BUILD YOUR OWN HANOI-TALKIE! Build this liigh-efficiency HANOI-TALKIE for business or amateui communications ^ Build our — REFLEX TESTER and find out just ^ how fast you are! ^ How to use the IB 555 TIMER CHIP 1 to build oscillator circuits Build a 250-WATT POWER INVERTER to supply 120 volts AC from 12 volts DC! Use our ^ PC-BASED TEST BENCH ^ to identify and test ^ digital IC's CombtnBd with est $3.75 CAN i ' Bectroaics FLUKE AKD THILtrS - THE GLOBAI ALLIANCE IH TEST & MEASUREMENT FLUKI PHIUPS PHILIPS I Introducing SCOPEMETEK. There's More Than One Reason to Reach for It. Ill (acl there's evety reason to reach lor ScopeMeter/ Becaose only ScopeMeler combines the expertise of Fluke and Philips to bring you a dual-channel digital scope along with everything youVe come to expect from Fluke digital multimeters. The result: an integrated scope-and-multimeter that lets you see a waveform and digital meter display at the same time from the same input. Or switch betv/een dedicated high-performance Scope and Meter functions with the touch of a key. That makes it faster and easier than ever to capture, store and analyze precisely what you're looking for. At a prme Ifral looks good. too. To get your hands on a ScopeMeler, contact your Fluke sales office or your nearest Ruke dtstnbutor For more product information, cafi 1-800-44-FlUKE SCOPEMETER* Now there's only one to reach for. Simply Easy. • Intuitive front panel layout for simple, slfaiflhtforv/ard operation, • Pop-up menus and five function keys for easy conUol- • Autos et automatically sets voltage, time and tngger functions. « Saleiy^Sjgned BHC connectors and probes simplify ftaating Built toTake It. • Completely sealed against water, dusl and contaminants, • Ef^l protected and measures up to 600 volts rms • Rugged construction with shock' reststanl holster » Thfee-v-ear warranty Goes Wherever You Go. • Runs on rechargea&le PJiCad Batteries slandard C-celEs otthe included line voltage adapter "battery charger • Ad|ustaii?t tih-stanlTianger • COfnpatibfe if/ith a wide range of Buke mu^i meter accessories. CIRCLE 121 ON FREE INFORMATION CARD W i October 1992 ^^^^ m. 63 No 10 35 HANOI TALKIE Use this efficient mini FM transceiver for business or amateur communtcattons. Doti Wray 43 REFLEX TIMER Find out just how fast your reflexes are! Dan Kennedy 61 DIFFERENTIAL PROBE Make safe measurements in ungrounded systems. Walter Dorfman 47 PC-BASED TEST BENCH Build the TtOOa digital logic fC tester. Steve Wolfe 75 250-WATT POWER INVERTER Use it to power small appliances from your car James Melton TECHNOLOGY 55 NOT WORKING TO NETWORKING Case histories of some problem LAN's. Gary McClellan 69 THE 555: A VERSATILE OSCILLATOR Learn to use the 555 IC in circuits that waiL warble, and honk! Ray M. Marston 7d HARDWARE HACKER Histograph equalization. Don Lancaster 88 DRAWING BOARD Video scrambling. Robert Gross blatt 97 COMPUTER CONNECTIONS Miniature multimedia. Jeff Holtxman 8 VIDEO NEWS What's new in this fast- changing field. David Lachenbrucli 16 EQUIPMENT REPORT Computer monitor checker 78 AUDIO UPDATE Syndicated reviewers, AM stereo, and consumer fraud. Larry Klein 84JtLp THIS REFLEX TIMER PAGE 43 250 WATT POWER INVERTER J ■ PAGE 75 105 Advertising and Sales Offices 1 06 Advertising index 97 Buyer's Market 4 Editorial 14 Letters 32 New Lit 22 New Products 12 Q&A 6 What's News Whether you need a handheld transceiver for business or for ama- teur-radio — or just want to build one for the fun of it — ou r Handi-Talkie has a lot to recommend it. The small, tight-weight transceiver is powerful and efficient, offers narrow-band FM modulation and can be designed to operate anywhere from 27 to 32 MHz — and even up to 60 MHz with minor parts changes! That config- uration allows the Handi-Talkie to work both the six- and ten-meter amateur-radio bands. Thanks to the use of surface mount technology, the whole devicei including a re- chargeable nickel-cadmium battery pack, is housed in a case less than six inches long. Turn to page 35 for all the details? COMING NEXT MONTH THE NOVEMBER ISSUE GOES ON SALE OCTOBER 6. PHOTO SOUND STROBE This project brings the worlds of electron tcs and photography together to capture exciting, astounding images on film. SOLAR EVENT MONITOR Keep track of magnetic-field anomalies that can disrupt hance — communications. en- CIRCUIT COOKBOOK A variety of astable- and monostable multivibrator circuits based on the 555 timer. AUTOMOTIVE POWER RELAY This "smart" switch is perfect for controlling such high-current devices as auxiliary lights and high-power audio amplifiers. As » tQAiic« 10 Fead#rf. ELECTHONICS NOW pybli^Hes avithbfv plana or inifofni»tiDn rvUting to npwjA&fthy ptoducli. trd^nkiLwa and i^iAntific vid 1ftClu^o4oBiC4ij dfvelop'rients. BecjsiutF of posA^blfl vartanci^i tn tha quiihty and CDndtliort cA nfttfult ind worlunanship utvi by readsrs. ELECTRONICS NC^ di$daim« «ny rfMponsib^lity for tha %Af« and pnpmr hmettonino r*ad4r-buil1 pitii^ctt bas«d upon or from plans ckf infarmatKin pubUahaif m liNit maganna. Or f*lbig of any audh SbK« aoim of tha eqyipfnvnt i^d cirQ*try 4»Cftl»d in a£CTRON(CS NON may »«t*ia to or QICTOQNICS WOWifactaiWtBatTy tabth%lafllw i j Ai n o^ •quipiTWst Of cifCMitry, ^wggaali. ihat affyona intomtad n imth pro^Mtt carmA a jpafemt ~ ELfCmONlCS t*€M. aSSH 0033-75621 Octchber 19^2 Piiblr^d manlhty bv(l«rn«b*di Ribbattom. Inc , SOO^B B* County Soul»vard, FBrminQd^le. NY 1l735i S«<^n iJ -Oil A£s Pomgs p^id ai Farmii^jdata, NV and adtfiitionaJ nvviUrvg olficei Second- CiMt% jnud rtoiil/atton No Rl2Si€£L20O. «LithDri;«d at TcN^to. C*n»di. Om^ytv tubKripbon rata U S A acvd poftM»ions S19 07. C*n^ $7779 fmclcjd*« GST CanAd.an Good& ^d Safvicai Tut RaQivtrabon 1^ Rt2S1&S7S0). $rt oth*t covniH»« $28,97, A7I ibibacriptiofi ordan pAyable in LI.S A. tundi on\iiis«. Bectroms NOW. Hugo C«msba€k 1 1 604- 1 9673 foumtef Larry St«ckl«r, EHE CET. odftor-in- chief and publisher EOlTORtAL DEPAmiMENT Brian C. Fenton, i^ditor M«rc Spiwattp associate editor N^H Sclater» associate editor Tart Sf^dutOt assistant editor Jflffrsy Holtzman computer editor Rob«rt GrossblJittt circuits editor Lurry Klein, audio editor David Lachenbnjch conthbutin'g editor Don Lancaster contributing editor Katliy Tflranzii editorial assistant JUTT DEPARTMENT Andre Duzant» art director Injcie Leo* illustrator Rus»«tl C* Truelsoni illustrator PftOOUCTION DEPARTM£ffT Ruby M. Vh* prDductton director Karen 5. 8rown advertising |>roduction Marcel la Amoroso produ ctio n n^tstant Lisa Rachowftx editorial product! ori CIRCULATiON OEPARTIMENT Jacquellno P* Chaoseboro circulation director Wandy Alanko circulation analyst Thar*sa Lombardo circulation assistant MIcHela TorHtlo reprint bookstore Typography by hAates Graphics Cover photo by Oivoretfied PhvtO Services Electronics How fs indexed In Applied Schnc9 d Techoofogy index, and Hoadmrs Guida to P^riodic^ Utvr- Ature^ Acmdemie Abstracti, and MugjLfrVte ArUcfe SwnmAti^. Microftlm & Microfiche editions ere available. Contact circulation depart* mem for details, Advertisfng Sales Offices Us led an page 102. Elftctronica Now Executive and Administrative OfTtcos Subs^Rier Customer Service: 1-800-288^52. Order Entry for Mew Subscribers: 1,800-909^7139. Audit Sure^u of Cl^culatlons JUIember HOME-WORK For Electronics V5> Cuslom Molded CanyiDg Csso !(^ into bfiefCBse size Cmpar^t for text txxjf^ nmuals and/or wire jumper kit (optkmli LagsBrntlbomtsm hoik 24fDsZ500S$pm Fwctkm Ceneratof u.slne, sduare, trmgla.,plus TTi mro-mu^ 4000 Tm BNC Corinectofs for oscilfoscopes and counlers Triple Pom Supply... i-SV fixed, plustmvanBbfe5-15V 8TJlLo0cPtobeMcms Here's PB'503-C, It has every feature that our famous PB-503 offers, but we added one more, portability. Work on your projects at the office or school, take it home at night... it's for the engineer or student who wish to take their lab with them. Instrumentation, including a function generator with continuously variable sine, square, triangle wave forms and TTL pulses. Breadboards with 8 logic probe circuits. And a Triple Jim9 FOR MORE INFORMATION GLOBAL U^^Smi^^ 028 SPECIALTIES^ Power Supply with fixed 5VDC, plus two variable outputs (+5 to +15VDC). Throw'in 8 TTL compatible LED indicators, switches, pulsers, potentiometers, audio experimentation speaker... plus a life-time guarantee on all breadboarding sockets! And, because it's portable you will always have everything you need right in front of you! PB-503-C, one super test station for under S350! Order yours today!! Qll««lSpto«b«s^7DMb^Tt^1Kl•.HtttHmn,CT0eS1^ ^ CIRCLE IB2 ON FREE INFORMATION CARD NOW'S THE TIME Now, according to Webster*s New World Dictionary, means "at the present time; at this moment." Electronics Now is just what its name implies: a compilation of what is happening in electronics at this moment! Electronics Now brings you the latest news, the newest products, the most useful training, the most exciting projects, the newest how-to information. We help you learn how it works, how to keep it working, and, of course, how to make your own. We even show you what may happen tomorrow. Above all else, we remain your electronics magazine. We know that the great majority (89%) of you earn your living in electronics. But you are the engineers and technicians to whom being an electronics professional is more than just a job. In your spare time — your leisure time — your personal time— you still want to know and learn more about electronics. You want to know how Caller ID works. You want to know how digital audio tape compares to digital compact cassettes. You need to know about cellular telephone services and the personal communication networks of tomorrow. You need to know what microprocessor your next computer will have. You have to know what the next generation ICs will be like. Bringing you information on those and other subjects is our forte. We work and strive to stay on top, to learn, to explore, and follow late-breaking developments in electronics. And we do it now! That's where our new name — Electronics Now— comes from. That's what we bring to you — today and tomorrow — Electronics Now! Stay with us as we evolve and grow to meet the ever growing challenge of the electronics revolution. Stay with us as we continue our quest for the most exciting, most revolutionary, and most daring developments of today and tomorrow. Become, through our pages, a part of the most important and influential segment of our modern world- Come with us as we become Electronics Now. Larry Steckler. EHF/CET Editor-in-Chief and Publisher £ Standard $10095 High Performance GREAT iLALALEl. Standard Features - Models 100, 150, 200 & 400 ► AC a DC VOLTAGHS • DC CURREWT • RESISTANCE ft CONTINUITY TESTER ^ Buzzer • DiODE TEST •31/2 Digit LCD ft LOW BATTERY INDICATOR • ACCURACY 0.5% RDG KoMn Metm t»ck^ by a 2 Yr Wtrrtnty - P^hM & Ubor PRO 4001 too Basic lS0B3sic+ 200 Advanced BATTERY TEST TRANSISTOft W^E TRAI^ESTOR ftf^ BATTERY TEST KELVtH 150 Baslc-f KELVIN § 990007 100 Basic $19^5 Protective Cases For Models 100, 150. 200 ^M.^^^ i^sooaej Case For Model Pro 400 {9900M\ CAPACFTANCE ACDC CURRENT K£LVtM 200 AdvQficftd $3995 aDft*feFREQ COUNTER ACCC CURRENT CAPACfTANCE LOGCTEST TRANSISTOR HFE LEDTEST- VEniFYGOOOeAO KELVfH #990092 PRO 400 $6995 Standard Features - Models 92, 93, 94 & 95 • DC/AC VOITMETERS • AC/OC CURRENT • OHM METER • FREQUENCY COUNTER lo 4 l^z •AUDIBLE CONTINUITY TESTER | • DIODE TESTER • MAX/MIN AVERAGE MEMORY RECORD • RELATIVE MODE • 10A HIGH-ENERGY FUSE PROTECTION • DATA HOLD • AUTO SLEEP & AUTO POWER OFF PERFORMANCE ™ Uod»l92 i9»01O9 Ml Df AGNOSTIC^ Modal 93 #990110 $14995 EmiNE ANAL Y2ER Uodsl 9i # 990112 $19995 Compteto wilji above SttndMrd F4*titn» pkjs WATER RESISTANT |92 & &4 Modest onty), 2 YEAR WARRANTY. YELLOW HOLSTER, PROBES. BATTERY, FUSE, STAND Comp4dto wtin Sttrtdmtd A MotM 92 fwmlutw plus LOGIC PROBE, CAPACrTANCE TESTER, TRANSISTOR TESTER. TEMPERATURE I TESTER & K'TYPE PROBE, HIGH VOLTAGE | WARNING BUZZER Comploto with SttndAtd A Mod*! 92 FMtuna plus TEMPERATURE. TACHOMETER i DWELL ANGLE TESTER. DUTY CYCLE 10 MEGA OHM IMPEDANCE, ANALOG BAR GRAPH, K-TYPE TEMP PROBE. ALLIGATOR CUP TEST LEADS. INDUCTIVE PICKUP CUP 6* TEST LEADS & CARRY CASE The Ultimate Meter TRUE RMS - LOR - Hz - dBm t2 iNSmUMENTS IN ONE - DC VOLTMETER, AC VOLTMETER, OHMMETER, AC CURRENT, DC CURRENT, DIODE TESTER, AUDIBLE CONTINUITY TESTER, dBm, FREQ COUNTS CAPACITANCE METER, INDUCTANCE METER, LOGIC PROBE ocined in lEC^ 34B. Ul-1244ar eo card and others, get their basic clock speed from a single pin on the bus. The clock speed comes from the master oscillator on the mother- board, which is usually the one that's clocking the microprocesson For reasons buried deep in the corporate vaults at !BM. the bus clock was usually limited to a max- imum of 6 or 8 MHz — that was the speed of the last of the original AT s that had a standard bus. With the introduction of the PS/2 series of computers. IBM abandoned the old standard bus and began using the MicroChannel Bus— a different thing altogether That change left the compatible and clone manufacturers in a bit of a quandary since they no longer had a developing standard From IBM. The original AT had a t6-bjt bus because that was the internal bus size of the 80286 (the last microprocessor IBM used in the ATX IC's such as the 386 and 486 are 32-bit micro^ processors, but IBM's new 32 bit MicroChannel Bus was a proprietary bus. The result was a lack of an accepted standard for a 32'bit bus. With the exception of IBM, com- puter manufacturers have recently agreed on the EISA (Extended In- dustry Standard Architecture) 32- bit bus that has shown up in a lot of newer PC-compatibles, The gene- sis of the local bus is similar. While some cards that plug into the slots at the back of the mother- board have to run at speeds slower than the microprocessor, a few others are perfectly happy to run at microprocessor speeds. A good ex- ample of this is the video adapter, which can easily be designed to run Si The dirtiest part of your ^ Clean Without CFCs or 1,1 J-Trichloroethane With New HCFC Blend Tech Spray has d eve toped ^ fasUtcting and highly effeclive cleaner catled Envi-Ro-Tech'" 1677(1677) that uses a formulation of HCFCs and other non*CFC chemicals. This extremely pure product i^ non-corroiive, making it safe fof use on most electronic equipment. Invi-Ro-Tech 1677 ti effective in removing oiis, greases^ dirt^ silicone, fluxes and similar sotls. Although Envi-Ro-Tfch 1677 has unrversal deaning power, its tow surface tension ma^ei it ideal for precision and miaoKOpic cteamng. For a sample of this, or any Tech Spray deajitr, deffu^er, duster or freeze spray, contact our Technical Assistance Department toll free at 1 -800858*4043. Enyt'Ro- Tech ^''* 1 677 {1677} Y Use Envi-Ro-Tech™ Precision Duster^" For Pure Cleaning with No CFCs To remove parlfdes from sensitive equipment with out harmful solvents, use Tech Spray's CFC-free Envi-Ro-Teth''" Predslon Duster'^ Envi-Ro-Tech Preie Precision Duster Kit (1668-OfK) comes With a Chrome Trigger Sprayer 22 for predse dusting. The Chrome Trigger Sprayer is a conveiiient and safe attachment thiai can be removed and replaced without Joss of producL Tech Spray s3so offers a totally new dusting gas formulated v^th HFCs, Envi-Ro-Tedi'^ Duster 1671(1671), which has an ozone depletion potential of zero. For a sample of Envi-Ro-Tech Predsion Duster (1 668-OfS), contact our Technical Assistance Department toll free at 1-800'8S8-4043. 12; CIRCLE tTT ON FREE INFORMATION CARD at speeds higher than those avail- able with the standard bus cfocks. Along with the adoption of the EISA bus. the local bus (S a system m which a separate bus is provided for certain peripheral cards that don*t have to be limiEed to standard bus-clock speeds. The result is much faster operation, and for something such as video, the dif- ference is astounding. Deciding tf something is worth spending money on is a persona! decision, so I won't answer that part of your question. However, because this is a recent development, man- ufacturers are just starting to pn3- duce iocal-bus peripherals so you might want to wait and see what develops over the next few months and whether a standard takes hold. AUDIO CROSSTALK I've been getting a lot of crosstalk between audio chan- nels and, after eliminating every other possibility, Tve come to the conclusion that the signals are leaking through the power supply. There doesn^t seem to be anything on the circuit boards to take care of the prob- lem so I guess I'll have to do it myself. Could you tell me what the basic circuit setup is for power-suppiy decoupling?— A. MacDonnell, Mill Hill, NY If you re sune that the power sup- ply is the source of your problem, and it turns out that you're right, you can consider yourself lucky be- cause it's easy to take care of. The basic design for power-sup- ply decoupling is shown in Fig. 2 and. as you can see. there isn't much to it. You can get a lot more involved when you're dealing with very high frequencies* but because you're only concenried with audio Stuff, the layout in Fig, 2 wilf be fine. The resistor values should be cal- culated by looking at the maximum current draw of the equipment and applying Ohm's taw. Remember that the resistors will be carrying all the current needed by the circuit, so you should pay pnDper attention to their wattage as well. In general, as long as you're dealing only with line- level stuff, you can use quarter-watt FIG. 1— POWER-SUPPLY DECOUPLING CIRCUITRY, These circuits can gel a lot more complicated, but for audio fre- quencies, this Is more than enough. resistors and everything will be OK, Once you calculate the needed resistance (supply voltage/max- imum cument)* add another fifty per- cent to the value just to be on the safe side. Audio levels can vary all over the place, and if you*re listen- ing to something with a neally wide dynamic range, too low a value on the resistor wiH cause the signal to dtp. There's nothing magical about the choice of the capacitor value either, and Tve used everything from 10 to 100 |jlF without any noticeable dif- ference. You would think that the circuit vTOuld call for a non-polarized continued on page 15 job just got cleaner ^ Every Cleaning Task Made: Easier with New i Brushes, Swabs & Wipes i Whether you're tackling the dlrtiesl \ob, or cleaning a precision piece of equipment, Tech Spray has a cleaning prodLict that makes the task easte/, Tech Spray has expanded its line of brushes, swabs and wipes to cover the wide variety of cleaning and maintenance needs in Ihe electronic Industry. All TechBruihei'^ Tediswabs'" and Techclean'^ Wipes are precisely many faclu red undm Tech Spray's rigrd specifications, Tech Spray takes special care throughout the manufacturing process and in its packaging lo maximize cteanliaess and protection against electrostatic diKharge. For a sample of these, or any Tech Spray product, contact our Technical Assistance Department tolf Free at 1-800-858-4043, The makers of Blue Shower are bringing you a sophisticated itne of new formulations and accessories to make your cleaning and defluxing jobs easier. Tech Spray has expanded its proven line of cleaners and defluxers by adding the non-CFC Eavi-Ro-Tech^''' series, new products formulated wilh HCFCs, HFCs and other non-CFC chemicals- These innovative formulas have been engineered to ctean quickly and thoroughly, matching and in some cases surpassing the perfonnance of comparable CFObased products. In addition, Tech Spray has added to its line of brushes, swabs and wipes to accommodate the wide variety oi cleaning tasks found In the electronia service industry today. Ask for a sample of these or any Tech Spray product or a copy of Tech Spray's full-line catalog by contacting our Technical Assistance Department toll free at 1 800-858-4043. TECH SPRAY P.O. Box B4S Amarillo.TX 79105-0949 (806J 372^3 anCLE 177 ON fRE£ iMFOfUtATlON CAAO LETTERS Write to Letters, Electronics Nom 500-B Bi-County Blvd, Farmingdafe, NY 11735 Si o 8 I UJ 14 EQUIPMENT REPORT UPDATE Thank you for the wonderful Equipment Report on our Compu- Scope LITE IBM PC-based os- cilloscope (Electronics Now. August 1992). We wholeheartedly agree with you that "PC-based in- struments are the leading edge of growth for test and measurement " Gage has been a major contributor to the buildup of that industry for the past five years. In the same article, three valid criticisms were made by your re- viewer Because those points have also been raised by some of our customers around the world, we have been working to solve the problems. In July 1992 we released a new software package called GageScope for our complete line of CompuScope cards. First, we have drastically im- proved the hardware installatiorr procedure. We have rewritten the entire documentation and software supplied with the CompuScope LfTE card with special emphasis on installation. The 112-page manual has a 15-page section on board in- statiation, full of examples and charts on how to configure a new I/O address even if the user does not know hexadecimal mathe* ma tics. Second, to improve the descrip- tion of the menus in the manual, we included a detailed description of each menu entry, as well as a 13- page tutorial that guides the user through the most often-used menu commands. Finally, to satisfy the needs of more sophisticated customers, we offer other pn^ducts: CompuScope 220. a 40-MHz card with up to 8 megabytes of memory, and Com- puScope 250. which samples at 100 MHz. Our products are being used by major organizations such as NASA. IBM. Honeywell, and Motorola, and hundreds of smaller less well known companies and indi- vidual customers. We think that, overall, your review was very positive about the impor- tance of PC-based instruments in general, and CompuScope LITE in particular. We are very excited about our coverage in Electronics Now. MUNEEB KHALID Vice Pmsident Gage Applied Sciences Inc. Montreal Quebec, Canada SURFMAN DIODE REVERSAL An error appeared in our Surf- Man sound gernerator article CEIectrorttcs Now. August 199TX Diode D2 was incorrectly drawn reversed in the parts placement diagram, Fjg, 2 on page 35. However, it is drawn correctly in the schematic. Fig. 1 on page 34. IC SUBSTITUTION Mr Caristi is to be congratulated for his article "Digital Altimeter" CRadio- Electronics. May 1992X There is one point that concems me, however IC3 gives a full-scale reading for a 100- millivolt input change Cfrom 2.5 to 2.4 volts at pin 30), which is an effective sensitivity of 20 feet per milftvoll. My concern is the choice of the LM324 as ICl. While it is a very useful chip indeed, it does not exhibit low off-set drift with temperature. Prospective con- structors who think that shortcom- ing could be a problem might want to consider replacing the LM324 with four devices such as OP-07 s» which have impressively low drift. P.M. BRIDGEN Reading. Berks,, U.K. CLASSfC VrDEO AMPS RE-REVISITED I enjoyed seeing my article, "Classic Video Amps Revisited/* published in the June issue of Ra* dio-Electronics. Thanksl However, in the editing process some errors crept in. The first one occurs in the second paragraph on page 60. The wording implies that the 733 is the better choice for use in filters; thats not so. The 592 pro- vides the greatest attenuation of the unwanted signal. I tried to say that the the 592 will provide zero voltage gain with a high impedance across the gain control pins CGIA and GIB), the desired design objec- tive at those points for those sig- nals. In fact, the 733 would be a bad choice for this application because it provide a minimum 20-dB the- oretical gain for the unwanted input signals. Paragraph four implies that D1 through D4 are forward biased. Di- odes D1 and D2 are reversed biased and D3 and D4 are not biased at all or only forward biased when an overvoltage signal is applied to the circuit. That is necessary for input protection. Also on page 60. Fig. 7 shows SI with a shorting bar across the two wipers. That connection is incor- rect. There should only be an insu- lated mechanical connection. On page 61 . Q1 in Fig. 9 should be a f^NP device and it should be labeled 2N4959/2N3906 rather than 2N4959/2N3904. Also in Fig. 9. 03 should be a PNP device. Fig- ure 8 can be used to illustrate the proper configuration. Overall, the article fulfills its ob- jective of stating that both the 592 and 733 video amplifiers are still recommended for new designs. EDGARDO PEREZ R-E O&A conlimied from page 13 capacitor, but my experience is that polarized capacitors work just as well. Remember that you're not dealing with high current and volt- age levels here, and that gives you a considerable amount of leeway. LINE-LEVEL DIFFERENCE I've noticed that there s a con- siderable difference in the audio level that conies out of my CD, tuner, cassette player, and other equipment. When I switch my amplifier from one source to an- other I can often hear a dramatic difference in the levels. Is there some way to buffer those sig- nals between the equipment and the inputs to my power amp so the levels presented to the amp are all the same?— D. Gould, Michigan City, IN You can call them buffers, but as fares I can see, what you really need is a preamp on each line so you can adjust the level from each device before it gets to the power-amp in- puts. A lot of the consumer audio equipment on the market really cheaps out when it comes to the output level. The cassette and CD players on my sheli for example, are top of the line units, but neither of them has a convenient fft>nt panel control for adjusting the output level. There are really three ways you can handle this pmblem. The first, and easiest, ts simply to drop all the levels to that of the lowest one with simple resistor pads. Once you've done that, you can set the power- amp level and not have to change it every time you switch from one source to another. The second way to deal with this involves a bit more work, but is not really all that difficult. Although there s no front-panel control for the output level, you can bet your new pair of white tennis shoes that there's a trimmer somewhere inside each of the players that sets the output level. Just get yourself a screwdriver take the cover off, and start exploring. It's a good idea to have the service manual around when you do this, but most of the consumer audio stuff l*ve seen has the function of the trimmer silkscreened on the printed-arcuit board. The last approach to the problem is to build a bunch of preamps with line-level inputs and outputs. You can put them between the equip- ment and the power amp and adjust the levels that way. Td do that only as a last resort. It's a lot more work because you1l need two preamps for each piece of equipment (as- summg. of course, that you*re deal- ing with stereo). Besides the extra work. IVe never been convinced that it s a good thing to have more electronics on the line than the bare minimum required. That's because any extra electronics is a potential noise generator and also a potential entryway for externally produced noise. R-E •CRT RMdout *Dftlftyad Swfldip DIGITAL MULTIMETER ■ 6 rrac# / QM-90S5S DM 91 S3 9Pm TvOf OMtl *Mtfwl • LdqiC iMirt tL t^gs LCD Di^fmf 111 OM-633S DM 8135 DM T333 DM PMQUENCV COUNTER mWi Owek •Pft Owl DC POWER SUPPLV DM 7143 DM 62*3 ■ 4 T J O.gia mi t 2 O^n •CipKtiviQ* DifldL mifi LCD »rr«] , €0(Mtt vFificf Ififi intimt^on (y H» 30V 0.5A fj^as. iav 1.0A GoldStar ProcEsion Co.UcI no 13 EflfT leeth Sii*<*|.C*'Titov Ca 50701 USA €mCiJt m OH FflEE INFOfWATHM CARD 15 EQUIPMENT REPORTS The Checker Computer Monitor Tester Get a quick go/no-go indication of computer monitor operation. anCLE 10 ON FflCE IKFOFUIATTOfl CARD Computer monilors and Stan- dards have certainty changed dramatically in (he last decade. We've moved from composite video monitors through the MDA, CGA. HGC (Hercules). EGA. VGA, and SVGA standards. And there are yet other standards in use. and more in the wings. One thing that hasn^t changed, however, is that computers monitors even- tually need service. The Checker, a new product from Computer and Monitor Mainte- nance. Inc C6669 Peachtree Ind, Blvd. Suite B. Norcross, OA 30092) was designed with that in mind. Al- though The Checker is a rather sim- ple service tool, it can make things easier for any monitor repair techni- cian, or for anyone who manages or maintains computer equipment in an office environment. The Checker is packaged in a rec- tangular piasttc box that measures about 6 X 3 !6 X 1 Ya inches. The face of the unit has a single control that serves as the power switch as well as an output- mode controL Two vid- eo connectors, one a nine-pin and the other a fifteen- pin connector are provided on one edge of the device. The Checker can be powered by a standard 9-voft bat- tery for portable operation; a wali- adapter is also pre>vided to run the unit from the AC lines. The Checker pnDvides three out- SMALL DER 16 SmaU size to fit your pocket. Small price to fit your ptx:ketlxx)k, Laige functitiiMlity to fit your worL llic Rxkct Scries. A small wondci: Bl ;iRCL£ 193 OH FBEE INFOHAIATION CAliD U o Your Ticket To SlJCdilSS Over 28,000 technicians have gamed admit- tance worldwide as certified profesjfonals. Lei yotif ticket start opaninf doors for you. ISCET often Journeyman ceniftcation in Consumer Electronics, Indunriar^ Medical, Communications, Radar, Computer end Video. For more information, contact fhe International Society of Cartifted Electro- nid Techniciani, 2708 West Berry Street. Fort Worth, TX 76109; (317) 921-9101. Name Address_ City^ State -2ip. Send material about ISCET and becoming certified. S end one "Study Guide for the Associate Level GET Test/' £n- ^ closed is $10 ( inc. posiageK put modes: CGA Ccobr graphics adapter), EGA (enhanced graphics adapter) and VGA (video graphics array). On^ standard VGA resolu- tbn (640 X 480) is supported. Using the Checker ts slraighifor- ward: Turn the unit on. set the prop- er mode, and connect the monitor. In the CGA mode, you 11 see two sets of cofor bars: high-intensity on the top half of the screen, low-inten- sity on the bottom. In EGA mode, three sets of color bars are pre- sented. In VGA mode, the Checker generates a single set of eight color bars. Even though the Checker is rather simple, we can come up with many uses for rt. Around the Elec- tronics Now offices, for example, we could use it for quick checks of monitor problems. When someone reports a monitor problenn, the usu- al first check is to swap out the suspect monitor with one that is known to be good. (Of course if its the graphics card that is bad. then another swap is required.) That first step is basic, simple troubleshoot- ing to narrow down the problem. Unfortunately, that simple meth- od has its own problems. First is the lime and trouble to move heavy monitors around. Second is the lim- ited space that is available at the computer— there's usually not enough room to work conveniently The handheld Checker weighs less than a pound, and permits a monitor check to be done in just a minute or two. For afyone who maintains an in- ventory of computer monitors* the Checker could also come in handy. Is the monitor that is to be installed for that new employee workir^g? The Checker lets you find out beforByou haul a non-working monitor over to the installation site. The Checker also has a place in professional service shops. It can be used, for example, to "bum in" a monitor without tying up special test equipment or a computer (with, of course, the correct graphics card installed.) When a customer comes in to pick up his monitor, the Check- er makes an ideal way to demon- strate that the repair was suc- cessful and that the monitor is now working pn^perly. It can also be used as an aid in setting vertical and hori- zontal size controls correctly. The Checker does not support Hercules-type monochrome monitors. That's an unfortunate oversight in our opinion. Although such monitors are not popular sell- ers these days, there are an awful lot of older units in circulation, and older equipment is more likely to develop problems. We would also have preferred to see an SVGA (super VGA) mode and test pat- terns more useful than the non- standard color bars that are pro- vided. With a price of $229.95, the Checker is far too expensive for ca- sual use. Hov^^ver. the speed and ease writh which the Checker can provide a go/no-go indication would be welcome by anyone who spends a lot of time checking a lot of monitors. When you consider the amount of time that the device could potentially save, and the headaches it could help prevent, the Checker could prove to be a worthwhile pur- chase. R-E The World is Talking! Shortwave Listening Guidebook by Harry Helms re's viHir "uide 10 gelling ilie iiiosi from i\ sluuiwave radio! Jn clean nomcchnical l;jimiuijie. Hyny explains how. when, and u hcru lo iisien in, h% 320 heavtly-illustraled pageji are padced uith ad\1oe on: • antennas • selecting the right radio • accessories • reception techniques Leam how w hear the BBC Radio Moscow, ham operjiors, shipn, even spies und * "pirate* rmiio staiioas^ hiciudes huixlrcds of slation f vi\ \ ql- i k- i l- s and the i times you can hear them. | Only $ 1 6,95 ai radio egu inn ieni dealcni, I or order direct i rom HignText! Add $3 shinping (S4 Canada, $5 elscwliere). CA add sales tax. U.S. flinds onlv please. ■HighTaxt pti m I on ft Inc. 712K Miranw Ro^id, Suite I5L San DicgQ,CA 92121 riRCUE m OH FREE INFORMATION CARD No other trainini^ to troubleshooi computers Only NRI walks you through the step-by-step assembly of a powerful 386sx computer system you train with and keep— giving you the hands- on experience you need to work with, troubleshoot, and service today's most widely used computer systems. 