J'iiSJiUDIII AUGUST 1992 a ii it ^ a uj ttm Combined with Bring the soothing sound of ocean waves wherever you go! ^1 ML;{di[/ai 1 1 Boost the output of your low-power transmitter with our linear amplifier r S3.50 U.S. 1 GERMSBftCX S3.95 CAN ^ --'s^oic^. xnxttjx UAN-Hi m\ mis r5D456HRR5I65rf053 OS NOU S RE We Only Skimped OnThe Price. Introducing The Fluke Series 10 — From $69.- Actuaf size: Easy to carry, easy to use Hew! V Chek'*: For fast accurate ctiecks on power sources and supplies, set your meter on V Chek— and let it do the rest. V Chek will determine continuity/ohms; it voltage is present, jt BUtorfjatlcaify ctrange modes to measure AC or DC volts, whichever is detected. For most initial troLibleshootintj ctiecks, here's the only setting you need to make. Fluke quality: Made in the USA by Ffuke, with the same rugged reliability that's made us the world leader in digital multimeters. Count on hard-vjorking high performance— and a two-year warranty to back it up. LarQe, easy-to-read display: 4000 count digital readout. Audible Contlntilty; To perform tast continuity checks, just listen tor the beep; no need to watch the display, New! TL75 Hard Point^" Test Leads: Comfort grip \vith extra strong tips for extended service life. Newf Mln/IVlax record with relative time stamp and Continuity Capture'": Makes intermittent problems easier to find. Records highs and lows— and lime stamps'" when they occurred. In continuity mode, opens or shorts as brief as 250 ^is are captured and displayed. Capacitance: Autoranging from .001 LiF to 9999 ^fo need to carry a dedicated capacitance meter. For high performance at Fluke's lowest price, get your ham^s on the new Series 10^ Slop by your local Fluke distributci and feel what a powerful difference the right multimeter makes— at the rip hi prrce. For a free product brochure or the name ofyour nearest distributor, call l-aOO-BT-FLllKE. C04JH! digiTJl display 1,5% basic dcvotjs accuracy 29% basic Visits accuracy 1 5% bask: ohrns accuracy Fast continuity beer^er Dlod«Tesl Tw&-year warrantv S7'9.95' VCneSi'*' Capacitance; -Oet 10 9999 iiF 40O0 coutiidipitaJ display 0.9i% basic dc VQtiiS accuracy 1.9% basic ac volts accuracy 0.9^^ basic obms accuracy Fast CQntirtuity bficper Slesp Mods Two-year v^ar rarity Ffuhfl 12 VChek'*' Min/fJiiJt. rfcordcng with relative time scamp Conlmnily Caplure-" Capacitance. .001 (0 9909 4000 Cdurit di^jitaE display D,9':« basic dc vol!$ accuracy lO^&asic ae vpMs accuracy 0.9% basic ohms accuracy Fas! continuity beeper Diode Test Sleep Mode Two-year v^arranty 'SuQoesLed U.S. list ptice The New Series 10. A Small Price For A Fluke* FLUKE AN [> PHILIPS THE T 6i M ALLIANCE ©1991 Jobn Fluite W(g. Co., Inc. Prices and specifications 9Ub|ecT ^ cbango. Ad no. 00130 CIRCLE 121 OK FREE INFORMATION CARD August 1992 Ekctmics Vol. 63 No. B 33 SURFMAN Recreate the relaxing sound of the sea. John Siinonton 37 TELEPHONE SCRAMBLER Keep your confidential phone conversations private! Dan Rosen mayer 67 ATV LINEAR AMPLIFIER Boost the output of an amateur televtsion transmitter from 2 to 10 watts! Rudolf F. Graf and William Sheets PAGE 37 44 OPTOCOUPLER DEVICES Using optocouplers in circuits thatrequfra high isolation between input and output Ray M. Marston 55 NOTWORKING TO NETWORKING The first in a series on troubleshooting local-area networks, Gary McClellan 60 PC-BASED TEST BENCH Build an A/D converter that can be used as a low-frequency oscilloscope. Steve Wolfe FROM I i^TVUORKIND PAGE 55 12 VIDEO NEWS What's new in this fast- changing field. David LaohenbrucK 27 DRAWING BOARD Exploring the mysteries of video scrambling. Robert Grossbiatt 22 EQUIPMENT REPORT 73 HARDWARE HACKER FM antenna-range contest, and more, Don Lancaster 81 COMPUTER CONNECTIONS A user manifesto. Jeff Holtzman 98 Advertising and Sales Offices 98 Advertising Index 14 Ask R E 87 Buyer's Market m 4 Editorial 12 Letters E S 30 New Lit z 24 New Products i 6 What's News 1 I Do you often find yourself dis- tracted and irritated by the noisy sur- roundings — barking dogs^ scream- ing kids, droning lawn mowers, beeping horns, bone-shaking con- struction work, blaring music? One simple solution ts to replace that an- noying noise with one that is soothing and relaxing. You can do just that with theSurFMan, a pocket- sized gadget that lets you fisten to the sounds of the sea through Walk- man-style headphones, whether you're at the shore or stuck in the office. The Surf Man surrounds you with the rhythmic sound of waves crashing on the shore, while drew- ing out the noisy sounds of the real world. For construction details, turn to page 33. THE SEPTEMBER ISSUE GOES ON SALE AUGUST 2. BUILD A DSP VOICE-EFFECTS BOARD Use digital signal processing to alter your voice. WOTWORKING TO NETWORKING Basic and advanced equipment for troubleshooting LAN's. PC-BASED TEST BENCH Build an IC tester and Identifier. ATV DOWNCONVERTER Use a standard TV receiver to view amateur TV signals. CIRCUIT COOKBOOK Learn — or re-learn — how to use the 555 timer. As 2 scrvjuc to rejsdcrs, ELECTDONICS NCW pubtishes available pbns or infomiiiUoii rePstidg to newsworthy pnidircis, teciiniques itnd scientific and techfJGlo^itaE rfeveropments. B4caus« d possibEt variancM m the quali^ty and condition tjf mate:ri3E» ;ind morion EinsKip used by readiars, EL^CTHONICS NOW cfrsctalms any rt^ipfitlhWitf for tlie safe and proper fijocSOfiirh5 of reader' built projects based upon or From pluns or Mformflliort pub fished in this mag^ine. Since some q# tho equipment and circuitry described in ELECTRONICS NOW may rotate ta or be covered by U.S. pa Lenta , ELECTRONICS UON di^olatms any liability for tho infringemsnt of such patents by the n^nking, Uftng. or melting of any such aquipm^nt or circuilry, end suggo&ts Lhat anyone Fnte^-ested in f uch piojects consult a patent a tloroeyr ELECTRONICS HON, (ISSN 0033-7 &&2J Auqust Published monthly by Gern aback Publications. Inc., SCMD B ei Countv Boulevard. FarmingdaCe. NV 1173S. Second-Cla»$ Postage paid at Farmmgdale, NV and jtddrUonal maiEing cKicos. Second- Ct^ss rnait registralion No. R12S1 6^260, Aulhoriied at Toronto, Caionda. One -year subscnptJon rale U.SA. arid possessions $19. Caoada S27 79 ^includ^s G ST. Canadian Goods iin4 Services Tax Registration No. RI251G&2S0}. ttH other countries $2B. Afl Siuhscnptron orders payable in U-S A. 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Hol^man computer editor Robert Gros&blatt, circuits editor Larry KleJii« audio editor David Lachonbruch contributing editor Don Lanoa$te'r contributing editor Kalhy Terend, editorial assistant ART DEPARTMENT Andre Duzant, art director InjaB Le«, illustrator Rusfiell C. Truetson, illustrator PRODUCTrON DEPARTMEISIT Ruby M. Yee, production director Karen S, Brown odvcftising production MarceMa Amoroso production assistant Lisa B^chovtfitz editorial production CIRCULATION DEPARTMENT Jacqueline P. Cheesoboro circufation director W#ndy Atanko circulation analyst Theresa iombardo circulation assistant Michele Torrillo, reprint bookstore Typography by Mates Graphics Cover photo by Otversified Photo Services Eleotronics Now is indexed In Applied Science & Technology index and Renders Gwd6 to Penodhat UteT" Mj^crofllm & Microfiche editions are availalile. Contact circulation depart- ment For details. Advertising Sales Offices listed on ivage Electronics Now Executive and Administrative Offices T-516-293-3000. Subscriber Customer Service: t -800 -286-0652. Order Entry for Nevv Subscrit>ers: 1.800999-7139. Audit Buresi-t of Circufattons Member Releass Your Imagination Expsriencs the POWER oF Electronics with TAB/l^cGrBw-Hill, Inc. Includes an Index to all four volumesl ENCYCLOPEDIA OF ELECTRONIC CIRCUITS— VOLUME 4 Tufn riere fOf me latest ctrcustry used in com- pyier$, controls, insirumentation, leJecoiri' munhcalions, sensofs, and more. You gel over 1Q00 4- all-new circuits xhat answer your ques- tions on modem circuit desrgn. Savp 22^ — Get thotr«ands of circuits Qfici project lde« In Vols. 1> 2 and 3 {nB4B9C\ for only $t39.95 [regularly PRACTICAL ANTENNA HANDBOOK Design, build, ajid insialt anterrnas (o sua your n^ods — and save money] Build a variety of anien- nas. including: high-ff&quency dipote, shortwave, microwave, mobile » VHF and UHF transmitting, directional beam, marine radio, muUi-band, and more. Jispp , Jir tfftjs. *i3270H, *32.9S THE RADIO AMATEUR'S DIGITAL COMMUNICATIONS HANDBOOK You get tips and McH on how lo ' dsllngutsh various models * understand Iho different melhods of modulation used • and set up a com- munications workslation that fits your needs— and budget. 206 pp., mmji. #^2H. $22.91 PROGRAMMABLE CONTROLLERS: Hardware, SoHware, and Applications Vou get delatis on; hew PLCs are used . . types of hardware and sofiwara . . . high- and low-l^vel pro- gramming Languag:es . . . iniorfacing PLCs iftfith peft- pharals. . . and creating networks of PLCs. 30-< pp. fs? iHut. t3i47H, »a.as MICROWAVE OVEN REPAIR —2ND ED, Service tow'snd high-vglt^g^ problems * locale and replace the magnetron • repair oven motors and controJ clrcutis • and test for microwave leakage. Includes diagrams and case hi stories for many ot the popular brands of microwaves. 36Spfi , 3SStffus. «3457H, $29.95 SECRETS OF RF CIRCUIT DESIGN Design and buitd your own radio fretime ALHoran^tmg, Dolaypd sweep ar>d Trip(jer Lock u&ir^g a &-inch CRT.V^ dofll feeJ ti^e com^jaaness in iiuS..l ,S% basic accy. Zeroconlrol w/'Caio Digital LCR Meter LC'IBOI SI 25 Mflasuresi Coils luf^-200H Caps ,1pl'MClyf Res Ot-20M Muthrmter witti Copocitonce ft Tfonslstor Tester $55 CM-15D0B Raads VollE, Ohm Cutienl, Capdcilors, Trfirt5(Sl0r$ and Dig ttte speed of \hB moto^. t^e kit comes compfeie with 2 rtiDlors, 2 f rooi surface mirrors, 2 tnalor brackets and 1 power rheostat COntro I to vary speed ol the motor. Model lM-1 $19.95 WE WILL NOT BE UNDERSOLD UPS SHIPPING^ 48 STATES ILRES 7.5% TAX ($3 mi n SI 0 max) OTHERS CALL C&S SALES INC. 1245 ROSEWOOD, DEERFIELD. IL 60015 FAX: 708-520-0085 • (70S) 541-&710 15 DAY MONEY BACK GUARANTEE 2 YEAR WARRANTY WRITE FOR FREE CATALOG PJ^iCfS SUBJCCT lO CHANGE CIRCUE 109 ON FREE J^FOFIMATION CARD If Ybu'ie Serious ^ About a Future in Electronics, Ensure that Future with the Best Educational Ik'aining ^ Available. t L you want to fearn about electron- ics, ancJ earn a gooci income with that knowledge then CI E is your best edycatronaJ value. CfE s reputation as the woftd leader In home study eiectronics Is based sorely on the success of our graduates. And we've earned that reputation with an unconditional commitment to provide our students with the very best electronics training. Just ask any of ihe ISO/OOO-plus graduates of the Cleveland Institute of Electronics who are working in high^paying positions with aerospace, computer, medical, automotive and communi- cation firms throughout the world. They N tell you success didn t come easy. ..but, it did come..., thanks to CiE, And today^ a career in eiec* tronics offers more opportunities and greater rewards than ever before. CfE s COMIVinTED TO BEING THE BEST,..JN ONE AREA.,..ELECTRONICS. CIE isn t another be-everything-to- everybody school. We teach only one subject and we believe we're the best at what we do. Also, CIE is accredited by the National Home Study Council. And with more than a 1,000 gradu-^ ates each year, weVe the largest home study school specializing exclusively in electronics. CIE has been training career-minded students like yourself for nearly 60 years and we're the best at our subject ..... ELECTRONICS ... BECAUSE ITS THE ONLY SUBJECT WE TEACHJ CIE PROVIDES YOU WITH A LEARNING METHOD SO GOOD, rrS PATENTED- OE's Auto^rog rammed lessons are a proven learning method for building valuable electronics career sNilts, Each lesson is designed to take you step-by- step and principle-by-principle. And while all CIE lessons are designed for independent study, ClE's instructors are personally available to assist you with just a toll- free calL The result is practical training... the kind of ex peri* ence you can put to wortc in today's marketplace. LEARN BY DOING,..WrTH STATE-OF- THEWrr FACILTTIES AND EQUIPMENT. In 1969, CIE pioneered the first Electronics Labora- tory course and in 1 984, the first Mircoprocessor Laboratory course. Today, no other home study school can match CIE s staie-of-the-art equip- ment and training. And all your ist}Qratory equipment, books, and lessons are included in your tuition, fts all yours to use while you study at home and for on -the -job after graduation. PERSONAUZED TRAfNfNG»,TO MATCH YOUR BACKGROUND. While some of our students have a working knowledge of electronics others are just starting out. That's why we've developed twelve career courses and an A^S. Degree program to choose from. So, even if your not sure which electronics career is best for you, CIE can get you started with WHY CHOOSE CJ£ FOR YOUR TRAJilfNG? • 1 50,000 successful graduates from every country around the world, ■ Only CIE rewards you for fast study. CIE offers an Associate Degree program based on actual study time used. The faster you complete your degree the less your overall tuition. ■ Stateof-t he-art laboratory equipment is yours to keep and it comes assembled, ready for handsK>n experlments- ■ Approved for educational benefits under the G,l, Bill for veterans and other eligible persons. ■ Upon graduation, CIE offers free preparation to pass the CertiFred Electronics Technician Exams, core lessons applicable to all areas of electronics. And every CIE course you take earns you credit towards complex tion of your Associate in Applied Science Degree, So you can work toward your degree in stages or as fast as you wish. In fact CIE is the only school that actually rewards you for fast study, which can save you thousands of dollars. SEND TODAY FOR YOUR CIE COURSE CATALOa AND WE'Ll SEND YOU A FREE 24 PAGE CIE ELECTRONICS SYMBOL HANOBOOKI □ YESf I want to get started. Send me my CIE school catalog includ- ing details about the Associate Degree Program. (For your convenience, CIE will have a representative contact you - there is no obligation J AE41 Name: _ , Address:. City:. .State: Zip .Age: Phofie Nq. f I ^_ _______ Check box for G.l. BuHctirk Bor^litS ' Veteran Active Duty CLEVELAND INSTITUTE OF ELECTRONICS 1776 East :7th Street Clevclarnj, Ohio 44114 (216) 7ai-94DQ Allans one VIDEO NEWS Whats new in the fast-changing video industry. DAVID LACHENBRUCH * Ghostbuster ootriFiromlse- Theres peace at last \n the ghost- busting arena. Developers of the two leading systems have gotten together and merged their systems into one that should satisfy the needs of broadcasters and cable operators alike — as v^ell as viewers plagued with ghosting problems. Tests by the Nationai Association of Broadcasters CNAB) had found the ghost-canceling system developed by Philips to be superior, but a rival system by the David Sarnoff Re- search Center and backed by Thomson Consumer Electronics was favored in tests by Cable TV Laboratories CRadio-Elec- tronics, July 1992). The Philips system performed better in eradicating the widely spaced ghosts generally found in broadcast signals . while Sarnoffs technology did better with the more ctosely spaced ghosts developed wtlhin cable systems. In a model cooperative effort, both proponents got together and developed a third system that combines the best ele- ments of both. The ghost-cenceling system uses a reference signal transmitted during the vertical blanking interval to direct specially equipped receivers to eliminate ghosts. Ghost-canceling circuits are expected to add at least $100 to the cost of TV sets, and will be mar- keted for the current NTSC system. HDTV sets are expected to use a different method of dealing with ghosts, ^ Starrdards -con verting VCfl*s. An answer to a common question— how to swap tapes with friends and relatives in countries with different TV standards— is in sight. Aiwa, which has been out of the video field in the U.S, for several years, this summer will start mar- keting a reasonably priced VCR that can play NTSC tapes on PAL re- ceivers and vice versa. The stan- dards-converting VCR will carry a suggested list price of about $500 — far below previous stan- dards converters— and is sched- uled to be available this month. At the same time, Aiwa will offer a stand -alone standards converter, that will adept any tape or videodisc to a different standard, at $400. That model has three input and out- put terminals^ a stereo-mono switch, 500'kllobyte-per-second field memory, and a 7-bit A/D con- verter ft provides 240 lines of hori- zontal resolution and will operate on NTSC. PAL, and SECAM. The first VCR model will have no tuner, but a tuner-equipped version Cfor tuning NTSC broadcasts) is due early next year A model with a PAL tuner is already on sale in the U.K.. where one expert judged the picture quality not as good as the original, but ''quite good enough for most viewers wanting to watch family tapes from abroad/' • TV Data System. Next years TV receivers could have vastly ex- panded on-screen graphic ca- pabilities, thanks to a new "TV Data System" approved by an EIA engi- neering committee for submission to the FCC. The system is an ex- pansion of the technology de- veloped for closed captioning, which will be required by law in all TV sets 13 inches and larger made after June 30. 1993. The new data system adds a second field to the single field in the vertical interval line reserved for captioning. That addi- tional allocation will make possible closed captions in a second lan- guage and add new options, includ- ing a variety of background colors for the captions. It will also permit broadcasters and cable operators to develop new graphic and labeling ideas, including program identification service, which would offer on-screen label- ing of program titles at the push of a remote-control button— a feature especially useful to channel browsers. With additional software in home TV's and VCR s. the sys- tem would permit such features as automatic on-screen weather warn- ings for emergencies. Perhaps the choicest feature would be stations' transmission of their advance pro- gram schedules. Receivers could be programmed to seek and store that information. • VCR programming sys- tems. While the system described above could be used to program a VCR to tune to a single channel, a multi-channel on-screen program- selection system is scheduled to be introduced next year in sets made by Zenith, which has a one-year ex- clusive license. This system was de- veloped by InSight Telecast, a California firm whose backers in- clude the cable programmer Viacom, the Japanese trading com- pany C, Itoh. and several other com- munications and entertainment fjrms. InSight plans to use a portion of the vertical blanking interval of the PBS network Cwhich reaches 90% of TV sets in the U.S.) to send out a detailed program guide grid. Zenith TV sets equipped with the system will be able to call up those grids, as well as detailed descrip- tions of each program and even list- ings of programs by type (sports, talk, drama, etc). The on-screen grid would be used to set up VCR's by program name rather than time and channel The TV set contains an "IR blaster." an infrared transmitter at the end of a cable that sets up the VCR through its remote- control re- ceiver Future VCR's are expected to have InSight built in. InSight plans to offer the service by subscription, and its goal is to supply it for about half the price of a subscription to TV Guide. TV Guide also is experimenting with a programming system, in con- junction with major cable interests. That system apparently is similar to InSight. except that it would be car- ried on cable TV systems. TV Guide's goB\ is for the service to be supported by advertisers. R-E Where will it be? Hawaii? I^s Vegas? Mexico? The Ba- hamas? irs up to you. WcYe going to send you a free coupon for up to six days and five niglm of free lodg- ing at the desiination of your choice. Now did we gel your at- tenlion? Here's how il worlds: We sell hooks, and instead of adver- tising our program on TV (al great expense) w^e decided to pass the savitigs along to you. When you decide to participate in our program, we'll send you a booklet of 40 coupons and a catalog listing our current book offerings. Purchase one book and include one of the coupons for your second hook. In ail, you'll gel 40 books for your ? 19^95 invesimcnl When we receive your fifth coupon, there's a bonus for you in the form of a free membership in the Grocery^ Savers of .Amer- ica. This will entitle you to save up to $50 or more on your mondily grocen- bill And on receipt of y our 15lh coupon, you automatically get a free membership in The Great American Traveler, entidingyou to receive a 50% savings on hotels, mo- tels and car rentals. On receipt of your 20th coupon, BingoJ Ybu get that big free lodging for six day^ and five nights at your choice of Hawaii, Mexico, Las Vegas or die Bahamas, li'bu re going to be very impressed with the book selections 2S w ell These are not all paperbacks, but die same, high-qual- itj volumes you see in bookstores at many times \iour own pur- chase price. Frankly; there jusi isn t enough room on this page lo outline all of the details, but don't pass this up! Send us your name, address and $19-95 so we can send you ;ill of the information, in eluding your catalog and 40-cnupon book today Mastertiharge antl Visa are accepted. CLAGGK Inc. RO, Bo\ 4099 l^nningdale. New ferii 11735 Gendemen: t've enctoH'd S !9.*>5 in full paymunt. Please send my "The (ireai T\fc t) for One e Aifiay^" booklet of 40 couponii and caialog. j Check Eiidf&cd □ MastetCard m_ (Qip coupon and mail lod^fDo not send cast tkrmtgb fbe mail) Write to Ask R-E, Radio-Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735 ro jz^o AO IN RBDUOB VAC vac VDc MA/N STEPDOWN FOMM£R MAiN RECTlFiEU I. l/M/TF^ c/Fca/fRr F/NAL^ mUTAGF RmuiAJim am/my FIG. 1— POWER SUPPLY BLOCK DIAGRAM. It can automatically provide the same output voltage for a wide range of input voltages. AUTOMATIC VOLTAGE SENSING rm interested in learning the basic approach for designing a power supply that can be plugged into any outlet with a voltage from a low of 85 to a high of 270 volts. Those supplies, found on some TV's and VCR*s, automatically sense the input voltage and supply the correct output voltages needed by the devices they're powering. How do these things work?— Lfanes, Curacao, Netherlands Antilles There s always more than one way to approach a probtem like yours. I can't say how any one sup- ply like that works, but I do know how I would go about designing one. The first thing to realize is that it s much mone useful to think about the output voltage supplied by the cir- cuit than it is to think about the volt- ages being supplied to the circuit. What we want to design is a supply that can provide 5. 12, 24. or some other DC voltages. Once you think about the device in that way the design of the front end that "sees" the AC outlet voltage becomes a bit simpler. The basic block diagram for a power supply that can automatically provide the same output voltage for a wide range of input voltages is shown in Fig. 1 . As you can see, the only thing that makes it different from a fixed- in put supply is the box labelled 'voltage limiter/' The job of that section of the circuit is to take a range of DC voltages at its input and provide a constant DC voltage at its output. This isn't a difficult circuit to de- sign because we are really talking about a "preregulator ' for the last section of the supply that generates the final output. The parts of the preregulator can include Zener di- odes, fixed output regulators, or other devices. In fact, the pre- regulator is really the same as a standard regulator circuit. It is most innportant to know that the preregulation of the voltage is done after the input voltage from the wall outlet has been reduced to a manageable level by the front-end transformers. Trying some brute- force approach to the problem at the main input transformer is cer- tainly possible, but it would involve a lot more circuitry. You could have the preregulator control the input transformer so that it would switch among several sec- ondary windings but, off the top of my head. I think this approach would result in a much more complicated circuit, A design for chopping the DC voltage is a more straightfor- ward way. If you start experimenting with that idea, or any other approach to the problem, don't ever forget that you Ye dealing with some very high voltages. POCKET-STEREO AMP I've been experimenting with the LM386 amplifier, and Tm wondering if it can be used as an audio amplifier. When I ptay my pocket stereo through the en- closed circuit, the sound is dis- torted — even at low volume* Do you have any suggestions about what's wrong? — R. Mar- cachen, Algonquin, IL I'm really surprised at your ques- tion because the LM386 was de- signed specifically for use with audio. The circuit you've sent me is one that usually shows up in the data books and should work without any trouble at alL I think your prob- lem is elsewhere — particularly with the output of your pocket stereo. The LM386 is a virtually bul- letproof IC that can put out about 300 milliwatts into an 8-ohm load. It can drive a small speaker at a re- spectable level, but only if you feed it with the right levels at its inputs and give it enough supply power to operate without clipping. The overall gain of the chip is con- trolled by the resistance between pins 1 and 8. The LM386 has an internal 1350-ohm resistor acRDSS those pins to give the chip a gain of about 20 dB. The maximum gain you can get from the chip is about 45 dB. obtained by bypassing the inter- nal resistor with an external 10 |xF capacitor. That's what you did in the circuit you sent in. Assuming you have enough avail- able DC power for the LM386 to operate properly the only thing that can be causing a pnDblem is too much power being supplied to its input. Although you have a trimmer between the stereo s output and the input of the LM386, remember that power is a product of both current and voltage, and you have to be con- trol each of these separately That means you need a resistor in series as well as a trimmer to ground. To give you an idea of how easy it is to use the LM386, look at the circuit shown in Fig. 2. This is a minimum amplifier circuit built around an LM386 and, as you can see, the component count is very low. Because there's nothing be- tween pins 1 and 8. the IC will give you a 20'dB gain at the output. Con- sidering the signal level that usually comes out of a typical pocket ster- eo s headphone jack, a 20 dB gain should be more than enough to drive a speaker at what is usually referred to as a "comfortable listen* ing level/* Notice the resistor on the input line that's in series with the stereo s output and the LM386"s input. That s what cuts the current level of the signal, and it s also what's miss- ing from the circuit you sent in. The v^lue of the resistor to use depends on the output power from the ear- phone jack, but you should start your experiments with a value in the area of tOK or so. You'll know when you have a good value because you'll get a clean sound at the speaker regardless of how you set the volume control on the stereo. Fia 2— THIS AMPLIFIER CIRCUIT will give you a 2(HAB gain at the output. The frequency response of the LM3S6 is pretty flat, but the specs show that harmontc distortion will exceed one percent THD when the input signal gets much above 12 kHz. Even with that limitation, the LM386 is the ideal chip when tt comes to buifding a power amplifier for a small speaker Breadboard the circuit shown in Fig. 2, and use it to determine the value of the resistor you'll need. Once you've found the right number, you can put it in your circuit. If you decide that the LM386 cir- cuit in Fig. 2 provides enough gain and suitable sound quality, you might consider scrapping the more complex circuit you sent in favor of the simple one. One of the goals in electronic design, as in other fields. IS to keep things simple. 1-INCH RECORDER HEADS I'm currently building a multi- track recording system and I'm putting it together by rebuilding several mult it rack reel to reel re- corders. I have lots of broken ones at my disposal and Tm able to steal parts from several dead machines to make a good one. The only problem Vm having is that I can't seem to find a source for the heads on the machines. Lots of people have stereo tape heads for sale but I haven't been able to find replacement heads with multiple tracks for 1-inch recorders. Any ideas? — T Hold- er, Coshocton, OH Tm always in favor of anyone who wants to turn old scrap equipment into usable products. I'm surprised you*re having so much trouble get- ting the tape heads. continued on page 90 $299 Electronics Workbench^ The electronics lab in a computer" Powerful software to build and simulate analog and digital drciiits. Building and testing droijis is fast and easy with Eiechvnks WoHibench, Jim didc^anMrag wiih a mouse to add partSt nifi %1res, and adjust instrumt^nK the traces on the simulated instnjmenL<; are the same as you'd gel on real equipment Bec^nks Workbench really is an eledionics lab in a computer. It*s ideal for leaining about electrom'cs, experimcnling, and prototyping dmiiis. ""Blecironlcs Workbench is prelfy^ amaZtng. " -jerry P«timffU, Pk.ajti/f^^ DOS Professional Version - Macintosh Version - $199 ^ecfro flics Workbench l/idndes; • W(>rfiiJfe ttlih passive and acUve components including iranriMors, di{xleSr and op^amps; a funoion jjencraior, an osdHoscope, a jDuliimeier, and a Bode pJoiier. • DigiMModuie}}a\h Piles, (^ptk>P&,:idderi, a ^ord gmeraior, a lo^ ftftalyser, and a wiique bg^r converter and sia^Htfia^. (416) 361-0333 Int€ractl?e Im^ge Technologies Ltd 90fi Niagara Falls Bofite>-«fd North Tona^^da, NY 141Z0-206O ^\UpJ' Fax (416) 36^5799 ^ Mtfhuwfc VffJgn to m w d if tmt oolf. Al iriijcAirlj ate ORCLE IBS ON mEE INFOHMATTON CARD Si Learn to troubleshoot and service today's computer systems as you build a 386sx/20 MHz mini tower computer! Train the NRI way — and team to service ttxiay^s computers as you build your own 3868x computer system^ now with 1 meg RAM, 40 meg IDE hard drive, and exciting new diagnostic hardware and software! Jobs for computer service technicians will almost double in the next 10 years according to Department of Labor statistics, making computer service one of the top growth fields in the nation. 