Modular Aud Power System Spectrum Dac/Adc Board Signal Generator F-V Converter Microwriting

Australia $1.60 New Zealand $1.75 M alaysia $4.95 P R A CTIC AL FE B R U A R Y 1985 -

ELECTRONR O B OTIC S - MI C R O S ELE- CTR O NIC S- INTE RFCS ACIN G

MODULAR AUD POWER SYSTEM SPECTRUM DAC/ADC BOARD SIGNAL GENERATOR F-V CONVERTER MICRO WRITING The Principle and the Product Have you one of these?

r BBC * COMMODORE 64 DRAGON * VIC 20 ORIC 1/ATMOS ATARI 400/800 SPECTRUM * ZX81

ou need 0 Of these

Best Guide to Microcomputer Software sonwaRe INDEX 1984N0.5£1.50

Now with 5,000 programs more educational, games, business & personal ON SALE management listings than ever before! NOW! R O B O TIC S MI C R O S ELE CT R O NIC S INTE RF A CIN G ISSN 0032-6372 V OL U M E 21 I\J9 2 FE B R U A R Y 19 8 5

C O NSTR UCTIO N AL PR OJECTS

M ODULAR AUDIO PO WER SYSTE M —Part 1 by M. Tooley BA and D. Whitfield MA MSc CEng MIFF. 10 Main power amp module SPECTRU M DAC/ADC BOARD by R. A. Penfold . 15 Interface board for control applications MICROPROCESSOR CONTROLLED D.C. MOTOR DRIVERS by Tom Gaskell BA(Hons) CEng M1EE . 31 Enables analogue driving of dc. motors SIGNAL GENERATOR & F-V CONVERTER by John M. H. Becker 34 Quality test instrument NEPTUNE AND MENTOR ROBOTS by Richard Becker and Tim Orr . 49 Part Six: Com missioning and testing of Neptune M ONO/STEREO CHORUS & FLANGER by John M. H. Becker . 59 Part Two: Construction and setting up

G E NE R AL FE AT U RE S

MICRO WRITER by Tom Gaskell BA(Hons) CEng MIEE . 22 An ingenious six-key alternative to the QWERTY keyboard SEMICONDUCTOR CIRCUITS by Tom Gaskell BA(Hons) CEng MIEE . 28 Power Op-Amps (TCA 365 and TCA 2365) SPACE WATCH by Dr. Patrick Moore OBE 40 INGENUITY UNLIMITED .. 42 Readers' circuit ideas SEQUENTIAL LOGIC TECHNIQUES by M. Tooley BA and D. Whitfield MA MSc CEng MIFF 55 Part Five: Data multiplexers

N E WS & C O M M E N T

EDITORIAL 7 BAZAAR . .. 18,48 MICROBUS .. .. 65 NE WS & MARKET INDUSTRY NOTEBOOK.. 21 VERNON TRENT .. .. 67 PLACE .. 8 LEADING EDGE .. .. 25 P.C.B. SERVICE .. .. 68

THIS MONTH'S COVER...

Our cover photograph shows silicon wafers in a furnace during the production of integrated circuits. Photograph courtesy of National Semiconductor.

OUR MARCH ISSUE WILL BE ON SALE FRIDAY, FEBRUARY 1st, 1985 (see page 47)

IPC Magazines Limited 1985. Copyright in all drawings, photographs and articles published in PRACTICAL ELECTRONICS is fully protected, and reproduction or imitations in whole or part are expressly forbidden. All reasonable precautions are taken by PRACTICAL ELECTRONICS to ensure that the advice and data given to readers are reliable. We cannot, however, guarantee it, and we cannot accept legal responsibility for it. Prices quoted are those current as we go to press.

ItPractical Electronics February 1985 TRANSISTORS 221929im8 11: TIM - 11 g11.415 II r11 5458/9 160 WATFORD .ELECTRONICS - 35 TIP31C 45 214930 20 2N5777 45 , 33, CARDIFF ROAD, WATFORD,.HERTS WD1 8E0, ENGLAND AC127/8 35 13C308E1 18 BFX85/86 35 71P32A 43 2N1131/2 40 2146027 32 1 AC141/2 35 BC327/8 15 BFX87/88 28 11P32C 45 2N1303/4/5 2146109 60 Tel. Watford (0923) 40588. Telex: 8956095 WAELEC AC176 35 BC337/8 15 BFY50/51 30 1IP33A 70 2141307 70 2N6290 70 AC187/8 35 8C441 34 BEY52 30 1IP33C 75 2N1613 30 25A636 250 OR DERS NOR M ALLY DESP ATCHE D BY OF POST RETURN AC188 35 8C461 34 BFY53 35 11P34A 85 2N1671B 160 254671 250 A0142 120 6C477/8 40 BEY55 35 11P34C 105 2N2160 325 2SA715 75 A0I49 79 5C516/7 40 AU. DEVICES BRAND NEW. FULL SPEC. AND FULLY GUARANTEED. SEND CASH, P.O.'s OR CHEQUE BP/56 35 1IP35A 120 2N2219A/20A/ 25C495/6 85 WITH ORDER. GOVERN MENT AND EDUCATIONAL INSTITUTIONS OFFICIAL ORDERS ACCEPTED 13FY64 40 1IP35C 130 21A/22A 25 25C1061 250 VM I2 9542 58C54C549C718 12 15 (ACCESS ORDERS BY TELEPHONE 0923-50234). TRADE AND EXPORT INQUIRY WELCOME. P & P BFY90 80 1IP364 130 2142369A 18 25C1096 85 25C1162AFI39 45 40 5C556/7 15 BRY39 50 1IP36C 140 2N2646 45 ADD 70p TO ALL CASH ORDERS. OVERSEAS POSTAGE AT COST. PRICES SUBJECT TO CHANGE. AF239 55 5C5 15 B5X20 30 11P41A 50 2N2846 80 25C1172/3 125 ige Export orders no VAT. U.K. customers please add 15% VAT to total cost incl. p&p. 5C107/8 12 BCY41/42 30 5SX29 45 19415 52 2N29044/054/ 2SC1306 100 VA 1 We stock thousands more items. It pays to visit us. We are situated behind Watford BC107B 14 BCY70 18 BSY26 35 TIP42A 55 064/07A 26 2SC1307 150 Football Ground. Open Monday to Saturday, 9.00am to 6.00pm. Ample FREE Car parking. BC108B 14 5CY71 20 BSY95 35 1IP425 58 21429260 10 25C1449 95 BC108C 14 BCY72 25 5U105 180 11P120 70 2N3053 25 25C1679 190 POLYESTER RADIAL LEAD CAPACITORS: 250V; 10n, 20n, 15n, 22n, 27n 6p; 33n, 47e, 68n, 100n 8p; 150n, 5C109 12 8CY78 30 5U205 190 1IP121 73 2N3054 55 25C1678 140 220n 10p; 330n, 470n 15p; 680n 19p; 10 23p; 1p5 40p; 22 46p. BC1095 14 50131/2 65 B0206 200 11P141 120 2N3055 50 2SC1923 65 BC109C 14 8D133 60 BU208 200 11P142 120 2143442 140 25C1945 225 ELECTROLYTIC CAPACITORS (Values in on, 500V; 105 F 52p; 47 7gp ; 63g ; 947, 1-0,1.5, 2-2, 3-3, ills; 47 BCI14/5 30 50135 45 MJ2955 90 1IP147 120 2N3615 199 25CI953 90 9P; 10 10 P: 15,22 12P; 33 15p; 47 12p; 68 16p; 100 19p: 22026p; 1000 70 P; 2200 99p; 50V: 6820p; 100 BC117/8 25 50136/7 40 MJ5340 54 11P2955 70 2N3663 20 25C1957 90 17p; 220 24p; 40V: 68 1 89; 22 9P; 33 12 P: 330 , 470 32 P: 1000 48p; 2200 90p; 25V: 4,7, 10, 22, 47 8p; 100 5C140 38 50138/9 40 MJ5371 100 11P3055 70 2N3702/3 10 2SC1969 165 11p; 150 12p; 220 15p: 33022p; 470 25p; 680. 100034p; 1500 42p; 2200 50p; 3300769; 470092p; 16V: 5C142/3 38 50140 40 AAJE2955 99 71543 50 2N3704/5 10 2SC2028 85 2.5, 40 8p; 47.68, 1009p; 125 12p; 220 13p; 330 16p; 470 20p; 680349; 1000 27p; 1500 31P: 220036p; 4700 BC147/8 12 50158 60 mjE3055 70 11544 45 2143706/7 10 25C2029 200 79p. BC1475 15 BD245 65 MPF102 40 715884 50 2143708/9 10 2SC2078 170 5C148C 10 50434 70 MPF103/4 30 T1590 30 2143710 10 25C2091 85 TAG-END TYPE: 6491: 4700 245p; 3300 198p; 2200 POTENTIO METERS: Carbon Track, BC149 12 80695A 150 MPF105 30 1IS91/93 32 2N3771 179 25C2166 165 LW*: Si110,229 1.944-....M0P 110p,- 405: 4700160p; 2511: 025W Log & Linear Values. 8C149C 15 506964 150 MPSA05 30 VK1010 99 2143772 195 2SC23I4 85 47IX Y 98p; 10.000 320p; 15,000 345p. 8C153/4 30 BF115 45 MPS406 25 VNIOKM 70 2143773 210 2SC2335 200 500W, 1K & 2K (UN ONLY) Single 3.5p BCI5718 14 ElF154/13 30 MPS408 30 VN46AF 95 2N3819 35 2SC2465 125 TANTALU M BEAD CAPACITORS: ' 5K0-2MI-1 single gang 3. P 5CI59 11 5E167 35 MPSA12 32 VN66AF 110 2N3820 60 25C2507 40 5K0-2M0 single gang D/P switch ,95m P _ 351/: 0.10, 0,22, 0.33 15p 047, 0.68, 1-0, 1-5 16p 2.2, 3-3 18p 4.7, 8CI67A 14 5E173 35 MPSA55 30 VN88AF 120 2N3822/3 60 2SC2612 200 5K0-2M0 dual gang stereo .. P 58 22p 10 28p 1891: 22,33, 16p 4.7, 58, 10 18p 1536p 22 5C168C 12 8E177 36 MPS456 30 VN89AF 120 2143866 90 250234 75 36p 33, 47 50p 100 95p 220 100p 1091: 15, 22 26p 33, 47 5C169C 12 BF178 35 MPS470 40 ZTX107/8 12 2143903/4 15 25K45 90 SLIDER POTENTIOMETERS - 50p 100 75p. 5C171/2 12 5E179 40 MPSUO2 58 Z1X109 12 2143906/5 15 2SK288 225 025W log and linear values 60rnm track BC173 15 13E194/5 12 MPSUO5 60 ZTX2I2 28 2144037 60 25J83 225 51(0-5001(0 Single gang 30 P SILVER MICA (pf) SIEMENS mulitlayer miniature 8C177/8 18 13E198/9 18 MPSUO6 60 Z7X300 13 2N4058 15 25J85 225 2, 31, 47, 6.8, 8-2, 10, 12, 18, capacitors. 5C179/81 20 13E200 30 MPSU52 65 ZTX301/2 16 2144061/2 15 314128 115 22, 27, 33, 39, 47.50, 56,68,75, 250V: 1nF, 1n5, 2n2, 3n3, 447, PRESET POTENTIO METERS 8C18I 30 8E224 40 MPSU55 60 ZTX303 25 2N4264 30 3N140 115 0-1W 500-2-2M Mini Vert. & Horiz. 89 82. 85, 100, 120, 150. 180 15P. 6n8, 8,12, 10 n, 150, 22 n 7p; 18n, 5C182/3 10 BF244A 28 MPSU56 60 ZTX304 17 2144286 25 40251 150 220. 250, 270, 330, 360, 390, 27n, 33n, 078 69; 39n, 56n, 68n 0-25W 220<3/4m7 Vert. & Hone. 12p BC184 10 BF2448 29 0C23 170 Z1'X320/26 30 2144269 25 40311 60 470, 600, 8005 820pF 21p. 9p, 00nF 11p. 13C1821 10 BF245 50 0C28/36 220 ZTX500/1 14 2144400 25 40313 130 1000, 1200, 1800 30p each 100V 100n, 120n, 10p; 150n 11p; RESISTORS Hi-stab, Ministure, 5% BC183L 10 5F256B 50 0C41/42 75 ZTX502/3 18 2N4427 80 40361/62 70 3300, 4700 60p each 2206 139; 3300 18p; 4700 23p; Carbon. 5C1841 10 5E257/8 32 0070 40 ZTX504 25 2N4859 78 40408 76 6130n 30p; IMF 34p; 2M2 50p. RANGE Val. 1-99 100+ 13C186/7 28 I3F259 40 0072 50 ZTX531 25 2N5135 30 40412 90 025W 202- 4M7 E24 39 I p 5C212/3 12 BF394 40 0075/76 55 Z1'X550 25 2N5138 25 40467 130 CERAMIC Capacitors: 50V POLYSTYRENE Caps: 06W 202- 4-M7 512 3p 1p 5C2121 10 5E451 00 0076 50 2N696 30 2N5172 25 40468 85 Range 1pF to 6800pF 49; lOnF, 10pF to 1nF Sp 1W 2(72- 10M E12 6p 49 5C2131 12 5E494/5 40 0081/82 50 214697 23 2N5180 45 40594 105 15n, 33n, 47nF 5p; 100nF/30V 7p. 1n5 to 12nF 10p 1% Metal Film 510-1M524 Sp 6p 5C214 10 8E594/5 30 0083/84 70 214698 40 2N5I9 75 40595 110 5C2141 12 5FF139/40 25 TIP29A 32 2N699 48 2N5194 80 40603 110 RESISTORS S.I.L. Package: 7 Commoned, 1000, 4700, 6800, IK 2K2, 41(7, 10K, 47K, 100K 24p. 5C237/8 15 5ER41/79 25 TIP29C 38 2N706A 25 2N5305 r 24 40673 70 8 Corrirnoned: (9 pins) 1500, 1800, 2700, 3300, 3300, IK, 21(2, 4K7 6K8, 10K, 22K, 47K, 100K 26p. 5C3075 15 EIF580/81 25 TIP30A 35 214708 25 2N5457 30 40871/2 90

