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Popular Electröriics Build the Sonic Defender an Effective, Non -Lethal Deterrent to Those Who Wish You Harm 4878 Simple VCR Repairs that YOU Can Do! II; Popular Electröriics Build The Sonic Defender An effective, non -lethal deterrent to those who wish you harm. It protects you and your property with a blast of high- intensity sou nd Build The "Slot- Machine" Bank See your pocket change pile up with this fascinating electronic bank Weather -Alert Decoder It keeps a "weather eye" peeled for National Weather Service emergency alerts All About Meters Learn how analog and digital meters work, and how to design circuits to measure voltage, current, and resistance The Birth of the Vacuum Tube Lee de Forest claimed that he got the idea for the audion from a gas flame; Fleming l GERNSBACK thought that story was just hot air! _s i ._L_- r=:i 5 _LiRÌ'lMq9t;i-{0 'EE?2 a 3 NEW ,ROBERT C'AHM $2 95 U.S. FactCards F;i*'At-:i' ;_;mFnI?°A : $3.75 CANADA IN THIS ISSUE IL o 48784 7 www.americanradiohistory.comAmericanRadioHistory.Com 6 Electronics Paperback Books GREAT PAPERBACKS AT SPECIAL PRICES [I BP248 -TEST BP267 -HOW TO BP265 -MORE Le Wy410Y0stop BP256 -INTRO TO EQUIPMENT CON- Testequipment uwrow. USE OSCILLO- ADVANCED USES iari+.eru.e end LOUDSPEAKERS Construction STRUCTION 01d0./Toot SCOPES AND OF THE MULTI - 00001 uesUe AND ENCLOSURE $5.95. Details con- OTHER TEST EQUIP- METER $5.95. Use DESIGN $5.95. We struction of simple, in- MENT $6.95. Mas- these techniques to explore the variety of expensive, but ex- tering the oscilloscope test and analyze the enclosure and speaker tremely useful test is not really too difficult. performance of a vari- designs in use today so equipment. AF Gen, This book explains all ety of components. the reader can under- Test Bench Ampl, Au- the standard controls Also see how to build stand the principles in- dio Millivoltmeter, Tran- and functions. Other ad -ons to extend multi- volved. sistor Tester and six equipment is also de- meter capabilities. more. scribed. BP263 -A CON- BP260- CONCISE 1 BP249 -MORE CISE INTRO TO INTRO TO OS /2 ADVANCED TEST dBASE $6.95. The $5.95. If you are a mul- EQUIPMENT CON- dBASE series of pro- titasking PC user and STRUCTION grams are probably the want to get the most $6.95. Eleven more best known database out of your computer. test equipment con- programs for micro- then you must learn its struction projects. computers. This book _A, 4. OS,2 operating sys- They include a digital is designed to help you tem. This book shows voltmeter, capacitance get started working you just how to do that. meter, current tracer with them. á' quickly and easily. and more. PCP102- INTRO- mo BP245- DIGITAL BP247 -MORE BP257 -INTRO TO DUCING DIGITAL AU- AUDIO PROJECTS ADVANCED MIDI AMATEUR RADIO DIO $9.95. Covers $5.95. Practical cir- PROJECTS $5.95. $6.95. Amateur is a all kinds of digital re- cuits to build and ex- Circuits included are a unique and fascinating cording methods - periment with In- MIDI indicator, THRU hobby. This book gives CD, DAT and Sam -, cludes AC converter, box, merge unit, code the newcomer a com- pling. Bridges the gap input amplifier, digital generator, pedal, pro- prehensive and easy to between the technician delay line, compander, grammer, channelizer, understand guide to and the enthusiast. echo effect and more. and analyzer. the subject. Principles and meth- ods are explained. PCP108 -COM- DIGITAL PCP107- DIGITAL BP251- COMPUT- PUTERS AND MUSIC LOGIC GATES LOGIC GATES AND ER HOBBYISTS $9.95. Explains the AND FLIP-FLOPS FLIP FLOPS HANDBOOK basics of computers $10.00. Thorough $8.95. A wrapup of ev- and music with no pre- treatment of gates and erything the computer vious knowledge of flip -flops for enthusi- hobbyist needs to computers needed. asts, student and tech- know in one easy to Covers types of music nicians. Only a basic use volume. Provides a software and explains knowledge of elec- range of useful refer- how to set up your own tronics is needed. ence material in a sin- computer music stu- gle source. dio. BP195- INTRODUCTION TO SATELLITE TV $9.95. A definitive introduction to BP239- GETTING THE MOST FROM YOUR MULTIMETER $5.95. Covers the subject written for the professional engineer, electronics enthusiast, Or others basics of analog and digital meters. Methods of component testing includes who want to know more before they buy. 8 x 10 in. transistors, thyristors, resistors, capacitors and other active and passive devices. BP190-ADVANCED ELECTRONIC SECURITY PROJECTS Includes a $5.95. i BP97 -IC PROJECTS FOR BEGINNERS $5.50. Power supplies, radio and passive infra-red detector, a fiber -optic loop alarm, computer -based alarms and an audio circuits, oscillators, timers, switches, and more. If you can use a soldering iron unusual form of ultrasonic intruder detector. you can build these devices. BP235 -POWER SELECTOR GUIDE $10.00. Complete guide to semiconduc- BP37 -50 PROJECTS