CombinBd with Build this and capture lOtastic ip-action photos with almost any camera! Build a 1 - S - T J v| -i ^ fROL your next project! J Design and build PHI-FI AUOlO AMPS at hard-to-beat prices How to use the 555 TIMER IC in practical circuits i ?5D456HRR5ie5MC53 11 64 HOy 93 We Only Skimped OnThe Price, Introducing The Fluke Series 10 — From $69.- Actual siie; Easy to carfy, easy to use HewlMZh^k"*: For fast accurate checks m power sources and supplies, set your meter on V Chek— and let it do ttre rest. V Chek will (determine continuity/ohms; if voltage is pfies€nt, it wiEl automaticslly change modes to measure AC of DC volts. writct\e^»er is detected, Fdf most initial trout}] eshooting checks, here's Xht only setting you need to make. Fluke quality: Made in ttie USA by Fluke, vMh the same rugged reliability that s made us ttie wm Id leader in digital my !ti meters. Count on hard-working higtv pertormance — and a tv/o-year waf ranty to back it yp. Large, essv^lo-read display: 4000 count dtgital readM. To perform fast continuity checks, just listen lor the beep; no need to mtch the display. CIRCLE 121 ON rriEE INFORMATION CARD New! Min/MaK record with ralative time stamp ani Continuity Capture"*: Makes intermittent probfems easier to find. Records higlis and lows— and "time stamps' when they occurrBd, In coritmuity mode, opens or shorn as bnel as 250 MS are captured and displayed. Capacitante: Aytorangmg from .001 uf 10 99&9 nF No need to carry a (dedicated capacitance meter, ¥nr titgh peitormaiice at Fluke's lowest price, gtt your hands on the new Series 10. Slop by your local Fluke distnbutor and leel what a powerful diflerence the right muilimeier makes— at the right price. For a free product brocluire or the name of your nearest distributor, call 1-800-e7'FHJKE, Sfi99S* 4DO0 conn] ^ SS tustc dc vistls 29% lime ac wits (accuracy it1 €01t3 9999tiF 4000 tmihldiijiur 1.S% biMt 3c raits betpei Oicdeffst Sleep MfKl^ Tw{hy(4ir warranty Fiflit 12 Ccmtinullv Capture!" CioacitarKie, ooiio^ii; 19% basic 4£ ¥011) accuracy Fast cpntin uity ONNltTest " Su^oeued U S itst pnce The New Series 10. A Small Price For A Fluke* 1' 1. K [1 AN n PHILIP S T 11 H T &i M A 1. I. I A N C E Otit) Jehnflul^Mfg Co Jnc Ptiosi FLUKE November 1992 »^ Vol. 63 No. 11 BUILD THIS 31 SUPER STROBE Use the Freeze Frame Super Strobe for exciting stop-action photography. John Simon ton and Trey Simotiton 45 TELEPHONE HOLD BUTTON Add a convenient hold feature to your phone. Bill Green 47 UNIVERSAL REMOTE CONTROL Add remote control to your projects! Fred Eady 57 POWER CONTROLLER FOR AUTOMOTIVE ACCESSORIES Custonnize your car's accessories with the power-controller module. David J. Sweeney TELEPHONE HOLD BUTTON BL'tl D A POWER CONTROLIER 38 COMPOSITE AUDIO POWER AMPLIFIERS Build high-performance audio amps using turbO'Charged composite amplifier circuits. Charles Kitchin, Scott Wurcert and Jeff Smith 61 555 OSCILLATORS Put them to work in Schmitt trigger and alarm circuits. Ray M. Marston PAGE 57 AND MORE 6 VIDEO NEWS What's new in this fast- changing field. David Lachenbruch 22 EQUIPMENT REPORT JPG International TD107 Digital Designer 68 HARDWARE HACKER Distant FM reception, and more. Don Lancaster 78 AUDIO UPDATE Aud io eva luations — a non- mystical approach. Larry Klein 84 DRAWING BOARD Let's build our own video scrambler. Robert Grossblatt 88 COMPUTER CONNECTIONS Gigabyte memory storage. Jeff Hollzman 88 Advertising and Safes Offices 98 Advertising Index 91 Buyer's Market 4 Editorial 16 Letters 23 New Lit 24 New Products 12 Q&A to P fn 2 o 1 Point-and-shoot is fine for snapshotSt but truly interesting pho- tographs require some planning and some extra equipment. Forinstance. if you want to capture spf it-second action, such as a drop of milk splash- ing into a glass, you*ll need either very fast shutter speeds or a good strobe light Our Freeze Frame Super Strobe Trigger uses interchangeable sensors, so that anything that flashes, pops, snaps, or reflects or blocks light can be used to trigger your camera's flash or free-standing photographic lights* The inexpen- sive, easy-to-build Freeze Frame lets you captu re stop-action shots for scientific purposes, or just because they're fascinating to look at. For all the details, turn to page 31, Si I z s THE DECEMBER rSSUE GOES ON SALE NOVEMBER 3. BUILD A HIGH-TECH CHRISTMAS ORNAMENT You'll be sure to want our best-ever ornament hanging on your tree! COMPUTER MONITORS A look at the history, technology, and future of computer monitors. MODEM/FAX PROTECTOR Protect your telephone equipment from electrical transients on the phone line. THE 555 TIMER Sttll more uses for this versatile IC. Ai ■ marvtcv ta mad^n, ELECTRONICS HO^ publiihei nvsi^ablff plint or mitinnfllion r^Isting to n*wiwort^y prtnlucta. ttchniquet ancf sciintiflc and t^ci^nologicjii davDlopmAnti. BouLria nH pasiJbld vflHancii in the qujihty and condition of mftttdAlt and worfcmenihip u&id by rftadert. ElECTflONtGS HOW dtsclaLini any rttponiibilJiy fur the ufit and preper functioning ol rsadtf -buiit prpfvcU turud upon or from pbni or information pub^ithtd in thii magailntt. Sine* uma of Un« Muipmant and circuitry d«tot satisfied, I may return the books within ten days and have my membership cancelled. A shipping/handling charge £^ tax will be added to all orders. If you Miocl 2 boo*, thai couT^ 21 2 chocn. «T);a tn* book rtumDef ^1 on^ oo< &r^j )U m ttm rmA. H Tfou M * Bte to CiAGGK tnc, PULSE SnOC II CMer Charge my □ Visa □ MasterCard Account No. , Exp Date / Credit Card Sjg nature No telephone OrtJers or CO D. Signature re- quined on credit card orders- Air pric^ irKlude postage and handling Payments in U S A funds onty. New York residents must rnclude hxaf apftotsle sales taxes. No foretgn orders Maif orders to ClAGGK Inc. Pulse Suck 11 Offer PO Box 4099. FarmingdaJe NV I J 735 Teleptione orders to I 1 h*293-3?S I . FAX orderito I -5 16-293-3 ITS. you're talking about so I can't sug* gest a better way to get the putses from the engine. Optical stuff is okay but it seems like a bad choice for an engine conr^partment since there's always an oil nriist and other grunge that can interfere with the operation of the pickup, Magnetic pickups or a Hall-effect switch would seem like a better way to go. If you have solved the problems of dirt and alignment. I'm surprised you're having a problem with the level of the pickup output. It's an easy one for you to solve if you're using CMOS. The circuit shown in Fig. 1 is a simple amplifier that witJ work well with just about any phototransistor The layout isn't at all critical, and you can put the whole thing (minus the phototransistor. of course) inside a sealed plastic box anywhere in the cat The 741 is a readily available op- FIG. 1— THIS SIMPLE AMPLIFIER will work well with just about any phototran- sistor. TTie 741, although designed to op- erate with a split suppty. will work with a single-sided supply as wetL amp that was designed to operate with a split supply. But since you're only dealing with ons and offs, it will work well with a single-ended power supply. I've shown the input voltage as 9 volts, but if you've got regulated 12 volts available for the CMOS circuit- ry, that wrll do just as well. I suggest that you look at the 741 output on a scope and make sure the pulses are well-shaped and low in noise. CMOS is noise tolerant, but there are limits. If you see lots of glitches, run the 741 output through a CMOS gate before sending it to your ta- chometer. If you have some extra gates available, you can use one of them. If you're going to add a gate, use a Schmitt trigger such as a 4093 NAND gate or a 4584 inverten The inherent hysteresis in a Schmitt trigger will to clean up messy pulses and odd circuit line noise. R-E 48 HOUR ELENCO & HITACHI & B+ K PRODUCTS cal\7oufree i 1-800-292-7711; SHIPPING p^j DISCOUNT PRICES 1-800-445-3201 (Can.) ELENCO OSCILLOSCOPES S-1325 25MHz $349 Dual Trace Oscilloscope SO 340 40MHz $495 Dual Trace Oscilloscope S-1360 60MHz Dual Trace, Delayed Sweep * Autonnattc beonn finder §775 •34jitf4nc omp 0 nent tester # ImVsensitrvity • Ouoi time Dcsa 8+K OSCILLOSCOPES 2120 ' 20MHz Dua) Trace S395 2125 - 20MH2 Delayeterftai Linear 4 Log>: S«eep Fund Ion Generator Blox #0600 S28.95 PTOTidfis tin*. Iftw^t*, «jyaj# Kft waviliomlHitemHi $26,95 AWofFycapafeaiy Loom to Sulld ond Program Computers with ttils Kit >nc^u^«^ : All Parts. Aiswnlily amid: Lesson Ua^iuai Model MM^aooo Elenco Wide Band Signal Generators $129.00 H^OUlt and run m OOAS metoffoomscr, whch uus SG'90Q0 $129 mK-iSOUm AM UodUa^ 5G-5500 w CHgtui DispCsy & 1 SO WHi bulIMn Counief XK-500 Digital / Analog Trainer A complete fninMtb for building, lesilngt prototyping analog and digital drcuiia Elflnco's DiBital.'AniJ<>g TraiJief Ls ^jecia^fy designed tut schooE pfajscis. 5 built-in powdt iuppCiM. incluttes a fgrtction geflefator with ctjnttntjysly variafc^, &ine, liiangulaJ, square wave fornix. ASl powar supples ragulatsd aiid prcifi:-,ed shorts, Rowtr Supplies E>t 2Sto 15VDC# 1 AiTip} ■ -i ^ti ^OVDC^ SAirp E l2Sto -l5VDC9 1 An^} ■ *1Zyl>C«1 Amp ■ IZVDC^tAinp ■ «5VDC#1Anp ■ C«f««f UppM ^ « 1 Airp Analog - Section ■ FriquBicy ad|,u3itiibli} infftft far\Qtit irom i to 1 IJOKHj ■ Amoiliuda ad]iiii « DCoftitl Digital ' Se^on ■ T«g no tnunct looe tH«cA«t m « LED rMdaiti m. biM««d Bretdtioardt ci^t^ MO M poMiMMmeoi AsSemOEeQ 5129.95 Kit WE WILL NOT BE UNDERSOLO UPS SHIPPING: 4a STATES ILflES7.5«fl TAX (S3 mm Stomal) PROBES INCL AU SCOPES & METERS C&S SALES INC. 1245 ROSEWOOD, DEERFIELD, IL 60015 FAX. 708-520^0085 • (708) 541-0710 15 DAY IVIOI^EY BACK GUARANTEE FUU FACTORY WARRANTY WRITE FOR FREE CATALOG 15 CIRCLE \0S ON FREE tNFORMATLON CARD LETTERS Write to Letters, Electronics Now, 500-8 Bi-County Blvd. Farmingdale, NY 11735 AUDIO BUYING TIPS I have enjoyed Larry Klein's Audio Update column very much over the years. He provides a breath of fresh air in a field often fogged by the strung odor of addled logic, Larry s coverage of the 1991 AES Conven- tion was also enlighteninging be- cause he drew attention to the significant psychophysical research concerning what we really can or cannot hear I'd like to add a few buying tips for consumers from my article "Can You Trust Your Ears?" AES PrBphnI 3t 77. Because humans have such a strong tendency to hear sounds that might never have occurred, au- dio equipment customers should be aware that even the best receivers, preamplifiers, CD players and am- plifiers cannot be reliably evaluated under controlled conditions. CI am assuming that this equipment is being operated at its specified power limit and all cabling meets the manufacturers' requirements.) Second, it is practically impossi- ble to conduct a fair listening evalua- tion even in a studio-equipped retail store with all components matched and compensated. Finally you are not stupid if you don't understand everything the salesman tells you. When you are tempted to buy a product but still unsure of yourself, wait until the next day to make a decision. There s a good chance that youll decide you don't need whatever it was that was being pitched. Caveaf emptor I TOM NOUSAINE Ca/y IL I NETWORKING CORRECTION S As a long-time reader of Radio- § Electronics and a data-communi- ^ cations professional. 1 was pleased I to read the first part of Gary Mc- B Clellans series entitled "From Not j| Working to Networking/'in your Au- gust issue. Unfortunately the sec- fg tion entitled '^Connecting net- works" positions bridges, routers, and repeaters in the incorrect layers of the ISO/OSI model It is generally accepted in LAN networking that a repeater operates at layer one. a bridge operates at layer two. and a router operates at layer three of the ISO/OSI model I trust that statement clarifies Mr. McCleilans information, and I look forward to reading the remainder of the articles in his series, SHELDON H. DEAN. GET Calgary. Alberta, Canada THE BOTTOM LINE As panelists in a seminar entitled "Strategies to Guard Against Pro- ductivity Loss ' during PC Expo on June 25. we were astonished to find that of the thousands of industry professionals at the show, only one decided that a session on productiv- ity enhancement was important enough to attend. The shows management found the topic compelling enough to sponsor the seminar, and experts on the subject were ready to talk. But it seems that the indtviduats in the industiy — vendors, customers, and managers of corporate comput- ing resources — did not find it impor- tant enough to learn more about the link between technology and pro- ductivity. Members of the industry do seem to find glitz, power, and speed interesting. They seem to fixate on the question: "Can we make it big- ger faster, or better than our com- petitors?" The name of the game seems to be "hardware for the sake of hardwafe" and "software for the sake of software/' We forget that senior manage- ment, which controls the purse strings, cares about return on in- vestment, productivity and profit. They don^t care about chip speed or power. Who in our industry is think- ing about vita! productivity issues such as education, training, and support? Is anyone thinking about the need to re-engineer products to take advantage of developing tech- nology? Is management afraid to find out if there really is a positive return on investment in computer technology? Until the computer industry stops to takes stock of where it has been and where it is going — particularly the relationship between computer technology and the bottom line — the pnDmise of technology will not happen. We should be concerned with how the technology can change the workplace, improve cor- porate competitiveness, and help us to meet our national economic goals. None of this is glamorous stuff. Making technology deliver on its promise is tough, tedious work. It certainly does not offer the fun of playing with the latest and greatest graphics user interface. But it is where to find productivity in- creases. Productivity is the respon- sibility of people, not just machines. It seems that those attending PC Expo were looking for something other than strategies to prevent losses in productivity. KAREN KARTEN Karten Associates PETER DE JAGER de Jager S Co. DAVE WHITTLE IBM SUSAN RASKIN Rastec RALPH E. GANGER Sterling Resources I'd like to respond to the letter by Stephen Schleick, "Seeing the Light. "(June Radio*Elec- ironies.) In my opinion, as a tech- nically trained person Mr Schleik should have been better able to un- derstand the point made by his "Vocket scientist " friend. Mr Schleik's anger at his friend is un- warranted, but he is correct in what he said about the average power usage of a light bulb. However Mr Schleik missed by a mile the point being made by his friend. The problem is not average power consumed by the bulb, but the power surges that damage the bulb and cause its premature failure — the reason why we are al- ways purchasing new bulbs. The three reasons for filament lamp farlure are operating time, fre- quency of turn-on, and supply volt- age. A standard commercial bulb can be expected to fail after It has operated at its rated voltage for about 750 hours. CThis is an average life for household incandescent bulbsX The lamp manufacturer is in business to sell lamps at a profit. If bulbs last ten years, repiacement sales will be low, The more ffBquentfy the bulb is turned on and off. the shorter its life. The 750 hour-itfe is an average de- termined from specified test pro- cedures. Consumers usually don't get tfiat kind of life from lamps for the same reason they don't get the gas mifeage shown on new car stickers. People don*t use light bulbs or cars the same way they are tested! When I lived in art apartment in New York City. I never turned off certain tights because the electric bill was included rn my rent. I just turned down the light, with a dim- mer. The pent is, I never replaced light bulbs in the eight years I fived there. When I bought a house and had to pay the electric bilL I turned off all my lights at night, I had to replace my eight-year-old bulbs in a few days. Coincidence? Maybe, but I don't think so. In my own house we had to replace bulbs every few months. We operated the bulbs at full brightness only in the evenings and on weekends. Which is cheaper a $1,00 bulb that lasts eight years with a dimmer CIO cents a year without being turned off) or replacing bulbs cost- ing a buck two to three times a year? I measured the idle cunrent of a lamp with a dimmer having a 4.3* ohm resistor in series. The voltage across the lamp was 8 millivolts. With Ohms Law, 0.008/4.3 = 0,00186 amperes or 1.86 milliam- peres, I multiplied 120 volts x 1.86 milliamperes to get 223 milliwatts Cfn^m the line). Then 223 milliwatts X 8760 hours/year equals 1953 watt'hours. This is a 1.953 kWh power consumption with a dimmer For practical purposes 1.953 equals 2 kWh at 5 cents (average U S, power cost) per kWh for a cost of 10 cents, CIn New York City with power costing three times the U.S. average, the result is 30 cents.) I ignored the time the bulb was at full brightness because I assumed that time and cost would be the same in both cases. And I haven't included the tost time and trouble of buying new bulbs and spares. Based on the standard of 120 vdHs rms in the U.S., a good rule of thumb is that a 10% voltage in* crBase shortens bulb life by half, but a 10% decrease doubles bulb life. Are there ways to get around this? First, don't buy standard long- life or guaranteed bulbs ; all you get is one designed for 130 volts, usu- ally poorly made. Consider traffic-light bulbs. They are made for long life and reliability. The tungsten filament must be longer and thicker to obtain the same level of illumination but have a longer life. That makes the bulb more expensive to manufacture. Higher price means fewer will be sold which, in turn, forces up the retail price even further. Most peo- ple buy the cheapest bulbs th^ can find because they don't remember how long its predecessor lasted! PAUL CHRISTIE Bayside. NY DISTORTION STOPPER The distortion problem presented under the heading "Pocket-SterBO Amp*" in Ask R-E CRadio-Eiec- tronics, August 1992) might not be caused by the LM386 circuit: it coufd be caused by insufficient load on the source amplifier from the pocket stereo — particularly if the output amplifier is made from dis- Crete components. The key to my conclusion was the report of distor tion at all listening levels. I recommend loading the pocket stereo with a 20- to 50-ohm resistor as shown in Fig. 1, JIM HATHAWAY II North Highlands. CA VIDEO COPYGUARD ^^iS Stabilizer Mini jwJ flwhiiii, Snnple Pro ED/it 3 Video Processing Center •Cotopf«tt50f (nodd <4^AQC P»^a no • Sleieo sound mi»n j^q.^ ^ |t|5l*'^. 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Plus you leam to use your QuickTech diagnostic software to test the system RAM and such peripheral adapters as paralleS IBM is a re^flierfid, trademark of Intemiilianal Businesa MBehintfl Corp. H.A.C.E.R, and QuickTt^ch are rrii^ij^terLH] iraxItmarkH urUltrji-X. Inc. SEND TODAT FOR FREE CATALOG McGraw-Hill Continuing Eduication Center ^ 4401 Comi&cticut Avenue, NW WiJM Schools Washington. DC 20008 ff^ii Check one FItEE catoJo^ only n MICROCOMPUTER SERVICINC li rvVidWAudio Servicing □ Telecommunications □ Indui^trial Electronics D Security Electronics □ Electronic Music Technology □ Baaic Electronics □ Automotive Seni'icing For ciinrer courses appn?vect uniier GI Bill Q check Tor d«;t4]ils. D Computef Proframmin^ D Programming m C++ with Windows □ Desktop Publishing n Word Proces^iing Imma Business □ Home Inspection □ Building Construction n Bookkeeping & Accounting 1 Name 1 {please print) Age j Address 1 Citj^/State/Zip Accredited Member Kational Home Study Coundl 3-112 EQUIPMENT REPORTS JPC International TD107 Digital Designer Breadboarding circuits is the only way to learn electronics design! CmCLE 10 ON FB£E H^FORMATION CARD 'Ui^ ill From the mail that ^ve receive at Electronics Now, we know that many of our readers en- joy our concentration — in both fea- ture articles and columns— on circuit theory and design. In this is- sue, for example, we present al- most two dozen circuits based on the 555 timer in a feature article^ and a simple video scrambler circuit in our "Drawing Board" column. And, of course, our construction projects provide new circuits every issue. Although it s possible to learn a great deal by studying the circuits and their accompanying descrip- tions, its not the best way. There's just no better way to mcrease your understanding of electronics than "getting your hands dirty" building circuits and experimenting with them. Having an adequately equipped lab is essential to electranics ex- pehmenting. The right equipment lets you build circuits more easily and efficiently. That s important be- cause the easier it is to build cir- cuits, the more you will experimenl. and. thus, the more you will leam. Such thoughts kept cnDSSing our minds as we examined the TDIOJ Digital Designer from JPC interna- tional (P.O. Box 55, Agoura Hills, CA 91301). The TDiO? makes it easy to build circuits and change The RMS225 was built around sim- plicity. Instead of a barrage of buttons to push, you simply scroll through a menu of special functions- Minimums, maximums and automatic read- ing hold arc simple functions i-vith Bcckman Industrial's RM5225. It's simply the best meter for the money. Bl 22 CtnCLE 17« ON FUEE INFORMATION CARD /SUPER 12 HOUR RECORDED CALL TOLL FREE Modified Panasonic Slimline J 6hr$ per side 120 TDK tape fumished. AC/DC Operalion. Quality Playback. Digital Counter. Durable Lightweight Plastic. ^ $119.00 PHONE RECORDING ADAPTER Starts & Stops Recorder Automaljcaliy When Hand Sei is Used, Sorid State! FCC Approve VOX VOJCE ACTIVATED CONTROL Solid slate Adjustabte SensiUvit/. Voices Bi Sounds Activate Recorder Adjustable Sensitivity Provisions for Refnote Mike $28.50' $28,50' * Add for ship A handlir>g Phono Adaptor S Vox S2.00 each, Rocordors S5.00 G&ct\. Colo. Be% add lax. Mail Order, VISA, M/C. COlTs OK. Money Back Guar. Qly E>tsc. available. Daater ifiquirias inviled, Ffeo data on other prtwJucts. AMG SALES INC. 193 Vaquero Dr. Boulder, CO. 80303 Phones (303) 499-5405 1-800-926-2488 FAX (303) 494wi924 . Mon-Frl MTN. TIME ^ emcLE loe on free information caao their configurations, and examine how they operate. The designer, which is housed in 3 sturdy cneam- cotonsd plaslic case that measures about 10%x8%x2 inches, fea- turns a large soldeHess breadboard on its front panel. The breadboard provides a total of 1380 tie points, which can accommodate up to six- teen 14-pin DIP'S. Because the TDtO? offers burlt-in power sup- plies, pulse generators, clock gen- erators, and more, it's possible to build circuits that are quite complex. Eight LED logic indicators are lo- cated at the top left side of the de- signer s sloping front panel. A logic probe, which indicates high, low. and pulsing logic levels is also avail- able. Two momentary logic switch- es let you manually generate pulses. Pulses of 0.5 Hz and 500 Hz can be obtained from front panel temninals in either high- to- low or low- to-high transitions. Clock signals are also prwided by the designer Complementary clock signals with frequencies of 1 Hz, 1 kHz and 100 kHz can be switch-selected. A line frequency (60 Hz) clock is also available. Eight slide switches provide switchable high or low data lines that can serve as inputs. Two potentiometers. IK and lOOK units, are conveniently lo* cated at the bottom of the panel. Among other things, they can be used to adjust the levels of the + 5 and ± 12 volt power supplies. Having such building blocks as power supplies, pulse generators, and clock generators around the breadboard means that you can concentrate on accomplishing a task without worrying about basic, mundane circuitry. That makes the TD107 designer ideal for formal lab- oratory courses because it lets stu- dents use their class time more efficientty. The designer v^ould also be appropriate for home use by any electronics hobbyist or enthusiast. For those users who need to build large circuits, the designer can be expanded with additional bread- board space that can hold up to eight additional 14'pin DIP's. The TDf07 digital designer car- ries a suggested retail price of $159.95. which is competitive for this type of device. JPG also offers an analog designer, the TA102. which is priced at $149.95. The ana- log designer provides the user with variable regulated power supplies, a center-tapped 30-volt AC supply sine-, square-, and triangle-wave generators instead of the digital pulse and clock generators, and logic indicators. R-E Be an FCC LICENSED ELECTRONIC TECHNICIAN! No cosily school. No commuting to class. The Original Hoine-Study course prepares you for the "FCC Commercial Rfidio- teleptione License** This \'aluablc license is your professional "ticket" lo thousands of excitinji jobs in Communications. Radio- TV. Microwave. Maritime Radar. Avionics and morc»..even start your own business! You don't need a collejje degree to qualify, but you do need an FCC License, No Need to Quit Your Job or Go To School This proven course is easy, fast and lorn- cosil GUARANTEED PASS— You gel your FCC Li cease or monej* refunded. Send tor FREE ficls now. MAIL COUPON TODAYI communD productiohs FCC LICENSE TRAINING. Depl. 3Q P.O. &OK 2B24. San Frantisco, CA 94126 Pleue ruih FREE deUils Immedlaiety! NAME , CtTt SWT! . I I I I I I I .J TRUTH If your meter doesn't liave Tnic RiVlS, it's Kdng to you- Those nast)^ nonsinusoidal ami iiois)^ siniiscikLil n'mr forms ftx>l even the hcst "averaging meters. The pn)hleiii was, TKie RMS used to be expensive, Gotid news The RiVl5225 is I Kill' the price of similar meters. Call (800)854-2708, (8ai) 227-^781 in CA. I m S 3 23 CIRCLE 17G ON FREE INFORMATION CARD NEW PRODUCTS Use the Free Information Card for more details on these products. Si I E S I E I UJ 24 AM BROADCAST LOOP AN- TENNA. The BCLl receiv- ing antenna fmm Electmn Processing, a compact 8 X 8- inch square un- shielded loop, is said to re- ceive AM broadcast sta- tions while rejecting exces- sive noise. A 30-dB pre- anriplifrer assures strong signals, and interference is reduced or eliminated by the loop's directional characteristics. Noise re- duction permits the recep- tion of stations that other- wise could not be recetved. With a reception range of 530 to 2000 kHz. the an- tenna IS powered by tine t20-volt AC. It rs equipped with a jumper cable to con- nect the receiver and a se- lection of connectors Is available. The price of the BCL-f AM loop antenna is $125 handling.