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Only NRI gives you hcmdS'On training with the remarkable JLACEJ?. plug- in diagnostic card and QuickTech diagnostic sofhvare from UltraX— professional^ slaie-ofthe'art diagnostic iooit tkat make computer trou bleskooting fast and accU' rate. 16 I Your NRI computer training includeH all thi^: * NRl*» unique Discovery Lab^ for circuit dettign and testing * Hand-held digital multimeter with "talk*you-th rough** instructions on audio cassette * Digital logic probe that lets you visually ejcamine computer circuits * The new West Co€ist 388sx/20 MHz computer sy^tem^ featuring a high-speed SOSSGsx CPU, I megRAM^ 10 1-key intelligent** keyboard^ 1.2 meg high-densitx floppy drive^ and high 'resolution monitor * 40 meg IDE Aara rfriue • MS-DOS, GW'BASIC and Microsoft Works software • R^CEM, plug' in diagnostic card and QuickTech menu-' driven diagnostic software * Reference mtutuals with guidetirtcs and schematics NOW! Training now includes Ultra-X diagnostic hardware and software for quick^ accurate troubleshooting! Now you train with and keep the latest in diagnostic hardware and software; the extraordinary R.A.C.E.R* plug-in diagnostic card and QuickTech diagnostic soflware, both from Uttra-X, Using these state-of-the- art tools, you learn to quickly identify and service virtually any computer \ TWT^tjti problem on XT, ^ ^-C.W- AT 80286/80386, /_ 386SX and compatible machines. You discover how to use the R.A^C.E.R diagnostic card to identify individual defective RAM chips, locate interfacing problems^ and pinpoint defective support chips. Plus you learn to use your QuickTech diagnostic software to test the system RAM and such peripheraJ adapters as parallel printer ports, serial communications porU, video display memoi->\ floppy drives, and hard disk drives. Only NRI gives you such confidonce-bailding, real- world experience. 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Send today for NRl's big, free catalog that describes every aspect of NRI's innovative computer training, as well as hands-on training in other growing high-tech career fields. If the coupon is missing, write to: NRI School of Electronics, McGraw-Hill Continuing Education Center, 4401 Connecticut Avenue, NW, Washington, DC 20008, IBM in a Tti^lnlvTvti trndintutrh, urinLrmzHiannl nuJiinrJin ^f|lc}tj^n»« Cafp.RA.C.£.R and SEND TODAY FOR FREE CATALOG Mc{*raw-Hill Continuing Education Center 4401 Cunnecticut Avenue, NW 15,1 Schools Wafihinglon, DC 20008 ^Oieck ont- FREE cntnldj; i^nly OlOCROCOMPUTEft SESRVtCING OTOVidea'Audio Scn-iritig O Telecom mu nka tioiii O todustnai ElcctrDnics □ Security Ele^rtronics □ EtectTDn ic M usic Tpchnal □ Basle E loctronics □ Automotive Servicing Fcr carver caimcsi approved under Gl Biti n fhctk for details. 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S5P.95_S29 30 Day Money Beck Guarantee FREE 20 pm^ Cnlnlog Visa, M/C COD or send mor^cy order to: U^. Cable TV Inc. Depu KRE8 4L00 N\ Powertinc R±, Bldg. F-4 Pompano Beach, FL 33073 1-800-772-6244 For Our Record I, tbc undcn4grw4i da btrcby dedire und-er penalty of pcqucy that atl producupurth^iscd, and in Lbc fumrc^ *ill 4iid/o Update. RAYMOND R GRtESE, K6FD Santa Clara. CA GET THOSE NUMBERS STRAIGHT! I am very impressed by the quality of the "Build This articles that have appeared in Radio-Elec- tronics over the past decade, and I have built or adapted many of the devices that control AC power Yet 1 am annoyed by the frequent references to "110," "115," and "220." when describing household AC receptacle voltages. Although some old-timers can be forgiven for using such terms, there is no ex- cuse for seeing them in RadiO" Electronicsf '110/220" voltage does not exist anyv^here in the United StateSt and has not for more than 30 years. In the mid-1950s. "115/230" was common, but changed to "117/234" briefly before becoming the now-standard "120/240" in 1970. The American National Stan- dards Institute publishes a docu- ment entitled: "American National Standard for Electric Power Sys- tems and Equipment — Voltage Rat- ings (60 Hertz)." This Standard CANSI C84J) specifies that the Nominal System Voltage shall be 120/240 VAC in three-wire systems commonly found in residential areas. The great majority of electric utilities try to keep receptacle volt- ages at 120 ±3 volts AC. Some appliances might carry a nameplate voltage rating of 115 or 230 volts, but that considers the wiring voltage drop under load and is correctly termed "Utilization Volt- age." It is expected that the no-load voltage will be 120 or 240 volts. ERIC G, LEMMON Lompoc, CA CIRCLE 190 ON FREE INFORMATION CARD MORE ON MICROPROCESSORS, PLEASE I'm writing to commend you on the "Build This Microprocessor De- velopment System" articles CRa- dio*Electronics. April and May 1992). concerning the CMOS- based 1802 micnoprocessor During the mid'1970s. your sister maga- zine, Popular Electronics, ran a se- ries of articles dealing with the 1802, Many of those older articles can be photocopied at local public libraries. The two new articles, as well as the older ones, point to a very inter- esting fact— namely, that the 1802, in its use of chip pins and design philosophy, IS a very useful compro* mise between a general^purppse microprocessor and a micro- controller. Some other interesting things to note are that as a CMOS- based device it can easily be used in battery-powered projects, and it is one of the few microprocessors that will operate within the full military specification temperature range of - 55 to 125^0. That last feature is also due to the processor's CMOS construction, I would very much like to see more articles in Radio-Elec* ironies about small micro- processor-based projects, es- pecially those that use the 1802. JIM PARSONS Rapid City, SD DRIVEWAY ALARM SOURCE In Ask R-E (Radio-Elec- tronics. May 1992). the solution given to D. Ingebrighfs request for a driveway alarm will work. I installed thai system in my driveway about ten years ago. and it is in operation now. The manufacturer of the Air Switch is Acme Air Appliance Co. Inc.. 203 Newman Street* Hacken- sack. NJ 07601. Ask for Air Switch ConlrctI No. 118. RALPH MARSHALL The Rock GA CALL-WAITING SOLUTION In Ask H E (Radio-Elec- tronics, May 1992) the ^^Call'Wait- ing Dilemma" was discussed. In Houston, to defeat call waiting (for one call), you enter '*-7-4." That defeats call waiting for one call and then resets. (Other phone sys- tems have similar features. Call your local phone company's business of- fice for details. Some phone books also explain how to defeat call wail^ ing) This feature is a part of call waiting, and — at least rn Houston — you do not have to pay extra for it. I use the modem on my PC a lot. I have programmed that "prehx" ahead of the number I want to call and have experienced no interrup- tions. The caller just gets a ringing with no one ansv^rering and can call back later ^vith his voice call That does not interrupt the data transfer via modem. If the modem call is "in- bound/* then the "*-7-4" command will not work to defeat the call wait- ing, so I always try to be the one to initiate the call. JOHN CALLAHAN Houston, TX R-E OSCILIOSCOPE — OS gojOA ZOMHf. Dull Irac* 05 904flp • CRT Rt«dOtjt DIGITAL MULTIMETER OS 9D40D • & Tract Ohj-SOSSS DM-9tB3 Tvn* •Miruai RiPfv «log»c muf «LvgB ICQ Owivtr OM-6335 • 3 1'? &§rmsAi£3 CmCLE t76 ON FREE mFORMATtON CARD DRAWING BOARD Let's explore the mysteries of video scrambling. ROBERT GR055BLATT |*ve been looking around for a source for prewired LED ma- trixes to use in our honne-made oscilloscope but. so far at least. I haven't had a whole lot of luck. A few places had them but they were fairty expensive and, to make mat- ters even worse* there were mini- mum quantities and minimum orders. The problem is that the mini- mum s for each order are usually more than you or I would normaliy spend on electronic parts over the next six months. I can't believe that some supplier somewhere out there doesn't have a barrel or two full of those things hanging anDund. If anyone out there knows of a source for an LED ma- trix, please drop me a note and let me know about it so f can share it with everyone. I'll put it in the col- umn and post the address as a mes- sage on the E-Mail section of the RE'BBS C516-293'2283). as wetL Clt s hard to get on the bulletin board because it's always in use. but a bit of perseverance will win out.) I ' m still waiting to hea r from any of you out there who have done some- thing terrific and ingenious with the scope we designed over the last few months. The contest is still on, and the prizes are still waiting for a few winners. On a different subject entirely, I've been getting lots and lots of mail about video in general and scrambled video m particular. For some reason a lot of you really get enraged because some cable com- panies insist on scrambling certain premium channels. Before we go any further on this, let me tell you that I don't see anything wrong with it. Now, wait a minute — before you write me off as a stooge of the cable industry, let me finish. The cable companies have every right to scramble whatever they want, although the rumors that some companies are scrambling everything they transmit — including the standard VHF channels — ^is go- ing much, much too far Premium stations and the pay-per-view shows areok^to scramble. What's not okay are some of the regula- tions that a lot of the cable compa- nies insist are their God-given right to impose on you. To begin with, hitting you with an extra fee for putting in another out- let is ridiculous. Some years ago the phone company did the same thing — ^anyone who added an exten- sion phone on his own was risking life imprisonment or. even worse, being regarded as a not -nice person in the eyes of Ma Bell. That all went out the window years ago. and 1 think it's only a matter of time before the same thing happens in the ca* ble-TV business. And , as far as I am concerned, the sooner the better The most annoying part of the ca- ble system is the whole business of sending me scrambled signals, and then telling me I can 't do anything with theml As 1 said, if the cable companies don't want me to get a particular channel (because Tm not paying for it. or some other perfectly legitimate reason), then don't send it to me. Trap it out of the line before the cable comes into my home- The additional cost of the traps has to be offset by the reduced cost of the cable box needed for the system, and the cost of installation should be the same because anyone with an opposable thumb and finger can put a trap on the line. I agree that the signal coming into my home is the property of the ca- ble company but, and this is impor- tant, at a certain time the real ownership of the signal becomes less clear When the RF has been reduced to baseband video and has spent lots of milliseconds running around the inside of my TV set. I think things are a bit different and the cable companies" onginal claim of ownership is a lot weaker And if t worked out a way to record scrambled signals and then de- scrambled them on playback, what then? If I built a box that scrambled some of the channels currently sent to me in the clear, the cable compa- ny would look at me in a funny way, but 1 really doubt they'd care one way of the other Now that you know how I feel about this stuff, Td like to show you how to descramble signals > but I can't because there are several ways that signals can be scrambled. It s sad but true that being able to descramble one system is no guar- antee that you can descramble any other system. The scrambling methods can be broken into two basic categories. The method you have in your home depends on the kind of cable ser- vice you have, how it's sent to you, and the economics of your viewing region. That last reason is important because the cable companies have to pay for the decoder boxes; the more sophisticated the way the sig- nal is scrambled, the more the box costs. A cable company that has its franchise in a large city with lots of customers needs lots of boxes, and ^ that translates into some serious | numbers for the purchase of the ^ boxes. And don't forget that the ^ more extensive the scrambling m method, the more expensive the S equipment needed to scramble the | signal in the first place. 8 Taking apart the video signal and ? turning it upside down and inside * out is pretty simple, but putting it back together correctly is a different matter altogether. And the FCC 27 FIC. 1— THE MOST COMMON APPROACH to scrambling video involves manipulating the informaUon in the horizontal Interval. For example, without a sync pulse, the TV's tiorizonlai circuitry will treewheel, keeps a careful watch on how close the reconstituted signal corries to real video. If the new signal is too messy, the FCC will give it a big thumbs down. The most common approach to scrambling video involves manip- ulating the information in the hori* zontal interval. In the beginning, every cable company used the same method — they suppressed the horizontal sync pulse, which meant that the TV had no idea whene each line of video started and ended. The sync putse can be seen in the video waveform shown in Fig, 1. Without a sync pulsen the TVs horizontal circuitry will freewheel and you1t most likely see the hori- zontal weaving down near the cen- ter of your screen rather than being located discneetiy off to the side. That also means that the TV won't see the transmitted burst signal in the right place, and the colors will be off as well. ^ To descramble the video, a de- Z coding signal was sent, buried in the audio. It would rBStone the sync ^ pulse at the proper time and for the I proper interval. I don't want to z spend a lot of time on this because 8 there's as much chance of seeing e this as therB is of seeing a mast- S odon. Once upon a time they weiB ^ everywhere* but they're long gone today. The best way to get a good han- za die on the whole business of video scrambling is to get into the theory and the circuitry needed to turn the theory into practice. I have to stress at this point that you'ne not going to get much out of this unless you un- derstand how video works in the first place. Some time ago I did a series of columns on this subject. I strongly suggest that you get your hands on them, rBsd them, and then keep them handy for reference. HI assume that you understand the basics of a clear video signal as we go through the methods that are often used to mess it up. Every scrambling method de- pends on altering some or all of the control pulses that are included in the definition of the standard video waveform. That means that the most basic operation of any scram- bling/unscrambling system is the separation of the control infonma- tion from the picture information. That isni such a complex job be- cause the NTSC standard was de- vised with a strictly mathematical timing relationship between every individual part of the signal. There- fore, looking at a video signal is somewhat like reading a street map — if you know exactly where you are. you automatically know where everything else is. Or, in the case of scrambled video, just whene everything else is supposed to be. Sptitting the sync signal from the video waveform is. as I said, a very common job. After all, every TV does exactly that over and over as long as it s turned on. Most semi- conductor manufacturers with lines of video IC 's have several sync-sep- arator chips in their catalogs, al- though it's usually hard to buy them in single quantities from suppliers. And they're not the cheapest ICs around either I wonder if that means anything. Over the next several install- ments well be looking at various scrambling methods commonly used by the cable companies. I'll go thnDugh the theory and shew you how you can find out what your ca- ble company is shipping to the back of your TV set. And yes. we'll be looking at the circuitry needed to descramble the signals^^ — practical examples with component values. I'll be using standard ICs that meet all our usual criteria of price Clow) and availability (es/erywhene)* but this is one area where you're really going to need an os- cilloscope. If you're serious about electronics you should have one of these things anyway, because they're just about the most basic and esJ^ential piece of test equip- ment you can own. When we get together next time we'll start things out by building some stuff that will scramble a stan- dard video signal. That may seem a bit strange, but remember that the first step in defeating an enemy is to learn to think like he does, R-E GET YOUR RECHARGE CATALOG FREE...EARN BIG SS IH YOUR SPARE TIME— All supplies and DO'll*YoiiFse!f kils wilh complete instructions available. 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Fanrtirigdalo, NV 11735, FAX; 516-293*3115 CABLE TV CONVERTERS AND DE- SCRAMBLERS SB'3 S79.00 TRl-BI S95.00 MLD-$79.00 M35B S69.00 DRZ-DIC $149.00, Special comtxjs available. We ship COD. Quaniity discounts. Call for pricing on other procfucts. Dealers wanted. FREE CATA- LOG. We stand behind our products where others fail. One year warranty. ACE PROD- UCTS. RO. Box 582, Saco, ME 04072, 1*800*234-0726. CIRCLE 75 ON FREE IMFORMATIGN CARD I! TWO TRANSMITTERS IN ONE! 5 MINUTE ASSEMBLY! MONEYBACK GUARANTEE! New Law Enlorcemeni grade device on a single chip is the most sensitive, powerful, stable room transmitter yog can buy Uses any 3V-12V battery Or attach to telephone line 10 monitor all telephone conversations over 1 mile away without batteries^ lOOmW oulput! fl0-l30MHZ. Receive on any FM radio or wideband scanner VT-75 microtransmitter. S49.95 + 1.50 SSH, VISA. MC. MO, CODs add S4m OECO INDUSTRIES, Box 607, Bedford Hilts. NY 10507. 1-800-759-5553. CIRCLE 127 ON FREE INFORMATION CARD WORLD S SMALLEST FM TRANSMIT- TERS! New Surface Mount Technology (SMT) makes ail others obsoletef XST500 Transmitter— powerful 3 transistor audio am- phtier. transmits whispers up to 1 mile. XSP250 Telephone Transmitter — Ime powereti. transmits conversations up to mile. Both tune 88-108 MHz, Easy to assem- ble E*2 KITS (SMT components pre- assembled to circuit board)! XST500— S39,95, XSP25a--$29.95. VISA.'MC. COD add S5 XANDI ELECTRONICS. 201 E. Southern Ave., SuHe 111, Tempe. AZ 85282. 1*800-336-7389. aaCL1 184 ON FREE IKFORUATION CARD TUNABLE SOdB NOTCH FILTERS— for TV. Can be tuned precisely to required frequency. Model 23H-Chs 2*3 {50-66 Mhz) Model 46FM-Chs 4-6 plus FM (66-108 Mhz) Uod^ 713-Chs 7-13 (174-216 Mhz) Model 1417-Ch's 14-17 (120-144 Mh2) Model 1822-Ch's 18-22 (144-174 Mhz] S30 each, includes shipping. Visa. MC, Of check. (CO D. $5 extra). Fast delivery. 30 day money back. Quantity prices to SI 6. STAR CIRCUITS, P.O. Box 94917, Las Vegas, Nevada 89193, 1-800-535-7827. $495 FOR A PROGRAMMABLE DC POWER SUPPLY IS NOW A REALITYI • GPIB interface Standard • Output Voltage Curfent Programming & Readback • Local & Remote GPIB Operations • Remote Sense Function • Programmable Overvoltage and Overcurrent Protection • Soil ware Calibra- tion • Superior Line^Load Regulation • Output Enable/Disable • 3 Year Warranty FREE Oriental ion Video available. For de- tails, call: AMERICAN RELIANCE INC. 800^54-9838 FAX: 818-575*0801. CIRCLE laO OH FREE INFORMATION CARD NEW LIT Si o o 111 30 TELEVISION ENGmEERlNG HANDBOOK: REVISED EDI- TION; by K, Blair Benson; re- vised by Jerry Whitaker McGraw-Hill. Inc.. 1221 Av- enue of ttie Americas, New York, NY 10020; S99.95, Since this book was first published 35 years ago, television engineering has undergone many changes. One of the most fudamen- tal changes was the re- placement of vacuum tubes by transistors and ICS. CIRCLE 39 ON FREE INFORMATION CARD Other milestones in- clude the worldwide accep* tance of color TV. the introduction of cable TV, and the use of satellites as relays The new tech- nologies that have im- pacted television engineer* ing during that period include digital recording and transmission, hand- held video canneras. and the video cassette record- er (VCR). The video cas- sette and its format has been standardized and the laser disk has appeared. On the horizon is high- defi- nition television CHDTVX What system will be se- lected, wiil it be accepted, and how will it affect exist- ing transmission arrd re* ceiving methods? The original handbook has been completely re- written by a team of 70 contributors, each a spe- cialist in his field. In more than 1500 pages^ the hand- book provides comprehen- sive technical information and reference data for engi^ neers who design, develop, service, and operate televi- sion systems. The topics covered in- clude the fundamentals of television, signal genera- tion and processing, trans- nnission, reception, and picture reproduction. Ad- vanced TV systems are discussed and reference data is included. Opening chapters contain sufficient tutorial content to provide the reader with a back- ground for understanding the principles involved in the subjects covered in subsequent chapters. Those tutorial subjects include reviews of the prin- ciples of color vision, pho- tometry, and optics as they relate to television engi- neering. Later chapters cover broadcasting, cable and satellite distribution, signal and image storage on videotape, video disks, and film. The latest tech- niques for digital signal pro- cessing and transmission are also Included. Other chapters discuss graphics generation, picture manip- ulation, and TV standards conversion. A thorough coverage of the TV standards in the United States and the rest of the world is presented. A chapter is devoted to data, equations, and definitions not generally found in tele- vision-engineering hand- books. Finally a detailed survey of HDTV contains a discussion of the digital and analog HDTV pro- posals from competing teams of corporations and laboratories. It explains their operating principals and benefits. THE SODEfl-WICK SYSTEM; from ChemtrDnics Inc., Soder-Wick Fine-Braid, RQ. Box 1448, Norcross, GA 3S091-9931; free. This six-page, full-color brochure explains the Soder-Wick Fine-Braid desoidering system. It is said to be useful in the re- moval of both leaded and surface-mount compo- nents fnDm all boards. fluxed (pure water white rosin or no-clean) and un- fluxed. Sod er- Wick Fine- Bra id will remove accidental sol- der bridges and excess solder from all locations and correct poor solder joints. It is said to be helpful in the removal and re- mounting of all circuit com- ponents. HOW TO ETCH YOUR OWN PRINTED CIRCUIT BOARDS; by Neil Petrucelli, Cover to Cover Desktop PoEilishing, Attn: PCB Book, P.O. Box 8064, Westfieltl. MA 01086-8064; 59.95. This step-by-step in- struction manual is filled with valuable information CIRCLE 38 ON FREE INFORMATION CARD Chemtronics says its desoldering braids are made from oxygen- free » high-conductivity (OFHC) copper wire braided in a geometnc pattern that effi- ciently wicks molten sol- der The braid is cleaned to prevent the contamination of parts being desoldered. Braids are available in nine widths from 0.022 to 0.210 inch. The braid is available CIRCIE 37 ON FREE INFORMATION CARD for anyone interested in etching printed circuit boards. It leads readers through the entire process from analyzing the circuit to laying out the correspond- ing traces and pads, A pho- tographic process forms the circuit board mask that is then positioned against the copper-clad board and exposed to light. The author says the pro- cess produces PC boards comparable to those from industrial vendors. He keeps the hobbyist in mrnd by providing a fist of readily availabte and affordable equrpmerrt. The PC board manual is fully tllustrated with computerajded de- sign drawings. EASY PC MAINTENANCE AND REPAIR; by Phil Laplante. Windcrest/ McGraw-Hill, Blue Ridge Summit, PA 17294-0850; S14.95. This guide contams dear instructions that make it easy and inexpensive to troubleshoot and maintain your personal computer. No technical experience is needed to take advantage of the diagnostic advice given rn this book: the only tools necessary are a screwdnver and a pair of pliers. However, the reader who wants to do his own seivicing should at (east have a basic understanding of how personal computers work. The book applies to all IBM-compatible PC's Mjjinlemnce CIRCLE 40 ON FREE INFORMATION CARD based on Intel 8088. 80286. 80386. and 80486 microprocessors. Laplente s book explains the fundamentals of com- puter architecture and in- troduces PC terms and concepts. It explains how to perform the most fre* quently needed repairs and carry out routine mainte- nance procedures. Those procedures are illustrated with many helpful pho- tographs, drawings, and ta- bles. The book tells you how to prevent common hardware failures, dis- cusses the latest upgrade options, and reviews vital software tools that can help you to optimize your PC's performance. TELECOMMUNICATION WIRING; by Clyde N. Herrick and C. Lee McKim. Prentice HalL Englewood Cliffs, NJ 07632; S34.00 Written for the telecom- munications professional this book covers the impor- tant issues of wiring sys- tems. It is a valuable reference for decision mak- ing in cable design, materi- als, writing (he job pro- posaL documenting exist* ing systems, and establish- tng maintenance pro- cedures. Topics include nuiiiii I Ttlmininiiiniriiiii WlltlMl Tl CIRCLE 41 ON rREE INFORMATION CARD Specialized winng for com- puter installations. Wiring design, power sources, alternative power supplies, and expansion of existing facilities are dis- cussed, and maintenance, and troubleshooting pro- cedures are given. A tu- torial guide to the 1990 National Electric Code is included. This book gives the reader an outline for successful planning, in- staflation, and testing of ca- ble systems. R-E PtUGViniTO THE WEATHER! Tlvf IT^IO Uind.stitiafi nwif-iop st'nwjr plugs directly into (he FC (lamr Port. It M!fid$ ydu immcdhtc mruurtmcnts of ) our local Mcaitterpaiterns Wind speed, difmion 2nd gusi t^ue data amcontinuouslv disp1i)ied. OuuJde tcmpcratua% i4 tiour extfcme^ and w ind ch i 1 1 vaJ ues are optional . Mfinlhs iif information can be i lifted fcjf viewing, plotting and anahi^is. To plug into the weaihrr. calJ the order line; ]'80O-992 gllO ^MfeathefPort (916) ftx {9lS) 273'642<) CIRCLE 1M ON FRCe INFORMATION CARO Cable TV Article Parts We stock the exact Parts & PC Board for an article published in Radio Electronics Magazine on building 3 Snooper Stopper. Snooper Stopper Kit $19.95 jnciLTdvi ftJl ih« onpinal Port I & Etchsti. DuMtd Silk^crHntd PC Bovd. Snooper Stopper*.. , .S39.0D 106.5Mfu. Snooqtr Stoppiif ■'Or rnost JflfTD^d sycitms. Protect yourself from descrambler detection and stop the Bullet with one of our Snooper Stoppers. Macrovtsion..now you sea it, now you don't. Macrovision Kit 529.00 ^nctuo«i ftll HIV ofi^Erwl P«n» & Etcn*^, Onii Silk -S era An vd PC Bot/d. DngimJIy PudUsl^d in r^LadiD Eractmnics Magauno Call Toll Free 1-600-866*8699 Visa, MasterCard or COD Northeast Electronics, lnc« PC Box 3310 N. Attieborq, Ma. 02761 Be an FCC i LICENSED ELECTRONIC TECHNICIAN! i rt it hom« In ipafe time. I No piwioui expf fienoe ne«^t No costly school. 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Subscribe to the best electronics magazir^e— the one that brings you the latest high-tech construction projects, feature articles on new technology practical troubleshooting techniques, circuit design fundamentals, and much more. Electronics Now looks to the future and shows you what new video, audio and computer products are on the horizon. Whafs more you1l find helpful monthly departments such OS Video News, Equipment Reports, Hardware Hacker, Audio Update, Drawing Board, Computer Connections, New Products, and more. All designed to give you instruction, tips, and fun. Eiectronics Now gives you exciting articles like: • Buyer's Guide to Digital Oscilloscopes • Build A Scanner Converter • Single-Chip Voice Recorder • Build A MIDI Interface for your PC • Troubleshoot Microprocessor Circuits • Build A Higti-Power Amplifier for your Car • Add Music On Hold to your Phone • All About Binaural Recording • VGA-to-NTSC Converter FOR FASTER SERVICE CALL TODAY 1-800-999-7139 DON'T DELAY SUBSCRIBE TODAY! Just fill out the order card in ttiis magazine and mail it in today. 5REH4 Battered by a noisy world? Create your own soothing sound bacifground witli Surf Man. LISTEN. IT'S A NOISY WORLD. WHEN THE KID'S TV IS GOING UPSTAIRS. AND THE HI- ft is on in the living room. It can be hard just tr>'ing to think. If you'd like something to block out irritating, distracting sounds, here's something you'll like: SurfMan. It's a gadget that's small enough to fit in your shirt pocket and uses Walk man -style headphones to provide a soothing per- sonal audio ambiance of rain, crashing surf, or unmodulated pink noise. We like to think that the surf sound is something like Hawaii's Waimea with the Banzai Pipelint; thundering in the background, and we hope that you|igree. Fighting noise with noise , For a casual deiln itlon of unwanted nfcise, let's say that it is random sound occurring i|i the back- ground which, despite your best intentiims. still grab your attention from time to time. Yo« can however, mask unwanted noise with another kind of noise. Noise comes in colors. Wliite noise.jjiuch as the hiss heard between FM stations has% uniform distribution of all audio frequenciesiimixed to- gether—just as white light contains pll colors. Pink noise, like the color pink, is wemhted to- ward the lower-frequency end of the sjectrum Noise has interesting psycl30-acous|lc prop- erties. Experiments have showTi that exposure to pink noise increases learning under cer- tain controlled conditions, but the effects arc transien t and learn- ing soon re- turns to r St 0 + 9V 11 .01 + 9V C16 01 ^ 100K R1 8 74HC14 B3 R4 R3 100K ^10 Ve 74HCH m 22m m 100K R7 1? 