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You start by assembling and testing your computer's 10 1 -key "imeliigcnt" ke\t>oard, move on to test the circuit n- of the main logic board, install the power supply and 1.2 meg htgh-density floppy disk drive, then interface your higli-resoluiion monitor. Whai s more, you now go on to install and test a powerful 40 meg IDE hard disk drive— today s most- wan ted computer periph- eral—included in vour course to DIAGNOSTIC HARDWARe AND SOFTWARE R A C f K pfuR in tlu^o^ic « 4nJ jmd (^uickTet'h mmu- I ]tf3-X, |Ei>T viju lumLvdri fxprricluc with r(idiay'> DISCOVERY LAB t umpEcir hrTJilTxur'Lliiij; ki* yuu dr^jiui Mid nHHtify t'm:xiit>. Jujsni)^ ami rrpuir fjuU*^ LESSONS ( If-jr tlltiMTntrU ic\l% til I) Id iiHirundcrMjJidinj! 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NEW! 40 MEG HARD DfSK ORlVe instjll thb 4n meg IDE lunl ilbk drive ^itnuUv. fmr grrjtcr daia ^ufuj^c capatiiy 2nd dju 3;:crvs %pcril NEWl 386>i'20 MHz MINI TOWER COMFUTERl Fcaiurc* M Ht mm^x CPIJ. mci; ftAM. li4K ROM. 12 mcft hlplKtcmirji OoppI dak dm-« NRI gives you the confidence and ilie know-how to step into a fuII-iime, money-making career as an industr>^ technician « even start a computer service business of your own! No experience necessary., • NRI builds it in With NRI, you learn at your own pace in your own home. No classroom pressures, no night school, no need to quit your present job uniil you're ready to make your move. And all throughout your trainingt you have the full support of your personal NRI instructor and the NRI technical staff, always ready to answer your questions and give you help when- ever you need it, FREE catalog tells more. Send today! Send today for NRI s big, free catalog that describes even^ aspect of NRI s innovative computer training, as well as hands^n training in TVVvideo/audio servicing, telecommunications, industrial electron- ics, and other high-growth, high-tech career fields. If the coupon is missing, write to NRI School of Electronics, McGmw-Hill Continuing Education Center, 4401 Connecticut Avenue, NW, Washington, DC 2000H. lEtM rcfiistriTiJ tnitciTurk ut intcrrutjofu] JkiMnr«» ^Utlilnn Corp. cjitickTccli anti H-ACli H- are rtiMstcmJ [ladcnurkN nrUlin X, Inc. "Wcsi Ood^t U it nwinl^cr nf ilic !i^nux Group, compatible computers. You II use your Ultra-X QuickTcch diagnostic software to test the s>'Stem RAN! and such peripheral adapters as parallel printer ports, serial communications ports, video adapters, and floppy and hard disk drives. You 11 go on to use your R.A.C.E.R, diagnostic card, also from Ultra-X, to identify' individual defective RAM chips, locate interfacing problems, and pinpoint defective support chips. This ingenious diagnostic package is just one more way School of El&ctronics McGon-Hill ConiiniUng Edicatlon Center 4 iOl Comicciicut Avenue. NW Washington, DC 2CMM)B dicck one FR££ catalog onfy " MICROCOMPUTFJl SERVICING ^ TVy\''idct>/Audio Servicing [Z lodusthat EtectronJcs &. Robotics □ Telecommunications; n Basic Eicctronlcji for carteer cout^ck approved under Gt Bill ^ cht Lk fur deEaits □ Computer Prognniniing Q Security' Electro dies D Ekcironic Music Tcchnologv □ Desktop Publishing n Prograniniing in C++ with Windows Narnc (Incase piint) Age Address Ot>yStale/Zjp 3-102 id NEW PRODUCTS Use the Free Information Card for more details on these products. S % z c 2 I 22 LOGIC PROBE. Beckman In- dusthai's LP50 is an inex- pensive, small 50-MHz logic probe that can detect pulses as short as tO nanoseconds. The pen-siz- ed logic probe is intended for iroubleshoobng high- speed, microprocessor- conlrolled circuits and the detection of extrenriely fast pulses. According to Beck- man, the probe measures TTL DTL. and RTL logic levels at frequencies up to 50 MHz. The LP50 is powered from the circuit under test through an alligator clip that prwides a secure con- nection to circuit ground. The mmi'hook clips onto the circuit's positive volt- age points. When the probe tip is touched to the OIICILE 16 ON FREE INFORMATION CARD signal test point, the probe simultaneously lights an d LED and generates a tone to make it easy for the user to understand what is hap- pening at the test point. The LP50 logic probe is priced at $45 — Beckman Industrial Corporatiorr, 3883 Rutfin Road, San DiGgo, CA 92123-1898; Phone; 619'495-3218. GABLE TV SIGNAL'LEVEL METER. Leader Instru- ments Model 951 RF sig- naMevel meter is intended for broadcast and cable TV measurements. It features autO'Channel search to measure the store level data for up to 32 channels. The LED bargraph dispfay is arranged in groups of eight channels and it pro- vides readout of the se- lected channel in dBmV or other user-selectable engi- neering units. Autoranging is featured but manual ranging can be selected. The Model 951 also operates in the single- channel mode with a com- bination bargraph and dig- ital readout of leve! in selected engineering units. The meters operation can be programmed for video or sound-carrier levels of channels selected by the operator. < CIRCLE 17 ON FREE INFORMATION CARD Frequency data for the USA and other countnes are stored. Up to 32 chan- nel fBadings can be stored. DC and AC voltages on the cable can a!so be read. The portable instrument mea- s u re s 8 % X 4 % X 7 Vs- inches and it weighs 10!/2 pounds. Powered by D cells, it has an auto-off fea- ture that extends operating time. The Model 951 CATV/ TV signal level meter has a p rice of $ 1 695.— Leader In- strument Corporation. 380 Oser Avenue, Hauppauge. NY 11 788: Phone: 1-800-645-5104 or 516-231-6900 in New York. KEYBOARD-CONTROLLED POWER SUPPLIES. Kepcos DPS Series of keyboard- controlled power supplies provide 75 watts of DC power in four ranges from 0 to125 volts. Eachpower supply is controlled by a keypad that commands a built-in microprocessor to set voltage, current limit* range, over voltage protec- tion COVP). displays, and over-current protection- Remote talk-listen con- teol can be exercised with an RS'232C connection that can be addressed in Basic and most common computer languages. Key- pad slew controls permit continuous adjustment of voltage up and down for fine tuning while the output is enabled. Separate LED displays provide voltage and current readout. CIRCLE 1H ON FREE iNFORiMATION CARD DSP power supplies are priced at $429.— Kepco, Inc.. 131-38 Sanford Ave- nue. Rushing. NY 11352: Phone: 718*461-7000; Fax: 718-767^1102. MULTIFUNCTION OUTLET TESTER, Polytronics Sure- Test Pro Multifunction Out- let Tester is said to be able to pnDvide a higher level of assurance of power delsv* ery than conventional volt* age meters in situations where the power source is critical. The meter test for cur- rent capability by creating a 12-ampene load on the line. Applied in short intervals, the 12-annpere power draw can reveal the presence of a faulty circuit breaker or a sag in power delivery (greater than 5%) due to poor contacts or improper wiring. A MUST FOR OEMs AND MROs! THE NEW NTE PARTS CROSS REFERENCE AND TECH GUIDE IS MORE USEFUL THAN EVER! NTE's parts catalog just keeps getting better! Our new 1992^93 edition features: « Over a quarter of a millioo U.S.. Japanese and European devices cross-referenced to NTE's 3,500 quality replace- ment semiconductors — available off the shelf f ■ Easier to nead. thumb- through format ■ Divided sections Order your copy direct or through your local NTE distributor. For your nearest one, call NTE toll-free 1-800'631-1250 (including Canada) or {201} 748-5089. FAX: {201)748-6224. YES □ YES PLEASE SEND ME THE FOLLOWING NUMBER OF COPIES OF NTE^S 1992 CROSS REFERENCE: Copies @ S4.95 ea. Enclosed please find my check or money order forS ^ (US. funds only) □ ALSO SEND ME INFORMATION ABOUT mESmCKCmss - SOFTWARE! Name^ ^ ^ ^ I I NTE's fiew PC-based software alfows you access to the MTE cross reference of over 250,000 parts in about one second. Check ilie coupon boK to receive more tnformaliof*. Company . Aridrfss« Cfty- Slaia. .Zip. 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Enroll mc as a member «f ihc Elect runic?* Engineers* Book Cluh according to the terms outlined in this ad. If not satisllc^. I may return ihe books within VO days wtihout obligation an J my membership will be cancelled. A shipping^handling charge and sales lax will be added l525 ' CRT Readoui. Cursor Meas. $995 V-523 ■ Delayed Swoop $975 V'522 - Basic Modol S875 V-422 - 40MH2 S77S V'223 - ZOMHz delayed sweeps $695 V^222 - 20MH2 deluxe S625 HITACHI COMPACT SERIES 5COP£S OJtficy Ctr |V-tC£5). Swii pCff w KADfan^n^, Dt%td mpHp ajid Tnoper L^A UKig a &indi CHT.You dont laai ti4 LU(] vactnoss m tefms ol pn) workT wvHi w^amv on pairs t tabof. Marry accftuorlat awaj'.^ lor afl Htachu maoy oitwc fliw osdflofcopaa. 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Model LM-T $19.95 W£ WILL NOT BE UNDERSOLD UPS SHIPRNG: AB STATES 5'* IL RES 7 TAX (S3 min 510 mail OTHERS CALL C&S SALES INC, t245 ROSEWOOD, DEEflFIELD, tL G00I5 FAX: TOS-SSO-OOOS • (708} 541-0710 E3 15 DAY MONEY BACK GUARANTEE 2 YEAR WARRANTY WRITE FOR FREE CATALOG CIRCLE 109 ON HtEE INFORUATION CARD The latest in electronics is only a phone call away! 1-800-221-7774 In N.Y. or if busy call: 1-718-722-4750, Please mention co AIWA csD-sn P0RTA8U LCD RADW CASSETTE CD PLAYEft • Ptnmt fiwtaig swtccn ptut auto ixoo • ? & ) wlc i ctton iJwiOorapn?OQfnmio>e • AM wVde^FM srereo tuner ^ OofPrtoi AIWA NSX-330 50W/Ctl HH^ UIWI COMPONefT SY^TBI Wrm SURSOUKD SOUND • j^fjr^set Dncme eqiuuct • s^EBfHt ip«arum an^er < Dual auto revenc cat i w209.95 $<|ggd5 • Bmadasts ui^ to 9 ft * Autp revccM UffM iasi 2x sound fvstmt «vttti our Price SHARP t0*8400 EUCTRONK ORCANtZER *■ 256 XB mtniDry • Tvt^ewniCf ttvte nevooani • HKamfa«t4O0iar. byflintKrMn - iMiitii/wett i (f>¥ calendar • 3 i>rvon« OircctoriiH • ftutifieit Card turtcti^m prf ce ietaii «jm,95 y miES TO YOUR VIDEOS! 5ap«fimpos« picture UEie or DacvgfDuniEl» readout - ti runcoon tone mnoce • Auto togfc opentjorL Our price • Skfi auto scan < • 3 u lUif {JiangeaD • 2i«f»ir eagiflg ^autotfitvcom • 30 0^ no auto diai « Hanoset Auto xwtcn to taitc' mode tpMt^m STaods $11^ R£taci 9^ 39 9 CASIO BP100 BLOOD PmSUlTE ' liONfTDR WATCH • iMater reftitanc to so rneter • S muMHuhCdon ae^rrm • AMfnettc; Den tn meter ft Baromecer • COtfttdODA aiann iCAs^ Our Price JJTtH^KS INPUT lOvefSOO .j^ote/vioea input I^W » UJUfied W/va tcfl^te * QxnptJtiir CQutorrMmt * Mtfl stereo Equlpnwnt - wmfimJimngfrns^ . POTHtotty Personal AucBo - smaJt *«rtw ApfUlanc^ Set Sm * 6m, PiVC CMJC •eOtnaMStBeO • Uriiuiar pnones MaU Order E>ept: ^55 smith street, Brooklva NLY. 11231 EM 1092 Visit our superstores at 67 west 47th Street 115 west 45th street 1-212-921-1287 Sun i(M5£hS^G Moa-TFtuf^; ?J(H:O0. Fr/. 9:10-2:00, aosMSaturajv ii New wrk Landmark for over 26 yearst TDlMree Une ts open SUN. OWLY fr?, FRl. B-l i£tai Un« are open Suri lOS. DAilY 5306. FHl 93&2 ^ contVnenta USA AVAILABLE at 3' 34 BUILD THIS HANDI-TALKIE DON WRAY IP YOU EVER WANTED TO liUIUU A small powerful handheld Irans- cciver and, at the same Ume leam surface-mount technology (SMT), this is the project for you! The E'Comni frequency- modulated (FMJ transceiver is housed in a rugged yet attrac- tive aluminum case less than six inches long. It is one of the most unusual transmitter-re- ceivers ever designed for Us power level and operating fre- quency range. The case In- cludes a rechargeable nickel- cadmium power pack that will save you the cost of periodically replacing eight AA alkaline cells. The E-Comm receiver has a respectable 0,3-mlerovolt sen- sitivity (l2-dB SINADl for high quality reception, and its trans- mitter" boasts at least a 90% effi- ciency. E-Comm owes its effi- ciency to its innovative Ctass-E final am pi in er which exhibits high power gain. It offers a con- tinuous output of 3 watts rms into a 50-ohm antenna or dummy load. The efficient re- ceiver and the rechargeable power supply make it possible to keep E-Comm on the air in the squelch mode tor 80 liours without recharging the power pack. Intended for narrow-band FM. E'Comm has a usable car- rier frequency range of 27 MHz to 32 MHz with only crystal and alignmenl changes. The subject of this article is a version de- signed for 27, 145 -MHz opera- tion. With modilications to the transmit and receive filters (component value changes) op- eration up to 60 MHz is possi- ble. This allows the transceiver to work both the six- and ten- meter amateur radio bands. Note: This transceiver has not Build this efficient, miniature FtVI iiandiield transceiver and start your own private communications network. 1 r'-x R30 I Rt7 SFWSF LBI GfJO ICS MAxeii l\ lEDI fWDS SWITCH VRX VIX R6 Aim S1-3 L0W9ATTERY LED — HDh— D4 RX/TX SWITCH RXo ORX C30 l-SOpF CLASS £ AMPLIFIER Ca C3 56pF 47pF LiMfTfR tmrvER vix Q VT)« PIHS J2 ;? 11132 K^' 4.5.8 R20 100K FIG. 1— SCHEMATIC SHOWJNG THE MODULATOaTRIPLER, Ciass-E amplifier limiter, driver and lo w*voUage regu lator sections of the E-Gomm transceiver TTie key device fs ECl, the FM transmitter chip. 5il o 'c e 1 UJ 36 been submitted for FCC ap- provai, and its operation on cer- tain frequencies may not be allowed and/or may require li- censing. The top panel controls of E- Comm include an on-off switch. VOLUME and soltklcm knobs and an LED power-pack status indicator. The removable flexible seven-inch antenna is coupled to the transceiver with a 50-ohm bayonet^style BNC connector plug. All the compo- nents except the battery pack, microphone, and speaker are mounted on the double-sided PC board. Extensive use of Inte- grated circuits and surface- mounted components allows the circuitrv' to fit on a PC board that measures only 2.25 x 3. 1 inches. How it was designed The transceiver has three main sections: transmltten re- ceiver and power supply (Refer to Figs. 1 and 2, J The transmit- ter is designed around Motor- ola's MC2833, a low-power FM transmitter IC whose plnout and functional block diagram are given in Fig. 3. The receiver Is designed around Motorola's MC3363, a low-power, dual-con- version FM receiver IC whose pi- nout and block diagram are given In Fig. 4. Received signals picked up by the antenna are preselected by the five-pole transmit bandpass filter consisting of inductors L4, L7. and L5 and capacitors Cll, C2, and C30 as shown on the right side of Fig, 1, The received signal is then fed through the receive/transmit switch Sl-b to an impedance-matching stage consisting of CIO and L3 shown on the left side of Fig. 2, That stage provides an additional two poles of preselection. Diodes Dl and D2 prevent overloading and the possible de- struction of the RF amplifier transistor if It is subjected to overdriving at the front end. The preselected signal is then amplified by the 1C3 (MC3363) internal common-emitter RF amplifier stage and fed to the first mixer stage on pin 1. The RF amplifier provides a gain of approximately 20 dB, The first local oscillator (LO) takes a third overtone from a crystal, and drives the first mix- er through an internal cascode amplifier. Downconversion makes the first LO frequency (the first IF frequency) 10,7 MHz greater than the carrier. For ex- ample, if a 27.145 MHz carrier were present, the crystal fre- quency would be 27.145 MHz plus 10.7 MHz or 37.845 MHx. The mixer is a doubly bal- anced multiplier that provides about 18 dB of conversion gain. The output of the mixer is an emitter-follower stage with an output impedance of 330 ohms to match the ceramic fiiten Fil- 1ST iNPirt IKPUT mt VCAP ZOH 1ST LOTANK 1ST iQVm 1ST LO OUT 2NDL0 1STMIK BASE OUTPUT 2«IDIin QUTPUT oumn ZNDMX IHPUT LIMITER D£COUPU MUTE OUT LiMmn CHCOUPLE COMP OUTFUT MOlflOft COMF INPUT DfTICi REC AUOIO QUAD COIL MUTI (NPUT DtttwiuR FIG.2^SCHEMATIC SHOWING FM RECEIVER, audio filter, and audio amplifier sec- tions of the E-Comm transceiver. The key device here is IC3» Ihe duai-con version FM receiver chip. ler F2, a 10.7-MHz ceramic bandpass filler, removes un- wanted out-of-band harmonics from the ouipul of the first mix- en The second mLxer takes a sig- nal from the 10.245-MHz funda- mental mode crystal-controlled oscillator XTAL2 whose output Is mixed with the 10.7-MHz first IF to generate the 455'kHz sec- ond IF with a conversion gain of approximately 21 dB, The 455-KHz ceramic filler Fl (left side of 1C3 in Fig. 2) prt>- vides narrow-band filtering for Ihe limiter ampilfiers within TCI. the MC2833 FM transmit- ter chip. The limtters clip the 455-kHz second IF signal to re- move unwanted amplltude- modulaled signals and feed the audio detector A quadrature de- tector within ICS, the MC3363. detects the modulated signaL The parallel quadrature detec- tor tank, LIO. in the detector is tuned to 455 KHz. The demodulated (audio) sig- nal on pin 16 of the FM trans- mitter ICl is then filtered by an active filler stage that includes an op-amp within IC3* the FM receiv^er chip in Fig. 2. This ac- tive filter, connected at pins 15 and 19 of 1C3 and consisting of capacitors C13, C24. and C15 and resistors R21, R22, R23, and R15, has a rolloff at 3 kHz Squelch Is performed by the carrier-detect function on pin 13 of the FM transmitter chip. iCl in Fig. L Resistor RIO (be- tween pins 12 and 13) provides hysteresis in the squelch circuit to prevent unwanted "break through/' This squelch circuit is unusual; Its output both en- ables and disables iC4. a Motorola MC341I9D low-power audio amplifier with a chip dis* ABLE pin 1 (CD)* o O cr JO m S n Z o 37 VARIWLE REACTANCE RF OSC ^ ♦ Wf I BUFFER Aamp S4 IS PARTS LIST 15 14 10 m FIG. 3---PIN0UT AND FUNCTIONAL block diagram for IC1, the Matorota UC2BZZ tow-power FM transmitter chip. Power consumption is re- duced by disabling the audio amplifier when the receiver is squelched* and it is also kept low because U is run from the unregulated power supply In combination with the 32 -ohm speaker. This arrangement holds receiver consumption down to only 7 milliamperes from the battery pack when the receiver is in the squelch mode. The gain of the audio amplifier is set by resistor R29 (between pins 4 and 5) and nearby re- sistor R24, and is expressed as (2 X R29/R24). The transmitter Is a 3-watt narrow-band FM Class E circuit with efficiency greater than 90% /The front end of the trans- mitter is based on !C1 (Fig. I)* the low-power FM transmitter chip. The voice signal is picked up by the microphone and fed to thcMin AMPiNPirron pinS of ICL Resistor RU (between pins 4 and 5) sets the gain of the am- plifier, and the output of the am- plifier drives the FM modulator A variable reactance in the modulator '^bends' the frequen- cy of the crystal-controlled os- cillator. Because the crystal frequency cannot be deviated by more than a few kilohertzby the variable reactance circuit, a multiplication scheme derives the proper carrier and modula- tion frequencies. In the E- Reslstors (All 1206 SMD chip re- sistors are 1/8-watt, 5%, unless otherwise specif led) Rl— 47 ohms, 1/2-watt. 5%, radial- lead R2— 22 ohms. 1206, SMD ohms/1206, SMD R4— 220 ohms. 1206. SMD R5— 330 ohms. 1206. SMD R6^70 ohms. 1206. SMD R7— 1000 ohms, 1206, SMD R8, R9— 4700 ohms, 1206, SMD RIO— 4.7 megohms. 1206, SMD R11, R1 2— 22,000 ohms, 1206 SMD R13, R24— 10.000 ohms. 1206 SMD R14. Rl 5—47.000 ohms. 1206 SMD R16-R23— 100.000 ohms, 1206 SMD R25, R26— 100.00 Ohms potenti- ometer, Bourns 51CADD12A20. or equivalent Ra7— 330.000 Ohms. 1206 SMD R28— 390.000 ohms, 1206 SMD R29— 680,000 ohms. 1206 SMT R30— 510.000 ohms, 1206 SMT R31 — current variable resistor, poly- mer-based, Raychem Polyswttch RXE040 or equivalent Capacitors CI— 5 pF NPO 805 SMD ceramic, Tayio-Yuden UMK212CH0R5D- B or equivalent C2— 22 pF NPO ceramic disc. 100- volt, Panasonic ECC- F2A220JCE or equivalent 03. C4^7 pF NPO 805 SMD ce- ramic, Tayio-Yuden UMK- 212CG470K-B or equivalent C5— 56 pF NPO 805 SMD ceramic, Tayio-Yuden UMK212CG560K-B Of equivalent C6-C10— 68 pF NPO 805 SMD ca* ramie, Tayio-Yuden UMK- 212GG680K-B or equivalent C11— 82 pF NPO ceramic disc. 100- voll, Panasonic ECC- F2A820JCE or equivalent 012— 120 pF NPO 605 SMD ce^ ramie. Tayio-Yuden UMK- 212CGt21K-B or equivalent 013— 330 pF NPO 805 SMD ce- ramic, Tayio-Yuden UMK- 212CG331K-B Or equivalent Comm, a crystal frequency equal to one- third of the carrier frequency was chosen. Inductor L9 (In series with XTAL3 be- tween pins 1 and 16 of ICl ) cen- ters the oscillator frequency C14. C15— 470 pF NPO 805 SMD ceramic, Tayio-Yuden UMK- 212CG471K-B or equivalent CI 6. 026. 027— 0.01 M-F Y5V 805 SMD ceramic, Tayio-Yuden UMK212F103Z-B or equivalent C17-C23— 1000 pF NPO 805 SMD ceramic. Tayio-Yuden UMK212SL102K-B or equivalent C24— 1500 pF X7R 805 SMD ce- ramic, Tayio-Yuden UMK- 212B152K-B or equivalent 025, 029, 031^036— 0.1 jjlF Y5V 805 SMD ceramic, Tayio-Yuden UMl^12F104Z-B or equivalem C 28— designation not used C30—8-50 pF trimmer capacitor, Sprague-GM GKG50011 or equivalent C37-C40, 042. 043. 046— VP 1206 SMD tantalum. 16-voll 041 — designation not used C44— lO^F electrolytic, 16-volt, 5- mm, Panasonic ECE-AICGEIOO or equivaJent C45— lOOp-F electrolytic, 16-volt. 6.3 mm, Panasonic ECE- A1CGE101 or equivalent Semiconductors D1, D2— DL4148 switching diode. 1206 SMD, D3— DL4003 silicon rectifier, SMD D4— 1N4758A 56-volt Zener diode LED1— HLMP-1503-101 (Hewlett- Packard) green fight-emitting di- ode right-angle indicator or equivalent Q1, Q2~MPF6660 power FET, (Motorola) or equivalent 101— M02833 (Motorola) tow- power FM transmitter system. SMD 102— 74AOL11132 (Texas Inslru- menis) quad N AND gate, Schmitt trigger. SMD or equivalent IC3— MC3363DW (Motorola) low- power dual-conversion FM re- ceiver, SMD package 1C4--MC34119 (Motorola) low- power audio amplifier, SMD 105— MAX666CSA (Maxim) vott- age regufator. SMD package Inductors L1-L3--0.33 tLH, adjustable coil, Toko. 292KNAS-T10342 or equivalent when no modulation is applied. The buffered output of the os- cillator on RE' OUT! 'I ] r pin 14 then feeds a lank circuit made up of inductor LI and capacitor C8. which is tuned to the third har- PARTS LIST L4, L5— €.68 |iH, axiaMeaded in- ductor, Taiyo-Yuden, LAL04NAR58M or equivatent L6— 1.2 (aH SMD inductor, 2,5 x 3,2mm or ecjuivalent L7— 1.6 ^iH axial-leaded inductor, Taiyo-Yuden LAL04NA1R8M or equivalent L8— 2.7 axial-leaded inductor, Taiyo-Yuden LAL04NA2R7M or equivalent L9— 10 M-H adjustable mductor, Toko F292CNS-T1052Z or equiv- alent UO— quad coil. Toko 5SVLC- 0637eJT or equivalent Switches 51— OPOT pushbutton switch. (Schadow) F2U0A or equivalent 52— SPDT slide switch, C&K, 1101M2S3AQE2 or equivalent Connectors J1— 50-ohm BNC bayonet-style, PC- board-mount jack wUh two hex ring nuts J2— charging jack, Cui Stack PJ-002A or equivalent J3 to J5— sockets. 2-pin 2mm, Mo- fex 53014-0210 with three 2-pin plugs, 2mm. Molex 51004-0200 and six pins, Molex 50011-8100 or equivalent Crystals XTAL1— 37,845-MHz third-over- tone crystal. Toyocom, HC-49 or equivalent XTAL2— 10.245 MHz parallel- mode crystal, 32 pR Toyocom. HC-49 or equivalent XTAL3— 9.0483-MHz parallel- mode crystal. 32 pF, Toyocom, HG-49 or equivalent RItars F1 — 455-kHz ceramic filter, Murata OF UM455E or equivalent F2— lOJ'MHz ceramic filter, Toko SK107M5-AO-10 or equivalent Other Components MIC1— microphone, Panasonic WM-54BT or equivalent SPKR1— speaker, 2-inch square, 32-ohm, Regal, SA*200 or equiv- alent ANT1 — flexible coil antenna with BNC bayonet'Style plug. monlc or the oscillator. The signal Is multiplied by a factor or three to obtain the car- rier frequency in this tank cir- cuit. Both the carrier and the modulation stgna! are multi- Miscellaneous: PC board, custom-made battery pack with eight rechargeable nickel-cad- mium AA cells. No, 24 AWG wire: one 120-volt AC to 12-volt DC adapter for charging the power pack; custom-made extruded case with bottom panel and silk- screened top panel; one custom made speaker grill; two knobs. Keystone, 8580 or equivalent with two hex ring nuts each; tour No, 440 X 3/8-inch Philips-head screws, black: four No. 6-32 X Sn6-inch Philips-head screws, black; four No. 6-32 intemal*tooth lock washers, four No. 6-32 hex nuts, one perforated hole plug, Hayco 2637 or equivalent; six- inch length of shielded wire; 12- inch length of No.24 AWG wire; fine solder wire; tools and ac- cessories as specified in Ihe text. NOTE; The following parts are available from Micro Advance- ment Products^ Inc, RO, Box 8506, Hollywood, PL 33084 800-358-8545 • Printed circuit board only- Si 2.00 • Kh with printed circuit board and alt components — $97,00 • Enclosure including all hard- ware, microphone, speaker, knobs and transmit button — $38.00 • Battery pack— $17.95 • AC to DC adapter for charging power pack J wall outlet mount— S7.85 • Flexible ' rubber ducky*' seven-inch 27-MHz antenna with BNC bayonet-style plug — S17<95 • Complete kit for one E-Comm tra nscei ver— $1 68.00 • Complete kit for two E-Comm transceivers— 5297.00 • One E-Comm transceiver as- sembled and testetJ— S229.M Please add $4,95 for shipping and handling to all orders. Free frequency modification sheet and crystal list with each order. plied to obtain tlie 5-kHz devia- tion required by the receiver Next tlie signal is passed through a tuned common-emit- ter amplifier to amplify and smooth the carrier Next the signal is clipped by the quad nand Schmitt trigger, 1C2. a 74AC11132 high-speed CMOS logic gale. Two sections of 1C2 (IC2-b and IC2-c} provide drive to turn a parallel-con- nected pair of enhancement- Ill ode MPF6660 power MOSFETs. Ql and Q2, on and off. Class E operation is ob- tained with the fast switching as well as the low on resistance of the power MOSFETs. Theoretically, ifno power were required by the switch for ac- tivation (driver power K and if it were lossless, E-Comm would be nearly 100% efficient. Al- though the FETs do not form a perfect switch, they offer several useful characteristics: The in- put power required to drive the PET'S is veiy low (drawn prin- cipally in switching the gate in- put capacitance on and off at high speed (less than 6 nanose- conds), and their switching speed is very high. Those characteristics give the transmitter an efficiency of about 90%, measured as the ratio of rms RF power (delivered to the 50-ohm load) to the DC supply A five-pole filter matches FIG. 4— PINOUT AND FUNCTtONAL bloek diagram for the Motorola MC3363DW low-power, dual-conversion FM receiver chip. P 2 e 40 FIG. 5— PARTS PLACEMENT DIAGRAM tor Iho E-Comm transceiver. Nole radial lead-^ ed components C2, C11, R30 and F2, Axial leaded components R1» L4, L5, L7, LB and D4 are vertlcaily mounted. the output of the MOSFET switches to the antenna imped- ance while also filtering. Variable capacitor C30 fine tunes the output stage to match the antenna or dummy load. Notice that to obtain class E op- era t ion, lioth the load and the multiplier stages must be tuned In accordance with instruc- tions in the Calibration and Tlmeup section of this article. Mismatch and ov^erload protec- tion are provided by Zener clamp D4 (Fig.L between Ql and Q21 as well as the Poly- switch protective resistor R31 (Fig, 2, upper left) in the power supply. The low- volt age regulator shown in Fig, 1 includes a CMOS voltage regulator 1C5. a Maxim MAX666, which con- serv^es power and provides two features: low quiescent current ofabout 15 microamperes and a built-in low-battery detect func- tion. The regulated output is set by resistor R18 (pin 6) and R28 to be 6.4 volts. This voltage level was chosen to provide enough gate voltage lo switch powder MOSFETs Ql and Q2 on hard without exceeding the max- imum voltage specification of the quad nand gate IC2. The low-battery detect circuit Is set by resistors R17 and R30 at LBi pin 3 of IC5 to about 8 volts. Because the voltage reg- ulator is a CMOS device, high resistor ralues are placed in the feedback loops for further re- duction of power consumption. Pin 7 of 1C5 Luo has an open- drain output that drives the low-battery indicator LEDL The receive/transmit switch SI -a turns the receive and transmit sections of the trans- ceiver on and off for further power conservation. The power pack consists of eight AA nickel- cadmium rechargeable cells, each with a rating of L2 volts at 500 milliampere hours. The pack is charged through con- nector J2 (Fig, I, upper left) by a 120-voU AC to l2-volt unregu- lated DC adapter plugged into the AC line. Building the txansceiver Surface mount devices (SMD) were chosen for E-Comm be- cause they permit the con- struction of a miniature trans- ceiver, and their small compo- nent dimensions help to keep PC board traces short- There- fore, by building this trans- ceiver you 11 get a leg up on the whole process of surface-moun t technology (SMT) because you will gain iiands-on experience in picking and placing the mini- ature components and an awareness of both the benefhs and drawback to SMT However. do not attempt to construct this transceiver unless you are an accomplished project builder I^BJisceivcr assembly Many SMD coniponents are not marked with values or rat- ings because of the limited RG. e^UTAWAY VIEW OF ASSEMBLED E^omm TRANSCEIVER showing the pos*- lions of the controls and the iocations of the microphone, speaker, loaded circurt board and power pack. space on their cases. This means that you must be ex- tremely careful to avoid mixing up chip components before and during construction. Specialized tools should be used in picking and placing SMD components. They should be suitable for grasping smalL hard~to-handle parts. Recom- mended are stainless steel nee- dle-point curved-end jewelcr*s tweezers for picking and plac- ing small parts such as chip re- sistors, capacitors and diodes on the circuit board. Fine jew- elers pliers will be useful for straightening stub leads on sur- face-mount IC's. Do all soldering with a fine- tipped 10- to 15-watt pencil-type soldering iron. A lighted magni- fying glass will be helpfuK pref- erably one that mounts on the edge of a bench. Use only high- quality fine (0,01- to 0.02-inch) diameter solder wire and a suit- able liquid flux. Keep tine sol- der-removing braid on hand lo correct any mistakes that you might make. Anyone building E-Comm should be mentally prepared for the surprisingly small size of the SMD components and their close spacing. Working with SMD components calls for near professional quality soldering skills and a lot of patience. Set up for building E-Comm on a well lighted desk or bench and sit in a comfortable chair. Do not start this fine work unless you are rested and relaxed: mis- takes can be costly and frustrate ing to correct! Refer to the parts placement diagram. Fig. 5, Be sure to ob- serve all conventions when mounting polarized compo- nents such as diodes and capac- itors. Dots on the PC board denote polarity. Position all po- larized capacitors so the positive lead is nearest the dot, and position all diodes and rec- tifiers so their cathodes are nearest the dot. Be sure to find the markers indicating pin 1 on all SMD packages. It is typically a white dot. Do not attempt to build this circuit on any PC board except one that has been specifieaily designed for this circuit. Failure to observe this wiH result In a poor performing transceiver. A proper PC board for RF circuitry needs an adequate ground plane and short interconnects to prevent inadvertant oscilla- tions, loss of sensitivity and noise- related problems. The accurate and effective mounting of SMD components requires a solder mask on the PCB because of the cramped lead spacing, A double-sided board with plated-through holes and solder mask Is avail- able from the source given in the Parts List, It can be pur- chased as a single item or as part of the options listed. An orderly assembly pro- cedure is recommended be- cause of the cramped PC board layout and the mixture of small and large components on the board. Solder all surface-mount iCs to the board first. This is the most time-consuming and te- dious part of the project! WIRE SIDE of E-Comm transceiver circuit board In soldering SMD ICfe. first tin one of the comer pads on the PC board. Then* with needle-nose tweezers* grasp the part and center it so the Jeads align with all of the pads. Solder the corner lead to the pad that has been tinned. Next solder the pin diag- onally across from the first pin, making sure that the case is still centered on the pads. Before soldering the remaining pins, refer to Fig, 5 and verify that the IC is In the correct position: then double check to be sure that pin 1 is in the correct loca- tion. Be careful not to apply too much solder at each pad, and try to avoid making inadvertant bridges with the molten solder between Intended connections and adjacent pins. If bridging occurs, use a solder-removing braid and flux to remove it. Also avoid holding the soldering pencil at any connection point for more than the time requred to cause the molten solder to flow to prevent overheating the component. The next step is to position and solder all SMD chip capaci- tors and resistors. Install all re- sistors and capacitors of the same value at the same time to avoid mixing values I Tin one pad of two-terminal compo- nents, place the component in the correct position, and hold it with tweezers while soldering it to the tinned pad. Next, solder the other end. As in soldering the ICs, use only as much solder as is neces- sary to form a fillet between the component and the PC board pad. Be sure that the compo- nents are positioned flush against the board. After all SMD components are mounted, clean the entire PC board with flux removen and in* spect all of the soldered connec- tions with a magnifying glass. If all of the SMD soldering appears satisfactor>^, mount all of the leaded through-hole compo- nents with the exception of in- ductor L8 and solder them in position, (Inductor LB is to be installed after the multiplier stages are aligned,) l^ke care when soldering the connectors because their leads are off-centered. The axial-lead- ed inductors and resistor Rl are mounted through holes. Use the sllkscreened pattern on the PC board as a guide. Be sure to mount the switches and potcn- tiometers so they lie flush against the PC board. Now assemble the battery pack, microphone and speaker. Assemble the connector plugs for J3 to J5 by crimping and soldering them to the battery pack, microphone and speaker wires. Solder two six-inch lengths of insulated 26 AWG wire to the speaker and twist them together. Next solder pins to the ends of the speaker wires, being careful not to let solder flow into contact area. Then push the pins into the mating plastic plug housing. Each pin should snap into place if it is assembled correctly. The assembly work on the battery pack subassembly is limited to twisting the wires and attaching the connector plug. Note that this connector Is polarized and can only plug In one way. Verify thai the batlery connector polarity is correct be- cause reversed polarity will de- stroy the transceiver! Solder a four-inch length of shielded coaxial cable to the mi- crophone with the shield con- nected to the negative side of the microphone. Then conned the cable to the polarized con- nector again observing polarity Fasten the microphone into the plastic snap-in bushing with a room- temperature vul- canizing (RTV) silicone adhe- sive. Mask the front surface of the microphone with masking tape to prevent the entry of any adijesive in the microphone or it could be ruined. Be sure that the wire side of the microphone is flush with the back of the . continued on page 60 BUILD THIS REFLEX TIMER ' Clf #>Off o * Reflex Timer How fast are your reflexes? The reflex timer wiU show you. DAN KENNEDY HOW LONG DOES IT TAKE YOU TO dose a switch after you hear a buzzer? When driving, how long does it take to hit the brakes after you see an obsta- cle? What we're realty asking is, "How quick are your reflexes?" Our reflex timer will show you. Tfestiog your reflexes is a two- person job. To use It. one person secretly starts the timer, which sounds a buzzer. Upon hearing the buzzen the person whose re- flexes are being tested turns the timer off as fast as he can. (That also turns off the buzzen) The person s reflex time can then be determined by observing a ID- LED display Figure 1 Is a schematic di- agram of the reflex timer, which consists of a 555 timer (ICl) and three 74LS193 4'bit binary counters {IC4^IC6). The 555 timer outputs a pulse about twice ever>^ millisecond, or 2000 times a second. Tlie timer is se* crclly activated by SI which then turns on piezo buzzer BZl via Ql» and connects the clock output from the 555 to the bin- ary counters through one nand gate (lC3-d), as shown in Fig. 2, The person being timed turns S2 off, which disconnects the 555 output from the counters and turns off tiie buzzer Quad NANO gate IC2 Is configured as two separate latches, also as shown in Fig. 2, to prevent the contacts of SI and S2 from bouncing. Depending on how long it takes the person to shut off the timer, a certain number of LED*s light up. The numbers next to each illuminated LED ( L 2, 4, 8. 