— Electron Pro- plus $5 for shipping and cessing, Inc.. RO. Box 68 CIRCLE 16 ON FREE INFORMATION CARD Cedar. Ml 4962 T; Phone: 616'228'7020. DATA-ACQUISITION CARD, Gage's CompuScope L/rE*64K data-acquisition card provides 40'MHz sampling with 64K of mem- ory. According to the com- pany, its card permits personal computers to match the performance of stand-alone digital os- cilfoscopes. The card, in an IBM PC/ XT/AT format, performs 40-msps digitization on one channel or simulta- neous 20-msps digitization on two channels. It also of- fers 8-bit resolution, 32 kilobytes of memory per channel, external trigger capability, software drivers. CIRCLE 17 ON FREE INFORMATION CARD and a user- friendly inter- face. Up to eight of the cards can be installed in the same PC making it equivalent to an eight- channel. 40-MH2 or 3 16- channel. 20-MHz digital os- cilloscope. The CompuScope LITE card purchase includes dig- ital-oscrlloscope software permitting users to store, anal>^e, print, and transmit their data. GageCalc soft- ware also permits users to carry out math functions such as FFT and frequency counting. Gage offers soft- ware drivers compatible with all popular compliers: Turbo Fiscal, Turbo C* Mi- crosoft C. and Turbo Basic. Those drivers can contnDl the board in OEM appfica- tions. The software* which runs under MS-DOS. has an installation utility and an AutoDetect feature that is said to be simple to use. CompuScope UTE-64K costs $995 —Gage Ap- plied Sciances Inc.. 5465 Vanden Abeele. Montreal, Quebec. Canada H4S iSt; Phone: 514 337-6893; Fax: 514-337-8411. PUISE GENERATOR. Pro* teks Model 31 0101 Hz to 10 MHz pulse generator in- cludes includes variable delay and seven pulse wid* ths. 0 to 5 volts into 50 ohms. Delay time ts 0 to 50 and 500 nanoseconds. 5. 50 and 500 microseconds and 5 milliseconds, varia- ble in each step. CIRCLE 18 ON FREE I^R^RMATjON CARD Seven pulse widths range from 50 nanose- conds to 50 microseconds with each step variable. Four operational modes are offeied: internal exter- naL manual, and external up and down. The pulse generator measures lOVs X 9 X 3% inches and weighs 5V^4 pounds. The B-WfO pulse gener- ator price is $499.— HC Protek. RO. Box 59, Nor- wood , NJ 07648: Phone: 201-767^7242: Fax: 201-767-7343, PORTABLE PROTOTYPING STATION. How about a por- table electronics laborato- ry to lake to school the job—or even on vacation? ^ Every Cleaning Task Made Easier with New Brushes, Swabs & Wipes CIRCLE 19 ON FREE INFORMATION CARD Global S pecia It ies* PB'503 C is a complete electronics prototyping station housed in a carrying case, \i can be used for pn3- totyping analog, digital, and microprocessor circuits and performing many kinds of experiments. The breadboard has an area large enough to hold circuits with as many as 24 DIP^ packaged devices. The portable lab contains a function generator, a power supply with three output voltages, an S-channel log- ic probe, and two digital pulsers. The power supply has a + 5- volt, t ampere, and two vanable S-IS-volt, 0.5-am- pere terminals. The func- tion generator produces frequencies from 0.1 Hz lo 100 kHz with a choice of sine, square, and triangular waveforms or TTL clock output. The briefcase- sized, fold-down carrying case is roomy enough to store an optional Proto- Meter 4000 multimeter and WK-1 wire-jumper kit. The PB 503'C portable prototyping station is priced at $349.95: the ProtO'MBter 4000 price is $139 95. and the WK-1 wire-jumper kit price is $13.95.— Global Spe- cialties, 70 Fulton Terrace. New Haven. CT 05412; Phone: 800-572-1028. 4B6-CLASS SINGLE-BOARD COMPUTER. This PC-com- patible, single-board com- puter from Computer Dy- namics is intended for embedded OEM applica- tions, !t includes an Intel 486^compatible MPU. flash memory, and an ad- vanced video controller The board measures 5-3/5x7-3/4 inches, tak- ing up only about 10% of the space required by a desktop PC. The board's 25'MHz Cx486SLC MPU executes the 486SX in- struction set and all 486SX operating systems, includ- ing DOS and Windows. An on-chip, one-kilobyte cache gives the processor more than twice the speed of a 386SX at the same clock frequency- In addition to the Full complement of standard PC functions, the board provides for up to 786 K of flash ROM. CIRCLE 20 ON fREE INFORMATION CARD For fixed*program stor- age, the SB0486 has up to 1.5 megabytes of on- board ROM/RAM disk, en- suring quick boot-up and reliable operation, The on- board video controller driv- es CRT s and flat*panel dis- plays directly. Other fea- tures include hard- and floppy-disk controllers, a battery-backed real-time clock, a math co*processor socket, and an SBX inter- face that lets the user add "non-IBM" expansion boards. The SBC- 486 board is priced from $936 in OEM quantities.— Computer Dy- namics, 107 South Main Street, Gneer, SC 29650: Phone: 803-877-8700: Fax: 803 879 2030. V/helhef ymi're Ucklmg the iMest |ob, or deamnq a prediicn piece equipment Tecti Sprnsy fm a cJeanirig produa that makes the task easief . Tech Spray has expanded iu line bfushes, swabs and wipes to cover the wide variety of cleaning and maintenance needs in the electjonic industiy. All Tech8rushes'*\ Techswabs'** and Techclean^" Wipes are precisely manufacturefi under Tech Spray's rigid specifications* Tech Spray lakes special care throughout the manufacluring process and in its packaging to maitimize cleanliness and protection against eJectfostatic discharge. For a sample d these, or any Tech Spray product, contact our Technical Assistance Department toll free at 1 -800-858-4043 A saa^)^ 0/ recf»emsftes^. Techswahs ^ and Techckmn^*' Wipes TECH SPRAY, \nQ. P.O. Box 949 Ajtiarlllo. TX 79105-0949 (306) 372^8523 CIRCLE 117 ON FHEE INFORMATION CARD AN ECONOMICAL KEYBOARD-CONTROLLED KEPCO BENCH POWER SUPPLY 75 WATTS Choose from four DtgiJal Rower Supplies: 0-1 2.5V BA, 0-a4V ((t 3A, 0-40V m 2A or 0-1 25V 0.5A. Each one offers precise, repeatable voltage control with !wo current rariges. Fully protected for overvoltage or overcurrent. Bonus: You can program the oulpul from your PC s serial port d. so it wont suiprise us if you pick up a whole case. After alL some folks were just bom to have the blues, Duraprobe Brownell / Carolton-Bales / CMI-Metermaster / Contact East / ENTEST / INOTEK rrc / Jensen Tools, Inc* / Joseph Etectronics / Marshall Industries Radar Electric / Electronics / 2ack Electronics anCL£ 1 7i ON mEt WFOfUlAHON CARD Use The Free Information Card for fast response. ANALOG DIALOGUE; from Analog Devices, Literature Center, 70 Shawmut Road, Canton, MA 02Q21; Fax: 617-8^-4273; Iree, Analog Dialogue is Ana- log Device s house organ for the dissemination of in- formation about its prod- ucts and related tech- nology. The company terms it "a forum for the exchange of circuits, sys- terns. and software for real- worid signal processing/' ORCLE 25 ON FREE INFORMATION CARD This edition (Volume 26. Number 1 00) features high- light the subject of mixed- signal chips for driving digi- tal radio. It discusses a pair of monolithic I/O chips that provide critical functions for digital mobile-radio communications. The AD7001 and AD7002 are described in a tutorial titled "!F Stages Are Going Dig- ital for Both Analog and Digital Signals." The journal also carries an article on monolithic Sig- ma- delta converters with 21 -bit resolution backed up by a tutorial on sigma-delta architectures. Another arti- cle covers a SPICE macro- model of an analog multi- piier. Other sections in- clude a new product over- view, an advice column on voltage references, and a review of new literature from Analog Devices. MINIATURE SWITCH CATA- LOG; from Eaton Corpora- tion, Aerospace & Commer* cial Controls Division. 4201 North 27th Street, Mil- waukee, Wl 43216; Phone: 414^449-7483; free. CIRCLL lU (JN FREE INFORMATION CARD This catalog Cpublicatron number NC-169) contains a technical specification in* formation and illustrations on Eaton s line of miniature switches for electocal and electnsnic applications. To simplify the search for the switch that will meet your requirement, each product section includes a brief product description and a selection table, DESKTOP PUBLtSHING WITH WORD FOR WIN- DOWS VERSION 2.D; by To m Lichty. Ventana Press, RO. Box 2458. Chapel Hill, NC 27515; Phone: 929-942-0220; Fax: 919-942-1440; SS21.95, The software Word for Windows, version 2.0 is in- tended for word process- ing and desktop publishing. Tills book offers advice and examples to help users take full advantage of that software. Mr. Lichty*s book, which assumes that readers have a working knowledge of Word, ex- plains how to create attrac^ tive, well-designed docu- nnents on a computer. CmCLE 27 ON FREE INFOR^UTION CARD It addresses framing and text placement in desktop- publishing. Also covered are the fundamental princi- ples of page design such as proportion, balance, and unity. The book tells the reader how to apply those principles to setting mar- gins, white space, ailes, and borders. Other topics include typography, style sheets, multiple columns, and graphics placements. The final chapter contains specifications for recom- mended printers and print- ing methods. KNOB CATALOG; from Rogan Corporation, 3455 Wood* head Drive, Northbrook. IL 60 062; Phone: 800-423'1543; free. You'll be amazed at the variety of sizes, shapes, colors and styles in which a simple product like a knob can be produced, Rogan s catalog proves that push- buttons have yet to usurp the role of rotating contmis in electronics. The right se- lection of knob can make or break the appearance of your product. CIRCLE 28 ON FREE [NFORAUTION CARD This catalog illustrates Rogan "s broad range of products, spelling out its options in material, size, style* markings, color dec- orative options, mountings and dimensions. There are, for example, ergonomic clamping knobs, digital turnS'Counting knobs, in- strument knobs, and mili- tary spec knobs- TECHNI'TOOL CATALOG 42; from Techni-Tool, 5 Apollo Road, P.O. Box 368, Plymouth Meeting, PA 19 4 6 2; Phone: 215-94V2400; free. CIRCLE 29 ON FREE INFORMATION CARD Techni-Tool's 1992 cata- log gtves information on the company's tools, tool kits, test equipment, and supplies for factory pro* duction and professional trouble-shooting as well as field service on ail kinds of electrical and electronic equipment. 1992 CATALOG: from MCM EEectronics. 650 Congress Park Drive, Centerville, OH 45459-4072; Phone: 1-800-543-4330; free. MCM's latest catalog contains specifications in- formation on more than 17.000 electronics parts and components. This 212- page edition includes refer- ence to 1500 more items than the 1991 edition. Prod- uct categories include semiconductors, television and VCR parts, power sup- plies and regulators, tele- C1RCL£ 30 ON FRff INFORMATION QUID phone components and accessories, batteries, speakers, and tools, YOUR VHF COMPANION; ed- ited by Steve Ford, WBSIMY. Tfie American Radio Relay League, 225 Main Street, Newington, CT 06111; $8.00. Your i -VHP, - CmaE31 ON FRfE INFOItMATiON CARD This book will be wel- comed by veteran VHF op- erators as well as novices because it contains plenty of usehji infomnation in an entertaining, easy- to-read format. For example you'll find out how to participate in all the activities on the VHF bands— FM and re- peaters, packet radio. CW and SSB. satellites, and amateur television, UNOERSTANDING HAR- MONICS IN POWER DISTRi- BUTION SYSTEMS; from John Fluke Mfg. Co., Inc., Service Equipment Group, RO. Bojt 9090, M/S 250-E, Everett. WA 98206-9090; Pfione: 800-526-4731; Power line harmonics can be a source of un- wanted interference in fac- tories and offices that depend on the reliability of line-powered electronic equipment from PC s to copying machines- Har- monics can cause transfor- mers and neutral conduc- tors to overheat and circuit CERClf n ON FREE INFORMATION CARD breakers to trip for no ap- parent reason. This 17-minute educa- tional video will help you to understand and solve har- monics problems. It covers such subjects as the defini- tion and classification of harmonics, electrical loads, equivalent circuits, and the detection of har- monics. It suggests meth- ods for solving harmonics problems in new and exist- ing buildings. R-i Train at HOME to be an Electmnics Technician \ M ^ demard for tcjmpyters and mKropcDtTOOfS in bu^ine^^, mjntHactunng dftd comfnunitatiom ccMiTinue^^ ro grow, so does the nesd tor qtuUned technicians. \t's noi unmujA for enpenenced rechnfcians to earn from S10,0OD ta murv th^n S40.000 a yL*ar.* Now ihrough P^pli?s Collect* of independeni Studies you can train tor thi> eJtciting field without interrupting your job or home life. • Electronic* A MicfoprocesiOf Technofogv^ • Industital Electronics & Mtcrapioces^ Technology • Com muntcat ions Electrortic^ with MEcflV pnxe^wf Technology • Computer Servicing Sr Electronics Technology • Specialized Avsociate Degree In Electronics Technology Profmioru] Eqyrpment Is frKrluded Depeoding on I he program you ^lea, you'll perfeci your Mh using thb advanced equipment, included in the price o^ tuition: • JBM-Comp*iiible Personal Computer • Digital Mglrirnptef • Digital Logk Probe • Elenco Oscilfoicope • Portable Cellular Tel^hone Peoplev t oik'gt' lotrtxJiH M^nu' (raining firsts to makie your learning eitpeiience mon? comp!ele: • Accelerated Learning System — a scientifically pfoven study system that helps yon learn fastef and easier than ever before, • Video Tutor Training Tape* — give you a permanent, visual record of inforniative lectures and close-up demonslration*, • E!i|)erience Labs — professionally designed experiments that give you hands-on "Ixinch" experience. • Indusiry Ceriific^tior^ Training Guide — provided with four of our programs PrefMres yuu tot examiii.itions you may take for your prdevsional licenve of certification. To help yoo fjei ^fted on your eduiat»on. PieopSes College has reduced tuition raie^ and offers low monthly payment planii with no finar>ce fees. So tlnn't delay, caW or write for mofe informalion todiiy! Fof COLOR CATAtOC Mall Coupon Qill TOLL FREE 1-800-765-7247 i'nifitjn:, itr?tTrtJ unit f-'* i ncfx^j '■Ijfri. ( U'm^Li f'i/V-fTle faBt from o jr speoal-order warehouse. Orderiag is ©asyf Bring in the exaci part number (or an i/iW 271 m too z.m Carton 'Film ViW SOO 7,95 271 306 too 3 49 Mini AudJo Amp With a Built-in Speaker. Many uses! Tough 3%'- hrgh case Low Radio Shacit price, »277-1008 _ , 11.95 ( 1 ) Magnet Wire Asso rt m ent . For custom coil wending. Includes 40 feet of 22-gaugeH 75 feet of 26- gauge and 200 feel of 30-gauge on spools. #273-1345 4,99 {2} Dial Cord FU*lt Kit. Our exclu- sive! Includes siK feet of high- slrength cord and three tension springs. Put a radio back ifito aciioni #274-435 99* High-Speed 12VDC Mini-MotOf. Produces an amazing IS, 200 RPM at no toad. Ideal for pfojects. ro* botics. lunt About Z' \onq (with shall), #273-255 2.99 PC/XT Circuit Cord. Epoxy. Fits computer expansion bus. 10 'Ae' iong *276*l59e 29.9S night Angle 0*Sub 25 Female Con- nector tor 4bav*. ^276.1502 . 2,G§ Infrafed Project Box. Ideal for a rernote. Has removable infrared- trarvsparem ertd panel and Space for 9V battery. ^kKZ^xA'^h'. #270-204 4.49 100'Wen soldering Gun, For b:g jobs! Reaches full temperature in seconds. Built-in work light. Re- placement tips in stock. liL fisted. #64-?l93 11.95 Prices apply at panidpating stores and deafef^. MMEmCM'S TECHmLOCV STORE SMCm fB2f A DfViSK>N OF TANDY COflPOflAnaN aRCL£ 7B QN FREl IMFQRMATIOK CAflO BUILD THIS SUPER STROB Create breathtaking stop-action photos with the Freeze Frame. so MUCH OF LIFE IS A BLVU. WHEN you can slow i t down and savor I it. you discover the most inter-i testing things. I r Take, for example, the pie- 1 tures showing a Wcitcr- filled bal-' loon being popped by a dart . You might anticipate that the burst balloon would leave a ball of water hanging in the air for a fraction of a second, but would i you have guessed that the sur- face of the water ball would fipth the way It does? What a beaiiti* ful surprise. Our Freexe Frame strobe trig- ger lets you use photographic techniques that subslitule a strobe flash for high shutter speeds. You can reproduce these and other stop-acHon shots ei tiler for serious scien- tific purposes or jusL because they make such interesting pie- Lures. The inexpensive, easily built unit has been t!<*signed to use interehangeablt' ^^ensors. so that anyihing that pops, snaps* flashes* or reflects or blocks Itght can trigger your camera's strobe. How it works The complete schematic for the Freeze Frame Is shown in Fig, L Either of the sensors [phototransistor Q2 or electrel microphone MlCIl acts like a variable current sink in series with RL As light or sound levels change and more or less current sinks into the senson a voltage develops across Rl. The processing amplifier for the sensors is built around two stages of an LM324 quad opera- tional amplifier (ICl-a and ICl- b). The amplifier is AC-coupIed JOHN SIMONTON and TREY SIMONTON f t n so that only changes in the h^ig- gering signal arc detected. The values of the coupling capacitor between stages are inten- tionally small so that only changes with higher- frequency components (above about 5 kHz] pass through the ampli- lier When using the micro- plione. that means that snaps and poi>s will l>e more likely to trigger the unit than other am- bient noise* including speech. Capacitor C2 couples the out- put of the processing amplifier to the rectifier- and peak-detec- tor section consisting of Dl* D5* R9, RIO, and C4. The DC volt* age that appears across R9 is approximately the same as the peak-tO'pcak voltage at the out- put of the ampimcn The voltage is applied to a threshold detector, which is a m a' z 3t Jl INPUT C9 R6 R7 lOK V4 imii RB ^ .02 .1 MtCl SOUMD SEMSOR FIG. 1— SCHEMATIC FOR THE FREEZE FRAME. The sensors act like a varJabJe current sink in series with R1. As light or sound levels change and more or Jess current sinks ffito the sensor a voltage diivelops across Rl. — RT5^ —a- a R17 IfOT FIG. 2— PARTS- PLACEMENT DIAGRAM* The three wire jumpers can be formed trom excess component lead. SchmiU trigger built around ICl-d. The trigger level Is set to a couple of volts and hysteresis is set to about one volt by R16. R18. and R20. At the output of the amplifier, LED I Indicates when a stitnulus has exceeded the threshold. When the output of the threshold detector goes low, C6 couples the transition to the in- put of the 555-based timer sec- tton and triggers it. The amount of delay produced by the timer is set by the delay con- trol R!2 and capacitor C7. Ca- pacitor CIO Is switched in by S2 when longer delays are needed. The output of the timer is coupled by C5 to the final ampli- FREEZE FRAME foil pattern. fier stage in ICl* which is wired as a comparaton At the end of the time-out* IC2s output goes low and is inverted by ICl-c to a positive transition that turns on SCRL The current path to SCRTs gate is provided by LED2» which also indicates that the triggering signal has hap- pened. As a convenience when setting up to take photos, switch S3 can be closed to ground the gate of SCRl and prevent it fram firing. Building the Freeze Frame You can build the Freeze Frame with just about any con- struction technique you like. A circuit board is always the neat- est, quickest, and easiest way though, so we Ve provided a foil pattern- You can buy an etched and drilled board from the source given in the Parts List, If you use a PC board, mount and solder all of the components fol* lowing the parts-placement di- agram in Fig, 2. Tliere are three PARTS LIST All resistors are V4-watt, 5%. Rl, Rte— 1000 ohms R2— 5600 ohms R3, R4. R6. R7, R10, Rt5. 10,000 ohms 680,000 ohms RB— 50.000 ohmSp audio-laper po- tentiometer with switch (81) R9— 330.000 ohms R1 1—100.000 ohms R1 2— 250,000 ohms, linear-taper potentio meter R13— 680 ohms R14— 1 megohm R17. R25^2200 ohms R20— 15 megohms R21— 470 ohms R22— 330 ohms R23— 33.000 ohms R24 — 1500 ohms Capacitors Cl. C9— 0.005 |aF. ceramic disk C2. C5— 0,1 M^R MyJar C3— 2.2 ^F, 10 volts, electrolytic C4, C6. CS — 0.01 \Lf, ceramic disk C7 — 0.05 jiR ceramic disk CIO — 1 fiR 10 volts, electrolylic Semiconductors IC1— LIV1324 quad op-amp IC2— 555 timer D1-D3— 1N4148 diode LED1-LED3— red light-emitting di- ode 01 — IR phototransistor SCR1— T106D siiicon*€ontrolled rectifier Other components B1— 9-volt battery Jl — ^Miniature phone jack J2— RCA jack MICI— Electrel microphone PL1, PL2— Miniature phone plugs S1— SPST switch (part of R8) S2. S3— SPST slide switches Miscellaneous: case with top pan- el, knot>s, wire, tiardware, battery snap, hea!