1cm V6 74HCtl R9 I DDK C4 , 33mF^ FITO .01 -4^ 10K R20 Vf74Ba4 1 /«74HC14 R21 tOOK R22 IK :Cf2 .05 C11 -g H23 IK R2? SDK R24 15K R2€ 220pF J FIG. t— SURF MAN SCHEMATIC. The ctrcuit produces relaxing surf-Hke sounds. the base rate observed wILliout the noise. White noise has also been used instead of local anes- thetic by dentists, but whclhcr positive results were from actu- al analgesic properties or simply placebo effects is debatable. In the old spy movies the hc- roes/v^illains would discuss their plans to save^control the world in the bathroom with the shower running. You might think that this was just some kinky quirk that accompanies the Bond mentality, but in real- ity the sound of water from a shower Is a kind of pink noise, and its uniform distribution of frequencies is quite effective at masking speech and disabling hidden electronic bugs. A lot of natural sounds are es- sentialiy noise — rain on a roof, for example, is white noise. And others* like wind and surf, are ''voiced" noise, which means that their amplitude and fre- quency spectrum are modu- lated over time. Generating noise A number of methods have been commonly used to produce random noise. SurfMan de- pends on the noise produced by electronic components for truly random noise generation. All electronic components produce some noise, mainly because they re not working at absolute zero temperature, and the heal- Induced movement of electrons through the part results in ran- dom voltage and current fluc- tuations. In most components, the noise level is just enough to be a source of aggravation In critical circuits, but not enough to be useful for what we re doing. When Its reverse-voltage toler- ance is exceeded, a semicon- ductor junction breaks down and produces just the kind of noise that we Ye looking for Zener diodes do that, but some are specifically designed to min- imize the random fluctuations. The base-emitter junction of a silicon transistor that has been reverse biased to the point of av- alanching produces the kind of noise we're after, and it hasn't been designed out. So that's what we'll use. How it works A minor complication with using a transistor for the noise source is that its rare to find a base-emitter junction that will avalanche at less than about 10 volts — not quite low enough to be produced reliably with a 9- volt battery. Wc could use two batteries of course, but then the battery size would get to be a problem. The solution Is to use a voltage doublet Look at the schematic In Fig, 1. One stage of a 74HC14 hex Schmitt trigger inverter (lCl*c) is configured as a square -wave oscillator whose frequency is set to about 40 kHz by feedback re- sistor RIO and capacitor C6, When the output of the os- cillator is low. C7 charges through Dl so that the junction of the diode and capacitor is positive with respect to Uie out- put of the amplifier When the output switches high, the volt- age on the capacitor ts added to the output, and the resulting voltage charges C8 through D2 to roughly 18 volts. When that voltage IS applied to tlie reverse- biased base-emitter junction of Ql by way of RIL the junction avalanches and noise appears across the resistor The 18-voIt supply only biases the noise source and does not power any other circuitry. The low-level noise is coupled by C9 to the non-inverting in- put of op-amp IC2-a. a 5532 dual low-noise op-amp. Because the op-amp is billed as a low- noise component for audio ap- plications, it might not make much sense to use it in an ap- plication where noise is our ob- jective. But the part was chosen for its drive capabilities because it will drive low- impedance headphones. The 5532 is intended for bi- polar operation, but here w^e have only a single-ended supply* the 9-volt battery. To compen- sate for the lack of a bi-polar supply we provide a 4.5-volt ref- erence using voltage divider R15-r^l6. Every point that would normally be connected to ground is returned to that refer- RG. 2— PARTS PLACEMENT DIAGRAM. To conserve space, stand resistors on end and mount tall electrolytic capacitors on the solder side of the board so they He flat. ence point, thereby fooling the amplifiers inputs into thinking that there are positive and nega- tive supply rails. Capacitor CIO bypasses the reference voltage source so that it appears as a ground for audio signals. SurfMan s "wave action** sound effect is produced by three separate low-frequency oscillators running asynchro- nously The oscillators are sim- ilar to the one that drives the voltage doubler. but their oper- ating frequencies are set at a only one cycle every few seconds with larger resistor values (Rl* R4. R7) and capacitors (CI, C2. C3). Wlien added together the three oscillator outputs form chaotic voltages that are an elec- tronic approximation of surf sounds. 1\vo separate control voltages are generated. The first is through resistors R2, R5. and R8, Because those resistors are of equal value, only four dif- ferent control- voltage levels can be generated. The voltage level depends on how many of those outputs are high, and not which outputs they are. You can think of this voltage as repre- senting the "sets * of ocean waves. The second voltage is produced through R3» R6, and R9. whose values were selected as powers of two to produce eight different control-voltage levels. They can be thought of as representing the individual waves within the set. The volt- ages produced are smoothed by integrating them with capaci- tors C4 and C5. TWo voltage-controlled filters (VCF*s) convert the control volt- ages into a changing frequency spectrum. Ordinarily VCFs use transconductance amplifiers, FETs, or optocouplers as con- trol elements, but here we use diodes. Its not common to see diodes used this way In audio, but they function very well and they're hard to beat when low cost and a small size are impor- tant. The basic idea is to control the effective impedance of the diodes with a DC current while AC coupling the signal of inter- est to them. As long as the AC signal level is much less than the DC controlling current, the current works well* The filter consists of two * L" section circuits comprising R22. R23. C12, and C13. with D3 and D4 as the tuning ele- ments. Notice that the anodes of the diodes are returned to the reference voltage source men- tioned earlier so that the con- trolling v^oltages can both for- ward- and reverse-bias them. Control voltages are coupled to the diodes through R20 and R21 with potentiometer R17 and fixed resistors Ri8 and R19 providing a control of their fixed bias- As the control voltages for- ward bias their respective di- odes, the decrease in imped- ance pulls the comer frequen- cies of the filters back so that higher frequencies are by- passed to ground. Finally the output of the filter appears across volume-control R27. which sets the amount of signal applied to the final out- put amplifier that includes 1C2- b. The output of the amplifier is current-limited by R26 before appearing at the headphone jack Jl. \Vhile the wiring of Jl might look strange, it is done that way so that the two head- phone elements are in series. This is not a stereo system and doubling the impedance of the headphones makes it easier for the op-amp to drive them. BuildiBg SurfMan If 3"ou"re not concerned about the size of the finished unit, only the standard construction precautions apply: be careful about orientation of polarized components such as IC's. di- odes» electrolytic capacitors, and transistor Ql. The 74HC14 is a CMOS part and subject to damage by electrostatic dis- charge. Avoid shuffling along on a nylon carpet while han- dling the part. There are no par- ticularly high frequencies in- volved, so any construction technique will work just fine. Because of some fairly high- gain stages, keep wire lengths as short a possible to prevent hum pickup. If you're interested in build- ing a compact SurfiVlan such as the one you see in the photos, you're going to have to pack a good number of components in a relatively small space- Figure 2 is the parts placement diagram. Tb make maximum use of the circuit board area, stand re- sistors on end and mount all tall electrolytic capacitors on the FIG. 4— TO CONNECT SURF MAN to your hl-ff setup, use this capacitively coupled voltage divider. The *'Y" connector lets SurlMan drive stereo inputs. ^ PARTS LIST ^ All resistors are y4-watt, 5%, uri- less noted otherwise. M R1— 2.2 megolims " R2. R5, R8, R9— 100.000 ohms R3, R1&— 47,000 ohms R4 — 1.5 megohms R6— 220,000 ohms ii R7. R13, R25— 680,000 ohms M RIO— 33,000 ohms M R11 — 1 megohm " R12. R24— 15,000 ohms R14. R20— 150.000 ohms R15. R16— 2200 ohms R17 — 10.000 ohms, trimmer poten- tiometer R1&— 39,000 ohms R21'-100.000 Ohms R22, R23— 1000 ohms R26 120 ohms R27— 50,000 ohms, audio taper potentiometer with on'off switch (SI) Capacitors C1. 02, C3. CIO— 10 pF, 16 vOlts, eJectrotytic C4, C5. C16— 33 jiR 16 volts, elec- trolytic C6— 470 pR ceramic disk C7. C8. C9-^.01 ceramic disk C11— 4.7 ^iiR 16 volts, electrolytic C12, C13— 0.05 |jiR ceramic disk C14, C15— 220 pR Mylar or poly- styiene Semiconductors IC1— 74HC14 hex Schmitt trigger inverter IC2—NE5532N dual op-amp D1-D4— 1N4148 sifjcon diode Q1— NPN silicon transistor se- lected for noise (see text} Other components J1— miniature stereo phone jack S1— SPST switch (part of potenti- ometer R27) Miscellaneous: 9-volt battery and connector, case, PC board, knob, headphones, wire, solder, etc. Note: The following are avalalbfe from PAIA Electronics, lnc.» 3200 Teak wood Lane, Edmond, OK 73013 (405) 340-6300: • Etched, drilled and sllkscreened PC board (9160pcKS6.95 • Complete SurfMan kit in^ eluding PC boards case, and selected noise transistor (no headphones) {9160KH-$27J5 Please add S3. 50 shipping and handling to each order. soLder side ol the board to allow them to He flush with the board. Capacitors that are short enough to stand up on the com- ponent side of the board and 2»A IMCHES — ^ USE THIS FOiL PATTERN to make your own PC board for SurfMan. Still allow the board to fit Into the case are available, but they're more expensive and they are not really necessary. You can etch your own board with the foil pattern provided or buy a ready- to -use board from the source given In the Parts List. Even if you skip the circuit board and build the SurlMan on a piece of perforated con- struction board* it Is recom- mended that you follow the general component layout In Fig. 2. (A lot of effort went into minimizing trace length and placing components, so you should take advantage of this work.) Fully assemble the circuit board by mounting all resistors, diodes, capacitors, and !C*s, Do not install the noise transistor (Ql) yet. Use 22-gauge or small- er stranded wire to make con- nections from the circuit board to the volume control (R27K power switch (SI, which Is part of R27), and phone jack (Jl). The five jumpers on the circuit board should be made with Insulated wire to keep them from shorting against adjacent component leads. Snap a 9-vo!t batterj'^ into the connector and plug a pair of headphones into JL The gener- ally less expensive 32-ohm headphones are preferable to 8- ohm phones because their higher impedance is more eaisly driven by the output amplifier. Thrn on the unit transfer by ro- tating the shaft of the volume control fully clockwise. You won*t hear any noise because Ql has not been installed, but you can perform a quick test by touching your finger to pin 3 of IC2. You should hear a fairly loud buzz as environmental electromagnetic fields are cou- pled into the amplifier If there is no hum, you have a clear indica- tion that something is wrong. With that test successfully completed youYe ready to instaU the noise transistor. Almost any NPN silicon transistor, such as a 2N2712, 2N2222, or 2N3904. is a good candidate for QL You might not like the first tran- sistor you pick because smooth noise is what we're after You may run into a device that emits a lot of "popcorn" noise, which youll recognize if you hear it. Htm on the unit and set R17 fully clockwise. Press the emit- ter and base leads of the tran- sistor that you're testing against the pads on the PC board. You might have to hold the device in place for a second or two so that voltages can sta- bilize. Also be careful not to touch any of the transistor continued on page 79 a a 1=1 a Protect your confidential telephone calls against intrusion with this easy4o-build telephone-voice scrambler DAN ROSENMAYER TELEPHONE* VOICB SCR^VMBLINC IS the most effective method for eliminating unwanted eves- dropping on your confidential phone calls, it should be consid- ered if you have reason to be- lieve that unauthorized persons are or could be listening in on your telephone conversations. A system consisting of two com- patible telephone-voice scramblers will permit normal conversation between you and your intended listener, while making all speech unintelligible to anyone listening on exten- sions at either end of the line. Only a person with a compatible imscrambler will be able to un- derstand what is being said. Many circuits are available that can monitor your phone hne and detect intentional or unintentional removal of hand- sets from their hooks on any ex* tension. Because theyVe easily defeated* those circuits could lull you into a false sense of se- curity. Even If you detect an un- authorized listener "hornin/^ In/* you have only two choices: hang up or be on guard against saying anything that you don*t want to be heard by an un- authorized third party Matched telephone voice scramblers enable you to carry on conversations without guarding your speech. They also eliminate the threat of wire- tapping and covert tape record- ing, unless the intruder has the necessary circuitry to unscram- ble your garbled conversations^ In the past, factory-made tele- phone voice scramblers were ex- pensive and difficult to find, lb- day scramblers are more readily available and their prices have fallen because of the availability of low-cost voice scramblcr/de- scrambler ICs- Howeven those scramblers might include cer- tain features that you don't want such as a briefcase hous- ing. This article will permit you to build inexpensive » compact, and effective voice scramblers In the form of loaded circuit boards. Figure 1 shows the TVS250 voice scrambler coupled be- tween the headset and base of a standard telephone. It is half of a complete telephone security system. Connections between the scrambler circuit and tele- phone are easily made with standard telephone cords ter- minated wltli standard modu- lar plugs, A second voice scrambler would be similarly connected to another telephone to form the secure telephone system shown in Fig, 2, Theoiy of operation ^ The heart of the TVS250 is | the COM9046, a voice ^ scrambler/descrambler IC made g by Standard Microsystems N Corp, Figure 3 is a simplified ^ block diagram of that dedicated 2. chip. The IC contains two iden- § tical speech channels that per- S mit full-duplex operation when © connected between two tele- ^ phones. Each channel is capa- ble of scrambling and descram- bling voice communications. 37 /St TELEPHOfJECORO' Q Qua raEPHOHE BASE UN FT Qiu-i— POWER SWITCH ($11 -SCPAMHLi;.':-'ORMAL: RED LEi ADJl^STMEiMT COFJIROt. KNQJ -RI IHANDSFT S PEAK E-R VOL U R2 {I^A^JOSET MiC- SfNSrnW HANDSET SPEAKER HArJDSET MICROPHONE fMlC) FIG. I^NE END OF A SECURE TELEPHONE SYSTEM, a TVS250 scrambler circuit coupled between the handset and the base of a telephone with standard jacks and cord. TVS250 USER r;S250tjSER TVSZ^O SCRAMBLED 5CFWMBLED SCBAMDlffO < ti i ^ V SCRAMBLED TVS250 "J r „_,„^^ SCRAMBLED SCRAMBLED MODE FIG. 2— COMPLETE TELEPHONE SECURITY is obtained with a TVS250 at both endsol the phone Ifne forming a duplex scrambler/descrambier system. To render the speech chan- band modulator. While one nels unintelligible, the incom- channel accepts the normal fre- ing audio signal is inverted by quency spectrum from the the ICs internal double-side- handset microphone, inverts and transmits It* Uie other channel accepts the incoming inverted signal, normalizes and sends it to the handset speaker. Circuit design The COM9046 voice scrambler/descrambler iC con- tains a cr>^stal oscillator that controls system timing. The on- chip oscillator requires an exter- nal 3,58-MHz crystal that is commonly used in TV color-bur- st applications. The chip also contains switched-capacilor fil- ters, so input speech must be filtered by an anti-aliasing sin- gle-pole, loW'pass filter before it is applied to the audio input at pins 5 and IL The filter's 3-dB cutoff point is determined by the resistors and capacitors connected to pins 5 and 1 L The values of those com- ponents were selected so that the cutoff point is less than 20 kHz, As shown in the sche- matic. Fig. 4, both R5 and R6 have values of 3.0 K. and bot h C I 1 and C 12 have values of 2200 pK Applying those RC values to the equation for iiller cutoff fre- qucnc}; Fq - (2xRC)/2, yields a 3 dB cutoff frequency of about 18.5 kHz. The COM9046 was designed to operate on ^: 2,6 volts ( -f 2,6 volts at pins 9 and 7, and -2,6 volts at ptns 3 and 8), This oper- ating voltage is measured with respect to a ground reference at pin 4 of the IC. f loweven the WS250 operates from a single 9'Volt transistor batter)^ so it is necessary to obtain the re- quired ±2,6 volts from a uni- polar 9- volt transistor battery. Those voltages are measured with respect to the ICs analog reference at input pin 4. The 9 volts can be reduced to 5 volts by IC4. a 78L05A low- voltage regulator, as shown in schematic Fig, 4. The 5- volt in- put is applied to a voltage divid- er consisting of R16 and RIB. Pins 7 and 9 of 101 are con- nected to the 5-volt source. Pins 3 and 8 are connected to the supply ground (0 volts). The midpoint of the two resistors R18 and R16 is connected to pin 4 of the IC, Because the two re- sistors are of equal value* their junction prodLices +2,6 volts. SCRAMBLE- i -I 2 k ( 4- 2.6V. — f 1? » f 14 »-- FIG. 3— SIMPUFJED DIAGRAM OF THE COM9046 SCRAMBLER DESCRAMBLER IC and somo peripheral components that are the heart of each TVS250 voice scrambler. the teiephonc base passes IC 1 , it drives the handset speaker. The audio output signal from pin 6 of IC 1 is fihered by an active low- pass filter consisting of IC3-b, R14. R15. Ct3. and C14. inserting those RC values in the low-frequency cutoff equa- tion given earlier will show that the filler can pass all frequen- cies below 3,1 kHz. The filter greatly reduces high-frequency noise, especially that produced by clock feedthrough front ICTs internal osctliaton The output from this low- pass RUer is applied to the audio amplider IC2 which acts as a low- power dilTercntUil driver connected to the handset speaker. Potentiometer Rls re- sistance value of 100 K will per- mit volume adjustment of the handset speaker. HAJ40SF1 SPEAKER HANDSET SPEWER RG. 4^SCHEMATIC DIAGRAM FOR THE TV5Z50 voice scrambler. Now with respect to pin 4, pins 9 and 7 are at +2.6 volts, and pins 3 and 8 are at -2.6 volts as shown hi Fig. 3. Both of those values are within the acceptable limits for ICL The scrambler/descrambler ICl can be interfaced with a standard telephone. The audio output from the base of the tele- phone is AC coupled to ICl via C5. After the audio signal from The equivalent circuit for the handsel microphone is a poten- tiometer that changes its resis- tance with applied Input audio signals* In quiet periods, its effective resistance is constant. I if} 3 o 39 but when audio input is ap- plied» its resistance changes lin- early with the varying Input frequencies. Because the microphone can be considered as equivalent to a potentiometer a voltage divider can be formed with R17 as one resistor and the handset micro- phone as the other one. As the microphone's resistance changes, the voltage at JIJ4 will follow That voltage is AC cou- pled by C3 to the amplifier cir- cuit that includes lC3-a. Filter resistor R21 andcapacl- tor C8 form a high-pass RC filter for the amplifier circuit that will attenuate low- frequency noise and prevent DC bias ampllRca- tlon. Applying the values of this filter to the cutoff frequency equation yields a high-frequen- cj' cutoff point of 312 Hz. Below that frequency C8 will act as an open circuit, effectively remov- ing R2L so that the signal will not be amplified. At frequencies higher than 312 Hz, C8 will act as a short, and amplification will be determined by the values of feedback potentiometer R2 and filter resistor R2L The out- put of the amplifier stage is then AC coupled to ICl via coupling capacitor C4. The audio input from the handset microphone goes to ICl, and the output audio at pin 10 of that IC must be interfaced with the telephone base. This Is done by applying it to the base of transistor Ql, The current to Ql is limited by R20 to prevent saturation. As the applied base voltage changes, Qls collector current will vary accordingly A change in collector current causes a direct change in collec- tor- to- emitter voltage across the transistor. This voltage Is s! miliar to the voltage at JU4 which was derived for the hand- set interface. Lin^ from both collector and emitter of Ql con- nect the microphone input to the telephone base. The tele- phone base sees transistor Ql as a microphone. The resistance of potentiome- ter R2 was selected as 500 K to permit varying the amplifica- tion of the audio input. That po- tentiometer varies the audio applied to the base of Ql. The FIG. 6— PHOTOGRAPH OF LOADED BOARD for the TVS250. circuit pennits the user to ad- just the transistor drive as well as compensate for Internal cir- cuit differences in telephones. Constnictioii Because of the complexity of the telephone voice scramblen the double-sided PC board made with the foil patterns shown in this article is recom- mended. The finished PC board is available both as a separate Item or as part of the complete kit available from the source given in the Parts List. Begin the assembly of the tele- phone voice scrambler by inser- ting and soldering fixed re- sistors R3 to R21 where shown on parts placement diagram Fig. 5. {Figure 6 is a photograph of the loaded circuit board.) In- sert and solder potentiometers Rl and R2, Do the same for non- polarized capacitors CI to C15, Next, insert and solder polar- ized capacitors C16 to C18* not- ing their polarity. Ti'im all excess lead lengths. PARTS LIST All resistors are V^-watt, 5 %, un- less otherwise noted R1— 100.000 ohms, PC-mount po- tentiometer, screwdriver adjust R2— 500.000 ohms, PC-mount pen tenliometer, screwdriver adjust R3, R4— 10,000 ohms R5, R6— 3900 ohms R8, R9— 100.000 ohms R10-R13— 1000 ohms R7, R14, R15— 51,000 ohms R1&-R1S— 2200 ohms R19— 10,000.000 ohms R20— 150,000 ohms R21— 5100 ohms Capacitors CI, C2— 15 pR ceramic disc C3-C1 0—0,1 jiR metal film C11, 012— 2200 pF, ceramic disc C13-C15— 0.001 jiF, ceramic disc C16— I^F, 35 volls. tantalum CI 7, CIS— 10 fiR 16 volls, eiec- tfolylic, polarized Semiconductors iCl— GOIVI9046 voice-scrambfing IC, (Standard Microsystems) IC2— MC34119, audio amplifier driver (Motorola or equiv.) 103 — LM358 dual operational am- plifier, single supply IC3— 78L05A, 5'volt regulator (Texas Instruments or equiv,) 01— 2N2222A, NPN transistor LED1— green light-emitting diode, T1, Smm LE02 — red light*emitting diode, T1, Smm Other components 51— SPST slide, PC-mount, side- actuated switch 52— SPST stide, PC-mount, top- actuated switch 53— S6— STS2400 PC. 2P4T slide, PC-mount, top-actuated (Augat/ Alcoswitch or equiv.) switch Jt. J2™telephone jack, 4-4^ Type 616. PC-mount JU1-JU4 — two-post jumper, inch'On-centers with insulated shorting c1ips(sea text) XTL1— crystal 3.579545 MHz, met- al case (tTT 4183 or equiv.) B1— 9-voIl transistor battery, al- kaline, standard Miscellaneous: TVS250 PC board, S-inch length of telephone cord terminated with standard telephone plugs, 9-volt transistor- battery clip-type holder (Key* stone No. 79 or equiv.) with two 2-56 screws and nuts, 9-volt tran* sislor battery terminal snap with leads, four rubt>er or pJastic PC board feet (see text)* and solden Note: The following parts are available from Securicom, P.O. Box 5227, Chatsworth, OA 91 31 3-5227 (61 8)-71 0-0110 • COM9046 scrambler/de- scrambler IC only— $18.00 • Double-sided, silk^screened and drilled PC board— S2D.00 • A complete kit including PC board, all components, and 5- inch plug-terminated phone cord— S59,95 • Assembled and tested TVS250 with user's manual— S79.95 Check, money order, and Master- card orders accepted. Please add $3.75 for postage and han- dling. California residents must add 6.5% sales tax. TOP LAYER (COMPONEI^T SIDE) of telephone voice scrambler eOTTOM LAYER (SOLDER SIDE) of telephone voice scrambler PC board shown actual size. PC board shown actual size. 41 Then insert the jumper posts, switches. LEDs, crystal, and telephone jacks where shown on Fig. 5. (Place the shorting clips {see Fig. 7) on the jumper posts JU 1 to JU4 to prevent los- ing themj All switches can be inserted in only one position. Orientation is not critical for In- serting the cr)^stal XTALl, Note that the flats at the base of LED I and LED2 are next to their cath- odes. Solder all leads or wires and trim excess lengths. Assemble the 9- volt battery holder to the PC board with screws and nuts. Insert the red and black insulated wires of the battery terminal snap in the PC board with the black wire in the hole marked and the red wire In the hole marked + " as shown in Fig. 5- After soldering the wMres, trim their ends. Insert ail semiconductor de- vices (ICl to IC4 and transistor Ql) where shown In Fig, 5 last. Be sure to note the dots or notches that indicate the pin 1 positions on ICl to IC3, and the orientation of 1C4 and Ql, Ob- ser\T all precautions necessary to prevent electrostatic dis- charge damage of these devices. Solder their leads and trim ex- cess lengths. Make a careful visual exam- Ination of the soldered side of the PC board to be sure that all connections are sound and clean and that no stray solder has shorted any of the traces to- gether Remove any unwanted "bridging" by standard deso- Idering techniques or a sharp knife blade. Connectiiig the scrambler Connections to the kUephone line are well defined and stan- dardized, but there are no stan- dards for the wiring that connects a specific telephone handset to its base. The TVS250 was designed to adapt to a variety of telephones. The four wires inside the retractile telephone cord that connects the handset to the base are usu- ally color coded black, red, green and yeliou^, T\vo of these wires go to the handset speaker, and two go to the handsel microphone. Unfortunately telephone man- ufacturers have not agreed on PC BOARD Ra 7— SHORTING CUPS ON JUMPER POSTS are removed while adapting the TVS250 to a spedfic terephone. CONHECTlQIiTO BASE - BASEAyorOGNO HANDSET SPEAKER S3 QT EMinER S4 Ql COlLiCTOR S5 BASE AUDIO SIGNAL HANDSET SPEAKER S6 COWriECTfON TO ttANOSET FIG. 3— FUNCTIONS OF THE FOUR SWITCHES S3 ta S6 that adapt the TVS250 to a specific telephone. either the color coding or func- tion of those wires. The four two-pole* four-throw switches (S3 to S61 control the handset wiring order By chang- ing the actuator positions of these switches, any cord wiring configuration can be accommo- dated by the TVS250, Figure 8 shows the functions of each of those four switches. After some experimentation. It should take only a minute or SO to arrange the switch actu- ators to accommodate varia- tions in cord wiring. The easiest method for connecting the TVS250 to your particular tele- phone is as follows: 1) Set the midpoints of potenti- ometers HI and R2 by turning their control knobs with a screwdriver so that their arrows point toward the bottom of the PC board, 2) Switch SI to Its OFF position. Attach the terminal clip to the 9- volt transistor battery and snap the battery Into its spring hold- er on the circuit board. 3) Connect the TVS250 to your telephone by plugging one end of the five-inch phone cord into the telephone base and the other end into phone jack Jl, Then plug the retractile cord that normally connects the handset to the base Into jack J2 and hang up the phone. 4) Remove the shorting clips from posts JUl to JU4. This re- moves switches S4 and S5 from the circuit (see Figures 4, 5, 6, and 7). 5) Caution: Be sure that none of the actuators of the four switch- es S3 to SB are in the same posi- tions (see Fig. 91 if the jumper post shorting clips remain in place and two of the switches are in the same position, the unit will malfunction ♦ More- over, power Indicator LEDl (green) mighl not light. The re- moval of the four shorting clips prevents this. 6) Move SI s actuator on and green LEDl should light. Move S2s actuator back and forth and red LED2 should turn on and off. When red LED2 is il- luminated, the scrambler is in the scrambled mode. Before continuing, be sure red LED2 is off I norma/ model. When config- ured properly the actuators of S3 to S6 will be in one of four possible positions as showTi in Fig, 9. Remember that no two switch BCtuBtors should be set in the same position. Switches S3 and S6, which control the handsel speaker connection, should be adjusted first. To lind the proper switch settings for the handset speaker, listen for the phones dial tone, 7) Set S3's actuator to position 1* pick up the phone, and listen normally. Now move S6s actu- ator in sequence to positions 3, 4 and then 5. If you hear a dial tone in any of tJiose actuator po- sitions, leave it there. If no tone is heard » move S3s actuator to position 2 and again tr^^ S6 s ac- tuator In the other three posi- tions. Continue this procedure until the dial tone is heard. While the complete procedure should lake only about a min* ute* remember that If a handset is left off of its base (hook) for more than about 15 seconds, the dial tone will automatically turn off. Hang up the phone be- tween actuator settings to be sure that a dial tone is present when the right combination is found, 8) With the dial tone present, adjust potentiometer Rl to the desired volume, 91 Him the TVS250 off (green LEDl is off]. Place the shorting clips on all four jumper posts. After the dial tone Is heard, the handset microphone switches S4 and S5 can be adjusted. For this step ask someone to assist you by listening in on an exten- sion to your phone. 