16, 32, etc.) are then added together to give the per- son's reflex time in millisec- onds. If all the LED*s are lit. the total elapsed time is 51 1 millise- conds or 0.511 seconds. The in- dicated time can be multiplied by a correction factor to give a more precise measurement, but that's not necessary for relative measurements or "contests'to determine who has the fastest reflexes. Well talk more about the correction factor later. A 7805 voltage regulator (IC7) provides -r 5-volts DC for the cir- cuit from a 9-volt battery. TVvo 5. IK resistors (R! and R2)anda 0.047 \lF capacitor (CI) give the 555 a clock frequency of approx- imately 2000 Hz, or 2 cycles per millisecond. Tty using a few dif- ferent 0,047-(xF capacitors for CI to get the frequency as close to 200 Hz as possible. Closing switch 54 puts C2 (a 47 [lF ca- pacitor) in parallel with CI. That slows dowTi the timer to demonstrate how a binary counter works, The numbered LEDs will count the number of times that LEDl turns on. The formula 1440/(R1 + 2R2}C1 gives the timer frequency in Hz, I —I i a 3 a' z 43 FIG. 1— SCHEMATIC OF THE REFLEX TIMER. It consists of a 555 timer and three 74LS193 4.blt binary counters. ^^^^^ are in kilohms and CI is In microfarads. Switch S5 lets you turn off the buzzer when demonstrating the counters with the lower clock speed. The 74L5193 cotmters The 74LS193 is a 4-bit up/ down binary^ counter that can operate at clock speeds up to 25 MHz. Data input pins po-P3 allow a 4-bit binary number to be loaded into the counter be- fore counting begins. The loaii input (Ud, pin 11} must be pulsed low to load the 4-bit number. Notice thai the data in- puts (PO-P3) of all three counters RG. 2— QUAD NAND GATE IC2 is configured as two separate latches to prevent the are grounded and that the LOAD contacts of S1 and S2 from bouncing. The clock output from the 555 is connected to p 1 ns are held at +5 vol ts the binary counters through one gate of IC3. through R4. Momentarily clos- 10 11 12 13 14 15 16 17 Era 00(1) 1 0U2I 0 02(41 0 FIG. 3— WHEN ONE COUNTER RNISHES counting up to 15, it sends a carry pulse to the next counter. Here's how a counter responds to 17 clock cycles. 5V RG, 4— THE COUNTERS ADVANCE one count on each low^to-hlgh transition of the clock (point "X" on each rising edge). RG. S— THE REFLEX TiMER PROTOTYPE was buiit using perforated constructfon board and point-to-point wiring. Switches Si and S2 are housed In piastic 35mm fiim canisters and connected to the main baaM with three-connector wire. ing switch S6 grounds the ld pins and sets all three counters to zero. Although the clear inputs (cl) are permanently grounded, pulsing them to +5 volts would also reset the cir* cuit*s counters. The COUNT DOWN inputs (dn,, pin 4) are held at 4-5 volts through R16. The clock signal from pin 3 of the 555 is applied to pin 5 on the first counten IC4, When 1C4 finishes counting up to 15 J t sends a carry- pulse from its VP, J (pin 12) to the count up input (up,, pin 5] of the second counter* ICS- Likewise, when the second counter reaches a count of 15, it sends a carr>^ pulse from it upo pin to the third counter ICS. Figure 3 shows how a counter responds to 17 clock cycles. A low*to-high tran- sition triggers the counter. When a counter reaches 15, it starts counting again at zero- Accuracy Figure 4 shows the clock sig- nal that is fed to the counters, which advance one count on each low-to-high transition of the clock (point "X" on each ris- ing edgej. We can start and stop the count anywhere In the clock cycle. Suppose we start at Tj (just after a low-to-high transi- tion); the timer will advance one count when T^ is reached, which will correctly indicate 0.5 milliseconds have elapsed, Howeven we don't know exactly where In the clock cycle the timer will be started. Suppose the timer is started at T2 and stopped at T3. The timer would read 0.5 milliseconds more than the actual elapsed time be- cause the timer started at T2 and immediately registered one count. A similar situation occurs at the stop time. If we start the timer at Tj and stop at T3 the count win be correct. But if we start the timer at Tj and stop at T.|» the timer would read 0.5 milliseconds less than the actu- al elapsed time since we stopped the counters just before a low- to-high transition. That means that the accuracy of our timer is limited to ±0*5 milliseconds when we use a 2000-Hz clock. (That is also plus or minus the least significant bit (LSB) of our counters, which is the LED without a number next to it. Another factor that deter- mines the accuracy of the refiex timer is the clock frequency If you have a frequency counter you can measure the clock out- put from ICl directly If a fre- quency counter is not available, you can measure the clock fre- quency using a stopwatch and PARTS LIST All resistors are %-watt, 5%. R1. R2— 5100 Ohms R3— 10,000 ohms R4 — 4700 ohms R5^R15--470 ohms Rt&— 1000 ohms Capacitors Cl— 0.047 ceramic C2 — 47 ^lR 10 volts, electrolytic Semiconductors ICI— 555 timer iC2, 1C3— 74LS00 quad NAND gate IC4^1Ce— 74LSt93 4-bit binary counter IC7— LM7805 5-vort regulator Q1— 2N3904 NPN transislor LED1— LED10— red LED LED11— yellow LED Other components BZ1— PiezD buzzer SI, S2— 'SPDT switch with center off S3-S5— SPST switch 36— SPST normally-open push- button switch Miscellaneous: Perforated con- struction boardt standoffs, project case, IG sockets, wire, sotder, etc. the calibration LED {LEDU). If the clock frequency is exactly 2000 Hz. then it would take 40.96 seconds for LEDIl to turn on twenty Limes. The au- thor measured 4L5 seconds for LEDl 1 to light twenty times. To calculate the frequency multi- ply 2000 X 40.96/4L5: that comes to 1974 Hz. (A frequency counter measured it at 1979 HzJ With a clock frequency of less than 2000 Hz. the indicated reflex time would be slightly less than the actual reflex time. Mul- tiplying the indicated time bv a factor of 2000/1974, which is equal to 1.013, would give the reflex time correct to the nearest millisecond. Construction No PC board is required to build the reflex timer. Instead you can use perforated con- struction board and point-to- point wiring. The photo in Fig. 5 shows how the author's pro- totype was built and installed in a plastic case. The author used plastic 35mm film canisters to house switches SI and S2, although other mounting schemes can certainly be used. Three-con- ductor wire must be used to connect SI and S2 to the main board. Its a good idea to mount the ICs in sockets. That way you can easily exchange the 74LS193 swith 74LS192'stosee how a decade counter works. The 74LS192 has the same pin- out as the 74 LSI 93 but counts only to nine before generating a carry pulse and repeating. Using those chips, tlie timer would display up to 399/2 = 199.5 in binary-coded decimal (BCD). If you wanted to read the time directly in milliseconds (from BCD) you would have to change the clock frequency to 1000 Hz. The reflex timer is sure to be a smash hit at your next party — with it, you will be able to see for yourself who has the absolute fastest reflexes. R-E Train at HOME to be an Eiecimnics Technician i As the demand far cofnpiiter^ and iTiicfOfwoci?^*or5 in business, manufacturing and communtctttions coniinuiev lo grow. m> does ibe need ror qu^iliiied technicians. \t\ nol unusual lor esiperit?nced technicians to DeperxJing on the piogram you scleci, you'll perifea your skills using ihis advanced equipment, included in the price of tuition: • IdM'Compatible PefKKial Ccmiputer • Digital Mtiiti meter • Digital Logic Pfobe • Elenco Oscilloscope • Portable CelluJar Telef^ne i\ttin:w- £%lra* Thai Efihamre Your Trainiftg Pseople^ College rntroduce*- iome iraming fifsis to make your learning experience more complete: ■ Ac cetera ted Learning System — a ^^dentifically provi-n study sys^iem that helps you learn fascef and easier thjo over before. • Vidi»o Tutor Trainir>g lapt^ — give you a pernianeni, visual I record of informative leciures and t lose-up demonstrations. • Experience Labs — professionally designed exp*,»rimenrs that give you hands-on "bench*' enpertefKie. • JrxJosf ry CenilKation Training QukSe ^ provided with four of cHjr programs Prepares you for examinations ^-ou may take for your pfolessional licen*ie or cenific atinn. To help you gel sUrleti on > our education Peoples College h.1^ reduced tuition rates and offers low monthly ptiyment plans with no finance fees, Jso don 'I deliiy. call or write for more information Pfbf COLOR CATAIOC Mail Co C^U TOLL FREE 1-800*765-7247 Out prograrri^ ar*? accredited by the Accr«iit(ng Comniission of tho National Homi.' Study Council YESI 1 Hould like to know more about your tratnmg prt^rarm. Send a catalc^ to: Name City Slate Zip Phone ft Peoples Oollege lOF ISniPENntST STUDIES 233 Academy Ori%e • P.O- 8oi 411760 Kinimmee, FL 34742.1 76S 1, r«>plri Ct™*p R1092 CIRCLE 184 OH ¥BE^ INFORMATION CARD THIS MONTH WE COr^INUE our PC*baseci test*equip* mcnt series by building the T1004 digital logic IC tester and identifier. It is capable of testing 7400, 5400, and 4000 series IC^s. In fact, the T1004 should be able to test any digital IC family that has the standard Vec ( + 5V> and ground configura- tion {Vqq on the upper left comer of the IC pack- age and ground on the lower right). On a 14*pin DIP that would mean that ^cc would be pin 14 and ground would be pin 7. The T1004 will accept 14-. 16-, 18-, 20-, 22-, and 24-pin DIP'S. The T1004 performs the follourlng tests: THith table, positive-going in- put threshold, negative- going input threshold, input hysteresis, output source capability under load, and an open-collec- tor test. Additionally, the T1004 predicts (based on a best-guess analysis} what type of IC you are testing (HC, HCT TTL, etc.). From now on, youTl find grab bags of un- know^n lC*s very appeal- ing because the T1004 has a feature that can help you identify those unknown digital ICs, If the IC being tested matches any of the IC s al- ready in the IC database, the T1004 will find and display the names of those ICs. Running a complete test on one or all of those names wllL In many cases, provide you with a comprehensive picture of the IC under test. The T1004 also lets you add fCs to the database. As we expand our IC support library we will make up- dated files available on the RE- BBS (515-293-2283, 1200/2400, 8N1). General operation Figure I shows the T1004 block diagram. The chip-select section is driven by the Front End section which we dis- cussed in detail in our June PC-BASED TEST BENCH The T1004 digital logic IC tester and identifier can handle 7400-, 5400-, and 4000'Series ICs. STEVE WOLFE 1992 Issue: It selects and de- selects every other section In the T10D4. The reference-volt- age section provides a 2.5-vo!t reference for the analog-to-dig- itaJ converter (ADC) section and also for the digital-to-analog converter (DAC) section. The pull-up or pull-down section (PUPD) is capable of providing a 10-kilohm pull-up or a 200-ohm pull-down to any or all of the test-socket pins 1 except the V^^, pin). The DAC section produces a voltage (in 20-milHvolt steps be- tween 0 and 5 volts) which is fed to the DAC multiplexer {MUX) section. The DAC MUX can apply the DAC voltage to one of pins 1 through 23 of the zero insertion force (ZIF) test socket. The DAC multiplexer can also disconnect the DAC voltage from the test socket. The ADC multi- plexer can select a single voltage from one of pins 1 through 24 of the test socket and feed that volt- age to the input of the ADC section. The socket- ground section supplies ground to one of six test- socket pins [pins 7— 12) to connect the ground pin of the IC under test to ground. Ibsts performed • 'Huth-table test During this descrip- tion well use a 7432 quad 2-input OB gate as an ex- ample device. Because the 7432 is a 14-pin de- vice, the socket-ground section grounds pin 7 of the test socket. The DAC section is disconnected from the socket. The de- vice is looked up in the database and an input/ output (I/O) mask is stored as three variables (or three 8-bit bytes). The I/O mask differentiates inputs from outputs* During subsequent test- ing, the I/O mask protects outputs from being inad- vertendy grounded. Next, a line of the truth table is read into the three variables from the data base. The portions of those three variables which correspond to inputs are sent to the IC under test via the PUPD section. At this point the ADC multi- plexer and ADC sections scan every test socket pin for the re- sultant voltage. Voltages found to be greater than 2.4 volts are converted to highs, and those less than 2.4 volts are converted to lows. The highs and lows are converted to three 8-bit bytes that are compared to the bytes that were read in from the truth table. If they match, the IC has i m a 47 TOOACSlCltON VOLTAGE SECTION TO THE FRQHT EUO TO EVEHV SECTION DATA BUS t CHEP SCLECT SECTlOfJ PULL UP OR PULL WWi DAC MUX TO 23 21^ SOCKHPINS TO Om OF S3 ZIF-SOCKET PINS DAC ADC MUX ]4- FR(miON£OFa4 3F'S0CKET PJNS ADC SOCKET GROUND TO ZIF^SOCKET PIN 7.8,9.10,1 1, OR 12 HQ. 1— 11004 BLOCK DIAGRAM. The Front End drives the chl(>-select seclioa, which selects and deselects ev^ry other section in the T1004. passed the first line of the truth table, • Low-to-high input teat In this section three bytes are again sent to the test socket. The bytes are selected based on the following criteria: A kno\ra input pin on the IC under test is being held low. Additionally, when the pin being held low is taken high, a known output pin will change state. Working to- gether, the DAC and DAC muUi- plexer sections take control of the input pin and slowly ramp its voltage from zero to the volt- age level needed to cause the output pin to toggle. The volt- age on the input pin is then read back and displayed on- screen ne.xt to the label **VT + • High-to-low input test In this section three bytes are gj again sent to the test socket. § The bytes are selected based on the following criteria: A known o input pin on the IC under test is E being held high. Additionally, g when the pin being held high is z taken low, a known output pin 8 will change state. The DAC and 2 DAC multiplexer sections take f control of the input pin and uj slowly ramp its voltage from +5 volts to the voltage level needed 46 to cause the output pin to tog- gle. The voltage on the input pin is then read back and displayed next to the label "VT-:/" • Hysteresis Input hysteresis is the dif- ference between the trigger point of an input being taken high and the trigger point of the same input when it is taken low. ICs such as a 7414 intentionally have a large amount of hys- teresis to give them increased noise Immunity. The T1004 cal- culates the hysteresis and dis- plays it on the screen next to the label "HYS:." The T1004 calcu- lates hysteresis as follows: IVT + ) - [VT-) = (Hysteresis) • TTL inpiit compatibility A TFL-compatible input must trigger when fed a voltage not larger than 2A volts. If VT+ Is greater than 2.4 volts then the IC under test fails the test. • Output-load test The output-load test is per- formed by taking an output high and loading it with 200 ohms to ground for a very brief period. During the time that the load Is present, the ADC reads the loaded voltage. This test will reveal weak or damaged gates, help to identify the gate type, and test for an open-collector condition. Any of the tests described above may be omitted from the testing procedure. The testing process is defined by a script, which is a set of test instrtic- tions for a parlictjlar IC, Each IC has lis own script which TSW or the end user writes to suit a particular IC. IC scripts are compiled using a program sup- plied by TSW. Script tutorial IC's not presently supported by the T1004 can be added to the existing database by the user. Each script contains the IC's name, whether the IC is an open-collector device, and Its truth - table in format ion . Scripts can be written using any ASCII text editor. The easiest way to create a new script is to copy an existing script and edit it as needed. Once a script has been created, it can be compiled and added to the appropriate database. You can compile a script simply by selecting that option from the software menu. You will be asked to give the name of the script (example: S7400.TSW). The compiler will then open the script and get the IC name* Next, it checks to see if the tar- get iC already exists in the database. If it already exists, then the preiious version of the IC script will not be overwritten- The delete function lets you remove any IC from the database. If the target IC docs not exist In the database, then the compiler will compile the target script file and add the re- sults to the database. The origi- nal script is written in a form that is easy for a person to fol- low. Once compiled, the script takes on a more compact form that can be used by the main testing program. Scripts for 14- pin iC's must be located in the directory ^TSWMCTEST- \D14\SCR1PTS," Similarly, scripts for 20-pin IC's must be located in the directory ' \TSWMCTEST\D20\SCRIPTS , ' and so on. Tkke a look at Listing L The top line (TUTORIAL SCRIPT NUMBER 1) and the numbers down the left side [1-14] are not part of the script file. They have been added for reference onJy; and should not appear in serfpts that you write. The s>'Tnbols in the beginning of each line tell the software what kind of function is to be performed. A ' tells the soft- ware that the two following vari- ables are the ICs name and whether or not it is an open- collector device, respectively, A ■ tells the software that the letters *f." "O, ' 'V/* and "G" des- ignate inputs* outputs. Vq^^ and ground* respectively "V" and "G" always represent V^^ and ground* respectively. The numbers " 1 " and "0" always rep- reseni a logic high and a logic low. respectively An tells the sofJware that following symbols designate the truth table of the IC under test, and that the data should be sent and the results should be read back. A ' indicates that the following symbols designate the truth table of the IC imder test, and that the data should be sent but not read back* A 7" tells the software that the following sym- bols designate the truth table used for the "low- to-high input threshold test" of the IC under test, A T says that the two following numeric variables designate the *'low-to-hlgh In* put threshold test" Input and output pins* respectively, A "\" Indicates that the following symbols designate the truth ta- ble used for the "high- to-low in- put threshold test" of the IC under test. A"-" means that the following symbols designate the truth table used for the "output load test" of the IC under test. An " = " means that the follow- ing numeric variable designates the "output load test" output pin. Lets take a closer look at the script in Listing L Line ( I) must contain three string variables separated by commas. The first variable in the line must be a " ?" which tells the software that the next character Is the name of the IC . The IC name can contain nine characters* In this case the name is "7400/* The next character on line (1) tells the software whether or not the IC being tested is an open -collector part: **T* for open-collector parts or "N" for parts without an open collector. Line (2) represents the pin numbers of the IC being scripted. In this case the IC is a 14-pin package. Line (3) is the first line of the truth-table sec- tion* From that line the test software is able to determine whether to treat any given pin as an input or as an output. The line must be correct for the lines that follow to work correctly. If the IC being scripted has more than one input/output mode |a USTING 1 TUTORIAL SCRIPT NUMBER 1 IC KAKE CD ?,7400,» vtn mmzns {2\ oooooooooiiixi 12345678 901234 KftlK TRUTH TABLE [1) |,I,I,0,I,I,0,C,O,I,I,O,E,I,V (4) %O,0,l,O,O,l,G, 1,0,0, 1,0, Q,V (5J %0,l,l,Orl,l.G,l,0,l,l,0,l,V [7) •aa*o.i*iiO,G,o,ia,o,i,i.v TO BIGS IKPtlT TBST (8) /,l,0,l,l,0,i,<3,l*l.<»*l,lrO,V (9J lt2,3 HIGH TO LOW IKptrr TEST (lOj \,l,l,0a*l,O,<3,O,l,t,0,t,l,V (11 J UZrl OUTPUT LOAD TEST (12) -,0,0,l,O,O,l,G,l,0,0^ 1,0,O^V (Hi TSW ELECTftOMICS 14 I- IK IC TEST SCniKT 74245, for example), you should give a new line just prior to the IC's mode change. You can use as many lines as needed, and you can use them in any section of the script. In this case pin 1 is an input, pin 2 is an input, and pin 3 is an output* Pins 4-6 follow the same pattern and pin 7 is ground. Pin 8 is an output, pin 9 is an input, and pin 10 is an input. Pins 11-13 follow the same pattern and pin 14 is V^^. If you check your data book you will see that this accurately de- scribes the I/O of a 7400, Line (4) begins with an That means that any *l"s and "0"s corresponding to inputs should be sent to the IC and that the "Ts and "0"s corre- sponding to outputs should be read back from the IC. If the"l "s and "0"s read back do not match the those predicted by the script then a fail condition exists, A 7400 is a quad 2-tnput nand gate. The line tests all four gates at the same time. In line (4), pins 1. 2, 4, 5, 9. 10, 12, and 13 are all taken low. Each function- ing NAND gate must respond by outputting a high. The results are read back and compared to the script. (Any error within the script will cause good IC s to fall the test). Lines [5) through (7) send and test the remaining truth* table conditions. An can be used only in the truth- table section. Within that sec- tion, you can use as many tines as you like. Line (8) begins with a "7.'' That character causes the "low- to-high input test" (LHT} to be performed. The LHT Is used to determine the voKage that an Input considers a high, or log- ical. The "l"s and '*0*s corre- sponding to inputs are sent to the IC. Line (9) contains the character which precedes the input and output pins to be used during the test. In this ex- ample pin 2 is used as the input and pin 3 is used as the output. When pin 2 is taken from low to high, pin 3 changes state- It is not important whether pin 3 goes from high to low or low to high* but only that a change of state occurs. The T1004 In- creases the voltage present at pin 2 (in 20-mlllivolt steps) until pin 3 changes states. The volt- age on pin 2 Is read back and displayed. Lines ( 10) and [11) contain the character and "L" They work in the same way except that the input voltage is swept from high to low. This test Is used to deter- mine VT-. Line (12) contains the character That sends a truth table that must produce a high on one of the outputs. The next line contains the character which tells the software which output pin is presently high. We could have chosen any one of four outputs since tliey are all high. In this instance pin 3 Is chosen, and loaded with 200 ohms to ground. The load test determines the sourcingca- pabiUties of the gate, whether the part is open-collector or not. and provides clues that the soft- ware uses to predict the ICs family. The predicUon of family or type should be considered a best guess (not absolute). Line (141 contains the text * TSW ELECTRONICS," which is there as an end-of-file marker for the compiler. Listing 2 shows ^'TUTORIAL SCRIPT NUMBER 2/^ Line (1) indicates that the device is a 4040 and that it is not an open* collector device. Line (2) indi- cates that a 4040 is a 16-pin de- vice, A 4040 is a 12-bit ripple counten Line [3) indicates that pins 1—7 are outputs, pin 8 is ground, pin 9 is an output, pins 10 and 11 are inputs, pins 12-15 are outputs, and pin 16 is Vex:* Pin 10 is a falling-edge triggered clock input. Pin 11 is used to reset the counter, and is active only when high. Line (4) intro- duces the ''% ■ command, which is similar to the command, except that no test is performed; should be used whenever you wish to send a byte to the IC without testing for a result. In line (4) the reskt line (pin 11) and CLOCK line (pin 10) are taken high. On that same line all of the outputs arc shown low, which is an accurate represen- tation of the effect that a reset would have on the outputs. Be- cause line (4) is a *' % ' line, we do not actually test the outputs. On line (51 the reset line is re- leased. On line {61 the clock Is taken low activating the first output line (qoK Because line (6) uses an Instead of a the outputs win be tested for ac- curacy. The command al- lows you to configure a device before you begin to test it. It can be used in any section and as often as you like. In the low- to- high Input test, it Is used to rec- onfigure the 4040 before we sweep the Input. In this case, we are using the reset input to determine the low-to-high threshold (VT-F). The only pin that could be used for the high- to-low input test is the cloc k pin. Because clock input pins require fast transition times, they are not suitable for use In threshold tests. For that reason, the high- to-low input test is omitted for the 4040 IC- You can omit any section except the section and the TSW ELECTRONICS" section, A must precede truth-table, threshold, or out- put-load tests. It must appear at least once or as often as needed. LISTING 2 TUTORIAL SCRIPT NUMBER 2 I C Mm (21 0 000000001111111 13345C?a^ai33l5fi KAII* TSOTH TABLE (31 I^O,O,O,O#O,O^0,C,0,I,I,0,0iO|O,V (il %,o,o,o,o,o,o,Q,<:,o,i,irDpOtO,o,v {5} %,O,O,O,O,0,Op0rC,0,l,O,O,O,O,O,V (fiJ •,0,0,0,0,0,0,0,0, l,0>O,O,O,O,O,V (7 J *,B,0,0,0,0,O,O,<;, 1,1, 0,0, 0,0,0, V (Sj •,o,o,o,o,o,o,i,c,a*o,o,o,o,o,o,v (9 J •,0,0,0,0,D,O,l,C,O,l,0,O,0tOrO,V (10 J *,O,O,O,O,O,0,1,C,1,O,O,O,O,O,O,V (llj ',0,0,0,0,0,0, 1,0, 1,1,0, 0,0, OrO,V (laj •,O,0,0,O,0,l,0,G,O,Q,0,O,0,0,O,V (13 J 0, 0, 0, 0, 0,1,0,0,0, I, o,o,o,o,o,v (141 •,O,a,0,0,O,l,O,G,l,0,0,fl,0,0,O,V (15 J •,0,0,0,0,0, 1,0,G,1, 1,0, 0,0,0,0,V (16J •,O,0,O,0,0,l,l,G|0,0,O,O,0,0,0,V (171 •,0,O,0,0,0,l,l,O,0,l,0,O,0,0,0,V (lei •,o,o,o,o,o,i,i,o,i,o,o,o,o,o,o,v (lij -,0,0,0,0,0,1,1,0, 1,1,0, 0,0, o,o,v Um TO HIGH INPUT TESt (20 J l,O,O,O,O,Or0,O|tJ,O,l,l,O,O,O,O,V (21) t, 0, 0, 0, 0,0,0,0,0,0, I, o,o,o,o,o,v ill] /, 0, 0, 0,0, 0, 0, 0, 0, 1,0, 0,0, 0,0,0, ¥ f23J 1,11,? QUTFTIT LOAD TEST (241 1,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,7 {251 %,O,O,0,0,O,0,0,O,0,l,0,0,0,O,O,V (261 -,0,0,0,0,0,0,0,0, 1,0, 0,0, 0,0,0, V (271 -,9 (2B} TStr BLECStONlCB Ifi PIl JC TEST SCRIPT Detailed operation We will use BASIC as an exam- ple language. As wcVe seen with previous peripherals, the first step in controIUnii the T1004 is to establish a base address and select the desired peripheral. The first bit of code will be: BAS-768 : OUT BAS + 31,4 768 (hex 3001 Is the factoiy-pre* set base address of the 1 1000, As noted earlier, this address is DIP-switch selectable. Next, we have an **OUT TO BAS + 31 / As you may recalL that address is reserved for peripheral selec- tion. The T1004 has a unit, or peripheral address of "4." Con- sequently, if we send an "OUT TO BAS + 31 ^ with a data byte of "4/* the T1004 will be readied for full I/O operation. The T1004 schematic has been split into two lialves and shown in Figs, 2 and 3, Address lines Ao^Ai (32 bytes) are used by the T1004 (or any other pe- ripheral! to address its IC's, and AO is the LSB of the address lines, (Lines as-ao are used by the 11000 only) The chip*select section shown in Fig. 2 (IC23-IC25) contains two 74HCT138's (1C23 and 1C241 Whenever their c2a and g2B lines are low and gi Is high, one of eight outputs will go low de- pending on the address present on the A. H. and c inputs. IC23 is active when \i\-:N is high» send is low, and rd is low IC24 is active when BEN is high, send is low, and vvR is low All but one of 1C24S output lines drive the load line of the 74HCT573 latches. Because the load line of a 74HCT573 must see a high to store data, IC25 inverts the ac- tive lows produced by IC24. The voltage-reference section, also in Fig, 2, is composed of IC26, R21, Rl. IC9-a. and ICS b. IVimmerRSl Is adjusted for 2,5 volts at TPL That provides the ADC section with a precise ref- erence voltage. The reference voltage also passes through IC9- b and used bv the DAC section. An ' OUT TO BAS + 7 ' will load a data byte into IC15 (a latch). DAC IC16, in combination with IC17-a, will produce between 0 and 5 volts which is propor- tional to the byte stored in IC15, The voltage produced will be a function of n x (5/255), where n Is equal to the number loaded into thelatch(lC15). ASOO-ohm potentiometer (R22) is used to set the full-scale output voltage. If IC15 contains a value of 255, then R22 should be adjusted for 5 volts at IC17-a pin 1, The DAC multiplexer section is com- posed of IC18 through IC22. A latch IIC18) used to hold the DAC multiplexer address. The FIG. 2— Ifst THIS PORTION of the T1004 schemallc, address lines A0-A4 are used to address IC's, least Significant three bits of the address are fed to each of three 8-bit multiplexers {74HCT4051). The remaining data Unes are fed to IC19 (a 74HCT138). which activates only one of the multiplexer IC's (IC20-IC22). Assuming that the address byte sent to IC18 was less than 23, the DAC voltage Is then passed through to the test socket. If the address byte is 23 or greater, then the DAC voltage is disconnected from the test socket. 