*shrink tubing, coaxial cable, circuit board, etc. Note: The following items are available from PAIA Elec> tronics, Inc.. 3200 Teakwood Lane, Edmond, OK 73013 (405) 340-6300: • Etched, drilled, and sHkscreened PC board (#9208pc)— $12.75 • Complete Freeze Frame kit including PC board, case, and all components (#9208k)— S39,75 Please add S3.50 shipping and handling to each order. Fta 3— MAKE THE SENSOR ASSEMBLIES with heat-shrink tubing and small diame- ter coaxial cable such as RG-174/U. The space between the coaxial cable and the outer heat-shrink tubing is filled with a little silicone rubber. FIG. S^A DART HfrTING a water-filled balloon from an angle. The microphone sensor picked up the sound of the bat^ loon bursting. FIG. 4--THE COMPLETED FREEZE FRAME. This is one of the most attrac- tive boards you'll ever see. wire jumpers on the board that can l>c formed from the excess leads clipped from other compo- nents. A fairly light gauge wire such as AWG 26 is appropriate for making connections between tlie circuit board and front-pan- el controls. With any electronic circuit, keeping Ihe wiring be- tween the circuit board and front panel as short and direct as possible is good practice, and with the Freeze Frame it is im- portant because the high signal gains in the sensor-processing amplifier at maximum sen- sitivity could cause the pickup of stray signals- The circuit board is laid out so that the LEDs and the STKOBE-THIGGEK OUtpUt jack J2 are on an edge of the board PIG. 6— ANOTHER DART hitting another water balloont but from directly above. where they can look out through holes in the front panel when the board is mounted at a right angle to the panel with "L" brackets- i rn n 3 33 Providing a miniature phone jack (Jl) will allow interchange- able sensors. Using different style jacks for the trigger input and strobe outpnl prevents the possibility of damaging the Freeze Frames circuitry if a high voltage on the flasli unit were suddenly connected to the input of the amplifier circuit!^': Even if you're going to be using only one sensor, having it re- mote from the rest of the circuit- ry is an advantage because it makes it much easier to set up photos and to protect the trig- ger parts from splashes and other abuse. Make the sensor assemblies with heat-shrink tubing and small diameter coaxial cable such as RG-174/U (see Fig. 3). Both the phototransistor and microphone are polarized com- ponents, so mal^e sure tiieir positive sides (the collector in the case of g2) connects to the center conductor of the coaxial cable, which, in turn, connects to the tip of the phone jack. Note the resistor in series with the phototransistor: we mounted it at the detector end of the coaxial cable and made the heat-slirink tubing long enough to cover both it and most of the case of Q2« The space between the coaxial cable and the outer heat- shrink tubing was filled with a little silicone rubber An infrared photodetector is recommended because it allows a setup under limited Ouores- cent lighting, which is low in IR, At the same time, many of the events that will be triggering events (such as things blowing up. for instance) are high in fR, You will need to modify a (lash extension cord by replacing its normal camera-end connector ^ with an RCA plug. There are a g couple of things to be aware of Z here. First check I he polarity of -| the voltage on the flash cord; $ the positive side must go to the ^ anode of SCR I (the center of the g RCA jack) and the negative side :^ to ground. Also, the voltage on 3 those leads varies widely: on I some strobes it might be only a ^ cotiple of volts, while others Qj might be over 200 volts. There is fairly low energy Itere in either 34 case, so we* re not talking about RG. 7-AIR-FILLED BALLOON hit by a pellet. The streak on Uie right side is the pelleL RG. 8— WATHR-RLLED BALLOON hit by a pelEeL The sound sensor was used with the report of the gyn providing the event trigger. RG. 9-^GHT BULB hit by a pellet The del ay was set at its minimum value for this shot ■' - V' RG. 10— THE LIGHT BULB is almost to- tally gone in tills picture. Don't forget to wear goggles when shattering light bulbs* a lethal situation. Butyoull def- initely feel the higher voltage ff you touch it. If you don't want to purchase an extension cord to be dedicated to the Freexe Frame* you might be able to cut your existing cord and patch the tvvo ends together with an In-line plug and jack pair Make sure the male connector on the end of the cord is connected to the flash. Figure 4 shows the completed unit, lasting Any testing procedure should start with a close visual inspec- tion of your work. Make sure component polarities have been obsened. that all solder joints look good, and that there are no solder bridges on the circuit board. Don't plug in a sensor yet — our iniUal tests won't need one. Snap in a fresh 9- volt battery and turn the unit on by rotating the sensit ivity control clockwise bevond the detent; the power In- dicator (LED3) should light. If not. check for a dead battery, short circuits, etc. Set the SBNSiTivriT (R8) and DELAY (R12) controls to about the mld-polnt of their rotation, and set the sHoimi^oNG switch {S2) to "short." With a wire jumper or clip lead, short the tip and ground lugs of the Input jack Jl logethen If everj-^thlng^s working properly you should see both the trigger and fink LED*s flash briefly and appar- ently simultaneously If neither LED flashes, it could indicate problems in the sensor^process- ing amplifier, so check the cir- cuitry associated with ICl-a and -bp the polarity and assembly in- tegrity around diodes Dl and D3, and the circuitry associated with ICI-d. If only the triggkh LED lights, it could indicate problems In the timer circuitry associated with 1C2 or the final comparator ICl-c. Switch S2 to "long," and once again short the Input. Now you should be able to see a discerni- ble time delay between the flash from the trigcick and fire LED's. If you don't see an ob- vious delay It could mean prob- lems with the timer or with S2 and CIO, Now plug in the microphone sensor Wiih the sensitivity control set to about mid-range, a finger snap from within a foot of the microphone should cause both the TRiGni':R and fire LED's to light. At maximum sen- sitivity, a finger snap within sev- eral yards should trigger the unit, and at minimum sen- sitivity you wili have to be wlth- in a inch or so from the microphone. If there are no ob- vious differences in the sen- sitivity of the unit as the SENSITIVITY control is rotated over its range, check the wiring around potentiometer R8. If there is no response from the microphone as an input, check the wiring of the phone plug and coaxial cable of the micro- phone, as well as the polarity of the microphone. Plug in the IR sensor and point it at an incandescent lamp (fluorescent or Krypton lights might not have sufficient infrared energ\^ to be detected by the phototransistor). and set the SENsrrfvrr\ control to mid- range. Passing your finger in front of the photolransistor should cause the trigger and FiRK LED's to Hash briefly Strik- ing a match or lighting a ciga- rette lighter in front of the sensor should trigger the unit. If there are problems here, check the wiring of the senson in particular the polarity of the phototransiston Finally mate the RCA plug on the end of your modified llash extension cord with the strobe jack and lum the strobe on. Set the ARM/SAFE switch (S3) to *'arm'* and trigger the Freeze Frame, The strobe should flash when the hre LED flashes. If not, check the strobe first, mak- ing sure Its battery is good by firing it with its own test switch. Then check the modifications youVe made to the flash s exten- sion cord; make sure that the positive voltage from the strobe connects to the tip of the RCA plug. If there are still no results, check the SCR. Using the Freeze Frame The Freeze Frame helps you to get shots that would be difficult to obtain otherwise. But that SHAtlOW iOWl FIG. 11— YOU CAN TRIGGER A MILK DROP by polnling an IR emitter and !he sensor in the same direction toward the space through which the drop will fall through. You can look forward to giving your imagination a workout as you figure out what sensor to use, how to use It, and how to light the subject — not to men- lion thinking up an interesting picture in the first place. Each situation will be slightly different, but to get you started well cover first some basic prin- ciples on the camera side of things, and then look in detail at how the Freeze Frame pro- FIG. 12— THIS MILK CROWN is formed duced the photos shown here, after the drop hits. As we said in the opening, the essential idea Is that you're go- ing to be exposing the film with a brief flash of light while the camera shutter is held open, rather than the usual way of lighting the subject and briefly opening the shutter. The first obvious implication of this is ^ that the photography must be | done in the dark — not | darkroom dark necessarily, ^ where every tiny little crack ^ must be sealed against light, ^ RG.i3^THis MILK COLUMN forms later but dark— a moonless-night-in* m m the sequence. the^country^ kind of dark. % Sensor selection is usually 3 doesn't mean that they're neces- pretty obvious. If the event that g sarily going to be easy. The qual- you want to photograph makes z ity of the pictures you get will a sound (like a popping bal- i depend to a large extent on how loon), use the microphone. If carefully you set up the shot, the event Is very quiet, makear- 35 rangements for the event to in- terrupt a light beam. In the case of the milk drop, we found that milk was surprisingly reflecUve of infrared, and we were able to exploit this. Some events (like an exploding firecracker) pro- duce a flash and pop giving you a choice of sound or light sen- sors- After setting up the strobe and sensor you will need to do some trial events to get the proper sensitivlly and delay set- tlngs for the Freeze Frame, Since you won't be shooting any pictures, you don't have to do this part in the dark. You can get a pretty good preview of the photo just by watching the event when the strobe flashes. Persistence of vision will hold the image on your eyes retina for a short time, and you can get a feel for whether the delay is right or needs to be shorter or longen The range of delay is from 0.5 millisecond to 12 milli- seconds when S2 is set to "short" and 10 milliseconds to 0.25 second when set to 'long." Proper placement of the flash makes a big contribution to the quality of the photo. For exam- ple, backlighting the subject slightly {placing the strobe so that it lights the subject from behind) will keep any back- ground clutter from showing up on film. When backlighting, make sure the strobe doesn*t flash directly into the camera lens or close enough to cause lens flares, unless you want them. Strategically placed **light baffles" can make things that you don t want in the photo, such as supports for the sub- ject, disappear by keeping them in shadow. Sheets of cardboard would be our choice material. ^ but we used books or whatever g else we could lay our hands on, Z When you're trying to freeze motion, you need brief flashes I of lighi/Strobcs that arc too § "smart" can produce a flash that Is amazingly long; we figure z several milliseconds judging a from the biurrcd results of our I first shots. Switch your Hash to ^ its "dumb" (manual) mode and iD minimum energy settings if you get blurred results. If you are 36 not able to do this, switch to FIG. 14— TO CATCH A STONE SKIPPING ACROSS WATER, we set up the camera on shore, and supported the flash and microphone sensor out in the water to get them closer to the action* not completely sure where all the pieces of a subject will be when the shot is taken- A tripod was used to free up hands needed elsewhere, but the camera can be handheld without much fear of blurring because the strobe will stop ihe action. A cable or other remote release can be used to open the shut ten but our Minolta Maxx- um 7000 had a self timer that we used Instead. We fotmd that a 2-second exposure was long enough to let us take a picture without rushing, and short enough to keep the film from being exposed. As the batten^ In a strobe ages, it takes longer for the unit to charge high enough to fire again. That can become an an- nojing delay if the Hash is inad- vertently fired during setup. The ARM/SATE switch keeps that from happening. Leave the switch In the "safe" position un- til you're ready to shoot a pic* ture, then switch it to "arm." Once we finished setting and adjusting the camera, strobe and subject placement, delay times, sensitivity, and other ad- justnients» the general se- quence for all shots was the same: il Arm the Freeze Frame and ac- tivate the self timer PIG. 15— THIS STONE was In the middle of skipping when we "caughr' It. another flash, A modern Vivitar 636AF was smarter than we were, so we wound up using an inexpensive and ancient Vivitar 253 for all of the shots shown here. You can use whatever film youYe used to; these shots were done on Kodachrome 64 with aperture settings ranging from f8 to fll. We used a fairly long lens (35— 80mm zoom) because taking som*' of these shots was a messy proposition and we wanted to keep the camera as far away as possible. Re- member, the larger the f-stop, the greater the depth of field. That is Important when you're 2) Darken the scene 3) Pray while waiting for the shutter to open 4) Do the event 5) Wait for the shutter to close and relight the scene 6) Figure out what went wrong and do the next one Balloons and darts Figures 5 and 6 were shot with the microphone sensor to pick up the sound of a water- filled bcilloon bursting. Tlie mi- crophone was placed close to the subject, just out of the frame. No protection against splashes was needed in the case of the water balloon because splashing is minimal — most of the water just falJs and forms a puddle. In the case of the water- filled balloons, the SENSirivrn' (R8J setting was important because the event didn't generate much more noise than the self-timer opening the camera shutter (With too much sensitivity; the strobe triggered when the shut- ter opened J With air-filled bal- loons, the sKNSJTrviTY is not as critical because the balloons generate a louder sound w^hen they pop. The SHORT/LONG switch {S2) was set to "short" for those shots with the delay control (R121 set for a very' short period. In fact* it was the shortest possi- ble delay in most of the photos. The balloons were all sitting on an up-ended spray-can lid for support. Light ba riles kept the support from being lit. Balloons and pellets Figures 7 and 8 were pro- duced by shooting at a balloon with an air rifie (the balloon in Fig, 7 is filled with air and the one in Fig, 8 Is filled with water). The sound sensor was used, and the report of the gun provided the event trigger The sensj- TFvrrY control was set to mini- mum. The rifle was securely clamped to a tripod about 4 feet from the target and carefully aimed during set-up. Several sheets of corrugated cardboard were used as a back-stop for the pellets. We chose a pump-type air rifle rather than a cartridge- powered one because, by pump- ing it the same number of times for each event, we found it had a more constant muzzle velocity. Because air balloons are not as messy as water ones, we used them for setup. Simply place a balloon, arm the strobe, shoot the balloon, and see what hap- pens. Don't blink, or you 11 miss the part of the event Illuminated by the flash. If what you see by the light of the flash is the bal- loon just sitting there, increase the delay. If you don't see any balloon, decrease the delay. If you re not sure what you saw, shoot a picture annvay_ (There Is such a thing as serendipity) lt*s interesting to notice the FIG. 16— A CAPACfTOR EXPLODING is really quite a spectacie if you can reafly see what happens. difference between water bal- loons burst with a dart and those hit with a pellet. While the dart simply slides in, leaving the water in the balloon almost undisturbed (Fig. 5), the energy from the impact of the pellet sets up a shock wave like that shown in Fig. 8, In some of the piiotos you can see the pellet as a streak in the right-hand side of the frame. Light bulbs and pellets Shooting at light bulbs with a pellet gun (Figs. 9 and 10) is set up the same way and with sim- llar siiNsiTiviTY and dklay settings as shooting at balloons with pellets. Safety first here: Don't forget your protective safety goggles. Milk drops This is the "classic" stop-ac- tion photo, with a tip of the hat to strobe photography *s pioneer. Dr. Harold Edgerton, Since the splash produced by the drop is pretty quiets the phototran- sistor is the sensor of choice. We tried the microphone, but couldn t keep the camera shut- ter from pre-triggering the strobe. This common picture is usually taken by having the drop fall between a colli mated light source and photodetector. We tried that with our some- w^hat less-than-laboratory- grade stands and supports. It was difficult to get the eyedrop- per we were using as a drop source in Just the right position to break the beam. After playing around for a while, we found that milk is surprisingly reflec- tive of infrared. By placing an IR emitter and the sensor facing in the same direction pointing to- ward the space through which the drop would fall, we got very reliable triggering (see Fig. 11). The SENSITIVITY control was set nearly to maximum. In these pictures we used the long delay range. By adjusting the DELAY control, we were able to get shots of both the familiar milk "crown" (Fig, 12) and the reaction column that forms later in the sequence (Fig, 13), To help visualize the distribu- tion of flow vectors induced by the momentum imparted to the resting fluid by the fluid in mo- tion, we dyed the medium— just kidding. We thought it would look interesting to put some food coloring in the drops; nev- ertheless, it shows that the fluid that was in the drop winds up in the crown of the splash. Skipping stones ^ These were fun. We set up out- § doors by the side of a small g country lake on a moonless ^ night. A convenient wall gave us ^ a di^^ place to put the camera and throw rocks from, but the m support for the flash was put S out In the water to get it closer to g the action (see Fig. 14], The mi- g crophone was used as a sensor 2 to trigger from the splash of the * stone hitting the water After en- con f//iued on page 87 Z7 TWhat do you get when you mate a power I amplifier IC with a precision op-amp? f Answer: a ^'turbocharged" audio amplifier. COMPOSIT€ AUDIO POW€R AMPLIFI€RS CHARLES KITCHIN, SCOTT WURCER, AND JEFF SMITH NOW VOU CAN BUILD YOUR OWN high -performance audio ampli- fiers from Inexpensive compo- nents and beat the high price of faclory-made amplifier mod- ules. The composlle amplifiers described here can improve stereo systems and other audio equipment with moderate power output. As you read this article you will probably lie able think of many applications for these circuits. The five souped-up audio am* plificrs are made by inserting monolithic power amplifiers in the feedback loops of opera- tional amplifiers. The "lur- bocharged" composites retain the low distortion and offset of the op-amps and the high-cur- rent handling capability of the power amplifiers. The amplifiers described here are: two simple 10- watt com- posites, a 33-watt bridge com- posite, a 40-watt composite with a single-ended summing connection, and a 70-watt com* posite with two current-sum- mlng amplifiers in a bridge con- figuration. The output power values of all circuits are in root- mean-square (rms) watts. Figure 1 is the pinout and functional diagram Ibr the Ana- log Devices AD71 UN, the preci- sion, high-speed op-amp that is a part of all the composite am- plifierB described here. The op- amps include both bipolar and field-effect transistors fab- ricated in a process known as BIFET technology. The pinout diagram is for plastic and ce- ramic DIPs. Figure 2 is the pinout di- agram for the National Semi- conductor LM 1875, the20-watt power audio amplifier (power amp) in all of the composite am- pliliers in this article. It is pack- aged in a flat-pack plastic TO-220 case. Single-unit or low-volume prices on the op-amps and power amplifiers are subject to wide variations among the vari- ous vendors. However, calcula- tions based on components from nationally advertised sources show the cost of the composites to be quite low. The component costs for each com- posite amplifier (except for power supply) were summed and divided by the amplifiers rated output power, and the re- sults averaged out to be less than SI per watt, A 10-watt composite Figure 3 shows the basic com- poslte amplifier circuit with 1C2. an LM1875. in the feed- t OfFSET NULL rjc 2 1 INPUT 3 NOMINVERTmG 6 (NPtJT OITTPUT 4 V- A07t1 OFFSET NULL 5 FIG. 1— PINOUT AND FUMCTIONAL BLOCK DIAGRAM for the AD711 JN opcr- ationaf amplifier tn an 6'pin DIP. LMtSTS -Vji -IfJ + lfj 5 o 4 2 1 RG. 4^A lO-WATT INVERTING COMPOSITE AMPLIFIER, FIG. 2«-PIN0UT DIAGRAM for the LMie75 amplifier m a TO-220 case. Circuit causes approximately 10 dB less distortion than the non- inverting configuration of Fig. 3 because the non-inverting pin of ICl, tlie AD711JN/ Is grounded. The AD711JN pro- OUTPUT Fia 3— A lO-V^ATT NON-INVERTING COMPOSITE AMPLIFIER hack loop of ICL an AD711JN. The circuit is a non- inverting, high input- impedance, unity- gain follower. It delivers 10 watts rms into an 8-ohm load at 1 kHz, with a total harmonic dis- tortion of less than 0.003%, Total harmonic distortion (THD), a figure of merit for an amplifier, is the total root-mean- square (rms) harmonic voltage in a signal, as a percentage of the voltage at the fundamental frequency. THD should be as low as possible. The maximim offset voltage of this amplifier Is 1 miUivolt. The basic composite circuit can also be configured as a low input-impedance inverting am- plifier as shown In Fig. 4, That duces more distortion when it is connected as a follower (Fig, 3) because of its large common- mode signal. Both ICk are operating within the same loop in Fig, 4, so a phase-lead network, consisting of capacitor CI and resistors Rl and R2, provides the necessary compensation to stabilize the response of both the AD711JN and the LM1875. This network can be tailored for specific ap- plications by providing a trade- off between bandwidth and phase margin as listed in Tkble 1. The THD values given for these circuits include both dis- tortion and noise. At low fre- quencies, noise is the predomi- nant error source; at higher frequencies, distortion will in- crease because of the finite open-loop gain of the ampll- iiers. Even with this frequency- related increase, THD remains extremely low over the entire au- dio range. When functioning indepen- dently, the THD of the LM1875 power amplifier vs. power out- put peaks at about 0.5 w^att. It produces about 0.05% THD into an 8-ohm load and 0,1% THD Into a 4-ohm load at this powder leveL That variation in THD vs. power level is charac- teristic of thermal feedback on the IC chip. It is also one of the benefits of thermally Isolating an external amplifier within a feedback loop, FET-lnput op-amps with low first-stage transconductance (such as the AD7 1 UN) tolerate a larger voltage swing on their in- puts than bipolar op-amps without producing the charac- teristic bipolar op-amp overload distortion. When open-loop gain decreases, producing a larger error on the summing Junction, a FET-input op-amp behaves more linearly than a bi- polar op-amp, making It the op- timum choice as the control am- plifier in composite circuits. Step response is an impor- tant consideration in many au- dio- amplifier applications. The composite amplifiers described here take advantage of the per- formance features of the AD711JN, For example, the AD711JN has twice the slew rate of the LM1875; if the AD711JN I m 3 8 as TABLE 1— PERFORMANCE VS. COMPONENT VALUES Connection Resistor Resistor 1 1 {Kilohms) (Ohms) were slower, the LM1875 could overshoot significantly before it is corrected bv the AD71 UN. On the other hand, if the AD71 IJN were much faster than the LM1875, the driver would slew to the supply rail before the buffer could respond. Higher power composites The composite circuit con- cept can be expanded by con- necting two or mofe of them together. High -power amplifiers normally Include discrete tran- sistors with high breakdown voltages (typically over 100 volts) and high current-han- dling ability Small IC power am- plifiers have breakdown volt- ages in the 30- to 50-volt range. Maximum power delivered to the load is directly related to the supply voltage. A bridge configuration ap- plies power to the load differen- tially Therefore, It can provide twice as much driving voltage to the load as a parallel or current- summing configuration. This permits higher power output from a given supply voltage (as- suming that the increased cur- rent demand can be met). Also, the slew rate delivered to the load is greater than the slew rate of either of the two IC driving amplifiers. 