10) Set the actuator of S4 to one of the positions not used by S3 or S6, and set S5s actuator to the last available position. Turn the TVS250 on after making sure that it is set for normal mode (red LED2 is off) Ask your assistant on the extension to pick up the handsel and key In any number to eliminate the dial tone before proceeding. Then speak normally Into the handset. Your assistant can tell you if the sound volume is with- in normal limits. Then adjust potentiometer R2 for the best speech quality^. If, after adjusting R2, you cannot obtain quality speech, it is probable that the actuators for switches S4 and S5 are In reversed positions. (This can be determined if your assistant's voice seems distant or in- comprehensible even after you have turned R2 both completely clockwise and counterclock- wise. A screeching sound might also be heard J If this is the case* simply switch the actuator posi- tions of S4 and 85 and repeat the adjustments to R2 while speaking to your assistant. The positioning of actuators of S3 and S6 is critical. If you still cannot get quality speech from your phone after perform- ing the previous procedure, the positions of actuators of S3 and S6 are reversed. Exchange their positions and repeat step 10. Although the TVS250 is rug* ged and will not require special handling, the unprotected cir- cuit board must not be placed in any position where conductive P0SfTK}N2 POsrriOH3 posmOMi r*- S3 S4 85 I t I I [ 1 1 1 . H — I- J — t — h -1-1 ;. ...1 . t 1 t 1 i 1 1 SUD€ SWITCHES FEG. FOUR POSSIBLE ACTUATOR SETTINGS Of Ihe two-pole, four-throw slide switches S3 to SB that adapt the TVS250 to a specific phone. surfaces could short out un- protected soldered connections on the underside of the board. The Insulating feet at the cor- ners of the PC board s underside will help to prevent damage from this cause by elevating it above any ilat surface on which it is positioned. However, you might also want to enclose your scrambler in an insulated pro- tective case for more protection. After the fine adjustments have been made, your voice scrambler will be ready for use, but. of course, two scramblers are needed to form a system. Make the following simple test: • 'mm on the TVS250 with SI noting tliat green LEDl is on. • Pick up the handset and lis- ten for the dial tone, • Switch S2 to the scrambled mode (red LED2 is on). • Listen for the scrambled dial tone. • Change back to normal mode and phone someone. • Speak normally into the phone with the scrambler mode off (green LEDl is always on when using the phone). • Switch the unit into the scrambled mode (red LED2 is on)* • As the other party speaks, you will hear his scrambled speech and he will hear yours, • Switch back and forth from the scrambled to the normal mode as often as necessary to check out a single unit, Wlicn two tested scramblers on the same line are in the scrambled mode, both your voice and that of the person you called will sound normal. Any- one listening on extensions to either phone will only hear garbled speech. Scramblers should be turned off when a call has been com- pleted to conserve battery power. In continuous opera- tion, a 9-volt alkaline battery will provide about 30 hours of scrambler operation. Answermg and call waiting The scrambler can leave se- cure messages on an automatic answering'machine. Tlirn on your scrambler and speak nor- mally to any telephone with both a compatible scrambler and answering machine. When a receiving party plays back your message and hears the garbled speech, he turns on his scrambler and listens to your normalized speech through his handset. The T\^S250 can be switched back and forth from scrambled to normal mode at any time dur- ing a conversation. If you have call waiting, you could be in a secure conversation with an- other party whose telephone has a compatible scrambler when you are interrupted by an- other caller Tb answer the call waiting signal, simply switch your scrambler to its normal mode and answer the call as usual. After the call is com- pleted, return your unit to the scrambled mode and continue your secure conversation, r-e OPTOCOUPLER DEVICES Learn to use optocouplers in circuits that require high electrical isolation between input and output. I c 6 yj 44 RAY M. MARSTON OITOCOUPLERS OR OFTOISOIJ^TORS have applications in many sit- uations where signals or data must pass between two cir- cuits, but high electrical isola- tion must be maintained be- tween those circuits, Optocoup- Ung devices are useful in changing logic levels between the circuits, blocking noise transmission from one circuit to anothen isolating logic ieveis from AC-iine voltage, and eiim- inating ground loops. DC level as well as signal in- formation can be transmitted by an optocoupler while it main- tains the high electrical isola- tion between input and output. Optocouplers can also replace relays and transformers in many digital interfaces. More- over the frequency response of optocouplers is excellent In ana- log circuits, Optocoupler basics. An optocoupler consists of an infrared-emitting LED (typ- ically made from gallium arse- nide) optically coupled to a silicon photodetector (photo- transistor photodiode or other photosensitive device! in an opaque light-shielding pack- age. Figure I is a cutaway view of a popular single-channeL six- pin dual-ln-line-(DIP) packaged optocoupler The IR-emittlng LED or IRED emits infrared ra- diation in the 900- to 940- nanometer region when for- ward biased current flows through it. The photodetector is an NPN phototransistor sen- sitive in the same 900- to 940- nanomeier region. Both IRED and phototransistor are In chip or die form. PLAST!G PACKAGE UGHT-CONDUCirNQ MATERIA! AflOUND SOURCE AND DETECTOR IR SOURCE LED FIG. 1— CUTAWAY VIEW OF AN OPTOCOUPLER wllh a phototransistor output Most commercial opto- couplers are made by mounting the IRED and phototransistor on adjacent arms of a lead- frame, as shown. The leadframe is a stamping made from thin conductive sheet metal with many branch-like contours- The isolated substrates that support the device chips are formed from the inner branches, and the multiple pins of the DIP are formed from the outer branches. After the wire bonds are made between the device dies and ap- propriate leadframe pins, ttie region around both devices Is encapsulated in an !R- trans- parent resin that acts as a "light pipe*' or optical waveguide be- tween the devices. The assem- bly is then molded in opaque cpojcy resin to form the DIR and the leadframe pins are bent downward. Figure 2 is a pin diagram of the most popular single-chan- nel, 6-pin pjiototransistor op- tocoupler DIP It is called an 1 6 2 5 3 FIG, 2-TOP VIEW SCHEMATIC of a ph ototra n si s to r-^ u tput o ptoc o u p le r. oplocoupler because only in- frared energy or photons couple the input IRED to the output phototransiston The device is a!so an optoisolator because no electric current passes between the two chips: the emitter and detector are electrically insu- lated and isolated. These de- vices are also known as photo- coupler or phoion-couplcd iso- lators. The base terminal of the pho- to transistor is available at pin 6 on Uie six-pin DIR but in nor- mal ues it is left open-circui ted. Also, no connection (NC) is made to pin 3. The photo tran- sistor can be converted to a pho- todiode by shorting together base pin 6 and emitter pin 4. That option is not available in four-pin optocoupler DIPs and multi-channel optocouplers. There are, however photodiode- output optocoupiers optimized for the wider bandwidth and higher speeds needed in data communications, but they are far less efficient as couplers* Large-volume producers of commercial optoc ouplers in- clude Motorola. Sharp Elec- tronics Corp.. and Siemens Components, Inc. Optek Tech- nology concentrates on optoin- terrupters and optorenectors while Hewlett-Packard s op- tocouplers are focused on high- speed communications and special applications. Optocoupler characteristics One of the mosl important characteristics of the op- tocoupler is its light-coupling efficiency specified as current transfer ratio. CTR. That ratio is maximized by matching the IRED's IR emission spectrum closely with its detector/output devices detection spectrum. CTR is the ratio of output cur- rent to input current, at a spec- ified bias* of an optocoupler. H is given as a percent; CTR = [Ict:oJ^tJF) >^ 100% A CTR of 100% provides an output current of 1 milliampcrc lOOr 50 1 10 1 ^ 1 to m INPUT CURflEMT. l^mA) FfG. 3— TYPICAL OUTPUT CURRENT vs. input current for a pholotranststor-output optocoupler with a Vcb c>MO volts. for each mllliampere of current to the IRED. Minimum values of CTR for a pho tot ransis tor-out- put optocoupler such as that shown in Figs. 1 and 2 can be expected to vary from 20 to 100 %- CTR depends on the input and output operating currents and on the phototransistor s supply voltage. Figure 3 is a plot of phototran- sistor output current {1^.^^} vs. input current (If J for a typical phototransistor optocoupler at a collector- to-base voltage (V^^) of 10 volts. Other Important oplocoupler specifications include: • Isolation voltage (Vj^<^j). The maximum permissible AC volt- age that can exist between the input and output circuits with- out destruction of the device. Those values typically range from 500 volts to 5 kilovolts RMS for a phototransistor-out- put coupler • ^CE' maximum DC volt- age permitted across the pho- totransistor output. Typical values for a phototransistor - output coupler range from 30 to 70 volts. • Ip The maximum continuous DC forivard current permitted to fiow in the IRED, Typical val- ues for a phototransistor-out- put coupler range from 40 to 100 milliamperes. • Rise/fail time for a phototran- sis tor-out put coupler is typ- ically from 2 to 5 microseconds for both rise and fall. Those de- termine device bandwidth, Indus try- s tandard s A wide variety of optocouplers is produced by many manufac- turers throughout the world* Some of the suppliers of com- modity optocouplers Include Motorola, Sharp Electronics, ^ Toshiba, and Siemens. In addi- g tion to the industry standard S six-pin DIP shown in Figs. 1 and s 2, some Lransis tor-output op- % tocouplers are packaged in four- E pin DIPs and surface-mount E packages, 1 Multi-channel configurations §" of the popular optocouplers are ^ also available with dual and * quad emitter-detector pairs per package. Those optocouplers repeat the basic schematic of 45 Fifl. 2 excepi thai they lack ex- tcrnaJ base pins. It is important to note, however, that certain electrical and thermal charac- teristics are derated in those packages because of the closer spacing of the semiconductor dies. The lowest cost industry- standard phototransistor op- tocouplers with single channels have been designated bv the JEDEC prefix 4N' and include tile 4N25 to 4N28 and 4N35 to 4N37, However, many suppliers have developed their own pro- prietary parts with unusual fea- tures which are sold under their own designations. Popular pho- totransistor op tocouplers are now available in small quan- tities for less than a dollar each. Because optocouplers are used in AC-line powered cir- cuits, they are subject to safety tests such as those of Under- writers Laboratories Inc. (UL) and Canadian Standards As- SDsiation ICS A), Most suppliers are offering UL-Recognized op- tocouplers and many "make cou- plers that conform to the tighter Verband Deutsch Electro- techniker (VDE) specifications. Compliance with those specifi- cations or the equivalent na- tional spec ificai ions is a man- datory requirement for their use in Europe, Figure 4 illustrates a simple optocoupler circuit. The con- duction current of the pho- totransistor can be controlled by the forward bias current of the I RED although the two de- vices arc separated. When SI is open no current flows in I he IRED so no infrared energy falls on the phototransistor making it a virtual open-circuit with zero voltage developed across FIG. S— AC INPUT PHOTOTRANSISTOR- oulput optocoupler schematic FIG. 6— PHOTDDARLINGTON-OUTPUT optocoupler schematic. FIG. 7— Bi-DIRECTIONAL LINEAR out- put optocoupler schematic showing MOSFET output. FIG. 8— PHOTOSCR-OUTPUT opto- coupler schematic. 1 B 2 5 3 A FIG, 4— CIRCUIT for phototranslstor- output optocoupler FIG, 9-PHOTOTRrAC-OUTPUT opto- coupler schematic. output resistor R2. When SI is closed, current flows through the IRED and Rl , and the resuU- inji IR emission on the pho- totransistor causes it to con- duct and generate an output voltage across R2, The simple optically*coupled circuit shown in Fig. 4 will re- spond only to on-off signals, but it can be modified to accept ana- log input signals and provide analog output signals as will be seen later The phototransistor provides output gain. The schematics of sLx other optocouplers with different combinations of IRED and out- put photodetector are presented as Pigs. 5 thru 10. Figure 5 Is a schematic lor a bidirectional- input phototransistor-output optocoupler with two back-to- back gailiutTi-arsenide IREDs for coupling AC signals or re- verse polarity input protection, A typical minimum CTR for this device is 20%. Figure 6 illustrates an opto- coupler with a silicon pho- todarlington amplifier output. It provides a higher output cur- rent than that available from a phototransistor coupler. Be- cause of their high current gain. Pho todarlington couplers typically have minimum 500% CTRs at a collector-to-emitter voltage of 30 to 35 volts. This value is about ten times that of a phototransistor optocoupler. However, there is a s peed -out- put current tradeoff when using a photodarlington cou- plcn Effective band with is re- duced by about a factor of ten. Industry standard versions of those devices include the 4N29 to 4N33 and 6N138 and 6N139. Dual* and quad-channel pho- todarlingtoti couplers are also available* The schematic of Fig. 7 iilus- trates a bi-directional linear- output optocoupler consisting of an IRED and a MOSFET. Those couplers t>^ically iiave isolation voltages of 2500 volts RMS. breakdown voltages of 15 to 30 volts, and t>pical rise and fall times of 15 microseconds each. Figure 8 is the schematic for one of two l^asic t^'pes of opto- t liy r is t o r- o u t p u I op tocou piers, FtG. 10-^SCHMITT^TRJGGER-OUTPUT optocoupier schematic. FIG- t1— SERIES RESISTOR must limit tREO current. It can be R1 at (a) or R2 at RG. 12— IRED IS PROTECTED against reverse voltage with external diode D1. one wilh an SCR oulpul. Op- toSCR couplers have typical iso- lation voltages of 1000 to 4000 volts I^S. minimum blocking voltages of 200 to 400 volts, and maximum lurn-on currents (Ip,^) of 10 milliampcres. The schematic in Fig. 9 illustrates a phototriac -output coupler Thy- rislor-output couplers typically have forward blocking voltages '^drmJ of "100 volts, Schmitt-trigger outputs are available from optocouplers. Figure 10 is the schematic for an optocoupler that Includes a Schmitt-trigger IC capable of producing a rectangular output from a sine-wave or pulsed in- put signal. The IC is a form of multivibrator circuit. Isolation voltages are from 2500 to 4000 volts, maximum, turn -on cur- rent is typically from 1 to 10 mil- Itamperes, the minimum and maximum operating voltages are 3 to 26 volts » and the max- imum data rate (NRZ) is 1 MHz. Coupler applications Optocouplers function in cir- cuits the same way as discrete emitters and detectors. The in- put current to the optocouplers IRED must be limited wilh a se- ries-connected external resistor which can be connected in one of the two ways shown in Fig 10» OUTPUT FtG, 13— EXTERNAL RESISTOR wired at phototransistc^r collector (a) or emitter {by either on the anode side (a) or cathode side (b) of the IRED. Figure 5 showed an op- tocoupler optimized for AC op- eration. but a conventional phototransistor coupler can also be driv^en from an AC source with the addition of an external conventional diode as shown in Fig. 12, That circuit also provides protection for the IRED if there is a possibility FIG. 14~PH0T0TRANSIST0R-T0- photodiode conversion witli base pin connection. thai a reverse voltage could be applied accidentally across the IRED. The operating current of the couplers phototransistor can be converted to a voltage by plac- ing an external resistor in series with the transistors collector or emitter as shown in Fig. 13, The collector option is shown in (a} and the emitter option is shovra in (bK The sensitivity of the cir- cuit will be directly proportional to the value of either of the se- ries resistors. A phototransistor-output op- tocoupler in a six-pin DIP can be converted to a pho tod lode-out- put optocoupler by using the base pin 6 as shown in Fig, 14 and ignoring the emitter pin 4 (or shorting ii to the base). This connection results in a greatly increased input signal rise time, but it sharply reduces CTR to a value of about 0.2%. Digital interfacing. Optocouplers are ideally suit- ed for interfacing digital signal circuits that are driven at dif- ferent voltage levels. They can interface digital ICs within the same TTL, ECU or CMOS family, and they can interface digital ICs between those families. The devices can also interface the digital outputs of personal com- puters (or other mainframe computers^ workstations and programmable controllers) to motors, relays, solenoids and lamps. Figure 15 shows how to inter- face two ITL circuits. The op- tocoupler IRED and current- limiting resistor f^l are con- nected between the 5 -volt positive supply bus and the out- put driving terminal of the TTL logic gate. This connection is made rather than between the TTL gate's output and ground because TTL outputs can sink fairly high current (typically 16 milliamperes). However TTL outputs can only source a veiy low current (typically 400 mi- croamperes). The open-circuit output volt- age of a TTL IC falls to less than 400 millivolts when in the logic 0 state, but It can rise toonlv2.4 volts in the logic 1 state if the IC does not have a suitable inter- FIG. 15— TTL-GATE INTERFACE provided by a phototransistqr, outpyl optocoupler. FIG, IB— CMOS'GATE INTEFIFACE provided by a phototransistor-oylput optocoupler FfG, tS — AUDIO INTERFACE provided by a pliototransistor^output optocoupler. nal pull-up resistor. In that case* the optocoupler's IRED current will not fall to zero when the TTL output is at logic L This drawback can be overcome with external pull-up resistor R3 shown in Fig, 15, The optocouplers phototran- sistor should be connected be- tween the input and ground of the TTL IC as showTi because a TTL input must be pulled down below 800 millivolts at 1.6 mllll- amperes to ensure correct logic 0 operation. Note that the cir- cuit in Fig, 15 provides non-in- verting optocoupllng. CMOS IC outputs can source or sink currents up to several milh amperes with equal ease. Consequently, these ICs can be interfaced with a sink config- uration similar to that of Fig 15, or they can be in the source con- figuration shown in Fig. 16, In either case, R2 must be large enough to provide an output voltage swing that switches fully between the CMOS logic 0 and 1 states. Figure 17 shows how a photo- transistor-output optocoupler can interface a computers dig- ital output signal (5 volts, 5 mil- Uamperes) to a 12-volt DC motor whose operating current is less than 1 amp. With the computer output high, the optocoupler IRED and pholotransistor are both off. so the motor is turned on by Ql and Q2, When the com- puter output goes low, the IRED and phototranslstor are driven on» so QL Q2 and the motor are turned off. Note the 1-ampere current limitation. Analog interfacing An optocoupler can interface analog signals from one circuit to another by setting up a "standing" current through its IRED and then modulating that current with the analog signal. Fig 18 shows this method ap- plied to audio coupling. The op- erational amplilier 1C2 Is con- nected in a unity-gain voltage- foil owe r mode. The op- tocouplers IRED is wired into the op-amp's negative feedback loop so that the voltage across R3 (and Ihus the current through the IRED) precisely fol- lows the voltage applied to non- inverting input pin 3 of the op* amp. This pin is DC biased at half-supply voltage with the RI- R2 voltage divider. The op-amp can be AC modulated with an audio signal applied ai CI. The quiescent IRED current is set at 1 to 2 milliamperes with R3. On the output side of the cou- pler a quiescent current is set up by its transistor. That cur- rent creates a voltage across po- tentiometer R4 which should have its value adjusted to give a 27m IHPUT FROM COliTROl ancurr IC1 CI r +1 FIG. 19— NON-SYNCHRONOUS TRIAC power switch with optocoupled inpuL INPUT FROM CONTROL ClRCUtT J> R5 C3 4m VAC FtG. 20— SYNCHRONOUS TRIAC power switch with optocoupled input. mm mm COHTRDL CmCUlT (20rtiA} + V Rl — SI ICl LMP1 <100niARMS <1.2A PEAK 117 ■ VAC FIG. 21— INCANDESCENT LAMP CONTROL with a Triac-driver output optocoupler. Rl CONTROL CIRCUIT SI ICl R2 ma LOAD ^117 '^VAC FIG. 22— HIGH-POWER LOAD CONTROL with Triac-driver output optocoupler. i +VR1 INPUT FHOM * ^ CONTROL t20mAJ ,»_cro- S1 ICT R? R3 LOAD I SgTEXTf TR1> 4^ X —I I T T R4 10011 C2 4IMV 117 VAC FIG, 23— INDUCTIVE LOAD CONTROL with Triac-driver output optocoupler and (riac stave. quiescent oulpul equal to halt" the supply voltage. The audio- output signal appears across potentiometer R4. and it Is de- coupled by C2. TtiRC interfacmg* [nterfacing the output of a low- voltage control circ uit to the input of a Triac power-control circuit driven Irani the AC line is an ideal application for the optocoupler (It is advisable that one side of its power supply be grounded.) That arrangement shown in Fig, 19 can control the power to lamps, heaters, motors and other loads. Figures 20 and 21 show prac- tical control circuits. The Triacs should be selected to match load requirements. The circuit in Fig. 19 provides non-syn- chronous switching in which the Triacs initial switch-on point is not synchronized to the 60-Hz voltage waveform. Here. R2. Dl Zener diode D2 and CI develop a 10- volt DC supply from the AC line. This voltage can be fed tt> tlie 'IVlac gate with Ql. which turns the Triac on or off. Thus, when SI Is open, the optocoupler Is off, so zero base drive is applied to Ql (keeping Triac and load oiT). When SI is closed, the optocoupler drives Ql on and connects the 10- volt DC supply to the Tibiae gate with R3, thus applying full line volt- age to the load. The circuit in Fig, 20 includes a silicon monolithic zero-volt- age switch, the CA3059/ CA3079. sou reed by Motorola and Harris Semlconducton That IC with a phototransistor- output optocoupler provides s\TichronouB power switching. The gate current is applied to the Triac only when the in- stantaneous AC line voltage is within a few volts of the zero cross-over value. This syn- chronous switching method permits power loads to be switched on without generating sudden power surges (and con- sequent radio frequency inter- ference [RFH in the power lines]. This scheme is used in many factory-made solid- state relay modules. PtiotoSCR*s and Photo'niacs Both photoSCK and photo- Triac-output optocou piers have rather limited output-current ratings. However, in common wMlh other semiconductor de- vices, their surge-current rat- ings are far greater than their RMS values. In the case of the SCR. the surge current rating is 5 amps, but this applies to a 100 microsecond pulse width and a SLOT Ra 24— OPTICALLY-COUPLED INTERRUPTER MODULE (a) and speed counting ap- pticatlon (b). RG. 25^PnCALLY COUPLED REFLECTOR MODULE (a) and rBvolution counting application (b). duty cycle of less than 1 % . In the case of the T)-iac. the surge rat- ing is L2amps, and this applies to a 10 microsecond pulse width and a maximum duty cvcle of 10%. The input IRED of oplo- coupled SCR s and Triac s is driven the same way as in a photolransistor-output op- locouplen and the photoSCR and photoTriac perform the same way as their conventional counterparts with limited cur- rent- handling capacitvi Figures 2K 22, and 23 illustrate prac- tical applications for the photo- IViac-output optocoupler In all circuits Rl should be selected to permit an IRED forward cur- rent of at least 20 miUiamperes, In Fig. 21, the photoTViac di- rectly activates an AC-tine- powered Incandescent lamp, which should have an RMS rat- ing of less than 100 milll- amperes and a peak inrush current rating of less than L2 amps to work in this circuit. Figure 22 shows how the photoTriac optocoupler can trigger a slave Triac, thereby ac- tivating a load of any desired power rating. This circuit is only suitable for use with non- inductive (i ic=:> APFlJOAtECi ;:;;!jE::i;;t?!j;: FJG. 3— REPEATERS, bridges, routers, and gateways work at progressivaly higher levels of the OSI stacJ<. Every 8.2 feet a transceiver can tap into the backbone, and from the transceiver a cable drops down to an attached workstation, file sender, PC. or other device. Most thick Eth- ernet LANs use RG-58 coax with BNC connectors as drop cables. However there is a grow- ing tendency to use twisted-pair cable with RJ-45 modular con- nectors in more recent Ethernet installations. The maximum length of a thick Ethernet segment is 1640 feet; the maximum number of transceivers per segment is 100. To extend that maximum distance or add units* a re- peater must be used. Thin Ethernet (sometimes called Cheapernet) uses RG-SS coax (10Base2) that snakes di- rectly from machine to machine using T connectors. In this set- up, the transceiver mounts di- rectly on the network interface card in the PC or other device. The maximum length of a thin Ethernet segment is 607 feet, with a maximum of 30 devices per segment Ethernet also runs on un- shielded twisted pair (lOBaseT) in a star topology. The max- imum length of any segment from hub to workstation is 328 feet. lOBaseT is growing in pop- ularity due for the most part to its low cost and easy configura- tion with modular telephone- style connectors. Last, Ethernet runs on fiber cables, including 50-. 62.5-, and 100-micron duplex and plenum duplex cables. Cur- rently (unless cost is no object), fiber is used mostly to link indi- vidual networks separated by some distance. Token Ring: Token Ring (IEEE 802.5) uses a token-pass- ing protocol, and runs at 4 or L6 Mbps. A given network (or sub- net) runs at either 4 or 16 Mbps, but it is possible to bridge ^Ibkcn Ring nets running at different speeds. Token-ring topology is some- what more complicated than the name might suggest, as shown back in Fig. 1. Note that the ring really consists of a ring of Media Access Units (MAU's), Continued on page 66 IN THE EARLY EIGHTIES there was no easy way for personal computers and control circuitry to intcF act with each other The Interfaces that were avail- able were cumbersome and expensive. Today, however, real-world inter- faces like our Ti003 let your PC receive and send both analog and digital signals. The T1003 Is ca- pable of24-blt digital I/O, eight channels ofS- or 12- btt analog-to-digital con- version » and a single 8- bit digital-to-analog con- version< The T1003 comes with easy-to-use software that allows you to quickly con- figure every aspect of the unit* As an example of what the T1003 can be used for, the softft^are in- cludes a storage-os- cilloscope program that lets you monitor eight low-frequency voltages graphically and save the results to disk. 24-blt I/O port Look at the block di- agram In Fig. I. The I/O section is composed of one IC (an 8255 program- mable peripheral inter- face, or PPl). The IC Is configurable as three 8- blt ports or two 8-bit ports and two 4-bit ports. Additionally, each port can be configured for ei- ther input or output using the software included with the T1003. The output DAC (D to A Con- verter) sect ion consists of a data latch, a DAC IC {a DAC0800 or DAC08). and an operational amplifier Any byte sent to the DAC section will be output as a voltage between 0 and 5 volts at pin 33 of the terminal block (TBl-33). The A/D section uses three analog signals: V^KF^a* ^in-* and V,f^^, V|^EF/2 *^ used as a reference vol tage by the A/D con- verter From that voltage the A/D establishes full scale. If Vj^p^ ts 2.500 volts, full scale is 5.000 60 volts. If the byte read back from PC-BASED TEST BENCH sent The T1003 has 24'bit digital I/O, 8 channels of 8- or 12-bit AID conversion, and a single 8'bit D/A conversion. STEVE WOLFE the A/D converter is 128 (10000000), the voltage being measured at V,t^ ^ is 2,500. This assumes that Vjj^, is set to 0 volts. Vjj^_ is similar to the ground lead of a voltmeten It Is grounded during operation. The A/D converter measures the difference between V|j^^ and V|,^_. The analog multiplexer section is software addressable. Address values of 0 through 7 cause channels 1 through 8. re- spectively, to be connected to the A/D converters Viiq^ pin. The A/D converter used In the T1003 (an ADC0803} is an 8 bit device. A 5-volt 8-bil device is typically capable of approxi- matelv 20-milUvoU resolution steps. To achieve 1-mSlli- volt resolution (greater than 12 bits), the reference multiplexer is set to pass 2.5 volts to the V,^£p^ pin. The reference DAC which is connected to V^f^_ is set to 0 volts. The analog mul- tiplexer is set to connect one of its 8 channels to V^^ The A/D converter ts a start conversion pulse and, after 100 micro- seconds (conversion time), it is ready to return the val- ue measured. The value measured Is then read back into the software. The reference multiplex- er is now re-addressed to pass 128 mi Hi volts to the A/ D converters Vi^^^^^-^^ pin, so full-scale ts set to 256 milli- volts. Since our A/D con- verter has a total of 256 counts (0^-255), the T1003 is now set to a resolution of 1 miUlvoU per count. How- even we arc not yet home free. If we arc measuring 3 volts, then we are, in es- sence, measuring 3000 millivolts. If ViN_ is still set to 0 volts, then we will over- run our A/Djs capability by 2745 millivolts. That would yield a reading of 255 which, in this case, would mean overrange. In- stead, we will set the refer- ence DAC section two counts (40 millivolts) be- low what we measured using the 20 millivolt mode. The V|jy_ is now 20 to 60 miUi- volts below the actual voltage being measured. While in the 1- millivolt mode we are able to re- solve 255 millivolts in 1-milllvolt steps. The A/D converter is again told to start conversion. The resultant reading is the number of millivolts to be added to the voltage we are producing at the reference DAC tV,j^_). First, we did a 20-milIlvolt con- version to determine a rough value of the voltage being mea- sured. Next, we adjusted V^^_ to a value just below the measured voltage and did a l-mlllivolt con- version. Vip,,_plus the 1-mlllivolt result equals the 1-milIivolt res- olution final value. A/D SECTION I DATA ANALOG MUX SECTION REFEREfJCE MUX SECTION FRONT DATA m$ TO EVERY SECTION CHIP SELECT SECTION J TO DACs «r RER MUX REFERENCE VOLTAGE SECTION RG. 1— T1003 SLOCK DIAGRAM. The 1/0 section contains an 8255 programmable peripheral interface (PPI), which Is confi9urable as three 6-blt ports or two 8-bit ports and two 4-bil ports. Each port can be configured for either input or output. is the LSB of the address lines. The chip-select section is made up of IC1-IC5 and IC19. (IC1-IC4 are 74HCT138^s; whenever g2a and g2B are low and Gi is high, one of eight out- puts will go low, depending on the address present at the a. d, and c: inputs.) Chip ICl is active when BEN is high and send is low. If ICl is inactive then IC2-IC4 are also inactive. If ICl is active and the address value is less than 8, then ICl pin 15 activates iC2. If the address in use is between 0 and 3 then 1019 activates 1C6 (the 8255). Therefore. ICS is active during writes and reads in the address range of BAS + 0 to BAS-fS. If the address is BAS + 4 , then the cnip SELECT line of the A/D con- verter is activated, allowing it to respond to read or write pulses. If ICl is active and the address Is between 8 and 15. then ICl pin 14 becomes active. If the func- tion is read, and the address Is 8, ICS pin 15 becomes active causing ICIO to move its latched data to the data bus. Chip ICIO holds seven hard- wired bits that are used to deter- mine whether the T1003 is at- T1003 PARTS LIST Detailed operation As was the case with the pre- vious IIOOQ peripherals, we'll continue using BASIC lan- guage. The first step in control- ling any 1 1000 peripheral Is to establish a base address and se- lect the desired peripheral. The first bit of code will be: BAS = 768 : out BAS 4- 31,3 768 (hex 300) is the factorj^-pre- set base address of the 1 1000. As noted earlier, the address is DIP- s witch selectable- Next, we have an OUT to BASH-3L As you might recall that address is re- served for peripheral selection. The T1003 has a unit or pe- ripheral address of "3." Con- sequently if 1 send an OUT to BAS -h 31 with a data byte of "3/" theT1003 will be readied for full I/O operation. Look at the schematic in Pig. 2. Address lines ah through Ay are used by the 1 1000 only and AO through A4 (32 bytes) are used by the peripherals to ad- dress their IC's, Address line ao All resistors are V^-watt, S%, unless otherwise noted R1— 2200 ohms R2, R4— 10,000 ohms R3— 33 ohms R5— not usect R6. RIO— 2320 ohms, 1% R7, Rtl, R16— 1000 ohms R8, Rt2"-5110 ohms, 1% R9, 2050 ohms R14— 1100 Ohms 240 ohms R17— 10,000 ohms, multiturn poientiometer R18— 1000 ohms, multiturn potentiometer R19. R20—5G0 ohms, multiturn potentiometer R21~5000 ohms, potentto meter Capacitors C1, C2, C5, C17, C24, 026, C31, C32, C35. C36, C45-C49— not used C3. C4, CIO, C12-C15, C19--0.15 f;F, ceramic C6, Clt C3S, C41, C4a— 100 ftp, 25 volts, electrolyttc C16. Cl8, C20-C22, C29, C39, 040, C42, C44, C50, C51— 10 fiF, 35 vpEts, etectrolytic C26, C33, C37. C52, C53~-2.2 fxF, 50 \.