3 4 -A 1; * OS J ■ • 0? 9 4 * * -tj **SVfCT IS J t RG, 3^THE PULL UP OR PULL DOWN section pulls any or all of the test socket pins high or low as needed. Latch ICIO is used to hold the ADC multiplexer address* The least-significant three bits of the address arc fed to each of three 8-bit multiplexers. The re- maining data lines are fed to ICll, a 74HCT138. which acti- vates only one of the multiplexer IC s (IC12-IC14K Assuming that the address byte sent to ICIO was less than 24, the ADC re- ceives voltage from only one of the test socket pins. If the ad- dress byte is 24 or greater, then the ADC is disconnected from the test socket. The pull up or pull down (PUPDl section, shown in Fig. 3, Is composed of ICl, ICS. IC6. RIO, Rll. R13-R16. R17-R19, and 915-Q29. This sec- tion pulls any or all of the test socket pins high or low as needed. The PUPD section Is primarily responsible for truth- table functions. Three bytes are used to control the PUPD sec- tion. Byte-A controls test socket pins 1— 8» Bytc-B controls pins 9-16, and Byte-C controls pin^ , 17-23. Pin 24 Is reserved for Vcc only and is not affected by the PUPD or DAC sections. The sections controlled by Byte-A, Byte-B, and Byte-C are func- tionally identicaL so well de- scribe the Byte-A section only Well assume that the number 85 (01010101) has been sent to ICL The OUTPUT enable line on ICl (oe) is grounded so the 'Q" outputs must follow the "D" in- puts. Pin 1 of DIP RIO will re- ceive a high, ptn 2 a low, pin 3 a high, and so on. Resultantly the base of Ql will be taken high connecting ground to Rll pin W * That causes pin 1 of the test socket to be pulled low through 200 ohms. Because the base of Q2 is low. it will not conduct. That allows Rl 7 pin 3 to pull Rl 1 pin 2, and subsequently the test socket ptn 2, high. The IC ground section con- sists of IC2-1C4, R12, and Q9-Q14. Any byte latched into IC2 is passed directly to IC3, Byte values ranging from 0 to 5 transition to a low one of lC3s output lines. IC4 Inverts the signals which are then fed through R12 to the bases of Q9-Q14. Only one line is active at a time, thus ensuring that only one transistor is con- ducting at any given moment. Transistor Q9 is selected when driving a 14- pin device and Q14 would be used when driving a 24-pln device. Regulator IC27 and its associ- ated components produce - 5 volt5» which is used by the DAC (1C16K Regulator IC28 and its associated components pro- duce - 5 volts for the multiplex- ers (IC12-IC14 and IC20-IC22K Regulator IC29 and its associ- ated components produce +7 volts, whicti the op-amps re- quire in order to produce a full 5-voll output swing. Regulator IC31 and its associated compo- nents produce + 5 voUs for the IC being tested. Regulator 1C30 and IC32 and their associated HEATSINK components produce +5 volts for all the remaining IC's. Reg- ulator IC31 produces +5 volts and is dedicated to supplying Vcc to fhe test socket and +5 volts to the pull-up resistors R17-R19, Constructioii To build the T1004 pe- ripheral, a PC board is recom- mended. You can either buy a PC board from the source men- tioned in the Parts List or make your own from the foil patterns weVe provided. Note that the parts for the Front End are con- talned on the T1004 board shown with a dark line around them in the Parts-Placement di- agram of Fig, 4. There is a sepa- rate Parts List for the Front FRONT inO End* which was discussed in detail in the June issue. Do not confuse the two lists of parts, or where they go on the board. Also, for many of the capacitors, notice that there are three holes on the board, with two of them electrically the same. The holes accommodate capacitors with different lead spacing. Use whichever pair of holes on the prlnied-circuit board that best fits the capacitors you intend to use for the project. One of the voltage regulators {IC32) is in a TO-3 case that must be mounted on the back panel of the T1004 case. Mount the regulator, along with an ap- propriate heatsink, on the back panel and hardwire it to the board. Figure 5 shows the com- *_JHL_ fl6 = ^ ■ 'Z I fm t f 1 r' " 1 I : 1 , r c TPlO O to ^ & R2 1 IC15 "ICS 10^^[:iiOo,e,opooDo 3 OOOOOD""^ 0 1 0 Q1 1 023 C 1 1C10 C IC12; IC13; iDt4; ad, IC31 *^ 24 22 20 IS 1& UXy ODD 1 2 4 e B 10 12 TOZIFSOCKHPINS FIG, 4— PARTS-PLACEWENT DIAGRAM. The parts for the Front End are shown with a dark Una around them. There is a separate Parts List for the Front End, so don't confuse the two lists of parts, or where they go on the board. TO ZIF SOCKET PINS I 63 T1004 COMPOKEhfT SIDE. T1004 SOLDER SIDE T1004 PARTS UST z UJ 54 All resistors am vv-watt, 5%, ynfess otherwise noted, R1— 2200 ohms R2— 10,000 ohms R3— 2320 ohms, 1% R4— 1000 ohms R5— 51 10 ohms. 1% R6— 2050 ohms. 1% R8— 1100 ohms R9— 240 ohms RIO. R12, R13, RlS-1000ohms. 16-pin DIP R11. R14, R16— 200 ohms, 16-pin DIP R17-R20— 10.000 ohms. 10-pin SIP R21— 10*000 ohms, multiturn trimmer potentiometer R22— 500 ohms, multitum trimmer potentiometer Capacrtors Cl*-€7, ClO-Ct4, Cie-C25, C48— 0.1 5 |iF, potyslyrene C8. CI 6. C31. C35. C37, C39, 042. C45— 100 ilR etedfolytic C9, CI 5, 020. 032, 033, 034— not used 017, C2A 036, C38, C40, C41, C43. C44. C46. C47— 10 jiF. electrolytic Cafr—ISO pR mica picted T1004 board. When you use the T1004, position the ICs you want to test as shown in Fig. 6. 029—2,2 fiF, electrolytic C30— 36 pF. mica Semiconductors 101, IC2. ICS. 106. IC7. ICIO. 1015, IGie— 74HCT573 octal latch IC3. IC11, tClS. IC23. JC24— 74HCTl3a demultiplexer 104. 1025— 74HCT540 octal buffer ICe— ADC0803 8-bit A'D converter !C9— L1\435Q dual op-amp !012^IC14, IC20-I022"-74HCT4051 6- bW multiplexer ICIfi^DACOaOO or DAC08 D/A converter 1017— UVI621 BAN op-amp 1026— LM336 voltage reference IC27, 1028— 79L05 voltage regulator 1029— LM317T voltage regulator IC30, IC31—Uy!7©05T voltage regulator 1032— UA7805K voltage regulator (TO-S case) D1— 1N4002 diode 02 1N5231 5.1-volt Zener diode Q1-Q29--PN2222 NPN Iransistor Miscellaneousr 24-pin ZtF socket* TO-220 heatsink. 10-3 heatsink, PC board, instrument case, wire, solder, etc. Software Each peripheral has its own software program to control its operation. All of the programs PIG* 5— THE COM PLETED T1004. One of the voltage regulators. 1032, must be mounted on the back panel of the T1004 case. end up in one directory as you add more peripherals. Software for the 1 1000 and the entire sc- ries of peripherals, including the T1004, can be downloaded from the RE-BBS (516-293-2283. 1200/2400, 8N1) as a self-unarchiving zip file called T1004,EXE. Both compiled and uncomplled soft- ware is included. Software is in- eluded free with the purchase of any peripheral from the source that is mentioned in the Parts THE Tim AimfS OOHHECTS Vq. (+5 mis DC) TO THIS PIN. i PIHt(OfTKElWTEaRArED CiRCytT Biim TtSTED) MUST BE LOCATED HERE. CORRECT POSlTlONlNtS tNCORREQT POSmONING FfG. 6— BE SURE TO POSITION the IC's you want to test In the test socket as shown here. FRONT'END Resistors R1™33 ohms. 16-pin DIP nesrstor R2— 2200 ohms, 10*pin SIP fosistor R3— 1000 ohms. lOiHn SIP resistor Capacitors Ct-C7— 0J5 |jlF, 50 volts, monofythic or polystyrene C8-C11. C20-<;2e-^1500 pF. 63 volts, polystyrene C12-C19— 220 pF, 100 volts, ceramic dtsc Semiconductors iCI— 74LS573D octal latch IC2— 74LS688D 8-fait magnitude com- parator 1C3— 74LS245D octal transceiver JC4— 74LS02D quad 24nput NOR gate [C5, IC6— octal buffer IC7— 74LS08D quad 2-input AND gale Other components J1 — 16-pin male header J2 — 18*pin male header J3 — male PC- mount OS25 connector Miscellaneous: 17 shorting b[ocks (for J1 and J2) Note: The following items are avail- able from TSW Electronics Corp., 2756 N. University Drive. Suite 166, Sunrise, FL 33322 (305) 748-3387: • HOOO kit— $65.00 « hOOO PC board only^$35.00 • 11000, assembled and tested— S77.00 List- (Software can also be pur* chased from that same supplier If you Ye not buying anything else from them and you have no PARTS LIST • 6-foot interfac«} cable (DB-26^>— $12.95 m T1001 kit (includes PC beard, all listed parts, project case, and p re- assembled front and rear panels— $149.00 • T1001 PC board only^9.00 • T^OOI, assembled and tested— S179.00 • T1001 software {included free with T1001 order)^S10.00 • Capacitor kit (unmeasured) — S21.00 « Capacitor kit (measured to within 1%)— $26.00 • T1003 kit (includes PC board, all listed parts, project case, and pre- assembled front and rear panels) — SI 59.00 • T1003 PC board only— ^59.00 • T1003. assembled and tested — $189.00 • T1003 software (Included free with T1003 order)— S10.OO • T1004 kit (Includes PC board, all listed parts* protect case* snd pre- assembled front and rear panels] — S209.00 • T1004 PC board only— S79,00 • T1004, assembled and tested- $249.00 • T1004 software {included free with Tt004 order)— $10.00 Add $5.00 S & H to any order. Check or money order only. way of downloading it from the RE-BBS.) With the T1004. you are on your way to automatic troubleshooting, r-e 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 **disiance education" — teaching by correspondence- through printed materials, computer materials, fax, and phone. No commuting to class. Study at your own pace, while continuing on your present job, Leam from easy-to- understand but complete and thorough lesson materials, with additional help from our instructors. Our Computer B,S. Degree Pro- gram includes courses in BASIC, PASCAL and C languages — as well as Assembly Language, MS DOS, C ADD, Robotics, and much more. Our Electronics B.S, Degree Pro- gram includes courses in Solid-Stale Circuit Analysis and Design, Control Systems, Analog/ Digital Communica- tions, Microwave Engr, and much more. An important part of being pre- pared to move up is holding the right coIJege degree, and the absolutely neces- sary part is knowing your field, Grantham can help you both ways— to learn more and to earn your degree in the process. Write or phone for our free catalog. Toll free, 1-800-955-2527, or see mailing address below. Accredited by the Accreditmj* Commi^^ion of the Noltoiial Hnnic Study Council GRANTHAM College of Engineering Grantham College Road SUdell, LA 70460 m B % 59 HAINDi TALKIE cominued from page 42 bushing to provide a gap be- tween the top of the m icrophone and the holes in the face of the bushing, (that permits sound to enter unimpeded.) It is recommended that the bushing be snapped Into the ex- trusion before performing the microphone bonding step or the plastic snaps will interfere with the microphone. Refer to the mechanical layout drawing Fig. 6 as a guide for mechanical assembly. At- tach the front panel to the PC board. First attach hex ring nuts to the front of both SQUELCH potentiometer R25 and VOLUME potentiometer R26, and coaxial BNC connector Jl. Be sure that the PC board abuts the front panel and is fastened with hex ring nuts on the out- side of the threaded barrels of the potentiometers and BNC connector Avoid placing exces- sive torque on the potentiome- ters by holding the hex ring nuts behind the panel with pliers or wrench while tighten- ing the front nuts with another wrench. lb complete the assembly of the transceiver, place the speak- er and grill inside the alumi- num housing extrusion and fasten It with four No, 6-32 x 5/16-lnch Philips-head screws, Internal tooth lock washers, and nuts. Connect all cables to their proper jacks on the PC board, and slide the assembly into the housing. Depress the transmit switch SI shaft so that it slides into the housing, (The transmit switch button cannot be attached until the board is inserted in the extrusion.) Attach the end panels with No, 440 self-tapping screws. Slide the knobs on the 0,125* inch diameter squelch and vol- ume potentiometer shafts (R25 and R26) and lock them in posi- tion with a 0,050-inch Allen wrench. Calibration & troublesliootlng Charge the power cells by con- necting them to the wall outlet- mounted AC to l2-volt DC adapter for 24 hours. Be sure the power switch is off white the power pack is being charged. The following test equipment is required to cali- brate the E-Comm transceiver: • OsclQoscope (one that is 50 MHz or fasterl • Frequency counter • Digital multimeter • Plastic coil- tuning sticks • A 50-ohm dummy load An FM-modulated RF source Is helpful but is not a require- ment for calibrating the trans- ceiver The 50-ohm dummy can be made by wiring ten 470*ohm resistors in parallel with short leads. Be sure that inductor L8 is not installed before starting the procedure! First tune the transmitter. Note: whiie adjusting the trans- mitter avoid touching any of the output circuit components be- cause some high voltages arc developed there. TUrn on the power switch and connect ttie oscilloscope leads to pin 1 of !C2. the quad'NAND Schmitt trigger and observe the wave- forms while pressing the trans- mit switch, T\veak inductors LI and then L2 until a clean sin* usoidal waveform is observed, (The frequency should be about 27.145 MHz,) Disconnect the oscilloscope and attach a frequency counter to pin 1 of IC2 through the high Impedance input of the counter. and adjust inductor L9 to set the frequency to 27.145 MHz* Reconnect the scope again and fine tunc inductors LI and L2 to get the best looking waveform. The waveform amplitude should be between 3 and 6 volts peak-to-pcak. if the waveform is satisfactorj^. solder Inductor L8 into the circuit board and at- tach the 50-ohm dummy load to the BNC antenna jack. Attach a current meter in se- ries with the power pack or the DC supply to adjust the final RF ampli^er Hook up the output pin of Jl to the oscilloscope and set it to 10 volts per division. While observing the current me ten press the transmit switch and look at the wave- form. Quickly tweak capacitor C30 so that the current is less than 400 milliamperes and the output voltage across the dummy load is about 35 volts peak-to-peak- To obtain maximum efficien- cy^ fine tune inductors LI and L2 and capacitor C30 to set the output power as close as possi- ble to the optimum value. That value is expressed as (V^,^^ peak X 0,707)2 divided by the in- put power (V^„ DC X DC), (This is a "trial and error*' step that calls for patience,) Do not try to set the output to max- imum power! If the 400-miliiampere max- imum input current is exceed- continued on page 94 p probe Is an o^lilgscope ai cesson- Uiai permits you*o rake mea- k^ufsemenis from two points in a circCMt without reference to ground. That eijiables the oscilloscope to be safely grounded without tha ^^.jieed for optoisolalprs or isolation transfor- ^^^ers. The probe can also make accurate mea* '^^urements of small signal differences even in tire presence of veo* h*gh common-mode volt- age. The probe. In effect, moves the input termi- nals from the front panel of the scope to the end of the probe. The inputs of a dilTerentlal probe with appropriate input ratings can. for exam- ple, measure power semlcondutor circuits be- cause no reference to {ground is needed. Both positive and negative sides of the balanced in- put offer high Impedance !o ground. High-im- pedance difTerential probes increase the Input istance and reduce the effective input capac- ce of the oscilloscope. The low-cost dillerentlal probe shown In Fig. 1 was designed primarily for induslrfal efcc- ^ tronic maintenance applications where AC volt- ages up to 500 volts rms are present. TMjIe 1 gives the leading specifications of that Instru* ment. It has selectable attenuation ratios of 20:1 and 200; 1. ^ Figure 3 is a stmpliiied schematic of the dif- ferential pmbe showing how it is connecied j between the circuit under test and the scope. A ' built-in differentf al amplifier converts the htgh- voUage difTerential input signal to a low-voli- age, single-ended output for a general purpose oscilloscope. Electronic test labs that perform a wide v^ii- ety ni' measurements are likely to own one or mort! differential probes. But until recently dlf- fen iHial probes have been quite expensive (more than 82000). As a result, you might stiU see oscilloscopes lluated'' above ground while tests of ungrounded circuits are made. White it Is neyer recommended, it can be done ^nfdy only If low voltages, say I to 28 volts, arc in- volved — and profjer safety precautions are taken. Some use a battery-ppwered portable scope, others remove the ground pin from the scope*s AC line plug or find other ways to ground" the scope's chassis. However, if one is to measure hundreds volts in ungrounded circuits, the case of oscilloscope and any metal parts touching that case are at a lethal potential. The scope operator could be electrocuted! That is why demand is increasing for low-cost , industrial-strength dif ferenttal probes that can make accurate mea- surements safely on the factory floor with conventional groiuidcd ^ciriural purpose os cilloscope. 1 me r thf at or is :l Learn how to uMe the acUve differential probe to make measurements k ungrounded systems — safely * Walter Dorfman is a Senior Etectrical al Avex Proljes, Inc. RG. 1— API MODEL SI-900 ACTIVE DiF- FERENTTAL PROBE suitable for making measyrements to - 1000 volU DC. High-voltage applicatton The best way to explain the value of a differential probe in an industrial setting is to review a problem that occurred In an ungrounded closed-loop control system and that was solved in a safe and timely manner with the probe, A conveyer belt in a manufac- turing plant was exhibiting radical speed fluctuations: It would alternately slow almost to a halt and then speed up to a rale that endangered nearby personnel. Solving this control problem was important be- cause, unless it was corrected promptly the production line would be shut douii. Figure 3 is the schematic for the belt drive in a control system closed around a programmable logic controller (PLC). The belt- drive DC motor is driven by a single-phase, full-wave SCR bridge that is electrically iso- lated from the PLC by four iso- lating SCR gate trigger mod- ules. The motor is electrically isolated from a tachometer that sends velocity signals back to the PLC, and both bridge and motor are electrically isolated from the 220-volt AC line by a 1:1 power isolation transformen When the belt was running, persons close to it couid ticar the sound of the drive motor change pitch as they observed the erratic belt speed. In at- tempting to trace the cause of the problem, the first step was to connect a conventional dig- ital multimeter across the motor's armature terminals to verify that the belt speed changes corresponded with motor voltage changes. Then the conveyor belt was discon- nected from the drive motor sheave to verify that the the motor*s speed variations were not due to variations in belt loading, lYoublestiOOtmg plan A troubleshooting plan was formulated to rule out possible faults and isolate the cause to one or more of the system ele- ments. Figure 3 shows that the PLC is referenced lo Earth ground. But the rest of the cir- cuit is isolated from ground to prevent a build-up of damaging or hazardous potentials, due to an insulation failure, within the motor-driven conveyorbelt sys- tem. An oscilloscope referenced and connected to Earth ground cannot make accurate measure- ments in a circuit that is not referenced to the same ground- The maximum peak-to-peak voltage that could appear in the bridge is about 622 volts, based on the characteristics of a sine wave for 220-volt AC, (The rms voltage must be multiplied by a TO THE CIRCUIT, mom ^ TEST BLACK AHENUATIOH NETWOBK factor of 2.83 to obtain the peak-to-peak voltage,) Exam- ination of the control diagram showed that differential mea- suremcnt techniques were needed to make accurate and safe measurements of this "floating" system. It would be necessary lo check logic-level SCR gate signals riding on the 220-volt AC line. Any differential probe suitable for making those measure- ments had to be capable of can- celling the large pcak-to-peak AC waveform, leaving only the desired logic-level signals, esti- mated at 3 and 12 volts DC. for analysis. The differential probe was first connected to Earth ground with the oscilloscope (BNC) con- nector. Then the probe was con- nected to the oscilloscope. In this case, the internal power supply was used so the probe coitld then be turned "on. Knowing that voltages in ex- cess of 622 volts AC peak-to- peak would be present, a probe attenuation range of 200:1 was selected. (Table 1 shows that for the probe used, the maximum working voltage to ground and between inputs is 500 volts rms. and the maximum non-de- structive input Is 700 volts AC rms or 1000 volts DC.) The 622 volts is divided by 200 to become a 3Jl-voit sig- DC TO DC CONVERTER TO OSCILLOSCOPE DIFFERENTIAL -V AMPLIFrER 1 RG. 2— A SCHEMATIC OF AN ACTiVE DIFFERENTIAL PROBE that can be internalty powemd by four IS- volt celts or an AC to OC converter TABLE 1- Bandwidth Accuracy Attenuation ratio Input resistance Input capacitance Input range Max, common mode input Common mode rejection ratio Max. output Output offset Power requiJBmenls -LEADING SPECS OF API PROBE DC to 15 MHz ±2% (nominal) 20:1 and 200:1 (selectable) 2 Megohms 26 pF (each side grounded) ± 700 V 00 f peak AC (200:1 attenuation) -70 V DC peak AC (200:1 or 20:1 attentualion) 600 V rms 70 dB (it 1 kHz ±3.5 V into 1 Megohm ±5mV (10'C to 40=^ C) Four 1.5 VAAceJls or 6 V DC. 50 m A adapter I PROGRAMMABLE LOGIC CONTROLLER ISOLATING SCR GATE TRIGGER MCDULfS 220V AC SCRl SCR2 iSOLAHON T1WSFDRMEH r 1 I 5CR3( SCR4 ISOLATED TACHOMBER RG, a— A CONVEYOR BELT SPEED CONTROL system, isolated from Earth ground. Indudes a programmable togtc controller (PLC), a futUwave, smgle^phaseSCR bridge. DC motor with isolated tachometer, and four isolating SCR gate^ triggering modules. nal. ITtie displayed output volt- age had to be kept within the ±3,5 volts limit of the probe J The two probe input le^ids were then carefully connected across the 220-volt AC line feed- ing the 1:1 isolation trans- formen The oscilloscope dis- played the 3.11-volts peak'to- peak sine wave shown in Fif(. 4- a. The regularity of the scaled - down sine wave showed that there were no faults in the line voltage. Both probes were moved to the secondar\^ of the isolation transformer and a waveform es- sentlally the same as the 622- voll peak-to-peak sine wave- form of Fig. 4*a appeared; it is shown as Fig* 4-b. However, small distortions and ampli- tude changes were seen on the negative peaks* and they were in s^Tich with motor-speed vari* at ions. The electrical noise in the waveform was believed to be due to the reflected loading effects of the motor's power and speed changes. The differential probe leads were than connected across the motors armature, and the periodic high-frequency oscilla- tions shown in Fig. 4-c were seen. Their occu ranee matched the motors speed variations* Next the probe was connected across the anode ( + ) and cath- ode ( - ) terminals of each of the four SCR's in the bridge, and their waveforms were observed. As shown in Fig. 5, all the SCR s exhibi ted some waveform distortion, butoneof them» Fig. 5-c exhibited more severe dis- tortion than the others. As the next step, the probe was connected across the gate ( + } to cathode { - ) terminals of each of the three SCR's that showed lower anode-to-cathode noise voltages. The differentia! probe successfully cancelled the 622 volts peak'to-peak AC on which the gate-to-cathode volt- ages were riding. The result was clean, normal gate trigger wave- forms with nominal 3 -volt peaks, as showm in Figs. 6-a, 6- b, and 6-d. However, the remaining SCRs gate*to-cathode voltage waveform. Fig, 6-e, showed time-varying gate-trigger pulses. (Il was the same SCR that had shown the highest anode-to-cathode jitter in Fig, 5-c,] Some pulses in Fig. 6-c started earlier and others slart- flG. 4— VOLTAGE WAVEFORMS viewed at 220-voll AC input; transformer pri- mary a, transformer secondary d, and motor armature {joad) c. (f FIG. 5— ANODE-TO CATHODE VOLT- AGES viewed at each bridge SCR (trig- gered at 90 into a positive p€ak supply voitage): SCR1 a, SCR2 SCR3 c, and 5CR4 ed later than the nominal times seen for the other three gate-to- cathode waveforms* Identifying the culprit A pattern had now been es- tablished linking the trouble to one SCR channeL It was next decided to determine the quali- ty of the output signals from tlic PLC, lb observe the PLC output lines* which are referenced to system/Earth ground, the black ( - ) lead of the difTerential probe was connected to system ground. Because 1 2 -volt logic signals were to be viewed, the differential probes attenuator was switched to 20:1 {12 volts/ 20 = 0.6 volt), and the o^s- cilloscope's vertical sensitivity ofO* I volt/division was selected. Three of the four 12- volt logic signals from the PLC to the SCR gate-trigger lines appeared nor- mal* as shown in Fig, 6-e* 64, and 6-h. However, the Fig. 6-g waveform was distorted by low- level reflected noise that tracked with the motors speed varia- tions. It was the same SCR channel that had shown gate- to-cathode electrical noise in Fig- That finding narrowed the cause of the problem down to one SCR channel and it was thought to be either a faulty PLC-to-SCR gate isolating trig- ger module or a malfunctioning SCR* A new plug-in module was then substituted for the one that appeared to be faulty and the problem was quickly solved. The differential probe dis- cussed in this article is sold in the United States by three dif* ferent suppliers: Avex Probes Inc, (API) as the Sl-9000: Test Probes. Inc*{TPl) as the ADF15, * 3V 1 1 i 3V 1 T 3V 1 11 . 3V d T" + 12V 0 412V 0 t 412V REaECTEO 0 — 4l2V ft ft RG, 6— GATE-TaCATHODE VOLTAGES viewed at the Input of gate terminais of SCRI to SCR4 a, b, c, and and output signals from the PiX a, b^ c, and d. PROBE SUPPLIERS Avex Probes Inc. (API) PO Box 1026 Bensalem. PA 19020 215-638-3300 CIRCLE 316 ON FREE INrOFIMATlON CARD Hewlett-Packard PO Box 612350 San Jose, CA 95161-2350 800-452'4848 CIRCLE 317 ON FREE INFORMATION CARD ITT Pomona 1500 East Ninth St. Pomona, CA 91769 714^9-2900 CIRCLE 318 ON FREE INFORMATION CARD Jensen Tools, Inc. 7815 South 46lh St. Phoenix, AZ 85044^5399 602-968-6231 CIRCLE 319 ON FREE INFORMATION CARD Probe Master Inc, 4898 Ronson Court San Diego, C A 92111 800-772-1519 CIRCLE 320 ON FREE INFORMATION CARD Tektronix PO Box 50 Beaverton, OR 97077 503-627-7111 CIRCLE 321 ON FREE INFORMATION CARD Test Probes, Inc, (TPI) 9178 Brown Deer Road San Diego. CA 92121 (616} 552-2090 CIRCLE 322 ON FREE INFORMATION CARD and Probe Master as the PM4230. For purposes of comparison, consider two other differential probes, the Tektronix P6046 and the Hewlett-Packard HP U41A/1142A. The Tektronix system consists of three sepa- rate cable- connected units: a probe head, an amplifier and an AC4ine operated power supply. It has a common-mode reject ion ratio (CMRR) of 10.000:1, an in- put resistance of I megohm, and an input capacitance of 10 p Ic o farads , I ts m ax 1 m u m ba nd- width is 100 MHz, and its max- imum DC plus peak AC is ± 250 volts. The HP 1141A differential probe is a 1 X FET differential probe with a 200-MHz band- width and a CMF'tR of 3000:1, The probe has an input resis- tance of 1 megohm and an input capacitance of 7 picofarads. It must be used with the HP 1142A probe control and power mod- ule system, R*£ FROM NotWorkiimg ^NETWORKING Bring your knowledge to bear on several tough LAN case histories. PARTS 1 AND 2 OF THIS THREE-PART series on troubleshooting LAN s presented technical back- ground on network tech- nologies (in Part IJ, and on tools and test equipment (in Part 21 This time we put our knowledge to work in diagnosing and solv- ing network problems of vary- Ing difficulty. In each case, we will describe the type of LAN, symptoms manifested, fault isolation tech- niques, use of test equipment* and repair methods, lb follow the discussion* It is important to have at least a basic under* standing of LAN technologies and test equipment as de- scribed in parts 1 and 2, So if you are unsure about anything discussed so far, reread those parts before continuing. The computer ate my work! This one happened at a local metal fabrication shop: the symptoms drove the company s finance people up the wall! That shop had five XT clones commu- n teat ing with an IBM PC- AT file server via Ethernet, For a long time, the network had been re- liable, but after several years of use. it began to run slower and slower whenever users ran order entry and accounting pro- grams off the file server. Error messages began to appear, and sometimes users had to repeat the process, TVouble shoo ting began when several people in the order entry department GARY McCLELLAN complained of trashed data. Several users were affected, so it seemed unlikely that their computers were at fault. That left the Ethernet backbone ca- ble and the file server as sus- pects. The backbone cable could have been the problem, but it didn't seem likely Then someone discovered that a sel- dom-used word-processing pro- gram ran fine, so we ruled out the possibility of cable fault. That left the file server and hard disk £is a possible culprit. That evening we shut down the network and ran a "disk doctor" program on the file serv- er. Those programs are available from several sources, including Symantec (Norton Utilities), Central Point Software (PC Tools), and Gibson Research (SpinRlte), What these pro- grams do is perform a non*de- structive low-level format of a disk drive. Typically such pro- grams work by reading a track of data from the drive, format- ting that track, and rewriting the data. Any bad sectors de- tected along the way get mapped out. and the data gets moved elsewhere, if possible. Figure 1 shows a sample screen from the Calibrate utility included with versions 6.x of the Norton Utll- Itfes. A related function often goes by the name o{ disk defragment- ing, which attempts to group logically related segments of a file together physically in con- secutive sectors of a disk. Doing so can dramatically increase the speed with which DOS reads files. A disk becomes frag- mented because, when a file is erased, DOS subsequently adds the now-unused sectors to a pool of sectors that might sub- sequently be reused. A par- ticular group of erased sectors might not contain enough space to hold an entire file, so DOS puts parts of the file In non-adjacent areas across the disk. The result is that when loading the program or data file, DOS sends the" read/write head all over the surface of the disk, rather than lapping up sectors one by one. That jerky head mo- tion can really slow things down. It is not unusual for over- all operation to be speeded up by 10-20% or even more simply by "doctoring * the hard disk, Nor- ton and Central Point both in- clude disk defraggers as well, Anw'ay running a disk doc- tor program on the fabrication shops server solved the prob- lem. Tb avoid that type of prob- lem, run a disk doctor program a minimum of every sbc months to catch bad cylinders and pre- vent data loss. If you encounter many bad cylinders, say 5% or more, you should replace that hard disk before a catastrophic failure occurs! The dead PC Many LAN problems go like this: A user cannot log onto the network, or a PC suddenly drops offline — but other users remain unaffected. Following are two examples of this type of problem, along with corre- sponding solutions. Example one occurred In a parts distributors office. The LAN consisted of five clone PC's and a generic 80286 file server tied together via ARCnct. ARCnet operates over RG-58 thin coaxial cable that runs from computer to computer First, we tested the sick PC off-line and found it to be func- tional. That left the Network In- terface Card (NIC) and LAN cabling as suspects. First we In- spected the coax cables and they looked good. But a gentle tug on a loose BNC cable connector caused it to come off. Replacing the connector brought the com- puter back to life. Generally speaking, con* nector faults are a major prob- lem on LANs. Most BNC connectors are cr Imp-on types, and if installed improperly, eventually they fall — but not be- fore becoming intermittent and causing lots of grief! Connector problems usually develop sev- eral years after their initial In- stallation; often they're caused by oxidation of contacts. For problem Installations, we prefer soldered to crimp-on BNC con- nectors. They take 5 to 10 min* utes longer to Install, but are far more reliable. Many connector problems are caused by users who acciden- tally damage cables by crushing them under chair legs, or drop- ping equipment on them. Our troubleshooting kit includes a collection of 10-foot cables which have coaxial BNC con- nectors, triple twisted-pair RJ-11 connectors, and quad twisted-pair RJ-45 connectors. The cables are for on-site sub- stitution of questionable ca- bles. Example two In this category concerned a