33-watt composite bridge The circuit shown in Fig* 5 combines two non-inverting composite amplifiers, A and B, in a bridge or differential output connection. It operates with an overall gain of 30 and It provides 33 watts rms to an 8-ohm load with less than 0.002% THD at 1 Capacitor -3dB Phase t Bandwidth Margin (Picofarads) (Degrees) 35 70 85* 25 25 90' Rgs. 3 and 4 — tO-watt composite amplifiers All capacitors are 50 volts, silvered-mica except as stated below, C3. — 0.01 ^F, 50 vollSp ceramic C5, C7— 10 ^jiF. 35 volts, aluminum electrolytic C6, C8— 0,1 50 volts, ceramic C2. C9— 1 liF, 35 volts aluminum electrolytic Fig, 5— 33-watt composite AH resistors are y^-watt, 5%, met- al-film except as stated below. R7, R15— 1.500 ohms, 5-watt,20%, wirewound All capacitors are 50 volts, 5%, silvered-mica except as stated be tow C2, C3. CIO, C11, C14 to CI 7— 0.01 50 volts, ceramic C5. C7, C20, C22— 100 |iR 35 volts, aluminum elecfrolytic G6, C8. C21,C23— 0.1 piR 50 volts, ceramic C25-C32— 1 ^R 35 volts, alumi- num electrolytic 09, CIS— 0.47 |iR 20 %, 50 voltS, polypropylene C12, C24— 0.27 plR 20 %, 50-volt mylar Rg, 7 — 40-watt composite All resistors are i/i-watt, 5 %, met- al-fllm except as stated below R6, R8— tOOO ohms, y-t-watt, 1 metal film R7, R16— 2000 ohms, y4-watt. 1%, metal film R11, R17— 1 ohm, 5'Watt, 20%, wirewound R12, R18— 0.33 ohm. 6-watt, 5%, wirewound All capacitors are 50 volts, 5%, sllvered-mica except as stated below kHz. AmpHlier C is a DC servo amplifier. Amplifier D inverts the Input signal 180° so that the output of ampIHier B is non-inverting Willi respect to llie circuit*s in- put. The low input-impedance of a high-gain inverting com- posite amplifier makes it diffi* cult to drive. To overcome this, two non-inverting composite amplifiers have been configured as a bridge amplllien and one of them is driven with a single op- amp inverter. C2, G3. C7. Ca. CI 5, CI 6— 0,01 p-F. 50 volts, ceramic CIO. CI 2, C18. C20— 100 |jlR 35 volts . aluminum electrolytic C11. C13, C19, C21— 0,1 piR 50 volts . ceramic C23"C2a— 1 |iF. 35 volts, alumi- num electrolytic C4, C5— 0.47 ^iF, 50 volts, 20%, polypropylene Fig. 8—70 watt-composite All fBsistors are v^-watt, 5%, metal- film except as stated below R4, R8, R23, R27— 1000 Ohms, Va- watt, 1%, metal film eS, R9, R24, R2e— 2000 ohms, Va- watt, 1%, metal film R12» R16, R31, R35— 1-ohm, 5- watt, 20%t wirewound R13, R17, R32, R3&-0.33 ohm, 4- watt, 5% wirewound All capacitors are 50 volts, 5%, sTIve red-mica except as stateci below C3, C4. C7, C3. C14, CI 5, C22. C23, C26. C27, C30, C31, C37, 038,— O.Ol ftF, 50 volls, ceramic CIO. CI 2, CI 8, C20. C33, C35, C40. C42— 100 jiF, 35 volts, alumt* num electroJytic Oil. C13. CI 8, C20. C34, C3B, C41, C43— 0.1 jxR 50 volts ceramic C46-C57— 1 (jlF. 35 volts, alumi- num electrolytic C2. C5, C25, and C28— 0.47 ^iR 50 volts, 20%, polypropylene All semiconductors are Analog Devices AD711JN and National Semiconductor LM1875 Note: AD71iaN's are available in single quantities from Active Electronics, Woburn, MA 01801, and LM1875"s are available from several Electronics Now adver- tisers. Non-inverting 4 200 30 1, 77MHz Non-inverting 4 100 68 1.58MH2 Non-inverting 4 65 100 1.34MHz Inverting 4 400 30 1.8MHz Inverting 4 200 68 1.6MHz Inverting 4 80 100 890kHz •Best transient response and highest slabiHty at expense of bandwidth PARTS LIST Ct RG, 5— A 33'WATT BRIDGE COMPOSJTE AMPLIRER. Figure 6 shows the authors prototype for the 33- watt bridge amphfler The four AD711JN's are show^ mounted in the mid- dle of the circuit board (white patches), and the two LM1875's are shown mounted on the heatsink (black surface}. The DC servo amplifier The compound composite amplifiers of Figures 5, 7» and 8. all include DC servo amplifiers that share a common function although some of their intemaJ components var>^. The DC servo in Fig. 5 (Amplifier CI will sense any net difference in DC voltage appearing across the load — and therefore any DC current through the load. The amplifier will servo any net dlfTerence in DC output voltage through am- plifier B, thus minimizing wasted power. The output of each composite passes through a low-pass filter that removes AC signals from the s^rvo loop. If the output of amplifier A were more positive than the out- put of amplifier B, the output of servo amplifier C would become less positive. Its output would then drive amplifier B, which inverts the polarity again. This Inversion makes amplifier Bs output Increasingly more positive until the two DC output voltages are equaL The single servo amplifier in the Fig, 5 circuit forces the DC offsets of the other amplifiers into equality, but does not re- move them. Any DC voltage ap- plied to the circuits input will still appear at both LM1875 out- puts, amplified by the circuit gain. Therefore, the maximum voltage swing or "headroom" available will be reduced, and if appreciable, maximum output power will be reduced. If DC voltage is present on the input ^ source, capacltive input coup- 9 ling is necessary: | A 40-watt composite amplifier ^ The circuit in Fig, 7 combines ^ the outputs of t^'o non-invert- m ing composite amplifiers. Out- ^ put current is summed with 3 resistors, and the output is ref- erenccd to ground. The output s from the first composite, ampli- S fier B, is coupled to the non-in- verting input of amplifier A, No 4t FIG. 6—THE AUTHORS^ PROTOTYPE FOR THE 33-WATT composite amplifier. The two LM1S75'$ are on the black heat $irik at top, and the four AD71 1 are the white patches In a square pattern on the circuit board. ouTPin FtG. 7"A 40'WATT COMPOSITE AyPLIFIER that includes a single-ended summing connection. phase inversion Is needed be- cause the two outputs are sim- ply added together. Amplifier C is a DC serv^o that differs from its counterpart in Fig. 5 be- cause its input is referenced to ground. It connects to the inver- ting input of amplifier B. and nulls any DC offset at that com- posites output. The circuit of Fig. 7 delivers slightly more power than the bridge circuit of Fig. 5, but the bridge circuit has a faster slew rate. The circuit of Fig. 7 also has its output referenced to ground. It delivers 40 watts rms with less than 0,0029% THD at IkHz into an 8-ohm load. A 70-watt composite amplifier The circuit of Fig. 8 delivers 70 watts rms into an 8-ohm load at 1 kHz uith only 0 003% THD, It combines two of the current- summing amplifiers of Fig. 7 in a bridge. The current-summing amplifiers give the necessary high output-current handling capability. A differentia] output is obtained by connecting the two pairs of current-summing amplifiers in the bridge config- uration that allows the com- posite to drive ± 34 volts into a 8-ohm load. TVvo DC servos keep the DC output voltage at both output pins at zero. As with the other circuits described here, any off- set would cause the amplifier to lose "headroom' or clip unsym- metrically. Figure 9 shows the authors' prototype 70- watt composite amplifier. Four AD7irs are shown as white blocks on the circuit board (lower left), and three more are shown on the cir- cuit board at k)wer right. The four LM1875's are shown in a horizontal row on the heat sink (gray area) above the circuit boards. Figure 10 is a graph showing THD (including noise) vs, power output plotted from the authors* breadboard versions of the cir- cuits described in this article. For comparison purposes the plot of THD vs. power output for the LM1875 as a stand-alone de* vice has been taken from the National Semiconductor data* Building the amplifiers These circuits can be built with dual or quad versions of the AD711 if you want to save board space. The AD711JN met all of the op-amp requirements. 1 • • • • FIG, 9— THE AUTHORS^ PROTOTYPE FOB A TO^WATT composite ampltfiet The four LM1875'S are In a row on the heat sink at the top, and the seven AOTIVs are the while patches on the two circuit bodrdd. 0.1 O o o < i 0,00!L 0.1 FRE0=1 kHz MLY> A J711/L Mil 75 ;o MPOSITE 33-W BR OGE 4 1.0 10 POmn OUTPUT*{WATTS RMS} 100 FiG. It)— TOTAL HARMONIC DISTORTION vs. POWER OITTPUT for trie composite amplifiers dlscnbed tn the text and a stand-alone LMtS75, but additional components might be needed for circuit sta- bility if olher op-amps are sub- stituted. The Parts List specifies the components selected for op- timum circuit performance. The composites have ampli- fiers within their feedback loops, so the differing frequency response poles of each amplifier could interacts causing circuit inslabiltty. Therefore, proper grounding and componenl layout are important. Build all circuits on a j^round plane. In- adequate circuit #*rounding and layout can increase THD by an order of magnitude. Keep all component leads as short as possible, and connect signal grounds to the ground plane. The plane and the power grounds are tied to the common connection of the power sup- ply's filter capacitors. Power supply bypassing is important in these circuits. Lo- cate the by-pass capacitors as close as possible to the ICs when building the circuits. Separate all high -current carry- ing wires or olher conductors from low-current or high-im- pedance conductors. Keep in- put and output leads as far apart as board space wilt allow. The power supplies The circuits must operate at the specified voltages to reach the power levels stated here. Those are typically ±25-volts DC for the LMI875 power am- plifiers and ± l5-volts DC for the AD7UJNS, The highest power output is reached when the LM 1875 s are powered from ±30-voIl-DC {their maximun safe rating], and the AD711JNs are powered by ± 15 volt-DC. Mount all LM 1875 s on heat- sinks, but use an oversize heal- sink when operating any LIVI1875 at ±30 volts, its max- imum ilmiL The LM1875 dissi- pates 2 watts with an idle current of 70 milliamperesat ± 15 volts. However, dissipation rises to 6 watts with an idle cur- rent of 100 milliamperes at ±30-volts. The LM1875S limit the power supply voltage excursion of minus about 2.5 volts on top and bottom. For a ± 18-volt sup- ply the limit is about 15 watts I ms into an 8-ohm load, and for a ± 15- volt supply it is about 10 watts rms. Estimate your volt- age requirements to obtain the power needed for any specific application. Remember that low supply voltages mean cooler running circuits and higher cir- cuit reliability r-e Add a convenient hold feature to any phone! TELEPHONE HOLD BUTTON BILL GREEN WE ALL KNOW THE STORV: WE'RE ON the phone in one room and need to be In another. So we lay down the first phone, go to the other phone and pick it up, go back lo the first room and hang up that phone* and then go back to the second phone — the one we needed to be on in the first place. Or maybe we don't go back and hang up the first phone, so that when we finish our conversation we forget that it's off-Iiook — and tlien wonder why we didn t get the important long-distance call that we were expecting. (WtDl SOU ^h/, fTlWi TP RG. 2— PARTS-PLACEMENT DIAGRAM. You can make a PC board from the foil pattern we've provided and mount the parts as shown here, or use perforated construction board with point-to-point wiring. ST - I p PUSH HOLD m mi m 2,2K LED! SCR1 (RED) — OTIP FIG. 1— HOLD-MOOULE SCHEMATIC. When SI is pressed, the SCR fires and places LEDt and R1 across the phone lino. The line voltage drops to about 20 volts, which holds the connection to the phone company ^5 central office. [m- 13/itKCHES ^ FULL-SIZE hold-button foil pattern. PARTS LiST Rl—2200 ohms y^-watt, 5% R2— 1000 ohms,V4^watt, 5% R3— 47 ohms, '/^-watt. 5% LEDl— irght-emltling diode, any color SCRl— 2N5064. TIC47, MCR104 or equivalent sjiicon-controlled rectifier SI— Normally-open pushbutton switch PC board or perforated con- stojction board, enclosure, wire, solder, etc. If the above scenario Is more real than you'd like to admit, we have a design for a simple and cheap little automatic hold module. Its so cheap (about S2.00) that you can make one for each of your phones. How It works As you can sec from the sche- matic in Fig. K the hold module connects across the phone line. When all phones are on-hook. there Is about 36 to 48 volts DC across the module. When SI is pressed, the SCR fires and places LEDl and Rl across the phone line, which causes the voltage to drop to about 20 volts. Enough current flows to keep the SCR conducting when SI is released. Its also enough cur- rent to keep the connection in the phone company*s central of- fice, so the phone is on hold. When any phone is picked up, the load of Uiat phone causes the line voltage to drop to about 6 volts. At that point there is not enough current through the SCR to keep it conducting, so it turns off. When the phone is placed back on hook the line is released. Indicator LEDl glows when the hold is engaged. The gate of SCRl is kept from float- ing and turning on when SI is open by R3, and R2 limits the turn-on current through the SCR's gate. The SCR (a 2N5064 or equiv- alent) has a 200- volt forward and reverse blocking voltage. The maximum ring voltage on the phone line is 140 volts. The 2N5064S minimum hold cur- rent is 5.0 mA at 25 degrees C, Assembly We have included a PC -board foil pattern for the hold module although it is simple enough to build on perforated con- struction board with point-to- point wiring. Figure 2 is the parts-placement diagram for the board. Select a small case for the projects or mount it in- side your telephone. The pro- totype was installed in a telephone outlet box with a built-in modular jack, and a modular plug was added. That allows the hold module to be in- confffiued on page 74 Electronics Paperback Books GREAT PAPERBACKS AT SPECIAL PRICES n OP24B~TEST EOUIPMENTCON' STRUCTION ..... t5.95. DfiTails con- ftrudion ol pimple, iri' oxp&ns>ve, but ex- tremely uselul lesi ^qulpmenl AF Qer\, T&sl Bench Ampl. Au^ dio MiHivoftmetj^, Iran- Bifllor Tester and sii , BP26r— HOW TO 'use OSCILLO- 3C0P1S AMO OTHER TEST EQUIP^ Ij^MT _ UJ». tsnng the cndltogoop^r IS not rcaFty toc^ ditlicuil Thts booli explaina all the standard conlrolB and runctions Other :L equipment is a\%o tio- scftted BP265— WORE , ADVANCED USES OF THE MULTI- ttiese lecttniques to leal «nd analyze the pinlnrTnanoe ot a van- «1y ot comptinents Also see how to buftd ad-fiRs ta extend mulU- BP256— tNTRO TO LOUDSPEAKERS AHD ENCI.OSUFIE DESIGH $&.9S.\Ato ciDtofq thfj vancty ol Cin-iosure and speaWet deigns m Ltse loday so ifH' rc^ador can under- stcDd the F vofyed. n CM0S1— CMOS POCKET GUIDE 1 fiB.SS. Wotks like the TTL Guides but corefs all commonly used CMOS starMkid devices SJx rna^of E^ctkv^ The tprat 5hc*s the devicg schernaiE. Mert ii a trvei doscnptton oi th^* cofnponef^l and is toAewed (Dry fyii operaiing dfit«ii». The Ixtfth ssctcfi dsts mapr applica- mm. MfNle iti9 sm and 6ti sections prawit eswniaf diCa Isr tfiai itovice and a Vst o( the lilvvintfiiamteum^ Th« liiiii tMQ secQons ;i BPZ99— PRACTICAL ELECTflOHIC FILTERS , — Pte^enis a do^- en ten based praclieat projects wiO appik^ations tn and anMmd Ifit homo or n cansmictof ^ Wirkshop^ ComplBte constnictiOr> de^ n BP24&— MORE ADVANCED TEST EQUIPMENT CON- STRUCTION SS.95. Ereven more iDsl equipment con- struction proiOClS. Tbey mdude a digital voltrnirier, capaoSancs meter, currant tracer and: wore OlGlTAt AUDIO PROJECTS cuts io bujid ard ei- periment wiih In- dudes A^'D oonveftef. input ampEifier. digital delay Im, oomfMnder, echo eflect and rtiOfD n eP303— UNDERSTANOmO PC SOFTWARE M.W. TTias book ^ help you urtderslarxl the basica o( vonous types d business «itmm in oommon use. Tjfpm$ d scftiMft oave<«d incfcxje word pio- ICS ^togtmm , dasiaop ptijfcshng. dMlHttkl. spieaiMiQA arid utl^ SP247— MORE I ADVANCED M10I PROJECTS _SSJ1 Qfcuits included are a MIDI indcatOJ THRU bOix^ merge umr. code generator, peda^ pro- grammer, channelizer, and analyser ~ BP257— INTflO TO JUUdEURRAIMO^ SS.95. Amateur is a uiiCfue and lasematviQ hobby. This book QiMlS tne rkewcomei a own- prehensile and easy lo underhand guide to the subject. n ['^ BPSQ^P RE AM PU- RER AND FILTER CIR- cyrrs Piowsas orcuitt and badtgrovnd irrfo lor a range of pra- amplifiers, plus tone con- trols. Mtors. mixers and more. All are htgh-perler- mance orcuils that can bo butit al a reasonabkr cost PCPUG— ELECTRONIC [ ] BP2S1— COMPUT* ER HOBBYISTS HANDBOOK %&3S. A wrapup d ev- efythtng ibe computer hobbyist needs lo know m one easjr to rang* oi ttsaful nlif ■ once RtMn^ a a sn* 9^ somfi. PROJECTS FOR HOME SECUR- ITV $tO.Q0.25 projects ranging from a sinfjio-doof pfotection cir- cuit ihni can Do completed in an hour or two. lo a sophisticated muiti-citannei security system. Each protect IS doscr4}6d Bi detail ol bow It WMta. inattuctiarks kn buidng ml It^ig^ and liow to t tome ELECTRONIC PflOJECTS HOMESikuitlTT Q □ WTROOUCnON TO SATELLITE TV^„ tfl.». A dafiresvii midixlion to Ihe sjj*i|ea wrr&en ttw pix^e^^s^ntl efigmeef, elcclTDncs anthusiast Or {jtfian wtio Mailt to krww more tJotore l?wy buy 0 ■ 10 at □ BPl 90— ADVANCED ELECTROHK; SECURITY PROJECTS..„4S,95. Indijdos a passrve mtra-rad detector, a liber-op(s loop alarm, corr^utar-based aianns and an unusual torm o( ultiasoryc intruder deieciof □ BPZK— POWER SELECTOR GUIDE ^0.00. Conviete gu^ lo semconduc- lor poMor devices More ihan tOOO power tiarxHmg dOvices are included They are labutoted in alptia-numetic sequency. by tectvwial specs Includes power diodes, TtiyttslOnl^ Tnacs, ftwwr Transistors arid FETli n BP234— TRANSISTOR SELECTOR GUIDE ttom Companion volume 10 BP23S Book cowrs more than 1400 JEDEC. JlS. arid bfaiwl-specific devKes Also conuum lissmg by case type, and e^ectronc parameters. Includes Darlington ^ansJ3lors. fwgn-votaQa devices, higivajrrani devicas. hi^n pc^wer devices □ B P » ! t MM I MATBIX SOARO PROJECTS.^ IS^. Hefe aie 20 useM circuits that can Oe bmtl on a mn>^mMm txsard t^M ts |ust 24 boles by ten copper-tod stnps n BP! IT— PflACTlCAt. ELECTRONIC BUILOiNa BLOCKS^OOk 1.^.^.79. Oacdalfn, Timers, N«e Garwiicn, Rec&Aers, Comparators. Tnggers and more ' LAIICUIAO£^^.SC«S. T1^ 68000 ts a assefnOiy ttfiguage ^loeases . Hare^ wtiai you need to know n BP179-ELECTRONIC CIRCUITS POR THE COMPUTER COKTROL OF ROBOTS ..... %TSQt, D^a and circmlstor mlerlacing The computer to the robot's motors iitvS sensors. CHECK OFF THE BOOKS YOU WANT □ BP£S9-^£rnNG THE MOST FROM VtMJR MULTWETER^ S5^. Covers ba&ics of analog and c^grial meiers. Methods ot component miwtq mdkxtos tarsisiors. ihyrdctots. lesistors, capacitors arxt odior actnw and passive deuces. □ aPSr— IC PROJECTS for BEGINNERS„.^5a PoMjr suppLes. radto and audio cinxiits. oso iaiors, bmers, swficttes. and more, tl youcanusoa sotoohng won you can buiid tfie$e devices [ BP37^50 PROJiCTS USING RELAYS. SCR S 4 TRiACS 15,50. BuOd prr- onty indicators, bght moduialors. warmnig devices, light dimmefs and more I RADtO^iOd RADIO HOOKUPS^M.SlilO- Repfumt of i92* booklei pnssents radio circijJts of tt» era indudirig legenerative, neutrodyrie, reRea 4 more BP42— SIMPLE LED aRCttTTS.... %5M. A lar^ s eie c t i gi ot sfliple appbctf tons tor Itus s^mpte etoctronit component < BPl2a— AUDIO AUPUFIER COWSTRLlC1lONL_».75. Constmcavi dMaai tor prwips and pcmer atnctOmn yp Vwough a lOCNuaet OC-cou^ed FED ampMar BP93— CRYSTAL SET COMSTRtlCTION^ $S.50-Ev«ryff«q yoy rwd to krvw al»ut bu^dd^ crystal tit>o rK^fvers BP2S5— INTERNATIONAL RADIO STATIONS GUIDE . S7.95. Proxies itvj ca-saal Ii:s3enad and generating the 40- ktiz modulated infrared drive sig- nal. L^t's take an in-depth look at how those two tasks are accom- plished. A schematic depiction of the 16- key keyi:jad is shown in Fig. L Ifyou*re Inleresicd in the "down and dirty" pm- gram de- tails, a fully docu- mented ma- chine language listing (IRXMIT ASM} is av-ail- ableaspart ofa self'unarchh'- ing ZIP file called IRSYSTEM. EXE on the I^-BBS (516-293-2283. 1200/2400. 8N11 The keypad used in this project was from All Electronics Corp.. PO Box 567, Van Nuys, CA 91408 (800) 826-5432, (part No. KP-16K Any fimclionally equivalent keypad can also be used. Each key con- tact surface inside the keypad is an intersection of a particular row and column. As you can see from Fig. 1, the o key is an inter- section of row 1 and column L and the 9 key is an intersection of row 4 and column 3. Al- though the layout of the keys in Fig. 1 doesn't match the actual layout of the keys on the key- pad. Fig. 1 is electrically correct- Also, while the 5 x 5 grid allows up to 25 kc>'S* the actual keypad has only 16 keys. Rows 1 through 5 are nor- mally held at a TTL high leveL To determine which key has been pressed^ ICl successively ap- plies TTL logic lows to each row from 1 to 5, and then reads the output of the columns. When a key is pressed, its row and col- umn arc shorted together, and the low applied to the row is transferred to the column (which is normally held high). As an example, if row 1 is being scanned and the o key is de- pressed » a low will be read by IC 1 at column L That low will be decoded as a "0," A succession of "0'* characters will be sent as long as you hold the o key de- pressed. Table 1 shows how the pins on the back of the keypad connect to the pins on the mi- croprocessor and the corre- sponding microprocessor ports, Inirared tmnsmitter 71ie enemies of the infrared signals that emanate from the transmitter are incandescent light, fluorescent light, and sunlight. Large amounts of 1 to m o B 47 RG, 1— KEYPAD SCHEMATIC, Each key contact surface *s an intersection of a par- Ucular row and column. The physical layout of the keypad does not match the elec- trical layout. TABLE 1 KEYPAD CONNECTIONS Keypad (see Ftg. 1) Microprocessor Pin Port JM 34 P17 J1-2 27 P10 35 P24 JI-4 20 P11 J1-5 36 P25 JV6 29 P12 J 1-8 37 P26 J2-1 30 P13 31 P14 Also jumper Jt-6 to J2-3 on back of keypad modulated, noisy infrared ener- gy are produced by those light sources. Most of the inter- ference is modulated in the 50- or 60-Hz range. A simple red plastic filter will screen out some of the noise, but to over- come the extraneous infrared interference* the transmitted infrared signal must be modu- lated at a high carrier frequency. In our system* the carrier fre- quency is 40 kHz^ — which Is re- quired by the GP1LI52X receiver module used. The IR transmitter schematic is shown in Fig, 2. The 40'kHz carrier originates at pin 11 of ICl (aDDRICSS tJVTCH ENAI^LE, OT ale] which provides a square wave that is exactly one fif- teenth of Id's oscillator fre- quency. In our system* that is 6 MHz divided by ls* or 400 kHz. The 400-kHz signal is applied to the CLK input of IC3* a 4017 CMOS decade counter which is configured to divide by 10 to ob- tain the desired 40-kHx carrier. The resultant 40-kHz sign a I at pin 12 of IC3 is gated by the output port P15 (pin 32) of the microprocessor and fed to pin 3 of inverter/driver IC4, a 4049 CMOS inverting buffer That buffer serves Iwo purposes: First* it Inverts the idle state of IC3 so that MOSFET gi is turned off when no characters are being transmitted. Second, it provides sufficient drive to the gate of Ql so that maximum in- frared energy is emitted by the infrared LED*s. As stated before, the 40 kHz carrier signal at pin 2 of IC4 drives Ql s gate which turns Ql on and illuminates two IR LED's (LEDl and LED2) producing a 40-kHz modulated IR signal, A logical "I" is a I-millisecond pulse of IR light and a logical "O" is a 0.5-milHsecond pulse. Each bit is scparaicd by at least 0,5 millisecond to allow the IR de- tector to synchronize. Figure 3 depicts how a Iraiisml 1 ted character "9" wotiid look on an oscilloscope. Tlie transmitted "Is" and "Os" are comvined in groups of eighi to form 16 dis- tinct characters as showTi in 1^- ble 2. To av^oid sequence errors and to allow the receiver to syn- chronize between transmis- sions, a 50-millisecond idle period is placed between trans- mission of each character. Infrared receiver The receiver* whose sche- matic is shown in Fig. 4, is based on the Sharp GPiU52X IR module, and the INS8048L mi- croprocessor. The IR receiver de- tects and decodes I he IR signal from the transmitter. Once again, if you want the raw de- tails, consult the machine code listings IRS\VITCH,ASM. IR- SERVO.ASM, IRRECROB ASM and IRPOT.ASM. which are part of the ZIP file called IR- SYSTEM.EXE on the RE- BBS. The GP1U52X IR Receiver/De- modulator is a hybrid IC/in- frared detector A PIN ( posit ive- intrinsic-negativel photodlode feeds an amplifier and li miter that provides a strong* clean signal which is filtered to re- move all frequencies outside the 40-kHz passband. The resul- tant signal is demodulated to provide a waveform minus the TABLE 2 KEYPAD CHARACTERS Row Col Binary 0 R0W1 CQL1 00001111 UPC R0W1 C0L2 10100101 owe R0W1 C0L3 10110100 1 R0W2 C0L1 00011110 4 R0W2 C0L2 01001011 7 R0W2 C0L3 01111000 2 R0W3 COLl 00101101 S BOW3 C0L2 01011010 8 R0W3 C0L3 10000111 3 R0W4 COLl 00111100 6 R0W4 C0L2 01101001 9 R0W4 C0L3 10010110 UP V ROWS C0L2 11000011 DW V ROWS C0L3 11010010 ADO R0W5 C0L4 11100001 DEL R0W5 COLS 11110000 ■1 cT ceT 26 40 01 VOLTS DC C5 1 \ C6 + 5V C7 ICl tNS804&L XTALl mL2 RES 32 P17 PIO m P11 P25 PI? P26 P27 P19 P14 P13 Tl PSE P22 P21 P20 D87 oaG D85 Ddi D83 DZ2 D81 DBO ALE 34 Jl'l Cf J 1-2 35 J 1-3 26 J1-4 36 Jt-6 29 . . J 1-6 37 38 in 31 J 2-2 J2-3 0 nc £J "■ s A1G 22 A9 21 S A8 19 s i Q 10 17 S 16 N 15 S 14 s 13 12 11 ROWl C0L1 R0W2 C0L2 R0W3 C0L3 mm C0L4 R0W5 COLS ra-KEY KEYf%D R3 All A12 ADDRESS JUMPER BLOCK ALE 20 / 19 / / 17 / 16 15 TJ / / 1 1 / 01 £A / 7A / 25 / 3 / 4 / 8 / 7 / e / 9 .0 22 A12 2 All 23 ALE 1 27 [28 OE D7 06 D5 D4 D3 D2 D1 DO AID A9 Ae A7 A6 A5 A4 A3 A2 A1 AO DE IC2 87CB4 FIG.2— IRTRANSMHTER schematic. The 40-kHz carrier is denved by dividing icrs oscillator frequency (6 MHz) by 15, to get 400 kHz, which is divided by 10 by IC3. 