LINEAR IC's SA54209 595 ZN428E 450 8216 200 1M59914 895 745260 70 7453 30 74196 120 L583 70 L5320 210 4035 70 4519 32 5G3402 295 ZN429E-8 245 8224 £3 1M59927 £14 74S262 f10 7454 30 74197 100 1S85 80 LS322 360 4036 275 4520 53 555 CMOS 95 LM334Z 160 5L490 350 ZN459 246 8226 £3 1M59928 IMO 745274 00 7460 30 74198 200 LS86 35 LS323 360 4037 115 4521 115 702 75 LM335 135 S1924 00 ZN10345 200 8228 270 1MS9929 £16 745275 00 7470 50 74199 200 LS90 50 15324 150 4038 75 4522 125 709C Spin 35 1M337 275 516270 170 ZN1040E 695 8243 425 7M59980 £20 745280 00 7472 50 74221 200 1591 90 L5325 150 4039 280 4526 60 710 48 1M339 40 5N76013N 350 ZNA234E 925 8250 Ell 1M59995 £12 745281 00 7473 50 74246 130 1S92 55 1S326 290 4040 60 4527 65 741 16 LM348 60 SN76033 350 8251 500 ULN2003 75 705283 00 7474 45 74247 120 1S93 59 LS327 290 4041 57 4528 70 747C 14 pin 70 LM349 125 51476488 525 1• g 8253 585 UPD7002 725 745287 200 7475 55 74248 145 1595 70 L5347 120 4042 50 4529 150 748C 8 pin 30 LM358 50 SP0256AL 625 8255 600 UPD7007 725 745288 180 7476 45 74249 175 1S96 90 L5348 140 4043 42 4530 90 753 8 pin 185 1M377 210 1A7120 140 IC's 8256A £15 W01691 £14 745289 200 7480 60 74251 90 LS107 45 L5352 110 0044 50 4531 130 810 159 LM379 495 747130 125 8257A 400 W01770 £19.95 74S299 540 7481 175 74259 150 1S109 45 L5353 110 4045 110 4532 65 9400CJ 375 LM380 120 747204 150 21021 160 8259 1(7 WD2143 850 745301 350 7482 100 74265 280 15112 45 LS355 220 4046 60 4534 400 A000808 885 LM381N 175 747205 90 2114 325 8271 POA Z80CPU 2-5 300 745365 250 7483 100 74273 180 L5113 40 15356 200 4047 60 4536 275 AY-1-1320 225 LM382 200 1A7222 150 2147-3 425 8272 1(25 Z8OACPU4M 376 740373 375 7484 105 74276 130 LS114 40 15363 150 4048 55 4538 80 AY-1-5050 99 LM384 225 1A7310 00 2516 350 8279 750 280ACTC 320 74S374 375 7485 100 74278 160 15122 70 L5364 150 4049 38 4539 90 AY-1-5051 160 LM386 90 TAA900 395 2532-4 400 8282 450 2808 £11 745412 380 7486 40 74279 80 LS123 100 L5365 50 4050 35 4541 95 AY-1-6720 210 LM387 200 T4A621 296 25L32 450 8283 450 2800ART 795 745470 325 7489 200 74283 100 LS124 125 LS366 50 4051 70 4543 70 AY-3-8910 390 LM389 160 744661 190 2564 700 8284 550 280ADART 820 745471 600 7490 60 74284 440 1S125 80 L5367 50 4052 60 4544 150 AY-3-8912 500 1M393 85 744700 275 27108 450 8288 £11 280ADMA 900 745472 400 7491 70 74285 300 L5126 SO 1S368 50 4053 60 4549 400 AY-5-1317A 630 LM394CH 385 TAD100 159 2716-5V 350 8748 £45 2800MA 795 745473 00 7492 70 74290 80 1S132 60 15373 100 4054 85 4553 245 c.83011 130 LM55a 170 18A1205 70 2732 £4 8726A 99 280P10 300 745474 400 7493 50 74293 80 15133 50 LS374 100 4055 85 4554 180 C83012 175 LM725CN 300 TBA500 275 2764-250 475 8727 150 280AP10 325 74S475 425 7494 100 74297 175 L5135 28 L5375 70 4056 85 4555 35 CA3014 275 LM733 65 TBA5500 330 27C64 1095 8731 350 280S10-1 850 745571 300 7495 60 74298 160 15136 50 L5377 130 4057 £10 4556 55 CA3018 86 1M1871 300 TBA64I 290 26501 75 8795N 90 280A510 900 745573 450 7496 75 74351 180 L5138 60 1S378 110 4059 435 4557 250 CA3019 90 LM1889 350 TBA651 190 27128/250n £16 879714 90 280AS10-2 £9 7497 200 74365 70 L5139 60 15379 130 4060 68 4558 120 CA3020 210 1M2907 395 188800 80 256K DRAM £49 9364AP 550 28002CPU 00 75 74100 175 74366 70 LS145 115 1S380 310 4061 ES 4559 395 CA3023 210 LM3900 70 TBA810S 95 3242 675 9602 220 74S n ,nm 74104 70 74367 70 L5147 165 1S382 310 4062 995 4560 160 CA30284 130 LM3909 85 TBA820 SO 4027 95 AM26LS31C 125 .,7!,13,,,7/81. n‘," 74105 70 74368 70 151 48 130 LS384 460 4063 85 4561 104 CA3035 255 1M3911 185 T8A9200 200 4116 140 AM261532A 125 74500 40 '.". 74107 45 74376 120 LS151 70 1S385 330 4066 45 4562 350 C83036 270 LM3914 300 TBA990 350 4164-150 425 AM26L533 150 74502 40 75121 ..r. 74109 70 74390 100 LSI53 70 1S386 50 4067 245 4566 165 CA3043 275 LM3915 385 TCA270 350 4416-2 475 AM7910 £30 74503 40 .,75 ,.c,,33 = 74110 55 74393 100 L51 54 200 1S390 80 4068 25 4568 250 CA3045 365 1M3916 300 TCA280A 220 4532-3 250 AY-3-1015 300 74504 40 .,'-','„,.'' ...... , 74111 65 74425 60 LS155 70 1S393 100 4069 25 4569 175 CA3046 70 1M13600 150 TCA940 175 0815.10Ons 185 AY-5-1013 300 74505 40 . ,' , ' ra . 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Z. . , ' ‘ , , . ,- . 74122 86 -2,45 150 15163 70 1S465 140 4077 25 4585 70 62641,15 f19 DP8303 450 70530 60 74123 75 C m ft , 1S164 80 15467 120 4078 25 4599 155 CA3086 60 MC1204 250 TDA1034 350 7536 1 00,... " n CA3089E 200 MC1301 90 10A1054 00 63403 £14 DP8304BN 350 74S22 40 . ,' .Q ' 4 , . , ,. . 74125 60 C374 425 LS165 110 1S490 150 4081 25 40097 45 CA3090A0 375 MC1303 98 10A1490 350 6402 350 0S3647 00 74530 40 ' • ' . . ' X X 74126 60 , , , , ., 4 ,g L5166 150 1S540 140 4082 25 40098 42 C83123 165 MC1304P 260 1082002 325 6502 CPU 355 0S3691N 495 74032 50 L 53, ,L . X X 74128 55 C-9-2-3- 0-4 1S168 140 15501 140 4085 60 40100 215 C83130 90 MC1310P 150 TDA2003 250 6502A 545 1358820 110 74537 50 4nr,,,, r, 74132 70 reog p., L5169 125 L5624 155 4086 60 40101 130 CA3140 50 MC1445 250 TDA2004 300 6503 650 0S8830 135 74S38 70 4,nc .,,..c ..n.... 74136 50 ---- - LSI70 160 LS629 130 4089 125 40102 140 CA3160 95 MC1455 50 1082006 330 6504 600 0S8831 125 74S40 40 ,c,."m.. 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184422 320 NE556DB 65 U1N2803 190 6854 750 MM52800 695 745174 250 7426 40 74174 100 1S32 50 1S257 75 4016 40 4490 450 _1- 1C7120 300 NE558 170 UPC556 00 68854 800 MM5303 635 745175 300 7427 35 74175 100 1533 25 15258 75 4017 80 4500 395 ... . 1C7130 320 NE560 350 UPC575 275 6875 500 MM5307 1275 745181 00 7428 35 74176 100 1S37 25 LS259 125 4018 60 4501 38 1C7137 350 NE5625 410 UPC1025H 375 68000 £25 MM53874 885 745182 00 7430 25 74177 110 1S38 30 1.5260 70 4019 58 4502 60 1F347 150 NE564 420 UPC1156H 295 8035 525 MM58174 875 745188 200 7432 30 74178 130 1540 25 1S261 100 4020 90 4503 40 1542 55 1F351 70 NE565A 120 UPC1181 00 80808 400 RO-3-2513L 700 745189 225 7433 30 74179 130 15266 60 4021 58 4504 99 JUST 1S47 90 4505 385 1F353 90 NE566 155 UPC1182 425 80858 600 80-3-2513U 650 745194 280 7437 30 74180 100 15273 120 4022 67 PHONE 1548 90 LF355 90 NE567 140 UPC1366 195 8088 £15 58.45050 875 745195 276 7438 40 74181 300 15275 350 4023 30 4506 100 YOUR 1549 100 4024 50 4507 45 LF356 90 NE570 410 XR2206 375 811S95 140 SFF96364E 800 745196 00 7440 30 74182 120 15279 70 ORDER, 1F357 100 NE571 400 XR2207 400 811S96 170 SP0256AL2 495 745197 300 7441 90 74184 170 1551 30 LS280 185 4025 22 4508 130 1F398 495 NE5532 150 XR2211 575 81LS97/98 140 TCM3101J £13 745201 250 7442 65 74185 170 1S52 25 1S283 80 4026 90 4510 55 THWEERDOEST. 1N110 325 1455534 160 X112215 676 8123 180 054S2716-3 725 74S225 600 7443 150 74186 79 1S54 30 15290 80 0027 48 4511 55 0023 LM3014 30 0M335 650 X52266 360 8131 475 1M54047 100 745226 500 7444 100 74188 78 1555 30 1S292 850 4028 45 4512 55 00234 LM307 45 5C41360 60 ZN414 SO 8154 750 TM54164-15 395 745240 376 7445 110 74190 120 1S63 55 15293 80 4029 75 4513 150 1M308 75 6C4558 60 ZN423E 130 8155 500 1M54416-2 595 745241 375 7446 110 74191 120 1573 30 LS294 999 4030 35 4514 115 1M311 60 S5668 225 ZN4245 130 8156 000 TMS45004 £12 74S244 474 7447 95 74192 120 1S74 35 1S295 140 0031 130 4515 125 t p k l 1M318 150 SAB3209 425 ZN4255-8 345 8202 £25 1M54532-3 350 745251 225 7448 110 70193 120 1S75 45 15297 850 4032 70 4516 65 I 1M319 180 S883210 325 ZN426E-8 200 8212 £3 TMS5100 600 745257 225 7450 30 74194 100 1S76 40 1S298 100 4033 130 4517 276 1M324 45 5A83271 485 ZN4275-8 620 8214 495 TMS6011 500 745258 225 7451 30 74195 75 1578 40 1S299 226 4034 140 4518 48 SPEAKERS OPTO 0.5" LCD VOLTAGE REGULATORS OIL DISPLAYS 80, 0 3W, 2'; 2 25 , 2 5 LEDS price includes Clips 14 T0220 Plastic Casing SOCKETS 80p 31/2 digit 495 TIL209 Red 3mm' 10 r ve ye Low Wire 03W, 25 400, 640 or 4 digit 530 TIL211 Green 3mrn 14 5V 7805 45p 7905 55p profile wrap SPECTRU M 800 80p 6 digit 625 TIL212 Yellow 14 12V 7812 45p 7908 55p 8 pin 8p 25p TIL220 .2" Red 12 15V 7815 45p 7912 55p 14 pin 10p 35p DIODES BRIDGE 0-2" Yel, Grn, Amber 14 OPTO 18V 7818 45p 7915 55p 16 pin 10p 42p 32K UPGRADE AA119 15 RECTIFIERS BPX25 250 Rectangular LEDs with 24V 7824 45p 7918 55p 18 pin 16p 52p AA129 20 (plastic case) two part clip. 8,0 & Y 45 BPW21 320 100 m4 T092 Plastic Casing 20 pin 20p 60p AAY30 15 BPX65 320 1A/50V 18 Rectangl. Stackable by 78L05 30p 79L05 50p 22 pin 22p 65p Upgrade your 16K Spectrum to full BA100 15 1A/100V 20 LEDS 18 ILD74 145 6V 78L62 30p 24 pin 25p 70p BAX13 20 IL074 275 48K with our RAM Upgrade Kit. Very 1N400V 25 Triangular LEDs R&G 18 8V 78L82 30p 28 pin 28p 80p BY100 24 ILCT6 Darlington 1A/600V 34 0-2" Flashing LED Red 58 12V 78L12 30p 79L12 50p 40 pin 30p 99p simple to fit. Fitting instructions BY126 12 Isolator 135 2A/50V 30 0-2" Br colour LEDs 15V 78L15 30p 79L15 50p BY127 14 TIL111 70 2A/200V 40 Red/Green 100 ZIF TEXTOOL supplied. ONLY £22 CR033 250 OCP71 120 2N400V 46 Green/Yellow 80 ICL7660 248 LM317K 250 OIL SOCKET 0A9 40 ORP12 78 2N600V 65 0-2" Tr, colour LEDs 78H05 5V/5A 550 LM317P 99 24 way 575p IDC CONNECTORS (Speed block type) 0A47 255777 50 6N 100V 83 Red/Green/Yellow 85 78H12 12V/5A 640 LM323K 500 28 way 695p 0A70 4533 135 PCB Male Female Female 6N400V 95 0-2" Red High Bright 59 78HG f 5 to LM3377 175 40 way 845p 0A79 1 Pin diode 720 with latch Header 6N600V 125 High Bright Green or + 24V 5A 599 LM723 30 Card-Edge 0A81 Schmitt 2 rows Stn. Angle Socket 2 10A/200V 215 Yellow 100 79H0 -2.25V to TBA625B 75 OIL PLUGS (Headers) Connector 0485 1 Receiver 715 Pins Pins 10N600V 298 LD271 Infra Red (emit/ 46 - 24V 5A 685 RC4194 375 Pins Solder IDC 0A90 10 way 90p 99p 85p 120p 25N200V 240 TIL32 Infra Red (emit) 52 LM309K 120 RC4195 160 14 38p 95p 0A91 OPTO 16 way 130p 150p 110p 195p 25A/600V 395 0FH205 (detector/ 118 78540 225 16 42p 100p SWITCH 20 way 145p 166p 125p 2409 0A95 BY164 56 TIL78 (detector) 55 24 88p 138p 0A200 26 way 175p 200p VM18 50 TIL38 50 Reflective 28 185p 290p 150p 320p 34 way 0A202 TIL81 82; TIL100 90 TIL139 225 S WITCHES 40 195p 218p 205p 236p 169p 3409 15914 Slotted similar SLIDE 250V TOGGLE 2A 250V 40 way 220p 250p 190p 420p 15916 to RS 186 14 DPDT 14 SPST 35 RIBBON CABLE 50 way 235p 270p 200p 470p ZEN ENS 7 Segment Displays 154001/2 1A DPDT CJOFF 15 DPDT 48 (price per foot) Range: 2V7 to TIL321 5' C.An 140 154003 ALU M.BOXES I/2A DP oNon/on 40 4 pole on off 54 1Nays Grey Colour 39V 400m W TIL322 5" C.th 140 154004/5 40211202" 100 10 15p 25p SPECIAL 10 • 8p each DL704 -3" C.Cth 125 154006/7 402 3/4 02 1/2 103 16 20p 30p OFFER Range. 3V3 to DL70) -3" C.Anod 125 PUSH BUTTON 154148 40402 1/2" 120 SUB-MIN 20 259 40p 2764 - 250ns £4.75 £4.35 33V 1-3W FND357 or 500 130 Spring loaded 155401 5<402" 105 TOGGLE 2 amp 26 40p 65p 27120- 250ns £16.00 £14.00 15p each -3" Green C.A. 140 Latching or 155404 5x23/4 01 1/2" 90 SP changeover 64 34 50p 80p 6116LP - 1550s E3.75 £3.40 31 3 Red or Green 150 Momentary 6A 155406 5/.2 3/4 02 12130 SPOT on off 58 40 60p 90p 6264LP - 150ns £19.00 £18.00 Bargraph 10 seg. Red 275 SPOT clover 150 155408 50401 12" 99 SPDT doff 85 64 90p 125p Bargraph 55M3914 DPOT clover 200 1544 VARICAPS 500 50402 1/2" 120 SPOT Biased 105 10921 BA102 30 60402" 120 DPDT 6 tags 80 FERRIC CHLORIDE 'D' CONNECTORS TRANSFORMERS (mains Prim. 220-240V) 6A/100V 4 BB105B 40 60403- 150 MINIATURE DPDT C/OFF 88 Pins 9 15 25 37 3.0-3V, 6-0-6V 100mA 130; 8 0-9V 75mA; 6A/400V 5 BB106 40 70503" 180 Non Locking DPDT orVon/on 185 Crystals llb way way way way 12 0.12V 751nA; 15 0-15V 75mA. 98p 6A/800V 6 80603' 210 Push to make 15p DPDT Biased 145 195p 50p p&p 6VA: 2 x 6V-5A; 2<9V-4A, 2x 12V-0. 3A; 1004 1/4 <3 240 Push break 25p 4-pole 2 way 220 M ALE 2 - 15V-25A 250p 1007.3 275 ROTARY: (Adjustable Stop Type) DAL ETCH RESIST Solder 80p 110p 160p 240p 12VA: 2.4V5-1. 34; 2.6V-1.2A; 2' 12V.54, TRIACS 120503 260 1 pole/2 to 72 way, 2p/2 to 6 way, 3 pole/ Angle 150p 210p 250p 355p 3A/100V 48 Pen plus spare Pp 1043p 120803' 295 2 to 4 way, 4 pole/2 to 3 way 48p 2. 15V-4A 3459 135p p&p/ SCR's Strait 170p 160p 220p 310p 3A/400V 56 24VA: 6V-15A 6V-1. 5A; 9V-1- 2A 9V-124; Thyristors 12V-1A 12V-1A; 15-84 15-84; 20V-6A 3A/800V 85 COPPER CLAD BOARDS ROTARY: Mains 250V AC, 4 Amp 64p 0 8A 100V 32 FEMALE 20V-64 385 (60p p&p/ 5A/300V 38 8A/100V 60 Fibre Single- Double' Solder 105p 160p 200p 338p 50VA: 2.6V-4A; 2, 9V-2 5A; 2 • 12V-2A; 2, 15V. 5A/400V 40 8A/400V 69 Glass sided sided DIP SWITCHES: ISPOT) 4 way 65p; Angle 165p 215p 290p 440p 1 5A; 2-20V-1- 24; 2, 25V-24; 2 x 30V-0- 8A 5N600V 443 8A/800V 115 100p 125p 6 way 80p; 8 way 87p; 10 way 100p; Strait 175p 200p 3009 4209 520p 160p p&p) 124/100V 78 6" , 12" 175p 225p (SPOT) 4 way 190p. 8A/300V 60 100VA: 2.12V-4A; 2.15V-34; 2.20V-2. 5A; 8A/600V 95 124/400V 82 COVERS 80p 75p 75p 90p 2 30V.1. 5A; 2040V'1 , 254; 2.50V-1A 12A/100V 78 1240800V 135 VEROBOARDS 0.1" A MPHENOL CONNECTORS IDC 75 way Pig 385p, SO 450p 965p 160p p&p/ 124/400V 95 1640100V 103 Clad Plain 'VC!' Board 180 IDC Solder 12408000 188 1640400V 105 21/2 03 3/4 ' 95 - 'DIP' Board 395 24 way IEEE 475p 4709 EDGE CONNECTORS TURNED PIN Low Profile BT106 150 16A/800V 220 21+205' 110 - Vero Strip 144 36 way Centronix 525p 475p 1 Professional DIL SOCKET BT116 180 25A/400V 185 33/4 x 33/4" 110 - 24 way Female 490p 450p 2018 way 210p 8 pin 25p 22 pin 70p C106D 38 2540800V 295 33/4 v5" 125 959 PROTO-DECs SIL 2x22 way 215p 14 pin 40p 24 pin 72p T)C44 24 25N10000 33/4 017" 4202759 Veroblock 480 ASTEC UHF MODULATORS Sockets 2<23 way 175p 16 pin 42p 28 pin 90p TIC45 29 480 43/4 018" 590 - S-Dec 395 6MHz Standard 375p 0 1' 2025 way 18 pin 47p 40 pin 120p TIC47 35 304/400V 525 Pkt. of 100 pins 55p Eurobreadboard 590 8MHz Wideband 550p 2859 20 way 20 pin 60p 255064 38 72800D 125 Spot Face Cuner 150p Banboard 1 695 2028 way 1909 65p 2039 way 2N4444 130 Pin Insertion Tool 185p Superstrip SS2 £13 A NTEX Soldering Irons 310p 32 way 2>36 way 3609 JUMPER LEADS Cl SW 535p 959 2<40 way 380p IDC FEMALE RECEPTACLE Jumper Leads 36 SOLDERCON VERO WIRING PEN and Spool 380p G51 7W 545p PINS 2043 way 450p 20pin 26pin 34pin 40pin Spare Wire (Spool/ 75p; Combs 6p ea. 018 W 550p 1 end 160p 200p 260p 300p DIAC 100 45p 2x75 way 650p Wire Wrapping Stakes 100 250p XS25W 560p 2 ends 290p 370p 480p 525p ST2 25 500 370p