USING RELAYS, SCR'S & TRIACS $5.50. Build pri- tor power devices. More than 1000 power handling devices are included. They are ority indicators, light modulators. warning devices, light dimmers and more. tabulated in alpha -numeric sequency, by technical specs. Includes power diodes, Thyristors, Triacs, Power Transistors and FET's. RADIO -100 RADIO HOOKUPS $3.00. Reprint of 1924 booklet presents radio circuits of the era including regenerative, neutrodyne, reflex & more. BP234- TRANSISTOR SELECTOR GUIDE $10.00. Companion volume to BP235. Book covers more than 1400 JEDEC, JIS, and brand -specific devices. Also contains listing by case type, and electronic parameters. Includes Darlington BP42- SIMPLE LED CIRCUITS $5.50. A large selection of simple applications transistors, high -voltage devices, high- current devices, high power devices. for this simple electronic component. BP99-MINI-MATRIX BOARD PROJECTS $5.50. Here are 20 useful circuits BP127-HOW TO DESIGN ELECTRONIC PROJECTS $5.75. Helps the reader that can be built on a mini -matrix board that is just 24 holes by ten copper -foil strips. to put projects together from standard circuit blocks with a minimum of trial and error. BP82- ELECTRONIC PROJECTS USING SOLAR CELLS $5.50. Circuits with applications around the home that am powered by the energy of the sun. Everything [ 1 BP122 -AUDIO AMPLIFIER CONSTRUCTION $5.75. Construction details for from radio to receivers, a bicycle speedometer, to timers, audio projects and more. preamps and power amplifiers up through a 100-waft DC- coupled FED amplifier. BP117- PRACTICAL ELECTRONIC BUILDING BLOCKS-Book 1 $5.75. Oscillators, Timers, Noise Generators, Rectifiers, Comparators, Triggers and mom. BP92-CRYSTAL SET CONSTRUCTION $5.50. Everything you need to know about building crystal radio receivers. BP184-INTRO TO 68000 ASSEMBLY LANGUAGE $6.95. The 68000 is a great new breed of microprocessor. Programming in assembly language increases BP45- PROJECTS IN OPTOELECTRONICS $5.50. Includes infra -red detec- the running speed of your programs. Here's what you need to know. tors, transmitters, modulated light transmission and photographic applications. ELECTRONIC BP185- ELECTRONIC SYN- LI BP179- CIRCUITS THESIZER CONSTRUCTION FOR THE COMPUTER CONTROL OF $5.95. Use this book to learn how to build a ROBOTS Data for $7.50. and circuits C HECK OFF reasonably low cost, yet worthwhile interfacing the computer to the robot's monophonic synthesizer and learn a lot motors and sensors. THE BO OKS YOU WANT about electronic music synthesis in the i i process. SHIPPING CHARGES IN ELECTRONIC TECHNOLOGY TODAY INC. USA AND CANADA SORRY No orders accepted Number of books ordered I I PO Box 240, Massapequa Park, NY 11762 -0240 outside of USA & Canada $0.01 to $5.00 . $1.25 $5.01 to 10.00 . $2.00 Name Total price of merchandise $ $10.01 to $20.00 . $3.00 Sales Tax (New York State Residents only) $ Address $20.01 to $30.00 . $4.00 Shipping (see chart) $ $30.01, to $40.00 . $5.00 City State Zip All payments must $40.01 to $50.00 . $6.00 Total Enclosed $ be in U.S. funds P -591 $50.01 and above . $7.50 www.americanradiohistory.comAmericanRadioHistory.Com MAY 1991, VOLUME 8, NO. 5 G. Popular Electronics THE MAGAZINE FOR THE ELECTRONICS ACTIVIST! CONSTRUCTION ARTICLES THE SONIC DEFENDER Phil Salas 25 Protect yourself and your property with a blast of high -intensity sound BUILD THE "SLOT MACHINE" ELECTRONIC BANK Marc Spiwak and John Yacono 35 Watch your pocket change add up with this fun -to- build, fun -to -use electronic bank WEATHER ALERT DECODER Keith Rawlinson 62 You'll never miss another severe-storm warning with this weather -alert detection device FEATURE ARTICLES ALL ABOUT METERS Stephen J. Bigelow 28 With a little know -how, you can design and build your own metering circuits THE BIRTH OF THE VACUUM TUBE James P Ryback 40 A look at the device that made world -wide radio communications practical, and at the men who battled to control it SIMPLE VCR REPAIRS THAT YOU CAN DO Sam Allen 57 This guide to basic VCR repairs can save you a bundle. PRODUCT REVIEWS GIZMO 45 Including: Sharp Vision XV-100 Projection -TV System, Fosgate Surround Sound Processor, and more HANDS -ON REPORT 65 Laser PC4 Portable Computer PRODUCT TEST REPORT Len Feldman 67 Toshiba M -441 VCR COLUMNS THINK TANK John Yacono 20 Multiplexing with counters ANTIQUE RADIO Marc Ellis 69 Operating the Cunningham Special COMPUTER BITS Jeff Holtzman 72 Hypertext: hype or text? CIRCUIT CIRCUS Charles D. Rakes 74 Test instruments for your bench HAM RADIO Joseph J. Carr 78 An audio -noise blanker DX LISTENING Don Jensen 80 Reader mail SCANNER SCENE Marc Saxon 82 A high -tech turbo scanner DEPARTMENTS EDITORIAL Carl Laron 2 LETTERS 3 ELECTRONICS LIBRARY 4 NEW PRODUCTS 12 ADVERTISER'S INDEX 92 Popular Electronics (ISSN 1042 -170X) Published monthly by Gernsback Publications, Inc., 500 -B Bi-County Boulevard, Farmingdale, NY 11735.
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