14 15 CLK IC3 RES 4017 19 8 NEXT CHARACTER- - 50ms- TTL HIGH ni LOW I ITO - Oims- I FIG- 3— A TRANSMITTED CHARACTER weuld look like this if seen on an os- cilloscope. The transmitted "1's" and "OV are put together in groups of eight to form 16 distinct characters as shown in Table 2. carrier The demodulated si^^nal is presented to ICl via the event counter input (n, pin 39). At this time the program residing in IC2 (an 87C64 EPROM) takes over. The idle state of the GP1U52X is normaUy high. As soon as the output pin of the IR detector transitions low. ICl starts an internal timer to mea- sure the incoming pulse width. Depending upon whether the pulse width is 0.5 or 1 millise- cond, a binary 0 or 1, respec- tively. is stored in a holding register. Once 8 bits are re- ceived, ICl attempts to match the 8-bit word with a term in its internal table to determine which character has been re- ceived. How the received character is used depends upon which one of the four functions is selected. lYansistors, buffers, & relays See Fig. 5 for program -selec- tion information. IRSWITCH. ASM, the first of four programs contained in the EPROM/ is se- lected by Jumpering both ad- dress jumpers (ah and A12). Basically, keys 1— Son the key- pad select ports pjo-pi? (pins 27--34) of ICl respectiveiy The ITL logic levels at Pio-ri7 can tLtrn on a switching transistor. C4| .1 ce m 26 40 20 C3 32 IC1 PI 7 INSa04BL P10 P24 P11 P2S P12 P26 P21 P19 P14 Tl 3i 28 'i^ 36 +5V 29_ f E. 30_ 31 39 XTAL2 RES PI 5 PSE P22 PZ\ P20 D37 D86 DS5 DB4 D83 D82 D81 Deo ALE GND MODI 6P1U5ZX OUT OE 23 A10 22 A9 2t AO + 5V A11 ADDRESS JUMPER BLOCK ALE 20 19 IS \1 15 15 13 24 25 to 22 A12 2 27 28 CE D6 D5 04 03 02 01 00 AlO A9 Afl A7 A6 AS A4 A3 A2 A1 AO OE tC2 87C64 I All 23 1 FIG, 4— IR RECEIVER SCHEMATIC, It is based on the Sharp GP1U52X [R module and INS8048L microprocessor. The GP1U52X is a hybrid IC/inf fared detector that provides a strong clean signal for later filtering and demodulation. 1 JUMPERS All A12 MEMORY MAP O 0 O o IRPOT I o o IRRECROB O o I IRSERVO I iRswrrcH PROGRAM START ADDRESS -800H A12 A11 A10 A9AB A7 AeA5 A4 A3A2A1 AO ADDRESS J J 0 0 0 0 0 0 0 0 0 0 0 IRSWITCH ^ OOOOH J 1 0 0 0 0 0 0 0 0 0 0 0 IRSERVO = OaOOH 1 J 0 0 0 0 0 0 0 0 0 0 0 IRRECROB^ lOOOH 1 1 0 0 0 0 0 0 0 0 0 0 0 IRPOT = 1 BOOH JUMPER 0N=0 OR J JUMPER OFF^l FIG, 5— PROGRAM-SELECTION INFORMATION. Four different programs (IRSWITCH.ASM, IRSERVO.ASM, IRRECROO.ASM, and IRPOT,ASM) are stored in the receiver's EPROM. The programs are selected via jumpers A11 and A12. drive a TVL buffer, or activate a solid-state relay. Pressing the ADD key allows any following key depression of keys I through 8 to output a high on the corre- sponding port. Conversely, pressing the Di:i. key Ibliowed by any oDieys 1 throLigh 8 signals ICl to take the following port selection low. That allows any of the eight outputs to be turned "on" or "off' individually with- out interfering with each other To see this, use a logic probe to check pio as you press add or de':l followed by a i, At>i> i should take pio high while del i returns no to low Driving servos Hobby-grade servos are com- monly found in radio-controlled model aircraft and cars. How- ever, because servos convert electrical pulses to mechanical motion, they do have many other uses. Servos are easy to use once you understand how they work. The most common hobby ser- vos have a three-wire termina- tion: positive voltage, ground, and signal input. Positive volt- age is usually -f 5-vo!ls DC and ihc signal is a TTL-compatible variable- width pulse. A LS-mil- lisecond pulse will center the servo rotor increasing the pulse width to 2 milliseconds will move the servo rotor fully clock* wise. Decreasing the puise wid- th to 1 millisecond moves the servo rotor fully counterclock- wise. So. a pulse width between 1 and 2 miiiiseconds will cause the rotor to travel in a specific direction and distance depend- ing on the applied pulse width. Pulses are normally applied about every 16 milliseconds to hold the ser\^o rotor in position. In our application, pulses are applied every 45 milliseconds. The IR remote control system can control a maximum of two hobby ser\^os as shown in Fig. 6. The program IRSERVO.ASM, which is selected by jumpering only Ai2, is used to drive them. The servos are operated by pressing the up v and down v keys for counterclockwise and clockwise rotation, respectively. The 0 key will center the selected servo rotor. Selection of servos 1 and 2 is performed by pressing i for servo 1 and 2 for servo 2, The drive signal for servo 1 ori- ginates al pin 27 of ICl {vio] and the drive signal for servo 2 ori- ginates at pin 28 {vi 1 ), Wlien ser- vo 1 is active, a high Is present at pin 35 of [CI and when sen o 2 is active, a high is pres- ent at pin 38 U^jtI You can use those outputs to drive LED In- dicators with a PN2222 tran- sistor as shown in Fig, 6. Robot remote control Do you remember Ken the robot from the April 1991 issue of Radio-Electronics? He had a mind of his own. but the IR re- mote-control system will let you teach him some manners. The IR system gives you override control of Kens motions. You will need to change or re- program the original 8748H mi- crocontroller with the new version of the machine lan- guage. IRROBOT.ASM, which is included in the ZIP file IR- SYSTEM.EXE on the RE-BBS, (A new, preprogrammed 8748 H containing IRROBOTASM is available from the source given in the Parts List.) The IR receiver unit, which must be mounted directly on the robot, decodes the ui' v key as forward, i>own v as reverse, up c as left, and down c as right. The o key stops Ken in his PARTS LIST— TRANSMITTER AIL resrstors are Vk-watt, 5%. R1— 10 ohms R2-R4— tOOO ohms CapacKors CI , C2— 27 pF. ceramic dfsk C3^1 jiF. 35 vol Is. tan! alum C4-C7— 0.1 |iF, Mytar CS— to \Lf, 10 volts, eleclrolyiic S^micoitdyctors ICl— INSe048L micfoprocossor (Na- tional) IC2— 87C64 EPROM wilh transmilJer program installed IC3— MC140t7 CMOS decade counter IC4— MCH049 CMOS tnvefling buffer Di— lN400t diode 01— IRF222 MOSFET LEDt LE02— T08 infrared light-emit- ting diode Other components XTALi-^-MHz crystal Kiscellaneoufl: On/off switch, 16-key keypad (All Electronics part number KP-16 or equivalent), PC board, plastk: case, 6-volt t^attery, ntibon cabie, wine. sxMer, etc. RG, 6— THE IR REMOTE CONTROL SYSTEM can control a maximum of two hobby- grade servos. The LED's indicate which servo is active. as well as details on how its done, can be found in the head- er section and main body of the program IRRECROB.ASM (in* eluded in IRSYSTEM.EXE). That program is set by jumper- Ing only am. Figure 7 details the connections between the IR re- ceiver unit and the robot. Remote potentiometer Program foun IRPOTASM, re- tnolely controls a digital poten- tiometer. The DS1267 dual solid-state potentiometer (made by Dallas Semiconductor) is composed of 256 resistive sec- lions, T^p points are provided between each resistive section, and each tap point is accessed FIG, 7— THE IR RECEIVER can be mounted on Ken the robot (see Radio- Electronics, April 1991) to give you full control over him, traclts. If you want Ken to roam as he originally did* the uku key puts him in his roving mode. All of the key combinations and codes used to manipulate Ken. P27 P24 ICl Pt2 PH FIO GfID — CI 133 j PHmZi 180f2 'LEO POTENTIOMBtR 1 INDICATOR 35 29 IK 28 27 PN2Z2Z 4r I 2 'LED POTEKTIOMETER 0 IfJDiCATOH T8Gn +5V LI 0StZG7 POT 0 W1 RST CLK POT I 14_ W012 HO LO It 10 -ML m RG. 8— THE IR SYSTEM can remotety control a DS1267 dual scltd-stale potentro meter 55 1 n2 GROUND CASE^ lof M0D1 MOT , v^>%'>?ig fer^^r^g LED21 LED1 I ■ mti ^ H X'^ — - — h~ — [ri k[gW«ru"CttW — ^-'^^^^Bri^ I ^ 4iJB«!i*i.o-*4-'" B O 0 6 0 Q o - g RG. 9— THE TRANSMITTER AND RECEIVER are on the same PC board- Build the transmitter first, checking off each part in the transmitter parts list as you go. Put it aside when done^ and then build the receiver^ o ^ol IlllloIIlIIoooe II 00 V ' 33/4 INCHES- COMPONENT SIDE for the tR transmitter and receiver boards. CI o y o — OOOD- ' 3^/4 INCHES- SOLDER SIDE for the iR transmitter and receiver boards. by the wipen By clocking a 17- bit digital code into the dq pin, each potentiometer within the IC can be adjusted indepen- dently. The part is available with different resistance values, de- pending on your needs. Figure 8 shows how to con- nect the DS1267 to ICl on the receiver board. The up v and DOWN V keys raise and lower the resistance, while t> selects po- tentiometer 0 and I selects po- tentiometer 1, We use the o and i keys here instead of 1 and 2 because the DS1267 data sheet PARTS LIST— RECEIVER At! resistors are l^4-wat1, 5%. RI, R2— not used R3. R4— 1000 ohms Capacitors CI , C2— 27 pF. ceramic disk 03— 1 jjlF. 35 volts, tantalum C4. C5— 0,1 jjlR Mylar 06, 07 — not used 08—10 p.F, 10 volls. electrolytic Semiconductors ICl— INS8048L microprocessor {Na- tional) IC2— 87C64 EPROM with receiver pro- grams installed 103, 104— not used D1— 1N4001 diode Q1— not used LED1. LED2— not used Other components XTAL1— 6-MHz crystal MODI— GPtU52X IR detector module (Sharp), or Radio Shack part number 276-137 Miscelianeous: On/off switch, PO board, two jumper blocks, wire, solder, etc. Note; A complete kit of parts for the transmitter and receiver (not includ- ing a battery and case) is available for $49,00 plus S3.00 S&H from Fred Eady, PO Box 541222, Merrit island, FL 32954, Check or money order only. For technical assistance call 407-454-9905, labels the potentiometers as 0 and 1. Again, pin 35 of ICl is high when potentiometer 0 is active, and pin 38 is high when potentiometer 1 is active. You can also use the LED indicator circuits connected £0 pins 35 and 38 of ICL Both jumpers All and AJ2 must be removed to ac- cess IRPOT.ASM. Common factors The receiver and transmitter circuitry are almost identical, and they are built on the same PC board. Parts common to both circuits have the same part number, and parts added or removed from one of the cir- cuits will have corresponding part numbers added or re- moved. So, when a particular part number that's contained in both circuits is mentioned, the pan performs the same func- tion in both circuits, Wlien a part contained in only one of the circuits is mentioned, The refer- ence is limited to that particular circuit. The first and most important part common to both circuits is ContinuGd on page 76 BUILD A FOR AUTOMOTIVE ACCESSORIES ADDING ACCBSSORIES TO A CAR OR truck was once a simple chore. Just run some heav>^ wire from the car battery to the load, through the Fire walJ to the dashboard* and connect the wires In series with a fuse and a toggle switch and the job was complete. With that huge, high* current switch mounted on a bracket strapped to the dashboard, a Hip of the wrist would activate the new accesso- ry and testify to the owners ex- pertise and initiative. But a plain old toggle switch hanging from the dashboard doesn't cut it anymore: it pre- sents a tacky, unprofessional appearance In todays motor ve- hicles. Besides looking bad. an old-fashioned lever switch could make you look bad, too. If you were to leave the power on when the Ignition key is off. you could kill the battery You can personalize your dashboard and avoid those tog- gle'SwltcIi headaches with our simple pushbutton power con- troller for high-current accesso- ries. When youVe finished, youll have a "smart" switch that blends in with the existing dashboard controls. An LED can also be installed to indicate the power state. The motor vehicle power con- troiler is si>ecially designed for under- 1 he-hood mounting. It is de- signed to switch a high current when it receives a posi tive- going pulse from a momentary switch. It could also be con- trolled by a spe- cialized device like a remote control radio receiver Pulses from a 555 timer IC could Add that custom touch to your automotive accessories with our power-'Controller module. DAVID A SWEENEY be used to trigger the power controller to flash warning lights. For pushbutton use, only a thin control wire runs to the dashboard, which helps make mounting easy As shown In Figure 1, a small switch, with an LED power indicaton controls power to a load, which could be lights, a siren, a winch sole- noid, or any other device that draws up to 10 amps. A fuse« which should be mounted as close to the battery as possible, protects the switched power Pressing the dashboard- mounted switch once activates a relay that supplies power to the load; pressing the switch a second time disconnects power from the load. The author designed the pouxr controller for a pair of quartz halogen lights that he added to his can The power con- troller delivers the 8 amps re- quired for the fog lights, and it^ controlled from a liny pushbut- ton blended into the dash- board, as show^n in Fig. 2. The power controller operates only with the ignition on. Therefore, if the driver doesn't remember to turn off the lights, the controller will. That way you won*t find a dead battery the next time you go to drive the car. Cireuitiy Figure 3 shows the DASHBOARD RG. 1^THE POWER CONTROLLER Eets a smafi pushbutton control power to a load that draws up to 10 amps. RG, 2— THE AUTHOR DESIGNED the power controller for a pair of quartz halogen lights that he added to his car. The lights are controlled from a tiny pushbutton switch blended into the dashboard. .GRO -3 INCHES- FOIL PATTERN for the power controller schematic for the power con- troller The controlJer is powered from the vehicle's accessory switch, so the load can receive power only when the ignition key is in the "on*' or "accessory" position. Relay RYl does the high-current switching (up to 10 amps), and its coil requires only 38 milliamps. When you turn on the igni- tion switch In your car and press Sl> capacitor C3 ciiarges, causing pin 2 of EC 1 (wc only use half of a CD4013 dual flip-flop) to toggle high. The high output from pin 2 of ICl is applied to the gate of FET transistor Ql. which in turn energizes relay RYL The relay connects the load (up to 10 amps) to Uie car bat- tery After C3 discharges, a sub- sequent high from SI will toggle the flip-flop again, opening RYl s contacts. Capacitor C2 re- sets the flip-flop tt> ensure that pin 2 is low and that the load is disconnected when the accesso- ry voltage is first applied, FET transistor Ql can casiiy drive an extra relay in parallel with RYl, PARTS LIST All resistors are V4-watt, 5% R1— 10,000 ohms R2— 3300 ohms R3— 1000 ohms 2200 ohms R5— 1500 ohms R6— 10,000 ohms R7— 2.2 megohms Capacitors C1— 0.1 |iF. ceramic 02— 0-02 |iR ceramic C3 — 0.3 fjiR ceramic Samioonductors ICl— CD4013 dual flip^lop 102— LM781212'VOlt regulator Q1— IRF511 field-efleet transistor D1— 1N914 6\o6e LED1 — light-emitting diode (choose color to match existing lighting on dashboard) Other components S1 — momentary SPST pushbutton switch (choose one that closely lill matches existing switches on dashboard) F1— TO-amp fuse SOI— 5-pin DIN socket PL1— 5*pln DIN plug RYl— 12-volt, 10-amp relay (Radio Shack part number 275-248, or equivalent) Miscellaneous: PC board, 10-amp terminal strip, inline fuse holder, aluminum plate, encapsulating material, wire, solder, etc. 1 '^l2VDCmEG) -II R7 2.2MEG I m C3 .3 14 D1 1Hfl14' 13, 12 11 to 9 IC1 R2 3.3K R6 lOK (FROM CAR BATTEFlVr R3 IK SI IC2 7812. GND OUT +12VDC I LED1 R5 ■ + 12V fFROM ACCESSORY FUSE) 2^ -^MOUNT m DASHBOARD VEHICLE -i-GROUND RG. 3— POWER-CONTROLLER SCHEMATIC. Because the power controller is powered from the vehicle's accessory switch, the load can receive power only when the ignition key Is on. FIG. A — ALL OF THE PARTS mount on a srngle-slded PC board for which we've provided the foil pattern. in case you want to control a second 10-amp load, (Do not connect two 10-amp loads to one relay.) An LM7812 12- volt DC reg- ulator (IC2) provides a stable voltage to run the circuitry, re- gardless of fluctuations in the vehicles power Capacitor CI provides decoupling for RYl. Construction AI! of the parts for the power controller should be easy to find at most electronics supply houses. The electronic compo- nents are mounted on a single- sided printed circuit board as shown in Fig, 4. WeVe provided the foil pattern for the PC board In case you want to make your own. Otherwise, use point-to- point wiring and perforated construction board. Be sure that the gauge of the wire you use for the load connections can handle 10 amps. A DIN socket (SOI) provides the low-current external con- nections to SI* LEDl, accessory powen and ground. A matching DIN plug (PLl) plugs into SOI to make those connections, (The load*s power and ground con- nections should be separate from the DIN connector). The DIN connector also makes it easier to change a power-con- troller module in case of failure, FIG. 5— THE POWER-CONTROLLER board is mounted on a 0.064-inGh alumi- num plate bent into a U-shaped frame. The DIN socket and the terminal strip are mounted on the sides of the U-b racket. without having to disconnect any wiring. If you don't have a 5- pin DIN connector you can use 4-conductor phone wire to con- nect the module to power, ground. LEDK and SL if you do thaL you must ground the LED to the dashboard or any chassis ground as shown in Fig. 1. A terminal strip provides the con- nections from the load to the relay contacts. 'fb make the power controller as durable as possible in a car's engine compartments the cir- cuit board was mounted on a 0.064-inch aluminum plate bent into a Ll-shaped frame, as shown in Fig. 5. The DIN socket and the terminal strip were mounted on the sides of the U- bracket. The entire circuit was then encapsulated in a clear plastic resin block (the product is called Casting Resin) as 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 '^distance education"— teaching by correspondence — through printed materials, computer materials, fax» and phone. No commuting to class. Study al your own pace, while continuing on your present job. Learn from easy-to- understand but complete and thorough lesson materials, with additiona) help from our instructors. Our Computer B.S, Degree Pro* gram includes courses in BASIC, P A SC A L and C languages — as well as Assembly Language, MS DOS, CADD, Robotics^ and much more. Our Electronics B,S, Degree Pro- gram includes courses in Solid -State 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 college degree, and the absolutely neces- sary part is knowing your field. Grantham can help you both ways — to learn more and to earn your degree M in the process, ^ Write or phone for our free I catalog. Toll free, U800'955-2527. or E see mailing address below. Accrediled by the Accrediting CommUslon of tlie National Home Study Council I GRANTHAM College of Engineering eo Grantham College Road SlideU, LA 70460 shown In Fig. 6. Encapsulation Is not necessarj', but it helps the circuit withstand the vibration, humidity: and temperature ex- tremes found under the hood of a can You should make sure the power controller works before encapsulating It, After encap- sulation, the unit becomes "dis* posable" if It falls because it can't be repaired. Installation After you've encapsulated a working module, you can mount it in your car Find a ty If there's no removable plug in the fire walL tr^' to snake the new wires through an opening where existing wires already pass through, h's often helpful to poke a coat 'hanger wire through the fire wall and to use a hook bent on the end of the hanger to pull the wires through In much the same manner as an electrician uses a fish tape to snake electrical wires through walls. Next connect power from the load to the conlroUer and then from the controller to the car FIG. 6^THE ENnRE CIRCUiT is encapsulated in a c[ear piastic resin block help it withstand vibration, humidity, and temperature extremes. place for the module somewhere under the hood away from a high heat source, {For example* avoid the exhaust- manifold side of the engine,! Route the control wire through the fire wall and connect it to the switch and LED indicator, which you should mount in the driver*s compartment. Be sure to drill the mounting holes slowly in plastic. Snaking wires through a fire wall can be difficult. Sometimes tliere s a plastic plug that can be removed to gain access to the interior of the car from the en- gine compartment. Be sure to weatherproof such openings after the power controller is in* stalled so vour car won*t be draf- battery. After checking all the connections, Instatl fuse FK You should now be ready to sit behind the whecL turn on the ignition, and operate the load that is connected to the power controller You can expand the design of the controller to incorporate two relays, both powered by Ql. or to connect something to the normally-closed (NC) side of RYL Howeven building an addi- tional power con t roller might be just as easy. Once you get used to the convenience of our motor- vehicle power controllen you could end up adding a number of custom pushbutton-con- trolled accessories to your auto- mobile. R-E RAY M. MARSTON TWO PRKVIOUS AKrttMJ:s iSE-ir- tern ben page 58 and October page 69 explained llie operation of the popular and vcrsaHle in- dustry-standard 555 timer IC as a tnonostable and astable multi- vibrator They gave examples of its use in accurate time delayer oscillator clrcuils. This iliird article starts by discussing the 555 as the key component in a Schmitt trigger circuit. It goes on to explain tile role of the 555 in various astable multivibrator or oscillator cir- cuits with many practical ap- plications. Those circuits in- clude light- and dark- as well as hot- and cold-actuated alarms. Other circuits are a code prac- tice oscillator, a door buzzen a continuity tester, a signal gener- ator and a metronome. Various light-actuator and relay-driver circuits are included. Schmitt trigger Figure 1 is the pinout and functional block diagram for the 555 timer IC. In previous articles it was pointed out that for a 555 in the time-delay oper- ation mode, timing can be pre- cisely controlled by one external resistor and one capacitor. For astable operation as an os- cilia ton the free-running fre- quency and duty cycle can be accurately controlled with two external resistors and a single capacitor. It is worth recalling that the 555 can be triggered and reset on falling waveforms, and the output circuit can source or sink up to 200 milliamperes. or drive TTL circuits. The 555's features include normally on and normally off outputs. Figure 2-a illustrates the 555 IC as the active component in a Schmitt trigger circuit. Notice that the 555^strigge%r pin 2 and TURBSHOLD pin 6 are connected to form an input terminal Ex- ternal input signals are applied directly at that point. The OUTPUT pin 3 becomes the out- put terminal* [ntemal comparators A and B (see Fig. 1) are biased with an on-chip voltage divider. That di- vider biases comparator A at OSCILLATORS Put the 555 time to work as a Schmitt trigger or as the heart of light and temperature alarms and drivers, a metronome, and a continuity checker. "1 TB1G5ER OUTPUT FLOP RESET DISCHARGE 5K THRESHOLD COrfTROL VOLTAGE p[0. 