Plastic Library CRYSTALS BBC MICROCO MPUTER COMPUTER CORNER 32-768KHz 100 DISC STORAGE 100KHz 575 • EPSON RX80 Printer £209 CASES 200KHz 370 SPECIAL OFFER THIS MONTH ONLY £315 455KHz 370 We stock the full range of BBC Micro peripherals, Hardware • EPSON RX80 F/T Printer £219 Holds ten 5/14 " Diskettes .£1 .80 1MHz 275 1.008M 275 & Software like, Disc Drives (Top quality Cumana & Mitsubi- 1.28MHz 450 shi), Diskettes, Printers, Printer Paper, Interface Cable, Dust • EPSON FX80 Printer £316 DISC ALBU MS 1.5MHz 420 Covers, Cassette Recorder & Cassettes, Monitors, Connec- 1.6MHz 595 Attractively finished in beige 1.8MHz 545 tors (Ready made Cables, Plugs & Sockets), Plotter (Graphic • EPSON FX100 Printer £429 leather-vinyl, these convenient- 1.8432M 250 Tablet) EPROM Program mer, Lightpen Kit, Joysticks, ly store up to 20 discs. Each disc 2.0MHz 225 • SEIKOSHA GP100A £122 2.4576M 200 Sideways ROM Board, EPROM Eraser, Machinecode ROM, can easily be seen through the 2.5MHz 225 The highly sophisticated Watford's 16K BEEB DES, WORD- clear view pockets. 2.56250M 220 • KAG ATTAXAN KP810 Printer £242 3.2768M 150 WISE, BEEBCALC, Software (Educational Application & ONLY £4.25 3.57954M 98 Games), BOOKS, etc. etc. Please send SAE for our descrip- • KAGA/TAXAN KP910 Printer £332 3.6864M 300 tive leaflet. 4.0MHz 150 51/4" Disc Drive 4032MHz 290 • BROTHER HR15 Daisywheel Printer £329 4-194304M 200 HEAD CLEANING KIT 4433619M 100 DISC DRIVES FOR BBC MICRO 4,600151Hz 200 • CS100 - TEC Cased with own Power Supply, S/ • Centronics PRINTER CABLE for all the above £12 4.80MHz 200 printers to interface with the BBC Micro £7 5.0MHz 160 S,40 track, 51/4", 100K £119 SPECTRU M 5-165MHz 300 524288M 390 • CD200 - TEC Twin Cased with own PSU, S/S, CENTRONICS/RS232 6.0MHz 140 • KAGA - RGB 12 inch medium resolution colour 15144MHz 150 40 track, 51/4", 200K £236 monitors £195 PRINTER INTERFACE 65536MHz 200 7,0MHz 150 * It was the first! 7-169MHz 250 • EPSON Single Cased with own PSU, D/S, 40 • ZENITH 12" Hi-RES, Green Monitor 40/80 It is still the best! 7,68MHz 200 track, 51/4", 200K £149 column select switch, value for money. £68 8.0MHz 150 8.08333M 395 * Centronics and BI-DIRE CTIO N AL 8.867237M 175 • EPSON Twin Cased with own PSU, D/S, 40 track, • MICROVITEC 14" colour monitor. RGB input. RS-232 with full hand-shaking, 900M1-1, 200 51/4", 400K £299 Lead incl. £165 0375MHz 350 10-0MHz 175 * Obeys SPE CTR U M LUST and • MICROVITEC 1451 Hi-res 14" Monitor incl. 105MHz 250 • MITSUBISHI 51/4" Slim line Disc Drives double LPRINT. 10.7MHz 150 . Lead £250 10.24MHz 200 sided, double density, track density 96 TPI, track to * Split-Speed Operation for RS-232. 12.0MHz 175 track access time 3msec. 12.528MHz 300 • QL RGB MONITOR, medium resolution £239 (Use it to com municate with 14 ,31818M 170 the BB C MICR O or O THER 14.7456KA 175 • SINGLE MITSUBISHI Slim line - Cased with • TEX EPRO M ERASER. Erases up to 32 ICs in PERIPHE R ALS). 14765MHz 250 own PSU, DS/DD, 1 Megabytes (400K with , 15-30 min. £30 150MHz 240 16.0MHz 220 *Interface 1, Interface 2 & Microdrive BBC) £165 18.0MHz 180 • Spare 'UV lamp bulbs £8 compatible. 18-432M 150 • TWIN MITSUBISHI Slim line - Cased with own 19.968MHz 150 • C12 COMPUTER Grade BASF Cassettes in * Configuration progra m creates 20.0MHz 260 PSU, DS/DD, 2 Megabytes (800K with BBC) £339 24.0MHz 170 custo mised M/C driver to suit your Library Cases 36p 24.930MHz 325 printer. 29485MHz 150 51 /34 " Disketies (Life Time Warranty) • 8/12 " or 9/12 " Fan fold paper 11000 sheets) £7 (150p) 26.670M1-9 325 • 10 3M Diskettes S/S D/D £14 * HI-RES screen dumps in 2 sizes 27.125MHz 295 on EPS O N, SEIK OS H A, 27 ,145M 190 • Teleprinter Roll no VAT) £4 27.648MHz 300 • 10 3M Diskettes D/S D/D £22 ST AR, SHININ A, M AN NES M AN 38.66667M 240 , MANY MORE PRINTERS, MONITORS, INTERFACES, T ALLY, NE C, FUTE M A N, K A G A, 480MHz . 240 Many more types available. etc. This is a ST A N D AR D 55.5MHz 400 AVAILABLE. CALL IN AT OUR SHOP FOR DEMON- 100MHz 295 Please send SAE for our detailed leaflet. FEAT URE! Not an extra. STRATION OR WRITE IN FOR OUR DESCRIPTIVE 116.0MHz 300 N.B. Carriage is extra on drives. LEAFLET. 145.8MHz 225 * Compatible with T ASIN OR D T W O and most professional progra ms. (P&P on some of the above items is extra) Call in at our shop for demonstration of any of the Price: £29.95 (Carr. £11 WATFORD ELECTRONICS , above items. Be satisfied before you buy. Centronics Cable EV Tel. (0923) 40588 Telex. 8956095 DISHED WASHER

TOROIDALS OUTER INSULATION The toroidal transformer is now accepted as the standard in industry, overtaking the obsolete laminated type. Industry has NEOPRENE been quick to recognise the advantages toroidals offer in size, SECONDARY WASHERS weight, lower radiated field and, thank to I.L.P., PRICE. WINDING

Our large standard range is complemented by our SPECIAL INSULATION DESIG N section which can offer a prototype service within 14 CORE DAYS together with a short lead time on quantity orders which PRIMARY can be program med to your requirements with no price penalty. WINDING END CAPS

15 VA 50 VA 120 VA 225 VA 500 VA 62 x 34mm 0354 80 x 35m m 0.9Kg 90 x 40m m 1.2Kg 110 x 45m m 2.2Kg 140 x 60m m 4Kg Regulimon 197. Regulation 13% Regulation 11% Regulation 7% Regulation 4% W hy a Toroid? SERIES SECONDARY RMS 2x010 6+6 4.16 4 x010 6+6 10.00 6x012 12+12 9.38 8x016 25+25 10.00 * Smaller size & weight to meet No. Volts Current 2 x011 9+9 2.77 4x011 9+9 6.66 6x013 15+15 7.50 8x017 30+30 8.33 modern 'slimline' requirements. 4x012 12+12 5.00 6 x014 18+18 6.25 0 x010 6+6 1.25 2x012 12+12 2.08 8x018 35+35 7.14 • Low electrically induced noise 0 x011 9+9 0.83 2 x013 15+15 1.66 4x013 15+15 4.00 6x015 22+22 5.11 8x026 40+40 6.25 demanded by compact 0 x012 12+12 0.63 2 x014 18+18 1.38 4x014 18+18 3.33 6x016 25+25 4.50 8x025 45+45 5.55 0 x013 15+15 0.50 2x015 22+22 1.33 4 x015 22 +22 2.72 6 x017 30+30 3.75 8 x033 50+50 5.00 equip ment. 0x014 18 +18 0.42 2 x016 25+25 1.00 4 x016 25+25 2.40 6 x018 35+35 3.21 8 x042 55+55 4.54 • High efficiency enabling '2 *017 30+50 0.83 4 x017 30+30 2.00 6 x026 40+40 2.81 8x028 110 4.54 0 x015 22+22 0.34 conservtive rating whilst 0 x016 25+25 0.30 2 x028 110 0.45 4 x018 35+35 1.71 6 x025 45+45 2.50 8 x029 220 2.27 0x017 30+30 0.25 2 x029 220 0.22 4 x 028 110 1.09 6x033 50+50 2.25 8 x030 24+3 2.08 maintaining size advantages. 4 x029 220 0.54 6x028 110 2.04 (encased in ABS plastic) 2 x030 240 0.20 • Lower operating temperature. 4 x030 240 0.50 6x029 220 1.02 625 VA 140 x 75mm 5Kg 30 VA 80 VA 6 x030 240 0.93 Regulation 4% 70 x 30mni 0.45Kg 90 x 30mm 1Kg 160 VA 300 VA W hy ILP? Regulation 18% Regulation 12% 110 x 40m m 1.8Kg 110 x 50mm 2.6Kg 9x017 30+30 10.41 9 x 018 35+35 8.92 1 x010 6+6 2.50 3 x010 6+6 6.64 Regulation 8% Regulation 6% • Ex-stock delivery for standard 3x011 9+9 4.44 9x026 40+40 7.81 1 x011 9+9 1.66 5x011 9+9 7 x013 15+15 10.00 240v range. 3x012 12+12 3.33 9 x025 45+45 6.94 1 x012 12+12 1.25 5 x012 12+12 6.66 7 x014 18+18 8.33 9x033 50+50 6.25 • Fast prototype service 1x013 15+15 1.00 3x013 15+15 2.66 5 x013 15+15 5.33 7 x015 22 +22 6.82 3x014 18+18 2.22 9x042 55+55 5.68 available. 1 x014 18+18 0.83 5x014 18+18 4.44 7x016 25+25 6.00 3 x015 22+22 1.81 9x028 110 5.68 1 x015 22+22 0.68 5 x015 22+22 3.63 7 x017 30+30 5.00 • 3 weeks despatch for special 1.60 9 x029 220 2.84 1 x016 25+25 0.60 3x016 25+25 5 x016 25+25 3.20 7 x018 35+35 4.28 orders. 3 x017 30+30 1.33 9 x030 240 2.60 1 x017 30+30 0.50 5 x017 30+30 2.66 7 x026 40+40 3.75 • 2 year no quibble guarantee. 3 x028 110 0.72 5 x018 35+35 2.28 7 x025 45+45 3.33 3 x029 220 0.36 5 x026 40+40 2.00 7 x033 50+50 3.00 • No price penalty for call-off 3 x030 240 0.33 5 x028 110 145 7 x028 110 2.72 orders. 5 x029 220 0.72 7 x029 220 1.36 5 x030 240 0.66 7 x030 240 1.25

Prices inducing P&P and VAT Mail Order - Please make you crossed cheques Post to: ILP Electronics Ltd., Dept. 2 VA Size C VA Size E or postal orders payable to ILP Electronics Ltd. Graha m Bell House, Roper Close, 15 0 7.06 160 5 12.17 Trade - We wil open your credit account Canterbury, Kent. CT2 7EP 30 1 7.67 225 6 13.75 immediately upon receipt of your first order. Tel: (0227) 454778 Telex: 965780 50 2 8.90 300 7 14.97 80 3 10.06 500 8 19.60 120 4 10.65 625 9 22.30 For 110V primary insert "0" in place of "X" in type number. For 220V primary (Europe) insert "1" in place of "X" in type number. VISA For 240V primary (UK) insert "2" in place of "X" in type number. IMPORTANT: Regulation - All voltages quoted are FULL LOAD. Please add regulation figure to secondary voltage to obtain off load voltage. ELECTR O NIC S LTD. in&

IF YOU'RE CRAFTY, YOU'RE BOUND TO PICK UPA LOT OF TIPS AT OUR SHOW

WEMBLEY CONFERENCE CENTRE 10-13 JANUARY, 1985 Thursday to Saturday 10am-7pm Sunday 10am-6pm Whether you're a craftsman creating fine furniture or a beginner making a simple bookshelf, you'll find everything you could possibly need under one roof. See the latest ideas and equipment for woodworking. Talk to the experts about timber and finishes. * CRAFT MARKET See the very latest ideas and equipment for woodworking. * FREE CHRISTIES VALUATIONS Let Christies value your antiques. An expert will be available at the show, so bring along your interesting pieces, or photographs of them, if you prefer. Admission prices: Adults £2.50 Children under 16 and Senior Citizens £1.50. Advanced Party Booking for groups of 20 or more. Adults £2.00 Children £1.00 (Plus one free ticket per 20 sold for the organiser or teacher).