dead computer in a medical billing office. The com- pany used five IBM PC*s linked by telephone-type unshielded twisted pair {UTP3 cabling into a Compaq 386 configured as a hub. The hub serves as both a file server and as a central point to which all cabling returns. We tested the problem PC, and it appeared to be working. U just wouldn't log onto the net- work. We substituted a different drop cable between computer and wall outlet: the new cable worked for a while and then quit. Next we substituted a PC from the office of a vacationing user* but without success. At that point the problem could have been anywhere, in- cluding the computer, its NIC, the cable plugged into the wall ouUet, or even the wiring back to the hub. First* we checked the old waU cable with the Paladin PatchCheck tester (discussed in the last article), PatchCheck checks cables in seconds, if you can access the modular plugs on both ends. Pin 2 showed a dim indication on the tester, suggesting high resistance. We didn't know which end was bad. so we replaced the connectors at both ends. The cable then test- ed good, so we reinstalled it and were able to log onto the net- work briefly But then trouble developed again. On a hunch, we pushed and held the modu- lar connector in the waU outlet. The user could log onto the net- work and work normally — until we let go of the connector. Then the PC crashed. Replacing the wall outlet solved the problem. In general, most twisted-pair cable problems are caused by bad crimps or by users pulling individual strands out of the connectors. In the present case, the initial installer used cheap connectors that probably were not crimped fully which in turn caused resistance to increase over time. As for the wall outlet, close inspection showed that the pins were partly covered by a greenish film, probably caused by moisture in the wafi corrod- ing the faulty gold plating on the pins. If you want to avoid a career in connector replacement you should always use qustlity cable and wall-socket connectors. Warehouse madBess The problems described so far represent roughly 80% of the faults you will encounter on computer LAN's, But there are other kinds of problems that will tax your troubleshooting abilities, and that also require specialized test equipment. Our next case is a good example. A firm relocated to a new headquarters 100 miles away leaving behind a warehouse. The new system used an IBM mldrange computer (at head- quarters) and CRT terminals and printers {in the ware- house), all connected via mod- ems and a dedicated telephone line. The purpose of this ar- rangement was to generate cus- tomer shipping orders. One day all the terminals and printers In the warehouse stopped cold. The data processing manager (DPM) of the company found that his equipment was not working properly, and he blamed the tetephone line. The local telephone company check- ed its line and pronounced it good! So where was the prob- lem? One possibility was that the fault was somewhere in the warehouse, between the modem and the outside line connections. With permission, we inspected the modem wiring in the telephone cable closet. It looked good* but then we mea- sured the line voltage with a DMM, It read zero! We had ex- pected 2 to 10 millivolts of AC noise, typical on a terminated line, A quick resistance check showed 7 ohms. There was a short in the wiring! We then spent several hours walking between modem and cable closet* disconnecting wir- ing, and eliminating various suspects. One look at the huge bundles of wiring on the wall of the building was enough to dis- courage fault finding by visual inspection! The solution was to use a time domain reflectometer (TDR), which can locate faults along the cable. After making sure the outside telephone line and modem cable were still discon- nected, we attached a MlcroTest Cable Scanner handheld TDR to the line in the closet. The TDR indicated some irreg- ularity about 70 feet away, which put the fault near the modem. Then we made another measurement near the modem end, and the cable scanner indi- cated a dead short. Then we traced the wiring into a storage closet where the red and white twisted-pair cable ran through a hole in a steel riser and up the wall. Close in- spection of the wires running through tlie hole revealed that a sharp edge had cut through the insulation and shorted the ca- ble. Insulating the wires with electrical tape brought the net- work back on-line. The problem of different or- NETWORK BACKGROUND The following am reference materi- als, equipment suppNers. and network- related standards organizatkins. References: • The Practical Guide to Local Ama Networks, Rowland Archer Osix)rne* McGraw Hill. Good inlroduction to cable types, topologies, artd access methods* • Neiworkir}g IBM PC's, Michael Durr, Que Cofpofalion. Chapter 14 contains good ovenflew of bridges, routers, and gateways. « LAN Magazine, 600 Hanison Street, San Francisco. CA 94107 (415) 905-2200. Suppfiers: • Black Box Corporation, P,0, Box 12800, Pittsburgh. PA 15241, {412) 746-5530, • Cable Express Corporation^ 500 East Brighton Avenue. Syracuse, MY 13210, (ai5) 476-31O0, • Coniaci East. 335 Wilto Streei South, North Andover. MD 01845. (508) 688*7829 • JDR Microdevices. 2233 Samaritan Drive, San Jose. CA 95124. (800) 538-50OO. • Jensen Tools. Inc., 7815 S. 46th Street. Phoenix. AZ 85044. (602) 968^6231. Standards Organizations: • American National Standards In* stitute. 1430 Broadway, New York, NY 10018. (212), 642-4900. • IEEE Headquariers. 345 E. 47m Street, New York, NY 10017-2394, (212) 705-7900. RESOURCES The following are addresses of man- ufacturers whose products were dis- cussed in this series of articles. Contact those companies for current pricing and more information. • F^adin Corporation, 3543 Old Corre- p Rd.. Newtjury Park. CA 92123. (800) 272-8665. • MiCfoTest, lnc.» 3519 E. Shea Blvd. Suite 134, Phoenix, AZ 85028, (800) 526-9675. • Radio Amateur's Han(iboof<, American Radio Relay League, New- tngton. CT 06111. • Tektronix, Inc., Redmond Division, 625 S. E. Salmon Dr, Redmond. OR 97756, (800) 833-9200. • AA^PJnc., RO. Box 3608, Harnsburg, PA 17105, (717) 561*6168. • Gibson Research. 22991 La Cadena Dr.. Laguna Hills, CA 926S3. (714) 830-2200 • Symantec Corp., Norton Utilities. 10201 Torre Ave.. Cupertino. CA 95014-2132. {408) 253-9600. ganizations blaming each other for faults neither can trace is common, because most LANs consist of different products from different vendors, includ- ing computersi terminals, printers, modems, NIC*s. ca- bles, and more. The solution is to leam about your LAN equip- ment and service it yourself, or find a trustworthy service firm that can do it for you. Cloak and dagger We saved the most fascinating LAN servicing case for last. After this case was resolved, someone must have answered some in- teresting questions about his late-night activities. Here's what happened: A soft- ware development firm became highly distressed when several of Its workstations performed intermittently in the middle of a rush project. The firm promptly called Its regular service compa- ny, which In turn concluded that there was a bad cable con- necting those machines and the rest of the LAN. The service company recommended tearing the old cable out of the wall and replacing it. After considering the cost of a new cable Inslalla- tlon. the firm asked that it be repaired instead. At this point we were called in to provide a second opinion. Wisely, the service company had bypassed the bad cable with a temporary one; thus wc could test the bad cable without shut- ting down the LAN, This net- work used a series of high-end workstations tied together via an ARCnet system into a mini- computer. A 60- to 100-foot length of coaxial cable con- nected the LAN with the last two workstations in the chain » We knew that the cable between them and the LAN was at fault. ^ We started troubleshooting by B making continuity checks on ? the wiring. Instead of an open 3 circuit, our DMM showed 10 r§ ohms between the shell and 01 center conductor of one of the | BNC connectors extending from 1 | the wall. a ' There was definitely a short in g li the cable. But where was it lo- ^ cated? Our initial response was to confirm the service compa- 67 OFF AC 1 : 1 i ! i i 159.2m ; : * I : : : 1 : ^ ill * : * ; fTin i ll :U . 1 ui : " : II r : i : ✓ • ; I I * * * ' I : : : : 1 : * * * i 1 ; 1 ! i * * " 1 . ' ' - ■ r * * ■ * ; ■ * » * ' 1 ■ • » : i : m OFF OFF OFF AC ; i : ] : ; 29.52mA : : : : : t : : * * I * 1 : : = ' i : I % I I r * • • * I ■ 4 « m r 1 : 1 ; 1 r : ; I * * % Y w * : : : : 1 : : -•^ , ^_ FIG* 2— A GOOD ETHERNET CABLE appears like this on a time domain reflectomoter (TDF^)» which shows fmpedance vs. dbtance. The vertical line In a marks the end of the cable. In the vertical line represents a bad cable tap. The TOR can "zoom" into the display, and c shows an expanded view of the bad tap. z n nys assessment, and to recom- mend tearing out the old cable. However, we first decided to do some troubleshooting. We rented a Tfektronlx model 1502C analog TDR from a local instrument rental company, (Rental is recommended any- time you need an expensive piece of equipment for just a few days,) We chose this premiere TDR because it displays minor faults that digital TDR's often miss. In the past we have lo- cated rusty connectors, loose connectors, and watersoaked cable sections with the 1502C. all of which w^re missed by a digital TDR. The dovm side of an analog TDR is that it re- quires more skill to use. The 1502C displays distance vs, impedance on an LCD screen. The display shows, along the entire length of the cable, a continuous "snapshot" of Impedance, which in our case was supposed to be about 50 ohms. Shorts cause the trace to drop to 0 ohms, and opens cause the trace to rise off the display. In operation, you look for suspect drops and rises, read the distance directly off the display, and start troubleshoot- ing at the specified location. Figure 2 shows several exam- ples of TDR displays. After connecting the TDR to the cable, we checked the dis- play» which showed the ex- pected 50-ohms. but with a sharp drop about 29 feet away A company manager, who had been looking over our shoulders, suggested that we check the celling* We lifted cell- ing panels and located the ca- ble. Since we had no idea of distance in the ceiling space* we guessed at the location and In- spected cable for some distance each way from our access point. Above a service closet we found the culprit. Someone had sliced the cable open and crudely spliced another cable to it. Upon closer inspection, we noticed that the added cable was pulled taut, causing strands from the uninsulated connections to touch. That, in turn, reduced signal levels to the workstations, causing Inter- mittent problems. With excite- ment» we traced the second cable into a closet where we found a computer and a printer hidden behind a row of shelves. We showed our findings to the manager. He said he would watch the closet and determine the identity of the eavesd ropper A week later he called the service company and had them remove the splice and replace it with a crlmp-on BNC connector and a barrel adapter. Later we heard that the computer had been re- moved from the closet » but the manager would not say whether he had caught the guilty per- son. If it hadn^t been for the short, we might never have dis- covered that illegal tap! H-E THIS ARTICLE LOOKS AT THE VER- satile 555 monolithic integrated timing circuit as an asiable multivibraton the illp-sidcorits capabilities as a inonostable multivibrator in time-delay cir- cuits, A recent article (Sep- tember R-E. pg, 58) explored tlie role of the 555 in the monosta- bie mode. Now youli find out how to build many different kinds of circuits with the 555 contigurcd as a self-triggerlng oscillaton You will want to build the cir- cuits that can generate a variety of square or rectangular wave- forms, wail like a police car. imi- tate the jarring he- haw sound of European emergency vehicles^ or reproduce the i^laxon alarm of the Star Treks' starship Enter- prise. The last article on the 555 as a monos table multivibrator in- cluded a functional block di- agram and an electrical sche- matic of the chip. You might want to refer back to those fig- ures if you want more detailed information about how the 555 is organized. Figure 1 is a pin- out diagram of the 555 as pack- aged in the most common 8-pin DIR It was pointed out in the last article that, although a ma- ture device, the 555 remains one of the most popular IC's available today At least five major semicon- ductor firms in the U.S, and Ja- pan make the 555, There is also a dual version, the 556, that has two identical 555 *s on a single chip. The device is usually pack- aged in a 14-pin DIR A quad ver- sion, the 558, has four inden- tical 555 's on a single chip, and it Is packaged in a 16-pin D!R The alternate source stippiiers usually include the numerals 55, 56 or 58 in their own desig- nations for those devices. The 555 occupies a strange position in the universe of inte- grated circuits. Classed as a lin- ear IC because it can be triggered either by linear or dig- ital signals, its output is always digital — in the form of rec* tangular or square waves or pulses. The 555 in a monostabie mul- tivibrator circuit (also called a timer, time delay, or one-shot) THE 555: A VERSATILE OSCILLATOR Learn how to build the 555 IC into osciilator circuits whose frequency you can change so they^li wail, warble^ and honk. RAY M. MARSTON generates a fixed-length output pulse for each trigger pulse at its input. This can be demon- strated with the circuit in Fig, 2. By contrast, the 555 in an astabie multivibrator circuit is shown in Fig. 3. It has no stable output states and no external 1_ GROUND 2 TRIGGER m OlSCKARGf 3 oirrpuT THRESHOLD 4 RESET CONTROL! VOLTAGE Astabie operation In the monostabie multi- vibrator circuit in Fig. 2, OUTPUT pin 3, DISCHARGE plu 7. and THRESHOLD pin 6 are held low when the circuit is quiescent. A monostabie timing period can be started by driving trigger pin 2 low with pushbutton switch Si, That causes output pin 3 to switch high, while DISCI u\RGE pin 7 is released and free to follow the voltage across CI. Voltage rises exponentially through Rl toward the supply FIG. 1— PrNOUT DIAGRAM OF THE 555, trigger is necessary to start cir- cuit oscillation; it is said to be self-triggering. This circuit con- figuration is also called an osciHator, signal generator pulse generator, or a rectangle- wave generator. As long as power is applied to the astabie circuit, the output continually switches back and forth between the high and low states at a regular rate or fre- quency The time in the high state (pulse width) and the time in the low slate (space length) depend on the selection of exter- nal resistors and capacitors. Be- cause of its relatively high output, the 555 in an astabie circuit can drive LED's. speak- ers, and meters directly. + 5VT0 + T5V -m Rl 22K 8 4 555 33#iF 22K HS1 START I- - \,< OUTPUT i 1 i FfG. 2 — MONOSTABIE MULTh VIBRATOR TIMING CIRCUIT based on the 555. ^ v^okai^e. Eventually the voltage at pin 7 rises to t\^'o- thirds of the supply voltage, and mono- stable action ceases with pins 3, % IP m 2! 69 6 and 7 grounded by the inter- nal circuitry of the 555. Examine the astable circuit shown in Fig, 3-a, in this circuit TRIGGER pin 2 is shorted to TMKKsiiOLD pin 6, aiid timing re- sistor R2 is wired between pin 2 and DISCHARGE pin 7. When power Is applied to the circuit, capacitor CI charges exponen- tially (as it did in Fig, 1) through resistors Rl and R2 until the voltage on CI reaches two- +5VT0 + 15V Rl IK ^: R2 a 4 5S5 I 1 oumrr OUTPUT M m 3 OUTPUT ACROSS €1 FIG, 3— A ONE-KILOHERTZ ASTABLE MULTIVIBRATOR based on the 555, and waveforms at output pin 3 and across CI are shewn la d. thirds of the supply voltage. At that time, monostable action ceases and discioirge ptn 7 re- turns to its low state. Capacitor CI then discharges exponen- tially into pin 7 through R2 un- til the voltage on CI falls to one- third of the supply voltage, and TRIGGER pin 2 Is activated. At that time, a new monosta- ble timing sequence is started and CI recharges to two- thirds of the supply voltage through re- sistors Rl and R2. The whole sequence then repeats itself over and over with CI alter- nately charging to two-thirds of the supply voltage through Rl and R2, and then discharging to one-third of that voltage through R2 only Notice that in Fig, 3-a, the val- ue of R2 Is very large with re- spect to tlie value of RL It turns out that the oscillation frequen- cy of the circuit is largely deter- mined by the values of R2 and C2. Figure 3-b shows the nearly symmetrical square output waveform that appears between OUTPUT pin 3 and ground while a nearly linear triangle waveform is simultaneously generated across CI. The grapii of Fig. 4 shows the relationship between the free- running frequency of the cir- cuit in Fig. 3-a and the capaci- tance values of CI w\ih the range of R2 values shown on the diagonal lines. In this graph the contribution of resistor Rl is neglected because it is a frac- tion of the R2 value. \ \ 1 to m IK 10K F. Fn^-CU/NlltNG RHWCV (Hi} lOQK FIG. 4-THE FREE-RUNNING FRE- QUENCY OF OSCILLATOR In Fig. 3 as a function of capacitance values for C1 and tfie resistance value of R2 (when large with respect to Rl)* FIG, 5— THIS SQUARE-WAVE GENER- ATOR produces a variable frequency of 650 Hz to 7.2 kHz, FIG. 6— AN STABLE MULTIVJBRATOR with independent pulse width and space penods variable from 7 to 7S0 mlcrose* conds. FIG. 7— ALTERNATE VERSION OF OS- CILLATOR shown in Fig. 6. The values of Rl and R2 can be varied from 1 kilohm up to tens of megohins. Resistor Rl can, however, have a significant effect on the total circuit cur- rent consumption because pin 7 is essentially grounded during half or the oscillation cycle. The duty cycle or pulse width-to- space ratio of the circuit can be preset at a nonsymmetrical val- ue Jf desired, by the choice of Rl and R2 values. The high time (pulse width) and low lime (space length) in this circuit must be calculated separately The pulse width cal- culation includes the values for the timing capacitor CI and both timing resistors Rl and R2, By contrast, the space length formula includes only the values of timing capacitor CI and resistor R2. Refer to Fig. 3-b. Pulse width (or time to charge capacitor CI is: tt - 0,7 CI (Rl +i^2] Space iength or time io dis- cliarge capacitor CI is: t.^ = 0.7C1R2 The total cycle time is: T - t, +tj The ratio of pulse undth to the total cycle time Is the duty cycle. In a 555-based oscillalon tlie duty cycle is defined by the rela- tive values of the two timing re- sistors Rl and R2: Duty cycle = R2/[R1 -!-2R2) Frequency in hertz (Hz) is the reciprocal of total cycle time: F = l/T, Tiie circuit in Fig. 3-a can be modified in many different ways. Figure 5, for example, shows how it can be made into a variable- frequency square- wave generator by replacing R2 with a fixed resistor and polentiome- ter in series. The frequency can be varied over a range of about 650 Hz to 7.2 kHz with the val- ues of the resistor and potenti- ometer R3 showTi. If required, the frequency span can be fur- ther increased by switch-select- ing alternative values of 01. R3 IDOK Dt 1N414A 1fM14S* .Of IK -w — r fK 555 .01 OUTPUT i RG. 8— A 1,2 kHz OSCILLATOR with a duty cycle vadatite trom 1 to 99%. Widiii-space control The circuit in Fig. 3-a can generate a fixed-frequency out- put waveform with any desired pulse widlh-to-space iength ratio by selecting tlie appropri- ate lvalues for Rl and R2. In each operating cycle, CI aitemately charges through Rl and R2, and discharges only through R2. For example, if Rl and R2 have equal values, the circuit will generate a 2:1 width-to- space ratio. The widih-to-space periods can be independently con trolied with either the Figs. 6 or 7. in Fig. 6, CI alternately charges through RL diode DL and po- tentiometer R3. and tt dis- charges through potentiometer R4, diode D2, and R2. In FSg. 7, CI aitemately charges through Rl, potentiometer R3, and di- ode Dl, and it discharges through potentiometer R4, di- ode D2. and R2. In both Fig, 6 and 7 circuits, R2 protects tlie 555 if potentiometer R4 is shorted. IK i t)2 ir >1K» R3 100K 01 S55 1 JTP i OUTPlfT FIG. 9— AN ALTERNATE VERSION OF OSCILLATOR shown in Fig. B. + 5VrO + l5V ; ^ C3 B1 2M D1 1H4143 — W— R2 t.lK m IK R4 75K 555 'Z^X T?! OUTPUT 1 ' 1 FIG. 10— A PRECISION LOW-FREQUEN- CY OSCILLATOR with a frequency of aboyf 20 Hz. In the circuits of Figs. 6 and 7, the width'to-space periods can be independently varied over about a iOO:i range, en* abiing the width-to-space ratio to be varied from 100:1 to 1:100. The oscillation frequency varies as the ratio is altered. Figures 8 and 9 show alter- nate ways of connecting the 555 in the astable mode so that the width-to-space ratio can be var- ied wiliiout altering the oscillat- ing frequency In those circuits, the pulse width period automat- ically increases as the space length period decreases, and vice versa. Therefore, IItc total period of each operating cycle is constant. In those circuits* the feature of interest is the duty cycle, in Figs. 8 and 9, the duty cycle can be varied from 1% to 99% with potentiometer R3. in the circuit of Fig. 8, CI al- ternately charges through RK the upper half of R3. and Dl, and It discharges through D2. R2. and the lower half of poten- tiometer R3. In Fig. 9, CI alter- nately charges through Rl and Dl and the right-hand half of potentiometer 1^3, and it dis- charges tlirough the left-hand half potentiometer R3, D2, and + 5VTO+15VJ Rl IK ,0t fl2 75K 555 1 I I i 1 R3 SI 1 OUTPtlT i 1 r 1 ov; _ -■ /. V 1 OUTPUT^ AT PIN 3 txnpuT ACROSS CI --*KSt CLOSED $1 OPtfl b SI OPEN FIG, 11— GATED 1-kHz OSCILLATOR of- fering "press-to-tum-on'* operation, a, CFHB and waveforms at output of pin 3 and across Cl^ +SVTO + ISV R1 tK -01 75K 555 I OUTPUT i OUTPUT J^PIN3 SI CLOSED ft RG. 12— GATED t-kHz OSaLLATOR Qi- ferrng "press*to*turn-off" operation, a, and waveforms at output of ptn 3 and across Ct, m SS5 OlfTPUT S1QfB« -$1 CLOSED SI 0PEI4 RG. 13— ALTERNATIVE GATED 1-kHr OSCILLATOR offering 'press*to*turn* on'' operation, a, and waveforms at out- put of pin 3 and across CI, R2. Both circuits oscillate at about L2 kHz with the value of CI shown. Precision astable circuit In the description or astable multivibrator operation given earlier in this article, it was stated that in the first halfcj'ele of oscillation liming capacitor CI charges from zero volts to two-thirds of the supply voltage* but in all subsequent half-cy- cles it either discharges from two- thirds to one- third of the supply voltage or charges from one-third to two- thirds of that voltage. Consequently the first half cycle of oscillation has a far longer period than all subse- quent half cycles. ifSVTQ+ISV f f iWTO ♦ 15V (SEE TEXT) Rt IK 6 5S5 R3 ^ IK |5 h CI ^ €2 I Qy-fp 1 OUTPUT OUTPUT ATpma ^S1 aos€Dh- FIG, 14— ALTERNATIVE GATED 1-kHz OSCILLATOR offering ^ pre ss- to- turn- off" operation, Ta and waveforms at out- put of pin 3f t. In applications calling for a low- frequency clock signal, this large differential in period can cause a timing problem. How- even this problem can be aver- ted by adding an external voltage divider and diode as shown In Fig, 10. Those compo- nents bias CI to a point slightly below one- third of the supply voltage (rather than zero volts) at the moment of switch-on. Here. Rl rapidly charges CI to one- third of the supply voltage through Di at switch-on. and all of the CI charge is subsequently controUed by R3 and/or R4 only 1 — ■ — siaostc ^ OPfH OUTPUT ourpuT Acnoss -SI OPItt FIG. 1&--PRECiSiON VERSION OF THE OSCILLATOR in Ffg. 13, and wave- forms at output of pin 3 and across 01, Astable gating The 555 in the astable multi- vibrator mode can be triggered ON and OFF in many different ways with either an elec- tromechanical switch or an electronic signal. The most pop- ular way to trigger the 555 is through re;skt f3in 4. Figures U-a and l2-a show alternative ways of triggering the 555 with this pin and pushbutton switch SL The 555 is organized so that if pin 4 is biased above about 0.7 volts, the astable mode is en- abled. But if it is biased below 0,7 volts by a current greater than 0-1 milliampere (by grounding pin 4 with a resis- tance less than 7 kilohms. for example) the astable mode Is disabled, and the 5551s output is biased low. For example, the circuit In Fig. 11-a Is normally turned off by R3, but it can be turned on by closing pushbutton switch Si, which biases pin 4 high. Figure 12 -a shows an astable circuit that is normally on, but it can be turned off by closing push- button switch Si, which shorts pin 4 to ground. The circuits in Figs. 11 and 12 can also be trig- gered by applying suitable elec- tronic signals directly to their *5VT0+1SV R1 .01 R2 75K 555 MODULATIDN INPUT I -O t OUTPUT i PULSE WIDTHS VARIABLE OV 1 r Y 4^ OUTPUT M PJfJ 3 SlWCES EQUAL Fia le^iRCurr for applying ac- COUPLED FM or PPM to a 555 config- ured as an oscillator, a, and waveforms at output of pin 3, b. FIG. 17— CIRCUH FOR APPLYING A DC- COUPLED FM or PPM to a 555 config- ured as an oscillator. FIG. 18— CIRCUIT GENERATES SOO-Hi MONOTONE ALARM that operates rrom 750-mllliwatts, ^ 14- m ^ 01 03 FIG. I^CIRCUIT GENERATES BOO-Hz MONOSTABLE ALARM. tion of CI and R4 close to zero volts through R2 preventing os- cillation. When pushbutton switch SI is closed. Q) is biased off, and the astable circuit is free to oscillate norinaUy* Refer to Fig. 13-b for the wave- forms of the circuit in Fig. When the astable response Is triggered on» the first half cycle is again considerably longer than in succeeding half cycles, and that the voltage on CI de- cays rapidly to nearly zero volts when the trigger is off. Also notice that output pin 3 is high in the off state. Figure 14 shows how the cir- cuit in Fig. 13-acan be modified to give pness- f o-furn-o/r oscilla- tion simply by replacing Ql with a pushbutton switch, A digital signaJ can trigger this circuit if a diode is connected as shown in the diagram and the push- button 51 is deleted. With SI re- moved, the circuit will be turned off when the Input sig- nal voltage is reduced below one- third of the supply voltage. The waveform is shown In Fig, 14-b. Finally, to complete this look at triggering techniques. Fig, FIG. 20— CIRCUIT GENERATES SOO-Hi PULSED*TONE ALARM. RESET pins. In Fig. 11-b, the precise cir* cult waveforms at output pin 3 and across CI are shown, it can be seen that the duration of the first half-cycle of oscillation is considerably longer than the succeeding half cycles because of the time for Cf to charge to two*thirds of the supply voltage. Also, note that when the astable mode is turned off, the CI volt- age decays slowly to zero: the output at OUTPUT pin 3 is zero volts in the off condition. The waveform characteristics of Fig- 12-a are similar as shown in Fig. 12-b. Figure 13-a shows an alter- native method for triggering the 555 In the astable mode. Here transistor Ql is normally biased ON by RL so it acts like a closed switch, which pulls the junc- IS-a shows how the Fig. I3*aclr* cuit can be modified so that the duration of its first half-cycle is almost equal to that of all suc- ceeding half-cycles, thus giving precision operation. In the Fig. 15-a circuit, when pushbutton switch SI IS open, Ql is satu- rated, so the voltage divider made up orR2 and R3 puUs the junction of R5 and CI to slightly below one- third of the supply ^ — ^■ f f — R1 . iok: 04 R2 75IC IC2 S55 CI : tOMF T T ^'T 4 i 1^ lOK R4 220K D1 1N4D01 R5 OK it Z 6 IC1 555 C3' .01 SPKR1 8 a R6 D3 4> FfG, 21^IRCUIT GENERATES WARBLE ALARM of European emergency vehicles. f- f T M- + 12VTO + 15V R1 4jK: :C3 7 (► — 6 1C2 555 m TOK Dl 1II40O1 02 1D0K ^—7 01 rci 655 IT R6 2.7Kn R7 1200 SPKR1 03 02 2H30S5 FIG, 22— CtRCUrr GENERATES SIREN WAIL of poirce cars. — T ? — f f — f- R4 < i R2 IC2 555 ft3 12K 01 zmroz ^ n SPKR1 555 "1 ^ CT Z7K 03 03 47mF .01 " HI 2113704 i 4 — ^4 4 R5 lOK s t N- D2 1N4Q01 + T2VTO+15V 03 -- tN4Qai RS 2011 04 1N4O01 RG, 23.— CIRCUIT GENERATES PENETRATFNG ALARM of Star Trek spaceship. voltage through diode Dl, thus turning the circuit off. When SI is closed, Ql turns off. Dl is re- verse biased through R2, and the circuit is then free to oscil- late normaUy. Notice in Fig, 15-b thai when SI is first closed, CI starts to charge from an initial value of almost a third of the supply volt- age rather than from zero volts. Therefore, the duration of the initial half cycle is similar to that of all the succeeding half cycles. Modulation techniques All of the 555 astable circuits reviewed so far can be frequency or pulse-position modulated (FM or PPM) by Iceding a suit- able modulation signal to coNi ROL VOLTAGE pin 5, vvhlch is connected to part of the internal voltage divider chain of the 555. The AC modulation signal is fed to pin 5 through a blocking ca- pacitor, as in Pig, l6-a. or the DC modulation signal can be fed directly to pin 5, as shown in Fig. 17. The voltage on pin 5 of the Pig, 15-a circuit alters the width of the pulses in each timing cy- cle of the 555, but it has almost no effect on the space duration. The signal at pin 5 changes the PPM pulse width position, af- fecting the total cycle period so it also inlluences the output fre- quency, as showni in Fig, 16'b. In so doing, pin 3 provides a fre- quency-modulated signal- Those characteristics of the 555 are useful for generating special waveforms. Alarms and sirens Some of the most popular ap* plications for the 555 organized as an astable multivibrator are as waveform generators for loudspeakers. They can pro- duce alarm and siren sounds. Figures 18 to 23 show difTerent wa>^ to create those sounds. All of the circuits in those figures are triggered by making or breaking their supply- volt age connections. Figure 18 shows an 800-Hz monotone alarm-call generator circuit, which can be powered by any 5- to 15-volt DC supply. The speaker SPKRl can have any impedance value. Note* however, that Rx must be wired in series with any speaker whose total impedances is less than 75 ohtns. Select a resistor to give a total series resistance with the speaker of 75 ohms. continued on page 94 JAMES MELTON DO \X)U EVER NEED TO rO\V>:!^ 120 volt ac equipment when there is no AC outlet available? Our af- fordable power inverter was de- signed to supply up to 250 watts lo power line-operated equip- ment a a fraction of the cost of commercially built units. The inverter described here has been used to power Hood lamps, soldering irons (both re- sistance and transformer types), fans, televisions, and portable computers. It has even powered an air pump for the au- thor's asthmatic son. The inver- ter will power almost any device that runs on 120 volts AC, Some motorized devices won't work well however* A variable-speed drill may work, but only at one speed. Fans and other purely in- ductive loads seem to run at about % normal speed with the inverter Synchronous motors will run at normal speed but will be a little "noisy/' Power FET's to the rescue Power FET (field eflect tran- sistor) devices have gotten more versatile over the last few years and, at the same time, the prices for them have plumm- eted. No tiling can match a FET in Its ease of interfacing with logic signals, and for the ease in which it can work in parallel with similar devices without the need for any extra compo* nents. To parallel the FET's. all you have to do Is tie the source leads togetlien When the they get warm, FET's exhibit a positive temperature charac- teristic, which means as the temperature goes up. so does the resistance: as the resistance goes up, the current through the device is lowered. That makes FET's self-limiting when working in parallel. FET's are now being produced with power ratings that can often make parallel operation unnecessary* The ratings for the 1RFZ30S that are used in this project are amazing: they can handle a SO-amp load with 50 volts across the source-drain leads and 75-watt power dis- sipation, all in a TO-220AB plastic package — for less than two bucks each when pur- chased in small quantities. Operatioa Figure 1 shows the schematic of the Inverter, A 555 timer. ICl, along with R3. R2, and C2, gen- erates a 120-Hz ( ± 2 Hz) signal, as set by the value of potentiom- eter R3. The output of ICl at pin 3 is fed to the clock input of a CD4013BE dual D-type flip-nop. lC2-a. which is wired to divide the input frequency by two: that generatea the 60-Hp. clocking for the FET array {Q1^6), The output from nip-flop lC2-a at pin 1 has a 50% duty cycle, which is necessary for the out- put LransFormer, Tlie nip-flop also provides an inverted out- put (Q, pin 2), which saves us from having to add additional components to invert the q output. The second half of IC2 (iC2-b) is not used, so all of its input pins are grounded. The Q and g outputs fmm 1C2- a are each fed. via R5 and R4, to three inputs of IC3, a CMOS CD4050BE hex buffer. Each group of three buffer outputs drives one bank of FETs in the power stage. Power small appliances from your car or any other 12'Volt source with our 250-watt inverter. 