Build a Super -Simple Laser Power Supply 48784 Popular Electronics Make a Mac The Electronic Get a better, more expandable machine, Dragonfly and save some cash in the bargain, when Turn pieces of piezo- you build your own Macintosh computer electric film into a fun - to- build, fun -to -use conversation piece All About Receiver Sensitivity Find out what those receiver- sensitivity specs really mean GERNSBACK PUBLICATIC^. rocct Reviews Build the Socket Sentinel onyjo a e A surge -protected, "smart" power strip system, Pulsar that let's you use one device to control 72 -inch up to three others projection TV, and much more What Do Electrical Engineers Do? Is a career as an electrical engineer right for you? 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Data and circuits for reasonably low cost, yet worthwhile interfacing the computer to the robot's monophonic synthesizer and learn a lot motors and sensors. THE BOOKS YOU WANT about electronic music synthesis in the i process. SHIPPING CHARGES IN ELECTRONIC TECHNOLOGY TODAY INC. USA AND CANADA SORRY No orders accepted Number of books ordered I I P.O. Park, 11762 Box 240, Massapequa NY -0240 outside of USA & Canada $0.01 to $5.00 $1.50 $5.01 to $10.00 $2.50 Total price of merehandise $ Name $10.01 to 20.00 $3.50 Sales Tax (New York State Residents only) $ to 30.00 . $4.50 Address $20.01 Shipping (see chart) $ $30.01 to 40.00 $5.50 City State Zip All payments must $40.01 to 50.00 $6.50 Total Enclosed S be in U.S. funds P -991 $50.01 and above $8.00 J www.americanradiohistory.comAmericanRadioHistory.Com SEPTEMBER 1991, VOLUME 8, NO. 9 Popular ctroiiicS THE MAGAZINE FOR THE ELECTRONICS ACTIVIST! CONSTRUCTION ARTICLES BUILD A SIMPLE LASER POWER SUPPLY Gregory Gray 32 Learn about laser operation with this easy -to- build, low power, laser-tube power-supply circuit THE ELECTRONIC DRAGONFLY Marc Spiwak 55 Make your next project a most unusual one BUILD THE SOCKET SENTINEL Marc Spiwak and John Yacono 63 Control the power to all the components in your A/V or other system using one component's own on /off switch! FEATURE ARTICLES MAKE YOUR OWN MAC .. Elliot Kantor 26 You can build an easily expandable Macintosh with some built -in frills for less than what a new no- frills unit would cost WHAT DO ELECTRICAL ENGINEERS DO? Harry L. Trietley 35 Read this article and find out; maybe you'll also learn if an engineering career is for you INSIDE THE SONY MINI DISC Brian C. Fenton 39 Will Sony's new Mini Disc revolutionize the portable audio industry, or will it simply muddy the waters for years to come? ALL ABOUT RECEIVER SENSITIVITY Joseph J. Carr 61 Learn about the different ways that receiver sensitivity is measured and specified, and what each rating really means PRODUCT REVIEWS GIZMO 43 Including: Sony Portable Shortwave Receiving System, Design Acoustics Video Speakers, and much more HANDS -ON REPORT 66 OWI WAO ll Mobile Robot Kit PRODUCT TEST REPORT Len Feldman 68 Pulsar TVP 2000 "Prodigy" Projection TV Receiver COLUMNS THINK TANK John Yacono 18 Controlling power COMPUTER BITS Jeff Holtzman 70 The 386 revolution continues ANTIQUE RADIO Marc Ellis 72 The theremin: A first look inside CIRCUIT CIRCUS Charles D.