^3ts. electrolytic C27— 150 pF, mica C30, C34— 36 pF, mica Semiconductors IC1"1C4^74HCT136 3 to-S W multiplexer ICS— 74HCT540 octal inverting buffe IC6 — 8255A programmable peripheraJ^ interface IC7-JC9— TL082 dual JFET input op- amp ICIO, IC12, 1015. IC17— 74HCT573 oc- tal D-iype iatch IC11— ADC0803 S m A. D converter IC13. 1C14— 74HCT4051 8-channel multiplexer IC16. IC18— DAC0800 D/A converter iC19— 74HGT20 dual 4'input NAND gate 1020— LM336-2,5 reference diode 1C21— LM317T adjustable voltage reg- ulator IC22— LM340K-5.0 voltage regulator IC23— LM7905T negative 5-voEt reg- ulator D1^1N4002 diode Other components TB1 — two 16"P0sition termmal blocks TPVTP4, TPe^-PC-mounttest point TPS — not used Miscellaneous: IC sockets, 103 type heat^ink. instrumer^t case, wire, sol- der, etc- I to )9 N- m 3 a' z 61 s z 2 62 RG. 2— TI003 SCHEMATIC, The ch1p-s#lect section is made up of !Ct-^C5 and ia9. If tCI is [nacUve then IC2-IC4 are atso inactive. tached to the 1 1000. It is also used to check the A^D iNTERRUin^ line. The line Indicates whether the A/D has finished its con- version process. If ICl is active and the address is in the range of 16 through 23, then ICl pin 13 becomes active. If the fun- tion is a write, and the address Is in the range of 16 through 18. then IC4 pins 15 through 13 be- come active. The signals pass through ICS where they are in- verted. The three inverted sig- nals are used to load three latches; IC12, IC15, and IC17 re- spectively. OUTs and IN s in the range of BAS+0 to BAS + 3 activate IC6 (the 8255}. ^OUT BAS + 33YTE" Is used to configure the 8255 where "BYTE ' is the input/ output configuration. BAS-f 0 through BAS + 2 represent ports 1 through 3 respectively* If the 8255 is configured with port 1 an input, port 2 an output, and port 3 an outpui. then an * OUT BAS + 2,85" would place alternating ones and zeros on TBI pins 17-24. The line A = INP{BAS 0) : A = INP(BAS + 0)" would read into the computer the byte pres- ent on TBI pins 1-8, As you might recall from the previous articles, two input stalenients are used to read data. The first statement moves the data from the peripheral to the 1 1000. Tlie second statement moves the data from the 11000 to the com- puters memory (variable a). The voUage-relerence section generates the reference voltages used by the DAC and A/D con- verter sections. Five volts is ap- plied to Rl and subsequently IC20. an LM336 voltage reg- ulator Potentiometer R17 is ad- Justed for 2,5 voUs at TP6: the 2.5-voll reference is buffered by JC7-a. lC8-a, and IC9-a. and then sent to IC14, IC16, and IC18, The reference voltage is also sent through R2, R18, IC7- and across C26 and R3 (RI8 is adjusted for 128 millivolts at ICHpln 131 The output DAC section is composed of IC17, fC18, and IC9-b, An ^OUT BAS^17.BYTE" will cause a data byte to be load- ed into IC17, The data byte is converted to a current in ICI8, The current is fed to IC9-b where it is converted to voltage. The voltage is available to the user on TBI pin 33. Potentiome- ter R20 is used to adjust the full- scale voltage output to 5 volts. As for the A/D section, we'll Jump right to the explanation of the 12-bil mode because it In- cludes the 8-bit explanation. Lets assume that we want lo measure the voltage on TBI pin 25 using the I2*bit mode. First, we will do an "OUT to BAS 4- 16" with a data bvte of 8 [OUT BAS +16,8), Thal'causes 2,5 volts to pass through 1C14 and be applied to A/D converter ICll pin 9 {Vr^Ep,,^), It also ap- plies an address 'of 0 to IC13 which connects TBI pin 25 to ICll pin 6 (Vjj,^ J, Next, we will "OUT the value ' 0 ' LoBAS + 18. That causes the reference DAC I. 5 64 SOLDER SIDE of the T1003 board. to apply 0 volts to ICIl pin 7 i^m-l Now we are ready to start the A/D converter That is ac- complished by doing an ''OUT ' to BAS + 4, The data byte Is Jr- relevant when sending a start pulse so you can use any value you like (as long as it is in the range from 0 to 255), Next, we will read ICIO to see if the AID interrupt line has gone low (end of conversion). If it is still high, then the A/D has not finished, and we will read IClO again. When IClO's LSB goes low the A/D converter is ready to be read. A pair of inputs to BAS + 4 brings the measured byte back into the computer. We now have an 8*blt measurement of the voltage under test. We will call our result byte 1. To get a 12-bit reading, we must continue from where we left off An ^*OUT" to BAS+16 carrj^ing a byte of 0 is done, which changes Vj^j^j.^^^ to 128 millivolts. We are stilf connected to TBI pin 25 as before. Next, an "OUT" to BAS + 18 is done using the byte received during the 8- bit measurement (BYTE!) minus two counts. In other words, if the byte was a 100. we now OUT a 98, That causes the V|„_ to be 20 to 60 millivolts be- low^ the voltage receiv^ed from the terminal block. We are again ready to start the A/D converter using an OUT to BAS + 4. We read BAS + 8 until the A/D con- verter finishes its conversion and then read back the new val- ue (BYTE2). Since V^KFr^ Is presently equal to 128 milli- volts, BYTE 2 Is equal to the number of millivolts above V,^>4^- Vjj^_ is equal to (BYTEl-2) x (5/255). Therefore, the value of the voltage at pin 25 is equal to (BYTEl-2) X ((5/255) + BYrE2)L Power supplies Regulator IC21 makes use of the computers + l2-volt supply to produce the + 7 volts re- quired by IC7-1C9. Regulator 1C22 makes use of the comput- er's -hl2-volt supply to produce the -^-5 volts required by all of the other ICs. Regulator IC23 makes use of the computer's - 12-volt supply to produce the -5 volts required by 1C7, ICS, 1C9, IC13, ICi4. IC16, and ICI8- {BOTTOM VIEW) 1^ ^ r ' - ' * FIG. 3— T1003 PARTS-PLACEMENT DIAGRAM, You can either buy a PC board or make your own from the foil patterns we've provided. The Front End parts are shown with a dark line around them. FROKT-END Resistors R1— 33 ohms, IG-pin DIP resistor R2— 2200 ohms, 10-pin SIP resistor R3— 1000 ohms, lO-pin SIP nesistor GapaQitors Ct-C7— 0.15 \Lf, 50 volts, monolythicor polystyrene CS-C11, C20-C28— 1500 pF, 63 volfs. polystyrene C12-C19— 220 pR 100 volts» ceramic disc Semi conductors ICl— 74LS573D octal latch IC2— '74LS668D 8-bit magnitude com* paratof IC3— 74LS245D octal transceiver IC4— 74LS02D quad 2-input NOR gate IC5, IC5-K)ctal buffer IC7~74LS0SD quad 2Hnpul AND gal© Other components J1— 16-pin male header J2— 10-pin mate header J3^26-pin dual-row header with match- ing IDC connector, ribbon cable, and male IDC DB25 connector Miscellaneous: 17 shorting blocks (for J1 and J2) Note: The following items are avail- able from TSW Electronics Corp., 2756 N. University Dnve, Suite 168, Sunrise, FL 33322 (305) 748-3387: Construction To build the T1003 pe- ripheral, a PC board is recotn- mended. You can either buy a PC board from the source men* tioned in the Parts List or make PARTS LIST • irOOO kit— S65.00 • 11000 PC board only— S35,00 • 11000, assembled and tested— $77,00 • 6-foot interface cable (DB-25^)— $12.95 9 T1Q01 kit (Includes PC board, all listed parts, project cdse, and p re- assembled front and rear panels— $149.00 • T1001 PC board only— 549.00 • T1001, assembled— $179.00 • TIOOI software (included free with T1001 orderHSlO.OO • Capacitor kit (unmeasured) — $21.00 • Capacitor kit (measured to within 1%)— S26.00 • T1003 kit (includes PC board, all listed parts, project case, and p re- assembled front and rear panels— $159.00 • T1003 PC board only— $59.00 • T1003, assembled and tested — $189.00 • T1003 software (included free with T1003 orderHSlO.OO Add $5.00 S&H to any order Check or money order only. Florida residents must add 6% sales tax. your own from the foil patterns weVe provided. Note that the parts for the Front End are con- talned on the T1003 board shown with a dark line around them in the Parts-Placement di- FIG. 4^THE DB-25 CONNECTOR at- taches to the board with a length of rib- bon cable and a 26-pin header and matching connector. The LM340K reg- ulator mounts on the back panel of the T1003 case along with a heatsfnk. agram of Fig. 3. There is also a separate Parts List for the Front End. (The Front End circuitry was discussed in detail in the June issue.) Do not confuse the two lists of parts, or where the parts go on the board. Also, notice that there are three holes on the board for many of the capacitors* with two of them electrically the same. The holes can accommodate capacitors of different sizes. Use the pair of holes that best fits the capaci- tors til at are available to you. Four voltage regulators are in theTlOOS: 1C20-IC23. Three of PC BASED TEST BENCH coniinucd from preceding pnge them mount directly on the PC board, but one of them (IC22) is an LM340K in a 70-3 case that must be mounted on the back panel of the T1003 case. Mount the regulaton along with an ap- propriate heatslnk, on the back panel and hardwire it to the board. Figure 4 shows the com- pleted T1003 board. Software Each perlpheraL including the 1 1000. has its own software program lo control its own oper- ation. All of the programs end up in one directorv' as more pe- ripherals are added. Software for the 11000 and the entire se- ries of peripherals, including the T1003. can be downloaded all at once from the RE-BBS (516-293-2283. 1200/2400, 8N1) as a self-unarchiving zip file called I1000.EXE, Both com- piled and uncompited software Is included. Software is In- cluded free w^lth the purchase of any peripheral from the source in the Parts List- (Software can also he purchased from thai source without purchasing any hardware items ifyou have no way of downloading it from the RE-BBS.) The T1003 peripheral must be calibrated precisely if you ex- pect it to work properly You II need a DC voltmeter for elec- trical testing. The hand tools you 11 need Include a non-con- ductive alignment tool to set the potentiometers, a small flat- blade jewelers screwdriver, a 5K calibration potentiometer (in- cluded with the T1003). and a "U" shaped wire (also supplied g{ with the T1003). The main, or - "TSVF' menu allows you to select 1 "A/D, DfA, I/O/' That starts the T1003. Select "C ' from the next ^ menu to calibrate the T1003. J and carefully follow all of the in- g struct ions that you are given. I The T1003 will provide you I with a relatively simple method g for obtaining real-world data and getting it in to your PC, With practice you will be able to gen- erate your own custom applica- ^ tions for this project. B-E TROUBLE SHOOTING continued from pBgc 59 each of which has one or more connectors for cables that drop to individual workstations, !f a station drops off the networks the MAU takes on the respon- sibility of ensuring that the ring maintains electrical continuity throughout. Calculating maximum cable STP). and TVpe 9 (26 AWG STP). Unshielded IVpt 3 is not recom- mended for l'6-Nfbps operation. 1\pes 6 and 9 are more flexible, hence convenient, thanT^^pes 1 and 3, TVpes 1 and 3 are often used for the main ring* and Types 6 or 9 for runs from a wall plate to a PC or device. Type 1 was the first type offered, and is still most popular ARCnct: ARCnet uses a token-passing protocol, and It FILE SERVffl □i IDI JD □ □ □ FIG. 4 — ARCNET offers a hybrid star bus topology that runs on twisted-pair cabiing. Note that the middle cluster of PC's is wired as a bus, which is itself connected to a hub that services another PC and cluster in a star configuration. lengths is straightforward, but it ts a little bit more complicated than the simple maximums for 802,3. Token ring runs on several types of cable; common types include Type 1 (22 AWG STP). Type 2 (22 AWG STP plus four unshielded pairs for phone, e.g. RS-232], Type 3 (24 AWG UTP). Type 5 (fiber). Type 6 (26 AWG runs at 2.5 Mbps over RG-62 coax or UTR ARCnet has a flexi- ble topology configuration. In- cluding daisy chained coax (like thin Ethernet], coax star, and twisted pair star With proper network Interface cards, ARCnet also supports hybrid bus/star topologies, as shown in Fig. 4, Continued on page 71 Build this linear amplifier to boost the output of an amateur television transmitter from 2 to 10 watts mv Linear flmp I RUDOLF R GRAF and WILLIAM SHEETS THIS AliTlCLE l^hlSCKIIlKS THK Dl-l sign and construe lion of ah aui- pilfler I ha I can Increase the power outpul of the amateur television transmitter de- scribed in the June and July 19S9 issues of Radio-Elec- tronics. That transmitter had a nominal 2-watt peak output. However, with this linear ampli- fier, the transmitters output can be increased to 10 to 15 watts over the frequency range from 420 to 480 MHz, (The power output will be slightly less up to 500 MHz. and slightly mare below 420 MHz.) The am* pliOer should also be useful for amateur FM at 450 MHz as a power booster for 1- or 2-walt handheld portable trans- ceivers. provided that a suitable switching relay is added. Referringto the schematic in Fig. L the ampliiier has a single Motorola MRF654 RF power transistor (Ql) as the active ele- ment. RF input power is fed to Jl, lyhere CI, C2, and LI form an adjustable matching net- work to transform the low input impedance of QI (typically 3 ohms) to about 50 ohms, (LI and L3 are part of the I^C board etching, so you should not make changes in the design of the foil pattemj Base bias for Ql is fed through R2 and L2. Ferrite choke L4 supplies 13,2- volts DC to the collector of QL For optimum performance* Ql should have a low- impedance load, so C3, and C4 trans- form the nominal SO-ohm load (the coaxial line to the anlenna) to 2.6 ohms. Although Ql is designed for FM service, it can function as a linear amplifier if it is forward- biased with about 0.6-volt to an idling current (when no signal is present) of 50 to 100 m ill! am- peres. Good linearity is impor- tant, because it is handling an AM signal with video modula- tion. Also, the matching net- works should have adequate bandwidth (about 10 MHz} to avoid cutting the higher video frequencies. Poor linearity will show up as sync compression, sync buzz In audio, or video level clipping. Bias for Ql Is provided by di- ode Dl, Its important that Dl be thermally connected to Ql so that Ql and Dl are at nearly the same temperature to avoid ther- mal runaway. That is done by soldering one lead ofDl directly to the emitter lead of QL and keeping Dl in contact with the Ik S to m <& o 67 J1 1^-2.0 W^TS INPUT LT (PftBTOF PC BOARD) 01 lO'lSWUTSSOU 10pF 'SEE TEXT r R3 D1 1114007 R4 IK 115 m Re IK Rl 100Q + 47%F 1 C7 'f^ D2 1N4I107 + 13.2V 03 1N4007 Fia 1-UNEAR AMPLIFIER SCHEMATIC The amplifier has a single Motorola MflF654 RF power transistor (Ol) as tts active element PC board foil around Q!, Capac- Itors C5 and C6 provide broad- band bypassing of DL and L2 and R2 feed DC bias into the base of gi. Coll L2 is a low-Q broadband choke that prevents parasitic oscillation. Potentiometer Rl is adjusted so that, in the absence of an in- put signal to Jl, the amplifier draws about 125 milliamperes from a 13.2~volt DC supply. Ca- pacitors C7 and C8 perform broadband bypassing in the col- lector circuit, and D2 and D3 provide reverse-polarity protec- tion in the event of power-sup- ply spikes or accidental miscon- nection, A 3-amp fuse* not Included on the PC board, is de- sirable in the positive lead of the power supply Constructiaii The linear amplifier is con- structed on a G-10 0.062- Inch epoxy fiberglass double-sided PC board. Note that one side of the PC board is a ground plane with no components or traces on it. That is absolutely essen- tial to the operation of this cir- cuit. The PC board traces have capacitance and inductance that are Incorporated Into the design of the amplifier Induc- tors LI and L3 are two exam- ples, as are the mounting pads for CU C2, C3, and C4, which offer significant capacitance to ground. Therefore, it Is impor- tant that you do not modify the foil pattern provided. You can buy the PC board from the source given in the Parts List. Figure 2 is the parts-place- ment diagram. All components are mounted on the component side of the board and soldered to their respective pads with zero lead length , except as in the spe- cialized Instructions that fol- low. Refer to Fig. 3 for details concerning those specialized instructions, A number ol f^rounding wires must be passed through holes in the board and soldered on both sides to connect the top and bottom ground planes to- gether. All of those points are designated on the board with a "G/* A short length of excess component lead can be used. Wrap a length of ^/le-inch cop- per-foil tape around all four out- side edges of the PC board, fold It over, and then completely sol- der it on both sides. Variable capacitors CI and C4 must have their leads benl at 90'' angles and soldered flat against the board. However, In- sert the leads of variable capaci- tors C2 and C3 through holes In tlie board and solder them on each side* The leads of potenti- ometer Rl must also be bent at 90"" angles and soldered flat against the board. Bend the leads of electrolytics C6 and C8 at right angles so they are flush with their cases, and solder them to the PC board. Trim the leads as short as possible. Coll L2 is actually just one lead of R2 (a 6,8-ohm resistor) formed into a 2^2- turn induc- tor. Wrap the lead 2*A times around an '/H-inch thick nail or similar form. When soldering it to the board, make sure that you raise the coil part of the lead slightly above the board so that it doesn't touch the copper trace below it. IWo chip capacitors are used Vw irjCM COPPER RIBBON MFSSlfiG CORNER FIG. 2— PARTS-PLACEMENT DIAGRAM, surface of the tioard. At I components are mounted on the top FfG. 3— CONSTRUCTION DETAILS. Because of the high frequencies Involved, certain aspects of the design are very critical. In this project [C5 and C7). To install them properly, first tin the area where the chip is to be Installed, and then place the chip on the board. Hold the chip down with the tip of a small screwdriver and tack solder one side to the tinned surface. After one side is tacked in place, lack solder the other side. After both sides are tacked in place, per- manenlly solder both sides as shown in Fig. 3. Now install Ql. Note that a hole is drilled in the board for Ql . large enough so that no part of Ql s case touches the board. Look for the lead that's missing a cornen and position that lead as indicated in Fig, 2. There are two larger holes near each emit- ter lead of Ql, Thread a short length of copper foil, yie-inch wide (cut from foil tape) through those holes and solder it to both sides of the board after Ql is installed. The copper sol- idly grounds both emitter leads to the top and bottom ground planes (see Fig. 4). After Ql is soldered in place, mount Ihe PC board inside the case, as shown in Fig. 4. so that thebotlom ofQl is level with the outside surface of the case. Use a metal case for proper shield- ing. Mount Ihe board with the four corner mounting holes and 4-40 or 6-32 screws. Use wash- ers or available spacers that will allow the proper fit for Ql. Drill a hole in the heatsink for QTs 8-32 threaded stud, and deburr the hole so that the bottom of Ql mounts flush. Secure the heat- sink with an appropriate nut and lockwasher. ^ Make sure that Ql fits in its % mounting hole and that no part ^ of it, except for the four ribbon ^ leads, touches the PC board. There must be no mechanical ^ stress on QTs leads. If Ql is off- g center or cocked at an angle to 2. the PC board, the stud might | break off when the mounting o nut is tightened. The heatsink for Ql should be at least a '/le- or ^s-inch tdumi- num plate measuring about SV^ S9 PARTS LIST FIG, A — Qi IS INSTALLED so that no part of its case touches the hoard. Heatsinking is very Importafit FIG. 5— THE AUTHOR'S PROTOTYPE- A metaJ case provides superior shrelding. 5il I o Z c 9 70 rMPUTO-- 2.2pf WITH SCOPf 3 imUS OF #23 nr-K'iED WIRE 1 APR ED AF \ 1 URf\! FIG. 6— THE AMPLIFIER cart be monitored for linearity with this video-detector circuit and an oscilloscope. X 5 inches. The heatsink tem- perature should not exceed 140°F (60^0 during amplifier operation. If Ihe amplifier runs too warm, replace the heatsink with a larger one. A suitable heatsink is included with the kit available from the source All resistors are Vi-watt, 5%, un- less otherwise noted* R1— 100 ohms, potentiometer R2— 6-8 ohms R3-R6— 1000 ohms Capacitors C1-C4— 2-18 pF trimmer C5. C7^.001 fiR 60 volts, chip C6^10 jmF, 16 volts, electrolytic C8— 470 fiF 16 volts, electrolytic Semiconductors 1N4007 diode Q1--MRF654 transistor other components Lt , L3-"part of PCB etching 12— one lead of R2 wrapped 2V2 times around a ^/4}th-inch thick nail ^ggg text) L4— VK200-19-4B bead choke (Ferroxcube) J1, J2— BNC connector Miscellaneous: PC board, metal case, heatsink, hardware, 15 inches of copper-foil tape, coaxial cable, wire, solder, etc. Note: The following items are available from North Country Radio, RO. Box 53 Wykagyl Station, New Rochelle, NY 10804: » Linear amplifier kit (mcludes PC board, all parts, case, heat- sink, hardware, copper-foil tape, coaxial cablei and con- nectors}— $79.50 • Linear amplifier PC board only— S1 1.50 • ATV transmitter kit (includes all parts, case, 439.25-MHz crystal, and all connectors) — $125,00 • ATV transmitter PC board only— $12.50 • Additional crystals for the ATV transmitter (channels 14, 15, 16, 17, or 18}— $7.50 each Add $3.50 shipping and handling to any order. Mew York resi- dents must add appropriate sales tax. given in the Parts List. Connectors Jl and J2 can be BNC- or N-t}pc. Do not use type F connectors because the im- pedance is not satisfactor)^ at 400 to 500 MHz, Use a short length of miniature coaxial ca- ble to connect Jl and J2 to the PC board. Figure 5 shows the inside of the author s prototype. Alignment After carefully inspecting the board, setRl fully counterclock- 12I014VOC MV iTfWNSPifrTriH "TT I AUDIO IK \ Jl J2 LINEAR Ai.lP COAX RG. 7^THE TRANSMITTER connects to the linear amplifier with a short coaxial cable, and ihe antenna is connected to the amplifier draws about 1 ampere. Quickly adjust C3 and C4 for maximum RF oulpuL Now go back and ad- just CI and C2 for maximum RF output. Now readjust C3 and C4, Repeat that procedure until a maximum RF output is ob- tained. You should obtain 10 to 15 watts or more from J2, and the amplifier will draw about 1.5 to 2.2 amperes. Check to see if any part is overheating;. Now vary the drive to Jl : the RF out- put should smoothly follow the input, if it is correctly tuned. For amateur TV use, the am- plifier can be monitored for Hn- COMPONEMT SIDE for the linear amp, wise and connect a regulated 3- amp, 13,2-volt DC supply, ob- sending proper polarlly. An am- meter must be installed in series with the positive lead un- less the power supply has a built-in meter. Connect a suit* able wattmeter (0-25 watts J and a 50-ohm dummy load to J2, (Do not use an antenna, be- cause the circuit might radiate interference during tests J Make sure your wattmeter and load are both functional at 400-500 MHz (many CB and ham-radio meters are unsatisfactory at those frequencies K Do not yet connect anything to Jl, Adjust Rl so that the amplifier draws 100 to 125 mtlIiamperes(do this very quickly). Next, apply i^F drive of L5 to 2 watts to Jl and slowly tune CI and C2 until the amplifier earlty with a video detector on the output and an oscilloscope. Fig. 6 slaows a suitable detector for that purpose. Figure 7 shows how to con- nect the transmitter (from the June and July 1989 issues of Radio-Electronics) to the lin- ear amplifier. Tiie best perfor- mance is obtained by adjusting R33 in the transmitter so that initially there is an output of 3 to 5 watts from J2 with no video input. Check to see that the out* put varies smoothly with R3, Then adjust R32 and R33 for the best video performance without 5\Tic clipping or white clipping. Slight adjustments of Rl in the linear amplifier might be needed for optimum lin- earity Do not overdrive the am- plifien or s>tic clipping and de- graded video will occur, R-E TROUBLESHOOTING LAN'S con tinned from page 66 The chief attractions of ARCnet have always been low cost and ease of network expan- sion (to a limit of about 100 users). For example. ARCnet network interface cards from brand-name dealers cost about SI 50, half that of comparable thin Ethernet cards. In com- parison. 4-Mbps Token Ring cards from the same vendor cost about S400. Offshore- made ARCnet cards sell for un- der SIOO- Conclusions This whirlwind tour of net- work cabling, topologies, signal schemes, and access protocols will not make you a fuU-fiedged network wizard. But if you mas- ter the concepts presented here, everything else will fall into place easily. Next time well delve into what to do when these won- derful beasts don't do what they're supposed to do. See you then. B-E RESOURCES FolJowing are reference malerrals, equipment suppHers, and network- re- lated standards organfzalions. We es- pecially recommend The Black Box LAN CatBiog References^ • The PracUcal Guide to Local Area Networks, Rowland Archer Osborne- McGraw HilL Good introduction to cable types, topotogies. and access methods, • Networking IBM PCs, Michael Dure, Que Corporation. Chapter 14 contains good overview o( bridges, routers, and gateways. • LAN Magazine. 600 Harrison Street. San Francisco, CA 94107 (415) 905-2200. Suppliers: • Black BOK Corporation. P.O. Box 12800. Pitlsburgh^ PA 15241. (412) 746-5530. • JOB Microdevices. 2233 Samaritan Drive. San Jose. OA 95124. (800) 538-5000. m Cable Express Corporation. 500 East Brighton Avenue, Syracuse. NY 13210» (315) 476*3100. Stand&nlfi GrganixAtloiis: • American National Standards In- siiiute. 1430 Broadway, Mew York, ISA^ 10018, (2i2|. 642-4900. • IEEE Headquarif rs, 345 E. 47m Street. New VTork. NY 10017*2394, (212) 705-7900. HARDWARE HACKER Santa Claus machine BBS, FM antenna range contest, direct toner breakthrough, synchronous rectifier ideas, and the fundamentals of correlation. DDH LANCASTER i 72 A quickie update before we begin; We've found out that most of those popular FM wireless broadcaster circuits will no longer work because nearly all of the newer synthesized receivers positivefy demand exactly on-chan- nel frequencies. In recent columns, we've seen how that Pioneer CD- FM-1 can easily be modified into a fine crystal-controlled and high- quality FM stereo broadcaster At the time. I didn't neaily believe that a plain old third-overtone crys- tal could really get pulled that far and still provide a CD-quality result. So. I asked an outstanding VCXO de- signer by the name of Jim FitzSimons to do a circuit analysis for me. The bottom line: Yes. you can pull an ordinary third-overtone crystal far enough and linearly enough to do the job. But just barely. Sonrte other fallout from the VCXO analysis: The temperature- compensated 1.4-volt supply is quite critical for linearity, and you should not try and raise the voltage. And the varactor modulator does its work by shifting the series resonant point of the crystal. Do let me know if you need any further information on this. Now let us go on to some new stuff that involves... Electronic correlation This is one topic that can get real hairy fast, but let us try it anyhow Many fancy electnonic applications need correlation techniques of one sort or another A few of the zillions of possible examples include spread-spectrum communications , machine vision, radar. GPS naviga- tion, speech recognition, video compression, radio astronomy, planetary pnDbes, fuzzy logic con- cepts, pattern recognition, neuron computing, etc.