Further details fro m: Practical \Xood working Tickets. Reed Exhibitions. Surrey !louse. I Thro wley Way, Sutton, Surrey SN1 I 1(2 Q

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4 Practical Electronics February 1985 / Grkit. Making it bigger and better. 1-30V 1mA-2A PSU Selected Lines Cirkit stock all the Adjustable 1-30V Power supply with pre-setable BBC to Centronics components, accessories and current limit from IrnA-2A 41-01600 37.46 Connect Cable 03-10019 7.25 tools and the kits you're looking 5-12V IA PSU Dragon to Centronics Connect Cable 03-10017 725 for. Designed and selected to offer Adjustable PSU from 5-12V with current protection, 1 amp max output 41-01504 6.45 Cl2 Computer Cassette 21-00012 0.55 the best possible standards at the Interface 84 multiplexed I-30V I.5A PSU Ram Card 40-84000 59.95 best possible price. 1-30 volt adjustable PSU with protected Z80A industrial controller 40-82000 54.95 output up to 1.5 Amps 41-01402 10.45 EPROM Eraser 84T 40-82001 59.95 3 DIGIT LED DVM 6502 Micro Controller 40-65020 54.95 DVM to read up 10 99.9 volts or configured as an 6802 Micro Controller 40-68020 54.45 ammeter to read up to 9.99 amps '41-01403 17.00 PB2720 80dB Piezo Buzzer 43-27201 0.55 INFRA RED LINK 10M 1 5A 10.7 Center Freq. 20-10152 2.10 Single channel IR Link with relay 10M08AA 10.695 Center Freq. 20-11152 3.49 PC 177 LCD (Freq.) output 41-01300 9.60 39-17700 20.00 CM161 LCD Clock 40-80161 8.25 TEMPERATURE SENSOR 8 x 0.3" IC socket 28-00800 0.12 Thermistor based temperature sensor 14 x 03" IC socket 28-14000 0.13 with relay output 41-01303 6.20 16 x 0.3" IC socket 28-16000 0.13 LOCOMOTIVE SOUND GENERATOR 6V KUIT-A Relay 46-86000 0.48 Realistic steam sound and whistle for 9V KUIT-A Relay 46-80001 0.48 model railways 41-01304 9.20 12V KUIT-A Relay 46-80002 0.48 CX120P Centronics Interlace LAMP DIMMER COAX Relay 46-90120 11.96 CX520D COAX Relay (N-type) 46-90520 Cirkit Kits Control lamps and drill speed 41-01305 5.70 26.98 CX540D COAX Relay (BNC) 46-90540 26.98 CIRKIT ELECTRONICS TOOL KIT WATER LEVEL ALARM Contains: 15W Soldering Iron 2 spare bits. heat Alarm to indicate high water level or shunt. solder, pliers, cutter. flooding 41.01601 2.70 screwdriver 40-00007 12.00 3 NOTE CHIME Doorbell chime with adjustable AUDIO FUNCTION GENERATOR Versatile waveform generator with sine, tones 41-01503 7.00 triangular and square wave outputs. 2M PRE AMP On board mains PSU 41-01302 27.00 Miniature low-noise MOSFET pre-amp STEREO 40W AMPLIFIER for the 2m amateur band 41-01307 381 Single board 40W per channel stereo 2M CONVERTER amplifier 41-01301 38.00 Low noise 144MHz-28MHz amateur band converter 41-01306 17.35 STEREO VU METER 5 LED per channel stereo VU meter for 2M POWER AMP use with stereo amplifiers 41-01401 11.50 20W - 10dB gain - power amplifier for the 2m 5W AUDIO AMP band. Automatic TX switch over, RX A very compact audio output stage for use pre-amp, robust construction 41-01404 32.87 HT-320 in a wide range of equipment 41-01406 4.60 Multimeter (20101-V) 56-83201 14.00 UNIVERSAL AMP Please add 15% VAT to all advertised prices and A universal audio pre-amp with a 60p post and packing. Minimum order value £5 gain of 10 41-01604 6.45 please. We reserve the right to vary prices in accordance with market fluctuation. MONO REVERBERATION UNIT Just send for our catalogue or visit one of our Single channel, spring line reverb unit three outlets at: to add echo effects to tape recording etc. 41-01602 10.00 200 North Service Road. Brentwood. Essex. CMI4 4SG: 53 Burrf ields Road, Portsmouth, Hampshire. P03568: TONE GENERATOR AND DETECTOR Park Lane, Broxbourne, Hertfordshire. ENIO 7NQ. Very low distortion tone generator Items in stock despatched within 48 hours and signal detector for circuit fault [To: Cirkit Holdings PLC, Park Lane, finding 41-01603 10.46 Broxbourne, Hertfordshire. ENIO 7NQ. 10MHz DFM I enclose 85p. Please send me your latest 10MHz OFM 8 Digit LED digital frequency meter CRYSTAL CALIBRATOR catalogue and 3 x discount vouchers! and period measurement 41-01500 54.10 Crystal reference calibrator for alignment If you have any enquiries please telephone us 50MHz PRESCALER of receivers, outputs at 4, 2, 1MHZ, on Hoddesdon (0992)444111. Extend the range of the 10MHz DFM to 100, 50 AND 10KHz 41-00801 4.32 Name 50MHz 41-01501 8.55 CB NOISE SQUELCH Address 1-5MHz PRE AMP Improves the mute performance of the Low frequency pre-amp and waveform majority of CB rigs 41-01605 5.40 shaper for the 10MHz DFM 41-01502 5.13 CENTRONICS INTERFACE Telephone 70cm PRE AMP Connect your personal computer to Area of Special Interest Low noise, miniature pre-amp for the the outside world via the Centronics 70cm amateur band 41-01506 4.78 printer output 41-01606 22.50 PE2

70cm CONVERTER 70cm PA 70cm to 144MHz low noise converter featuring IOW Power amp to boost the output of pre-aligned helical filter, schottlry diode mixer handheld and portable 70cm and low noise transistors 41-01405 21.50 transceivers 41-01505 33.82 irkit Bigger Stock. Better Service ////,'" ELECTRONIC SIREN TOP QUALITY. . . TOP SERVICE MICROPROCESSOR KIT TIMER KIT

Produces an extremely BOTTO M PRICES! Designed to con- loud piercing swept For FREE CATALOGUE send 9" X 6" SAE - contains full list of stock trol 4 outputs frequency tone from a independently range all at very competitive prices. Cash with order (except account 9-15V supply Enable switching on and input for easy connection customers). Access or Barclaycard telephone orders welcome. Add off at preset times to alarm circuits 75p p&p + 15% VAT to all UK orders. Overseas customers add £2.75 over a 7-day Includes Sin Horn Speaker cycle LED dis- alp Europe, £6.50 elsewhere. Giro No. 529314002. Goods by return play of time and day, easily program med Mini Siren via 20 way keyboard Ideal for central subject to availability. Shop open 9am - 5pm (Mon-Fri). 10am -4pm As above, but with a small speaker (instead heating control lincluding different of horn speaker) for internal use Sat). ALL PRICES EXCLUDE VAT switching times for weekends) Battery Complete with box (4 30 Ell back up circuit Includes box 18 time settings INFRA-RED REMOTE CONTROL KITS SECURITY PRODUCTS CT6000K £39 00

XK114. Relay Kit for CT6000 Protect your home includes PCB, connectors and and property and MK19 Stereo Amplifier Controller Kit one relay Will accept up to 4 save by building for remote control of bass, treble and relays 3A 240V c o contacts E3.90 your own burglar volume (or balance) by MKII, Includes a one of 701 115 Additional Relays E1.65 alarm system 10 decoder remote channel or input selection. May be connected between the pre-amp and power amp of almost any audio system. Stair Mat 23 • 7 in 1950 1201 £1 70 ELECTRONIC LOCK KIT These kits are designed to enable infra clan Floor Mat 29 .• th in 1950 1251 E2.60 red remote control to be incorporated into Tamper-proof connecting block MK12 Receiver Kit mains powered With hundreds of uses indoors, garages, virtually any application from switching 1950 1101 E0 30 with 16 latched or momentary outputs car anti-theft devices, electronic equip- car locks or alarms to controlling Hi-Fi or Door/Window Contacts. Flush Latched version is f or applications re ment, etc. Only the correct easily TV The application will determine the mounting, 4 wire, Magnet switch 'wiring one output on at a time. eg TV changed four-digit code will open it' Re- interface circuitry between the receiver Per Pair 1950 1401 E1.05 channel selection Momentary type gives quires a 5-15V DC supply. Output and the controlled device General in Window Tape 0 5- wide 50ni an output only during transmission Lines 750mA. Fits into standard electrical wall structions and applications are supplied 1950 1451 E2.50 box. The kits are coded and provide a high may be latched as required Window Tape Terminations Size 9 . 4 2cms El 3 50 Complete kit (except front panel) dearee of security and noise immunity Per pair 1950 1501 C0.36 XK101 (11.50 MK 18 Transmitter Kit - for use with Key-operated Switch. 1 5A 250V Electric Lock Mechanism for use with MK ft 'MK 12 receivers Requires PP3 bat MK 15 Dual Latched Solid State Relay &PSI Heavy chrome metal existing door locks and the above kit tery Size 8 . 2 . 13cms Range approx for switching mains loads such as lamps. 13501281 E4.50 TVs, etc, from the outputs of the MK 12 (Requires relay I 12V AC 'DC coil Passive Infra-Red Detector 6011 E6.80 !momentary) 15 items may be switched 1701 1501 £14 95 Keyboards for MK 18 Detects intruder's body heat Range independently using 8 MK 15s Triacs Mot MK9 4-way for use with MK 12 (1 .90 10 metres 12V DC. no & nc contact supplied) switch at mains zero to reduce MK1016- way for use with MK 12 E5.40 1950 1351 E40.00 interference £4.50 Alarm Control Unit. 4 input circuits, 2 MK13 11 way for use with MK 11 £4.35 HO ME LIGHTING KITS instant and 2 delayed Adjustable entry, MK 11 Receiver Kit mains powered exit and alarm times Built and tested Full Provides 10 latched plus 3 analogue out These kits are instructions supplied Srze 180 130 . Puts ideal for controlling audio amplifiers. 30m m Supply 12V DC TV or lighting where control of light designed to 1950 160/ E26.00 brightness is required (13.50 replace a stan dard wall switch Ultrasonic Burglar Alarm. self-contained MK 14 AC Power Controller Kit I or to control up to mains or battery powered unit complete (phase) controlling AC loads from MK 11 300w of lighting with horn and AC adaptor. Imputs for pres- analogue outputs, eg lamp dim ming sure mats and other sensors together with (5.20 exit/entry delays enable this unit lobe used TDR300K Remote Controlled* as a complete system. (45.00 • p&p (2.20 Light Dim mer £14 95 8W Horn Speaker. 5 5 ins 8 ohm Ideal for sirens, etc 2 5m lead and 3 5mrn lack COMPONENT PACKS BT STYLE PHONE MK6 Transmitter for Mug 1403 1481 £6 15 CONNECTORS above 4 50 PACK 1 650 Resistors 479 10M TD300K Touch Dimmer £7 75 10 per value 4 00 PACK 2 40 • 16V Eler trolytir Line Jack Units IR GARAGE DOOR 75300K Touch Switch £7 75 10 1000pF 5 per Master Unit (first CONTROLLER KIT '(3 25 line unit, has bell value TDEiK 2 way extension capacitor and PACK 3 60 • Polyester Capa for above kits £2 50 citors 0 01 luF 250V Surge arrester For controlling motorised garage doors E5 55 Flush or sort ace ntrng Screw con 5 values LI3300K Rotary controlled and switching 3 00 'lectors PACK 4 45 Presets 1009 1M Light Dim mer £395 garage and drive PACK 5 30 • Low Prohle IC Master M u sh, 960 10 ' 'I / 3 3.0000 lights on of f up to Sockets 8 14 & 16 pm E2 40 Master (surface, 960 112 a range of 40 ft PACK 6 25 Red LEDs i5nirni ft 75 Master imini surf acei 960 113 3 50 Secondary (flush) 960 114 £2 65 DISCO LIGHTING KITS Lots of applo Secondary (surface] 960 116 £265 cations like Secondary (mini surf I 960 117 £3 00 controlling lights Dual outlet adaptor 960 118 E4 20 011000K This value for money 4 way and TVs. 4-way line cord with plug to spade ter chaser features hi directional sequence etc, in the home Ideal for aged or dis minals 1960 1201E2.00 and dim ming 1kW per channel E15.95 abled persons, this coded kit comprises of 4 way line cord [960 1301 E0.20 per to DL21000K - A lower cost uni directional a mains powered infra red receiver with a version of the above Zero switching to normally open relay output plus two LCD DIGITAL M ULTIMETERS reduce interference £8 95 latched transistor outputs battery Optional opto input allowing audio 'beat' powered transmitter and opto isolated light response IDLA/11 70p solid state mains switch LOW COST! 10M ohm. 31/a digit 0.4 in Auto Ranging. 3°2 013000K - 3-channel sound to light kit display. Auto zero and polarity, low batt. digit 10m m display. features -zero voltage switching, auto- E25. 00 Continuity buzzer, XK 103 indication. overload protection Includes =0 matic level control and built in micro XK105 Extra transmitters E10 50 test leads, battery, spare fuse, manual, low battery, overload hone 1 k W per channel f 12 95 carrying case. and range indication AC Volts 0 200 - 500 10A internal shunt DC Volts, 0.2-20-200-1000 for ACiDC current DVM/ULTRA SENSITIVE PANTEC KITS DC Current' 0-20m 200mA. measurement. Carry- Resistance' 0-2k 20k 200k-2 M ing case supplied THERMO METER KIT Size: 138 86x 36mm. AC Volts: 0-2-20-200-600. 1405 202/ (25.95 DC Volts: 0-0,2i2-20-200•1000 Professional - 10M, 0.5 in, 31/i digit. AC Current: 0-200mA. 0.10A. P62 FM Micro Transmitter £7.50 Based on the ICL 7126 and a 3'2 digit Overrange and low battery rndication. DC Current. 0-200mAi0- 10A. liquid crystal display, this kit will form the P63 Stabilised Power Supply £1370 Overload protection. Includes leads, Resistance: 0-200-2k-20k-200k 0i2M. basis of a digital multimeter (only a few P65 2 1 Ow Stereo Amplifier (14.50 Size: 160 v 85. 29m m. spare fuse, battery, manual and case additional resistors and switches are re- P66 2 • 40w Stereo Amplifier E24.95 Transistor Checker. Size: 175 v 93 . 1405 206) (44.85 P67 Pushbutton Stereo Preamp 02,80 quired - details supplied), or a sensitive 42m m. High Sensitivity Temperature Probe. P68 Tone & Volume Control E13.60 digital thermometer (50 ° C to *150 ° C) AC Volts. 0-200 ,750. For use with a rnultimeter to measure P611 3m FM Transmitter (11 95 reading 01°c The kit has a sensitivity of DC Volts: 0-200m-2-20-200-1000. temperatures from -- 50°C to 250°C. P613 Single Channel FM 200mV for a full-scale leading automatic DC Current: 0-20ui2mi20m.200mA Accuracy: 1.5°C @25 ° C, 2 °C@100 ° C. polarity and overload indication. Typical Transmitter E9.80 0- 10A, Response time lie water), 5 seconds. battery life of 2 years IPP31 E15.50 P614 Receiver for above £15 50 Ohms: 0-200-2k-20k-200k-2M. 0-20M Includes case, calibrated scale and in- 1405 2041 £33.50 structions. 1405 220) (8 .50

C.1504 NORTH ELECTRONICS ClEIGUL•il 11-13 Boston Road NWEL London W7 3SJ T GARAGE ORDERS ENQUIRIES 01-567 8910 01-579 9794

01-579 2842 TECHNICAL AFTER 3pm

6 Practical Electronics February 1985 [ El V OL U M E 21 I\19 2 FE B R U A R Y 19 8 5

Editor Mike Kenward SAFETY Secretary Pauline Mitchell ELECTRONICS has done much to vehicle braking system, so we can- benefit our way of life and stan- not fit a system to help ourselves. Editorial Tel: Poole (0202) 671191 dard of living in all areas from enter- The sad thing is that the tainment to safety at sea and in the technology and mechanics to per- Advertisement Manager air. Of course it has also enabled form the necessary tasks has been David Tilleard 01-261 6676 development of more sophisticated around for some years. Perhaps the weapons and defence systems but manufacturers feel we will not pay Secretary that is another story. Our explora- for the extra safety; maybe they do Christine Pocknell 01-261 6676 tion of space is totally dependent on not feel it is necessary? The next Classified Supervisor electronics and navigation about our time you see a minor skid that could Barbara Blake 01-261 5897 own planet is also now based have been dangerous, a motor- mainly on high technology. cyclist fall off, or a lorry stopping Ad. Make-up/Copy What a pity then that the modes slightly sideways just think about Brian Lamb 01-261 6601 of transport we all use every day what could have gone badly wrong have not benefited more from the and see if you feel anti-skid braking Queries and letters concerning introduction of electronics to aid would be worth another couple of advertisements to: Practical Electronics Advertisements, safety. The car you drive may have a hundred pounds on the already in- King's Reach Tower, computer to show fuel consump- flated price of a new vehicle in the Stamford Street, London SE1 9LS tion, it may have a talking dash UK. Telex: 915748 MAGDIV-G panel or even an engine management computer, but have the elec- LEGISLATION Letters and Queries We are unable to offer any advice on the tronics been used to improve Maybe you will even think that use or purchase of commercial equipment safety? How many vehicles are legislation would be a good thing, or the incorporation or modification of fitted with an anti-locking braking even if it might not save as many designs published in PE. All letters requiring system? How often do you see lives as compulsory seat belt a reply should be accompanied by a stam- vehicles skidding even on dry roads? wearing ! ped addressed envelope, or addressed en- How often do the back wheels of Incidentally, the motorcyclist I velope and international reply coupons, and unladen lorries lock up when they saw come off this morning was each letter should relate to one published stop? How many motorcyclists shaken but not badly injured, project only. come off in the wet when braking or although his bike was probably a Components are usually available from advertisers; where we anticipate difficulties skid into the back of the car in front? write-off and the car he ran into a source will be suggested. Admittedly many of the skids that badly damaged. Think about it if you do occur result in no damage or in- buy a new vehicle! The extra cost Old Projects jury but of course some do. Surely it could be worth the time, trouble and We advise readers to check that all parts is better to make vehicles safer with heartache alone. are still available before commencing any an electronically controlled failsafe project in a back-dated issue, as we cannot braking system than to get them guarantee the indefinite availability of components used. talking to you? This is one area where the amateur in electronics Technical and editorial queries and letters to: can do little himself. We would not Practical Electronics Editorial, encourage readers to modify any Westover House, West Quay Road, Poole, Dorset BH15 1JG

