RESTORING AN OPE _-; EEL TAPE RECORDER le FEBRUARY 1998 NOW® Build a Multichannel Oscilloscope Trigger Troubleshoot and debug even the most complex digital circuits with a standard scope and this accessory A Precision Voltage/Current Reference Build one and perform lab -grade measurements on your own workbench Build a POC$AG Encoder Create your own pager messages $4.50 U.S. $4.99 CAN. The Great £LOZ-940iZ OW ttI9WS1103 -ma H1Vd NIWHtl31ä39Óá N3I6 66 &Id Compression ZIStIO 4£L094ßL £60ä5I56WHOß 1111"' 1' 1' "I MPEG is what makes today's I"' I II I' 1""11' 1"1"" I ' I' I"11"I"' high- capacity multimedia possible; 9401Z 1I9I0-5 ******3MbONX84 here's how it works www.americanradiohistory.com Professional Power at a hobbyist price. That has been our philosophy at MicroCode Engineering since 1987. So it's no surprise that CircuitMaker and TraxMaker are the leading software tools for affordable, easy -to- use circuit design, simulation and PCB layout. QUICKLY DESIGN analog, digital or mixed analog /digital circuits with CircuitMaker's `ldrti(rl®IcT7II{i~I 12fJ/J4211 U advanced schematic features. You fully control the wiring, device placement, annotation and colors. And the Symbol Editor and macro features let you create unlimited custom devices and symbols. SIMULATE and ANALYZE what you create try all the "what if" scenarios with: CircuitMaker® schematic capture Fast, proven 32 -bit SPICE 3f5/XSpice simulator and simulation True mixed analog /digital simulation Fully interactive digital logic simulation 4,000 -device library AC Frequency Analysis DC Operating Point Analysis DC Transfer Function Transient Analysis TraxMaker' PCB layout and autorouting Step Function step component values and sources over a user -definable range A.F.a Ld 50w Bd. Rah Hep I H R TAKE MEASUREMENTS at any point in the circuit with a click of the Probe tool. Results appear immediately on virtual instruments like the Digital Oscilloscope, Curve Tracer, Digital Multimeter and Bode Plotter. No other simulator lets you take measurements as quickly and easily as CircuitMaker. COMPLETE the design process with TraxMaker, a professional printed circuit board layout program with built -in autorouter. Import netlists from CircuitMaker and other schematic programs, or design boards from scratch. Includes autorouter, auto component placement and Design Rules Check Supports up to 8 copper layers, board sizes up to 32 x 32 inches LMyPUm Surface mount and through -hole components from a customizable library r Pna e r semN J Outputs your PCB as a Gerber file, Excellon N/C drill file, and prints to any Windows -selectable printer or plotter J J RELY ON free technical support from qualified engineers. And every ,wLd,a, MicroCode product is backed by our 30 -day Money -Back Guarantee if it does not live up to your expectations. CircuitMaker version 5 $299 Call 800- 419 -4242 for more TraxMaker Version 2 $299 information and free demos Design (or download from www.microcode.com) CircuitMaker Suite" CircuitMaker and TraxMaker) $549 CIRCLE 171 ON FREE INFORMATION CARD MicroCode Engineering Inc 927 W. Center St Orem, UT 84057. 801 -226 -4470 Fax: 801 -226 -6532 Email:sales @microcode.com CIRCLE 133 ON FREE INFORMATION CARD www.americanradiohistory.com Electronics NOW Vol. 69 No. 2 CONTENTS1 8 F E B R U A R Y 9 9 ON THE COVER TECHNOLOGY 13 PROTOTYPE 33 BUILD A MULTICHANNEL OSCILLOSCOPE TRIGGER While an oscilloscope is among the most useful pieces of test gear one could own, there are times it falls short medical sensors, 50 -inch of our needs, such as Tiny RESTORING AN OPEN-REEL TAPE RECORDER high- definition plasma TVs, when troubleshooting using space technology to treat a computer or another fronts tumors, and more. complex digital circuit. THE GREAT COMPRESSION Build a Multichannel 37 For example, have is what makes many of Oscilloscope Trigger MPEG you ever tried to 'eeareerarwlr>r- today's high- capacity confirm that data was multimedia technologies possible; here's how it works. being written to the A Precision Yasuda Hiroshi Voltage; Current - correct