250 WATT POWER INVERTER ri 20 MIPS C2 , 02 1K4751 13V D1 tN4D01 1 ^ S> Si ^SQUARE WAVE) m 33K R3 50K a DISCHARGE ICI 555 THRESHOLD TRIGGER HItSET -^CLK 0 dciR - CB4I]13BE Q 0 R5 4.7K V4 CtMOSQBE < SET ^Q2-b 11 10. CLK "'^ -C CLR R4 4:7K 05 1H314 Qt IBFZ30 02 03 06 1KSU Q4 Q5 06 mFZsa 7 Ii4r^i5 i C04050BE D4 tmm D3 — H— FIG. I'-INVERTER SCHEMATIC. A 555 timer (ICI) generates a 120-H2 signol that is fed tea CD4013eE flip-flop (]C2-a} which divides the Input frequtncy by two to generate a BO-Hz clocking frequency for the FET array (Q1-Q8). The Inputs to the buITers are also controlled by D5 and D6, which are connected to the drai* ns of the FETs so that the array that is turned-on essentially heis control of the drivers of the opposite array* When one side Is turned on arid lis drain Is at ground potentiaK the other side cannot turn on because the in- put to the buffer for that array is also being held at ground. It stay^ that way until the control- ling array has completely ^ turned off and the drain voltage a has gone above about 6 volts. That is necessary because the o turn-off time for a FET is longer S than Its turn-on time. If the di- g odes were eliminated, both ar- z rays of FET's would be turned 3 on simultaneously during each o trans ist ion. which creates tre- B mendous spilies on the battery* m the equipment tied to the out- put of the inverter, and to the 76 FETs themselves. The FET array can be made as big or as little as your applica- tion requires. The author needed at least 250 watts, and used two IRFZ30's in parallel for each array. Howevcn to play it safe, use three in parallel (or however many you need| for each array as we ve shown In the schematic- Diodes D4 and D3 dampen Inductive kickback from the transformer winding that would likely cause over- heating and premature tran- sistor breakdown. Power-supply conditioning circuitry (Dl. RK D2. and CI) eliminates spikes, overloads, and other noise from a cars 12- volt supply. Even though the 555 can handle up to a 15-voli supply, power-supply spikes will surely damage it. If the transibrmeryou use has a center tap. the center tap must be connected to the 12- volt line and the two 12-volt windings must be connected to the drains of their respective driving tran- sistors. The author used a Jefferson buck/boost trans- former that's normally used to reduce or increase the line volt- age for AC devices. If you are going to buy a transformen you can use any center-tap 24-volt or dual-winding l2-volt trans- former. It is important to use a transformer that can supply tlte ammount of current that your application requires. Construction Some of the components mount on a small PC board, for which weVe provided the foil pattern. The parts-placement diagram is shown in Fig. 2. We recommend that you use sock- ets for the ICs. After soldering all components on the board, apply 12 volts and measure the frequency on the pads marked J4 and J2. Adjust R3 for a read- 120 OUT fSOUARE WAVE I ; WINDING TWO ♦ \ r # ; g WiNDIKGOfJE n r n n " ri 05 lb A I i | 3 D IS R n w n ) IC3 ^ s B [3 ^1 rr J2€ JSC ) fCT ri r n T r R3 fl2 CZ i 1 0>i 05 06 D3 , I OT 02 T 03 ct D2 Fia 2— MOST OF THE COMPONENTS mount on a small PC board. The off^board components can be mounted on a terminal strip of perforated construction board. ing of 60 Hz, and make sure the voltage is very close to Vi o{ the supply voltage on each pad. That tells you that your dutv cy- cle is 50%. Now connect the rest of the components. The small off- board components can be mounted on a terminal strip. However, be sure to mount the FETs on a heatsink. If the heat- sink is at ground potentiaL also be sure to insulate the FETs from it. ^^^^^^ 1^ X FOIL PATTERN for the Inverter board. PARTS LIST All resistors are Vi-watt, 5%, un- less otherwise noted, Rt— 60 ohms. 1 watt/10% R2— 33.000 ohms R3— 50.000 ohms. 10-tum potenti- ometer R4, R5-4700 ohms Capacitors CI— 220 35 volts, electrolytic C2— 0.1 50 volts, ceramic cfisk Semiconductors 1C1— LM555 timer 102— CD4013BE CMOS dual D- type flip-fJop ICS— CD4050BE CMOS hex buffer D1, D3, D4— 1N4001 diode D2— 1N4751 IS-volt Zener diode D5. D&-1N914diode Q1-Q6— 1RFZ30 30-3mp, GO^volt FET Other components Tl— Jefferson #216-1121 buck/ boost transformer (contact WW Granger. Inc., 1250 Busch Pkwy. Buffalo Grove, IL 60015, 708-459-5445} or other 12- or 24- volt center-tapped transformer (see text) SI— SPST switch F1 — 20-amp fuse (or use value ac- cording to desired oLftput cunent and transformer used) Miscellaneous: fuse holder, cab- inet, mounting hardware, AC out- let, car cigarette lighter plug, wire, solder, etc. FIG. 3— THE PROTOTYPE INVERTER. The author used a car cigarrette lighter plug on the end of the power-input lead and an AC outlet for plugging appli- ances into. ■Ik FIG, 4— THE FET'S ARE M0U^fTED on metal pfates used as heatsinks. If the heatsink Is at ground potentiaL Insulate the FETs from the heatsink. The author used a car ciga- rette lighter plug on the end of the power-input lead, but you are free to use aUigaior clips or whatever is most convenient for you. A stand^ird AC outlet was mounted on the front panel of the unit. The prototype was in- stalled in an old, rugged metal case, but you can use whatever you have on hand. Figure 3 shows the prototype inverter and how everything is as* sembled. Figure 4 shows a close-up view of the FETs and how they are mounted on metal plates used as heatsinks. Operation lb operate the unit, plug the input power into your cigarette lighter socket, turn on the I>ower switch, and turn on the appliance that's plugged into the inverter When you are not using the inverter be sure to turn it off, since the trans- former will draw about 2 amps even with no load. That will drain your car battery fairly quickly! R-E AUDIO UPDATE Syndicated Reviewers, AM Stereo, and Consumer Fraud LARRY KLEIN I've frEquently been dislrBSsed by the writings of the syndicated audio columnists, the pundits whose opinions appear weekly in large and small local newspapers. IVe met nr^any of them over the years and. by and large, they are nice people, but I just don't like the job they do. What's wrong? Several things. I feel stnongfy that a writer should not express his opinion in print on the audio qualities of a borrowed product listened to under uncon- tnolled conditions in a home environ- ment. Such home evaluations without lab test backup are, in gen- eral. untrustworthy. They actually teJl you far more about the writers mood, health, and relationship with the manufacturer than they do about the product. This is not to say that some of the recommended products aren't topnotch, but the reader has no way — sound un- heard—of confirming the reviewer s opinions. Am I being loo harsh in my judg- ment? I think not. The temptation to say nice things about a product be- comes intense when a writer has been personally wined, dined, junketed, and brainwashed by a company's public relations agency I can say that in the 35 years or so that I've been writing atx>ut audio I've kept my skirts relatively clean. Despite temptations to do other- wise, I have never confused my sub- w jective opinions with objective facts S and never praised a hi-fi component i In print without a lab test backup. I 5 should admit that as the technical O director of the worid s largest cir I" culation audio magazine, 1 found it ^ easy to be hoJter than almost any- "p body t regulariy received such man- S ufacturer-supplied perks as all- S expense-paid annua! trips to audio shows and factories in Japan, Eu- 78 rope, and elsewhere, and all the long-term-loan audio equipment I could use without extolling the vir- tues of anyone's products. Free- lance writers, on the other hand, inevitably find themselves in a quid pro quo situation. The amount of laudatory "ink" they give to prod- ucts in their columns correlates di- rectly with the frequency of invites to press junkets. Their columns and comments are reprinted by gratified manufacturers, and they are on the "A" lists for goodies. Once I left SterBO Review for the freelance life, my invitations slowly dwindled as the various PR agen- cies became aware of my new unex- alted status. I could have reversed the situation somewhat by taking the same product review route as my syndicated contemporaries, but I chose not to do so. In any case, to reaffirm my point: Be careful before committing your dollars on the basis of any opinions unsupported by lab- oratory testing. Its just too easy to be mislead. AM stereo Remember AM stereo? it s an idea that won't die — but won't come fully to life either Perhaps a dozen years ago, when AM stereo was first introduced as a new broad- cast technology, I wrote that be- cause of the lack of consumer interest the format would probably never fly. The letters of drsagree- ment that subsequently reached my desk were mostly from station owners, broadcast engineers, and companies with investments in AM- stereo technology. For years there was no visible pnDgress on the AM-stereo front, possibly because the FCC in its wisdom Cha!) decided to let the competing formats fight it out in the marketplace. True, there was an oc- casional press release telling of this or that company's home or car re- ce'rver*s having AM-stereo recep- tion facilities, usually Motorolas system. A mini breakthrough almost oc- curred in June 1990 when the Na- tional Association of Braadcasters (MAS) and Denon announced a "comprehensive component broad- cast monitor tuner that does it all." The "air* included the now-defunct FMX FM noise-reduction system. AM stereo (Motorola "s C-Quam). and the newly promulgated NRSC AM standard. The new standard in- cluded an extension of the AM tun- ing range (520 to 1710 kHz), a pre- emphasis/de-emphasis curve, and a vsrtden lightiy specified audio band- width. The tuner was pnDmised for "eariyl991."" I recent!y called the Denon tech- nical rep to ask what, if anything, had happened to the tuner He faxed me a copy of a press release dated May 1992 announcing a revised tuner that no longer had FMX but did have AM AX. which seems to be the NRSC parameters under a new name (See Radio-Electronics, February 1992 for more details). The AM bandwidth can be switched to wide or narrow, providing either the broadest audio-frequency response or the lowest noise. Helping to re- duce AM impulse noise is a notse- btanking circuit from Sprague/Alle- gro Microsystems. 1 found the tuner s technical spec sheet, which was printed in Japan, to be somewhat puzzlmg. The audio frequency response of the AM tuner set to wide is given as 50 Hz to 7,5 kHz, +1.5 -3 dB. Certainly that s better than what one finds in most AM/FM receivers, but it falls far short of CD quality. The claim has been made that good AM stereo is frequently indis- tinguishable from FM. That may well be, given the aging ears of the clas- continued on page 96 HARDWARE HACKER Histogram equalization, alternate action latches, gamma curve correction, digital image processing, and semiconductor IC houses. DON LAHCASTER Stop the presses. Murata has jusl announced a Gyrostar piazo gynDScope. Which, rf it rs as gmat as it looks, coufd easily beconne the hacker component of the decade. All I've got on this so far IS that brief note in the June 8th Design News and a promise for more technical information. Need- less io say the hacker potential of a $5 navigation gyro would be truly revolutionary. Be sure to stay tuned on this one. Things are also starting to happen fast and furious on that direct'toner printed circuit board front. Since my last report, the new water-soluble decal-based Toner Transfer System offered by Dy^iaArt has been further improved. The new Printed Circuit Board Transfer Film from Techniks looks even nnore promising. What Techniks did was take their old differential transfer system and add a new blue polymeric release coating. The polymeric release coating can dramatically improve the transfer: it actually becomes an important part of your resist pattern. Faster than light? Every week or so I get at least one letter or helpline call from peo- ple who feel they have clearly broken some physical law. Maybe they have proof that the speed of light is not a constant. Or that those three laws of thermodynamics just do not apply to them. Or that per- petual motion can be possible using magnetic repulsion. Or they have lapped the zero point scalar energy from the fabric of space. Or that their latest pet theory pru\^s the cold-fusion process, Usually, they'll also complain that they've sent their theory every- where and have gotten no replies. Or that th^ arB getting ignored be* cause they are outsiders. Very often, their inquiries will be self-defeating. How? They will in- clude totally irrelevant religious or political contexts. Or they* II be super secretive. Or written and sub- mitted in such a way that they scream "Hey, kick me. for Tm not even computer literate/" If it likes water looks like a duck, and quacks like a duck... But consider who is receiving those letters. Based on past experi- ence, the editors or the publishers know that the probability is 0.99 H- that the lab work Cif any) is just plain wrong. Or more typtcally not even wrong. And 0,99 that the sendee is clearly a few chips shy of a fult board. Why should they believe you? The sad thirig is that needle in the haystack. Tm going to be generous and claim that one letter in 500 in fact does have the germ of a new theory or a developable product or a fresh look at a solvable problem. And, yes, newer ideas often will get ignored or vehemently attacked. What can you really do if you have genuinely beaten those overwhelm- ing oddsandyour controversial idea is in fact both new and for real? There are tvw3 possible routes you could take to get your ideas accept- ed. The first or mat science method is to thoroughly try and pra^ that you are wrong. Be sune to use lots of careful research, especially through Dialog and those UMI reprints. Be certain to subscribe to all of the rele- vant insider trade journals and go NEED HELP? Phone or write your Hardware Hacker questions directly to: Don Lancaster Synergetics Box 809 Triatcrier. AZ 85552 (602) 428-4073 out of your way to study the schol- arly publications in the field- Learn all the lingo. Attend conferences and trade shows. Find a patient and knowledgeable industry insider that is willing to look at your idea and comment honestly on it- Be absoiutety certain that you have B simple experiment that can be independently duplicated and verified by disinterested outsiders. Hire some competent engineer- ing or physical science consultants to study and add credibility to all your claims. Take enough college and university level courses to make sure you do thoroughly understand at least the fundamentals of the field — along with the needed math to back it up. And finally* present the ideas clearly identified as a possible new theory tn some professional context totally free of religious* polittcai or any conspiracy mumbo jumbo. The second route is to publish via a pseudoscience press. There are quite a few underground and alter- nate life publications that welcome materia! of this type. Every now and then. Whole Earth Review gives you a list and rundown of all the maga- zines of that genne. Let me know if you want to see a resource sidebar on those. One leading bookstore that does specialize in selling and distributing pseudoscience topics is High Ener- gy Enterprises. Many of their offer- ings are utterly fascinating. Those ^ folks also sponsor several yearly ^ forums where controversial ^ pseudoscience topics are strongly g encouraged- Several very important tips when |" publishing your own pseudoscience g tracts: Be sure to use cut-and-paste b Xerox*of-a*Xerox and lots of poorly ^ printed sloppy layouts. Smeared ink 1 on cheap paper is a must. Freely quote obscure rural newspapers as 79 your prime data sources. Include il- legible artwork. Extensively refer to unheard-of and unavailable ioumals. Use plenty of irrelevant inference and innuendo. Use only 20-200 year old refer- ences, especially in any rapidly changing field. Misquote and drop some big names, even if totally out of context and they never heard of you, "Billions and billions of Carl Sagan's ago..." Never offer any succinct and easily van f ted experi- ment. Always use ten words where one will do. Make alt of your paragraphs unbearably wide and long. Then run them all together rn haphazard order. Never come right out and state your key points. Work Tesia in somehow, and be sure to include plenty of obscure religious and/or political references. Show how your theory is now being suppressed by a federal conspiracy headed by the Trilateral Commission and secretly funded through both the WCTU and the SPCA, Ignore all the personal computers entirely They are only a passing fad that never will catch on, Finaliy do NEW FROM DON LANCASTER HARDWARE HACKER STUFF Kartfvwaro Hacker Rcprirtli H or HI £4.50 Uklnlght Engtniicrlng fleprlnts Inmd tbiflSocreiMonoyMachmo 18.50 CMOS Cookbook 24.50 TTL Cookbook 24.50 Actlvo Filler Cookbook 19.50 Micro Cookbook vol I or II 19.50 Unc^istor ClQftsIc! Library tId.SQ ApploWrUor Cookbook 19.50 POSTSCRIPT STUFF Ask Th« Guru Reprints I, II or lU 24.50 LBset WrI (■ r S«crc ts {i l«/U«c/PC> Z9.SD FoilScrlpI Stiow & Teli 39.50 Intro to Po t ts c ri pt V H S Vldoo 39.50 PostScript Btginner Styfl 39.50 Pos tSc rip t C ookbook ( Adobe ) 1 S .50 PostScript Rer Manual M (Adobe) 21.50 PostScript Prog ram Design (Adobe) 22,50 Type I Fon! Format (Adobe) 15.50 LaserWritor Perorcnco (Applo) 19.50 Real World Poatacrtpt {Roth} 22^50 PostScript Visual Approach (Smith) 22.50 Thinking In PoslScftpl (Rold) 22.50 Undgt PS Pgrmmg {Ho1t2gang} 29.50 The Wholo Work s ( a 1 1 Posts cripl ) 349.50 BOOK-OM-DEMANO STUFF Book-on-dontand rosoufco kit 39^50 GEnle PSRT s imp lor (llo/Mac/PC) 39.50 FREE VOICE KELPLiNE VISAJMC r[KH 1 Clear (A) Relay convertecf to latch. > I- i Clear JE. Set (B) Inverter pair used as laicfi. {C} Alternate action pushbuLlpn. FIG. 1— SOME SIMPLE UVTCHES and alternate action circuits. not ever, untder any circumstances, use any new desktop publishing tools and techniques. Alternate action switches I got a helpline call the other day asking For a circuit to convert any old ordinary relay into an aiternate- action on-off device. Well, as the caller has found out on his C3wn, that gets a little tnckier than it sounds- Figure 1 -a shows how to convert a regular relay into a latching relay. Press normally open button A and your relay pulls in. The pull in closes a relay contact that holds the relay engaged. To reset the relay, pness normally closed button B. The relay dn^ps out, opening its latching con- tact. This IS a simple example of a latch, or a set-reset flip-flop. In Fig. 1-b we've used a pair of digital logic inverters instead. An in- verter outputs a one for any zero input and vice versa. Assume the left inverter happens to be output- ting a one. The hght inverter sees this one as an input, and outputs a zero. The zero in turn reaches areund and holds the left inverter in its present state. We are thus latched and stable. Press button A to set your latch. P^ss button B to clear your latch. It turns out that any altemate*ac- tion circuit has to consist of (wo distinct storage elements. One is for "Where am I?" and one is for "Where was I?" If you don't provide two storage devices, you will get into major reliability, oscillation, or prefenred state hassles. In most integrated circuits, the two needed storage elements are done with a pa/r of separate latches. One is called the master flip-flop. The other is the slave flip-flop. Often they are combined into a single more complex logic block, forming a type-D clocked flip-flop or some similar device. Check carefuify, and you will even find that the button on a retractable ball-point pen consists of two dis- tinct storage devices. The simplest alternate-action pushbutton I know of appears in Fig. The "Where am I?*' storage consists of that pair of back-to-back inverters. The "Where was I?" stor- age is the capacitor. Here s how it works: Some brief time after that latch changes, the capacitor will charge up to hold the The VALUE at eadi PEL or pictuia elemant det&rrntnos Ihe brightness for thai pel; the tOCATtON of that pel In the array sets til a pel position in your actuai image. 107 aOG 035Tiri93 2S4 - 091 080 12a £19(l3)l77 161 ■ £53 101 223 115 216 01S 041 - 251 OaS 205 001 240 032 089 - 093 032 093 170 079 093 106 ■ ■ 115 119 023 126 194 091 086 ■■ 004 FIG. 2— A DiarrAL IMAGE Is noth{n9 but an array of numt:t^rs. Digital image pro- (jessing takes those numbers and re* places them with other numbers, foJ lowing a ru[e or set of rules. While there ts a stunning variety of uses for digital image processing tricks and techniques, two of the most important involve gannma correction and hlsto* gram equatization. f SYNERGETICS Box e09-RE Thfitchor* AZ 65552 (602) 428*4073 (K) Typical Gamma curve of a CRT electron beam cJispiay or a 'white write* laser printer witl wash out many of the lighter whites* (B) Properly gamma correcled display or printer treats alt gray levels equally. Some available gray levels may be lost In the process. (C) Typical Gamma curve of a 'biack write" laser printer (such as a Canon SX) wilt muddy the darker grays. (white) Perceived gray levels at output (black) Intended gray levels at input RG, 3— THE GAMMA CURVE for any display or printer relates how the brightness levels are viewer perceived compared to how they are input. A non-linear gamma either '^muddies the lows" or "washes out the highs/' Gamma correction attempts to make each gray equally significant to the end viewer. ''Where was I?" one or zero. Press- ing the button forces the "Where was I?" value back onto the input of the first inverter, and the latch quick- fy flips. That happens because the charge on a capacitor cannot change immediately. Thus, at the in- stant the switch is closed, the ca- pacitor acts as a very low impedance which "force feeKis' its value to the inverter input. As soon as the inverters flip, positive feed- back reinforces and holds the new value. Releasing the button will let the "Where am I?" pair of inverters work normally A short inters^! later, the capacitor will charge up Cor down) to its new "Where was I?" value, and the cycle can repeat. The circuit can also be used as a relay driver It's the fastest and best way I know of to make a mechanical relay reliably alternate its states. While any old CMOS gates could be used, my favorite here would be a 74HC13 hex Schmidt trigger Much mom technical information on counters , latches* and state alterna- tion appears in my CMOS Cook- book, Digital image processing { never cease to be amazed at how stunningly versatile that PostScript general-purpose lan- guage is. I've recently used PostScript to create a group of rapid, easy, and fun digital image processing tools. The tools and a few test images to go with them have been posted to my GEnie PSRT RoundTable as IMAGE- KIT.PS, What I'd like to do here is give you a brief introduction to digital image processing. We'll limit ourselves to high-quality gray-scale images. We will also try to zero in on doing both a gamma correction and a histogram equalization. Those are both highly important and little un- derstood cmcial uses for serious digital image processing. Fail to un* derstand either one and your im- ages will all end up as disasters waiting to happen. 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You can borrow one of mine off of CEnie PSFET, or grab one from a scanner, off a satellite, a fax nnachine, or a video-capture board. Such a digital image is made up of picture elements, or pels. Note that a pel may or may not be the same size as the final pixel on your output device, A pel is simply the minmum resotvabte data value found in your numbers within the digital image. In a gray scale image, a pel gets defined by three parameters. The pel tuminancB value wifi tell you how bright this tiny portion of your scene will be. Its X position value will tell you how far over in the picture this pel sits, while its Y position tells you how far up and down. Fennstance. in the LENAPS file #463 on up PSRT we use 256 pos- sible grays (ranging from PostScript sO = biack smoothly up on through a 1 = white). These pels are arranged as an image 256 bytes wide by 192 bytes high. 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There are no dark blacks, no tighter whites, and the full use. A full histogram equalization Is the equivalent of a few remaining grays cluster around the two peaks. perfect photo darkroom 'dodge and burn." and extract a debluning function. Which can cancel out much (but not all) of such things as camera mo- tion. And perform such tricks as reading those license plates on speeding cars. There are now zillions of exciting techniques which use digital image pnocessing. We may look at some of these in future columns. But the first of the two techniques I feel are by far the most rmportant involves... Gamma correction The eye acts as a fog, rather than a linear device. And deep down in* side, most display schemes are also quite nonfinear As Fig. 3 shows us. ^ the Gamma curve for any imaging system nefates how the expected ^ input gray levels actually appear to g your eye at the output. The process of "fixing" a gamma J curve is called Gamma Correction, g On a video display, nonfinearities I are purpose// introduced to attempt g to cancel out such nonlineahties as iij the square law response of most electron beams to a control voltage. 84 In color work, the strengths of each individual beam are also carefully adjusted to make each color appear to be equally bright. Even if the color phosphors used have different sen- sitivities. As does your eye. If at all possible, you want to do your gamma cormction in some way that does nof cut into the number of grays you hav^ available. But if it simply can't be helped, digital image processing can be applied lo gam- ma correct your display. It can do that by redefining gray levels, trad- ing off a lot of nonlinear grays for fewer and more linear ones. All of today s laser printers have inherently nonlinear gamma curves. This happens because a n^und dot is used which has to be larger than the intended square prxel it is sup- posed to completely and flawlessly cover. Thus, in a black write system (such as the Canon SX) where the laser places down black dots, typ* ica! gray levels usually end up darker than you asked for The PhotoGfsde system used on the Apple LaserWriter G uses dig- ital image processing to trade off its gray levels for a more linear gamma. We saw some details on the PhotoGrade halftoning prcjcess last month. At 106 DPI. Apple's Pho- toGrade system has 128 gray levels available. A total of 6t of these are often used for gamma correction. The gamma correction redefines lots of realty dark grays and a few of the mtd range grays. The net result is the remaining 67 distinct and fully Gamma corrected grays. The PhotoGrade system offers you three calibration options. The options compensate for your par- ticular choice of toner, density set- tings, humidity, and so on. On a calibration^ a coarse and a finer half- tone square are put down for typical gfBy levels. This is done for three different pages. You then pick the page you like the best. The internal code does a predefined Gamma correction for you. Additional details on PhotoGrade processing appear in my GEnie PSRT#451 LASGCAL.PSandover in #388 Li^SGNOTE.TXX Also quite handy is a #R023il/A LaserWriter tfg hinters D&mioper Notes from APDA. NAMES AND NUMBERS APDA 20525 Mariam Avenue 33G Cupertino, CA 95014 (800) 282-2732 QRCLE 345 ON FBEE INFORMATION CARD Dialog InfomnaUon Service 3460 Hillview Avenue Rato Alio, CA 94304 (415) 858*2700 CmCL£ 346 ON FI^EE INFORMATION CARD DynaArt Designs 3535 Stillmeadow Lane Lancaster. CA 93536 (B05) 943*4746 CIRCLE 347 ON FREE INFORMATION CARD GEnie 401 N Washington Streel Rockvilie, MD 20850 (800) 638*9636 CIRCLE 348 ON FREE INFORMATION CARD GeO'Monitor 65 Washington Street #400 Santa Clara, CA 95050 (408) 749-6770 CIRCLE 349 ON FREE INFORMATION CARD High Energy Enterprises PO Box 5636 Security. CO 80931 (719) 475-0918 CIRCLE 350 ON FREE INFORMATION CARD Hitachi 2000 Sierra Point Pkwy Brisbane. CA 94005 (415) 589*8300 CIRCLE 351 ON FREE INFORMATION CARD KMC PO Box 348 Port Washington, Wl 53074 (414) 284-3424 CIRCLE 352 ON FREE INFORMATION CARD Histograms Those photo darkroom techni- cians and artists have lots of secret tricks they use to explore the in- credible dynamic range of photo film. By lengthening or shortening all their exposures, they can make all of their prints darker or lighter By pnnting on a "soft" paper, they can reduce therr dynamic range and contrast. Or increase it by using a **hard'' paper Or eliminate it entirely with a "litho" photo paper Even moiie sneaky is dodging and burning. With dodging, you put your moving and out-of-focus hand or a Murata 2200 Lake P^rk Drive Smyrna. GA 30080 (404) 43&-1300 CIRCLE 353 ON FREE INFORMATION CARD Outwater Plastics 4 Passaic Street Wood^Ridge, NJ 07075 (800) 526-0462 CIRCLE 354 ON FREE INFORMATION CARD Quality Technologies 610 North Mary Avenue SunnyvBle. CA 94086 (408) 720-1440 CmCLE 355 ON FREE INFORMATION CARD Signetics/Philips PO Box 3409 Sunnyvale, CA 94088 (800) 227*1817 CtRCLE 356 ON FREE INFORMATION CARD Synergetics Box 809 Thatcher. AZ 85552 (602) 428-4073 CIRCLE 357 ON FREE INFORMATION CARD Techniks, Inc 45 J Ringo Road Ringoes. NJ 08551 (908) 788-8249 CIRCLE 358 ON FREE INFORMATION CARD urn 300 North Zeeb Road Ann Artjor, MI 48106 (800) 521-3044 CIRCLE 359 ON FREE INFORMATION CARD WealherSat ink 4821 Jessie Drive Apex. NO 27502 (919) 362-5822 FAX CIRCLE 360 ON FREE INFORMATION CARD dodging paddle between the en- larger and the area bemg printed. That holds back your light in a se- lected area and nnakes that area lighter than nornnal. Which lets you pull details out of any dark or "mud- dy" areas of your negative. With burning, you hold an opaque mask having a small, ragged, out of focus, and rapidly moving hole in it between your enlarger and the print paper. Burning lets you darken your highlights and extract details from underexposed areas. By now. most of you have seen those spectacular Navajo slot can- yon photos. Most any southwest calendar should include at least one example. And Arizona Highways wHI be happy to sell you bunches of them. These mcnedible prints cany dodging and burning to an extreme, using multiple exposures and twen- ty or more very preciseiy aligned dodging masks to bring out the sub- tleties of color and texture. Digital image processing can be used to imitate these darkroom tricks. And gettmg things right on gets even more important with dig- ital images, because you will alv^s be severEly limited by both the dy- namic range and laser resolution. The fii^t step in correcting a dig- ital image is to find out what was wrong with it in the first place. To do this, you run a histogram. A histo- gram is simply a vote on how many of the grays get used how often. Figure 4 shows us the stock and welhknown Lena digital image, which should appear slightly 'weak'' or low in contrast. That histogram underneath Lena cleariy shows us why. Those light- est and darkest grays are not used at alL And most of the rest fill two cleariy defined peaks. A digital image processing meth- od known as histogram equalization will let you perform a magjc dodging and burning that can often dramat- ically improve your results. In Fig. 5 you see a much higher contrast and greatly improved Lena with lots more *'snap." To do your histogram equaliza- tion, you try to spread all of your pels around such that each gray gets used nearly as often as any other. You can then selectively re- place each pel with a lighter or a darker gray, adjusting your accumu* laled sum to spread out the total number of pets per gray. In short* you 11 do an absolutely perfect dodge and bum. § For instance, if you have 49152 S pels in your image and use 256 gray ^ levels, you redefine your grays to ^ get about 192 or so pels per gray level. A simple accumulated running ^ average does the job for you. Full a code details in my digital image g" tools on GEnie PSRT especially IM- ^ AGEKITPS. As you can see in Fig, i 5. nearly all of those available grays are Fully and uniformly used. as By doing a histogram equaliza- tion, you can pnnt "auto shopper" quality images on any unenhanced 300 DPI laser printer Figunes A and 5 are available as PSRT files #463 LENA.PS and my #468 LENAHIST.PS. Semiconductor chip houses I have been meaning to do some resource sidebars that give you most integrated circuit manufac- turers, or at least the more hacker- friendly ones. Since there's so many of them. weHI need several sidebars to do the job right. So, Acfe/ through Fujitsu will appear this month, and I'll show you the fBSt of them as we get to them Some data books are free. Others have "optional" pncing de- pending on whether the sales per- son likes you or whether any of the covered chips are currently being promoted. For others, just about ev- erybody has to pay the going rate. Your best bet is to first request a short fomi catalog, a price list, and their technical literature and applica- tion note rndex. These are all usually both Free and Immedrately available. Be sure to use your laser-pnnted letterhead or a professional sound- ing telephone request. New tech lit Data books include the Optoelectfomc Products Catalog from Quality Technologies. This used to be the old GE/Harris opto line. Advanced Lmear Devices has a f^duct Databook on linear timers, op amps, and comparators. From Signettcs/PhiUps. there's a new data book on CMOS Se- quencer Solutions. And from Hitachi, there's a Semiconductor Devices for Communicattons data book. Included are lots of telco and cellular radio devices. Our two brand new labor-of love newsletters include WeatherSat Ink and the Geo-Monitor The first is on weather satellite image reception; the second on earthquake monitor- ing and prediction. Over tn our neat mechanical Stuff department, a fiee sample of a laser machined plastic ts available from KMC And an rncredible catalog fnDm Outvoter Plastics. These folks are labonng under the delusion that they are now in the store display fixtures business. In reality, they of- fer lots of useful new electronic and prototyping hardv^re at unbeatable prices. Not to mention off-the-wall ideas. They even stock Grecian urns for writing odes on. For the two key books on all of the fundamentals of digital inte- grated circuits, try my CMOS Cookbook and JTL Cookbook, ei- ther by themselves or as part of my Lancaster Classics Library. As usual, we've gathered many of the resources mentioned together into either the Names & Numbers or the Integrated Circuit Manufac- turers sidebars. Check these out before you use our no-charge tech- nical helpline or call for your free hacker secrets brochure. I e I 06 AN ECONOMICAL KEYBOARD-CONTROLLED KEPCO BENCH POWER SUPPLY 75 WATTS Choose from four Digital Power Supplies: 0-12.5V r« 6A* 0-24V ia 3A. 0-40V (a 2fK or 0't25V (u 0.5A. Each on© offers precise, repealabfe voilage control with two current ranges. Fully proiecled for overvollage or overcurrent. Bonus: You can program the output from your PC's serial port (RS232 sohware included) and read back too! The DPS is an affofdable prolessronal inslrumenl and belongs of> your bertch. 