BACK NU MBERS SUBSCRIPTIONS and BINDERS... Copies of Practical Electronics are available ocsA cn cru., tas peronsa w m a a by post, inland for £13, overseas for £14 Copies of most of our recent per 12 issues, from: Practical Electronics, P..C1111t:ITICI• MIC AIDIS•1111.111.7T.3141 .11. NVTICI .D .11.40 issues are available from: Post Subsceription Department, IPC Magazines Sales Department (Practical Elec- Ltd., Room 2816, King's Reach Tower, tronics), IPC Magazines Ltd., Stamford Street, London SE1 9LS. Che- Lavington House, 25 Lavington ques, postal orders and international money Street, London SE1 OPF, at £1 orders should be made payable to IPC each including Inland/Overseas Magazines Limited. Payment for subscrip- p&p. Please state month and tions can also be made using a credit card. year of issue required. Binders for PE are available Phone: from the same address as back Editorial Poole (0202) 671191 numbers at £5.50 each to UK or overseas addresses, including We regret that lengthy technical enquiries postage, packing and VAT cannot be answered over the telephone.

Practical Electronics February 1985 7 Items mentioned are available through normal retail outlets, unless otherwise specified. Prices correct at time of going to press. re• PATENTLY HIGH COST MEAT ION OBVIOUS M ost constructors will be painfully aware of the annoying shrink-back All too often the most worrying aspect for the properties of insulation, encountered when soldering wires into place. creator of an original design is, how to protect Over the years manufacturers have developed heat-proof insulation that idea from those who would copy and ex- materials for specialised cable applications w hich eventually filter ploit it for their own gain. This has been the case since the first inventor brought forth a through industry to the home-constructor —and very welco me they are, brainchild, only to stand by helplessly as too. It.may surprise you to kno w, however, just ho w far, and to what ex- someone else marketed his idea and made pense, manufacturers will go in order to optimise the insulating properties a fortune. The laws governing Patents, of the materials they use. Trademarks, Designs and Copyright are complex indeed, without guidance the layman may B.I.C.C. for instance has just completed be forgiven for getting confused. Laurence the installation of a new electron beam ac- Shaw's recently reprinted guide can be of celerator plant at its Electronic Cables fac- great help to inventors and innovators alike. tory in Cheshire, the cost? A staggering The Practical Guide for people with a new £2.5 million. The facility is considered to be idea is a book which explains in clear the most sophisticated and versatile of its language how to protect a new idea, product kind in the Western world. The accelerator or scheme and exploit it to the full. Market produces high velocity electrons which research, approaching a manufacturer, telling have sufficient energy to penetrate the the world about an idea without losing your cable insulation. rights and patenting an invention are all Once inside a polymeric insulation, the covered together with secret patents. electrons initiate chemical reactions which This publication is available from lead to the formation of chemical bonds or booksellers at f5.50, or by mail order at f5.95 crosslinks. Increasing the number of thermoset with a better balance of from The Patent Eye, George House, George crosslinks leads to eventual formation of a mechanical properties at both high and low Road, Edgbaston, Birmingham 1315 IPG. three-dimensional network which substan- temperatures; chemical resistance is also (021 454 2165). tially enhances the physical properties of enhanced. the insulant. The whole facility is enclosed in 1500 The most obvious effect of crosslinking is tonnes of concrete for personnel protection that the material loses its thermoplastic during plant operation. The picture shows M A GIC characteristics and becomes a non-melting the plants computer control room. L ANTE R N Question: If you are exposed to radiation do you glow in the dark? Answer: Of course not. Not unless you are first coated with a phosphor of some kind. It is a useful fact that beta particles from a radioactive source will, 111 TELEVISIONIONITOR when they strike a phosphor such as zinc sul- The latest in the TX range from Ferguson is Perhaps the most interesting of these phide, cause light to be emitted from it. Bat- a 14 inch monitor/colour television. It will options is the ability to directly connect telle's Pacffic . Northwest Laboratories are offer those who can afford a second or even a home computer without the testing a novel application of this third set a very flexible visual display tool. modulation/demodulation problems that phenomenon. Scientists are evaluating a por- The MC01 has separate RGB, composite occur when using a standard TV set. It must table runway lamp for setting up landing video and aerial inputs enabling the user to be borne in mind that not all currently strips in out-of-the-way places, or during get the best possible display from broad- available home computers have a direct emergencies in which the electricity supply is cast TV, video recorders, teletext and home video output. The machines without lost. computers. this facility have on-board The lamp comprises a glass tube, its inside modulation/demodulation and were so surface coated with a phosphor, and which is designed for use with a visual display filled with tritium gas, the radioactive isotope mediu m that most people already of hydrogen. The lamp can not be turned off, it possessed —a standard TV set. simply continues to glow for the twelve years The provision of separate RGB, com- half-life of the gas. Keeping the glass clean is posite video and aerial sockets also allows the only maintenance operation required dur- the home computer, video recorder or ing that time. The quantity of radioactive game and TV aerial to be connected material used is so minute that it is harmless simultaneously; the set senses the signal even ([the glass breaks, it is claimed. selected and switches to it automatically. During field tests in Alaska pilots reported A range of special connector leads is that they perceived light from the available to cover the different home com- radioluminescent lamps differently from that puter options. The set is manufactured in of conventional light, and human response the UK at the company's Gosport plant. It is now needs to be assessed to find out how expected to retail at circa £230. useful these lamps may be.

8 Practical Electronics February 1985 . M ARCH: M ACH BTi rumble BEMIS 111C's go Ban machine Ensuring peak response and high-quality reproduction, Electrolube's Video Tape Following a tongue-in-cheek comment from Head Cleaner is a safety solvent designed Mike Cook, the Technical Editor of Micro for use on all magnetic tape heads. User, several hundred BBC micro owners The cleaner loosens and removes ac- recently returned their machines to their cumulated deposits of dirt and tape oxide respective dealers, in the fear that they were and dries quickly without leaving any about to detonate. residues on the tape. The cleaner is non- The unfortunate comment was printed in flammable, and non-conductive, it will not the magazine's problem page as part of a reply damage plastics or rubber. to a reader's query regarding an 'error The sqlvent comes in handy 110 gram message'. Mr Cook, believing himself to be the aerosols and is conveniently applied by subject of a "wind-up", answered in kind. spraying directly onto the heads and "Take your computer immediately to the mechanisms. In addition, the cleaner is dealer as this error message indicates that it is ideal for spraying onto cleaning tapes and about to explode." other tape cleaning devices, such as cotton The manufacturers, Acorn Computers, buds or felt and chamois leather sticks. were not amused, neither was the middle-aged Available on its own at circa £1.20, or housewife who reportedly surrounded her with 25 extra long cotton buds at circa It's new from British Telecom, machine with a bucket of water. £1.60 from electrical retail outlets. For paging far-off staff. A little pocket thing, That could well cause a laugh. POINTS

You see instead of 'bleeping', ARISING... It's been made to 'vibrate'. So you're the only one that knows, RING MODULATOR Ha and you have got a date. December, 1984

The waveforms coming through the air, Alterations to this project must be made as Will go right through your pants. follows: And trigger-off this rumble-box, In Fig. 9 the component marked C35 Like a herd of elephants. should be marked R35. The capacitor C21 should have its +ve So if you're in a meeting, terminal connected to R10. Friends might still get the rise. In Fig. 10 the unmarked component When they notice that your eyeballs, mounted between JK1 and JK2 is R47. A wire link should be connected between Are looking like mince pies. JK3 IC25 —vel and JK4 (C26 +ve).

All Electronics Show/ECIF April 30—May 2. Olympia 2. E Circuit Technology April 30—May 2. E Field Service & Repairs April 30—May 2. Olympia 2. E 3nrithittli • • Automan (manufacturing) May. NEC. Ti Please check dates before setting out, as we cannot guarantee the ac- Scotelex June 4-6. Royal Highland Soc., ex. Hall, Ingliston, curacy of the information presented below. Note: some exhibitions may Edinburgh. Al be trade only. If you are organising any electrical/electronics, radio or Personal Computer World Show Sept. 18-22. Olympia 2. M scientific event, big or small, we shall be glad to include it here. Address details to Mike Abbott. S2 Fairs & Exhibitions Ltd., f 01-831 8981 International Light Show Jan. 14-28. Olympia. E6 D6 0 1 -7 0 1 7127 British Toy & Hobby Fair Jan. 18—Feb. 2. Olympia. D6 Evan Steadman 0799 26699 Component Fair March 10. Carleton Community Cntr., Pontefract (on E6 f 058 84 658 Al to Darrington). F2 F2 Pontefract Am. Rad. Soc. N. Whittingham f 0977 792784 London Medical March 12-15. Earls Court. S2 F5 01-487 4397 IFSSEC (fire/security) April 15-19. Earls Court, London. S ITF f 021-705 6707 Cast (Cable & Satellite) April 16-18. NEC, Birmingham F5 K2 Reed Exhibitions, Surrey Ho., 1 Throwley Way; Sutton, Surrey Communications April 23-25. Olympia. I Montbuild f 01-486 1951 Photoworld April 23—May 6. Earls Court. I 0 Online f 01-868 4466 CAD April 26-28. Metropole, Brighton. K2 f 01-387 5050 Fibre Optics & Lasers April 30—May 2. Olympia. E Al Institute Electronics f 0706 43661 Custom Electronics & Design Techniques April 30—May 2. E Ti Cahners f 0483 38085

Practical Electronics February 1985 9 PART 1 M.TOOLEY BA

P1 A"V ! T CEng F iELD E

jfr pràvements in semiconductor technology invaluable accessory for those wishing to run-up" the iciiilar, the introduction of a number of highly amplifier without destroying their ear drums. nnSumer integrated circuits and power Darlington Having started on a cautionary note it is perhaps worth , have resulted in audio equipment which is both corn- saying that, provided readers carefully follow the setting-up and Very straightforward. This new series deals with the procedure and observe the recommendations concerning onstruction of a variety of modules for use in the custom heat sinks, component ratings, and supply rails, there should design of sound reinforcing systems and for public address be few, if any, problems. work generally. We start, this month, with full constructional details of a CIRCUIT DESCRIPTION 50W power amplifier module. This unit forms the basic A simplified block schematic of the power amplifier building block for several complete designs to be described module is shown in Fig. 1. The corresponding circuit diagram later. Details of suitable pre-amplifiers, line drivers, tone con- is shown in Fig. 2. The module consists essentially of a dif- trols and mixers will also be included; the aim being that of ferential input stage followed by a driver and complementary affording the individual constructor the widest possible power Darlington output stage. The unit runs from balanced choice of audio system configuration. (i.e. separate positive and negative) supply rails with a common OV rail at earth potential. THE 50W PO WER AMPLIFIER MODULE The input stage is formed by TR 1 and TR2 which are con- The power amplifier module is electrically robust, is sim- nected as a long-tailed differential pair with TR3 acting as a ple to construct, and uses low-cost readily available compo- constant current source. The emitter currents of TR1 and nents. In its basic form, the module is capable of delivering a TR2 are determined by VR1 which provides a range of ad- continuous r.m.s. sine wave output of 50W into a 4 ohm justment from about 1.5mA to 3.0mA total current. The load. The design may be easily modified for operation with signal input is applied to the base of TR 1, via a switched d.c. alternative output transistors and/or supply rails, as shown in blocking capacitor arrangement, whilst negative feedback Table 1. (both d.c. and ac.) is applied to the base of TR2. The overall Whilst every effort has been made to avoid the pitfalls, it voltage gain of the module is determined by the amount of should be stated at the outset that this project, together with feedback applied and is approximately equal to the ratio of its higher power derivatives, is not for the faint hearted. In- Max. Rec. Max. rec. TR6 - TR7 Ti sec. deed, the prototype amplifier was not developed without a r.m.s. supply heatsink (npn) (pnp) rating few disasters, including four output transistors which literally output rail thermal 2 x melted during the testing stage! power voltages resistance An important requirement of this project (and one which 30W ±30V 4 deg.C/VV TI P121 TI P126 20V/1.5A readers ignore at their peril) is that the loudspeaker systems 45W ±30V 2 deg.C/VV 11P141 TI P146 20V/2A employed should be capable of handling the full amplifier 80W ±40V 1 deg.C/VV 10K80 11K80 25V/2.5A output power. However, readers who do not have immediate MJ3001 MJ2501 access to correctly rated loudspeakers need not despair 2N6058 2N6051 120W ±50V 0.5 deg. MJ11016 MJ11015 32V/3A since we shall, next month, be describing a calibrated test C/W load rated at continuous r.m.s. powers well in excess of 100W. A dum my load of this type should prove to be an Table 1 Output device selection table

CUSTO M DESIGN YOUR OWN HIGH PO WER AUDIO SYSTE M

Practical Electronics February 1985 COMPLEMENTARY POWER R3 to R4. DARLINGTON OUTPUT STAGE c Id,. Direct coupling of input signals is provided by means of Si which by- DIFFERENTIAL INPUT STAGE DRIVER BIAS SUPPLY passes the d.c. blocking capacitor, Cl In order to preserve sym metry of the differential stage, the following INPUT resistors are made equal: R2 and R3, R5 and R6, R1 and R4 (note that the latter assumes that the amplifier is fed from a relatively low-impedance source). TR4 forms a conventional com mon LPE1556PJ emitter driver stage using an npn LOUDSPEAKER transistor. Since the quiescent power

Fig. 1. Simplified block schematic of the Power Amplifier Module

R10

C3 SK1/4 1N4148

01/ R9 220 M. 4700. 1N4148

TR3 BC212L R12 OUTPUT 2k7 SK2 SK3 a chic

L1 KBPC Si 110V TR1 0JT 02 SK//1 Cl

4k 7 474 BIT 220n 110V BC 212L BC212L

loon

VR 2 C2 1k BC142 FS1 SK//5 100,., 20

TR7 ClO usso 4700o

R6 ON/OFF CB 470 a m 100n TR4 B4142 SK1/2 SK1/3 ff'El5571,

—30V • • Fig. 2. Complete circuit diagram of the Power Amplifier Module

dissipation for this stage is in the region of 125m W, a metal SPECIFICATION cased T05 style device is much to be preferred. Bias for the output transistors is provided by TR5 which acts as a constant voltage source, adjustable by means of VR2. The Maximum power output: 60W r.m.s. into 3ohm output stage is a conventional complementary sym metrical (measured at 1kHz) 50W r.m.s. into 4ohm arrangement using Darlington pairs, TR6 and TR7. A variety 40W r.m.s. into 8ohm of different devices may be employed in the output stage 25W r.m.s. into 15ohm depending upon output power requirements and the Minimum recommended load available supply voltage rails. These configurations are sum- impedance: 3ohm marised in Table 1. The output stage is protected by means Voltage gain: 10 of two 5A quick-blow fuses, FS2 and FS3. It should perhaps Input voltage for max. rated output: less than 2V r.m.s. be mentioned that this form of protection is not completely Input impedance: 50k approx. foolproof but will normally cope with a short-circuited load Recommended source impedance: 600ohm Total harmonic distortion: 0.05% typical at 30W or failure of one of the output Darlingtons. output into 8ohm C6 and R17 form a Zobel network whilst Li ensures Frequency response (a-c. coupled): 15Hz to 50kHz at-3dB unconditional stability of the amplifier when operating into a (d.c. coupled): d.c. to 50kHz at —3dB severely capacitive load. Bootstrap feedback is applied via Hum and noise: less than —85dB C4 in order to raise the effective impedance of the collector related to max. rated load for TR4. C5 provides high-frequency roll-off since the output bandwidth of the amplifier is otherwise somewhat excessive. The power supply arrangement is fairly conventional and

Practical Electronics February 1985 11 provides sym metrical supply rails of nominally +30V and Output power relative to 35W —30V. (dB) +2 CONSTRUCTION -2 With the exception of the power supply (Ti, FS1, REC1, C9 and C10) and the output transistors (TR6 and TR7), all components are mounted on a single-sided p.c.b. measuring approximatly 65m m x 115 m m. The component overlay of the p.c.b. is shown in Fig. 3. Components should be assembled on the p.c.b. in the following sequence: terminal pins, resistors, capacitors, transistors, pre-set resistors, fuse clips, and inductor. The latter component consists of 20 turns of 20 s.w.g. wire wound with an inside diameter of 8mm. Care I 10 100 1k should be taken to carefully remove the enamel at each end 1 PE1559/' Frequency ( Hz) of this component in order to facilitate an effective soldered connection to the p.c.b. Fig. 5. Frequency response (8ohm load)

SKI COMMON 0 C9 +VE(+ 30V) D1 SKI INPUT TR6 COLLECTOR C3 11 1 11 1 R") 766 BASE 111—[ 615 j —• ri ; s o u p 166 EMITTER 613 1-0 TR5 L W!! scTiS SK 3 (BLACK) C. b • 0 SK2 (RED) II T R1 aT L e• C10 +VE (0V) TR4

• —.1 R14 I—• TR7 EMITTER

• 6-4 616 1—• 167 BASE

f =1 1-0 TR7 COLLECTOR

• CIO -YE ( 308)

•

FET5 1. Fig. 3. Component layout of the p.c.b.