address or that Reference own woretworn A the correct bit is being on row 46 RESTORING "REEL" Build RECORDER set during a memory Pocsi: tjn:aller operation, using just a the Grew Compression standard, two- channel nqn ..cnr multimedia ow* hare s how 1 wens scope? Impossible, you say? Well, not anymore- thanks to this month's cover story. If you troubleshoot digital electronics, this is one accessory that you just can't do without. - Thomas Peterick Bring those marvelous open - reel recorders of yesteryear back to life. - Phil Van Praag techniques and scientific and technological As a service to readers, ELECTRONICS NOW publishes available plans or information relating to newsworthy products, ELECTRONICS NOW disclaims any developments. Because of possible variances in the quality and condition of materials and workmanship used by readers, responsibility for the safe and proper functioning of reader -built projects based upon or from plans or information published in this magazine, NOW disclaims any liability for Since some of the equipment and circuitry in ELECTRONICS NOW may relate to or be covered by U.S. patents, ELECTRONICS interested in such projects consult a the infringement of such patents by the making, using, or selling of any such equipment or circuitry, and suggests that anyone patent attorney. County Boulevard, Farmingdale, NY 11735- ELECTRONICS NOW, (ISSN 1067 -9294) February 1998. Published monthly by Gernsback Publications, Inc., 500 Bi- No. 334103, authorized at Mississauga, Canada. 3931. Periodicals Postage paid at Farmingdale, NY and additional mailing offices. Canada Post IPM Agreement Tax, Registration No. R125166280), all One -year subscription rate U.S.A. and possessions $19.97, Canada $27.79 (includes G.S.T. Canadian Goods and Services drawn on a U.S.A. bank. Single copies other countries $28.97. All subscription orders payable in U.S.A. funds only, via international postal money order or check $4.50. ©1997 by Gernsback Publications, Inc. All rights reserved. Printed in U.S.A. -5115. POSTMASTER: Please send address changes to ELECTRONICS NOW, Subscription Dept., Box 55115, Boulder, CO 80328 if their return is desired should they be rejected. We A stamped self- address envelope must accompany all submitted manuscripts and /or artwork or photographs possession or otherwise. disclaim any responsibility for the loss or damage of manuscripts and/or artwork or photographs while in our 1 www.americanradiohistory.com F E B R U A R Y 1 9 9 8 B U I L D T H I S 42 BUILD THIS POCSAG ENCODER Generate your own pager r Electronics signals with your computer NOW® and this simple interface. Hugo Gernsback (1884 -1967) founder - Robert B. Whitaker LARRY STECKLER, EHF, CET, Editor -in -chief and publisher 51 BUILD THIS PRECISION ADRIA COREN, Vice -President VOLTAGE /CURRENT KEN COREN, Vice- President REFERENCE EDITORIAL DEPARTMENT Perform laboratory -grade CARL LARON, editor measurements on your own JOSEPH J. SUDA, technical editor workbench. JULIAN S. MARTIN, associate editor EVELYN ROSE, assistant editor - Skip Campisi TERI SCADUTO, assistant editor MICHAEL A. COVINGTON, N4TMI contributing editor DEPARTMENTS SAM GOLDWASSER, service editor JEFFREY K. HOLTZMAN, computer editor FRANKLIN J. MILLER, audio editor 11 EQUIPMENT REPORT DON LANCASTER, Nomai 750.c portable SCSi contributing editor DEBBIE CYBULA, editorial assistant hard drive. ART DEPARTMENT ANDRE DUZANT, art director RUSSELL C. TRUELSON, illustrator COMPUTER CONNECTIONS 12 PRODUCTION DEPARTMENT Pilot port I /O. RUBY M. YEE, production director - Jeff Holtzman KATHRYN R. CAMPBELL, production assistant KEN COREN, desktop production director 22 TECH MUSINGS _ISA BAYNON, desktop production A tiny TV test generator, MELISSA GIORDANO, desktop production investigating Brown's Gas, CIRCULATION DEPARTMENT and more. THERESA LOMBARDO, circulation manager - Don Lancaster GINA GALLO, circulation assistant REPRINT DEPARTMENT 83 SERVICE CLINIC MARIE FALCON, reprint bookstore How printers and copiers work. 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