-. Well correlation is simply looking for a match. A match against some original signal. Or any replica of that signal. Or against some expected pattern. And the longer you look for your match, the deeper the noise you can extract it from. With luck and a decent correlator, all your noise and interfering signals will cancel out or. at the least, pile up far more slowly As a general rule, if any electronic system has to push the limits of what can be done, comeia- tion often will end up playing a big role. A trivially simple ferinstance of correlation is the Morse Code. You Cor some machine) receive a pattern of short-long-short-short. You can then compare that pattern against a stored list of all of the acceptable characters and numbers. A begin- ner might note that it sounds like "li- no-le-um" and linoleum starts with an "L" With practice, you can do a near-immediate correlation, rather than having to go and compare each and every possible pattern. You sim- ply "hear'' the code as letters, in the same way a musician "sees" notes. But, inside your brain, a very elegant wetware correlation is coming down. Lets see how correlation can help push the detection limits of a simple problem. Say you have a very long driveway and want to know whenever anyone shows up. You put a bright LED on one post and a photocell on the other and build an ' electric eye/* And it works just fine at night. NEED HELP? Phone or write your Hardware Hacker questions directly to: Don Lancaster Synergetics Box 809 Thatcher, AZ 85552 (602) 428-4073 But when the sun comes up, the photocell saturates and nothing seems to work. You next try some obvious non-corretation cures to see if they help You raise the LED power, add a deep red filter and some focusing optics to improve your signal and reduce the noise. You amplify only those received sig- nal changes that are in the expected frequency range of a passing cat And you even use some sort of AGC loop to keep the sensed light in the linear detector range. Any of those stunts should work in a plain old driveway sensor but let's pretend that, after trying every- thing you could think of to improve your lineahty. noise rejection, and signal-to-noise ratio, that things still aren't quite reliable enough. Now what? Figure 1 shows you one of the oldest and simplest of the elec* tronic correlation techniques. It Is called a synchronous demodulBtor, and may still even go by its ancient name of a lock -in amplifier You chop your LED at an audio rate, turning it on and off at, maybe. TOGO times a second. You design a re- ceiver that amplifies only signals near tOQO Hertz, Now for the tricky part. Instead of just detecting your 1000 Hertz, you fate a copy of your original signal and route that to a specially crafted demodulator which follows the rule "amplify when I am positive, but am- plify and mverf when I am negative." Well neglecting any phase shifts or delays (they can be easily gotten around), your real received signal will always match your signal copy, and it should nicefy pile up. But any interfering signals will sometimes add and sometimes subtract. So, the interference cancels. At least some of it some of the time. By correlating, or looking for an exact match for an expected input signaL you have quite dramatically 1 kHz chopped light beai routed across driveway from LED to photodiodo Alarm output 1 kHz square wave generator i> L 1 kHz narrow band amplifier synchronous demodulator 1 kHz demod reference FIG. 1 — A "LOCK-IN AMPLIFIER/' or synch ronous demodulator is an older and sim- pler example of electronic correlation. In thts driveway detector, the desired "no cars'' signal can easily be extracted from sunlight or other interference. improved your ability to reject nearly all types of potential interference or conflicting signals. You can also view a synchronous demodulator as an extremely nar- rov^ bandpass filter that automat- ically and exactly tracks your input signal. Even if your input signal is varying. But synchronous demod- ulation goes one step further than a simple filter Note that signals of the wrong phase get more or less re- jected. For instance, any Interfering signal that happens to be at a phase angle of plus or minus 90 degrees gets comp/efeiy rejected. Other phase angles mtght only get par- tially rejected, but they will still be reduced. Go through the math, and you'll find that a synchronous demod- ulator offers a "free'* additional three decibels of signal-to-noise ratio improvement over the best de- tector you can come up with that does not use correlation. And three decibels at or near a digital detec- tion threshold can mean a big world of difference rn reliability From er- rors per second to errcrrs per hour. Building a correlator In general, you do a correlation by muitf plying and then by adding. You first find out how well a smaller piece of your received signal can match. You might assign a +1 for 'agree" and a ~1 for "disagree." Then you add up (or integrate) each individual agreement or disagree- ment to get some overall total. The summed total is called your correlation coefficient. If your final correlation coefficient ends up high enough, you vote "yes." Or else you simply pass the correlation vaf- ue on to more circuitry that wants to know relatively how well you hap- pened to do this time around. Correlation can be done by using analog, digital, or mixed signals. In the digital world, you can correlate in either a serial or parallel mode. Serial is slow and fow in cost, while parallel is fast and complex. But se- rial might not be nearly fast enough for many real-world uses. A special class of microprocessors we know as digital signal processors are ar- ranged to do many correlation tech- niques faster and easier than can the traditional personal computer CPU chips. Several simple correlator circuits are shown In Fig. 2. For linear cir- cuits, a diode bridge or any four- quadrant multiplier should work just fine. For high-frequency RF work, the Signetics NE605 is a great choice. But my favorite lower frequency linear synchronous demodulator is the gated gain amplifier of 2-a. If the mask signal is low, the gain is plus one. If it is high then the gain is minus one. This is a synchronous full-wave rectifier that does all of the multiplying for us. A following integration stage will do the addition for us. Often the addition can be done with nothing but a series re- sistor and storage capacitor. The fundamental digital correla- tion circuit is the compare gate, oth- erwise known as an exclusive nor, shown in Fig. 2-6. A compare gate gives you a one out if the inputs are identical and a zero out if they are different. For serial use, one com- pare gate can be followed by an up- down counter. For parallel use. bunches of compare gates are fol- lowed by a special pile of adders configured as a "how many ones are in this word?" circuit. Figure 2-c shows the details. Yes, you can go out and buy dig- ital correlator chips, but they do tend to be specialized and expen- sive. TRW and Stanford Telecomm are two big sources for these chips. A second more popular route is to use firmware and a digital signal pnD- cessing chip. On your own. you can easily and cheaply hack up an eight-bit digital correlator out of any plain-Jane 2764 EPROM, following the details from Fig. 2 d. Your truth table simply answers the question "How many bits match?" The answer will be a four-bit word ranging from -8 to + 8, For any sixteen-bit parallel digital correlator, simply precede a dif- ferent 2716 EPROM with four quad xoR gates. Or use a device such as a PLA or PLD. Correlation could also be done in software. For instance, in PostScnpt, just do an excfu$ive-or- not sequence, followed by a table lookup which converts a binary number to the numberof ones in the word. Fast and fun. NEW FROM DON LANCASTER HARDWARE HACKER STUFF Hardware Hacker RopHnts II or III 24.50 Midnight EnginewEng Reprints 16.50 Incredible Secret Money Machine 1S.50 CMOS Cookbook 24.50 TTU Cookbook 24.50 Active Fitter Cookbook Micro CQckbook vol I or 11 19.50 Lancaster Cla9$ics Lfbrdry 119.50 Apple Writer Cookbook 19.50 POSTSCRIPT STUFF Ask The Guru Repfinia I II or III 24h50 L a ser Wri te r Sec rets (^1 i/M bc/PC) 29.50 PostScrlpl Show & Tell 39.50 Intro to PostScript VHS Vtdeo 39.50 PostScript Beginner StuM 3§.50 Pe stSc ript Ceo kbook (Adobe) 1 5. 50 P- match bit out 1 - same 0 = different (B) Serial digital correlator uses an excluslve-NOR gate. sn mn r o- ( 0) Paral le I di g ilal co rral ato r uses gates and a special adder. - CK*- ■^"^ 2764 EEPROM - O-^ ^ ^ E CD O-*- E O-p- (D) 2764 EPROM made into a parallel B-m correlator. Fia 2— HERE ARE FOUR POPULAR METHODS for domg electronic correlations. Correlation functions An exact match against your ini- tial signal is called an auto- correlation. Attempting a match against anything else is a crosscor- relation. Should you try a match against some shifted ordelayed ver- sion of your initial signal, you are now performing a shifted auto- cornefation. Ideally your autocorrelations will always strongly agree, and most of your crosscorrelatJons will more or less cancel to zero. But those shift- ed autocorrelations get interesting in a very big hurry. For instance, say you now have a planetary probe flying past Nep- tune. The extension cord needed to deliver an exact copy of your auto- correlation signal tends to end up a tad on the long side. Not to mention asteroid breakage. The tdck. in- stead, is to take a local shifted auto- correlation sfgna! and move it around until you get a strong match to your incoming data. This is called acquiring a lock. Until you have your local clone reference precisely lock- ed to the incoming data, you can't receive any useful information. By far the most unique autocor- relation function occurs with the se- quence 1000. Like so... 0 0 41 -Hi -1-1 4 1 0 0 0 0 1 0 0 -1 -1 +1 4-1 —> 0 1 0 0 0 0 1 1 0 -1 -1 +1 ~> 0 1 0 0 0 0 0 0 1 "1 +1 +1 -1 —> 0 Here we are not adding. We are comparing two vertical bits at a time, and putting down a " + 1" if they are identical and a " - 1" if they NAMES AND NUMBEfiS Burr-Brown 6730 South Tucson Blvd Tucson. AZ 85706 (602) 746-1111 CIRCLE 301 ON fBBB INFORMAUOK CARD Consofidated Electronics 705 Watervfiel Avenue Dayton. OH 45420 (513) 252-5662 CmCLE 302 ON FREE IMFORMATION CARD Dr Dobb's Journal 411 Borei Avenue Suite 100 San Mateo, CA 94402 (416) 358 9500 CIRCLE 303 ON FREE IMFORMATION CARD Environmental Protection 225 North New Road Waco, TX 76710 (817) 776-9000 CIRCLE 304 ON FREE INFORMATION CARD GErtie 401 North Washington Street Rockville, MD 20850 (800) 638-9636 CIRCLE 305 ON FREE INFORMATION CARD Iterated Systems 5550A Peachtree Pkwy #650 Norcross, GA 30092 (404) 840-0310 CIRCLE 306 ON FREE INFORMATION CARD MCM EJeclronics 650 Congress Park Drive Centorviile, OH 45459 (513) 434-0031 CIRCLE 307 ON FREE INFORMATION CARD Pollution Equipment News 8650 Babcocl< Blvd Pillsburgh, PA 15237 (412) 364^5366 CIRCLE 30& ON FREE INFORMATION CARD Signetics/Philips 811 East Arques Avenue Sunnyvale, CA 94088 (800)227-^1817 CiRCLH 309 ON FREE INFORMATION CARD Stanford Telecom 2421 Mission College Blvd Santa Ciara. CA 95054 (408) 980-5604 CIRCLE 310 ON FREE INFORMATION Don Thompson 23072 Lake Center Dr #100 El Toro. CA 92630 (800) 457-5776 CIRCLE 311 ON FREE JNFORMATION C TRW Microelectronics Box 2472 La Jolla. CA 92038 (619) 475-1000 CIRCLE 312 ON FREE INFORMATION CARt>'^' IDQO tOOOlO 1000101 lOOlOtOt 100D0001011001 lOOOOIOOOt 001011 1000001001110101 100000010111001 FIG. 3— SHIFTED AUTOCORRELATION FUNCTIONS appear when you coirerate a digital word agamst a time-shjfted or bit^shifted repWcm oi itself. Those functions get rmportant in a hurry whenever you are trying to lock onto an incoming digital data stream. These examples am from GEnie PSRT download #427, are different. Only then do you add up the totai results. Note that the second, third, and fourth examples represent shifts of one, two, and three bits in your target word. Amazingly oil of the shifted autocor relation results are precisely zerol Very sadly this is the only known digital sequence that gives a "per- fect** shifted autocorrelation. The longer codes will do all sorts of weird things with the shifted sum- mations. Most of which can end up as less than useless. Some of the more interesting Cand more useful) shorter autocorrelation codes are shown in Fig. 3. There are far fewer autocorrela- tion functions than there are possi- ble bit combinations in any word. Why? Because shifted bit patterns, mirror patterns, and complemen- tary patterns will all end up generat- ing identical functions. The best possible autoconielation codes are called Barker Codes. Sadly, these are all short, and are few and far between. Instead, when you are using a long correlation code, you'll often have to settle for one that is simpJy "well behaved." rather than the best possible. On any longer digital codes, moat crosscorrelation values will be very low. For any code length, you could easily predict how badly a random interfering noise code might cfosscorreiate. Just use a messy piece of mathematics known as the bionomiai coefficients. For in- stance, on a feirly short code of 20 bits, only one cnosscorrelation will total to + 20 and one other to ~ 20. A mere twenty will sum to a value of + 18. Why twenty? Because there are only twenty possible places in a 20- bit word for the one bit ernDrs. How many possible errors of two bits? Go through the binomial math and the answer is a scant 190 cases that sum to + 16. Of the 1048576 possi- ble 20*bit cnDsscorrelations. a huge 772616 will sum to +4. -^2.0. -2, or - 4. Put another way. a tad over three quarters of all of those possi- Earn Your B.S. Degree In ELECTRONICS or COMPUTERS By Studying at Home Grantham College of Engineering, now in our 42nd year, is highly ex- perienced in '^d [stance education"— teaching by correspondence— through printed malcrials, computer materialSj fax, and phone. No commuting to class. Study at your own pace, while continuing on your present job. Learn from easy-lo- understand but complete and thorough lesson materials, with additional help from our instructors. Our Computer B,S. Degree Pro- gram includes courses in BASIC, P ASC A L and C languages — as well as Assembly Language, MS DOS, CADD, Robotics, and much more. Our Electronics B.S. Degree Pro- gram includes courses in SoIid'State Circuit Analysis and Design, Control Systems, Analog/ Digital Communica- tions, Microwave Engr, and much more. An important pari of being pre- pared 10 move up is holding the right college degree, and the absolutely neces- sary part is knowing your Held. 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, l-SO0^955-2527, or see mailing address below. Accredited by the Accrediting CDniinitsioii of the Nutioniil Home Study Council GRANTHAM College of Engineering Grantham College Road Slidell, LA 70460 1 75 1 +vout J fn a SYNCHRONOUS RECTIFIER, power switches are turned on only when conduction is desired. Because of the lower forward drop of a switched transistor, the efficiencies can be much higher than using ordinary silicon diodes in low voltage, high current supplies. In a CHIRP radar system, a frequency swept pulse is transmitted ttiat permits both high power (for long range) and narrow time resolution (for closer target separation.) A linear delay-versus-frequency correlator converts the received target swept phase histories back rnto actual viewable or recordable target maps. FIG, 4— AS THESE TWO WILDLY DIFFERENT EXAMPLES Show us, there is now an J n credible number of applicatfons for electron io correlation techniques. ble 20-bit interfering signals will be strongly attenuated by your cor- relator As you go to longer codes, the odds of noise interference be- come astronomically low. I've now posted a quick-and-dirty autocorrelation generator to CEnie PSRT as my file #435 AUTO- CORRPS. As is, it will generate atf of those unique autocorrelation codes up to 20 or so bits in fength. Yes, duplicate codes are discarded and not reported. And you can easi- ly extend the technique to quickly and accurately find autocorrelation functions as long as 65536 bits! It's written in PostScript, of course. The trick is to put all your ones and zeros into a string. Then play around with the string. That by- passes the precision limits of any conventional digital anthmetic. Sneaky, huh? We wilt be seeing much more on correlation in some future columns. Especiafly if we do get into more on spread-spectrum communications and GPS navigation. I just wanted to give a bare bones intro to a tricky topic here. Those shifted autocor- relation functions are lots of fun to play with (and a winning school pa- per topic) just because they are there. Let's wrap this up by looking at two wildly different examples of an electronic correlation in Rg. 4 — one simple, one elaborate. Say you want to build up a low- voltage, high -current power supply, maybe 5 volts and 100 amps. If you try using plain old silicon diodes for your outputs, you'll get a volt or two of forward drop across your diodes. And lots of waste heat and terrible efficiency. While the newer Schottky diodes help some, even those are very inefficient at higher curnents. But a propeHy chosen and driven power transistor could have a much lower forward dn3p than a diode. So. instead of using diodes, use field- effect transistors as switches set up as synchronous rectifiers. You turn your transistor on only when you desire conduction and turn it off otherwise. The forward drop can be much lower and the efficiencies much higher The synchronous rectifier is most likely to be your least elegant cor- relator example. Solar energy con- verters are another area in which high rectification efficiencies are super important. Shortly after World War II, pulse radar systems hit their limits. The resolution of a traditional pulse radar is inversely proportional to its pulse width; the range is propor- tional to the energy inside the pulse area, tdeallyp you want a super powerful yet ultra- narrow pulse waveform. The trick is to conjure up some method of sending a long putse that still gives you acceptable resolution. And the solution was called chirp. By sending a long linearly swept FM pulse out and then by routing the received swept waveforms through a linear delay vs. frequency network (a fancier example of a correlator), the individual bits and pieces of that swept waveform would pile up and generate a narrow target pulse. The exotic coherent radar sys- tems even went one step further especially those that were side- looking. The swept transmitted chirp pulses were suitably record- edy generating what were known as target phase histories. Those phase histories were converted into view- able data by using linear detay-vs- frequency networks, optics that made a Fourier Trans formatior}, ho- lography techniques, or electronic digital correlators. Alt of those tech- niques perform a comelation in one way or another. Chirp may sound really compiex and hairy. But bats have done it for eons. Compactly and elegantly in wetware. And the bats "figure of ment" for their radar beats out our best and newest military radars by some ten orders of magnitude. That s 10,000,000.000:1. And not half bad for amateurs! But. in all fainness, they did have a head start. Prtnted-oircuit ypdate From time to time in the past, we have looked at the new direct-toner method for making printed circuit boards. The new direct- toner meth- od promises to revolutionize hacker PC boards, doing the job in minutes for pennies with zero darkroom work or other special techniques. The two key secrets to the direct- toner method are that laser-printer toner does make an outstanding etch resist, and that the great PostScript computer language makes printed circuit layout excep- tionally fast, fun, and easy to do. From any computer, using nothing but your favorite word processor One early transfer film sheet was the TEC' 2 00 film from MeadowLake. Sadly many hackers swore at this new product, rather than by it. Even though many of the partial-transfer problems were caused by improperly cleaned boards, not doing a pre-etch or pre- heat, by using any old copier (in- stead of an SX laser printer), and trying to use an iron (instead of a Kroy Kolor machine or suitable heat press of some sort). As we saw last month, a very much improved trans- fer film Is now offered by Technics Inc as its PCBF-1000, Both of those products suffer a common flaw: They both expect a differential transfer to take place neliabiy in the real world. You first ask all of your toner to stick loosely to the transfer film. Later, you ex- pect all of your toner to adhere strongly to the board, leaving zero residue on the film. The differential transfer problem has been solved in spades by a brand new Toner Transfer System offered by DynaArt Designs and available from AH Electronics and DC Electronics, The system is basically a polyester film coated with some high-tech sugar water. There are two different ways to use the film, called the cold method and the hot method. Both methods open all sorts of new hacker oppor- tunities. The hot method is best for hacker circuit boards. With the hot method, you wifl laser print a backwards but positive image by using an SX printer with a good grade of graph- ics refill toner. As with the previous films, you then iron the toner onto a super-clean bare printed circuit board. You now have toner that is very tightly stuck to both the PC board and the film. Soak your board in warm water for a few minutes, and all the high- tech sugar water dissolves, floating away the backing sheet. And leaving pretty near all of the toner on your circuit board nearly all of the time. Gently wash the board in warm water to remove any residue. Then etch as usual. The cold method is best for cir- cuit-board component-callout over- lays, dial plates, and ordinary decals. Print the normal and positive image to the film. Then spray the image using several light coats of a clear lacquer, urethane, or epoxy. Cut out all your images slightly over- sized and soak them in warm water. Then transfer the images just as you would any model-railroad decaL You can either remove the lacquer with alcohol to get at the bare toner, or add additional and more protecting clear sprays for extra durability. Those cold method results look especially impressive when you use a Canon color copier. Note that you can now transfer toner onto anything. The cost of the introducto- BIG PROFITS IN i VIDEO REPAIR!; Work kuuai K(XME>Earn SH5 URl With the lens Qi mtllions of VCRs and Camci^orders In use, there currenlly h a seriou s sh ortaga o1 trained techs to porform cleaning onri repair jobs on ttioso popular dcwlte; Learn how you can start your ^ ovvn highly profitable, Hfime^Pas^Ht video servicing And since up to 95% of all VCR and Camcorder malfunctions ^ are due to a simple USechanfCfTl or efectro- Cnechanic^i! failure!, you need not spend months or even years 0^ GompFicaled study before starling pMt professional sorvice work! Let Vj'ejo's Training Program show you howl 1-800-537-0589 ' ^ ' o r 111 ;i 1 1 C(i M p m tod ay 1 Vli:jC) PUBLICATIONS, INC I 4470-107 Sunset Blvd.. Suite fi^X) I IX'pE. VK Los Angeles. CA ^0027 ((tlieck appropriate Ixi^ ) J VCR R*piifr I J Cain«»rdcr Rf pair ■ j Advanccii VCSt Repair I J Fax MachiiK Rcpir I Name Address I Citv/Sijte. Zip L. J CIRCLE 1« ON FREE INFORMATION CARD Your Ticket To ! SUCCESS Over 28h0O0 technjcians have gained admit* tance worldwide as certified professionals. Let your ticket start opening doors for you. ISCET offers Journeyman certification in Consumer Electronics, Industrial, Medical, Commuriications, Radar, Computer and Video. For more Information, contact the Internationa) Socisty of Certified Electro- nics TechniciansH 2708 West 8arry Street. Fort Worth, TX 76109; (817) 921-9101. Name^^ 1^ k IB Addross_ City State .Zip. _Send material about JSCET and becoming certifiedn Send one "Study Guide for the l77 Associate Level GET Test." En- [ closed is SIO (inc. postage). R-E Engineering Adnfiart MIDI PROJECTS MIDI interfacing enables any so equipped instruments, regardless of the nnan- ufadurer. to be easily connected together and used as a system with easy computer control of these music systems. Combine a computer and some MIDI instruments and yoj can have what is virtually a programmable orchestra. To order your copy send $6.95 plus S2.50 for shipping in the U.S. to llictronic Technofogy Today Inc, RO. Box 240, Massapequa Park, NY 11762-0240. Rates: Ads are 2>'i"x2vr. One insertion each. Six insertcons S950 each. Twelve insertions S925 each, GEosing date same as regular rate card. Send order with remittance to Engineermg Admart, Radio^Eieclranics Magazine, 500-8 8i^County Blvd.. Farmingdale, NY 11735. Direct telephone inquiries to Arline Fishman, area code-1-516-293-3Q00, FAX 1-516-2S3-3115. Only WQ% Enginmm Btis are accepted for this Admart. WUNK SA YS D£VEtOPMEfjV TOOLS QUALITY a^nd SERVICE "Ctiip" experts agree with Dr. Munk. TECI's PC based microcontroller devcl* (ipnient tovls are the must oust eJTectivc for vctcr^ins or beginners, \W\\M I-'OR JU'lCiLSStatN^ S\9$£0 rj*H5;w(M(.(lf '6SHCll CHOVS ASSKM HIRERS. .... SM^ wthHiiffl? sr\m-\TOH i' nt^^iKiGFjLs s99Jon hHiH -tnS f^nas&S PRlMiKAMMKKS FROM $J?5.00 t.<).Mri,tn^K K' &.ASED my. sx^ms reoM ^^00 ftxircwvwarcii Rtm. tlmk F^tn.^TORs from Sieawi TECJi CALL TOLL FRKK 1-800-336-8321 rtic Engineers Collaborative, Inc. Kf n^ Box 8C, Bartun, V r 05822 USA TFL:(802»525-545S rAX:rK02)525-.U51 CIRCLE 18? OH FREE INFORMATiON CARD FCC LICENSE PREPARATION The FCC has revised and updated the commefcial license exam. The NEW EXAM covers updated marine and aviation rules and regulations, transistor and digital drcultry, THE GENERAL RAD lOTEl^ PHONE OPERATOR UCENSE - STUDY GUIDE contains vftal Information. VIDEO SEMINAR KFTS ARE NOW AVAILABLE. WPT PUBLICATIONS 7015 N.E. 61st Ava Vancouver. WA 98661 Phone (206) 750-9933 Dept. 50 CIRCLE 133 ON FREE INFORMATION CARD ry kit with five sheets is $9.95. For the first of our two contests this month, just show me something new, different, or off- 1 he-wait that you can do using either the hot or cold method of the DynaArt transfer s UJ 78 TONER RESOURCES All Electronics RO, Box 567 Van Nuys. OA 91408 (818) 904-0524 CIRCLE 323 ON FREE INFORMATION CARD Black Lightning Riddle Pond Road West Topsham. VT 05086 (800) BUCK99 CIRCLE 313 ON FREE INFORMATION CARD DC Efectronlcs RO. Box 3203 Scottsdale. AZ 85271 (602) 945-7736 CIRCLE 324 ON FREE INFORMATION CARD DynaArt Designs 3535 Stillmeadow Lane Lancaster. OA 93536 (805) 943-4746 ORCLE 314 ON FREE INFORMATION CARD The Flash Riddle Pond Road West Topsham, VT 05086 {800) BLACK99 CIRCLE 31S ON FREE INFORMATION CARD Kepro 630 Axminister Drive Fenton, MO 63026 (800) 325-3878 CIRCLE 316 ON FREE JNFORMATION CARD Lazer Products 12741 E Caley Ave #130 Englewood, CO 80155 (80O) 843-5277 CIRCLE 317 ON FREE INFORMATION CARD Meadowlake Box 497 Norlhport, NY 11768 (516) 757-3385 CIRCLE 318 ON FREE INFORMATION CARD Midnight Engineering 111 E Drake Road Ste 7041 Ft Collins, CO 80525 (303) 491-9092 CIRCLE 319 ON FREE INFORMATION CARD Recharger 101 Granite Street Ste F Corona. CA 91719 (714) 371-8288 CiaCLE 320 ON FREE INFORMATION CARD Supplies Unlimited 101 Granite Street Ste F Corona. CA 91719 (714) 371-8288 CtRCLE 3Z1 ON FREE INFORMATION CARD Techniks, Inc 45 J, Ringo Road Ringoes. NJ 08551 CIRCLE 322 ON FREE INFORMATION CARD system. As this month s resource sidebar. I ha/e gathered together a few of the better known direct-toner re- sources. Besides the three films we just looked at, Kepro is your leading source of hacker printed circuit sup- plies. More on the direct-toner method is likely to appear in The Flash or in Midnight Engineering magazines. My two very favorite toner sources remain Lazer Prod- ucts and Black Lightning, while others advertise in the Recharger and Supplies Unlimited magazines, I've recently posted my share- ware PostScript printed circuitry layout package over to CEnie PSRT as our file #401 PRNCRCIGPS, Pius a new summary tutorial on the new hacker printed circuit tech* ntques as file #419 NUTS3.PS. There will be bunches of exciting new stuff on toner in general as #435 TONERTRX.PS, A secand contest Our big-time name-brand cable company here in the Gila Valley has stupidly discontinued all of its FM bnaadcast sen/ices. And it's tn an area where any decent and useful FM stations are extremely hard to pull in otherwise. What really saddens me is that the reception on top of the mountain in my front yard is exceptional. Take ELECTRONIC COMPONENTS Whether you order 1 part or alt 38,g04...MOUSER stocks and...can ship today!! CALL... (800) 982-994a foryoyr ; ELECTRONICS SalM & Stdeklnfl LMitlont KeUonwldA any old $4 receiver up the moun- tafn, and a Tucson FM station comes in loud and clear Tilt the an- tenna slightly, and the Ei Paso sta- tion on the same channel frequency booms in. again loud and clear The same goes for Phoenix and Albu- querque at 933. So. I guess this month's contest is in that "Don*t get mad.,, get even" category. Just tell me all about any favorite tricks, circuits, antennas, or other products you know of which really work for relia- ble long-range FM reception. With both contests, there will be the usual dozen or so newly revised Incredible Secret Money Machine II book prizes, plus an aiUexpense- paid (FOB Thatcher. AZ) tinaja quest fov two going to the very best. As usual, send your written en- tries directly to me per that Need Help? box, rather than to Radio- Electronics editorial New tech lit Two reliable sources for foreign semiconductor replacements are MCM Electronics and Consolidated Electronics. Both send free cata- logs. A free video on laser-printer re- pair training is now available from Don Thompson. Don is regarded as having the finest training services rn this field, and stocks hard-to-find re- placement parts. Two environmental trade journals are Environmental Protection and Pollution Equipment News. The lat- ter has plenty of ads for interesting and unusual sensors. For lots more information on San- ta Claus Machines, check out the brand new stereoltthography user's group on GEnie UNIX. And a good tutorial on wavelets has appeared on page 1 6 of Dr Dobbs Journal for April 1992. Two free software sources for this month: Iterated Systems has a free demo diskette on its new real time fractal decompression soft- wane. And Burr-Brown now has a new freebie Active Filter Design disk available. If you are interested in active fil- ters, be sure to check out my clas- sic Active Filter Cookbook. It's available by itself or as part of my Lancaster Classics Library, as per my nearby Synergetics ad. R-E SURFMAN conUnucd from page 36 leads with your fingers or all you'll hear is hum. Listen to the noise produced; it should be loud and smooth- 11' its not, try another transistor IT you find a transistor that produces good qualiU^ noise, but the volume is not loud enough, the gain of the preamp stage IC2-a can be in- creased by decreasing the value of R12. But don't go below lOK. Drill holes for the volume con- trol and earphone jack in the front panel of the case (notice that the circuit board is notched to allow space for these parts) and mount them. Install the circuit board as shown in Fig. 3. No hardware mounts the circuit board directly; Instead, the two large mounting holes in the corners of the board fit over the mounting posts in the case so that when the top is installed it holds the circuit board in place. Using SurfMan Ti-immer R17 controls rain/ surf/pink noise selection. By setting R17 fully clockwise, you turn the filters off and obtain white noise (rain). When R17 is fully counterclockwise, the fil- ters are fully on for pink noise. At intermediate settings, the fil- lers wiil be modulated by the chaotic voltage generators for various surf sounds. If you want to connect Surf- Man to your hi-fi setup, the sim- ple capacitively coupled voltage divider shown in Fig. 4 wiil iso- late and attenuate the signal so that it can be plugged into an auxiliary input of your ampli- fier A *'Y" connector can be used as sliown to drive both stereo inputs. If you Ye really adven- turesome, build two SurMans for stereo. A word of caution: SurfMan really blocks outside noise and puts you in a kind of sound clos- et. Nothing short of a Scud at- tack will attract your attention. Don't use it while you re sup- posed to be baby-sitting the kids. Don't use it while jogging down the boulevard, and please don't use it while driving. R-E CIRCLE 1 17 ON FREE INFORMATION CARD ADVANCE YOUR ELECTRONIC INTERESTS WTTH A NEW SUBSCRIPTION TO: THE SPEC-COM JOURNAL! Getting your FCC Amateur Ftadio U- censa is easier than ever before (NO-CODE requirement - see R;E. April 91 issue, pages 27^28). SCj is an 80-page per Issue HAM RADIO magazine that covers ALL the spe- cialized modes. Modes like HAM-TV. Radioteletype, Satellites, WXFAX and Computer Data Transmissions. Current issue * just $3.75 ppd. Annual Subscriptions (6 issues): $20 USA $25 Canada/Mexico $30 Foreign (Surface) The SPEC-COM Journal P.O. Box 1002, Dubuque, !A 52004-1002 (319) 557-8791 BBS (319) 582-3235 COMPUTER CONNECTIONS A User Manifesto JEFF HOLTZMAN ■ get excited when a new tool comes along that provides nne with a better way of doing my work, f am disappointed when the tool lets me down. In the software industry these days, there is a lot of excitement: there is also a lot of disappointment. In analyzing the causes of this dis- appointment, I came up with the Software User Manifesto (SUM) shown in the sidebar It includes ev* erything I could think of, but it un- doubtedly misses some things. If you think of additions, send them to me c/o the magazine; we'll publish an update later For this project. I'm looking for general rufes. not com- plaints about specific products. The purpose of the SUM is as follows: If you have ever been or ane now disappointed by a software product, make two photocopies of the SUM. Send one to the CEO and the other to the marketing depart- ment of the vendor of the offending pHDduct, along with a cover note ex- pressing your displeasure. Add a specific exptanation of the circum- stances that raised your blood pres- sure. Then put your money where your mouth is. Windows prinJiict watch In all the hoopla surrounding the release of Windows 3.1 . it's easy to lose sight of the fact that Microsoft has also released significant up- dates to numerous products, includ- ing Excel. Project, Visual BASIC, and the C compiler. The Excel up- grade is particularly significant, be- cause new features typically appear there first and subsequently mi- grate to other products. There ane far too many new and improved features to cover here. Among the most interesting are the user-interface improvements, in- cluding fully customizable toolbars, right-button mouse usage, drag- and-dnDp table building, auto-fill, and automatic table fomnatting. Toolbars have become requined on most serious Windows prod- ucts: Excel pushes the concept in new ways. Typically a tool bar adds a row of "'buttons " somwhere near the top of the screen. You click a button to execute a built-in com- mand or custom macro. Most prod- ucts allow you to add and delete buttons, change the icon associ- ated with a button, or change the associated command or macrc). Ex- cel 4.0 does all that and quite a bit more. It comes with seven toolbars covering common functions such as formatting, charting, cfBating, and debugging macros: you can create your own at wilL A toolbar can float over the cunnent document, or dock along a screen edge. Now the right button works con- sistently throughout the program. Select an object (cell, range, chart, graphic), press the right button, and up pops a menu of actions appropri- ate to that object. Typically you1l see cut. copy, and paste, format changes such as font, colon and border. Drag-and-drop allows you to se- lect a rectangular range, then drag it with the mouse to a new location. Often this is much more convenient than the old method of cutting to the clipboard, going to a new location, LEIc tiltl FfiimtilB Forms) Qals Q0ani M^cis .