1— PINOUT AND FUNCTIONAL eLOCK diagram of Itie 555 timer IC. two-thirds of the supply voltage, and the non-inverting terminal or comparator B at one-third of the supply voltage. Comparator A drives the R input and com- parator B drives the S input of the on-chip R-S flip- flop. When the input voltage of the circuit in Fig. 2-a rises above two-thirds of the supply voltage, the 555 output switches to its low state. It remains there until the input v^oltage falls below one-third of the supply voltage. Then the outpui switches high and remains high until the in- pul rises above the two-Uiirds supply level again. The difference between those two trigger levels Is called the hysteresis value. It is one-third of the supply in Fig. 2-a. That large hysteresis makes the cir- cuit useful in signal con- dilionlng where noise and ripple must be rejected, as shov^Ti in Fig. 2-b. Figure 3 shows how the cir- FIG. 2-'A SCHMITT TRIGGER CIRCUIT formed wJth a 555 timer IC, cuit in Fig. 2-a can be modified into a high-performance sine- to square-wave converter useful at input frequencies up to about 150 kHz. The voltage divider formed by Rl and R2 biases the input terminal (pins 2 and 6) of the 555 at its quiescent value of one-half the supply voltage (i.e., midway between the upper and lower trigger values}. The sine-wave input signal is superimposed on this point with capacitor CI. Square-wave output signals are taken from pin 3 of the IC. Resistor R3 is wired in series with the input terminal to ensure that the sine-wave signal is not distorted when the 555 switches. Figure 4 shows liow the Sehmitt trigger circuit can be made into a dark-activated relay actuator by wiring the light-de- pendent voltage divider consist- ing of po ten ti omen ter Rl and photocell R2 to the input termi- nal of the IC. Tlie potentiometer and photocell resistance values are nearly equal at the middle of the light-activation range. The inherently high input backlash or hysteresis of the Sehmitt trigger limits the usefulness of this circuit to very specialized light-sensing ap- plications. A more useful relay- driving, dark-activated switch- ing circuit is shown in Fig. 5. It acts as a fast comparator rather than a true Schmitl trigger. The riiRKSHoi.r^ pin 6 to internal comparator A of the 555 is tied permanently high by resistor r^3, while the output of the light-sensing potentiometer Rl and photocell R2 voltage divider is applied to triggbk pin 2 of comparator B. The photoresistive element for this circuit can be any cad- mi um-su If ide photocell whose resistance is between 470 ohms and 10 kikjhms at the desired turn-on light level. The circuit in Fig. 5 can also function as a light' (rather than dark-) acti- vated switch by exchanging the positions of the potentiometer and photocell as shown in Fig. 6-a, + 5VTO + 15V SIHE- WAVH INPUT Rl lOOK 10K fT f . .AAA 1 6 555 R2 100K IC2 ,01mF 1 SQUARE- WAVE OUTPUT FIG. 3— A SCHMUT TRIGGER SINE- AND SQUARE- wave generator formed with a SSS la FIG. 4— DARK-ACTIVATED RELAY SWITCH BASED on the 555 has a lot of hysteresis. The circuit can also function as a temperature-activaled switch by substituting a ther- mistor with a negative tempera- ture coefficient for the pho- tocell, as shown in Figs. 6-b and 6-c. (A thermistor with a nega- tive temperature coefficient de- creases in resistance as temper- ature increases.) The ther- mistor for this application must have a resistance value between 470ohms and 10 kilohms at the desired turn-on temperature. Thermistors arc topically pack- aged as radial-leaded disks, and their resistance values are spec- ified at 25"^ C. Stable of oscillators The 555 in the as table multi- vibrator or oscillator mode has three outstanding advantages over other kinds of oscillators; • Excellent frequency stabilit>^ with variations in supply volt- age and temperature. • Frequency variable over a wide range with a single poten- tiometer control. • Low impedance output that can source or sink currents up to 200 miiliamperes. Figure 7 shows the 555 as the scEniconductor IC in a Morse- code practice oscillator. The cir- cuit is an oscillator with its fre- quency variable from 300 Hz to 3 kHz by adjusting tone control potentiometer R3. The sound volume of headphone 7A can be varied with potentiometer R4* and tlie headphones can have any DC resistance from a few ohms up to a lew megohms. The oscillator circuit draws no quiescent current until the nor- mally-open Morse key connects the circuit to the 5- to 15-voIt supply. Figure 8 shows the 555 as the semiconductor device in a sim- ple electronically actuated door buzzer. Pushbutton switch SI connects the 555 to the 9-volt battery, and the output of the IC is coupled to speaker SPKRl through capacitor C4. Capaci- tor Ci produces a low supply- line impedance, ensuring ade- FIG. 5-^MlNIMUM^BACKLASH, DARK- ACTIVATED relay based on the 555. FIG. 6— ALTERNATIVE SENSOR CIR- CUITS for Ftg. 5 provide actuation by light (a), under-temperature (b), and over-tamperatureic), quale on I put drive current to the speaker when SI is closed. The circuit generates a monoto- ne buzzing sound set by poten- tiometer R2. Figure 9 shows the 555 as the semiconductor component in a continuity tester that generates an audibie tone only if the resis- tance between the test probes is less than a few ohms/The cir- cuits operation depends on an output tone that sounds only if the kizshrr (pin 4) is biased positive to about 600 millivolts or greater by sensitivity potenti- ometer R5, Pin 4 is normally pulled to ground by resistor R2, so no tone is heard. For the buzzer in the circuit of Fig, 9 to sound, the two probe tips must touch, connecting R2 to the output of the reference generator formed by resistor R3 and Zener diode Dl through sensit ivity potentiometer R5. Potentiometer R5 must be care- fully adjusted so that a buzzing sound is barely audible. Con- sequently if the resistance be- tween the probe tips exceeds a few ohms when a continuity test is being made, the buzzing tone will not be heard. The cir- cuit draws several milliamperes whenever SI is closed, even if the probe tips are not touching* Figure 10 shows the 555 func- tioning as a signal generator for testing both audio and radio- frequency circuits. The circuit oscillates at a frequency of a few hundred hertz when SI is closed. Its square-wave output is verj^ rich in harmonics, and those can be detected at fre- quencies up to tens of mega- hertz with a radio receiver. The signal level can be varied by ad- justing potentiometer R3. In Fig 1 1 the 555 is the active component of a metronome with a beat rate variable from 30 to 120 beats per minute. The beat rate can be set by adjusting potentiometer R3, and the beat level can be set by adjusting po- tentiometer R4. this circuit is a modified version of the stan- +5VT0+1SV m - — 9 R2 m R3 m TONE 555 .01|iF| R5 RG. 7^0DE-PRACT1CE OSCILLATOR with varrabEe tone and volume. FIG. e^ELECTRONIC DOOR BUZZER based on the 555. FIG, 9— CONTlNUrrY TESTER based on the 555. dard astable multivibrator in which the main timing network Is driven from output pin 3 of the IC. When the output switches high. CI charges rapidly through diode Dl and resistor Rl in series to generate a beat pulse only a few milliseconds long. When the output switches low again. CI discharges through potentiometer R3 and resistor R2 In series to provide an off period of up to two sec- onds (30 beats per minute). The output pulses are fed to speaker SPKRl through leveUcontrol po- tentiometer R4 and buffer tran- sistor QL LED flashers and alarms. Figures 12 to 14 show the 555 in LED flasher applications in which the LEDs have equal on and o/T switching times. With the component values shown, each circuit flashes at a rate of about one flash per second. The circuit in Fig 12 has a sin- gle-ended output. Either a sin- gle LED (or LEDs In series) can be connected between the OLFTPijTpin3andGROu:^Dpin lof the 555, and all LEDs turn on and off together Resistor R3 sets the on current of the LED s* The circuit in Fig, 13 is sim- ilar to that of Fig. 12, but it has a double-ended output connec- tion. The LEDs above pin 3 are FIG, lO^SIGI^AL GENERATOR based on the 555 na 11— METRONOME CIRCUIT based on the 555. I ^3 ED E 3 o' Z 63 I — — m ^ — Li + 5VTO + 15V 75K 555 5k cv -onif .01 0^1- LED2 ^ — RG. 12— LED FLASHER WITH SINGLE- ENDED output 4-5VT0 f15V ^2 i /In FIG, 13— LED FLASHER WITH DOUBLE- ENDED output. volts. The circuit oscillates only when pin 4 is pulled to a positive voUage greater than 600 millivolts. That can be achieved only by turning on QL As one arm of the Wheatstonc bridge, resistors R4 and R5 ap- ply a fixed half'Supply voltage to the emitter ot'QL The photocell and potentiometer form the other arm that applies a light- dependent voltage to the base of transistor QL Under bright light, the pho- tocell offers low resistance. As a result, the base-emitter jiuic- tion of Ql is reverse biased* and the circuit does not oscillate. By contrast, under dark condi- tions> the photocell resistance is high, so Ql and the oscillator are biased on. Normally^ polen- tiometer R2 is adjusted so the 555 is triggered at the desired dark level. The photocell should have a resistance between 470 ohms and 10 kilohms under this condition. The precision gating method described can trigger a variety or555 oscillator circuits to form useful audible alarms and relay drivers. By interchanging the photocell with the potentiome- ter, or replacing the photocell with a thermistor having a negative temperature coeffi- cient, those circuits can be trig- gered by increases or decreases beyond preset values in either light or temperature. Figures 15 to 17 illustrate practical exam- ples of such circuits. Figure 15 shows an automatic heat- or light-actuated relay driver. The circuit works with any 12-volt relay having a coil resistance greater than about 60 ohms. When actuated, the circuit triggers the relay RYl on and off about once per second, A heat-or llglit-activated mo- notone alarm is shown in Fig, 16. When triggered, this circuit +5 TO + 15V FIG, 14— AUTOMATIC (DARK-ACTUATED) LED FLASHER, on when the LEDs below pin 3 are off, and vice versa. Resistor R3 sets the on currents of the lower LED*s, and resistor R4 sets the on currents of the up- per LEDs. Figure 14 shows how to modi- fy the circuit in Fig, 12 for auto- matic dark-actuation. Resistors R3 and R4, photocell Rl, and potentiometer R2 form a light- sensitive Wheatslone bridge that triggers the 555 through bridge balance-detector Ql and the RFiSET pin 4 of the IC, The oscillator is normally dis- abled by resistor R6, which pulls HESET pin 4 close to zero FIG. IS— HEAT- OR LIGHT-ACTUATED relay pulser + 1ZVT0-I-15V C3 1+ 3 " I ± SENSOH cmcun SEE FIG.17 R1 1^ Q1 2N3702 V R3 lOK R2 1.2K CI R4 10QK 6 555 T r SPKRl "1 II ^ R6 R5 02 -t 1H4001 D3 02 211305$ FIG. t&— HEAT- OR LIGHT-ACTUATED medium-power aOO*Hz alarm. R7 BASE m m R5 10K Q1 'base B6 10K 01 BASE FIG, 17— ALTERNATIVE SENSOR ClRCUnTS ior Figs. 14 or IS for actuation by darkness (a), light (b), ynder-temperalure (c), or over-lemperatufe (d). BIfJARY DIVIDER CMOS 14'STAGE (-1^.384) RY1 12V + 12V RG. IB— A 60-MINUTE TIMER based on the 555, generates a buzzing sound at about 800 Hz* Several watts of power are drawn from speaker SPKRl through buffer tran- sistor Q2* The resulting high speaker output current could transfer ripple voltage to the power supply so diode Dl and capacitor C3 protect the circuit from that interference. Diodes D2 and D3 clamp the inductive switching spikes of the speaker protecting Q2 against damage. Alternative sensor circuits thai can automatically activate tiic clrt:uits of either Figs. 15 or 16 arc shown in Fig. 17, If light actuation is desired, the sensor should be a cadmium-sulfide photocclL If the circuit is to be triggered when light level fails to a preset value (dark actuation). the circuit of Fig 17-a should be used. If the circuit is to be trig- gered when the light Intensi^' rises to a preset value (light ac- tuation), the circuit of Fig 17-b should be used. If you want temperature actu- ation, use a thermistor with a negative temperature coeffi- cient as the sensor For under- temperature operation, vise the circuit of Fig. 17'C; for over- tem- perature operation, use the cir- cuit of Fig, 17-d, Regardless of the kind of operation desired, the sensor element must have a resistance value between 470 ohms and 10 kilohms at the de- sired trigger level, Long'period timers A 555 can function as a su- perb manually- triggered relay- driving timer when it is con- nected in the monoslable or pulse-generator mode. In prac- tical applications, such a circuit will not generate accurate tim- ing signals of more than a few minutes because they require an electrolytic capacitor with a high capacitance value. Elee- t ro lytic ca pac i tors typ i ca 1 ty have wide tolerance values ( -50 to + 100%) and large and unpre- dictable leakage currents. If the 555 is to be the active component in long-period timers, the external circuitry must include a capacitor other than an electrolytic. Figure 18 sirows* as a block diagram, the principles behind a design for a 60-minute relay-driving timer. In this case, the 555 is orga- nized in the as table mode, ft has its output connected to the relay driver through a 14-stage bin- ary divider IC- That configura- tion gives an overall division ratio of 16,384. If the output of the 555 is set to zero at the start of an input count, the output will switch high upon receiving the 8192nd input pulse. The circuit will re- main high until the 16.382nd pulse arrives. At that time, the output will switch low again, completing the normal operat- ing sequence. In Fig. 18, the timing se- quence is initialed by closing SI. which connects the supply to the circuit, simultaneously I B2 39K 470K TIME 2 555 6S1 1 C3 ^ • - 4 12K: Q1 ZN37Q2 t6 4070D R3 1MEG D2 1N4001 01 S2 STAflT RY1 12^ 2dn RANGES: 1 ^ 1 TO 10 MIN- 2 = 10 TO 1O0 Mm -12V FIG. 19— TWO-RANGE RELAY OUTPUT TIMER providing Ito 10 minute- and 10- to 100- minute intervals. FIG. 20— EXTRA-LONG PERIOD RELAY OUTPUT TIMER provides 100-minute to 20- hour intervals. TV 4- i ♦ — 4— i ♦ 4 t>2 ]r ' ^ >12D£1 FWsQluta musll +12 vdc IN 1 i tOOOpl V OUT F[G* 3— MINI-CIRCUITS LABS offer a number of ultra low-cost and easy-to-use broad- band VHF UHF amplifiers and hits. This circuit forms an FM booster with a ao-decibel gain and a 1-decit>el noise figure. Input and output tmpedancas are SO ohms. Pre- filtering must t>e used to reject any strong out-of-band signals. DIGITAL VIDEO STABILIZER ELIMI MATES ALL VIDEO COPYQUAHDS While watching rent- al movies, you will notice annoying pe* riod»c color darken* ing. color shift, unwantecf lines, Mashing or jagged edgts^ This is caused by the copy protection jamnning Signals embedded In Ihe video tape, such as Macrovision copy prcteclion, the OlGiTAL VIDEO STABi^ U2ER RJtll COMPLETHLV EUWIMATES AXJl COPY PROTECmCMS AKD JAM^ MING StGNALS AND SRSMQS YOU CRYSTM. WARNING THEDKin'AL WOCO STA- BtuzER IS iNTtNoeo r^ much, you might need to vary the value of Rl to compensate for the dif- ference. The hold module will not put a significant load on a telephone line, so you can add as many of them as you like, r-e Electronics Now will keep you r friend in formed and up-to-date with new ideas and innovations in all areas of electronics technology computers, video, radio, stereo, solid state devices* satellite TV, industrial and medical electronics, communications, robotics, and much, much more. Well provide great plans and printed circuit patterns for great electronic projecLs, In just the last year. Electronics Now has presented amateur 7V equipment, computer peripherals, stereo transmitters, test equipment, speakerphones, robots, audio amplifiers, power inverters, and much more, coming issues, Electronics Now will present ictical. educational, and money-saving Srojects like: an electronic drum, an audio effects generator, communications equipment, a light-beam communicator, a remote car starter, an uninterruptible power supply, and many others! PLUS equipment troubleshooting techniques circuit design reports on new technology and new products equipment test reports in- depth covemge on computers, video, audio, shortwave radio and lots more exciting features and articles. "Basil: siib rale-- 1 yr/$ia97 2yrs/S38,97 Plug a Friend into EkOmncs NOW. and Save 017 A8! Tliis Chnstmas give an ekarifying gift ... plug a Mend into Electronics Now and brighten the whole new year! Whether electronics is your Mend 's livelihood or hobby your gift will illuminate the whole spectrum of electronics throughout the coming year and provide a monthly reminder of your friendship. SAVE SI 7.43* OR EVEN $35,83* For each gift of Electronics Now you give this Christmas, you save a full $17.43* off the newsstand price. And as a gift donor, youYe entitled to start or extend your own subscription at the same Special Holidav Gift Rate^ — you save an additional $17.43*! No need to send money if you preler. we'll hold the bill till January. 1993, Bui you must rush the attached Gift Certificate to us to allow time to process your order and send a handsome gift announcement card, signed with your name, in time for Christmas, So do it now .„ take just a moment to fill in the names of a friend or two and mail the Gift Certificate to us in its attached, postage-paid rep^ envelope. That's all it takes to plug your friends into a whole year of exciting projects and new ideas in Electronics Now! NO-CODE HAM LICENSES ARE HEREf AU About Ham Raditf by Hmry Helms, AA6FW, tells how to get your codefrce ham license and talk to the world. In over 300 pages, you'll kam about: • packet (computer~to-compmer) xzdio * hani television • using ham radio satellites * contacting stations in i'ot^ign countries and many other exciting topics explained in a friendly, humomus style without a lot of math and or technical jiirgon. if you've bccii wanting a ham license, this is tlie tvook you^ve been waidng forf Only SI 9.95 at kxikstores and radio tx^uipment dealers. Or order direct from HighTextl Add 53 jihipping {S4 to Canacki, $5 elsewhere). CA please add sales tax* U.S* funds only pleuKen HighTcxt pubncilkoni Inc. 7128 Miramar Rd. Suiic 15L San Diego, CA92l2i Try the Bectnmics bulletin board system (RE-BBS) 516"293'2283 The more you use it the tnare useful It becomes. We support 12Q0 and 2Am baud operation. Parameters: 8H1 (8 data hilt, no parity, 1 stop tiil) or 7E1 (7 data bits, even paritVp 1 stop bit). Aiid yourself to our user files to increase your access. Communicate witti other R-E readers. Leave your comments on H-B with the SYSOP. RE-BBS 516-293-2283 UNIVERSAL REMOTE continued from page 56 IC2, an 87C64 8K x 8 CMOS EPROM, which contains the machine language instructions for all functions provided by the remote-control system. The 87C64 IS identical to the indus- try-standard 27C64. except that the 87C64 contains an in- ternal address latch and the 27C64 part does not. For those interested in programming the EPROM, there is a modification you can make to the program* mer we ran in November 199 L Send a self-addressed stamped envelope to the author for de- tails (see the parts list}. In nor- mal use of the 1NS8048L, address lines ao-a? need a sepa- rate 74LS373 address latch be- cause the lower eight data and address lines are multiplexed between address and data by the INS8048L processor. Be- cause power consumption must be kept to a minimum, and space is at a premium, eliminat- ing a 74LS373 address latch by using the built-in function of the 87C64 works in our favor In botli circuits, capacitors CI and C2 are used by the built- in oscillator of fCL A 6-MHz crystal (XTALl) ensures high accuracy for timing routines, and it provides the basis for the 40-kHz carrier on the transmit- ter module. All 0. 