5K3 (black) SK2 ( red)

TR7 TR6 e b

REC)

PC B

FE11-;( 1

Fig. 4. Wiring diagram for the Power Module

(2 Practical Electronics February 1985 • COMPONENTS ... -28-4V TR1 Sc b OV le +0.6V Resistors —28.4V R1,R4,R7 4k7 (3 off) TR2 S cb OV R2,R3 47k (2 off) e +0.6V R5,R6 470 (2 off) R8 10k 5 c +0.6V R9 220 TR3 b +20.8V R10,R14,R15,R16 1k (4 off) le +21.4V R11,R12 2k7 (2 off) R13 1k8 —1.0V R17 10 0.5 W 5% carbon b —28.5V c VR1 220 min. hor. skeleton pre-set TR4 {e —29.2V VR2 1k min. hor. skeleton pre-set

IC +1.0V Except where otherwise stated, all fixed resistors are TR5 -{b 0-25 W 5% carbon. —0.5V e —1.0V Capacitors Cl 220n 250V polyester c +29.2V C2 100µ 16V p.c. electrolytic TR6 -lb +1.0V C3 100µ 63V p.c. electrolytic e OV C4 2201.125V tubular electrolytic C5 33p ceramic 5 c —29-2V TR7 b C6 100n 250V polyester —1-0V 1 e C7,C8 100n 100V disc ceramic (2 off) OV C9,C10 4700µ 63V can elect. (2 off) All test voltages measured with a 20k ohm N multimeter. Semiconductors Table 2. Test voltages D1,D2 1N4148(2 off) poses the rectifier heatsink can simply be provided by the ex- TR1,TR2,TR3 BC212L (3 off) ternal case or chassis of the equipment. This expedient will, TR4,TR5 BC142 (2 off) TR6 10K80 (see Table 1) however, not normally apply to the output transistors unless TR7 11K80 (see Table 1) the case is specially designed with heat sinking in mind! REC1 KBPC802 (200V/6A) When the p.c.b. wiring is complete, the underside of the board should be carefully checked for solder bridges and dry Miscellaneous joints, whereas the component side should be examined, p.c.b. s.p.d.t. miniature p.c. slide switch paying particular attention to the correct placement and Ti 80VA mains transformer with 220V primary and two orientation of polarised components. secondary windings each rated at 20V/2A minimum (see Connections to the heatsink mounted components (TR6, Table 1) TR7 and REC1) and reservoir capacitors (C9 and C10) L1 (see text) p.c. mounting fuse clips (4 off) should be made by short lengths (typically not more than FS1 2A 20mm quick-blow mains fuse and holder 150mm) of 16/0.2m m (0.5mm 2) stranded pvc covered FS2 and FS3 5A 20mm quick-blow fuses Heatsinks (see text) wire. A typical wiring layout is shown in Fig. 4. Silicone impregnated heatsink washers (thermal resist- tance 0.33 deg.CAN) and bushes (two sets required) Terminal pins (13 required) SK1 5-pin 270 deg. DIN socket SK2 and SK3 4mm sockets (1 red and 1 black) Mains connector Printed circuit board (502-01)

The Darlington transistors must be mounted on a sub- stantial heatsink of no more than 1 deg.C/W thermal resistance. To facilitate effective heat transfer the use of silicone impregnated washers is highly recom mended (it should be noted that the collector connections of the Darlington power transistors are formed by their respective cases and these will have to be insulated from a heatsink which will invariably be at earth potential). The encapsulated bridge rectifier, REC1, also requires mounting on a heatsink. The requirement for this heatsink is somewhat less stringent than that needed for the output transistors and a rating of 5 deg.C/W (or approx. 110mm x 110m m 16 s.w.g. aluminium) should prove to be quite adequate. Happily, with this component, there is no need for an insulating washer but a liberal application of silicone grease is recommended before assembly. For most practical pur- Internal view of the Power Amp

13 Practical Electronics 'February 1985 INITIAL TESTS AND SETTING-UP Before connecting to the mains supply and switching 'on' it is important to observe the following procedure:- 1. Adjust VR1 and VR2 so that they are both in the fully clockwise position. 2. Switch Si to d.c. and temporarily short-circuit the signal input connector, SK 1 . 3. Connect the loudspeaker (or dummy load described next month). The loudspeaker should have an impedance in the range 4ohm to 16ohm and should be rated for a continuous power dissipation of 50W. 4. Switch 'on' and measure the positiVe and negative supply rail voltages. These measurements can be most conveniently made using the terminal voltages developed across C9 and C10, respectively. The supply rail voltages, in the quiescent state, should be in the range + 27V to + 30V. If the voltages differ ap- of the transformer and bridge rectifier should be preciably, or if FS1 blows on switching 'on', the wiring carefully checked. 5. Switch-off and disconnect from the mains supply. Temporarily insert two 10ohm 1W resistors in place of FS2 and FS3. This can be done quite simply by trimm- ing and folding back the leads of the resistors so that the body of the resistor is gripped firmly by the fuse clips whilst electrical connection is achieved without the need to solder. 6. Transfer the d.c. voltmeter to the output terminals, SK2 and SK3. Reconnect the mains supply and switch 'on'. Adjust VR1 for exactly OV. If the adjustment has no effect or if the resistors get hot, carefully check the p.c.b. and wiring to the output transistors. 7. Switch 'off and transfer the d.c. voltmeter to the

MODULAR AUDIO POWER SYSTEM

INPUT

10ohm resistor fitted in place of FS2, Switch 'on' and adjust VR2 to produce a reading of 0.2V. Check that a similar reading is obtained across the 10ohm resistor fitted in place of FS3. 8. Switch 'off' and disconnect from the mains supply. Replace FS2 and FS3 and remove the shorting link from SK1. Finally, select normal operation by switching S1 to the 'a.c.' position.

This completes the setting-up procedure and the amplifier OUTPUT is now ready for use. It is advisable to check the adequacy of the heat sinking arrangements by observing the temperature rise of the output transistor after, say, 15 minutes con- • tinuous operation at a reasonable output level (i.e. 10W or more). If the rise in temperature is more than 25 deg.0 above ambient, the heatsinking should be improved. tto NEXT M ONTH: We shall provide constructional details of a 100 W dum my load and a simple pre- amplifier/line driver.

Practical Electronics February 1985 14 Spectrum DAC/ADC Board R. A. PENFOLD

ITH something like a million ZX Spectrum comp uters digital inputs, and when activated they connect the precision W now in circulation there are, no doubt, a great many in reference source through to the output via some or all of the the possession of electronics enthusiasts who would like to resistors in the R-2R network. Things are arranged so that use them in computer based measurement and control ap- each input, when set high, causes the output to be in- plications. One of the ZX Spectrum's main shortcomings is a cremented by the appropriate amount. The operation of this lack of built-in interfaces, and there are no ports ready fitted type of converter has been covered in past issues of this to the machine that are suitable for applications of this type. magazine, and will not be considered in more detail here. However, it is quite easy to fit interfaces onto the expansion In order to drive the DAC from the data bus of the Spec- port, and an analogue interface is one of the most useful trum an 8 bit latch is needed, so that data written to the con- from the electronics enthusiasts' point of view. verter can be stored in the latch and used to drive the inputs The port featured in this article gives both analogue-to- of the converter. The converter then gives a continuous out- digital and digital-to-analogue conversion. Both have 8 bit put, and ignores signals on the data bus that are intended for resolution, which is more than adequate for most practical other devices. The converter used in this project has a built- applications. The analogue output has an output voltage in data latch, and it can therefore be fed direct from the com- range which is adjustable from 0 to 2.55 volts to about 0 to puter's data bus. An address decoder circuit provides the 10 volts, but with additional circuitry the output voltage latching pulse when data is written to the converter. range could easily be converted to any desired span within The DAC has a 2.55 vcIt reference source, which sets the reason. The analogue input has adjustable sensitivity, with maximum output voltage at the same figure. This gives a the full scale value variable from 2.55 volts to about 25 nominal 0 to 2.55 volt output range in 10 millivolt (0.01 volts. Again, with suitable additional circuitry practically any volt) steps. A variable gain amplifier enables higher max- input voltage range could be accom modated. The maximum imum output voltages to be obtained, up to a maximum of a rate of conversion is guaranteed to be no less than 66000 little over 10 volts. Of course, with a higher maximum output per second, and in most cases in excess of 100000 per voltage there are still only 256 different output levels, and second can be achieved. Even the guaranteed rate is fast the output increments in steps of more than 10 millivolts. enough for most high speed applications such as digitising However, for most applications, such as motor speed con- audio signals. trollers and even audio applications, the resolution of an 8 bit converter is at least adequate. The amplifier gives the unit SYSTE M OPERATION a low output impedance, but without additional buffering The block diagram of Fig. 1 helps to explain the overall output currents of no more than a few milliamps should be way in which the unit functions. The digital-to-analogue con- drawn. verter is the more simple of the two converters. This consists The analogue-to-digital converter is of the successive ap- basically of a precision 2.55 volt reference source, a resistor proximation type. This incorporates a digital-to-analogue network (known as an R-2R network) and eight electronic converter which is driven by a fairly complex control logic switches. The electronic switches are controlled by the eight circuit. The eight outputs of this control circuit constitute the

1-K 579AI ENABLE LATCH/ DATABUS D A C. AMPLIFIER -0 OUT

ADC ATTENUATOR ENABLE

CLOCK INVERTER

ADDRESS Bus DECODER

Fig. 1. Block diagram

ctical Electronics February 1985 The device used in this project does not have a built-in output of the-ADC. The output of the DAC is fed to one input of a comparator, and the input signal is fed to the other input clock oscillator, and a simple C-R oscillator is used to of the comparator. When a trigger pulse is received at the provide the clock signal. The "start conversion" pulse is "start conversion" input the most significant bit is set at one, provided by the address decoder. The converter provides its but the other bits are all set at zero. If the output from the output via an 8 bit buffer which has three-state outputs, and it can therefore be connected direct to the Spectrum's data DAC is at a higher potential than the input signal the most bus. The "enable" pulse for the outputs is obtained from the significant bit is left at one, otherwise it is reset to zero. On the next clock cycle bit 6 is set to one, and, as before, it is address decoder, but an inverter is needed to give a signal of the right polarity. The converter has a nominal full scale sen- either left at one or reset to zero depehding on whether or not the output of the DAC is at a higher voltage than the in- sitivity of 2.55 volts, but a variable attenuator at the input of put signal. On the next clock cycle bit 5 is set to one, and the the unit enables this to be reduced somewhat if required. process is repeated with this bit. In fact the same process is CIRCUIT DESCRIPTION used for all eight bits, and at the end of this procedure the 8 The full circuit diagram of the Spectrum Analogue Board bit binary number fed to the DAC is a valid digital represen- appears in Fig. 2. tation of the input voltage. This method is reasonably fast, All the address decoding is carried out by IC3 which is a with the conversion taking no more than nine clock cycles, 74LS138 3 to 8 line decoder. The Spectrum has a Z80A but successive approximation converters are reasonably microprocessor, but it uses a non-standard method of in- inexpensive. put/output mapping. The general scheme of things is to have the address lines normally high, with one of the lower lines +12 VO being taken low to activate an input/output device. Some of

+59 0 the upper address lines are occasionally used to provide additional information to an input/output device. This leaves address lines A5 to A7 free for user add-ons. In this case A5 and the IORQ lines are fed to the negative enable inputs of 3 IC3, and A5 must be taken low when reading from or writing 6 IC4 °OUTPUT 94 LF351 to either section of the port (the IORQ line automatically

D3 goes low when a BASIC IN or OUT instruction is used). ICI 22k The three main inputs of IC3 are fed from the read (RD) 29428 OV and write (WR) lines plus address line A6. This gives four VR2 10k usable outputs from IC3, two when reading and two when writing (four outputs are always high since the read and write lines never go low simultaneously). This is adequate for Cr= Cl 2,N2 our purposes as only two write outputs and one read output are needed in this application. When writing data to the DAC

105- 741.514 the instruction OUT 65439,X is used, where X is the value PIN 14 +5V written to the converter. This takes the write and A6 lines PIN 7 OV 993 low while the value written is present on the data bus, giving 93 390 an output pulse from output 2 (pin 13) of IC3. Other 96 addresses can in fact be used, but it is best to use 65439 as 95 820k 2k2 this places the address lines apart from A5 and A6 high, so 02 IC5b IC5c that unwanted operation of any internal input/output circuits 9 03 is avoided. IC2 29427 IC1 is the DAC device, and this is the popular Ferranti D4 .11-- IC5a C3 13 lrIF ZN428. It has an integral 2.55 volt reference source, but this 13 05 requires discrete load resistor R1 and decoupling capacitor OV Cl. IC4 is an ordinary operational amplifier non-inverting D6 mode circuit, and this amplifies and buffers the output of 07 -.1 1 IC1. VR1 enables the closed loop voltage gain to be varied

C2 from unity to about 5 or so, but in practice the +12 volt supply used for IC4 limits the maximum output potential to about 10 or 11 volts. VR2 is the offset null control, and this +5V is adjusted to trim the minimum output voltage of the unit to 6 16 zero volts. The ADC is based on IC2 which is a Ferranti ZN427. Like WO O -, the ZN428, this has a built-in 2.55 volt reference source

RD 0 -1 which requires a discrete load resistor and decoupling INPUT capacitor (R3 and C2 respectively). R1 is part of the high A6 IC3 994 74LS138 speed comparator, and this is fed from a negative supply so 100k A5 0 that comparator will respond properly to voltages right down

5 to zero volts. R7 biases the input of IC2 to the earth rail and 97 IORE00- *-- • 8k2 VR3 plus R5 are used to provide a small positive bias which gives improved accuracy at low input voltges. VR4, together PE 5804 OV 0 with the input resistance of the circuit, acts as a variable

Fig. 2. Circuit diagram of the DAC/ADC board attenuator.

16 Practical Electronics February 1985 PE577 A

45 4 A6 +I2V • 5V WR RD I IORO

R C) )

44 OUTPUT

TO EDGE CONNECTOR -* EARTH

-4-( ® VR / 111 411

R7 (.111 04 4

03 + C3 05 DE • 02 R6

DI DO • • D7

S. 123 he OV +5V 4

INPUT

Fig. 3. Component layout of the p.c.b.

