloin meaningful information. RADIO- ELECTRONICS VIDEO OFFER RE WO-B Bi-Counry Blvd. Farmingdak, NY 11731 Please rush my copy of the CournersurveillajKc Techniques Video VHS Cassette for $49.95 plus J-1.00 fot postage and handling. No. of Cassettes ordered Amount of payment % Bill my □ VISA □ MasierCatd Card No. Expire Dace /, Signature . Name Address City . State . . ZIP . All payments in U.S.A. funds. Canadians add $1.0n pet VHS cassette. Mo fotcign orders. New York State residents add applicable sales rax. The professional discussions seen on the TV screen in your home reveals how to detect and disable wiretaps, midget radio-frequency transmitters, and other bugs, plus when to use disinformation to confuse rhe unwanted listener, and the technique of voice scrambling telephone communicarions. In fact, do you know how to look for a bug, where to look for a bug, and what to do when you find it? Bugs of a very small size are easy to build and they can be placed quickly in a matter of seconds, in any object or room. Today you may have used a telephone handset that was bugged. It probably contained three bugs. One was a phony bug to fool you into believing you found a bug and secured the telephone. The sec- ond bug placates the investigator when he finds the real thing! And the third bug is found only by the professional, who continued to search just in case there were more bugs. The professional is not without his tools. Special equipment has been de- signed so that the professional can sweep a room so that he can detect voice-acti- vated (VOX) and remote-activated bugs. Some of this equipment can be operated by novices, others require a rrained coun- tersurveillance professional. The professionals viewed on your tele- vision screen reveal information on the latest technological advances like laser- beam snoopers that are installed hun- dreds of feet away from rhe room they snoop on. The professionals disclose that computers yield information too easily. This advertisement was not written by a countersurveillance professional, but by a beginner whose only experience came from viewing the video tape in the pri- vacy of his home. A fret you review the video carefully and understand its con- tents, you have taken the first important step in either acquiring professional help with your surveillance problems, or you may very well consider a career as a coun- tersurveillance professional. The Dollars You Save To obtain the infotmation contained in the video VHS cassette, you would attend a professional seminar costing $350-750 and possibly pay hundreds of dollars more if you had to travel to a distant city to attend. Now, for only $49-95 (plus $4.00 P&H) you can view Countersur- veillance Techniques at home and take refresher views often. To obtain your copy, complete the coupon below or call toll free. Introducing a new companion to your VA62A Universal Video Analyzing System! Isolate All Playback Or Record Problems In All VCRs . . . Now And In The Future, Or Your Money Back! VA62A Universal Video Analyzer VC93 All Format VCR Analyzer Patent Pending Now you'll have everything to completely analyze all VCR RF, video, audio, and servo problems. 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