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Southern Ave., Suite 111, Tempe, AZ 85282, 1-800-335-7389. CIRCLE 195 OH FREE INFORMATION CARD DRAWING BOARD Let's see what's involved in desc rambling a SSAVI signal. ROBERT GROSSBLATT Fooling around with the simple video stuff we*ve been build- ing is a nice afternative to hanging around on street comers, but it s not really all that terrific if your ultimate goal is to figure out what to do with the junk that shows up on certain channels on your TV. Suppressed sync is the Modei-T version of video scrambling, and you can bet your bottom dollar that things have gotten a tot more com- plicated. Enter the digital age. Since the suppressed-sync scrambling system was so simple, it wasn't long before people with only moderate electronic skills figured out what was being done and how to beat it. Even the simple stuff we put together over the last couple of months could—with some minor additions — do the job. As the cable business grew, so did the complex- ity of their scrambling methods. As I told you when we first started out on this trip Into cable video land, ripping the video signal apart is easy — putting it back together suc- cessfully is something else entirely The amount of messing up that's done to the standard video signal is directly proportional to the cost. More intense scrambling is more expensive. Cable operators have to balance their degree of security against the cost of the equipment. Also, the larger the customer base, the less expensive the scrambling ^ system has to be. In New York City (and other large areas), the cabfe -| companies have a lot of subscrib- g ers. each of whom needs a cable - box. The more boxes the cable J company has to buy (they don*t ^ make them themselves), the more g money it has to keep tied up in its g inventory. UJ The old suppressed-sync system was a one-way deal. If you got a box that could descramble one channel. it could descramble any channel Which channels would be un- scrambled was determined by one of the wafers on the channel selec- tor dial A position would be either jumped or open, which was a major caWe company headache for two reasons. The first was that they had to open the boxes and solder or cut traces to configure the box for a given customer. The second was that some enterprising people real ized what was going on. opened up their cable boxes, and reconfigured it themselves. The only way the cable compa- nies could guard against that was to use screws with oddball shaped heads to hold the box together. When that didn't work, they started using screws that had a left-hand thread. But enough history. What the cable companies needed was a way to talk to each of the boxes individually, while they were in customer s homes. Making such addressable boxes also meant that several scrambling methods could be used; the boxes could be told which method v^^s in use at any one time. Since that information couid be sent to the box during the vertical blanking interval (while the beam was off the screen), the cable operator could change the scram- bfing method from field to field^ — up to sixty times a second. The boxes could also keep a serial number in an EPROM or some other storage device, which meant that boxes could be addressed individually and the descrambling circuitry could be turned on and off for separate chan- nels from the main cable company office. The cable companies loved it. Understanding that kind of stuff is a bit more difficult than the old sup- pressed-sync system, but if you take the pieces one at a time, it all gets cut down to manageable, bite* sized chunks. Although the cable company's scrambling delivery sys* tem became much more sophisti- cated, it was still faced with the same cost restrictions when it had to decide which of the available scrambling techniques to use. One of the most popular choices was the so called SSAVI system. That s an acronym for Sync Sup- pression Active Video Inversion. It allows the video to be delivered to your doorstep in one of four flavors: • Suppressed horizontal sync and normal video (Fig. 1). • Suppressed horizontal sync and inverted video CFig. 2). • Norma! sync and suppressed vid- eo (Fig. 3X • Normal sync and normal video (we can forget this one). Before we get into the nitty gritty of the SSAVI system, there are a RG< 1— THE SSAVI SYSTEM can deliver video with suppressed horizontal sync and nomiet video. \^ — coNmot: FIG. 2— SUPPRESSED HORIZONTAL SYr^C and inverted video is also possible with the SSAVI system. This isn't as strange as it might seem. In a normal video signal the reference for color is the burst sig- nal that follows horizontal sync- The colorburst signal lasts only a bit lon- ger than 2 microseconds, but it s used as a reference for the whole video line, which is about 63 micro- seconds long. As far as color cor* rection is concerned, that means there's no real reference signal avail- able for more than 95% of the line! The cobr phase for the rest of the few basic things you shoufd know, because they tell you some interest* ing things about how the system works. The first is that horizontal sync is never inverted — even rf the picture is rnverted. This means that any cir- cuit designed to descramble it has to separate the two basic parts of the video line (control and picture firsti We have to be able to turn the picture right side up Cif needed) without inverting the control section as welL The SSAVI system seems even more complex when you realize that the job of separating control and picture has to be done on lines that might very well have no horizontal sync pulse that can be used as a reference mark. In the older sup* pressed-sync system, the sync could be recovered from the gating signal that was buried in the audio: with the SSAVI system, there s nothing like that available. The key to regenerating the video signal is based on the fact that all aspects of tt are tied together in a strict mathematical relationship. If you can locate one part of the sig- nal, you can determine where every- thing else has to be. The broad picture for a de- scrambler, therefore, is to design a circuit that can identify one part of the signal, and then use the repeti- tion of that signal as a reference for restoring the rest of the video. You should realize by now that weVe talking about a phase-locked loop, or PLL. Even if the identifiable com- ponent of the video occurs only once a field Cor even once a frameX that's still often enough to control the frequency of a voltage*con- trolled oscillator, or VCO, and lock the PLL to the received video. 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CALL TOLL-FREE 1-800-284-8432 • JERROLD • TOCOM • ZENITH • • OAK • PIONEER • IIAMUN • * SCIENTIFIC ATLANTA • 24 HOUR SHIPMENTSl aUANimf OJSCOUHTS! MOHEY BACK COARANTEEl FREE CATALOG & [NFORMATIOM Masirrrani * Aimrksm Ej^niMs * i'jtsa * CO.D. mVE Uy(£ IIODa MIUSBI Cr fOUF^ USB} » ^ For techniciit ay connect to a TV set for home use* or it may be portable. It should hit the shelves in summer of 1993. and should be priced under Si 000. The software technologies be- hind Sweet Pea are mighty interest- ing. Kaleida. the jOint venture in multimedia between IBM and Ap- ple, will supply these technologies. One is called Script X: it is an author- ing language that developers can use to create multimedia titles that will run on multiple platforms, includ- ing Intel and Motorola CPU s. and RISC devices. It will also run on spe- cial operating systems used by MMM's, In fact. Kaleida is develop- ing one such operating system, the Consumer Operating System (COS) that will, of course, support Script X. Script X is also slated to support Apple s multimedia stan- dard, QuickTime. Apple has signed deals with Warner New Media and Paramount Communications to supply titles; Claris. Apple's software subsidiary, will also develop new titles. Kaleida got off to a slow start, and has been partially eclipsed by other more immediately apparent benefits of the historic 1991 accords be* tween IBM and Apple. However, the fBCenl appointment of a board of directors, along with Nat Goldhaber as head of Kaleida. not to mention the Sweet Pea technology an- nouncements. all indicate that Ka- leida is likely to be the vortex of some fascinating and industry-shab irvg new developments. Less technologically advanced, but likely to have some market im- pact, are new pen-based pocket or- ganizers that will be introduced by Sharp and a joint effort between Tandy and Casio. At an estimated $300. the Tandy/Casio unit aims to undercut initial pricing on Newton and Sweet Pea devices. The Tandy/ Casio will use the GeoWorks graph- ical environment, will have built-in handwriting recognition, and will have a PCMCIA slot for memory and telecommunications. Look for it sometime in 1993. The Sharp unit adds pen input to the Wizard line, and includes an extensive pushbut- ton/menu-based interface. Pricing was unclear as of press time; the device is scheduled for release this year Also scheduled from Sharp is an 8088-based palmtop that should sell for about $1000. Microsoft is hankering after this market as well. Lately there has been discussion about a CD-ROM based machine that would run a ROM-based subset of Windows, connect to a TV set. and provide infotainment. Apparentty designed to compete in the video- game mar- ket, the device is currently going by the name Wintendo. Upheaval in the PC business In the beginning was the PC. which meant an 8088 and one or two 360K floppies. Then came the XT, which added a hard disk and bumped memory up to 640K Next came the AT which added a full 16- bit pnocessor and peripheral inter- face. Then came the 386. which brought 32-bit processing and un- heard-of performance. For a good four or frve years, the boundanes between those four divisions were clear However, in the past two years, the introduction of new CPU's by both Intel and its rivals has almost completely obliterated those bounds. Now there is a smooth spectrum of often overlap- ping price/performance choices ranging from lowly 386SX's to 50- MHz 80486DX"s. It's nearly impos- sible to keep in mind all the varia- tions among CPUs, including speed, bus width, power manage- ment. cache size, math coprocessor, and system support components. Choosing a complete system is no longer a choice among four well-defined categories. § Against that backdrop, manufec- % tuners find it difficult to make their offerings stand out. In the past year g intense price wars have forced sys- ^ tem costs to absurdly low levels. At ^ first, the price wars were conducted g almost exclusively among clone | manufacturers, but Compaq re- ^ cently joined the fray. IBM has | promised to do so by this fall, and second-tier suppliers like Dell have gi already retaliated. One industry analyst has stated that there are some 500 PC suppliers, of which 450 shouldn't exist. Another ana- lyst suggests that within a few years, the vendor base will be re- duced to a dozen multinational cor- porations that supply 95% of industry needs. Another trend is that toward in- creasingly dense integration, both at the chip and the system level. For examplen the original PC used 16K DRAM s. Todays standard is 4 megabits, an increase of 256 times. Back then, system logic was built from hundreds of discrete TTL com- ponents. Today, three or four VLSI IC s do the same job. At the system level many motherboards today contain built-in serial and parallel ports, hard- and floppy-disk contnol- lers, and expansive memory — 16 megabytes or more. By contrast, original IBM motherboards seldom held more than 51 2K of memory, and contained nothing but the re- quired system logic. Together, price wars and the larger trend of increasing integration lead to the necessity of product dif- ferentiation, or some means of mak- ing your product stand out in the customers mind from that of your competitor. Price cutting is one wgy, but It can only go so far. The other way is to add features, and that s what well start seeing this fall. Look for systems with built-in net- working and sound capabilities. Look for systems from IBM and others with preinstalled operating system software COS/2. DOS/Win dowsX Look for systems with tons of bundled applications. Look for creative marketing schemes, (For example. DAK. a mail-order house, now gjves away a 386DX/33 with purchase of $1500 worth of soft- ware — and quality stuff at that, in- cluding current versions of Win- dows, Word for Windows. Norton Desktop. Adobe Type Manager. Par- adox, and more). Look for pre- assembled networks supporting anywhere from 2 to 250 users. Look for hard-drive upgrades from Sea- gale and others with preinstalled software (Windows). Look for laser- printer upgrades that incfude RAM with font and emulation cartridges. Look for operating systems (Win- dows and 0S/2> to include more and more features traditionally as- sumed to be part of the applications realm, e.g.. networking and E-mail The following are several trends to watch: CPU Wars Intel continues to try to fend off attacks on its 386 business— AMD expects to take 50% of the market by the end of this year — but both AMD and Cyrix are mounting new offensives on the 486, Cyrix will in- troduce 25-, 33', and 40-MH2 ver- sions of its 486 clone at about half the price Intel charges. Meanwhile. AMD plans similar introductions^ but a recent legal setback could stall its efforts. IIT is also entering the race: the company stated re- cently that it is developing a 486 clone with integrated video display and image compression hardware, paralleling Intel's efforts to combine an X86 CPU with IBM s XGA graph- ics and Intel's own Digital Video In- teractive (DVD, a digital system for compressing and playing back vid- eo on standard PC's. Timely intro- duction of the latter could be the breakthrough PC-based multimedia has been wailmg for Intels P5 (sometimes known as the 586. although reports indicate that Intel is searching for a new name) contains two CPU s. a 486- compatible unit, and a Reduced In- struction Set Computing (RISC) unit. V#iat's the value of sticking a RISC chip in a PC? On the other hand, what would be the value of sticking a 486 in a workstation (nor- mally powered by a RISC chip)? In a PC. let the 486 do PC things (DOS. Windows. OS/2), and let the RISC unit run the \ndeo system or a dedi- cated compressron/decompres' sion unit. In a v/orkstation. let the RISC unit do Unix things, and let the 486 provide PC compatibility. Power Play Power consumption is becoming a hot topic not only among note* book PC vendors, but among desk- top system vendors as welL Consumers demand longer battery life fnom their notebooks — a mini- mum of eight or ten hours. Desktop vendors need to cut power con- sumption for reasons of energy con- servation. Significantly reducing energy consumption by computers would save $1 billion per year plus reduce CO^ emissions by the equiv- alent of 5 million automobiles during the same period. Achieving these reductions is not wishful thinking; a recently formed industry/govern- ment coalition that mcludes the EPA. Apple. Compaq, DEC. HR CPU VESA OR MTEL imiHmcE GRAF HICS f FflAMI 1 BUFFER 1 SCSI VQ COMPONEtnS EXPANSION BUS CHIP SET STAWOARD EXPAHSIOH BUS (EISA.ISA.MCA) \ n LD BOARDS FIG. 1— LOCAL BUS ARCHITECTURES supplied by Intel and the Video Electronics Standards Association {VESA) promise to pmvfde a hrgh-bandwidth channel between the CPU and fast peripherals including video and network adapters, and mass- storage Interfaces. E-N Computer Admart HOW TO EXPAND, MODERNIZE AND REPAIR PCs AND COMPATIBLES BP271— lecludes PC overview, memory upgrades, adding a hard disc, adding floppy drives, display adapters and monitors, installing a co- processor, preventive maintenance, repairs, do il yourself PCs and more. To order your copy senti S7.75 plus $2.00 for shipping in the U.S. to Eleclronic Technology Today Inc.. P.O. Boi 240, Massapequa Park, NY 11762*0240. Rales: Ads 3fe lYi^'xlW, One insertion S99S each. SiJt insertions $950 each. Twelve insertmns S92S each. Closing date same as regular rate card Send order with remittance to Compuler Admart, Efectronics Hm f^agazine, 5D0-B Bi-County Blvd . FarminQdale. NV 11735. Direct telephone inquiries to Arline Fishman. area code-1-516-293-a000, FAX 1-511-293*311$. Qatf W% Computer ads are accepted for this Admart. PRACTICAL ELECTRONIC DESIGN DATA Pracllc«1 Elsctronic BP31&— A comprehensive ready- reference manual for electronics enthusiasts, be they hobbyists, students or professionals. To order your copy send $8 J5 plus $2.50 for shipping in the O.S, to Electronic Technology Today Inc., P.O. Box 240, Massapequa Park, NY 11762-0240. PCB / Schoifiatlc CAO * SI 95 mijflib)«f bovoi to 1 r« I r up 1 too PhwwTwiHy IHI Kfut lo tifm 2ftB/»& tcnC' ia*i vtK OmM lo (/ifimi. ffnm fiatmt tJC Dell, Jib<*ri*i «vkil«tJ« Not CflfT fm*ct*d Logic Simulation - S37S ***«MrmS Bid CHOI Analoguo SlmulaUon - $375 For Into", mtt*. lix. ull Of Ln« Inqulfy # ^ -urtaa Number One Syvtcmi LtiL i REf: REUS, HARDIMQ WAY. fiT.IVES. A,MEXhV1£A ind MASTERCARD iftlcomp. QtRO^ tB6 ON Fn££ INFOntUTlON CARD IBM, NCR. Zenith, and otfier man* ufacturers announced a set of de- sign parameters centered around several types of "sleep" modes and 3.3-vDlt system components. The goal Is to reduce power consump- tion of the average PC to 30 watts. AMD is pnomoting 3-volt system design guidelines, and it says that a complete PC chip set will be avail- able this summer with product in- troductions (probably centered around notebooks) scheduled for fall COMDEX. To support this bur- geoning nnarket. Intel has an* nounced a 3. 3-volt version of the 386SL that includes a fully static CPU, cache controller, bus and memory controllers, that can inter- face with both 3.3- and 5-voit pe- npherals. Cirrus Logic has intro- duced 3 dual-voltage video control- ler. Just Add Water Networking is not yet hilly per- vasive. However, new chip designs promise low-cost system additions that will further spread the ability to link up. One study shows steady growth in units shipped per year dur- ing the period 1989 (2.2 million) through 1995 C6.7 million). AMD has introduced a single-IC Ethernet adapter that (along with simitar de- vices from National, SMC, and others) is going to further increase the availability and use of networks. The chip will be a built-in component on many new motherboards: sev- eral influential PC systems houses (Apple, Compaq. Delt HR North- gate) have already introduced (or will shortly) systems with built-in network adapters. Couple that with increasingly aggresstve marketing by Novell plus built-in network c:a* pabilities of the next version of Wrn- dows — and you've got instant networking. The Magic Bus Windows and OS/2 demand fast, high-performance computers. As clock speed increases, getting data in and out of the CPU becomes more critical to maximizing system performance. Our trusty old system buses (ISA, EISA. MCA) simply amn't up to the task. In recent months, computer manufacturers have added a local bus that provides a direct path between the CPU and some other component, usually a special video adapter. So fan how- ever, these efforts have been ham- pered by a lack of standards. In response. Intel and an industry consortium called the Video Elec- tronics Standards Association (VESA) have each devised its own local bus standard (see Fig. 1). Some published reports have claimed that the two standards will compete with each other; however, Intel officials have stated publicly that the two efforts are complemen- tary. Both share throughputs in the 120-130 megabyteS'per-second range. The VESA spec includes a connector design (based on a Micro Channel bus connector) that the In- tel spec currently lacks. On the other hand, the Intel spec includes a special interface IC that helps iso- late the CPU from I/O sub- systems — and that presumably allows for transparent CPU up- grades via the company's Over- Drive technology Due to bus-timing and signal-reflection issues, local bus slots v^ll most likely be limited to thiBe, e.g., one each for video, network, and hard-disk control; the latter could be a SCSI host adapter for connecting multiple devices. The regular expansion bus would then § be limited to slow-speed devices. In short, the next few years v^ll see many PC vendors dropping out: S the ones that remain will be fighting tooth and nail to establish their ^ products with increasingly dense in- s legration of hardwans and software components. Price wars are already _ raging: feature wars are just about i to break out. This is going to be one heck of an interesting battle. R-E 93 HAND! TALKIE continued jrom page 60 ed, variable Polyswitch resistor R30 could Irip and/or the out- put power MOSFET's could overheat. When using the flexible "rub- ber ducky'Vantenna* it might be necessary to fine tune capacitor C30. taking care to keep the an* tenna away from people or large metal objects. After tuning the transmitter set up the receiver. TUrn the power ON and set the squelch control fully counterclockwise (off). With the 32-ohm speaker connected, increase the volume until the background noise is audible. Using the oscillocope. look at the output from REcowRKD AUDIO piu 16 of the FM receiver chip IC3, and adjust inductor LIO so that the signal reaches a maximum level. If an FM-modulated RF source is avaliable. connect it to the an- tenna jack and set it to a 1 mi- crovolt output level. Set the audio signal to 1 kHz and the deviation to 4 kHz. Adjust LIO for a symetric waveform on pin 16 of iC3. The tone should be audible in the speaker. Set the input level toO.3 microvolts and adjust L3 for minimum noise level. (This adjustment is op- tionaJJ The range of the transceiver with the specified antenna is one to three miles» depending on background noise and the proximity of buildings or geo- graphical obstructions. The range can be increased with a citizen band (CB) base station antenna, or if its transmission frequency is set for the 10-meter amateur radio band and a suit- able antenna for that frequency range is connected. To change the transceivers frequency from 25 MHz to 31 MHz* change crystals 1 and 3 (XTALl and XTAL3) and tune the transceiver according to the instructions given earlier {See the Parts List for the crystal specs,) To operate the trans- ceiver outside of the 25-MHz to 31*MH2 bands, the transmit fil- ter as well as the multiplier com- ponents must be changed. R-E VERSAiriE OSCILLATOR continued from pugc 74 That resistance value will keep the peak speaker currents with- in the 200-milliampere output limit of the 555, The output power of this alarm circuit de- pends on speaker impedance and supply voltage, but it can be as high as 750 milliwatts with a 75-ohm speaker and a l5-voIt supply. Notice that C3 ia an elec- trolytic capacitor Figure 19 shows how the out- put power of the circuit In Fig, 18 can be boosted to several watts with buffer transistor Ql, The resulting high speaker out- put current can introduce a sig- nificant ripple voltage to the power source. Diode 131 and electrolytic capacitor C3 protect the 555 from the effects of that ripple. Diodes D2 and D3 clamp the inductive switching spikes from the speaker and protect Ql against damage. The circuits in Figs. 20 to 23 have a similar output stages, Figure 20 shows how a pair of 555 s organized as as I able mul- tivibralors lorm an 800-Hz pulsed-tone alarm generator In this circuit ICl is wired as a 500*H2 alarm generator, and IC2 is wired as a 1-Hz oscillator that triggers ICl on and off through diode Dl once per sec* ond, thus generating the pulse- tone alarm. The circuit In Fig. 21 gener- ates the penetrating two-tone **he-haw*' sound of Ein^opean emergency vehicles. Here, ICl is also wired as an alarm gener- ator and IC2 is wired as a I -Hz oscillator. But In this ease the output of IC2 frequency modu- lates ICl through resistor R5, The output frequency of ICl al- ternates symmetrically between 500 Hz and 440 Hz in one-sec- ond alternating cycles. Figure 22 shows a circuit that generates the wailing noise of a police siren. Here IC2 is wired as a low- frequency oscillator with a cycle period of about 6 seconds. The slowly varying rnmp wave- form of IC2, buffered by emitter follower transistor QL frequen- cy modulates alarm generator 101 through resistor R6, In this circuit ICl has a natural center frequency of about 500 Hz. The alarm output signal starts at a low^ f requeue); rises for three seconds to a high frequency, then decays over a period of three seconds to a low-frequen- cy before repeating itself as long as power is applied. Finally the circuit in Fig. 23 generates an alarm that simu- lates the "Red Alert" that is often heard in the Star Trek TV series. The sound starts at a low fre- quency and rises to a high fre- quency in about 1.15 seconds, ceases for about 0.35 seconds, and then starts rising again from a low frequency. Here again, the sound pattern re- peats as long as power is applied to the circuit. The 555 labeled 1C2 is wired as a non-symmetrical oscillator. Capacitor CI alternately charges through Rl and diode 01, and discharges through R2. The result is a rapidly rising and slowly falling "sawtooth" wave- form across CI. After buffering by Ql. this waveform frequency modulates pin 5 of ICl through R7. causing the output frequen- cy of ICl to rise slowly during the decay part of the sawtooth waveform and to collapse rapidly during the rising part of the sawtooth waveform. The rectangular waveform at pin 3 of 1C2 turns ICl off through common-emitter am- plifier Q2 during the decay phase of the alarm. Therefore, only the rising parts of the sound pattern are heard which sound very much like the Star Ti-ek Red Alert, The ou tpu ts of most of t he cir- cuits in this article have been taken from output pin 3, but many of the figures haven shown triangular waveforms developed across the timing ca- pacitor (e.g. Figs, 3b, lib, 13b and 15b)* There might be occa- sions when you will find those sawtooth (or ramp) waves useful. You can obtain a saw- tooth by tapping the charge voltage across the timing capac- itor. By charging the capacitor with a constant-current source instead of a simple resistance, the ramp can be made quite lin- ear. R-E Countersurveillance Never before has so much professionaf information on the art of detecting and eliminating electronic snooping devices — and how to defend against experienced information thieves— been placed in one VHS video. If you are a Fortune 500 CEO, an executive in any hi-tech industry or a novice seefiing entry into an honorable, rewarding field of work in countersurveiilance, you must view this video presentation again and again. Wake You may be che vicrim of stokn words — jsrtctous ideas that ^^wld have made you vtr>' wtrakhy! Ycs» profcs- sionaJs, tntn rank amateurs, may be lis- tening to your most private con- versations. Waktt iipf If you att.- not the victim, then you ate surroundt'cl by cuurttless vic- tims who need your help if you know how to discover telcpho tiu caps, locate bugs* or "sweep** a foom clean- There is a thriving professional service steeped in hi^h-tech techniques that you can become a part oil But hrst, you must know anil understand Countfrsurveihince Technology. Your very first insight into this highly rewrdin^; field is made possi* ble by a video VHS prcsentarion that you cannot view on broadcast television, sat- ellite, or cable. It presents an informative pmgram prepared by pnjtessionals in the field who know their industry, its tech- niques, ktnks and loopholes. Men who can tell you more in 4") minutes in a straightfor\^'ard, exclusive talk than was ever attempted befoR\ Foiling Information Thieves Discover the targets professional snoopers seek out! llic prey irc stock brokers, arbirrti^e hrms, mnnufacturt.TS, high-tech companies, any competiiive industry, or even smalt businnesscs in the same community. Tlie valuable informa^ rion they filch may be marketing strat- egies, customer lists, protluct formulas, manufacturing techniques, even adver* rising plans^ Informarion thieves eaves- drop on court decisions, bidding informarion, financial data. Tiie list is unlimited in the mind of man— <*s- pecially if he is a thieH You know that the Russiatis secretly installed countless micmphones in the concrete work of the American Embassy building in Moscow. TTicy converted CALL NOW! 1-516-293-3751 HAVE YOUR VISA or MC CARD AVAILABLE w^hat Wp-as to be an embassy and pri^-atc residence into the most sophtsticated tv* cording studio the world had ever known* Tlie building had to be torn down in order to a- move all the bugs. Stolen Information Tlie opt^n taps fmm where the informa- tion |H»urs out may be fn>m FAXs, com* puter communications, telephone calls, and everyday business meetings and lunchti me encounters. Businessmen need counselling on how to eliminate this in- formation drain. Basic tclephtjoe use cou- pled with the users understiuuiing thiU someouir may he listening ut recording vital data and information greatly reduces the op|Mirt unity for others to purloin meaningful information. RO, \Uy\ d099 • I'armingdalc, NY 11755 PItiH' ni>h m\ oipy itl iht' C iniiiHT^nri fill j rut' Tc-vliii^Ujm'!^ Vidf^i VH> iJi**t'|ic fun liiiJil tityi *it sriUli t>likl) Ktt1tHhrt»4.1XI|hnUtr ami hinii&ii|tl S^i tit « nhknTll , _ ^>*iim III punimrit it^ Ufii Nil, AH fu^ mKm\ mVS \ f^lluK c^it^tSun^ jckJ » 4 Ul) per Vlts The professional discussions seen on the TV screen in your home reveals how to detect and disable wiretaps^ midget radio* frequency transmitters, and other bugs, plus when to use disinformation to confuse the un^K'anted listener, and the technique of voice scrambling reiephone communications. In fact, do you know how to kmk for a bug, w-here to look for a bug, and what to do w^hen you find it? Bugs of a vvry small size are easj' to build and they can be placed quickly in a matter of seconds* in any objecr or room. Today you may have used a telephone handset rhar was bugged. It probably con tat fled three bugs. One was a phony bug to fool you into believing you found a bug and secured the telephone, Tlie sec- ond bug placates the investigator when he finds the real thing! And the third bug is found only by the professtonaL who continued to st*arch just in case there were more bugs. The professional is not without his tools. Special equipment has been de- signed so that the professional can sweep a room so that he can detect \T3ice*acti- %'ated (VOX) and remote-activated bugs. Some of this equipment can be operated by novices, others require a trained coun- ters u rvei I bnce p rofcssi t> na 1 . The pmfessiormls viewed on your tele- vision scteen reveal information on the latest technological ad^^ances like laser- beam snoopers that are installed hun- dreds of feet away from rhe room they snoop on* The professionals disclose that computers yield information too easily. This advertisement was not written by a countersurveillance professional, but by a beginner whose only experience came from viewing the vide** tape in the pri- vacy of his home. After you review the videt) carefully and understand its con- tents » you have taken the first important step in either acquiring [>rofcsstonal liclp with ytmr surveillance problems, or you may very well consider a career as a coun- ters ur\'c ilia nee pmfcss i t>na 1 . The Dollars You Save To obtain the information contained in the video VHS cassette » you would attend a professional seminar costing $330-750 and possibly pay hundreds of dollars more if ycm had to travel to a distanr city to attend. Now, for only $49^95 (plus S4hIMJ F&H) you can view Counteruir- it xl la u€€ Techniques at home and take refresher views often. To obtain your copy* complete the coupon or call . 