1 |jlF capacitors are standard TTL noise-bypass components, while 08, a 10 mi- crofarad elect rol>tic, minimizes voltage drop at the battery ter- minals. Capacitor 03 is used to reset the processor. In the transmitter, Rl limits current and. along with Ql. al- lows a high-current 40-kHz pulse to be applied to the IR LEDs. Resistors R3 and R4 pro- vide pull-up for address lines ai i and A12, On the transmitter, in- stall jumpers All and A12. The system is designed to op- erate from a +6-'Volt DC supply Diode Dl drops the + 6-volts DC down to around +5.3 volts. The system works fine without the diode, but its best to leave it in the circuit because voltages above -t- 5 volts can lower the life expectancy of semiconductors. RG. 10— THE PROTOTYPE TRANSMf^ TER is housed in a plastic case with a stngle-sfded, copper-clad FC^board blank machined as its top panel. Buildiiig the system As mentioned before, the transmitter and the receiver are both on the same PC board. You can use the supplied foil pat- terns to make your owm (you 11 need at least two), or they are available from the source given in the Parts List, The transmit- ter and receiv^er boards are iden- tical except for a few compo- nents. Figure 9 shows the parts- placement diagram for both boards. Follow the parts list for the board you are building, and install only the parts in that list. Check off each part as you in- stall it to avoid confusing the two boards. Build the transmit- ter first, and put it aside when It is done. Install the capacitors, paying special attention to their polar- ities. Be sure to install junipers at the am ai2 locations for the transmitter only. It's advisable to use sockets in this project. Install the IR LEDs and RL Mount them in any position as long as they can able to radiate IR freely. Gate-pull-up resistor R2 is optional. Once you are satisfied that all your work is correct, attach the 16-key keypad with a piece of ribbon cable. Cut a piece of cop- per-clad perforated con- struction board with holes 0-1- inch on cen ters to the same size as the keypad. Mount it over the keypad pins and solder the per- forated construction board to the keypad pins. This will make it easier to solder and mount the keypad. A functioning transmitter FtG. 11— THE RECEJVER BOARD can be mounted on the project you are adapting it to. You can attach the GPHJ52X IR module directly to the PC board as shown here, or run wires to it off-board. can be tested with the GP1U52X infrared detector module from the receiver You 11 also need a logic probe or scope. Attach a + 5-volt DC supply to the GP1U52X (see Fig. 9 for pinout information). Apply power to your probe or scope, which should be connected to the out- put pin of the IR detector. Apply power to the transmitter and press any key. You should see a change in the scope pat term from the output pin of the IR module if the transmitter is op- eraling properly Install the transmitter in a suitable enclosure. A red arcylic lens will improve the ap- pearance of the remote control^ but it is not a requirement. The layout of the components on the circuit board is not critical The prototype is housed in a plastic case with a singic-sided copper* ciad PC-board blank machined as the top panel (the copper side is installed on the inside of the case). Rectangular openings were cut in the blank for mount- ing the power switch and key- pad. Brass strips, soldered from the copper on the top panel to the copper on the periboard in- stalled on the keypad, are used lo mount the keyboard to the top panel The prototype has a 6-voU "J"- type battery because of its size and shape. However, any -i-6-volt DC power source will be satisfactory for this proj- ect. The prototype transmitter is shown in Fig. 10. Now assemble the receiver In- stall the parts indicated in the parts list (or the receiver and the partS'piacement diagram. At- tach the GP1U52X to the PC board or optionally run wires to it off-board. Be sure to ground the meial case of the module. Install jumper blocks at the ah and A12 locations as shown in Fig. 11. The figure shows the completed module. Test the receiver module in the switch mode (jumper ah and Ai2 on the receiver). With a logic probe to monitor no (pin 27 of ICl on the receiver), you should be able to toggle mo by pressing add or dfa. followed by a ]. ADu 1 should take pio high while iiEL I returns Pio to low. If this function works, the rest of the applications will also oper- ate properly r-e INTRODUCTORY OFFER Greniiiite Coin Jewelry Attracts attention! Breath-taking designs! Exquisite Jewel n' iimrle imm govcnmieiit'iiiiiilccl criitis. Each Ltnin>cnfJunt iiHS i(s backj^roimti cut awayljy himtl with saws as thin us 16 thou- saiidUis of an jucli leavitiiJ the coin's figure Iloatijiir in£>idc Us i im. Each haiid-crartcfl coin is clciincd and polish ctl before 24 K gold and silver is added urUuUy to selected |>oiliotis cjfthe coinj^. 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Enrol [ mo as a member of the Electronic b Book Club according to the terms ou I lined in this sd. It not satisfied l may raturn tire txraks within 10 di^ys lor a full return and rrty momtwrshjp wiEl be cancelled. A shjppmg/hand^ing €tiarg@ h tax will tue add- ed to aJ I orders FflEE BOOK ^ 0i to iiad U a U« BQL J lU IN nt sat 2 bOK S^ng^ □ Check or money order enclosed payable to: McGraw-KiH, Inc. □ PFease charga my XI VtSA □ MasterCard □ American Ejc press Wame _ pavmen Exp. Date . _Sigfv , City Address State/Zip ^.—^ ■n US Ml *C^ii «Mw p n l w ii» i l > < Bpt d h^ i iMkM i Boca P«t^4d) HQM (luppmg & t&ttis^ A^i^dcwttowlwSt irw US Phone , CO 83 ITotir mort temptmtm mnd €Qmpreheitsiw MifUtte for - tJie iiiwsi electroffi'cs hookB DRAWING BOARD Let's buMd our own video scrambler! ROBERT GRGSSBLATT 84 We haven't seen very much circuitry yet on our journey through videoland. Thats to be expected, though, because video is a subject whose theory you should understand before you start building hardware. As Ive already written countless tinnes before, a video signal (shown in Fig. 1) is very complex, with many separate com- ponents that are mathematically re- lated to one another. If you look at a video signal on an oscilloscope > it will appear more or less like the lower waveform in Frg, 1. The most important component of the waveform is the horizontal sync pulse; if you do away with it. the TV won^t have any reference for the beginning ofa video line, and the resulting image v^ll be misaligned verticaNy. (See our September col* umn for more on the subject.) The color will also be messed up — with* out the horizontal sync pulse, the TV won't be able to find the color- burst signal. Altering horizontal synch Suppressing the horizontal sync is a simple* inexpensive, and rela- lively safe way to keep "un- authorized" viewers from receiving a coherent signal. So, to under- stand better how scrambling works, let's build a circuit that can alter the horizontal sync. Because we're dealing with com- posite video, and we intend to play games with horizontal sync, the first thing we have to do is isolate the sync from the rest of the signal. That isn't very difficult — every TV in the universe can do it. Most modem TV's either use a discreet sync sep- arator chip or have the needed cir- cuitry buried in the innards of some custom silicon. That makes things cheaper for TV manufacturers, but it's murder for people like us who FtG, 1— A VIDEO SIGNAL is normally 1-volt peak-to-peak, but after buffering, the relative voltage level of the signal is rafsed by 0.5 volts. Then, the only part of the pulled*up video signal that falls below the TTL threshotd of 0.8 volts is the horizontal sync signal. RG, 2— WHEN 81 PULLS PIN 3 of 1C2 high, the video signal loses Us sync. When SI pulls pin 3 low, sync is restored. have a hard time buying the chip in single quantities. Fortunately, theres always more than oneway to get the job done. In this case, it means looking at the voltage definitions inherent in the video signal, and seeing what we can do with them. Standard video has very stnct voltage divisions: ev- erything above 0.3 volts is picture information and everything below 0.3 volts has to be a control signal. (We haven*t talked about vertical sync yet* but youMI find that the same voltage levels apply to it, too.) When you have a 5-volt supply and a signal voltage with a O.S-volt knee, you should immediately think about standard TTL logic. In that family everything below 0.8 volts is low, which is exactly what we're looking for That nnight not be imme- diatefy obvious, so let s go through it. A video signal is l-volt peak-to- peak but* by buffering it. the relative voltage level of the signal is raised by 0.5 volts. So, instead of ranging from 0 to t volt* Ihe signal ranges from aboul 0.5 to t.5 votls. The translated level of the conttDl/pic- turn voltage point is now about 1 volt (see the upper waveform in Fig. 1). You can see that the only part of the pulled-yp video signal that falls be- low the TTL threshold of 0.8 volts is the horizontal sync signal. The bottom line here is that we can build a sync separator from a standard TTL gate — in this case well use a 7486 exclusive-or Cxor) gate. All we have to do. as shown in Fig. 2, is feed the translated and buffered video from Ql to one input of the gate, and tie the other input of the gate high. (Ql is part of the buffer that v/e put together in Sep- tember to keep your video gener- ator or VCR from being damaged J Suppression circuit If you work out the truth table for yourself, you'll see that the only time the output of the gate is high is during horizontal sync. The output at pin 3 of the 7486 is a TTLIevel inverted version of the horizontal sync. That output is fed to another xOR gate, which inverts the signal and gives us a negative-going sync signal. Ability to provide both a positive and negative sync signal is the key attribute of the suppression circuit. We want to build a switch that passes video during the picture portion of the signal and be able to alter the signal during the horizontal sync period. That s what the rBst of the circuit does. The first part of the circuit Is a picture/sync separator, and the last part is a picture/sync combiner — sort of. Even though we can put the sync back in, also h^/e the op* tion of sticking rn just about anything else we want in place of horizontal sync. The combiner uses half of a 4066 analog switch as a double*pole. double-throw switch. (The analog switch contacts close when the control voltage is high.) The outputs of the switch (pins 1 and A) are com- bined, but because the control lines of the switches (pins 13 and 5) are connected to mirror images of the horizontal sync signal, we can route the picture portion of the video sig- nal to the switch output when sync is low (pin 6 of the 7486) and route horizontal sync to the switch output when sync is high Cpin 3 of the 7486). The single-pole, single^throw svi^rtch CSl) controls the input to pin 3 of the 4066, While it's neat to see the effect Si has on the video signal when seen on an oscilloscope, this is one of those cases when you're better off seeing the effect on a TV. Whenever S1 pulls pin 3 of the 4066 high (anything above the ex- pected sync level), the video signal loses its sync and the picture on the TV goes totally haywire. If you*ve seen scrambled pictures before. you*ll recognize it immediately The left side of the picture will be on the right half of the screen, the right side of the picture be on the left half Down the middle of the screen will be the horizontal inten/al. When Si pulls pin 3 low. sync is restored and so is the TV picture. Putting It together We are not ready to go into the details of the scramblrng business just yet, though. A successful scrambler not only has to take the video apart, but it also has to put it back together again. That is quite a bit more difficult. There has to be a way to encode the video signal so that the horizontal sync signal is re- stored at the right time, and for the right length of time. One outdated way that this can be accomplished is to bury the information in the 31.5-kH2 audio subcarrier That's not so surprising when you realize that half that frequency is 15.75 kHz — exactly the same as the scan rate of the video lines on a standard color TV. There s not much point in going through all the gory details of recovering suppressed- sync video since it's about as useful as presenting a full tutorial on repair- ing telegraph lines. Since suppressed^sync scram- bling was figured out by signal pi- rates about five minutes after it appeared, the people in the televi- sion signal scrambling business moved on to more complex meth- ods of screwing up the video signal The most common method now in use combines a variation on the suppressed-sync method, inverting the video, and performing a lot of weird other stuff. r-e Learn VCR repair at home! MAKE GOOD MONEY IN YOUR OWN FULL- OR PARTTIME JOB Professional- level home study course. Yoo will master easy-to- learn. high-profit repairs with- out investing in high-tech instruments or a costly workshop. Want more independence and higher income? Send or call toda^! 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Now you can subscribe to the magazine that plugs you into \hii exciting wmM of electronics. VVith e\^n' issm o( Popular Electronics you'll find a wide variety of electronics projects wu can build and enjoy. Popular Electronics brings you informative new product and literature listings, feature articles on test equipment and tools— all designed to keep you tuned in to tlie latest devel- opments in electronics. So if you love to build fascinating electronics, just fill out the subscription form below to sub- scribe to Popular Electronics - . . It's a power-house of fun for tbe electronics enthusiast. EXCITING MONTHLY FEATURES UKE: □ CONSTRUCTION-Building projects from crystal sets to TL^kt. Ironic roulette Q FEATURES— Educational training on digital uleclronics, Ohms l-aw. Antennas, Communicalions, Antique Radio. Simplified Theory □ HANDS-ON-REPORTS^ User test comments on new and unusual consumer products I J SPECIAL COLUMNS- Think Unk, Circuit Circus, Com- puter Bits. 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Then buUd your own using our easy-to-duplicale^ Jo*- cost de^igFts FOR FASTER SERVICE CALL TODAY 1-800-827-0383 (7:30AM-8:30PM) EASTERN STANDARD TIME Po pular Electronics subscription order form AREL2 P.O. Box 338. Mt. Morris IL. 61054 YES! I \vant to subscribe to Popular Blectrt)nics for I 1' ul] year (12 Issues) for only $18.05. That'.^ a savings of $23.05 off the newstand price, (liask Subscription FUte— 1 yr'/$21.95) Q Pay in e ni E nc losed Q Bil 1 me I ater Please chaiige my: Q Visa □Mastercard Acct. tf l 1 I Sif?nature Exp, Date PLEASE PRINT BELOW: STATE ZIP cm' Allow 6 lo 8 weeks fordi-iii-cry \4 fifjt i5&ut-. VS. Funds only. SUPER STROBE continued from page 37 countering some trouble with false triggering by the sound of the shutter opening, we put the microphone on a tree limb to get il closer to the splash while being careful not to get it in the frame. \Vc covered it with a plas- tic bag to keep it dry. The sknsi TivrT>' ended up being set about mid-range. Figure 15 shows one of our efforts at catching a stone skipping across water Ea:ploding capacitors When the editor speculated on what an exploding capacitor might look like, we decided to find out.,, despite our better judgment. Do not try this at home! The fumes that are gen- erated are noxious and toxic, A fire extinguisher, proper safety clothing and eye-protecting goggles arc essential precau- tions. We learned that there's not much more to be seen of an ex- ploding capacitor w^ith the strobe than without it. How- ever, the picture that we chose to illustrate what happened (Fig, 16) is slightly more dra- matic because the smoke, which would not have shown up otherwise, was illuminated by the strobe. Tb try to get a more interesting shot, we even piled a group of electronic components on top of the cap thinking we could get a picture of them fly- ing into the air That might have worked eventually* but when our eyes started to water from the smoke we decided to take a break, and we just never got back to this experiment. Your tnxn These photos and the expla- nations of how they were set up and shot sliould getyou started. The only rule is that there are no rules; you really get to make them up as you go along. We have a standing bet about how much a golf l^all deforms when it's hit. If you find out before we do, let us know. Electronics Now will be happy publish the tiest Freeze Frame pictures we receive, mE II II I TWO TRAMSMITTEBS IH ONE! 5 MINUTE ASSEMBLY! MONEYBACK GUARANTEE! New law Enforcement grade device on a single chip is the most sensitive, powerful, stable room transmitter you can buy. Uses any 3V-12V battery. 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Call for catalog and price list. Spe- cial combos available. We ship COD. Quan- llly discounts. Call for pricing on other products. Dealers wanted. FREE CATALOG. We stand behind our products where others fail. One year warranty. ACE PRODUCTS, 1-800-2340726. CmCLE 75 ON FREE INFORMATION CARD CALL NOW AND RESERVE YOUR SPACE • 6 X rate S940.00 per each insertion. • Fast reader service cycle. • Short lead time for the placement of ads. • We typeset and layout the ad at no additional charge. Call 516-293-3000 to reserve space. Ask for Arline Fishman. Limiled number of pages available. Mail materials to: mini- ADS. ELECTRONICS NOW, 500-6 Bi -County Blvd., Farrr^ingdale. NY 11735. FAX: 516-293-3115 TUNABLE 50dB NOTCH RLTERS— for TV. Can be tuned precisely to required frequency. Model 23H-Chs 2-3 (50-66 UtM} Model 46FM-Ch's 4-8 plus FM (66-108 Uhz} Model 713-Ch"s 7-13 074-216 Mhz) Model 1417*Ch's 14-17 (120*144 Mhz) Model ta22*Ch's 18-22 (144*174 Mhz) S30 each, rncfudes shipping. 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The next step for IBM should have been 32 megabits, but that's already old hat. As has been widely reported. IBM is now cooperating with Siemens to de- velop 64-megabit DRAM More recently. Big Blue an- nounced an even more ambitious intemalional developfrient effort: it will now pool its resources with those of both Siemens and Toshiba to produce 256-megabit DRAM s — bypassing 128 megabits — built with quarter-micron trace widths. It would take 400 of these lines to equal the width of a human hairf Think about it. When many users are still moving up to 4 -megabit DRAMs, nine of those babies to be developed would provide 256 mega 6yfes of memory! That is from 16 to 64 times better than the memory capacity that today's higher-end Windows-compatible workstations limp along on. Now consider a com- bination of a bank of 64-megabit DRAM s with an Intel P5 CPU and an XGA/DVl graphics subsystem, all on a single chunk of silicon. Soon the sehaL parallel and network port connectors of a computer will take up more space than the electronics! Imagine the possibilities. We'll buy "dumb" highly stylistic display IntoPublisher - C1MISCDAT\ADDnB00K\TEST.PAt - {Work Tabic] Pf .... r- rrr mmm mrr larrfr r I Lotus Dcvciopmem Ootpomion 1 FIG. 1— DATABASE PUBLISHING is a snap with InfoPublisher Extract me data from one or several joined d8ASE, Paradox, Oracle, or SOL Server files, select desired rows and columns^ apply formatting, and then export the data to popular DOS and Windows word processors and desktop publishing programs- units with keyboard and stylus in* puts CDUKSrs)- Each DUKSI will have a socket that accepts a com- plete computer^on-a-chip. in a multt- tude of styles . They'll give customized performance for dif- ferent users, and permit easy up- grades. DUKSIs will be sold retail tike Ralph Lauren brand-name clothes in a variety of styles to engi- neers, technicians, executives, stu- dents, and even homemakers. Neither the DUKSI nor the com- puter module will cost much to make: they'll be produced by robots and, unless there are drastic changes in global business condi- tions, they won t be nnade in the good old U.S of A. Large profits will be generated from designing, sell- ing, and reselling highly stylized, fashion-conscious DUKSIs. People would buy new DUKSI s from time to time, not for technical upgrades, but for personal satisfaction — ^like buying new clothes. The DUKSI will be part of every schoolkids lunch box, every man- ager's briefcase* every doctors bag, and every technicfan's tool kit. Within ten years, they'll connect without wires to all major telecom* munications services and provide on-demand connectivity to an> node on the networks. Within twen- ty years, th^ could connect to al compatible electronic devices- telephone, fax, copier, television, oi stereo. If Microsoft has its way, Windows software will be an integrated part of this encn^aching World Net. Receni reports suggest that Microsoft is actively investigating ways to adapt Windows for other environments Those could include envisioned de vices called portable digital as sistants (PDA's) and next-genera tion video games (the 'Wintendo' discussed here last time). The> might also include office machines (faxes, photocopiers, and tele- phones), and personal tefecom- munications, which depend on computers to control access to news, sports, entertainment, and business information. A chip in the hand Tliere s good and bad news about Intel's forthcoming P5 micro- processor, sometimes (er- roneously) called the 586. The good news is that public hands-on dem- onstrations (including those for the press) prove \i to be screaming fast. It makes smooth-scrolling 3-D ani- mation possible, and it allows text scrolling under Windows almost as fast as character-based text on a 286 under DOS. The bad news is that introduction of the chip has been delayed until early 1993. Intel apparently wants to make sure that there are no bugs in the P5 and that the company can meet high-volume production de- mand. That bad news is tempered by the possibility that its later intro- duction is likely to spur further price cutting in the active 486 micro- processor market. As for its departure from its usual practice in naming microproces- sors. Intel appears to be intent on distancing itself from the chip-clone companies (AMD. Chips & Tech- nologies. Cyrix, NexGen. et alX It is holding an internal contest to de- velop a new name that does not contain the "86" moniker. It ap- pears that marketing has become more important in selling micnDpro- cessors than we would have thought possible. Intel has signed a deal with VLSI Technology under which VLSI gains rights to x86 technology. VLSI is expected to put that technology to work in building new devices that will be customized for handheld and other portable computers. However one recent study shows that the market for handheld and pen/tablet based PC's will not take off as rapidly as was initially ex- pected. According to that study, laptops will gradually drop out of sight between now and 1996, Note- books will pick up most of the slack and provide the largest share of new growth- Combination stylus/key- board units are also expected to show significant growth. Pure pen- based systems will just be getting off the ground by then. Product watch InfoPublisher, an innovative niche product, functions as an interface between a database and a publish- ing system. It allows you to extract the information you need and pub- lish it in a form that makes sense. On the database end. InfoPublisher can read dBASE. 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SLC, Ulafi 84152-1164 60 5OL0ERLESS Breadboard Projecls in two oasy io-fead pockei books. Complete with drouii descriptions, schematics, parts Eay^uis. cofnpo- neni hstinqs, etc. Both books iBPWl & BP113) only Si 1 .90 plus S3.50 tor shipping USA and Can- ada only US funds, ETT, INC,, PO Box 240. Mas- sapoqua Park, NY 11762-0240, CELLULAR backers bible Theory — hacks — modrticalhons — S53 95 TELECODE. PO Box 6426-RE. Yuma. A2 65366-6426 VJOEOCIPHER II satellite' scanner cadie ama- leur/cellulari repair manuals, modification books, software Catalog — S3 00 TELECODE. PO Box 6426 RE. Yuma. A2 65366-6426 BUILD 0-50 volt regiiatect dua^ trac>(ing pow^r supply. Complete schematics and mst ructions. $5,95. SMS ENGINEERING, RE 5932 W^st Baft Road, Suite Otoe. Glendale. AZ 85308 PROTOTYPING PC boards? Fast ar^f easy from artwork to eiched board in 30 nvnutes or less. Complete step by step plans arvj samples! S6.5D check or money order lo E.G,G., PO Box 11390. Bradonion, FL 342B2. 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At VlXt cuffmi. refill jiti:^. ijtodci, canKinuiiy, inii irjuilnor cunmt gitn {mfxpi M39O0) * MjjiujI ringing w/oveHoaid pfoici.ti»n * Comd wiilh pr(»bc», lultnici, cive Jii J rtuniut NR27a86&NR27ISS(nilji * Aba maHim ficqucncv and upumiKr KR271U M3fl00 NR2707e M36t0 NR27t40 M3900 !^il27(l8« M3650 KR27IS8 \M'NR2 onterii^ Noffofiol ofid Intel Dotabooks MI335&6 T^IS;%4__S.95 TXt$27iG_^5.95 I70M ^.95 ^3.95 «4.25 27C;i6.«...«...4.25 27J2 „ 4.95 27jZA 20.,....4.49 ^7^2A^^ — L95 2^C32 ^4.95 276420 4.95 2 TM -2^^3,75 2^64 A 20 1,75 NR39829 Nft39«45 N109S53 NR3W2 NR39925 NM9933 NfU996B NR399&4 NR39677 N 1139685 NR40070 NR40037 NR40(H5 KR40061 2-64A.2S__S3.49 I7Cfr*l5-_^9S I7£>i.25^«^49 ITCYri^-t 2.95 2712aUTP..^2.49 2^t2SJo 7.9S 2^128 2*1 «..-7.75 27I2KA 20,.H.4.75 27I2KA'2S_3.75 2^C12« n,...5.75 2^C12S-2S_7.95 272W^TP__4.I9 272 IS — 5,49 27256-20 — 5J9 27256-25^ — Am NR&59C14 NiU97l4 Mli9722 NIU973I NR401M NR4015O NR4016B NR39773 NlU97«i Niy*;790 NBJ9K02 Niy9 27fl&45 Dr«k« DiEibeQk $ t9.94 SjdKHiil Lope U nas {ynrwa DitibooJt ^11*9$ Drvtcci Dacabook >.1U95 Niitkmal LS/S/TTl Dat*bot»!