COMPONENTS . IC5 is a 74LS14 hex inverting Schmitt Trigger, but in this circuit only three sections of IC5 are utilised. One of these Resistors (IC5c) acts as the clock oscillator in conjunction with feed- R1 68k back resistor R6 and timing capacitor C3. IC5b merely acts R2, R3 390 (2 off) R4 22k as a buffer at the output of IC5c. The clock frequency is ap- R5 820k proximately 600kHz, which is the maximum guaranteed R6 2k2 clock frequency for the ZN427. However, with most devices R7 8k2 a substantially higher clock frequency is quite acceptable, VR1, VR4 100k 0.1W hor. pre-set (2 off) VR2 10k 0.1W hor. pre-set and where high operating speed is essential using a VR3 1M 0.1W hor. pre-set somewhat lower value for C3 to give a higher clock fre- All fixed resistors are 0.25W 5% carbon quency of up to about 1MHz should give satisfactory results. The "start conversion" pulse is taken from output 6 (pin 9) Capacitors of IC3, and is generated using the instruction "OUT Cl , C2 4.2 63V radial elect (2 off) 65503,0" (the value written can be any valid quantity since C3 1nF carbonate the pulse is obtained direct from the address decoder and C4 100nF ceramic not from the data bus). The port is read using the instruction Semiconductors "IN 65503". This gives a negative pulse from output 5 (pin 'Cl ZN428E 10) of IC3, but this is inverted by IC5a to give the required IC2 ZN427E positive pulse to IC2. IC3 74LS138 At least nine clock cycles must be allowed to elapse bet- IC4 LF351 ween sending the "start conversion" pulse and reading the IC5 74LS14 port, to ensure that the circuit has had time to compleYe the Miscellaneous conversion. There is no problem in BASIC since the slow Printed circuit board (502-02) speed of this language means that the conversion will 2 x 28 way 0.1 inch pitch edge connector always have been comfortably completed before the port is 8 pin di.). i.c. socket read. The situation is different when using machine code, 14 pin d.j.'. i.c. socket Two 16 pin i.c. sockets and it may them be necessary to use a delay loop to prevent 18 pin d.i.l. i.c. socket a premature reading of the converter from being taken. The Ribbon cable, wire, Veropins, solder, etc. ZN427 has an "end of conversion" status outpu't, but no means of reading this have been included in this unit, and as

Practical Electronics February 1985 17 -55 RD 04 05 02 00 the length of time taken for a conversion is virtually constant PE578A a delay loop is a perfectly practical way of doing things. The circuit requires +5, +12, and -5 volt supplies. These are all provided by the Spectrum from its expansion bus, and +11111T 1131161'1 01 no other power source is required. 1111111111 11111 1 1 11 1111 CONSTRUCTION The component layout of the printed circuit board is 11111111111111111111 H 1111 shown in Fig. 3. There are a number of link wires and it is probably best to fit these first. 22 s.w.g. tinned copper wire is suitable for the links. None of the integrated circuits are MOS types, but it is advisable to use sockets for these, especially in the cases of IC1 and 1C2 which are not the cheapest of devices. The integrated circuits do no all have Fig. 4. Connection details for the Spectru m edge connector the same orientation, so be careful to fit them onto the board the right way round. Connection to the Spectrum is via a piece of 17 way rib- An output potential of around 7 to 8 volts should then be bon cable about 0.5 metres long. It is unlikely that 17 way obtained. By adjusting VR1 any desired maximum output cable will be available, but it is easy to cut down a piece of voltage of between 2.55 volts and about 10 volts or so can 20 way cable to the required number of ways. Connection to be set. Repeat this procedure a couple of times to make sure the board should not prove to be difficult provided the end of that everything is set up as accurately as possible. each lead first has a small amount of insulation removed and • To check the ADC and facilitate its adjustment type in the is tinned with a small amount of solder. A 2 by 28 way 0.1 following short test program:- inch edge connector is needed to make the connections to 10 OUT 65503,0 the expansion bus of the Spectrum. Suitable connectors 20 PRINT IN 65503 complete with a polarising key are now readily available. 30 GOTO 10 Fig. 4 gives connection details for the edge connector. When the program is run it should return a series of very low readings (0 or 1). Set VR4 at maximum resistance (fully ADJUST MENT counterclockwise), VR3 at a midway setting, and connect an Connect the unit to the Spectrum prior to switching on. input voltage to the unit that is equal to the desired full scale The Spectrum should then operate normally - switch off value. This should be in the range 2.55 to 25 volts. Run the immediately and recheck all the wiring if it does not. program and set VR4 just far enough in a clockwise direction Assuming all is well, adjust the DAC first. Set VR1 and to give returned values of 255. VR2 at a roughly midway setting, and then type the follow- In order to adjust VR3 an input voltage that produces 5 ing command into the computer:- millivolts at pin 6 of IC2 should be applied to the cirrcuit. In OUT 65439,0 other words an input potential that is 1/510th of the full This should give a low output voltage from the unit, and by scale input voltage is required. VR3 is then adjusted to give a adjusting VR2 it should be possible to trim the output poten- series of reading that (more or less) alternate between 0 and tial to precisely zero volts. Next type into the computer the 1. It is not essential to carry out this procedure, and accurate com mand:- results will be obtained if VR3 is simply set for about half OUT 65439,255 maximum resistance.

SURPLUS to requirements MC6809E, OSCILLOSCOPE Heath 10-4555 £150 .ono 5N74LS783 Synchronous address multiplexer also other instruments P.C. bridge etc. OfferS, chips. £4.00 each. 10+ £35. SN74LS783 data good condition, sold separately. Mr. A. Ewing, 9 £2.50. Mr. N. E. Spiers, 114 Green Way, Tun- Croft Crescent, Markinch, Glenrothes, Fife KY7 bridge Wells, Kent TN2 3JN. 6EH, Scotland. CLEARTONE graphic equaliser (battery) 7 W ANTE D AY-3-1270 linear i.c. or S WOP Brothers EP44 computer printer/ channel mono, with master volume control. New RS-3-1270. Mr. J. F. Wilson, 233 Broomlee typewriter RS232 for oscilloscope. Mr. Small, 8 £22 inc. p&p. F. C. Smith, 283 Leeds Road, Close, Newton Aycliffe, Co. Durham. Tel: Ayeliffe, Cherrytree Road, Chinnor, Oxon. Newton Hill, Wakefield WF1 2JQ. Tel: 0924 312130. W ANTED Texas Microprocessor TMS 1000. 374122. W ANTED two track record head for B & 0' Please write to: Abbass Rezaei. PO Box 62, 10 x 8255A £70 the lot or £8 each. Also printer record 1800 RTOR deck. Mr. C. BreSsington, •17 Najafabad, Isfahan, Iran. leads for Dragon 32, BBC £9.95 each. Station Road, Ystrad Mynach, Mid-Glamorgan. FREE -sacks of old components. Mostly R. Vowles, 3 Orchard Waye, Uxbridge, Middx. Tel: 0443 813005. TV/valves, to be collected in Oldham. Details: U88 2BN. Tel: 0895 54720. EIGHT Philips LVC 150 2÷hr. video tapes. Har- 0923 20751, Mr. V. R. Halsall. W ANTED two 5N76001 i/c as used in the dly used. Offers plus postage. Mr. L., T. Hill, 14 FOUR pairs matched boxed speakers, £8 per Heathfield TV. Mr. Kendall, 4 Howlets Terrace, Rothesay Terrace, Bedlington, Northumberland. pair. T, A. J. Cooling, 4 Norfolk Road, East Ham, Chelmondiston, Ipswich IP9 10X. Tel: Bedlington 825967. London E6 2NJ. 5 x 7 dot Matrix printer 7 colours: 80 cols. W ANTED data or specimens of early transistor W ANTED Manuals for Cossor oscilloscope type parallel interface adjustable tractor feed VGC types. Good prices paid. Write for full details: Mr. 1035, and Harley oscilloscope type 13A. M. 0. £220 o.n.o. S. Walker. Tel: 0865 750600 even- Andrew Wylie, 18 Rue de Lausanne, 1201 A. Chari, Ladersattravagen 97 3 Tr, 175 70 Jar- ings. Geneva, Switzerland. falls, Sweden. CAR battery voltage monitor - graces any car. MICROSYNTH Synthesiser built and tested, PAL: information on PCBs making, from As new in immaculate condition £3.45. Russell with speaker and homemade stand £150. 8 amateur and experts. A. Larry, 56 Becher Street, Oakes, 32 Wigan Road, Winstanley, Wigan, Stourton Road, Witham, Essex. Tel: Witham , 514556. Derby DE3 8N N. Lancs. WN5 7XS. UK101 software for sale or swops. Send for list COPIES available from private collection early CO MPONENTS transistors mainly OC/AC/BC, of programs. Mr. P. Hale, 31 South Road, Stour- service sheets radios TVs etc. £1 + large SAE. capacitors, resistors, chips, pots, relays, motors and other. 16 lb. £20. Mr. Turner, 4 Mill Fields, bridge, West Midlands 0Y8 3YA. State make, model. Maurice Small, 8 Cherry Tree Newtown, Powys. Tel: 0686 27862. 'NIGHTRIDER' car lights sequencers, drives Road, Chinnor, Oxon. 0X9 40Y. W ANTED service circuit diagrams Sugden C51 nine channels van-speed. Easy wiring all HA MEG oscilloscope HM203-4 dual beam A51 purchase hire to copy. Good price paid. negative-ground cars £40 complete. Mr. S. M. 20MHz with probes f195. Tel: Southampton Richards, Maesyffynnon, CaehoPkin Road, Budzinski, 16 Laburnum House, Malpas Road, 557386. Mr. D. Couchman„.8 Grosvenor Gar- Abercrave, Swansea. Tel: 0639 730629. London SE4 1BL. dens, Southampton.

18 Practical Electronics February 1985 Top Value In Test Equipment

Select the Function and It Selects the Range Automatically

• Folds Into Compact Case • Automatic Power Off When Case Is Shut With Wrist Strap - • Automatic Polarity !A 25-Range Folding Multimeter. Features include fuse and g Folding LCD Multimeter With Autoranging. Features surge-absorber protection, banana-type probe jacks and 4" 3- extra large 11 /16" non-glare display with adjustable viewing colour mirrored meter with automatic shunt protection (when angle, a "beep" indicator for quick continuity testing, and zero- folded shut). DC Volts: 0 to 1200. AC Volts: 0 to 1200. DC ohms adjust for super-accurate low resistance Current: 0-60µA, 3-30-300 mA. Resistance: 0-2-20-200K-2 measurements. DC volts to 1000. AC volts to 500. Up to 10 megohms (centre scale 24). dB; —20 to +63 dB. Requires amps AC and DC. Resistance to 2 megohms. Open: 10 7/a x "AA" battery. 22-211 • £19.95 45/6 x 11/2". Requires two "AA" batteries. 22-193 .. £64.95

Transistor Checker and Reference Books Digital Logic Probe

El £995 £1 295 E'

El Dynamic Transistor Checker. Makes Go/ No-Go tests on small-signal and power types - and allow you to match similar transistors. Indicates relative current gain, "opens" and r • "shorts". Requires "AA" battery. E l Semiconductor Reference Guide. 22-025 £9.95 1985 edition! Exclusive cross-reference and substitution section lists over 80,000 types. E Digital Logic Probe. The fast way to 276-4008 £3.49 "peek inside" TTL, LS and CMOS digital E Getting Started In Electronics. The circuits. Colour-coded LEDs indicate perfect introduction to the exciting world of high, low or pulsed logic states (up to electronics. Learn to build your own circuits. 10 MHz). Minimum detachable pulse Overload 128 pages. 276-5003 £2.49 width: 50 ns. 36" leads with clips and r Timer IC Mini-Notebook. An excellent obtain power from circuit under test. Polarity reference and hobby book. Large schematic Low current drain. Protected diagrams. 32 pages. 276-5010 99p 22-302 £12.95

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Practical Electronics February 1985 19 era „ use.1 Mail order & shop: -[111-1 441 PR NCES ROAD, DARTFORD, KENT DA1 1RB Telephone: (0322) 91454

ORDERING INFORMATION: pa. 50p on orders less than £20 in value otherwise post free. All components fu I spec & guaranteed. Discounts avai able on orders over £50 - phone fo details. For unlisted components SKYBRIDGE phone for price Goods normally despatched by return post.