^nilow tielp 1 — r A 'Ell C ! D I E ' F O ! M ! I J |g^K^ila..j M N ' Q 1 T ^ I ■ I 3 I&TTfg. lii ...i ... , ... , ■ i_J 1 L_L_L 6D0 m m lUUMiM m ^l:ilIJ'LESJ£ja±a±)[MM RG, 1 — EXCEL 4.0 gives new meaning to the phrase user4riendly. Multiple customiza- ble toolbars let you set up for the way you work; automatic table generating, format- tin9, and charting features make fast work of common operations; powerful macro tools simplify devetopment of custom functions and operations* Software User Manffesto Dear : I am a user of personal computer software, and 1 am dissatisfied. The foHowing statements express my needs. If you do not pay attention to my needs. I wiN not pay attention to your product Product Functionality The tool should extend the range of tasks that I currently perform, while providing a smooth transition into new user fealures. The tool must not be underpowered: I want as- surance that 1 can use all (he latest and greatest features — when Vm ready But I don't want them to get in the way until I am ready Integration Wrth Other Tools I want your tool to integrate smooth- ly with the others in my toolbox, and I want your tool to work like my other tools. I want ptug*and-play functionality. If I break a W sockel wrench. I can go to any hardware store and get a re- placement. I want the equivalent With software. Include a mini graph- ics editor with your word processor, but tet me substitute my full-fledged editor seamlessly. I want your tool to share data easily, and to read the various files in the various formats I've collected over the years reliably. I want to be able lo automate your tool and make it work with my other tools. I want your tool lo overlap the func- tionality of my oiner tools so I can get by with just it in an emergency. But I don't want to be penalized for using more capable tools when it is necessary. Inner Workings I don't care what's under the hood. I don't care whether it's object-ori* enled or structured; I don't care whether it's written in COBOL or C + + . Go ahead and use whatever you think is best. If you make a mis- take, you lose. But don't try to con- fuse me with technology. All I want is a solution- Customization And Automation 1 want to be able to customize your tool, even in trivial ways like chang- ing colors or icons, just to prove who's master — me, not it. I want you to leave room in your menus and toolbars for two, three or four of my most important Items so I can automate my most important tasks without drowning in macro languages or complex cus- tomization procedures. User Interface I want your tool to faithfully mimic the real world, and where that's not possible, lo extend current meta- phors in non-arbitrary ways con- sistent with mainstream directions. Don^t create whole new interfaces built around small incremental im- provements in limited areas. Let en- gineers design the engines; let writers, graphic designers, and users create the interfaces. Product Support Give me a built-in, on-line tutorial, with beginning and advanced lessons, for every facet of your tool. Provide context-sensitive help for every dialog box and screen item. Give me all reference information on-line and on paper. 1 need de- tailed, integrated, hyper-linked on- Ime reference information when I'm under deadline pressure, I want de- cent paper documentation when fve time to browse (e,g,. for toilet- side or air-travel reading). For paper documents, provide con- cise» comprehensive, welt-orga- nized manuals, not six or eight separately, bound booklets with no obvious relations between them. Put as much effort into designing the document as the product— it is part of the product. Use spiral or loose-leaf binding. Provide quick- fBference charts and keyljoard tem- plates, including blanks for creating my own manuals. Product Updates And Upgrades Provide regular upgrades and easy access to updates. I'd rather wait for bug-free code than waste time on buggy early releases. Post bug fixes and driver updates on Com- puServe or some other accessible public forum. Product Performance Both maximize speed and minimize storage. If you must choose, go for speed. Storage continues to get cheaper, but God has shown little willingness to give us more time. Product Installation Provide simpfe installation and complete un-installation routines. For the latter, remove every file and every setting in every system file. Provide separate initialization files. Don't muck around with system files. Don't require your tool to be on the path: keep all its setup files in its startup directory. Don't put any files in the root directory. Use the main product directory as the root for all support files. Document every file included with your product, and minimize the number of them. Provide a list of files required for a minimal installa- tion, and a setup procedure to quickly clone a minimal Installation from an existing one (for last-minute traveling). Run your installation routine in the backgrounds letting me accomplish something in the meantime. Network Support Don't store customization files in a common network directory Better yet, store organizational level customization files on the network, and user-spedfic overrides locally. In General Make designers listen to me, not to the engineers building my tool. If your management doesn't support that philosophy kiss your company goodbye. Provide smooth transitions, 1 will probably never accept drastic changes to totally new vi/ays of doing things. Evolve me gradually. Apply this to both hardware and software. Signed A (satisfied) (disgruntled) (former) user and pasting. Auto-fill is special. Type "Janu- ary" into a cell, drag the lower right corner of the cell across eleven ad- jacent columns, and Excel fills in the remarning months for you. It can do the same with other labels and arith- metic series. Automatic table formatting allows you to select a range, choose a menu item, and automattcally for- mat the range in one of several at- tractive pre-defined styles. Al- though the style-selection dialog box altows you to preview styles, you cannot modify them or add your own. There s also lots more horse- power under the hood, including workbooks that allow you to save several spreadsheets in one file, spelling checker, better printing ca- pabilities, voice annotation (if you have a sound card), rotated text, and text centered over multiple col- umns. Many new analysis features Continued on page 86 3610 $20.95 Home Reinote-CDnirol & Aulomation Projects FEATURING 77 STEP-BY-STEP ILLUSTRATED PROJECTS Sec ond Edition 3765 529.95 ROBOT BUfLOEU'S BONANZA OS INEXPENSIVf ItOBQTid PROJECTS Basic Electro ntc« C course 2ei3P $17.09 OSCILLOSCOPES ANTINNA 1 Tin: I ILLUSTRATED 1 DICTIONARY I ELECTRONICS FIFTH iOmOW 334Sf £2GiJ&S OSCILLOSCOPE 2aQ4P $19.9$ Softoovvf 3627P »19.dS 95 Select any 5 books J°|y when you join the Electronics Book Club'*' (values up to $172.75) I'niitL'tl <:irt:ttlt -VlicnxompuiiT* ELEaRONlC POWER AUDIO EQUIPMENT 2e67P $18. 95 Softcover PRIhTED CIRCU1T5 DESIQh SoflOdvef Sotteover CIROUltS VOLUME OH E MICROWAVE Oy^i Repair Troubleshooting Rgfi a Repairing i Sf COND £DltiON '^H!^ 3632 $18.95 Courits iS 3 Sod server ma S2«JS so«don Mccomb 3777 S32.95 Counts as 2 As a member of the Electronics Book Club . . . . . . you'd enjoy receiving Club bulletins evefy 3-4 weeks containing exerting otfera on the latest books in the field at savings of up to 50% off of regular publishers' prices. If you want the Main Sefectton do nothing and it wWl be ship- ped automatically. II you want another book, or no book at all. simpiy return the RepJy Form to us by the date specified. You'll have at least 10 days to decide. Your only obligation is to purchase 3 more books during the next t2 months, after which you may cancel your membership at any time (Put*^ieni' Pncss ^ha^m} boots ara hardcDAr unieiS dtwnvtH notwd. CilOrgS ESC ^ELECTRONICS iBOOK CLUB 6lu6 Ridge SumrtHt. PA 17294-OBlO O YESt ReasQ accept my membet^ip in th6 Electn?nlca Book Club and the 5 volumes tist^ t>e1ow fof just $4j95 plu^ S4B0 shippmg/han^ljrig saEes tajc. If not satisfied, t may net urn the books wilhirt ten days for a full rdurvd and hsve my memberaftip cancelled. I agrw to pufchaso at least 3 books at regular Club prices during the nejcl 12 monttis and may resign anytime I hereafter. A shipping/handling charge and sale^ tax will be added to sH orders. Hole: Af^y 'Ccisnts as 2 at 3' tttia may be choson imtond of ^ or 3 Sifrtflte sei^tionSr □ Check or money order enclosed payable to; McGrsw-HUI, Inc. Q Pleaao charge my □ VISA G MasterCard O American Expresss ACCtn #. Exp. Date _ Signature Name Address Ptione. Crty/State/Sp VsM lot nm* iTiflmtwr* ofi.1y, sybjed lo *Mftpla*w5fl W EDC U S. cxtkirB 05^ shipped Mi] Oass Sook Posi . Canada auisi remit jn U.S runds. Applin^anEs Quisifit^tha and Canfidft wit! Tscoiw special ordarlnff inslrtjclicrti. 'CnnsKfian otibitn j aro stijppod rntflrriaiignisi Book Pqsj— ij4tJ ii0.t3 shippino/handlino'. i Your most complete and comprehensive source for the finest electronics books COMPUTER CONNECTIONS continued frvm pBge 8! for science and engineering, im- pnDved graphing, and quite a bit more are included as well. Industry leadership Microsoft shows true leadership with Excel 4.0: I look forward to seeing these improvements in other products, parlicuiariy Word for Win- dows. The gripers who complain about Microsoft's domination of the industry should understand that the company is doing so not by legal wrangling but by p^ing increased attention to user needs and deliver- ing quality pnDducts to meet those needs. In fact, Microsoft's domtnatJon appears likely to increase even more. We are headed toward the day when the word computer doesn't r^fer just to hardware, but to a complete solution that includes both hardwarB and software- And Microsoft is gearing up to provide a complete software solution, every- thing frcim operating system (DOS, Wrndows, NT) to word processing, spreadsheet, database (to be re- leased this year). E-mail (likewise), and morB. When you buy a car you don t just buy an engine, you buy a solution for the pnoblem of traveling. Sure, the engine is important, but for most people, even more important are the seats, the console, and the body style. Microsoft already dominates engines and is in the process of mastering the rest. When you buy a car. you don't buy the engine here, the transmis- sion there, the body elsewhere: You buy a complete solution. Computer buyers have never had that luxury. Soon, though, you'll be able to buy a single CD-ROM with a complete suite of applications under your fin- gers. You won*t think of them as separate applications, they'll work T n I z S c 2 UJ GREAT MONEY IN VCR REPAIR Start your own highly profiiahle cash bastrtess from your home $ Earn up to $1,000 Per week Proven Turnkey Operation: Your own business in loss than 30 days. # Big Money Making Opportunity ^ Millions of VCR's are sold each year. "Diere is 0 serious shortage of tr«iined VCR technicians. Learn to service and repair the most popular applrance in Amenca. No complicated electronics. No expensive instruments- No fancy workshop t-£ARN VCm REPAIR w)ih easy mtep-ty- step video mslnjction Video training allows you lo team faster with tr tetmniion □VCR fl*|»ir Techfilctpn J ElKtmnlc Stcmitv Technician CALL TOLL FBE£l 24 HRS • 7 DAYS 1 -800-aS4-7761 , ext, VI 4 or write to: SJD VIDEO LfARNING CENTER 22700 CrcnsKftw BoulevDrd. SuWa 203 Tofrancs, CA 90505 CIRCLE 196 ON FH EE INFORMATION CARD Tlie Hardest Part Of GivingA Bond Is Choosing The Right Size. I mill h^^Wsm - I .S. Sj\ing& lk>n th Diiikc t jx^rfcit ft tor u 1 1 iKtasitihs. lliL-y earn inlcri.*^! lor up to ^ J(J yi'iiri - giiaraiikTd, tiive thc jiifi i lh;)l fiK ivcnoiic. \ VS. \ii\ in^\ EUmdJ Call 1 8(114 is HONE) Ui Ond inti morcj i US. Savmgs Bonds i Making .Anieriran I )minis A R\rdll\\ ] ,\ piihiiL HTvit^v (t( t]ii% tiut^4/iar j together as if they were made to. Microsoft will be the General Motors of the Information Age: Borfand will be Ford; some com- bination of Novefl Lotus, and Sym- antec wilt be Chrysler; pieces of the remainder will end upas suppliers to the big three. Enthusiastic users may buy racing stripes and fancy carburetors from speciafty houses, but most will slick with stock factory offerings, OS/2 update Shrink-wrapped copies of OS/2 2.0 hnally hit the shelves. IBM has done a nice job with all the basic pieces. As reported here in the April issue, 2.0 does a better DOS than DOS. However, it still does not do a better Windows than Windows. Al- though you can now run Windows apps on*screen simultaneously with OS/2 apps» doing so is slow; in fact, slower on the same hardware than simply running Windows. In addi- tion, the product currently supports Windows apps only in standard VGA mode^ Windows 3 A support is absent, and hard-disk requirements are two to four times that of Win- dows. However. IBM promises a 3.1 compatibility update in eariy sum- mer, and Stac ElectnDnics has con- firmed development of an OS/2 version of Stacker. OS/2 is still missing significant driver support, and system com- patibility issues keep cropping up. However, IBM promises better driv- er support soon, and I have seen concrete evidence that IBM is trying to resolve OS/2's compatibility is- sues expeditiously. Windows 3.1 promised to elimi- nate UAE's, and has not made good on that promise. OS/2 stands a good chance of providing a more stable environment than WinSl, but still asks too many compromises in the way of speed, resolution, disk space, and device support. For now, I still prefer Windows to OS/2, and I think the vast majority of Windows users will too, IBM's best bet might be to position OS/2 against Win- dows NT, which makes more sense anyway. Then they should try to re- solve current difficulties before NT rolls out. At least well have an ap- ples-to^appies comparison. As they say in Michigan, go Bluei R-E BUYER'S MART FOR SALE TUBES: ^oldest," Hatosi." Parts and scnemaljcs. SASH lists STEINIIETZ, 7519 Ma^tewood Ave., R E.. Hammond. IN 46324. TUBES, new. up to 90% off . SASE, KiRBY, 398 West Carmel Dnve. Carmel. IN 46032. CLOCK, 1 '32MHz varia!)^ SQuaro wave Q&n&r- ator, Request specs, pnce. TROLEX, 1292 M^aT' ns Rd,, Wamiinstef. PA 1B974. TOCOM-Jerrold Impylse-Sc^entiric Atlanta Gonvefters, two y^ar warranijes. also lest mod- ij1«s lor your conw^rs. Contact NATIONAL CA- BLE. (219) 935-412S full details. CLASSIFIED AD ORDER FORM To run youi own eluainidi^ puton* «wd on MCh d th* Unn b«towMd •«nil tMs Njrm tlong HriUi yout to : ElectTontcs Now Classified Ads» 500-8 Bi Counly Boulevard, Farmingdale, NY 11735 PLEASE INDICATE m wNch category ot class) lied advertising you yyish your ad lo appear. For special headings, there is a surcharge of S2S.00, ( ) Plans Kds { ) Business Opportunities ( ) For Sale ( ) Education/Instruction ( ) Wanled ( ) Satellite Televisfon ( ) — Special Category: S25,0O PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS. (No relynds or credits for typesetttng errors can be made unless you deatty print or type your copy.) Rales indicated are for standard style classified ads only. See tjelow for additional charges for speaai ads Minimum: 15 words. 1 2 3 4 6 7 e 9 to n IE 14 15 (S46.50) ie (549.60) 17(552.70) Id (sss SO) 19(SS6.90) 20 (562.00) 21 (S65J0) 22 (566.20) 23(S7t.30) 24 {574.40) 25 (577.50) 26 (580.60) 27 (583.70) 26 (566,60) 29 ($89.90) 30 (593.00) 31 ($96,1 OJ 32 (599.20) 33 {$102.30} 34 (S105.40) 35 ($108.50) Wo iiocepl MasterCard ar^ Visa lor payrnent of orOors If ydii wish lo use ygur credit card lo pay lor your ad fill m tho lollDWing additional information (Sorry. i\o teleptior^ ordefs can be accepted Card Number Expiraiion Data Please (Vmi Nune IF YOU USE A eOK NUMBER VOU MUST INCLUDE YOUR PERMANENT ADORESS AND PHONE HUUBER FOR OUft FILES AOS SUBMrrTEO WITMOirr THIS INFORMATION WILL NOT BE ACCEPTeO- CLASSIFIED COMMERCIAL RATE: tfor tirms or indiyKluaFs cffoMnq ccxTtmerc^ai products Of serv.ci^s) 53 10 per worI pfapaid (no charge kx zsp ctxSe^ MINIMUM 15 WORDS. 5^^ discount ftx ssttio ad 6 osufls: 10% t§aOBM for same ad m t2 issues Mtttun one yeaf ; if fxepasd NOHC0UH£ftCtAL RATE: aof inAMdutfH wtio went lo buy or seff a personal tHiem) 52 50 per word, piopaid.. .oo mtnimum. OHVf RR5T WOnO AND llAllia«lmbc^ caps at FKi extr^ charge Addirt^^ SSe pef wofd MktHiofiar. E n!^f^ ad [ t>cHdt^e. S3.70 per vwrd TINT SC R EC N SEHI NO E NTlft E AD: S3.S5 per word. TINT SCREEN BEHIND ENTIRE AD PUm ALL BOLD FACE AD; S^l 50 per «^rd IXPANOED TYPE AD: S4. 70 pef word prepaid. Ent it? ad inboWt^. 00 l^-f *crO TINT SCREEN 8 EHtHD ENTIRE EXPANDED TYPE AO: S5 90 per *^Drd TINT SCREEN BEHIND ENTIRE EXPAl^DED TfPE AO PLUS ALL BOLD FACE AD; SSSO per word DISPLAY ADS: t" 2 - — S^tOiK) 2' - 2 ^^5820 00. 3 2' I 5t;30 DO General Intormation: FreqLrr:-, t.i^v^ ,ihd CKf^tjaymertt cf;$<:ourts are a>"ai,if^ t? ALL COPY SUejECTTO PUBLISHERS APPROVAL. ADVERTISEMENTS USING P.O. BOX ADDRESS WILL NOT BE ACCEPTED UNTIL ADVERTISER SUPPLIES PUBUSHER WITH PERMANENT ADDRESS AND PHDf^tE NUMBER. Copy to be in ouf hafKJs on ihe Sih ol the ihird monsr. pfc-ced^rvg if^^ diite o! ihe issufi. (i.d , Aug issue copy must t>e received by Miiy Str^) Wticn normal clo^rig date talis on SalurdOfy. Sunday Of Holiday, issue cfo^s on prGCedir\g working day 5«nd for the da^fied brochure Circkt Murnt>or 4Boi\ihQ Free fnfomatkon Card RESTRICTED technical mformation: El^ronic surveillance^ schematics. k>ck smithing, covert sdonces. hacking, etc Huge setectlon. free brochures. IIENTOR'Z« Drawer 1549. Asbury Par^, NJ 077t2. CABLE TV con^rterS' Jenokl. OaK. SoentrfiC AU antic. Zenith & many tMtwrs "New MTS" stefBO add*on: mute & ^^aiurrve kleal tor 400 and 450 owners! 1 {800) 826-7623, Ame?(, Vtsa, M. € ac- cepted. B & B INC, 4030 Bea^D-Rue Dfive, Eagan, MN 55122. WIRELESS CABLE RE{:EIVEaS 1,9 TO 2.7 GHz 30 CM PAR fWliZ DISW STStlM tl71 W ^ C hi ROD A/ITE^UA 5YSTF »l St53 gO 30 Oi CRVSEW OOMTRtkLEO SYSTIM « EUN Mocmivi INT L, ml miu trn fqh P.Q IQEjrJl^ CATALOG CHI tK£SC ntai mt. m iva} amd othir fm mtm^ Uii VIDEO Pltl}DUCTS TV. notch filters, phono recording equfpment, bro- chure SI 00. MICRO THinc, Box 63 6025. Mar- gate. FL 33063 (305) 752-9202 SPEAKER repair, Al! makes — models Stereo & pfotessiona! Kits availatrio. Refoammg Sifl.OO. ATLANTA AUDIO LABS. 1 (SQOj 566-6971. ENGmEERlUG software and hardware. PC/ MSDOS. Circuit design and drawing, PCB fayoift. FFT analysis, matherBatics. circuit ai^alysis, etc. Data acquisition, generation, I/O PCB"s< etc. Call or write for free catalog, (614) 491-0932. BSOFT SOFTWARE. \HC., 444 Colton M,. Columbus, OH 43207. CABLE TV Equtpment. Most type availatjio, Speoal: Oak M3SB Sd9.95. No catalog ^ COD or- ders only. 1 (BOO) 822*9955. DESCRAMBLERS [MMCE THE COMMEOIOH CABLE TV EQUIPMENT 1-800-228-7404 DON'T FORGET TO ASK ABOUT Ql^ FREE CAJALOG WflH ftUYINC GUIDE FRiEWDLV. PROFESSIONAl SERVICE 30 DAY MONEY BACK GUARAmV BEST PRICE - BEST SERVICE E13 I W D6>. 291 AUSin lEXAl SECRET eabte descrambierst Build your own descrambler for less than St 2. 00 in seven easy Steps. Complete instfuctions $10 00 Radio Shack parts list arxi iree d^ramblinq methods that cost nothing to try included. HARF^Y WHITE, PO Box 1790D. Baytown, TX 77520. I 1 m a 87 MRRK V CLCCTRONICS, INC O LU 88 0*tt€ Will be prtwi Soffn purehaM « Wnf*itet + CatWWI t- IrMTsksmtf" TAtSOO TA'SSOO TA477 Tran&lflfiTHJf Metal CabEiret DtSCRlPTIDN SnM«y.Wi(hte4U|r«li.«1£U MODEL TA-WG TA-m SMtaflM Artfi*^t:g'tfi»tiiriyv5i H >iiii * i fcJ i FitPri-M* AAA _ _ n^ti IJWr Hislii Ptw Mw ir* A A 5M- ?M law f !Kiw smrti? m-n 4. pmiwi A^fr i|c*u ^ ifjfljlarmii mciMdeSJU^ JOW [hnjmn CltH ftwwr M'rw K-v AA TA-tSOQ lOOW > I XW KtYd 'A' DC ^r^t tlaHi Amp A K M SwiTJ tHK Prt AAA TA-SJtti il ftTigPiiArtifr ^fa^iyflMMrtwAA TA-300D SlRfH birx^Aar ^icr Mdiw (V or Ar>v Mm ^u^al A. r*-340£l 3DMH0H-f.*WU(«J*^ AAA SM-3?d * ChHlM Ff ^iion^ CondoMr * SM«U IJSPi*™;!*3«ft**i6(IO A .. m m Ufiiwul AuiChgl]^?in4lMM« A iSOCi 17« ^ IS CO 2? t?ai 73 DQ If i.Tffibi ^ cwicito! iMi^w<-c.'; UKOtACj TA-133G lA t^lOOA TA%aD IHDd LG r»3 5>.- r T*i774 TAtSW HTSK Ti WK 21IVi7 6AiCi30vi. 2 6* T* sKm^? f n-BC? 1 A ^'XMA TA 1MC JS M 36V I 2 3A rFl-5Q3, TA a?:3A. TA40a. TA-JW. 2H» 4(K»7«A rA4TT _ MOO £*Vi;W T*1S!M«J _ n« jeViIlA TH-3S5e i?Oft W» accept asip CfMi C*m. lA*^ Onion *ia CPw» i^^ MARK V KLKCTROMCS, INC, ORDER IN CALIFORfJiA 1-S00>521-MARK ORDER OUTSJDE CA 1-800-423-RVE CATALOG & INFORMATION (213} e&8-89a8 ORDER BY FAX (2t3) 638-6865 El Nil I 'J MaiiMm Avi-. MunttrMll*?, < \ ynwil CiRCLE 93 OH FREE INFORMATION CARD GB RADIO OWNERS! We specialize in a wide vanety of technfcat information, parts and services for CB radios. 1 0-Meter and FM conversion kits, repair books, pfans. high-performance accessories. Thousands of satisfied customers since 1976' Catalog $2. CBC INTERNATrOKAU P.O- BOX 31500RE, PHOENIX. AZ 85046 LOW cost logic analyier — A must for compa- nies and serious hobbyists: 8 digital inputs, sam- pling rate from SO nsecto 1 msec. Connects to PC or compatibfG via RS-232. Only $250.00 US. For info: OPENTEK, PO Box 71. Sorel, Quebec, Can- ada> J3P 2T6. PROTECT yourself and equipmenl f rom electrical shocks. Complete unit S98,95. SAFETY- UN- UMITED, 1743 BaEdWin Road. Yorktown. NY 10598. S/H $5.00. FREE CATALOG FAMOUS "FIRESTIK" BRAND CB ANTENNAS AND ACCESSORIES. QUALITY PRODUCTS FOR THE SERIOUS CB'er. SINCE 1962 FIRESTIK ANTENNA COMPANY 2614 EAST ADAIVIS PHOENIX. ARIZONA 85034 TEST- Aids for testing units in ftiff »ervtve mode. Starcom Vll, $40.00: Starcom VI, S30.00; Star- corn DPSB, $50.00: Pioneer, S75.00; Tocom VIP 5503/5507. $25.00; S A call; Zenith. $25.00; N.E, ENGINEERING, (617) 770 383Q. CABLE test Chips S-A 8550, S-A 9500 — 310, 311. 320. 321 (specify) — S33.95. S-A 8580 338 — $69.95. Tocom 5503.07 VIP — $33.95, Star- com 6 — $33.95. Starcom 7 — S4 9. 95 TELE- CODE, PC Box 6426- RE, Yuma. A2 85366-6426. OSCILLOSCOPE 50 MHz, Hewfett-Packard, sol- id state calibrated, manual $290,00. 1 (800) 835-8335 X-159. Casli Syslcm UFETIUE WARRANTS Qualily r^icrowave TV Antennas WIRELISS CABLE - IFTS - MMDS - Amateur TV Urtrj li\qh Gtln 5adbj+) • Ti]fl«*Cite I t to ZJ Gtii. ' 55 Chanr&i E>ish System S199.95 • 36-Channel Dish System S149.95 " 20- GttarmeJ Dish System S 124.95 • Ti^i fcilcfina^ COrti 3^l?9 95 Si SCJi-xbf^Tg NwS Wif One |tS4 MQK) 95 Vlfifio S2g.9S. Ktfa4iit)ln*Q Mews Monfh^ i24.^yt Sanitfe £3 HmalaliOQS^.Simxim fJxnthtVSfmKiiSt^ Sera mb ling News , 1 Hert« I Aw, , 4 auir^la , N 1 m^. Vo l Ce/Fa X j 7 1 6 1 B74-2QSa ;] ^^^^ . ,^..^A*SmjM»|ft _ _^ \ SATELLITE TV FREE catalog — Lowest prices worldwide. Satis- faction guarantee on everything sold — Systems, upgrades, parts, all major brands factory fresh and warrantierf, SKYVISIDN, t0l2 Frontier, Fer- gus Falls, MN 56537. 1 (800) 334-6455. Outside US (216) 739 5231. VIDEOCIPHER II, desc rambling manuaL Sche- matics, video, and audio. Explains DES, Eprom. CloneMaster, 3f\^usketeer, Pay-per-view (HBO, Cine max, Showtime. AduFt, etc) $16,95, $2.00 postage Schematics for Vidoocypher Plus, $20.00. Schemalics for Videocypher 032, Si 5. 00. Collection of software to copy artd alter Eprom codes. $25.00. CABLETRONICS, Box 30502R, Bethesda. MD 20324. ANTIQUE RADIO CLASSIFIED Free Sample! Antique Radio's — j- Largest Circulation Monthly. Arlicfes, Ads & Classifieds. 6-Month Triak $15. t-Yr: $27 ($40-1 st Class), A.R.C., P.O. Bo3t 802'L9, Carliste, MA 01741 EDOCATION & INSTRUCTION RCC, Commercial General Radiotelephone II* cense. Hiectronics homo sludy. Fast, ine)em bled 1 Catalog S4 00 (refurxia' ble). QUANTUM RESEARCH, UStB^J? Ave . Edmonton. AB T5T 2SL H 0 B B Y . b road casli ng HAM; GB sij rve i ITa n ce transmitters, an^ifiefs, cabte TV, science, bugs, oihe; gm^ prqiedsl C^akxf St.OO PANAXiS. Box 130-Fe. Raradfoo, CA 95367. REMOTE CONTROL KEYCHAIN ' 3 1 CorTlp[ y O Add $ 3 snipping J 5 @ $19.95, 10 @ $14.95 VisUeCt \nO. Bok 14156, Ffomont^ Ca. 9^539 ,;:(510) 651^1425 Fax (510) 651-^454 . DESCR AMBLER kits. Cqmplele cable kitS44.95. CompleUi salellilo kit $49,95. Add S5.00 shipping Free brochuro. No Now York safes. SUMhIfT Rl, Box 489. Bronx, NY 10465, SURVEILLANCE transmitter kits lune from 65 to 305 MH:;. Mains powered duplex, telephone, room, cofntufvijion ttiloptione room. Catalog with Popular Communications, Popular Elec- tronics and Radio-Elecirontcs book reviews ot "Electronic Eavesdropping EQulpment De- sign," S2 00. SHEFFIELD ELECTRONICS. PO Bo^ 377765-C. Chicago. IL 60637-7785 HAND held digital recorder annoyncef. New technology permits permanent slorage erf person- al recorcings and messages. Plans S9.95. Kit S49,95 SefxJ check or r5iof>ey onJer to CO&JUI, 303 Nofthwoods Drive, Ballgroynd, GA 30107. GREAT Pioiict. Siitm Ssin iQfmnds you i^ftten you lorwt SSTSR (Tim SignaJ Hominder) beeps 3 saccn^ after 15 6«c- ondt Cyct& r^ais unlii carcdkid Uoofeiruiswii^ tto- sblod Mftmn jbr^kmci; compad dcctmtics kit fnounts ttp yOurlKh^ Parts, esse. PCB. SC^crrcmc. indlruc- tfm %20 PRO, a.'SaS. visa. MC t-8O0^39e-5«l5. Sttcfit Swiv 1€I7 BasjJ Dr., Colwmbua. OH *3327. DESCRAMBLING. New sec^l manual Build youf own descrambiers fof cable and subscflp- lion TV. Instructions, schematics for SSAV1. gated sync. Sinewave. {HBO. Cinemax. Showtime. UHF, Aduin S12,95. S2.00 postac CABLETRONICS, Box 30502R. Bethesda. 20824 age. .IAD CREDIT card cncodmg standard exptalnod in piatn English. I llastralive examples irKluded. send SS 00 BSC, Box 1841, Alexandria. VA 22314. CELLULAR hackers bible Theory — hacks — modilicitions - S53.95. TELECOOE* PO Box 64g6-X?<, Yuma, AZ 85366-6426. WIRELESS guitar transmission system. Build your own for 539.95! (kit) RADIOACTIVE TRANSMISStONS 1 (600) 263-922T Exl. 2587. REIVIOVE LEAD VOCALS From 513-444-2276 BuiFd this kit. wttich rvmovn lead voca.'s from standard liareo tvc^s. CD'A. tapes or FM bftudcasti Smg along with the bacld Impair dI VCRs, TVs lechructan oaaily turn Lcnil fof WhlO S5" S4» (1 3J {l£^79} 4 KHz-27 KHz. 8 Frequency nspanm: 30^500 Hz 5 0 wgs Pg jS^ tO O wftRs manrtL^ powef handing c^psb^ty^ S3^ (80yp> In-Wall Subwoofer pOmner t Wvi a ohnt Hfiffi iilfl^ai cm Piezo Super Tweeter Ttu£ extremely ^^^^c jrvorporatet al the ^^^^^B advantagts of piofo ^V^PB tweeters into 9 smaM package lt%ai C4n tiiO mounted almost anywherio. Freuyurtcy robpanse: SK-aOKMi. SPL; »7ro for uso ~ With vety tiiQh powur stemo syttofns and ! . ' in ©iifefnely lona catilerwis. Ovef250 strantls ol 3fi fia, wve Extra itydK, dSr PVC rt^utaHon. PIm* order Irt fnylUpitev of 5 feet. «FIH-10G-151 BBC 12" Dual Voice Coil Subwoofer Super qualAy ttaltan made cai^ Iranio dual vaicie cQit stUiHioof er Paper oorw M#t loeir !;i,sjrrDUnd. 2*dUil voice coil, tea 4S H/ Frequency respoflfiri 96.69 IW/IM. VAS 373 cu fl., QTS^ .338. Bee Nsw3at/Fa. Not weight: !) itjs. #RH-294-130 Sen£itrv«ty 90(^lWaM Dmensians: 1 £hSS' (W) iU 1 3' (01, Hote dimonsions 9^ {WJ x l3^ tD Wetwe.^?it di|}4 #flH-30(W3o lldi^ sas* $79^ 'Parts I . -^^1 f/cxpress VCR Parts Assortment Converiicnl assOftiTHOf^l qrf cl*P5. waiTier^. spnngs. and screws. lOpiocoa each ol 4 sjzcs of dipa. to peces 2 Etze^ d retainiog rings, lOpiflOoa OtH (^iit^ti of a tiZMOf - ^ Ecn^ion and comprosSJOn spnnqs anq 24 aSTfOrtod screws. Tola! of 246 pieces 2Si SI 39' (1-3) $128«* (44jp) fleH-43M15 S6» 8 Ga. In-LI {4-up) Suction Cup Mount Fuse Holder Cellular Antenna «RH<070-BIX) 0RH-2&5-2OO Sae* tog«1^lor &ak4j4ite fuse twtder vrXh 3 ga. wifia Tof use witn AGU typo rr^4f^ exci^TMltrx) S * Foret^ declination OfS^^ - send 55 00 U S fund-. Tor catatof] poslage * ^ "O00*338"0531 S49« FREE CATALOG anCLE 56 ON FREE INFORMATION CARD DESCRAMBLERS Convaters. i\ Cmiwh, Vksamhkn, more \mxm All major brands carried *JERROLD, *TOCOM, *ZEN1TH *GENERAL INSTRUMENTS *SCIENTIFIC ATLANTA, *OAK *irAMLIN, *EAGLE, ^PIONEER 7th Year in business. Thank Yow Member of Omaha Cliambor of Commerce 1 Year warranty oit new equipment 30 Day money back guarantee Orders shipped from stock within 24 hours CALL TODAY FOR A FREE CATALOG 1-800-624-1150 B ^ S C.O.D. % ^ 876 so. 72nd SL ^ CONVERTERS W/REMQTES- PANASONIC^ TZPC145 65 60 CALL STARQUEST- E-2550 65 60 CALL E'2Y550 75 65 CALL WITHOUT P^rfMiSSlON MAY EUBJECT YOU TO CIVrL OH CRIMfWAL PElyALTlES YQU MUST CHECK WITH YOUR LQCAL CABLE COMPAhJY AND PAY TOP ALL SERVICE YOU M$E IT IS HOT THE lMTE3^aT OF LAKE SYLVAN TO DEFRAUD ANY TELE Vision OPERATOfl AND WE Wrti NOT ASStST AMY COMPANY OR I-NDIV30UAL IN DCINti THE SAME LAKE SYLVAN SALES, INC, SOf^RY NO MtNf^ESOTA SALES CALL FOR A CATALOG NOW!! 800-800-4582 CIRCLE 179 ON FREE INFORIAATION CARD CABLE TV DESCRAMBLERS * CONVERTERS^ and ACCESSORIES. SAVE MONEY. OWTBENT! PANASONIC. JERROLD, OAK, PIONEER, SCIENTIFtC ATLANTA AND MORE. LOWEST PRICES- FREE CATALOG. "compa'nT (800) 234-1006 DEFEAT videotape anti-copy, PCB, PAL. instfuc- tions wvPSH S17.50, NORM HOGARTH, 955 NW Ogden, Bend. OR 97701. VJDEOTAPE dybtJirrg enhancer. Compfele kit $39.00. add $5.00 S.'H. Plans and instructions $5.00. Free brochure. C-TRAN. 1757 W. San Car- los Sl, Suite 117, San Jose. GA 95128 5205 CAMPALEHT ~ Backpackable perimeier alarm kilS39.95 + S3. 