< 14 JS Irtirl Memary Diuboot Intd Embedded C!ont roller FrDCnvori AJ^Uomal ditihwh iPidaklff «14.95 A*R.T. iPROM Prog ram me r ■ rro|;rami t\\ currirnE EPRUMa h ikc 27 Id to 27512 Hn$!c plm tbf X2Wi4 FimOM - RS232pon Ptn Kp. PraJuct So. Ogcri|ttMia Price 1*riif;rjinEticr $ 179-95 UVP EPROM Erwe ' t)E4 ema 8 chipt mT>' 21 minutes • D£ I Cf^uw profile 10 1 4 -pii^ low proftlc A t I b-pin. liiw prtiillc «12 24^ pin \aw pixitilc «]9 iS-pin lew pruAlc .22 4(}-pu) law pmfilc .201 Connectors ISRI5n4 DB25P Mal^, 25 pin ««,4j65 NRI5I57 DB25S Fcmair, 25 pm.-. .75 NRI5085 DB25M Hood.. „*, 39 NRI5106 D&25MH Meul HDod.,....43S Mis€elloneous Components* Tkwtsistors And Diodes I!uL^Di PlS!StjJl£LKlIi_ Memory NR4lj9a NR42Z51 NR4I52J NR4I718 NR41749 ^IIDOOp-flO 4l25fiA?li40 ■lllOOOA'JA^O 42I€C0A9&'80 UDs 256K Dir 1MB PIP 2^K SIMM IMBSIPP IMS SIMM 12Dm SOns .. -..5.99 i95 -5i95 Pan No. IWnct No. Dcttriptioft C|j££ M04761 XC556G Ti 3/4. (g^een) S.I6 NRJ4796 XC556R Tl 3'4 Jredl .11 NR54a25 XC:556Y Tl V^, udlti^ j .16 Linear ICs" Eiarfy tl Nfti 41 79 «3 71 SI 22 2S 67 39 31 57 ai 78 30 »5 &2 TX0«2CP., Ii43m». LM324N « LM339N ^ NE555V, U^t556N_ lAf74lOf« IAU458N_ LMt4g9K. — *.59 59 35 — 1.09 .45 --29 .49 .49 ,.29 -39 ..45 ..45 Pun pTMttta J5a ULi^2003A«,««.....«,....,.^ .69 IAU*>14N 2.49 NB5532 ..1.19 7S051 . -45 7S12T 45 SU2B628 SR28644 KR35991 NK3S236 NR.»6i26 NR3a359 NR36290 SRi*42i NRi603a PN 2222 PN2V07 IN40O4 2N2222A IN4735 2M39CM 1N751 2N440] lN4t4S 2.^rJ055 DfKTtptwti Prm TO '92 cue -..««S.1 2 T0.92cwc« 12 00-41 10 TO-lfi™. ,25 D0-4tcaiie 25 TO'92 awe .12 □0 35 .15 T092ci»c D035 CAM , j07 70-5 131C j69 Switches PfodiKi Nfa]936 JMri23 SPOT. cMi'S3bS020 [Gnp«i9 Tcduikd Suppon: 1-S0OS31-00S4 BBS Support; 415*637-9025 For Inicmaiionil Sdcs, Customer Scnicc, Crcdii Dqwunent and aU other inquiries: Call 41 5*592*8097 bcnvceo 7AM-5PM P.S.T. CA Rfxidri^ti p^cusr jdnJ j^plifable uIa u\, Shipping, hjuhiting and UiB^once ifc adJititmil- rcfmt; Piiccii iub|nt to chjngr without rtotkv. Complete li» of tenat/wafnnoei. U miUbIc aRCLE 1 14 ON mEE EMFORMATIOH CARO Cable TV DESCRAMBLERS >■ At Moft Complett line of Desiramblers > Friendly, professional service >FREE Catalog □ l_-80Q-228-7404 ^ ^ Go to the Source ^ NU-JEK ELECTRONICS 3250 Hatcfi RO Cmdat Pwgk T1XA5 78&I3 i I s 8 e IS [0 94 FOR SALE TUBES: "oldeai," "lalcst/" Paris and scho- matics SA3E (or lists STEINMETZ, 7519 Maple wood Ave., Hammond, IN 46324. RESTRICTED locfinical information: Elecfronic survefllanco, schomattcs. focksmiihrng, covert sciences, hacking^ eic Huge selcclion. Free brochures, MENTQR-Z, Drawer 1549, As bury Park. IsU 077ia. TUBES, Tmn.up 10 90^* qM. SASE. K1R0Y. 298 West Carmel Dnve. Carmen. \H 46032. T^V. notdi f jHers, ehOfM) recofCti^g equcpment, bm- ^tum $1.00 MICRO THinc, Box 63 6025. Mar^ gate.R-33063 i 305) 752-9202. SPEJ^KER repair A3i makes — rtKideEs. SrarDO S ATLANTA AUDiO LABS, 1 (6Q0J 568'697T ENGINEERING software and hardware, PC MSDOS. Circuit design and drawing. PCB layout, FFT analysis, mathematics, circuit analysis, etc. DataacQuisition. generation, I/O PCB's< etc. Call or write for free catalog. (614) 491-0832. BSOFT SOFTWARE. INC, 444 Colton Rd.. Columbus, OH 43207. CABLE TV Eqalpmeitt Mosi lype available. Special: Oak M35B 539.95. No catalog. COD or- d^ only. 1 (600) i22>995S. iOC52-Ba5ic mkcroconrrolier board. Basic inter* preler,33K RAM. 16K Eprom, Eprom pfogranvner. RS^2, expartsion connector Bare board iwim manual, scheitiaijcs $22. 9&. SCC52'Bastc micio- pracessor chip $25.95 Assembled ar^ tested S124^ PROIjOQIC designs. PO Box 19026. Ealtimofg. MP 2T2Q4. J ERR OLD, Tocom «nd Zemh ^^tesV" chips. Fylty activates unit. £50.00. Cftble de- scramblers from S40.00. Orders 1 (800) 452^7090. Infornnallon (310) &67j)0S1. TOCOM-Jerrold Impulse-Scientific Atlanta Converters, two year warranties. aJ&o lest mod- ules for your convortors. Conlad NATIONAL CA* BLE, (219) 935-4128 luil doiails. CABLE doscramblersi Build your own do- scram bier for less than S 12.00 in seven easy steps. CompJelo instructions $10. 00. Radio Shack parts fist ar^J free descrambltng moihods lhat cost nothing lo try mcJuded HARRYWHITE, PO Bojf 1790. Baytown, TX 77520. PROTECT voursetl and equipment from electrical stiocits Complete unit S9B.95. SAFETY-UN- LlMtTEO. 1743 Baldwin Road, Yofkiown. NY lOS9fl. SHS5,00. FREE CATALOG FAMOUS ^^FIRESHK^' BRAND CB ANTENNAS AND ACCESSORIES, QUALITY PHODUCTS FOB THE SERIOUS CB'er. SINCE 1962 FIRESTIK ANTENNA COMPANY 2614 EAST ADAMS PHOENIX, ARIZONA 85034 CONVERTERS — Doscramblers, Jerrold Star* com e. S.A. 85XX. Oak RTC, Tocom VIP, Zenith, all bullet prool. lowest prices, best warranty, CCD. orders welcome, ULTIMATE CABLE PRODUCTS, (702) 646-6952. PCB: Printed orcuit t>oard art work made lo your specifications plotted on transparency Muiti layer and surface componont capable Circuil tioatd production avarlat>le, tree estimate send scho- matic to NEQRON ENGINEERING. 1S9 Garfieid Pl at^. Brooklyn, NY 11215 Fa;< (718) 7&8-4Q2B PLATED thru ho!c pnnted a rousts, S25.00 mani- mum. Fast turnaround Foi more mfonnaiion call A.R CmCUrrS, (403) 25O-3406 or BBS {403) 291-9342 (S.n^ IS It true.. Jeeps for SW.OO through the U.S. gov t? Call fOf fads ^504) 649-5745 ext. 3-5192 CABLE TV DESCRAMBLERS iir CONVERTERS ★ and ACCESSORIES. I DOir TRENT! PANASONIC. JERROLD, OAK. PIONEER. SCIENTIFIC ATLANTA AND WORE LWVEST PRICES FHEE CATALOG CABLE READY COMPANY (800)2344006 OESGRAMBLERS-Converters, 1 piece com- bos. 8SXX DPV-S S179.00, Tocom VIP S25O,00. Zanllh $199,00, full warranty, bullet proof. S.A-C> 1 (800} 622'3799> CABLE converters. Oak RTC-56 S99.00. Jerrold DPV-5 S189.00. Zenith 1086 $225.00, Tocom* VIP S250.00, S.A. 65 — $179.00, Hamlin CRX'66003M S99.00, Sytvania 4040 010 $79 00, all makes in stock, luily bulie; proof. MOUNT HOOD ELECTRONICS i?06) 260-0107 BULLET prool descramblers-converters, all makes, best pnces. examples Star com 6 $179.tX). Oak RTC-56 Si 09 .00 Tocoms. Zenith. Soentflic Atlanta, m stock, lull warranty. KABLE KONNEC- T10N (702^ 433-6959. JERROLD Impulse digital converter. Upgrade your 400 450 untl to this latest system. (312) 896-5819. TEST equipment pre-^jwned ai atfonjahle pfices. Signal oeFieraiors Irom S50.00, os* aSbscxipes fmm iSO 00 Olhef ei] Q \ I hVi 1 H L CO M Ji CiLi [I SYSI r M S 9 pc^iaxfiiu? cutMOCOt PHDtiiu.ui^7 uiam ■ttn am i^mMMm tarn tm REMOVE LEAD VOCALS From B^fia thi« hit whicii nmovt vocftils horn standard utoiiNi t CD*!, tapes Df FlM bfoidcjtf along wtUt the b«c» sens fit tilt liiXcbi copy of tli« Jte Ccr.£UEier Inforraatlon C«ialag. H imM more ttiAn 200 £r«« cr lov-ccst govnrEiiniont publJcations Sond your name and addre^ to: CoxLEumer Inf onutloii Gimtsr I>ttp«ttm«iit TMLf ViamWOt Coloxmdo 910O9 REACH FOR THE POWER. TEACH. No other pfofession has this power. The power to wake up young minds, ihs power to wake up the world. Teochjers hove ttrat power Reach for it Teach For jnforrrtation call: 1-800-45-TEACH, Recruiting New Teachers, Inc. Covrttoim $*n/ic& - DiacotMii Mam - Fmt Shipfimff nLLaEaROflicscoRP. Mall Ofder Eloctronlc Parts And Sup pities R O. Box 567 - Van Nays, CA 9 1408 LASER POWER SUPPLY Epoory encspi utaled pamttr vjppfy (of up to 2 mW luwi. 4 1/r X 1 1/r X t 7/ir. Inpot: 9 Vd€ @ 1 trrp. Oulpul tUrling wHo^s: 7 to a kV. Opwatng vo.'tage: 1.1 to 13 kV 0.250 qucK oofuwd tAfrrimli for ou^Hft DOdvd WW9 iof inpul, CATiLPS^I t35.00«h RECHARGEABLE Gell Cell Batteries L U a a i bb in any po»^iori. 6 VOLTS @ 1 .2 AMP/HOURS r X r high. CATtOC^tS 12 VOLTS ^^ AUP/HOURS Two G voN 10 AA^ 01 a iin{fla 12 voti sfis; 6" K 3W X 3.75" CAT«GC-121CI $35,00 9«eh /MOTOR SP£EZ? CONTROL AND TIMER With a mifiimum of extflrnnl wirmg. Xbh PC boani wil eonlrol th«spa«d and duralon d a 120 Vk •divMtd, maior vittcparaia for 10. «r4a iTifM«i or oominiiouitly ^ h»gh, madiufn or low ipsed. To tirrpftly hook-up *w TWommwMl uiififl ovf macttirari* keypad, CATf KPM't2(lU25oa£:fi) whk^, wth tlgrt mod-ffiea- tbn, workft imH wilh this devico. In si ructions Included. CkT»m04 S3.00oadi FLASH UNITS NEW conpaci flash asswrbln Irom a caffwa maniiadurar. QporatH on 3 Vdc MeaaufM 2\fZ'X\ 1/4". i ^_ ^ - wanung ugh: or atlwitjDn B«aaf. Indudoa a hooii^up cSjg^'am, CAT* fSH-l $3.75 sACh - 1 0 tof m 00 TOO for S37S.00 TOLL-FREE ORDER LINES 1-800-826-S432 hf tfM *S cor^Twtji U S A S3 &0 psr ofzitr AlatfvTS fKiu^ng AX^ Hi, PR or C^raOM miat ptf hjt %hfi(Hfig. AM dtt^mf n CAJ. fOf^iA mtMt ridtJKif rtai* m (F if / ? 75%, n 25% s 5%; ajtnsmm Umttd. titO C O D Ptxi&ssobftrct to >*^'Q*^ notic* FREE 64 Page Catalog Th« U S JL S«nd S2.00 Po«liga} ALL ELECTRONICS CORP. P.O. Box 567 ' Van Nuys. CA * 91408 IM J V The /National Travet and ^Tl^ikssm Awareness Council CABLETRONICS CONVERTERS 1>4UtiUn PANASONIC TZP 145 $88.00 STAR GATE 2000 S79.00 'HAMLIN MCC 3000 $25.00 5 Unltfl 10 Unha $75.00 $70.00 $69.00 $65.00 $19.00 $15.00 ADD<»N DECODERS S8-3(NEW) $50.00 $45.00 *SB-3 FACTORY $45.00 $39.00 SA-3 $56.00 $50.00 DTB-3 $65.00 $55.00 KNi2A-2or3 $49.00 $45.00 ''H AM] LI N MLD 1200-3 $49.00 $40.00 *ZENITH SSAVI $1 65.00 SI 49.00 SA-DF $159.00 $139.00 JERROLD DPV7 JERROLD DPBB SA8580 COMBO •JERROLD DRX-3-DIC JERROLD DR2^3-DIC *OAK M35B HAMLIN SPC 4000 3M ADD $10.00 FOR VARI5YNCH COMBOS $299.00 $319.00 $299.00 $165.00 $175.00 $45.00 $50.00 S2 49.00 $259.00 S225.00 $105.00 $115.00 $35.00 $44.00 $43.00 $35.00 $45.00 $50.00 $40.00 $35.00 $1 25.00 $125.00 $239.00 $249.00 $215.00 $89.00 $99.00 $30.00 $44.00 Refurbished as New QTY ITEM OUTPUT CHANNEL PRICE EACH TOTAL PRICE QAtifcfnJa Ptnal Cede <593-0 Fotblds ui from ■tilipplng any ciibis descrambUng; unit to anyone rnlding In Uie siata of call fern la. Prices Aubjeet to ehanQ« wrlthout notice. SUB TOTAL Shipplnii Add 5.00 Per unit Add a% TOTAL Addles ft O Caa hi af ' » Ch«e k D Mon ey ordor □ vise Dmc CC* Tal:( _CiV_ J □god _Exp. Dalfi_ DECLARATION OF AUTHOFUZHD USE- 1, ttie undmslgnad, do hareby declere under penalty of perjury that all product! purcfiaaed, now and In ttie future^ w^li only be used on TV tyitemi wltti all eppM cable federal and itate Jewa, FEDQ^AL AND VARIOUS STATE LAWS PROVIDE FOR SUB3TANTJAL CRIMINAL AND QVIL PENALTIES FOR UNAUTHORIZED US& Date SiQfled_ Cabtetronics 9B00 D Topanga Conyon Blvd., Suite 323, Chatsworth, CA 91311 For Free Catalog, or to place an order call (800) 433-2011 ■ FAX (818) 709-7565 One trvt' can malif One matirh can bum CONSUMER R N . .Nirw toLid^ttAte and d^ptal TV miM^ timncA^ and md- efflTOiriSert sr* tuugJirr to rr- pair tiiJiii ^Itl'faahianed ii^ tyjtt vfta nnd r^vdr^ apecial tnininif for ihf servi rticck Htich itirt9i« n* "IVm* the bu^inCAs hiivfi ihif [utrti for your par- ttatlar bnnd'*'^. "Did you |e<>i afl «]»iiTnBtrd i^rievT., and "Pidl ynu thftk thia cDirtpany BarratiT MC /cm / VISA NO RDRIDA SALES CABLE TV DESCRAMBLERS WORLDWIDE CABLE * BASE BAl^ • POS^n • TDCOM - ZENITH * SOeJIFC ATLANTA * OAK • JERflOlD • KAMLM 1 800-772-3233 1^91 A POWERLIVE ROAD. SUlTi 109 POMPANO BEACH, FL 33063 / ELECTECH / CABLE T,V. DESCRAMBLERS • All qyalUy brand names ^ • All fulty guaranteed - AlMhetime * KnowlecfgE?ab1e Sales Service Department FOR FREE CATALOG 800-253-0099 C ABLE TV litters, Cfiu^r lypd. The best made^ chamsli m^kim^ Low prices. Quaritty dis- counis. Can 1 (fiOO) 643-9170 ejct. 170. DESCRAMBLERS and [Ufn-<>n kits, no eO0#. no catalog, gust the best prices! We' El b^al any logili- mate pnco — call for details. (407) 852-9576. 300 Experimenters Clrculls — Compieio in 6 practical books usino diodes, relaySn FEFs, LEG'S, IC 555 s, and IC CA3130s for building biocks. Only S33.00 ^us S5.50 for shtpping. USA ajid Can^ only. US funds. ETT, IKC*i PO Boi 240. Massapequa Potk, NY 11762-0240. ANTIQUE RADIO CLASSIFIEE Free Sample! Anttquo Radio's r Largest Circulaibn Monthly. Articles, Ads a Classifieds 6-Month Trial: $15. 1-Yr: S27 ($40*1 st Class A,R,a, P.O. Box 802-L3, Cartisle, MA 01741 CABLE TV convefiers: Jorrold, Oak. Scientific Atlantic. Zenith A many othOfS New MTS" stereo add-on: mute & volume. Ideal for 400. and 450 owners! 1 (800) 826-7633. AmeK, Visa. M.G ac- c&pled B & B INC., 4030 Beau- D- Rue Or\^ Eagan. MN 55122. ELECTRONIC lest equipment and parts. Fret catalog. EF ELECTRONICS, Box 326. Aurora, IL 60507. CABLE TEST CHIPS. S-A 8550. S-A 8500 - 310. 311. 320. 321 {speciJy) — $33.95. S-/ asaO 338 — S69.95 TQCOM 5503O7 VIP — S33.9S Siarcom 6 — S33 95. StaJXOm 7 — S49,95 TELECODE, PO Box 6426-RE, Yuma AZ 85366 6426 CABLE TV descramblefs! Absolutely the lowes prices! All m^^ijor brands. Nobody beats our prices CABLE PRICE CLUB, t (flOQ) 377-9742 PREVENT de^rambter damage. Donl bita thi bulteti! Snooper Stopper Data Pulse Blocke S33.95 with Surge Protection S44 95... Wii©ies V^jeo S^^ndof S34.95 VCl, I 1800> 925-9426, .i FREE CATALOG! 1-800-648-7938 JERROLD HAMLIN OAK ETC CABLE TV DESCRAMBLERS • Sp^cisl Oeahf Prk:esf • Compttfo ouf Law Aetoif PricBS! i • Guafanmd Prices A Wananim! • OfUBfs Shipped trnmedfamiy! REPUBLIC CABLE PRODUCTS, INC. ^ 4080 ParacJise Rd. #15, OeplnciTE»j rn Laa Vegas, NV 89109 irrj for all Qthef informalion (TQg) 363^9026 PAY IV AHO SAmUTlOESmMgUrfG ALL IitVV tW^EPmOH Ail NEW ScrlnUlag Hm, ^S^ HarUI toi.. FREE CATALOG ^ CABLE T.V. BOXES - ALL TYPES • LOW PRfCES - DEALER PRICES - EASY work! Excellent payf Assemble products al home. Call toll free 1 (eOO) 467-5566 Ext. 5192. HOME assembly work avaiiablo! Guaranteijd easy monByl free delails^ HOMEWORK^R, Box 520. DanviHe, NH Q3B19. M0NEYMAKERS1 Easy! One man CRT rebuild' inomachtnery, S6 9CK3 00 rebuilt St5.9OO.O0 new CRT, 1909 Louise, Crysialake. tL 50014 (815) 477-8655 FAX (815) 477-7013 WAKE S75,O00.00 to 5250,000.00 yearly or mote ftx ng IBM cotor moftrtofs. No imestineni, start doir>g fct from your home (a tel^Dhone reqmred). Information, USA, Canada S2.00 cash fof bro- chum, oifier countries SlO.OO US turtds RAN- DALL DISPLAY, Bojc 2l6a-R, Van Nuys. CA 91404 USA FAX (818) 990-7803 EDUCATION & INSTRUCTfON FXX, Commercia) Genef^l Radioietephone li* cense. Etecirontcs home study Fast, inexpen- sive' Free' derails COMMAfJD. D-176, Box 2824. San Francisco. CA 94126. ELECTRONIC engineering. 8 volumes com^ pleie. $109.95 No orior knowfedde reoutred, Fre# bfOCimra. BANNER TECHNICAL BOOKS. 1203 GrarH Avenue. Rockfofd. IL 61103 LEARN electronics and digitai basics. Pro- grammed courses. Si 7,00 each, bolh S29 00. Saiisfaction guaranteed. TEK SOURCES, 6050 NW 6Sth SL, Pa/kland. FL 33067. BUILDINGS A Robot: A Stralqhiforward Approach. 152 pagos fully iHustrated. Tnsiruclrons how you can easrly const rucl a robot Chock or money order Sl9 95plu3S3 OOsh ppmg. HUMANFORM ROBOTICS. PO BOK 158486. Nashville. TN 37215. WHY Buy e^ipenslve batteries? Lsam how to; salvage vjrtua'iy Iree rechargeable nicad batteries from doturKl baTtery p^ks. Use these oefis m radios, flashlights, etc SAS£ bnims deiaUs. DAY BY DAY PUBUSHING. Box 490, Ovefton, NV 89040. MlNfATURE gambling computer Play perfect biack|ack. dock foulette wheels, etc. Free infor- rriation ALT ENTERPRISES, Box 424, Porifand. OR 97207. SATELLITE TV -REE catalog — Lowest prices worldwide. SKY- /ISION, 1012 Frontier. Fergus Falls, MN 56537 1 eoO) 334-6455, See full page ad the Shopper ^tion. SATELLITE TV — Do il yourself — major braiwls nscouni&d. we [J beat everyone s price DIS- :OUNT t^RRY (609) 596-0656. /lOEOClPHER ft, descrambling mafiual. Sct>o* riaics. Video, and ajcfo Expia DES. Eprom :ioneMaster, 3Muskeieer. Pay-per-view (HBO ^inemax, Showbme. AduEl, etc ) Si 6 95. S2.o6 lostage Schematics tor Videocypher Plus 120 00. Schematics ior Weocypber 032. Sl5,0o! k»t:eciJon of software to copy aiKl alter Eprom odes, S25.0O CABLETRONICS, Box 30502R tethesda. 1^0 20B24. ftUP€R row satellrte prices. Free U,3. and Inior^ laiJonal caialog. SATMAN, (309) 692-4140 (fnt'l) (900) 472-8626 In U S. BUSINESS OPPORTUNITIES 'OUR owin radio station! Licensed unlicensed ^M, FM. TV, cable Infonmaiion Sl .OO BROAD- CASTING, Box 130-Fn, Paradise, CA 35967 ET the government fmance your srr^l business, irants loans to S500,000. Fjeo recorded mes- age (707) 44&.6600. (KSl) CABLE TV -800-582-i 11-4 FREE CATALOG UARAHTEED BEST PfifCES • IMMEDIATE SMIPftHG M.K. ELECTRONICS PtnV£Sr R£TA4f W^-KXfSALE mC£S IN l/S • Ml MAJOtt cnOfT J^CEVTfO FOR AU rNFORMAHOIV ^ — l-tW^345-Znj ^ PACIFIC CABLE CC INC. 7325> J Reseda Blvd..Oepi 2120 I Reseda. CA 91335 BEST BY MAIL flmr WrflB Wttlcnal, Box 5, Si moll, FL 34230 OF INTEREST TO ALL FREE PROFITABLE Avef^u* G. For! V&tJ'; INFORMATION: HERBS 4 Sf^lCES HERSS. SFlCfS. SASt f^erb Se-^s*. 1012 irvJng St Bo* San Francisco. CA 9^122, LEARN gold, sitver, platinum scrap rocydtng busi- ness. ^Fre©) (nformation. Wnie: RECVCUNG* Box 11216PE , Reno, NV 89510-1216. ELECTRONICS dealers: Expand your product line Make SSS! BtKome an AM ERIC AN ELEC- TRONICS deatef ! Profii opportunities sinco 1965 Call ScQtl Pfugtt. I (800) 872-1373. SATELLITE Television. A new money making business A 4 hour instaJt makes approitfmatoEy SSOO.OO and service rates average S50 00 hr, E)t- ceClent pari or full Irme income. Get sLirted. send lor your trainifig kits loday. Home Saleliiio televi- sion kit S39.9f Commercial Salellrte kit S49.95, Order bolh to roceiveyourfree vkJeo and suppltes ItSL ENTERPRISES. Box 76051 SnawUre Blvd SW, Calgary. Alberta, Canada T2Y-229. I ■ ^ ^ '*c*»li»IC«fiifMt«TWii4nt,0^ ^ 224S P**iratft» Pk . JUIinU. Gfl<»rgU Learn CoMPUTERsJl Homcatuci-y tft?conii? .vi npcrt wLm ihe I p*t%Or^i eSfr.pi.teT tor home oi btuirne-ti g UM. ¥tn lltenlurt i c Mtt BQO-n^S*!. | I 1 WANTED INVENTORS: We submit ideas to indusiry Find out what we can do for you. 1 (600) 288«fDEA. INVENTORS I^ONfTOR CORDLESS TELEPHONE C ^ Tim fiMigiiirgrB Qjfior Sao o^eea m tht £i»3sirc octxrme PHONE ORDERS «1 875 SO, 72nd SL Om^ha, KE 68114 ADVERTISING INDEX Electronics Novv does not as&ume any responsibility for errors that may appear in the index below. Free I nf or ma I i on N g m ber Page m AMC Sales... .22 75 Ace Pniducls 87 107 All Kkclrunlcs. ., ...95 84 ApplUinci' Service MT 176 Bi^kman Induslrial 12, 13 177 Beckmun Industriiil ..... . 22. 23 Ift9 C&SSales 15 — CIE. ...8 — Cabklronics 96 — Com ITU1 nd Prod u ct ions 127 Dcct> Industries , , K7 194 Electronic tiotdmiiie «/K — Elrdninics Book Viub . , . „ . 7, «0 121 Flu ke M a n u fac t u rt Ji g C V2 192 Fordham . 17 1K2 Gldbul Spiciiiltics 3 Gntfldiam College .60 I9Q HAM EG InstnunrfiU .26 86 Hcalhklt. 89 — HighTeiit Puhficatlnns, tnc 7ft IH4 ICS Computer TVuining 89 — ISCET . - 79 114 Jameco ^_.92,93 115 Jcm.cn Tools ,87 tSl Kcpco Inc .25 53 MD Eleclronics 98 117 ^Suu.sc^ ..V 12 — NRI Schools.,. .18 1 79 Nort h cast Electronics 13 1 80 Ptople^s College 29 till Pomona Klectronlcs 71 7H Radio Shuck. 311 192 Scope Eicclfonics 17 193 Sencor* CV4 — Star Circuits 87 Free Information Numtser Page 187 Tech Spray 25 178 Tiktronix 27 — rhe Sl»EC-COM Journal , 85 183 The Sthw»l Of VCR Repair . , , . 85 1 9 1 Vicjo hi t cations « 79 188. 189 Zcntck Corp, 73 ADVERTISING SALES OFRCE G«rn«lui?k Publications, Inc. 500 B Dl-Couoly Blvd. Farmlogdale, NY 11735 1-C516) 293 30QO PretjdenI: Larry Stvcldvr For Advsrtlming ONLY sie-ads-aooo Fax 1 516*293-3115 L»rry Stickler publtsli«r ChHttlna Estrada a^sistiint to the Pmiidenl Arltns Finhman advertising director DtifilBo Mullen advE^rtiiing a^istant Kelly McQuade credrt manager Subscnb#r Ctt*tan»r Service 1-800 2830652 Order Entry for New Submcribera 1 '800-999 -7 139 7;00 AM • 6;00 PM M F MST ADVeftTISiNG SALES OFFICES EAST/SOUTHEAST Stanley Levltan. Easlam Adv«rttstng Sales Manager Electrunics Now 1 OvoH{>ok Ave, Great NetV, NV 11021 1-51 6-437- 93 57. t- 51 6-293-3000 F» t'516-437-8402 MlDWEST/Teus/Arkan«aB/Olita. Ralph Bergen, Midwnt Advertising Salem Manager Electron ica Now One Nofthfiiild Raia, Suite 300 NoFthfield, \L 60093*1214 1-708-446-1444 Fai 1 706'559-0562 PACIFIC COAST/Mountain Stataa Elect ronlci Now Magaxina Pamela Kuxter PattiV3M 1800 North Highland Avenue Soite717 HollywDad.CA 90028 EN Shopper Joe Share, Natiooat Bepreientative RO. Box 169 tdyifwild. CA 92549 V714^9^9743 Fax 1-714'65§-2469 CIBCL£ £3 OH FREE tHFORUATION CARD Countersurveillance fever before has so much rofessionai Information on the art f detecting and eliminating lectronic snooping devices — and ow to defend against experienced iformation thieves— been placed 1 one VHS video. If you are a ortune 500 CEO, an executive in ny hi-tech industry, or a novice eeking entry into an honorable, marding field of worii in ountersurveiliance, you must iew this video presentation again nd again. Wake tip! YoLi may l>t' the victim of olen words — precious ii;ltM5 tkac would ivc rniKie you very weairfiy! ^'cs, prof'es- onals, even mrik amiucurs, may be lis- rting 10 your mosr private con- ^rsarions. Wake fipl Jf you are not the vietim, len you arc surrounded by countless vic- rtis who need your hei[> if you know how ) disct>ver teieplione taps» locate bu^s, or Avccp" a room clean. There is a thriving professional ser^'ice ccped in hi^h-tecli techniques that you m become a part oV. But first, you must n t J w a nd u nd e rs t a nd C a » u n te rs u r ve i I ance L^chnolo^y Vour very 6rsr insight into lis lujL^hly rewarding field is made possi- le by a video VHS presentation that you innot view on broadcast television, sat- lire, or cable. It presents an informative ro^ram prepared by |irt)fessionals in the odd who know rlieir industry, its tech- iques, kinks and loopholes. Men who ui tell you more in 45 minutes in a rai ghr for ward , exclusive talk than was /CT attempted Ix-fore. I'o i I i n g I n f o r ni iit i o II Th i e^ es Discover the targets ]> rofessionai iWfK'rs seek out! llie [irey are stock rokers, arbitrage firms, manufacturers, ]gh -resell companies^ any competitive V d us t ry, ( J r e ve n small 1^ u s i n n esses in t h e I me eommunity I'he valuable itifonna- on they fikli joay be marketing strat- >ies, customer lists, product formulas, lanufacruring techniques, even adver- sin^ plans. lnfr>rmarion thieves eaves- rop on court decisions, bidding iformation, fmaruial data. The list is niimited in the mind of man — es- ecially if he is a chieH Vou know that the Russians secretly IS railed countless niicro]iht)nes in rhe m Crete work of the American Embassy uilding in Moscow. They converted HAVE YOUR VISA or MC CARD AVAILABLE what wiis to be an embassy and private residence into the most sophisticated re- cording studio the world had ever known. The building had to be torn down in order to remove all the bugs. Stolen Information The t)pen taps from where the intorma- tion [x)urs out may be from FAXs, com- puter communicatitHis, telephone calls, and everyday business meetings and hi n c h f i ni e e net >u n te rs - H us i ness men need counselling on how to eliminate this in- formation drain. Basic telephone use cou- pled with rhe users understanding that someone may be listening or recording vital data and inforniatitHi greatly reduces the oppt^rtunity for others to purloin m can i ng lu I i n formac i on . I CIAGCIK INC. EN [ j Rl>. H«\ 4099 • I";inni!igdiik% NY 11735 " I l^k'.LSf riJiJinn iujn nf llu- t inniUT'*unLi]hiiiLt' Ii:i.h]i]t]L]<.:s I irH'li:iilr>^ ^ i i'tii poM:ii^i' .inil l],bnilljn>;^. I \£ >. ( al' i iiisvE't t ( jrtli'j'fi; \ ► . ' AnitHinc L»E |>j|timm * . J Sillf ^ c ;i \ i \ A . S. ( mSj ) . I Kin mj D VISA □Makii'Kiiitl I (jrti.'Vv ] pi ri- 1 niv / , J I Ntin^uurtr I V JOH" ^ I Aikkt^ I = Sf his home. After you review the video caretully and understand its con- tents, you have taken the first important step in either acquiring professional help with your surveillance problems, tjr you may very wx'll consider a career as a coun- te rs u rve ilia nee p mfcss i onal . The Dollars You Save To obtain the information contained in the video VMS cassette, you w^ould attend a professional seminar costing 53 50-7 5 1) and possibly pay hundreds of dollars more if you had to travel tti a distant city to attend. Now, for only $49-95 (plus $4.00 Pd<:I"l) yt)u can view Con titers u r~ veiliatict lechtiiifties at home and take refresher views often. To obtain your copy, complete the coupon or call . 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