1 O 95 E-N Engineering Admart DR. "CHIP" MUNK SAYS OCVHLOPMENT tSolJ ^UAUTV ^^^^^^ AfFORDABiLrrv "Chip" experts agree with Dr. Munk. TECFs P€ bii5«J ftiicroconlrollrr devel* opment took arc the mmt cost elTective Tor veterans or beginners, ft» FSIRWX Hm WlpT^lWv , . S19S^ aDt5^«iurcts^ficiL CROSS assemblers. .... swjdo •»f.lf*IKT»5 STATU AIIW / niinL Hammond, IN 46324 TUBES, new. up lo 90^4. ot^. SASE. KIRBY, 293 West Camel Onve, Carmel, IM 46032. TV. nolch fillers, phone recording ^uipmertt, bro^ Chure SI. 00 MlCflO THinc. Box 63 6025. Mar- gate, FL 33063. (305) 752-9202 SPEAKER mpau: AJt makes — modds. StefBo & c'^al. IQs awalable. Rafoajning 51 8. 00 ATLANTA AUDIO LABS, 1 (dOO) 56d-6971 . CLASSIFIED AD ORDER FORM 1q run ywff omr cftntifM ad, put am word OAMCh th« in«s bvtow and Hnd thit lorm atarig ntlh your cttack I?: Electronics Now Classifi^ Ads, 5£X^B Bi-Coiinty 8out@vard. Farmingdale, NY 11735 PLEASE INDICATE m which category of classrtied advertisfng you wish your ad to appear. For special headirtgs, there is a surctiarge of S25.Q0. ( ) Plans. 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(( e^ Aug. issue copy musl be recen«d by Bt^l When ngmtal dbsmg date faHs on Satunlay, Sviday or Homy, issue dkHes on p(«owing wodttrig day Send Iex 49 on me Free lintormaton Card RESTRICTED t&cfinical information: Electronic surveillance, schematics. locksmtthir>g. cover! sciences. Nacking, eic Kiige setectJon. FrM brochwros. MENTOR'Z» Drawer 1549, Asbury Park, m Q77\2. ENGINEERING software and hardware. PC/ MSDOS. Circuit design and drawing, PC6 layout, FFT analysis. mathematicSp circuit analysts, etc. Data acqyisition, generation, I/O PCB's, etc. Call or write for free catalog. (614) 491-0832. BSOFT SOFTWARE, INCm 444 Colton Rd ^ Columbus. OH 43207. CABLE TV EqufpmtnL Most type avaitabto. Speoal Oak M35B S39.95. Nq catalog, COD of' ders only 1 (300) 822*9955. Quality f^iCfQwave TV Antennas i wmuZS UeiE - efts MMDS - Anmruf TV PfflLLIPS TECH ELECTRONICS Di*h Sfitcm P.O. Bpi a533 - Scotlidnlo, AZ 65252 [SGZ^ 947T7DO il2 00 Cieifit iCL phont prdlflj umi» 80C52-BasiC microcotttroiter board, Basic inter- pralef, 32K RAM. 16K Eprcfn, Eprom programmer, BS232, oicpansion connector. Bare board with manijaJ. schematics S22.95. 80052- Base mjcm* processor chip S25.9B. Assembled and tested SI 24 95 PFIOLOOIC DESIGNS, TO Box 19026, BaEtimcra. MD 21204 JERROLD. Tocom and Zenith "test" chip*. Fully Qctlvatei unit. $50.00. Cabl@ de- scrambicrs from S40,00. Orders 1 (BOO^ 452*7090. Information (310) 387-0081. TOCOII-Jerrold Impulse-Scientlftc Atlanta Combers, two yeaf wairanties. aJso test mod- ules for your coTLverters Cof^iaci NATIONAL CA- BLE, (219} 93&4128 full details. FREE CATALOG FAMOUS "FIRESTIK" BRAND CB ANTENNAS AND ACCESSORIES. QDAUTY PBODUCTS FOR THE SERIOUS OB er SINCE 1982 FIRESTIK ANTENNA COMPANY 2614 EAST ADAMS PHOENIX. ARIZONA 05034 OSCILLOSCOPE 50 MHz. Hewlett-Packard, sol- id state calitirated» manual $290.00^ 1 (800) 835-8335 X459. SECIIET cable descramblets! Build your own descrambler tor less than S12 DO in seven easy steps, Cort^piete msuuctiofvs $10.00, Radio St^ack pans i^si and froe descramtifiiH mettvxis that cost nothifkg to try induded. HAWHYWHrTE, PO Box 1790, Baytown. TX 77520, DESCRAMBUERS, converters, all i^ame brands in slock, lowest price examples DPV-5 5189,00. VIP S250.00, Oak $99,00. add on descramblers TVT or SA3-B 5 $49,00 ea. Guaranteed. COD orders OK. free catalog KABL£ KONNECTION (702) 433-69S9. CABLE TV equipment, wholesale lo all, Oak. Jer- rold. Zentth. Tocom. S.A., eKam^>le Star com -6 with ^ume 5189,00. Quantity poces aivasiable CO O. ofders OfC Fr»e c^aJog. ULTIMATE CA* BLE PRODUCTS, (702) 646-6952. l\3 3 97 MARK V CUanONICS, INC. TA^tSOO TA 3fiOO lilt M ^CMn 1 K im Jut AAA n l« •«f7C'i«il D. |> V 4 A il V> *»«tMvh( iCQ t1 P ifl "^nl (m'vT'I'ii AA MOD 4100 tarn «» METAL CASrNETB WTTti AlLmtHUM FAHEL 1 ir j^! WiU'ci- ;ja 2tU 1»« WW i ir tl'i TAUT Ti i r4r.YiWiMAIQ0Ui? U tCQaili Jv^ 1 r* i"i -J, ,■ -J-, ri 1 *Xt *3a 'cra .m HOB fDOl foa i«tt MARK V KLHCI kONIOi. INC ORDER IN CAUFORNIA 1'B0D-52l^MARK ORDER OUTSIDE CA l'eOO'4Z3*FIVE CATALOG & IMFORMATIOH U13} 8a8'fl988 OHDER BY FAX (213) 6aa*68&e O ClflCLE 93 OH FUEE INFOnUATKW CARD CB RADIO OWNERS! We specialise rn a wide variely of technical ^nfomiation, parts and services for CB radios. 10- Meter and FM conversion kits, repair books, plans, fiigh-peiformance accessories Thotisands of satisfied cusiomefS since 1976 f Catalog $2. CSC INTERNATIONAL P,0, BOX 3I500RE. PHOENIX. AZ 85046 PflOi tui yourseW and aquipfneni from electncal shocks. Compfeie unir 398.95. SAFETY-UN- LIMITED, 1743 Baldwin Road, Yofklown. MY 10598. S-HS5 00. CABLE equipment at wtiotesate pnoas. Tocom. Oak, Zenitti, Jerrotd. SA. Hamlm. ad1 ^hflcKVJm (5f wc ^^H^VO Add % 3 s^ilpplng 5 @>S19<95,10@$14,95: Box 141 56, Fremont, C*. 94539 Fax {510) 651-8454 SURVEILLANCE Iransmitter kits tune from 65 lo 305 MHz. Mains powered dupfex, telephone, room, combination teiophone'nxjm. Catalog with Popular Communications, Popular Elec- tronics and Radio-Electronics book fevio i1 youfsell — major brands discounted, we' It beat everyone's price. DIS- COUNT LARRY {BOB] 596-0656 V10E0C1PHER \l descfambiin^ manual Sche* mat>cs. video, and audio. Estplains DES. Eprom, CloneM aster. 3 Musketeer, Pay-per-view |HBO. Dnemax, Shov^time. Adult, etc ) Si 6. 95. S2,00 postage- Scfiernaiics for Vtdeocypher Plus« $20.00. SchemMk:s for VideocypFier 032, $15.00. Collection of software to copy and alter Eptom codes. S25-00. CABLETRONICS, Box 30502R. Belhesda. UD 20824. CABLE TV -800-582-1114: FREE CATALOG CUUtANTEED BEST PIIICES ' lUMEOlATE SHIPPING ; .M.K. ELECTRONICS. ^^ Pjcnl 0362 Pines Qivd. Suite 3TG vnZ^4 Pembroke pines. Fl 33024 vSsSSi PAY TV AND SATE LUTE DESCflflMSltNO AU NEW mi mum ali kew Soiintiling Km, ISS? H«r1tl An.. Cable TV > The Ikrft C«tt|}(e1t Line of DntroiRblerf >Frieiidtf, prafeisional lervjct >FR£E Cotalog Go to th« 5ouN6 NU-TEK ELECTRONICS 3250 Hatdi RD Cedar Parte TEXAS 7S61 3 BUSINESS OPPORTUNITIES YOUR own radto station! Licensed unlicensed Af^, FM. TV. cable. Information St. 00- BROAD* CASTING. Box 130-F10. Paradise. CA 95967. LET tfie government finance your smati busiriess, GfafitsioaJis to SSOO.ODO. FJee reco/ded mes- sage: (707) 44&^d600. (K51) Is Bad Service Driving You Nuts? ELECimracs So don't cracli up. Call MCfi Electronics, toll free, at l'800'543-4330 or fax l-513-434'6959- We'll send you our free catalog. And show you how sane excellent service can be. Business gets crazy enough without your electronic parts supplier driving you up the wall* That's why MCM Electronics dedicates itself to customer service. Well answer and service your calls in just thirty seconds. We'll also answer your questions and give you advice. Whatever you need. Then we H use our computerized order entry and inventory control systems to speed your order to you within 24 hours. Of course, you get more than quality service. You get quality parts and components; more than 17.000 of them, all available in our huge distribution center. CAU. TOLL FREE 1-800-543-4330 MCM ELECTRONICS 650 CONGRESS PARK DR. CENTERVILLE. OH 45459-4072 9 RE-79 CmCLE B7 OM FREE INFORMATION CARD 99 1*800-8314242 Your Resource for Test! Measurement and Prototype Equipment Jofiieco SeldarloM Braadboartls pf IHotaiyping -uid dfcuit tlnifs- mcddi fbnirt i hatf-dti^ jtumioun ludungwrdi tiDto^iod fiut No. Frodttci No. COBMCI Polfttl Blntlijii Poses Prkc 20600 JE2I 3,25x2.125 400 0 20712 JEIJ Q 6J5 20757 |04 2 12J$ 20773 JE2S 3 20790 JE2& 6J75xl7S 4 1495 20i1l JQ7 7^x7-50 3J50 ■1 5Z.fS GoldStar lOMHx Dtfcil Tra€« Oscilloscope £rw DC 19 20 MKi^ Tift GoUScv iw^Slos^ wtd) t«A»40MHi pati0> rim fuiev pm-cf cnrd, Dpctaoon Buaiul, icimMtki aad t4oti jjid mm% dG^^. Ii i PmMB. faiJiiCtNa. PoqipttW BdCC mSSl CS7Q20 OicillaK^ Addtfional GoldStar Oscilloscopes Product 660SI GS904RD 40Mhi 1 66077 GSSlOO ItKIMhfJ (Mcilkiivopc^a 349.95 Call for additiomii Goidstar test equipment J AMECO * 24 Hour Toil -Free (^rdcr Hodme Norionol ond Intel ^ Dotabooks Motox Digital fAuMmotofs * .^{ofiLra AOLXI wic^ AO DC curmiE. dmdo, uAfimiffir, ind usbumk omnt gvn (except Mif^OO M365liacM46SO«ilr: * AIkO ixi«4iurci frf«|LKi}Cf and gpiritincc 17115 MUtOO 27078 M.I610 27140 MJ900 270&6 M3650 27158 M4650 J. 5 dtpt rTiuliimctcr»439»9$ di^t multinictcT»»f9.fS 5.5 dipt multimctcf with tach/d wcll . 59*95 3.5 digit niultimctct w/ftrtjLirrlcy Bt capacitiiricc *Kt»**i*.+i*«74.95 4.5 digji wt liwquciicy 4 a.pjc(tafiee at dati halJ >wiiciu^,«99»95 Mt(i50 IC Test aip Series • Tet dipi tlaigiicd &f tcibpcnij cncuKaKifls |o 0]? * Hei^f'ifinf qinnf la»ded Iue^ pniriflD pnimccDiitKt rrci6 1 6-pin PflC* fix iH&l&fiRlO) S5,9S 22110 JTC20 lO-ptn ^ 6,95 22146 fTC24 24 -pin —,....7,95 22162 2«pifl .,,,.^95 221S9 jTC40 40-fin„„„.„«^^.. n « EPKOMs - for your prograntRitng noods PmNa. P»d«iNdLDtiiJifti«i Price Pan No ■ Pf oduci No. 55566 402a 2764A-25 15.49 65904 27C25&-I2«^49 53601 TMSIS64 - 59A29 27C64-15.«™5.95 59714 27C256-J5 S.95 53£ll TMS2716«« ^5.95 39*45 27C64 25— 59722 27056^ 20«, J7647 I701A « ^.95 39«53 27G&4*45— 39751 27C25fr25^ 4.95 39909 2?m ^ .^4.95 3W2 27l2aOTP 2.49 40184 2751201T«. ««4.95 40002 2716„«^ . 59925 27128-20..«* «...7.9S 40)50 27512^20 ^. .»6.75 400n 27lf^ 1 .«.4.25 54933 27128-25 .....7.75 40 168 27512 25. .«5.95 39706 2n:u\ ..,.4.25 59950 27I2HA-I^ 4.95 3?>773 27C/II2.1].. „.7.4S 400% 27 ,...4.95 5996S 27liaA-20*, 3*781 27CSUJ5,. ..,6.95 40109 27>2A iU ....4,49 599^4 2712BA-25,, .„J75 39790 27C512-20- -.,6.49 40125 2732Ai5,.... ...J.49 59677 27CI28'15*, ...,575 39B02 27C5l2-25.« .,.5.95 40133 2732A-*5.«« ^X95 59685 27Cl2i^25« «..J.95 39651 270010 I5« ™9.95 39765 27C32 ,^4.95 40O70 272560T1'.. «...4.19 65699 270020 1 5«. .17.95 40192 2764*20™ 40037 27256*15...., 5.49 65681 270020-20- .15.95 40205 2764^25. 40045 27256-20 „„.5.29 4J692 68766-35.-- »«4.9S 40130 2764A20*«« --3.75 40061 27256-25-^ ..^4J9 41224 400026 41259 400039 41208 40OOL5 41504 400101 Ndtiocul Gcoenl PtupoK licetr Dnim Dai3i»c]LS]9.95 Diuk»k_ 19:95 Au|uliiii^ Put poic Lui£^ [ Wcf Da£d»(4^ 1 1 .95 Njtwcul LS/SHTL D^ubwilr ,l4.f5 Djubook 24,95 41275 4Q0O44 392S0 1J084J J9t70 270645 A.R.T. EPROM Pregrammer UVP EPROM Eraser 27512 OAfr plia the X2fl64 EHFKOM * RSl|2|i«>n PwffCaL Pfoityrtr^lft. Da cfyioa Prioi: j 15712 I66S6 EFT PrD9f3nuner_S199.9S ^ 6«o42 ■ DE4 frixi A chip^ otij 21 mimiitD DF4 DEI I'«i^Ef»ii^49,9S • Partial Listing • Over Electronic and Computer Components in Stock! * Call for quantity discounts* CIRCLE 114 ON FR£E iHFOBMATtON CARD Value. Only a Phone Call Away. Compzitei' Upgi^ade Products and Elech'otiic Components 1 Upgrade your existing tamputer system! Jameco wiU help you upgrade easily and economically. 1 01 -Kfty Enhanced Keyboonl Mmmmw S03S6SX Motherfaotml curKJf ajid numerk ktyt, • IBM POXT/AT inJ cttmpitibk cD[ii|>uim • Autnmatitilly iwi[chci iKmiccn XT of AT • L£D Indkitiin br Nufii^ CipMtid SduU lock hrp^. Part No V Pnxtnct Xo. 67411 KlOl Toflilba 1.44MB 3.5>* littoffnfll floppFy Disk Driv* • IBM rOXT/AT fni ampmbici « Giinpii^ Hntiii DOS vawu 3 J oi Ivf^ • 72IHCB Amnsiol W (kmicf fnoJe • Sor rH * 4*^ » 5.9'D (Ktuil Jirre uaj Price * Baby moihcrboiid {It.^'il 3*) * Irttt 01 one wiji mii vpcnma * Su^m up [0 \6MS ^n^M * Inrd SOJiTSX/csmpuible miih copracci^ ifidtft < AMI BIOS * S» ]&liit md rwp S^bii cxpaaiHxi Ixa ikici PirtNo. Pf&diKtNo. Description Pfj^ y IFif.lf^SN JcHii#co IBAA O>iii|Mililil0 Powor S4^ppli#s -Edfic J£]a34h • Ompst -SV 8 -5V * O.SA. • 1 50 warn nutp^ pQ^xr • S*m*ui>kbCTw«n n cue , , S.12 28644 PNI907 TO-92 cuc_„ ^32 3599 J 1K40» DO-41 ™30 38236 2N2222A TO- 18 cue ..^ -25 36126 1N4735 DO-41 cnc a5 3§359 2N3904 TO-92 C3ie_ 12 362M IN7SI DO 35 CMC 15 38421 2K4401 TO 92 aa^^ — .35 36038 1N4I48 DO-35euc„. 38508 2N3055 TD-3C2M Switches Pmit Produa Price 21936 JMT123 SPDT. on -on iio^t). -.31-15 38842 206^ SVS'l\ l6-p(n (DIP) .-«1.09 26622 MS 102 ™39 Part No. FwKtwa 41398 41256-120 2561: DIP 42251 5noo&P-M 1MB DIP 4!5Z3 4i256A9B-S0 256IC51MM 41718 42100aA9A-£0 IMBSIPP 41769 42iO0QA9&^ 1MB SIMM AAemo^^ .^$1.69 1,99 _ 1 6.95 -«S4^ --54.95 UDs Part No. Pmdmrt No. Docription Pfia 34761 XC556G T1 3/4, (Gicen) 1.16 34796 XC5S6R Tl 3M. (Rrdl — -12 34825 XC^5GY Tl (YclTtjwl .16 Call or write for your 1993 Annual Catalog: 1*800*637^8471 24-Hour Toll' Free Order Hotline: 1«800<831*4242 J AMECO COMPUTE R PRO DUCTS 1355 Shorcway Road Belmont, CA 94002 ^ $30.00 MintmiuQ OrdUr FAX: 1-8O0-237-6948 {D«™i FAX: 415-592-2503 nn^m-.«j) Jimcco SctviccLoc"* : Technical Supporti I *B00*83 1*0084 BBSSuppon:4l5'637'9025 For Intcrna[i(>n.il Sales, C 'us 10 me r Scmce. Credit Department and all other inquiries: Qli 4i^-V;2-Ha97 l>cim*cr^ 7AU^5VM P.S.T. CA Raidenis pinif acid jppliuhle uin [UpS^ iA»u.raiKc lie Termi: Pfko lubjcct to dwigc without notice, [tcmi lubjicct 10 jtrjikb^iy tad piiof talc Con]|i^jcic ]h|: of termi/wimaHei it nnrtiliyc 9 !99^jMmfrv tOfSi All mScsaitu ut r^jtfcnd mdcbuiu of tbsr CIRCLE 114 OU FREE INFORMATION CARD FREE CATALOG! 1-800-648-7938 JERROLD HAMLIN OAK ETC CABLE TV DESCRAMBLERS • Sp^f D^Qf&r Pricss! • Compam our Low Remit PrjcBS* • Guamfimd Ptm^ & WafmntiQs! • Ortiors SNppad Immediatetyi BiPUBLiC CABLE PRODUCTS. IKC. 4080 ParatJise Rd, ii5, Depintio^^ rzjk Us Vagas. NV 89^09 For an ottier informailon (702) 362^9026 CABLETRONICS CONVERTERS 1 -4Unl t» 5 Units 1 0 Unl ta PANASONIC TZP 1« STARGATE 2000 ^HAMLIN MCC 3000 $88.00 $79.00 $25.00 S75.00 S70.00 569.00 $65.00 $19.00 $15.00 ADD-ON DECODERS &B-3 (NEW) $50.00 $45.00 *SB-3 FACTORY $45.00 $39.00 SA-3 S56.00 $50.00 DTB-3 $65.00 $55.00 KNI2A-2or3 $49.00 $45.00 •"HAMI LIN MLO 1200-3 $49.00 $40.00 *ZENITH SSAVr $1 65,00 $1 49.00 SA^DF $159.00 $139.00 OERROLD DPV7 JERROLD DPBB SAesSO COMBO •JERROLD DRX-3-DIC JERROLD DR2-3-DIC *OAK M35B HAMLIN SPC 4000 3M ADD $1 0.00 FOR VAHISYNCH COMBOS $299.00 $319,00 $299,00 $165.00 $175.00 $45.00 $50.00 $149.00 5259.00 S225.00 $105.00 $115,00 $35.00 $44.00 $43.00 $35.00 $46.00 $50.00 $40.00 $35.00 $125.00 $125.00 S239.00 S249.00 $215.00 $69.00 $99.00 $30.00 $44.00 *Befurbl8hed as New OTY IIEM CXJTPUT CHANNEL CAlJrornla Penal Qodt §B9^0 Forbldt ui from ■hipping any cable d«sc rambling unit to anyons rffsldlna In the ttate of califomlB. Pikas iubject IP chaJtgs without notice. Please Print PRICE EACH SUB TOTAL Shipping Add S.00 Per unit 300/0 wttlCard Add 5% TOTAL TOTAL PBiCE AddrKi_ Stale _C»t¥_ _-Sp_ O Caihier's Ch ^Iv □ M o/rey or def OViM OUC CCi _Tet:{ J_ □ goo DECLARATION OF AUTHORIZED USE- 1, Itie undersigned, do hereby declaie under penalty or perjury thai all products purcliaiad. now and In ffie tutuie, Mrill onljir be used on TV SYilemi udt^ aJi appitlcai>le fedv^ and stale laws. FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL CRIMINAL AKD QVIL PENALTIES FOR UNAUTHORIZED USE. Data _Slfin&d_ Cabletronics 9800 D Topanga Canyon Blvd., Suite 323, Chatsworlh. CA 91311 For Free Calalog, or to place an order call (800) 433-2011 * FAX (818) 709-7565 EASY work! E)(coEienl pay! AssembEe prtKluds at home. Call ton Irge 1 (flOO) 467*5566 Ext Sl92. HOME assembly work availabEc! Guaranmed easy fDorieyr Fme details* HOMEWORK*a Bfix 52Q. Dar.vite. NH Q3fll9 UONEYHAKERS! Easy! One marr CRT f^tCd- irig machmcr^'. 00 retjuiti. $15,900,00 r^ew. Cm, 1909 LotJtse, Crystaiake. tL 60014. (aiS) 477-8655 FAX (815) 477-7013. MAKE S75, 000.00 to S25€,O0O-O0 yearly or mofO fixirvg IBM color monilors. No investment, si art doing ]| from your homo (a lelephoRD r&qLrred). Tnformaticn. USA. Canada S2.00 cash for bro* chyre. oiher counlrios S10.OO US funds. RAN' DALL DISPLAY, Box 216Q-R. Van Nays. CA 91404 USA. FAX (819) 990-7803. FREE CATALOG • CABLE T.V. BOXES - ALL TYPES • . LOW PRICES - DEALER PRICES • Ace Products 1-800*234-0726 CONTINGENCY paieni licensing. No fees ariy- time. Three d&cadoseKperierice: law. technoloavH neqoiiaiions. PROPAT INTERNATIONAL COH- PO RATI ON, 441 Summer Streei. Stamford, CT 0G9Q1. ^203) 325-3344. LEARNjjofd, stiver platinum scrap recy ding busl- ine ss. (Free) informaiion. Write: RSCYCUNG, Box naifiPEn Reno. NV 89510-1216. ELECTRONICS dealers: Expand your product line. Make «S! Bocomo an AMERfCAN ELEC- TRONICS dealer? Prolii oppof [unities since 1965. Gait Scon Pruell. l (600) 872-1373 S Millions on inventions secrets. Send S.A.S.E, and SS.OO payable Cart Hujriphr^s, lo INVEH- TION MILUONS. 3012 flax. El Paso. IK 7992S. « -tr «^ PRESEAmiWC ^ « « ■« CABLE TV -«r-«e«^^ STARRING JERROUI, HAJHUN, CMK AND OTHEff ¥AMOUi MAWLIfACnWE « » FINEST WAJ?RAINrtY PKQGUAM AVAILABLE * LGWEST RETAIL ia-HOtESALE Pmct% IM US * OIS>ERS VJ-HIPPEO FJ?UiM STOCK WmON ?4 HRi ■ AU MAJO» CftlDlT CARDS ACCEPTED FOR AU INFORMATTON im-usmj PACIFIC CABLE CO.. INC. 732S'/ Reseda Blvd., Deot. 2UB Reseda. CA 91335 BEST BY MAIL BUY JT WHOLESALE BUY 30% ^ B0% Below WholMiK Apparel ■ Eiffctitmles t5 95 • BGULOS. Box BOg?> Shwrw Qa^s, CA 9Un. 11500.00 A WEEK A' f"c-:e Fcr Fro^ r^lcTr^lion Sers^A Stamped Envokipe Id: Amencaj^ Dream. PO Box 1S33-1, North Wlw, PA 1ft*54 m£& SGGONO IN COMET?? Oatatls S99e: Thomas. 6dx ISBOI, .Jaefcfcinvjnp. FL 32245^sa01. ASTfiOlOOY CHINESE HOROSCOPE 1-90lM4*06l1 12 00 Per Minut* ia + LH Sor^lCdfS, F(. UuderdaSfl. FL 33308 {30^)564-2022. EDUCATtON & INSTRUCTION FCC. CommefC^al Gen oral Radtotclepbone li- c&nso. Elocironjcs hofne study Fasi, inexpen- sive! "Free" details. COMMAND, Box ^4, San FfandSCQ, CA 94126 iLECTRONlC engineering. 8 volumes com- plete. Si 09 ^5 He pr,or kncrft Sodgofequired. Free bfOdiure BANNER TECHNICAL BOOKS, 1203 Grant Avenue. Rockkffd. IL 61103 ^TENT rt yoursdf. Ejltminale huge toes. Com* pleie Dfaciical snsifueliofii S9 JS: PATENT aUlDE. PO Box 654. Gumee, IL 60031. LEARN electronics and digital basics. Pm- grammei^ courses. Si 7 00 each, both S29.00. Satis lac ton guaranieed. TEK SOURCES, 6050 NW 6Blh St., Parkland. FL 33067 SAVE $ importing radios, otoctrontcs... directly frpm manufaciuiefs. For business hobby. Guar- anteed easyl 52.00. MtNTER ENTERPRISES. Box e002'R. W^tchesier, OH 45069. I FUl-L- OR PARFTLMK J OB BUSINESS: I Learn VCR repair! Pmfessiorial-Je%^l home study program. Master easy-to4earn, high -prof it repairs without investing in costly hi|jh-le<:h instni- \ J , ments. Send or caSl today, * i Free career kit: j I 800-223-4542 M I riiiiif ^ I Add rus5 I City. .Zip. I Tlie School of VCR Repair, DepL VL342 ^ 2245 Perimeter f^rk. Allanta. 3034 1 MUSICIANS, buikj a Ngh CfuaMy digilai delay, S10.00. very high Quality dyopfwnic synihesiief ~ 510.00 KEts also availabte. GEBHAftOT Box 754. Aj^aconda. MT S971I (406) 563-7506. BUILDING A Robo4: A Strawhtfoward Appccach. 152 pages Jully illusiratod. Tn si ructions how you can oasily construct a robot, Check or money OfdOf. S\9 95 plus 53,00 shipping, HUM ANFORM flOBOTtCS. PC Box 15848C Nashville. TN 372^5. BUY BONDS MC / COD / VISA iSlO FLORIDA SALES CABLE TV DESCRAMBLERS WORLDWIDE CABLE • BASE BAND ■ POf^R • TOCOM • ZBirm • SC^TFC ATLANTA • OAK • JERHOLD ■ HAMUN 1 800-772-3233 I Sai A POWERUME ROAD, SUITE 103 POWPANQ BEAOH. FL 3306S CABLE TV DESCRAMBLERS * CONVERTERS^ and ACCESSORIES. PANASONIC, JERROLD, OAK, PIONEER, SCIENTIFIC ATLANTA AND MORE. LOWEST PRICES. FREE CATALOG. CABLE READY COMPANY (800) 2344006 TumtaNfl m sp&&d repair d VCfla. TVs Andmon. L«t» toctnevrt a«v4y turn unt for cemrntnt r«par. 20* Whto color l^el w^t: Super Horn Tweeter TJi& original pio;o Iwoetuf mrinufaclEirod l^y Molorola. 2.e3V/lM. 2&.30 malelv lo walti} powflr tuindlino PftKJucttf cntp. cl0«n highs. Technician's Turntable Ptezo Super Tweeter f \ ^naB tweeter ^^^^^K [ ] ncofporiteS ■!! th« ^^^^H Frequfl'ncy rosponte: BBC 12" Dual Voice Coil Subwoofer Si^iQf qyajgty itaion i¥iBd* cast frame tSuai vtHca cod »i10 SS» $4" $3^* 11079) (eO-i^iJ 8" In- Wall Subwoofer 0* ptfitit corM sutiwootor wits potyriof iMm ODNAfei^ OuMl w^ott' CDlb nwi B ohm irT«tdai)^p«rcoi^ PM4|AMeipefili«r " — 'UUHZL __ r hamflkx) capMbtfily SK-20KHI. SPL: 97„ tiantfiuig 80 vraita RMS. wt>e9^ pOw*f ^1 slereo systoms and tor >ii;_4^ in SKlj-dmAly long ^ cable mns Ov«r25o slrands of S6 ga wiio E*3Ta tfjci. ci^ai PVC Mt&ulatioa Please eiij^^n multSplkit of Staet. iRH*100-151 MdBlW/IM. Dimensions- nuionsa: 30-500 Hzl SO iMOlts RMS, 100 watts m^i !0-5/8*tW) HW(U 1 3" hkrio dkmensiorts: 9 (W) N*1w $79^ (1-31 340 E First St, Dayton, Ohio 454C»2 Locah 1-513<222*0173 FAX: 513<222-4644 VCR Parts Assortment Fiaqtjancy response: 45-tKMi SensiiJvrty; 06.69 1W/1M VAS' 3 73 cu fl . OTS^ 33a. BBC iSW32?/Fa Net #RH-294-130 assonmcnl ot dips, wssh«f$, ^P'l^^^ sc/Bws. 10 pwc as eacti of 4 $iz«& d *E~ rings. 10 pieces of 14 »iz»s of waiJiefi, 2 eadt of 0 iteas qI tension and conifNttssion spnnos and ?4 assorted scrowf. Tola! nl 34Q pieced. SI 39® (1-33 $128*^ #nH-430'315 S6» Ci'3) 8 Ga. In-Li $5* ijp) Suction Cup Mount Fuse Holder Cellular Antenna Dw fooytwr BitoMe tiae ixAfaf wiii Q iwife For iiaa mMi AGU lyps hiM« Of reguUir AOC ham nvtion spring spauf it SO amp ma« at 12 wafts S2« The ideai anJenna iot ponab^e phones Suction cup grip mounli on inside of car. Mevor tuve yOMf oar vandalize ag^. Anlenna coRUK with 9 led of RG-S6 w«fiTNC connector, 3 dB gain. Made in the U S A iRH4)70^ iRI»SS-200 4 30 morHy bac^ guaranty ' £20 00 niifurnufn order' We accept MftStercoidt Vna. Dr&covt^r. and C O. 0. orders. • 24 twur sfiipping ♦Sfi^jpingctMfgo ^ UPSc^iart rale + ST 00 ($3.50itiinimumcf*ai99j • Hou» ®:30 *rn - 7 iX) pfn EST, ^toniiay - Frtday - S 00 am - 5 00 prri Saiufday. Maii ofder aiilomers, pfeas^ cal fthf)prig es^^ on ordwt exe«e<^ 10. 22wf 4nd 2 piecH each of 33. and 47uf , 250V radial eapa. 5pf^^^:Orbf mm 603-6734730 FAX 603-672-5406 IICVISA,C00, Check Accepted. AO0S5S&K 24 Kr Ofdtf Phone: 80O-22M705 Laser Pen Pan sii«d iasar, gn»i lor movies^ drive- ins. poirtfsr Rsajy lo use, -1 lOlof St.SO- lOOtof $13,00 GREEN CATN LED-2 10 ter $2.00 • 100 for $1 7.00 YELLQW CATN LEO^ 10 for $2.00 * 100lor*17,00 REDUCED PRiCBS FLASHING LED W/ buit In flashing cirojlt 5 vol; operalkvi. T 1-3/4 (5nnm) RED &0« each CAT#LED-4 to for $4.75 GREEN 75c eadi CAT# LED-4G 10 lor $7,00 YELLOW 75« each CAT* LEEMY 10 for $7.00 LED HOLDER Two piece hokJer. CAT# HLEO 10for65e ELECTROL UMINESCENT BACKLIGHTS Autormtivo Cigar lighter p^ug with ref)la09db1e 5 btt^ Tu««, CKiality, retractable coil cord extends to approxImaleV 3 leet. terminates with a 5 pin OlH phjg which can bo cul- oft. Ideaf for banary chajger Of ornning 1 1 2 Volt devices from car battery. CAT* CLP-IS $ 1 .50 each - 10 for $1 2.50 D.a Walt Transformers (120 Vac INPUT) At lasll AkwCD^l etectrotuminesoenl gbwsirip and Inverter. These brand- new unhs were desigriod to bac^klight srr.ajl LCD TVs made by the Git lien Watdh conpany. The inverter drcuft changes 3 or 6 Vdc to oppro^^ Im^iTely 1 DO V^H the voltage required to tight the gtowsirip. Lumlnooosni aurfaca area Is 1,7* X 2,25*. ThOElrlp is a saJmon coEor In He oH state, and glows vrtiito wtien energized. The circuit board is 2.2^ X r. Glow strip and drcuhry car) be removed easiSy from pla&ilc hou&ing. Ideal lor spedal lighting etfedSr Citizen* 92TA operatea on 3 6 Vdc CATfBLU.t2 $3.50 each LARGE aUAfnJTY AVAILABLE 10 for $32.00 • 100 for $275.00 Monoral Equalizer Plufl St Yt« Pt1« 4 Vdc 70 ma. 2.5 mm co-iw negative [>CTX-47tJ IZOO flVdte 300 mo. 2.1 mr n CO- ax positive DCTX-KJa $Z75 e.3Vdc to ma. battery DCTX^IO $1.50 9 Vdc 300 rt^ 2.1 mr n cO'a:K poehlve DCTX »32 $aoo 12 Vdc t oo ma. 2 J mr pcoax negative DCTX^1210 $2^50 t2Vdc 500 ma 2.1 mr n CO- ax negative DCTX-125 $4.50 12 Vdc 800 mi. 2,5 mr noo-ajt positive DCTX-1281 12 Vdc 1 Arrp none DCTX-121 S6.S0 14 Vdc 700 ma. 1.3 mr n Co- ax negative PCTX-147CI $5.25 IS Vdc 400 ma. 2.5 mr nCQM negative DCTX-1540 $4.50 SB v£fiYSPEaALOEAL 1 w WATT SWITCHING ";^Sc^S" , POWER SUPPLY New 17 Vdc. 210 ma wall iransformofs. 6 ft. cord. Unusual co-ax la! device On end of oord can be cut oil and used lor another application. Large quant t;/ avarJabte. CAT* DCTX*1721 $1.50 each 100 for $1.25 eiM:h 1000 lof 11,00 ftach Rechargeable Batteries (nickehcadmlum) Five baAd graphic eQuaizer. AJbwG use of one source for bad^groond muafe and muslc-on-hold, Albws you to equalize and adjust the volume of one without changing the other. Us etui in any appfi- calbn where oqualLiallon of a monorai source Is des rrab^a. RCA |adk inputs and outputs. Ren^ovatJle met^ oontrol cover lo prevent tampering. 6,75' X 5.75" X 3.125- high. CATi EQ-1 $15,00 each 10 AMP SOLID STATE RELAY (USED) tOwrp solid stale relays, removed from equipment and tested. iDontfol vo^tagu: 250 volts AC at lOarrpS. Standard 'hock- ey- piick" size: 2.27- X 1 .TT X 0,95-. UL aiHl CSA l^ted CAT*SSRLY>11U $a.25each - 10 for $30.00 LCD Display • 40 Character X 2 Line BCWATT Computer Products « Xl4O^8301 Input: 115™) Vac Output: -12 VdccU i XL50^S6dl Inputt 11 5/230 Vac Output: -12 Vac #1,0 A 12 Vdc 1,0 A 5 Vdc @ 6.0 A Regulated twHcbing power sui^pV. 7.75* X 4,25' X 1,78' high CAT* PS-Ttt $20,00 e*ch 12 VDC STEPPER miOR AAA 1.20 leOmAh ik:&j^aa $1.50 $13*50 AA 1.20 600 mAh >*C&^A $200 $1S,50 AA«r/ SotdBfTcba 1.20 600 mAh NCB^AA $2.20 $20.00 1,20 1200 mAh $4J^5 $40.00 C 1.20 1200 mAh NCB^ $4.25 140.00 C Heavy Duty 1.25 leOOmAh MDm:B^ $5.25 $42.50 0 t.20 1200 mAh NCB-D $4.50 $42-50 D Heavy Duty 1.25 4000 mAh HOHCB^D $7,00 $65.00 Op«rex f DMC40218 or HItacH # LMOISl Buitt inconiro^rar>ddrTvers.4 Of fibll operation. 5 Vdc power. Dl^lay size: 8,05' X 0.7" ii^oduie size: 7. 12^ X 1 .34'. Character ske: |SX7do£Ej 3.2mm X 4.85 rrni. Data sheeis and irtemjct'onsavflaable. CATJLCD-^ $l5.00eadl Alrpaxi A83712 M1 1 2 Vdc. 36 ohm oof 1 15 degreei'step. 2.25'dia,X0.9SMhic< 0.25^ shah X O.e- tong. CAT«StfT-i $6,00 each ORDER TOLL FREE 1-800-826-5432 Call Or Write For A Free 64 Page Catalog Outside the U.S,A. sand $2.00 postage. FAX (818) 781-2653 ■ INFORMATION (818) 904-0524 Minimum Ordar $10,00* A\l Orders Can Be Charged To Visa, Mastercard Or Discovercard • Checks and Mormy Orders Accepted By Mail • Cafifomia, Add Sales Tax * No CCD. - Shippmg Arid Handling $3.50 for the 43 Continental United States - AH Others tnduding Alaska, Hawaii, P.R. And Canada Must Pay Futi Shipping ■ Quantities Limited * Pri^^s Subject to change without notice. MAIL ORDERS TO: ALL ELECTRONICS CORP • P.O. BOX 567 • VAN NUYS, CA 91408 105 ORCLE 107 OH FREE IHFORMATtON CARD "CABLE BOXES" BELOW WHOLESALE GUARANTEED STOCK - COO'S 106 DESCRAMBLERS (QTY) (10) (20) (40) NEW TBI-3 70 55 CALL TB 2 or 3 45 40 CALL SA 38 45 40 CALL OAK N^12 43 38 CALL SB 2 OR 3 43 38 CALL COMBINATION UNITS DRX^OIC 89 CALL SYL DIG 59 CALL PIONEER 295 275 CALL - CONVERTERS Wm EMOTES - PANASONIC- TZPC145 65 60 CALL STARQUEST^ E-Z550 65 60 CALL E-ZY550 75 65 CALL TM£FT OF 3EHVtC£ IS A. CRIME IKSTALL^N3 ANY OEVCE WITHOUT PERM|-S&tO>* W^T f^UEJJfCt tOU TO ClVJL Ofl CniMINAt, PENALTIES VOU MUST CHECK WITH tOUR LOCAL CABLE COMPANY ANO f*AY FOFI ALL SERVICE VOU use IT IS NOT ThEfNTENTOFlAKE SYLVAH TO E^EFnAUDi ANY TELEVISION OPEflATQF! AhO WE WILL NOT ASSIST ANY COMf*ANY OH INDJVIOUAL tN 00\t4G THE SAME LAKE SYLVAM SALES, INC. SORRV NO M(NNESOTA SALES CALL FOR A CATALOG NOW!! 800-800-4582 QRCLE 176 ON FREE INFORMATION CARD THE ELECTHONIC GOLDMINE electrwic us Miii^ in ofli !i& bte and IKFRAR£0 DETECTOR K.rt C6441 $5." 0 t^^s- IHEXPENSn^ CEtO£ft couKTER mr [>ii«di! bati Bd.i tf.i C^rrri, Hjij* C6447 S39« PRECmCN mCH SPEED G2>H> r^' Eil lll:S.'* ;atai.og G2741 MUSIC MODtJLC ^nf fid rur. paijf ThoEO fiv t:^^ piw R ci^iii»a4 ^pe mr.t< tfrt m^Mtl mq yrij ^ 1..\yir El^l*ry rut nOvi^oO bt< 0[> .v. , , 87 ^ Comniatid Productions, ....... 8.1 127 Dcco Indu^strivs 87 188 Electronic Gold mine . . _ . . l . . 106 — Kk'ClroniCs<> Book Cluh 7 — Electronics Engineers lt*C» , , . , 2H 121 Flukt Manufacturing , CV2 — 47tli Street Photo 34 182 Global Specialties .3 189 Goldstar I*reclsioii IS — Grantham College. ........... 59 86 Heattikit 9(1 — Hij^hText Publications, Inc - 1 7 — tSCET,... 16 U4 Janieco 100. 101 183 Kijliin, _.5 178 Kepco Po>*er Supply 86 1 76 Lak e Sy I ui n Sales, Inc 106 197 M&G Electronics , . , 104 8? MCM Electronics 99 53 MD Electronics 104 93 Mark V, Eleclronioi 98 1 17 Mouser . _ , 86 — NRI Schools. . . , 18 71 NTE Kleclronics 23 IHl IK6 180 56 184 179 177 192 190 195 191 Northeast KlfCtriUiics 83 Nu 111 Iter One Systems Ltd 93 Oploelcctnuiics CV3 Parts Express 103 Ftop|e*s Crollege 46 R.E. Video Offer 95 Star Circuits 87 TECI ..96 Tech Spray , , , 12 ilie SPEC-t OM Journal 26 ILS. Cable ,.. Ki Vtejo Ihibli cat ions 82 Xandi Elcclromas H7 Zentek Corp. 81 ADVERTISING SALES OFFICE Gertisback Publicfiticinsi Inc. 500 B Bt'County Biwd, Fai-miitgdale, NV 11735 1(5163 293 3000 PTesident: Lnrry Sleekier For Advertising ONLY 51B 293 3000 Fax 1516-293 3115 Larry Sleekier publisher Christina Estrada assistant to the President AHine Fishman t)dv£rrtjsing director DenSse MuN^n advertising assistant Kelly McQuade credit manager Subscriber Customer Seniioe 1-800 '288 0652 Order Entry for New SubscHbera 1-S00999'7i39 7:00 AM ' S:00 PM M-F MST ADVERTISING SALES OFFICES EAST/SOUTHEAST Stanley Levitan* Eastern Advertising Sales Man tiger Etectronics Now 1 Overlook Ave. Great Neck. NY 1t021 t 516-487-9357. 1*516-293-3000 Fan 1-516 487-6402 M10WEST/Texas/Ark«insas/0kEa. Ralph Bergen. Midwest Advertisir>g Sales Manager Electronics Now One Northfieid Pfaia, Suite 300 NorlhfieEd, 11 60093-1214 1-708-446-1444 Fax 1 -708-559-0562 PACIFIC COAST/Mountain States Artine Fishin<)n 500 B 8i-County Blvd. Farmingdale. NY 11735 1-£St63 293-3000 FaxV516'a93-3ll5 EN Shopper Joe Shere, National Representative RO. Box 169 Idyllwild. CA 92549 1-714-659-9743 Fax t'7 14-659-2469 CJRCLE laa ON FREE INFORMATION CAflO You want a bargraph & a full range counter - Pptoelectronics can deliverf BLEMO 111 lJiT-3Ttf- *1 ^ Now for a limited time only. Si 60. off the list price, for our Full Range Model 2810 witfi 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 TAIOOS; Tefescoping Whip Antenna.,*. .$ t2. CC30 Vinyt Carry Case,... S 15. BL28: EL Backlight for use in roomlight and low light .S 45. TCXO 30s Precision i.0.2ppm 20 to 40"C temp, compensalod lime base ....$100, Universal Handi-Counler" Model 3000, S375. and Bench Model 8030. S579. Both offer frequency, period, ralto and time intervaL Call for free catalog - Factory Direct Order Line: FL (305)771 -2050 • FAX (305)771-2052 5S21 NE 14th Ave, • FL Lauderdale, FL 33334 5^0 Ship/Handling (Max. SlO) U.S. & Canada. 15% outside corttinenial U.S. A, Visa and Master Card accepted. CIRCLE W ON rREE INFORIMTION CAtiO TheDMMour customers desisned. fiufBcffmHofsfgr Before we built the new generation IJcckman InclLisirial Series 2000 DMMs, we asked people like you what you rmliywml. You want more. Mc)re test and iTieasureiDeni capabilities. Moa* imiible-shooting features. All in an affordable hand-held Vmi The Series 20CK) features the widest ninge PrequenCT Counter in any professional DMM. a full-range Cajxicitance Meter, True RMS measurements, Iniermineni Detection, 50ns Pulse Detection, and Pc*;ik Measurement capabilities. Plus, the Series 2000 Ls tlie only meter to offer autoianging Min/Nlax reairding and relative modes. You want a DMM that*s easier to use, Tlie Series 2000*s display is 25% larger, %^'ith bigger digiLs and backlighting for easier reading, even in the worst light. Plus the fast 4 digit display provides the Itigli absolution needed for adjusting power supplies anti generators down to ImV. And only the Scries IWfy features a menuing system for fast, simple feature access. il. r,.l. J, MadU in Eht' USA An AfMate Of Emerson Eiectric Co. The lieckman Industrial Series 2000, priced from $209 to $279 olTer.s yovi the best perfor- mance for your dollar. Look again at tliese featunes; • i Digit, 10,000 Count Rescilution • Basic Accuraiy to (11% • True RMS. AC'or AC on DC • O.om Rc*solution • Automatic Reading Hold • 1ms Peak Hold • FuUy Auiorangtng Rebtive and Min Max Modes • Intennitient Detector • 111244. IHCIOIO Design • 'UxTLV Year Warranty The Series 2O0O offers tlie mn solutions ftjr your e\cn'ci;u test and measurement needs. Tlie only I )MMs designed by the pe(>ple who asc litem. You. Ft>r jnore infomiatitm m ihvsc new DMMs call {outside CA) 1-80O-H54-27O8 or (inside CA) 1-800-227-9781. Becknian Industrial 0)rporation. 3883 Rtiffin Rd.. San !>iego, CA mi^im. Spccdk^ w isihiea h> wthoui mtk^ CinCL£ 98 bM FREE INFORMATION CARD