00, Send stamp — info PROTEC- TION CONCEPTS, 340Torrance Ave., Vestal, NY 13850. CAItLK T\ i)i:St"RA.\ll{Li:kS BEST BUYS BEST SERVICE eLTLLETFROOf TV TESTED WANT TO BUY; TOCOM, SA a50#,DPV72ia FREE Catafag HunUVf*lpft t402)3at'3228 8 0 0*835-2330 £t«lfonlci™ 1710 S0.l2Jtii Cl*I2A Om*hi, 68144 WANTED INVENTIONS/ new products ideas v^^nted call TLCI for free info rmation/invon tors nowsEettof. 1 taOO) 46B-72O0 24 houfS'day - USA Canada. INVENTORSr We submit ideas 10 industry. Find out what we car^ do for you. 1 (BOO) 2e8''IDEA, INVENTORS INVENTORSI Can you patent and prof i I from your idea? Call AMERICAN INVENTORS CORP. lor free inform aiEon. Serving inventors since 1975. 1 (800) 338-5656. — — — — - — -T Learn Computers! - 1 Hmne study. Be- conit* a personal computer expert at home and in busi- ness. Ijeam al ytmr own pace, Fjtcitinj^ and t asy l(j follow. Send or cxill today for free literature. 800-223-4542 X.i[Tie Address_ Cilv . Stale. Zlp_ SCHOOLOfCOMPUTERTRAiNfNG 221fi l-'feriineter Park Depl.KJ3^2 Atlanta. Georgia 3034 J ASK R E continued from page ?5 I'll assume that you've already tned getting in touch with the origi- nal equipmetit manufacturers and found them to be either no help or out of business. There are several companies that make new tape heads and also have tape-head rec- onditioning services. Here are two companies in the tape- head business and if they can't help you. the chances are they'll be able to direct you to someone who can. International Electro Magnetics, Inc. Eric Drive and Cornell A^/enue Palatine. Illinois 60067 (312) 358-4662 Nortronics Company, Inc. 8101 Tenth Avenue Minneapolis, MN 55427 (612) 545-0401 There's no guarantee that either of those companies will have exact- ly what you need, but I'd be sur- prised if they can't supply some- thing similar that will work just as well R-E EQUIPMENT REPORT continued from page 23 CompuScope Lite card and soft- ware. At $595. the product is a price/performance leader How- ever, many sophisticated users will find it inadequate for their needs. The $995 64K version adds consid- erable measurement power, as do five CageCalc software modules, each priced at $100. One module, for example, lets you add. subtract, multiply and divide signals, and cre- ates a dual-channel digital volt- meter Another lets you differentiate and integrate any signals displayed by CompuScope. while yet another lets you use the card as a frequency counter Even without the add-on modules, you are free to write your own custom programs to manipu- late and measutB signals. And that's the real beauty behind PC-based test equipment. R-E 7 * * * * PfreSf NTlNG * * * * CABLE TV DESCRAMBLERS JnHOill, HAJHUN, OAK AND OmtH FAWOm MAftlUf ACTUfft F?S * FtNEST yiMHEANTT PSOOJIA^I /^.'A^^t • OADGK^UVf tDFIOUSIDOC WTTHM 24 h«S ♦ ^ K«AX>t Ciim CWDS ^CEFTe^ FOR All rNFORMATlON PACIFIC CABLE CO,. INC. 7a2SV? ftesoda Blvd., Dept. 2) 17 Respdo. CA 91335 BUSINESS OPPORTUNITIES YOUR own r^icJio sl^Hion! Licensed unhconsed AM, FM, TV, cable, rnformalion Sim BROAD- CASTING. Box 130-Ffl, Paradise. CA 95967 LET the govornmem fmafic© your small business. Gran Is/loans to S500,000. Free recordBd mes- sags: <707) 41^6600. (KSl) EASY wtKkl Excel Eent pay! Assemble pfOducts a! hOTTie. CaJl loll Ifee I (800) 467^5566 Ext. 5192, HOME asserr>bty work availabto! Guardnteed easy rrmt?y' Free details! KOMEWORK-R. Box 520. Dafiville, NH 03819 FREE CATALOG » CABLE T.V. BOXES - ALL TYPES ■ ■ LOW PRICES " DEALER PRICES • MOMEYMAKERSI Easy! One man CRT retRiik*- I ng machinery S6.900 00 rebuilt, StS,900.00 new. CRT, 1909 Louise. Crystaiake, IL 600t4. (815) 477-6655. FAX {615) 477-7013. MAKE $7S.0O0 00 to S250 ,000.00 yearly or more fixing IBM color monttors. No investment, start doing It from your homo (a telephone mquired). Information, USA, Canada $2,00 cash lor bro- chure, other counuros S10.00 US funds RAN- DALL DISPLAY, Box 2t68 R, Van Nuys. CA 91404 USA. FAX (616) 990-7803. WHY pay retalj? Order your computer equipment from ihe same wholesale suppliers as dealers letajlefs For a fast of over 100 who I esaJe suppliers send SI 0.00 check or money order to CRM. 2615 EdenbOfn. Suile B. Metairie. LA 70002. Allow 4 !o 6 lor delivery CABLE TV -800-582-1114: FREE CATALOG GUARANTEED BEST PRICES < IMHEIMATE SHtmWi r---.M.K. ELECTRON ICS HBsa raiiffl 8363 Pines aiVil Suite 27& MASTERCARD AND VISA are now accepted for payment of your advertising. Simply complete the form on the first page of this section and we will bill. BUY BONDS MCM Electronics Has a Constant Flow of New Products for You to " Choose From Today's tough marketplace ni^akes the ready avaiEabifity of quality efectn^nic parts more important than ever. That's never a concern when yoy deal with MCM Elearontcs. Just go wtth the Ifow— our constant ftow of nm products for atidto, video, computer and telephone repair work. With each catalog, we add hundreds of nev^ prodtjc^s to our current stock of over 17,000 top- quality items. And since they're stocked they're ready for immediate shipment, within 24 hours from your teleptone order Sd €alf our experts toll free at 1-800-5434330 or FAX 1-513-434-6959. They^re ready to keep the parts you need flowing to guarantee a steady stream of work And ask for our new MCM ElecfrDntcs catalog while you're on the phone. 111 Mil 1 e.ECTHON«CS l-aW54S4330 MCM ELECTRONICS 6SO CONGRESS PARK DR. CENTERVILLE. OH 454S9-4072 Source No. RE-78 CIRCLE B7 ON FBEE INFORMATION CARP A Monumental Selection Test} Measurement and Prototype Equipment Jomeca Sold!erle<^s Breadboards Jamcco's long-lasting bread buards fcaiurc scrmi -printed color toordiniitts and arc suitable for nnany kindi of prototyping and circuit dcj^ign, Larger models feature a Keavy-dut)" alumintjm backing wiih voltage and grt^unding psti. Pirt Dim. Cpnucf Binding Poinu Price JE21 y.lS^ZMS 40CI 0 JE23 ^Scik» 19.95 400059 National UgicDatabnak ...19-95 400015 Nation-i! [>dU Ac^tiiiition Linear Devices DatalxwL.l 1.95 400104 National Special Purpow: Li neat De^'ices Da tabook-, 11,95 400014 National l.S/SOTL Databook J 4.95 230S43 Intel Menior>- Daiabock».24.95 270645 Intel Lndietidcd Controller Pf occssttf !i Darabfjok . . *. .. »24 . 9 5 AtMimnai Ddubo&h avaikbiel Mefex Digital Mtilfi meters • Id and held, high accurac)' • AC/ DC vultage, AC/H' currentn resisfance, diodes ► coniinuiiv. transistor hi E (except M3900) • Manual ranging w/overload prcnection ' Conies with probes, batteries, case and manual M5650a!:M4(i50only: • Also tncasures frequcnc)' and capacitance M3800 3. 5 o igit M ul I Emc I >?T 539-95 M3610 3,5 Dij^it Mulclnitficr 459-95 M39a0 M3650 M4650 5-!i Pipe .Mulumticr «Kb T^Kh/DwdE 559.95 3^5 Vl\p\ Multimeter w/FttqutJiLy & Cap.ititarice $74,95 4.5 Di^jii vi/PrcqufiKv & GifULUJincc & Dju Hold .Sw][t!u -.599-95 Jameco IC Test Clip Series ' T«i Clips are designed Ibr temporars' connections to DIl^ package components ■ Heavy-dury spring badcd hinge provides psiiive contact Pam Np. Dtsfjjption Prk. JTC16 I6^pin (for 8, 14 6: ] 6-pin ICs) ,,$5.5 JTC20 20'piii (for 18 2fl-pEn ICsl ...6.9 JTC24 34-piii .....7-9 JTC28 2K pin 8.9 JTC40 40-pin 11-9 EPROMs - for your pragramming needs Pa rt Nq i Pdts fan IVi TMS2516.„ S4- TMSZ532A 6, TMS2564.... 5, TMS2716 5- I7{32A ..--3- 2708 „. 4. 2716 3. 2716 1 ..A. 27CI6 4. 2732.. 4- 2732 A-20 4. 2732A-25 3, 2732/V-i5 2. 27C32 ...A. 2764-20 ,...3. 2764-25 3. .25 2764A-20 $3-75 ,95 2764A-25 »3.49 ,95 27C64-15 3.95 ,95 27C1S4-25 3-49 ,95 27C64-45 -»2-95 ,95 271280TP. 2.49 ,95 27128-20 7.95 .25 27128-25..,, 7J5 25 27I28A*15 .-4-95 .95 27128A-20 4J5 ,49 27128A-25 .3.75 ,49 27C128-15 5.75 .95 27C1 28-25 -7.95 75 272560Tf».-..-*....4.19 ,95 27256-15 5.49 75 27256-20 5.29 27256-25 $4-8 27C256-I2 6.4 27C256-15 5.9 27C256-20 ,5,4 27C256-25-*.. .4-9 275120TP 4.9 27512-20 6.7 27512-25 5.9 27C512-12.... 7.4 27C512^15- 6.9 27C5 12^20 6-4 27C5 12-25 .5-9 27C010-15.,... 9.9 27C020-15.,. 17.9 27C020-20- 15,9 68766^35.-..-,.. 4.9 A.lt.T* EPROM Programmer UVP EPROM Eraser Pf£»grims all currciit EPRO.VIs in ibe 27lfi to 27512 Tans;c plus tlieX2864 EI^PROM RS232 pen • ,So[Wjre included Efaics all EPROM s • Eiuses \ chip iti 15 in inures and fl chips in 2 1 miti UV iniensiT)-; 6800 \miCW EPP,. ..5199.95 I DE4„, .„... ..-589.* • Partial Listing • Over 4000 Electronic and Computer Components in Stock! * Call for quantity discounts. CIRCLE 114 ON FREE INFORMATION CARD at Competitive Prices Computer Upgrade Products and Electronic Components Upgrade your existing computer system! Jarneco will help you upgrade easily and ecofwmically* fwjitsu 1 01 -Kay Iiihaiiced KeylMiMd FKB470a„ • IBM KTXT^AT ud c«ifnpiinlik oKnputias • AiirofMrkally ^idxi betiwen XT or AT ■ LED tntlicuon iot Ntun Lodk. Capt Ud.jalSooQtx>dc • Txttlc FtaSaei -S79.95 JamMO 80386SX Motherboard * \6htHi prooewi^ speed * Zen> or S-b* Afatry nwrt upgrade produm imiiiabU! JE1030 JE1036 • ] ]a/22(>V mi[i.habk 1 50Witt POXT Pwwr Supply „«.„.S69.95 ZOO Wjtt AT PiwTr SuppK „.»„».S89.95 i JEIO.W littegrotod Cirivfls* an No. L2 4uao .„.3.25 4LS04 .25 4US08 29 4LS14 J9 4LS30 » * 25 4LS3a .25 4LS74,„» „.,19 4LS76 A9 4LS86 .25 4LS112» ,,35 4LS125 39 41^1.^8 39 "4LS175 .35 '4LS193 59 ^4LS244 69 '4LS245 „ . M '4LS373 f>9 ■4LS374 ,69 Linear ICs* ^L0e2CP. S.59 M31TT , S9 M324N J5 -M336Z , «.L09 -M339N»^». , .45 ^."E5>5V ,29 JV1556N _ , „.„«„,49 -M723CN , A9 41CN *29 -M1458N 39 Jill486N___™ .45 _\!14«9N,.. « 45 JLN2003A , „ .69 Jkl59l4N 2,49 MT5532 'g05T,™. '812T ^\A9 No. £iiii£muiL. Price •lilCKKJA'MftO 421000 A'm 60 42IOOOA'>^70 i2l00aA9B'80 IHP 1MB DIP 2^>K s!^t^t 1MB SIMM tMBSlMM mm L59 sons 5.99 mm 5.49 Wcii.-.- 16,95 Kjtn^.««.54,95 "o»..,„..59.95 SOni 54.95 MUcellaneous Components* Potentiometers Vilufi j^^bbte (inirrt ahmt into qucc mirkd Mmh IK. SK, \uK. :oK, ^OK, mK. lvi>g 431'XX 65PXX 3/4 Watt, 1 5 Turn..... $.99 l/2Wati, 1 Turn 89 T^nsistors And Diodes PN2222 S.12 IN751 SI 5 rN2907 .12 C106B1 .65 LN40O4 ,10 2N4401 .15 2N2222A .25 1N4148 .07 IN4735 .25 2N3055 .69 2N39a4 .12 IN270 ^5 Switches JMT12J Srni.On.tlntT«¥jtk) $1.15 206 8 %m. l^pin iDIf) 1.09 MPCiii %nm cPmli Butiewl................. 39 DB25P DB25S DB25H DB25MH Connectors Mjk2!J'pin Tcmdc. 2S-pirt Mttai Hood IC Sockets XC209R LEDs S.65 i *75 I 39 135 I $,14 aLP S.iO 8>?™^ $.54 I4LP ,11 14 WW .79 16LP .12 16 WW .89 24LP .19 24WW 1.39 28LP ,22 28WW 1.69 40LP ,28 40WW 1.89 XG556G I I 3/4. (Green) .16 1 XC556R XC556Y Tl 3/4. (TUd) I ! 3/4.(Ydlni.) ,12 ,16 Call or Write for your FREE Spring Catalog: 1*800»637*8471 24-Hour Toll-Frce Order Hoilitic: 1*800*831*4242 J AMECO ELECTOONC COMPONENTS COMPUTED PRODUCTS 1355 Shoroi^'ay Road BdmonuCA 94002 S3a(K) Mtoimtun Order FAXM •8fKJ-237*6948 aw«iOH CARD ELECTROHIC ^ PRODUCTS and KITS Spa-ce Ships in KG Weils Wir or th# Worlds? MYSTERY Levitating Device Objects Afltai on air and move to ttie louefi. Defies gravifyi Ama^ gift oomafsatioo pi^, mgc tnck or greu sbentifc project AMT1K E«Y-to'y miPllfl explains how. when, and wnciv to listen in. Its 320 heavlly-illuslraied page^ are packed with advice on: • antennas • selecting the right radio • accessories • reception techniques Learn how lo hear the BBC, Radio Moscow, ham operators, ships, even s^es and ^'piniie* nidio stations! Includes hundRtls of station frequencies and the times you can hear them. Only S]b35 at radio equipment dealers, or order direct from Hi^nTexiI Add S3 shipping (S4 Canada. S5 elsewlverc). CA ado sales tax. funds mily please. l-|ic|hText p«i b J I c ■ t l«iii« Inc. 7128 Miramar Ro^d, Suiic 15L San Diego. CA 92121 Enter A World Of Excitement with a Subscription to Po pular Electronics Get the latest electronic technologyand informotion monthlyl Popular Itlectronics brinjjs you informative new prod- uct and literature li.^tings, feature articles m test equipment and tools— all designed to keep you tuned in to the latest de\*elopments in electronics. So if you love to build fascinating electronics, just fill out ihe subscription form below to subscribe to hjpular Electronics . . . Its a power-house of fun ftjr the electronics enthusiast. EXCITING MONTHLY FEATURES UKh ySPtClAL COLUMNS □CONSTSUCTJON J FEATllJfB jKANDS-ON- REPORTS FOR FASTER SERVICE CALL TODAY 1-800-827-0383 |7 30 AM.8;30 PAA-EASTERN STANDARD TIME) j Po pular Electronics subscription order form YKI I Ft* Kir Il3 tsAUcsl kit only S18,9S That"* :i sotv^ of ol^ the T^'sland rna'. □ PigimentEiidosed □ Bill mt hltr Pkas£diaifcre>- □Visa □Mastcratrd ^ * M t n I I i I I M I I PLEASE Pf?lNT BELO\ cm sitHi UP Mott 6 f « ii wnki Um tJdirecrf ^ finA mue. L'-S. Fun^ only: In Cwudi jiU Btatt^ i lo£ludr$ Q S Tl M\ Other COURTEOUS SERVICE • QUALITY PARTS • DISCOUNT PRICES ' FAST SHIPPING Electronic FLASH ITT Magidla^h. Qriginairf dss]gn»s tw^ "Preedom Conn^ciioft*' g nits are r«- qyired. A wwlt-knawn nafiofjaldlicounj 10/ ctifitfi. J ell* theie for TOre ihan twee Q'ur prjoQ. Opmaies on 4 AAA ba^ia-rie^ fnvt induded). CATilR-1 $9.^5 FLASH UNTTS 1,1--, ^'^ r MEW corrpacl; llash as samboes Ir&m a carneia manufaduipr. Operator pn a Vdc. Measures 2 1/r X 1 1/4\ Ideal for usfl as a si rob*, wsktning !^ht or arter- lioft g«ttei. Indudfis a hook-yp diogfam CATiFSH-l S3.75eacti to for $35.00 * I00for$32fi00 Surface mount LED chip, CSoar when oH, green wKe^ lit. Ver/ tiny ■ whole ur^it is 0. 1 1 5" X0.05S' X0.C5'!h-1 tOfaf St.SO" l00forSl3-{XJ CR££/^ CAt#LE0'2 10 for 1^,00* 100 lor $17.00 YELLOW CATir LED-3 lOlof S2.00 ' 100 for SI 7X0 REDUCED PRfCES FLASHtNG LED Wh buil ini llashin-g c^^cuii 5 vol! operation. T M^'^ ||5mm} R£D SOC oach CAT*LED-4 1010IS4.75 afJBEN 7SC each CAT* LE0-4G 10forS7,00 Y€LLOW 75c each CATiLEO^V tOforSZOO ifO HOLDER Two p»ce hoJdet. ^ CATiHLEO t3 L 101or65 2 prong rion-polaiiiifetJ plugs. Mot rocommendsd for use wiih heoterSr Re- quires, a 9 voll battery {noi inc'ijded) . A.C. Line Cord 2 for $17.00 6 " Slack A. C. power a>rda, SPT- 1 Insulation;. Polarized plug. Hanked. Qkjit tCAC^7 2 for $f 00 * 100 I of $45.00 ' 1 000 for $400.00 D.C. Wall Translormers (120 Vac INPUT) \ Electret MIKE Plug Slylti 4Vdc 70 mjL 2.5mm co-Stx rogarr^e DCTX^TO 12.1X3 6Vdc 300 rrjs. 2.1 m.ri co-an pOSilrvA DCTX-632 S2.7S 8.3 Vtf 0 to ma. t>attQry snap DCTX^310 fl.SO OVde 30O rna. 2.1 mm B^ax posilive DC 1X^93 2 S3 .00 l2Vdi: )COrra. 2.1mm cB-a3( nega:ve negaStve DCTX4210 S2,&3 12Vdc SOO ma 2,1mm CP- ax DCTX-iaS S4.50 l2Vdc 1 Amp none DCTX-I£t $6.50 14 Vdc 700 rrj.. 1.3mm QO'ax negative DCTX'1470 SS.25 15 Vde 2.5mm co-ax nesa!fve 0CTX-1&40 54,50 Hrgh elf c'^ncy. crrn- d'ireci'onaL minialure 1 I flb{:tr4l Dondof^ser ^^—^ nrvcrophone element Low current dfain, good signal ro nofseiasio, oper- a'cs on 2 Id 10 Vdc. Ideal (or nobe- acJivaled a'ajm* lelephonei, lape re- corders., and other aool^liona. 0,39^ d^iXO.Ol'hlgh. ftCi CATi l^tKE-10 97; 2oopcii$i5o.Do Men BACKLIGHTS | TMi^ftMEHS POWER SUPPLY At last! A lo* cwt ol«Jrolumine»cerl glow stJip arid cfiivefi&r. These brand -new uniis were designed io backlight smaN LCD TVs made by Ihe Citizen Watch company ^ The inverier circuit changes 3 Of 6 Vdc to 9pr projiimaieiy lOO Vac. ihe voltage fequirod to- light Iho glowslr^. LymifiBBcont surface area is 1 T X 2.25V The si rip is a Siilnnon co^or in its on stale, and glows white when e removed easil/ Iromp-aslic housing. Ideal lor special r-ghjing f^locls,. Crttiofiii *J2TA op#rales on 3-6 Vdc CATl^ BLU-92 LAROE QUANTITY AVAILABLE - 10 tor $32.00 f ^50 100 br $275.00 New 17 Vdc, 210 wA wal trar*stofmefS. S h. cord. tJnusual oo-axial device on end ol cold can Pe cut o!l and used lor anolher applcalion. Large quantity available, CATf OCTX-1721 $1.50 ea. T00lDr$1.25 each 1 000 fcrS 1.00 each 10AMPSOUD STATE fWJiY_ {US£0} 10 amp soEid state relays, ramcved (romeauipmenl and lesied, Conlrol voltage; 250 volts AC ai 10 amps. Standard "bock- ey-puck" size: 2 IT Hi I.TT X 0.95'. UL and CSA lisled. CATiSSRLY-llU $8 25 eacfr » 10 for SBO 00 PC Board With Rf Modulator (and kits otoUter pans) We recenily received a bad o^ these PC . , =^ boards which conlain, among other thing*^ ' , ' n * ■ " a RF modufator, Wilh a little dftJWWerinfl J- ^ r'^.,* - ^ you shou Id be able lo tbef ^e a working * 'i " i ~ ^ - unit from !he board. Alio contains a 7fl05T ^-r ^ — I - voltage losjutator with a coupl« ol heatslnKs. - ^-t ~ ' 20 ICs, capacitafs, reststofs, diodes and rs**^. v 1*':';.^'^, connectors, hio hook' up infwrrtatkjn avaitabla 'I ^ .'^^'"^ on Ibe modublor. '"^""-^ ''~ ' CATSVM&'l $2.75 each Regutated switching power tuppV- Inpyti 11 7 Vac Oulpyt; +5 Vdc @ 6 amps ■5 Vdc 0 1 arrp *12 Vdc@ 3arT^ - 12 Vdc@ 3 anijs Overlaiid and short -circuit projection. Vcitage adjusimen! trimrr^sf. Fused, 9.6?- X 3.5' X 2.22- venlod aluminum chassfs. fle^^yires itandard lEC slyle power cord f no* indudad). CATfPS SO $22.00 each Posi^r cord tor above svi^tching power SL4}pry, CATK LCAC-C? $3 00 each Pl^o Et^ment 3 wire pieio element. Taryo Yyden Co, # CB35aOKJ^4 Se^-encited peio etsctric diaphiam. t.40" d^meler % 0.021' Ihick. Resonanl resistance: 400 ohnu. 5" cold-coded leads. CATf PE-12 St. 00 each 10 for Se,50' 100 for $65.00 r ORDER TOLL FREE 1-800-826-5432 FAX (818) 781-2653 • INFORMATION (BIB) 904-0524 Call Or Write For Our Free 64 Page Catalog Outsfde ihe U.S.A. send S2.00 postago for a catafog. Minimum Order $10.00 * All Orders C^n Bq Charged To Visa, Mastercard ^^^^ Of Di$CQverc3rd * Checks and Morjey Orders Accepted By MbU * Oalifoma, Add ^^^J Safes T3X < Shipping And Handling $3.50 for the 43 Continerttal United States - J!!!5!* Alt Oshsrs induding Alaska. Hawaii, P.R. And Canada Must Pay Full Shipping * MKw QuanhVes Limited - No CCD, • Prices Subject to change without notice. {x^lH MAIL ORDERS TO: ALL ELECTRONICS CORP * P.O. BOX 567 • VAN NUYS, CA 91 m CIRCLE 107 ON FREE INFORMATION CARD CABLETRONICS CONVERTERS 1-4Linil8 SUnlls 10 Untie PANASONIC TZP 145 STAR GATE 2000 *MCC 3000 $S8.00 $79,00 $25,00 $75.00 $70.00 $69.00 $65.00 $19.00 $15,00 ADD-ON DECODERS SB-3 (NEW) $50.00 $45,00 *SB-3 FACTORY $45,00 $39,00 SA-3 $55.00 $50.00 DTB-3 $65.00 $55.00 KNt2A.2or3 $49.00 $45.00 *HAM1UN WILD 1200-3 $49,00 $40,00 *ZENITH SSAVI $1 65.00 $1 49.00 SA-DF $159.00 $139.00 JERROLD DPV7 JERROLD DPBB SA8580 COMBO *JERROLD DRX-3-DIC JERROLD DRZ-3-DIC *OAK M35B HAMLIN SPC COMBO ADD $10.00 FOR VARISYNCH COMBOS $299,00 $319.00 $299.00 $165,00 $175,00 $45.00 $50.00 $149.00 $259.00 $225.00 $105.00 $115.00 $35.00 $44.00 $43.00 $35.00 $45.00 $50.00 $40.00 $35.00 $125.00 $125.00 $239.00 $249.00 $21 5.00 $89.00 $99.00 $30.00 $44.00 ♦Refurbished as New QTY ITEM OUTPUT CHAN^JEL Callfornln Penal Code #593'D Farfaids us from shipping any c^Iq descrambllrvg unUtQ anyone rosidlne in the stata of cafiforfiia, Prtces subject to change wll^iout notice. Please Print PRICE EACH SUB TOTAL Shipping Add &.€0 Par unit DOO/CfoditCftid Add 5% TOTAL TOTAL PRICE State _C[tv_ n Cashier's Check Dlvioney order □ visa OmC CC# _Te":( )_ □ coo Evp. Oate OECLARATIDN OF AUTHORIZED USE- 1, the undersigned, do hereby dec tare under penalty of perjury that all products purchased^ now and tn the future^ wilJ only be Lr^e^ on TV syaTeni& with afl applicable f&deraJ and slate law^- FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUS9TANTIAL CRIMINAL AND CIVIL PENALTIES FOR UNAUTHORIZED USE. Date _Slgnied_ Cabletronics 9800 D Topanga Canyon Blvd. Sutt© 323, Chatsworth, CA 91311 For Free Catalog, or to place an order call (800) 433-2011 • FAX (818} 709-7565 THIS LAND Gave us our past . . . It can give us our future Help protect America's soil and water today. We owe it to our children. Find out what you can do. Call 1-800-THE SOIL to get your free kit. Umlcd Slates Department of Agriculture Soil Conservation Service 4 I E C T R 0 N I C S :00W Canoga Ave., Unu S-E CtiaTswcrlb. OA 9011 LASER DIODES STOCK s; MFG. WAVE- LEWGTH OUTPUT OPER. CURR. OPER. VOLT. 1-24 2S^9& 100+ LS&22D TOSHIBA a mW as mA 2.S V 129.S9 123.49 1t1.14 LSB200 TOSHIBA 670nni 3 mW B5 mA 2,3 V 49,99 47.99 43,19 LS9201 TOSHIBA fi7Cnm S mW BO mA 2.4 V 56.90 51.29 LS9211 TOSHIBA 670nm 5 mW SO mA 2.3 V 69.99 e6>49 59.S^ LS92tS TOSHIBA 670 nm 10 mW 45 mA V 109,99 104.49 94.04 LS33Q0 NEC 670nm 2 mW SS mA 2.2 V 59.99 56.99 51.29 LStJ22 SHARP 7flDnm S mW €5 mA T.7S V 19.99 18.99 17.09 SBiaS3 PHiLUPS 920fini WfnA 2^V m»9 10.44 9.40 WAO II PROGRAMMABLE ROBOTIC KIT • ( ) Powef SOLirco - 3 AA baltenes (not irtcluded) DESCmPTJON W V96 1 WAO if ProgrBmm$bS9 Robo tic Kit W1IAP tnierlBce Kit For App/a ii HE, Tfie pen mechanism m- cruded wfth t>i& Fot>ot alFows it tOdr^w in addition to drawing straight fines, tt can also accu- rately draw Circles, and even draw oul words and stiort phrases. WAD II cornes wUli 1 X 4 RAM and 2K ROM, and is pcGgrarnmed directly vta the keypad attach &d to il. Wiih its buJiE-in conneclof port, WAO w IS ready to cominunioate wilh your corr^puler. With Ihe OpIiOnal inferface kil^ you c^n con fleet WAO If to nn Appfe lie. or II - computer. Ediling and transJermg of any movement program, as well as saving and loading a pTogram can be perlormcd by the Interface k'tl The ki( mclude& SOltware. cabje. card, and inslryctions. The programming language is BASIC. 1-3 10-24 as+ SINCE 1983 — YOUR I.C. SOURCE — AND MUCH MORE!! NO SHIPPING CHARGES ON PRE-PAID ORDERS!* NO CREDIT CARD SURCHARGE! SCHOOL P.O.'s WELCOME! PROTOBOARD DESIGN STATION • Varlabte DC ouipui -5 - to -15 VDC @ 0.5 amp, ripple - 5 mV • Frequency generator frequency range: 0.1 Hj to 100 KH2 in 6 ranges output von age; 0 to 1 10V (20 Vp-p) output ] m peda rrce: 600 {exceps TTL J output currenl; 10mA max., stioJl circuit protected output waveforms: sine, square, trrange, TTL sine wave; distortion 3% {10 Hz id 100 KHz) TTL pulste: rise and (all lime 25ns drfve20TTL roads Square wave: rise and fall time ±1.5 S • Logic Indicators 8 LED's, active high. 1.4 voJl {nominal^ threshoJd^ inpuls protected to ±20 volla • Debounctd puihbultons (pulsers} 2 push-button operated, open-coifector output pulscrs, each with 1 normally- Open. 1 rtofrtially-closed output. Each output C3;n sink up to 250 mA • PotenUometer^ 1-tK , 1 10K , all leads avaEldble and uncommitted • BNC connectors 2 BNC connectors pin available and uncommitted sheH corinected to ground « Speaker 0 25 V/. 3 il • Breadboarding area 2520 uncommitted lie points • Dimensions 11.5" long X W wide x 6 5" high • Input 3 wire AC line tnput (1 M V. 60 Hz typicjif) • Weight Tibs 79.99 39.99 75 99 37.99 66.39 34.19 I The total design workstation - including expanded instnmentation, breadboard and power supply. ' Ideal lor analog, digital and micro- processor circuits I 8 logic probe CircuJlS ' Function gonerntor with continuously variable st^e, square, triangle wave forms, plus TTL pulses I Triple pov^er supply Offers fixed 5 VDC supply plus 2 variable outputs - +5 - 15 VDC and -5 - 15 VOC ' 8 TTL compatibiB LED indicators, switches ^ Putsors I Potentiometers ' Audio eKpcrlmenlatJon apoaker i Multiple features in one complete test instrument saves hundreds of dollars needed for individual units ' Unlimited lifetime guarantee on bread- board sockets I Fijfed DC Dutpul ♦5 VDC <^ 1,0 amp, rpplo - 5 mV I Variabte dC outpiit ■I 5 - ID <'1 5 VDC 0.5 amp, npple - 5mV DESCFtrPTIOM pa 503 t-9 t&-24 25* 299.99 284,99 25549 IDC BENCH ASSEMBLY PRESS The PanaviM T.'* Ion manual !DC bencn 3ss.em:bl^ iaiion ioQi (ie^igned lor iqw volume, mai-s icrfriinraliDn ot vujiouJ fDC co^n(^cl^Sfs on nut • Assembly base & s!antfm"d plate-n InctLtd^d • Baw plalo piiiTBri may De rotal^Jd 90^ for maKimiim ^riel quickly changed wilTiout any looii leqij^iKl • Additional iicce55niisli ot 3 tons ai^ a laser diocte, Ttie Ions system CDlljmalisg tli& diverg- ing I^Siir hi^hy ,ia mrad Tho rtBVcff&nt duality IS oifrrachon hniiitd. The no^usir^g circyrar and precisp^n manufacsuned measitring 1 1 0 nm m diSfi^Qler arid 2?.e fTitn Lof g. OaO sfip^t n>cliidc^j Ai With 9'\ s-pGCiJtl inry rle^TTn^, quah.EFt/ IS lifnilcii&d C'dnnpltitQf ^itri leads for connectiofi to a DC pawef supply Trcm 3 IQ S.2S V. ThDjgn prg^acl to produce a paralLel ^ni. th£ TOCdl \^rt^\h can fca£Fi2y tie adiusliHl to focus ^ts^m lo A 4pol. Sturdy. sRiail and sell-con^ ta;n&d. the LOMU^ & precision device ctes^^nod for a wide range of n^pplicaliotis C'^" s ^ Jong 10-34 7^ STDCKt DCSCRtPTtON l<1 1D^4 STOCK v DESCRIPTX^N PV505 PartffkjsiJ Bwreft /la^errjoy PrfrM 145.49 Sflias;? frrfra-Rsia ColSmatof Poft ^9,99 COLUMATING LENS DUAL MODE LASER POINTER Triif ecriical calnnabng; ions IiS^mbly cdn$j^ts of » Mack snoii\zo lens a$s^- biy, adtusl benni to dos^n^ct foctrt. iticn lei wiin admsivo 47. 4^ J2.74 I iDMia5-.5 _ -*L0M13S] LDM13!i-2 hhswsil:mlinet*3eip0ie\[eri3 0n-ly 't" f LOMI^^'^ in <;ific Qulputs wi4f ba SVtiiJabl^ si time ot order All tjntls are r!£?w. Eeated. and gusfanlfHsd ti? funtlian a| mantjlac:Eijirar$ specirlic*ti» i.¥-ii ei(^ Si^* 1 i,-^ N ai'i fir GZ741 SI. MUSIC MODULE rrEiJkit rr-'M* ^"j* 4 9'Mr/>g Cord l5b"v jHTftf Th«* in wiftfl rM c«y * ti^M^ \t« «ad^ Ivm hWltKl Th9 rnjiic C art bijwy haa* |l ffT * imdl ■PCitiaMT 01pBryh 461-7 J&l FWt OflD£RS (£02) 4SI M9S CIRCLE 1B1 ON FREE INFORMATION CARD Cable TV Descrambler Kits Universal Kit $55.00 Incluaes al. pans and PC Board. Not includud Tri-Mode Kit S39.00 lntlud«$ all pnrts, PC Board and AC Adaptor. Mot Included IS me ^noionjte SB'3 Kit S29.00 Includes all parts. PC Boaid and AC Adapt or. ^(ot inclydtd is the enolo^re. Universal Tutorial ...-..-SS.SS inE;:iLrdes an in deptn study ol tne techonaiogy uteo and nas tfouthJ^^nooiing hints. Tri-Mode Tutorial,, ,S9,95 includes a gate by gate siudy of the circuit itr.d trouoiasnootin^; hints- Snooper Stopper ...„S39.00 Protect ycursA^f from ce$£rartiDi«r ovlection and Eiop tne 'tJuti*t'. Call Toll Free 1-800-258-1134 CCD. M & G Electronics, Inc. 301 Westminister Street Providence, Rl. 02903 ADVERTISING INDEX Electronics Now does not assume any responsibility for errors that may appear in the index below. Free Information Number 75 107 ISO 98 109 176 127 ISI 121 182 186 114 191 179 195 87 53 95 117 IHS 192 m 56 196 Page AMC Sales 25 Ace Producls 29 All Electronics ,95 Amazing Concepts 94 American Reliance Inc 29 Bcckman Induslrial, CV4 C & S Sales 7 CIE , , a CLAGGK, Inc .13 Cable Warehouse .26 Cablelronics 96 Chenesko IVodiicis 29 Cnrnniand ProduclJons 31 Deco Induslrie-S 29 ElecEronic Goldmine . , * . * , * . - . 98 Electronics Book Club ...... 3, S2 Fluke Manufacturing CV2 Goldslar I*recision. 21 Grantham College, .75 HighText Publications, Ini^ 94 ISCET.......... ,77 Interacthie Image Ttech 15 Jameco. , , .92. 93 Kelvin 5 Lake Sylvan Sales, Inc 9Q M&G Electronics , ... 98 MCM Electronics 91 MD Electronics . . ........ 90 Mark V. Electronics 88 Mouser 79 NESDA 26 NRl Schools 16 Natn Paris & Service 29 Northeast Electronics 31 Optoelectronics CV3 Paris Express 89 Sea Jay Development , , 86 Star CircuiU 29 187 TEC! 78 178 Tech Spray 22 — The SPEC-COM Journal 79 177 The School OT VCR itepair .... 25 197 Unicom.. .97 190 U,S. Cable .20 194 Viejo Publications 77 183 WIT IHiblications , . , 78 193 Weatherport. 31 184 Xandi Electronics 29 189 Zentek Corp. 20 ADVERTISING SALES OFFtCS Gemsback Publications, Inc. 5O0'B Bi County Blvd. Farmingdaie, NY 1t735 1-[5t6) 293-3000 Pr&Siident: Larry Steckler For Advertising ONLY 516-293 3000 Fax 1 516-293'3115 Larry Stickler publisher ChriBtiita Estrada assistant to the President Aril no Fishman advert f sing director Denise Haven advertising dssistaint Kelly McQuade credit manager Subscriber Coslorner Service 1-800-288-0052 Order Entry for New Subscrtbers 1-800-999- 7 139 7^00 AM - 6:(K) PM IVl-F MST SALES OFFICES EAST/SOUTHEAST Stanley Levitan, Eastern Safes Manager Electronics Now \ Overlook Ave. Great Neck NY 11021 1-516-4B7-9357, 1-510-293-3000 Fait 1-516-487-8402 MtDWEST/TeKas/Arkansas/Okla. Ralph Bergen t Midwest Safes Manager Electronics Novv One Northfi«ld PEaza. Suite 300 Northfidd. IL 60093-1214 1-708-446-1444 Fax 1 -70S 559-0562 PACIFIC COAST/ Mountain Stato^ Marvin Green, Pacific Sales Manager Electron ECS Now 5430 Van Nuys Blvd. Suite 3^6 Van Nuys.CA 91401 1-818-986-2001 Fax 1-81S'9B6'2DD9 EN Shopper Joe Sherei Natifsnal Repinesentative P.O. Box 169 Idyllwild; CA 02549 I -7 14-65 9-9743 Fax 1-714^659 2469 CinCLE 195 QN FREE INFORMATION CARD You want a bargraph & a full range counter - Pptoelectronics can deliver! BLEMO Now for a limited time only, S160. off the list price, for our Full Range Model 2810 with bargraph - plus: • Full range -10Hz to 3GHz. ' LCD display (daylight visibility). • True state-of-the-art technology with the high speed ASIC. • NiCads & Charger included. • Ultra-high sensitivity. • 4 fast gate times, • Extruded metal case. Compatible with MFJ207. Suggested options TAlOOSr Teiescoping Whip Antenna,-. ......S T2. CC30 Vinyl Carry Case.. $ 15, BL28: EL Backlight tor use in room light and low light..... , ...S 45. TCXO 30: Precision ±0.2ppm 20 to 40X temp, compensated lime base $100. Universal Handi-Counter'" Model 3000. S375. and Bench Model 8030. S579. Both offer frequency, period, ratio and time interval. Call for free catalog - Factory Direct Order Line: FL (305)771-2050 • FAX (305)771-2052 5821 NE 14th Ave. • Ft. Lauderdale, FL 33334 5% Ship/Handfmg (Max. SIO) U.S. & Canada. 15% outside continental U.S.A. Visa and Master Card accepted, aRCLE 180 ON Uf FORMATION CAR& The DMM our customers designed. reaJtiW fiefore we built ihe ne^' genenaiion Beckman IndListriai Series 2000 DMMs, we asked people like you what you really wmL You \^ am more. More test and measurement capabilities. More troubleshooting features. All in an affordable hand-held DMM. Ilie Series 2000 feamres the widest range Ireqiiency Counter in any professional DMM, a fuli-ninge Capacitance Mel en True- RMS measurements. Intermittent Detection, 50ns l\ilse Detection, and Peak Measurement tapabiiities, Pius, the Series 2000 is the only meter to offer autoranging MinMax recording and relaii\ e [ockIcs. You want a DMM tiial s easier to use. The Series 20()0"s display is l^h larger, with bigger digits and backlighting for easier reading, c^'en in the worst liglit. Pius the fast 4 digit display pm\ ides the liigli i^esokilion needed! for adjusting power supplies and gen^erators down to ImV. And only the Series 2000 features a menuing system for fast, simple feature acce^ss. Made m Ihe USA The Beckman Industrial Series 2000. priced from S209 to S279 offers you the best per for- inance for your dollar, Ixjok agjiin at these fc^atures: • \ Digit. 10,000 Count Resolution • Basic Accuracy to O.P/b • Tme IIMS, AC or AC on DC • O^OlQ Resolution • Automatic Reading Hold • 1ms Peak Hold • Fully Aiaoranging Relative and Min Max Modes • inierniittent Detector • 1X1244, lEClO 10 Design • Tliree Year \Xamtnty Hie Seiies 2000 offers the most solutions for your every day test and measurement needs. The only DMMs designed by the people who use them You. For more inforiiiation on these new DMMs call (outside CA) 1-800-854-2708 or (inside CA) 1 -800-227-978 1 , Beckman M Industrial Corporation. 38B3 Ruffin Rd., KM m San Diego, CA 921 23-1898. " ■ ' Beckman Indlumtriaf An Aifihate of Emerson Electric Co. CIRCLE 9B ON FREE INF0RMAT10K CARD Ispedfracions sutifect lo change witjKJut notice, C ^992 tkckman In^j^am Corp.