CABLE Per metre ving, ties. fixings 22/16 10p 10M . 2009 BNC square 0-type n ang skt FUSEWARE Range of heat Round 12" TRANS- wire wrap 90 in stock-Phone for 22/25 10p 18.432M 270p skt 100p 15W pea 20rnrn panel sinks available - 60W 21162p FORMERS Red/white/black details 22/35 11p 26.54M 200p BNC free skt 110p D.type rt ang skt holder 46p Phone for quo- Round 12 6-0-6 V. 100mA solid 1/.6 22/63 15p 26 59M 200p BNC 1M. adapt. 25W pee 1¼" panel tation. 100W 4073p 167p CAPACITORS 26.64M 200p - holder 59p Round 12" 11 colours 4p 47/10 10p 140p D WPe n ang plug SPEAKERS 60-6 V. 2009 20mm chassis ISOW 4336p Hookup 7/.2 Plate ceramic 47/16 11p 26.69M BNC T adapt. 3009 O W pee Miniature buzzer 250mA 185p holder 14p Round 15" 11 colours 3p 1.8pF - 22nF 8p 47/25. 13p 26 74M 2009 X ISse ug 5op D-1V0e ft ang plug 6V or 12V 909 9-0.9 V. 1/4" chassis 150W 7186p Heavy duty. ..32/.2 Disc 47/35 15p 26 79M 2009 15W pea Ultrasonic ....BON, 100mA 167p holder 17p Round 15' 4 colours 15p 10pF 109 47/63 26.8M 200p Small reducer 20p D-type rt ang plug transducers 9-0-9 V. Extraflex 47pF 15p 100/10 lip 26 995M 200p Large inducer 2Op9. 25W poa Line holder 14p 200W 8736p 250rnA 166p taL.5rt p pair 13p 27.045M 200p ,3 Fuse clips ..... 3p Round 18 - red/black 16p 100/16 . Covers 9 1209 E ,rical 503" 12-0.12 V. 20rtim fuses Tinned copper per il9gt pFP PriPs 100/25 . 15p 27.095M 200p VHF round skt 50p Covers 15. 1200 200W 0108 50mA 166p 100mA, 150mA, 40, reel 1000pF 11p 100/35. 19p 27.145M 200p VHFsquare sk1 50p Covers 25 . 1309 12-0-12 V. 250mA, 500mA, SWG16 80p 2200pF lip 100/63 25p 27.195M 200p Ebow adapt. poa Latches 9 30p Motorola Fusco 10OrnA hip 1A, 1.5A, 2A. 3A. SWG18 85p .01 0 F 59 220/16 . 15p 27.245M 2009 Straight adapt 50P Latches 15 .50p tweeters 2' 231p 12-0-12 V. 5A 99 SWG20 95p .0220 F 50 220/25 20p 27.255M 200p VHF T adapt 160p Latches 25 .110p 314" 697p 250mA 188p .047uF Op Female T 20rnm ant/surge SWG22 95p 220/35 23p Power plug pt ic I 7x5".... 2"x6" horn 938p 0-12/0-12 V. CONNECTORS fuses 500mA, IA, 2 SWG24 960 if 8p 220/63 33p adapt 180p 2 lmm .169 2x5" horn 796p 500tnA 369p Croc clips 10p 2A 12p En copper per 20z .47uF 159 470/16 . 239 XLR line plug 11113p Power plug Elliptical 8"x5" 2/4" horn 457p 9-0-9 V. IA 2133p Terminal post 40p 114" fuses 103mA, reel SWG14 70p Polystyrene 470/25 27p XLR chassis 2 Stern 15p 5W .... 386p 3%" 624p 12.0-12 V. IA 3150p 1mm plug 20p 150mA, 250mA, SWG16 93p 22pF 13p 470/35 . 31p skt 330p Elliptical 8"x5" 4" x 10" 1435p 15-0-15 V. IA 433p IEC line skt .95p 500mA, IA 2A SWG18 90p 47pF 8p 470/63 489 1mrn socket 15p XLR line skt 230p 1EC chassis 8W 521p Crossovers 20-0-20 V. 2mm plug 20p 3A, 5A, 10A, 13A, SWG20 . 90p 6/3pF Op 1000/10 24p XLR chassis plug 90p Elli teal 9"o6",... 2 way 15W 1Et8p 1.5A 538p 90 2rnm socket 15p 15A 9p 100pF Op 1000/16 299 plug 160p !EC chassis skt 90p 4319 2 way 100W 690p 0-12.162024-30 V. 3mrn plug 20p 1" fuses 2A, 3A, SWG24 105p 150pF Bp 1000/25 41p DIN plugs ISC line plug 70p Miniature 1" ..90p 3 way 25W 193p 1A 6669 3mm socket 15p 5A, 13A 15p SWG26 I05p 220pF 8p 1000/35 45p 2 pin 10p Bulgin 9429 50p Miniature 3 way 40W 3381, 6-0-8 V. 2A 440p SWG28 105p 4rnm plug 15p RESISTORS 3 way 60W 502p 330p F Bp 1000/63 75p DIN plugs Bulgin P646 166p 1% 909 9-0-9 V. 2A 476p 4mrn socket 15p % W 5% 3 way 100W 1346p SWG30 110p 470pF Op 2200/10 39p 3 pin 15p Bulgin 9430 1259 Miniature 12-0-12 V. 2A 538p SWG33 1109 Phono plug 10p DIN plugs E24 2p 4 way 80W 626p 0-12/0-12 V. 560p E 8p 2200/16 46p Bulgin P649 135p I% 90p SWG34 1159 Phono line skt .209 4 pin 259 .4W 1% 2A 538p 680PF Bp 2200/25 55p Bulgin P650 1109 Miniature SWG36 125p Jack plug DIN plugs E24 79 0-12-15-20-24-30 V. 1000pF Bulgin P635 100p 2.5mm 15p 5 pin A 15p 1W 5% S.OP SWITCHES SWG38 :: 1500pF ggV/213 ;:tpo Miniature 2A 0009 Jack plug Bulgin P636 130p E12 10p Toggle Std SWG40 1509 2200pF 8p 3300/35 329 DIN plug 5 pin 2% ...... 90p 20-0-20 V. 2A 746p Figure 8 per metre 3.5mm 15p Bulgin 9551 300p 3W was L22-1R3Op SPST 47p 4700/10 59p 240° 20p Miniature 224" OR 30-0-30 V. 2A 9339 Jack skt Bulgin 9552 100p 3W new Tooptglre Std 71.25 13p 417000;°9 Op8p 4700/16 . 74 DIN plug 5 pin 90p 12.0-12 V. 3A 721p 2 5mm 15p Bulgin 5A2403 52p Coloured ribbon 5600pF 10p 4700/25 1039 360° 309 2R2 20p Miniature 2/4" 0-15 V. 3*.. 647p Jack skt 180p 7W ww 30p per foot DIN plug 6 pin 40p 'A 6-0-6 V. 4A 5313p 6800pF 10p Non-polarised MR 1009 n 10 Way 209 3.5rnm 159 DIN plug 7 pin 20p Bulgin SA2404 95p lOW new 35p ;PO' 68p 9-0.9 V. 4A 687p e;.5001 FF 14p 259 Bulgin SA2190 50p Round 5" 4W 174p Toggle Min 20 way 40p Jack skt line DIN plug Spin 130p 25W new 170p 12-0-12 V. 4A 8459 199 220F 25p Bulgin 5A1862 50p Round 5" 25W ... 34 WE1Y 809 2 5rnrn 30p DIN skts 2 pin .10p Ww Pots. 70p 0-15 V. 6A • .949p 3.3uF 25p 409p Toggle Mm tF 7MF 25p Jack skt line DIN skts 3 pin 20p Bulgin 5A2111 3W High Mains per metre 2 49p 4.7pE 25p Round 5" 60W ... 6-0-6 V. 8A 980p core Oval 35 .209 3 5mm 259 DIN skts 4 pin 15p 200p quern 2759 SPOT 11/off 83p 12-0-12 V. Polyester 6.8uF 50p 15137p Torottqe Min Round 6A • .46p Jack plug 14- DIN skts Bulgy) 5A2019A IOR 5R 50R BA 1615p 10uF 259 115p• 3 core Round 3A mono 209 5 pin A 15p 150p 100111, 250R, 930R, SICF A P 220 F 35p Round 5/14 " IOW Toroids, 30VA 35p Jack plug %- DIN skts Bulgin SA2020 1k. Sk. 10k, 50k. 0220 F 8p 33pF 40p By 950 Round 6A 50p stereo 30p 5 pin El 20p 140p 476p TArcnr4..11ip 033pF Op 470F 40p Round 514" 15W 30VA 9V 960p Round 13A Wiz Jack skt 4" DIN skts 6 pin 20p Bulgin 5A2367 SEMICON- Toggle 047v F . 9p 1000F 70p 771p 30VA 12V .960p mono DIN skts 7 pin 20p 180p DUCTORS 118Y "'" 2099 002430F 9p Thousands of Round 6" 5W 297p Toggle Min 4PDT 30VA 15V .950p Power Jack skt %- DIN line skt Bulgin 5A2368 95p So extensive is the Other capacitors in Round 8" 60W c/off 2449 30VA 18V .950p 1 rnrn TErE . .40p stereo 35p 2 pin 159 range of listed se Ig:F 159: stock i.e. Many other con. 1632p Push to make 20p 50VA 6V. 1150p 1.5 mm T&E 45p Jack skt line DIN line skt miconductors Silvered Mica. 1% nectors, adapters Round 614" 50VA 9V 1150p 2.5 mm THE 60p 22pF 11p mono 250 Spin 3(19 Please send large Push to break 20p Polystyrene. 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Variable etc. COAX plug • 15p 15W 150p LED Std green lep 1066 10p 100/ 423p Rotary 49 3W .62p BOVA 30Y. .12009 Twin round 20p 2uF 469 etc. COAX skt surf 309 D/type plug LED Std yellowl5p OIL sockets 8 pin Round 8" LED Min red 109 Suite min 120VA 30V 1300p Figure 8 min 20p Electrolytic CRYSTALS COAX skt fiush26p 25W 150p 9P Round 8" DPDT 22p 160VA 35V 1500p 8 std. • • 3g: ,F/V 1/63 100k COAX line ski 45p 0-type skt LED Min green 18p 14 pin 11p Figure 7 89 Sude std 300VA 35V 2000p 4 2.2/50 9p 1M 6009 COAX coupler 459 O W 140p LED Min 16 pin ... 12p 60W 13469 DPOT 22p 500V5 35V 26509 Spiral wrap 4.7/63 99 2M 2209 CAR aerial 0-type skt yellow 18p 18 pin 16p Round 10" DIP 4W 105p All tormds have 1/8" 15p 10/16 8p 3.276110.4 pork lug 15W 200p LED clip std 3p 20 pin 17p lOW 700p DIP 640 128p two isolated se- 20p 10/25 80 'IM 1809 plug 211:)' D-type skt LED clip min 3p 22 pin 20p Round 10" 156p condaries at volta '" 46p 10/35 10p ONC plug 10Dp 25W 460p Large range of pa. 24 pin 21p 20W 1113p 4.19304M 320p DIP 10W ... 184p ges shown Wide range of ca- 10/63 13p 4433619M 320p BNC round D-type rt ang skt nel lampholders, 28 pin 24p Round 10" Microswitch .83p ble markers, Mee- 22/10 Bp' 6 144M 130p ski 100p O W poa de luxe LEDs, etc. 40 pin 36p 30W poa

SEND THIS - VOUCHER WITH THE START OF YOUR ORDER OR BRING IT WITH YOU! SOMETHING NEW DIGITAL CAPACITANCE DIGITAL If you are leaving college and planning a career in modern METER (UK C/P 651)/ MULTIMETERS communications or if your present job lacks interest and Large LCD OiSplay 8 ranges 0 (p1(0 (UK C/P65p) challenge then why not join us in government communica- 2500 Mid 1069 501 S = Slide switches WITH VOUCHER £62.55 R= Rotary tions headquarters? We are recruiting RADIO OFFICERS PB - Push butlon who after initial training will become members of an organi- DC POWER •I(0305 (S) 14 Range 100 0€ 2M ohm 1029 801 WITH VOUCHER EM U sation that is in the forefront of communications technology. SUPPLIES 0310 (PEI} 28 Range 105 AC/DC 20M ohm Government Communications Headquarters can offer you a -aka 220/240 AC input (043 501 WITH VOUCHER £39.15 satisfying and rewarding career in the wide field of (UK C/P 01 001 o w 95C PI) 26 Range 10A AC/DC 20M ohm 1203 13 8 volt 3 Amp DC output For 01112 volt 1044 501 WITH VOUCHER £40.05 communications. DC equipment) £11 95 WITH VOUCHER 010.76 • 3510 (Fn RangelOA AC/DC 20M ohm Hle tester 241 Meter indicator Amps/Volts 0/30 Von Training involves a 32 week course (38 weeks' if you come cont buzzer 1046 521 WITH VOUCHER E41.89 Oft Amp 1037 951 WITH VOUCHER £34.16 ME540 (R) Man/Auto 19 Range 10A AC/DC straight from nautical college) which will fit you for appoint- 243 3 Amp version 1059 95) 20M ohm (047 77) WITH VOUCHER £42.99 ment to RADIO OFFICER. WITH VOUCHER E53.96 • £1103350 OR) Autorange 18 Range 106 AC/DC 2M ohm Cont Buzier 049 951 Not only will you find the work as a RADIO OFFICER ANALOGUE WITH VOUCHER £44.95 extremely interesting but there are also good prospects for MULTIMETERS •WiTH CARRY CASE promotion, opportunities for overseas service and a good (UK C/P 65p) salary. Add to this the security of working for an important NC 1015 10K/volt TRANSISTOR TESTER 15 Range pocket 1£8 951 C/P 65p) government department and you could really have the start WITH VOUCHER 0.06 Direct reading ot Hte and leakage of something new. N115611 10K/voll 22 Range (012 95) lor NPN/PNP transistors WITH VOUCHER £11.95 8 Oates (£27 951 WITH VOUCHER £25.16 The basic requirement for the job is two years' radio operat- 1028Z 206/0011 22 Range 10A DC ing experience or hold a PMG, MPT, MRGC or be about to i015 95/ WITH VOUCHER 014.34 PROBE KIT (UK C/P 45p) For obtain MRGC. Registered disabled people are welcome to £1130010 206/001119 Range plus Hie tett all scopes etc BNC conned°, switchable 01-010 (014501 WITH VOUCHER £13.05 in wallet (Ell 501 WITH VOUCHER £10.35 apply. 5031 50K/volt Range doubler 1060€ 20M on,), For full details and application form 'phone 0242 32912/3 or (021 95) WITH VOUCHER £19.70 SIGNAL INJECTOR (UK C/P 45p) 3330 306A/ 26 range 100 AC/DC Pencil type AF/RF output 1000's sold write to the Recruitment Officer, Room A1108, GCHQ, t 0 ohm (224 95) WITH VOUCHER £22.46 (04 95) WITH Priors Road, Cheltenham, Glos. Pras atorne of press approximately VOUCHER 04.49 6 weeks to bar...anon 0800 10% DISCOUNT VOUCHER C NOTE:011er closes 311 85 HENRY'S Apples only for gcocls as about 301 EDGWARE ROAD LONDON W2 1BN All prices (while stocks available prepaid by posl cs tor callers lone TELEPHONE 01- 724 3564 include VAT Recruitment Office, Government Communications Headquarters, Abele, per lotal owe') Oakley, Priors Road, Cheltenham, 404 EDGWARE ROAD LONDON W2 lED Open 6 days Voucher mist accompany order TELEPHONE 01 - 724 0323 a week (UK C/P extra as incleatee) Gloucestershire, GL52 5AJ. -1

2(1 Practical Electronics February 1985 Information Technology will have to pay fees to make the university 9 self-financing. Information Technology which seemed Fears have already been expressed by so novel (although hardly new) only three egalitarians that the university will be anti- It years ago has now become accepted as the social because it will create an elite of the norm and no more exciting than radio or already advantaged who can afford the television. Some pessimists are already fees. Nonsense, of course. We need more, saying that Britain has been losing grOund not less, centres of educational excellence. in this growing sector of industry. Their INOUSlOY fears are based on the. increase in imported equipment compared with indigenous Improvisation production. I remember at a press conference At the higher levels of the technique the organised by a Ministry of Defence elec- Alvey program me is now gaining momen- tronics establishment asking how we would NOS001 tum. Two new major contracts were awar- get on in a real war when the time scale of ded towards the end of last year. One equipment development stretched over a carries the painfully contrived acronym of period of years even when the equipment ADMIRAL derived from ADvanced Mega was comparatively simple. I had in mind the Internet Research for ALvey. The other is very few weeks which elapsed in 1940 bet- merely called the Speech Recognition Pro- ween the alarming discovery that the Ger- ject. mans were using magnetic mines and the The ADMIRAL contract is a £3 million countermeasure (degaussing of ships) joint venture being coordinated by GEC devised and implemented. And this was Research Laboratories. Partners are Univer- only one example of many rapid develop- Outlook sity College, London, The University of Lon- ments of that war. don Computer Centre and British Telecom I contrasted this with over 10 years of Everyone in business breathed a sigh of Research Laboratories. development of the Clansman radio system. relief once the US presidential election was The system will link local area networks before it came into service. I was not very over. The two-year run-up is almost un- (LANS) through a 'mega internet overlay' to impressed with the reply which was more bearable for its unsettling effect. produce a single large system of data or less that we would probably muddle All indications, are that 1985 will be a networks. The key feature is to allow high through as we always had done in the past. ood, though possibly hard year for the ,g speed intercom munication between dis- My confidence has now been restored electronics industry. In 1983 the number of similar equipment. It appears to be a te-jig (well, almost) by Alfred Price in his new 'small companies starting up provided a net of part of the Project Universe program me book 'Harrier & Sea Harrier at War', gain of 47,000. The 1984 figures, not yet originally initiated by the Department of published by Ian Allan Ltd. In it he' available, are expected to beat this record. Trade and Industry and later transferred to describes 'Blue Eric', an electronic counter- and there is no reason why 1985 should be the Alvey Directorate. measure system needed urgently for the \iicirSe. A significant number of the new. The Voice recognition project is funded Falklands war. If Harriers were to be start-ups will be in or associated with the with £2 million and is centred on British operationally successful in the South Atlan- electronics industry. Telecom Research Laboratories_ with tic they would need self-protection against Foreign investment in the UK continues collaboration from Cambridge University Argentine radar installations. at a high level. The prolonged miners' strike and Logica. Although most schoolchildren The threat was evaluated from normal was apparently seen overseas as a one-off are acquiring keyboard skills it is also military intelligence which already had out-of-character industrial relations recognised that speech is the most natural details of the characteristics of radar equip- problem and not typical of the 'new realism' form of com munication between people ment in service with Argentine forces. Ex- in British industry. in any case no foreign and the same applies between people and isting electronic warfare pods (e.g. for Tor- companies would want to invest in coal computers. nado and Buccaneer) were too large and mining and potential investors may be im- Present voice recognition systems are heavy for the Harrier so it was decided to pressed by , the relative ease with which primitive and generally respond only to use elements- of the Sky Shadow equip- British industry carried on through what single-word voice com mands. It is hoped to ment and fit them in a modified gun pod was intended to be a crippling exercise. expand into true verbal dialogue between which would meet the weight and size re- Expansions and new Starts planned last person and computer so that anyone who quirements as well as the jam ming year will begin to take effect. If we look at can talk can, for example, find what is re- capability. Scotland's Silicon Glen there are now quired from a data base without necessarily Marconi Defence Systems were prime nearly 300 electronics companies employ- having any keyboard skill. contractors and completed the design, ing more than 40,000 people. Inward in- testing and delivery of operational units vestment since the Locate in Scotland within 15 days instead of an estimated two agency was'founded in 1981 has now top- Time for Schools years at normal pace and at a quarter of the Ped £1,000 million, most of it finding its It is heartening to see that schools •are cost. way into high'-tech projects. And substan- .now to be networked through The Times Blue Eric (named after its MOD project tial investment is similarly going into other Network for Schools (TINS) which will give officer" Squadron Leader Eric Annal) was areas. Even so they will not create many any school access to more than 200,000 never used in the Falklands. When the EW- new jobs, one recent estimate being for pages of information by the end of the year. equipped Harriers arrived they were groun- 10,000 in the electronics industry this year. Secondary schools of which there are ded for four days by bad weather and by the " Intense competition in personal com- 6,500 will be first to join, followed by. time they got airborne the conflict was vir- puters will force prices down so intending 27,000 primary schools. tually over, the Harriers then being used for buyers ,would probably profit by delaying Future plans exist to network British front line ground attack where the radar purchase. , Alternatively, prices could schools to those on the continental threat was negligible or non-existent. stabilise but the product improved in the mainland. Joining the network will be op- While it is comforting to know that the classic "more-bits-per-buck" context. But tional but the fees are modest and the improvisational skills of yesterday have not despite all the difficulties it will still be scheme should prove popular and exciting. been lost, one is still left wondering why an possible to score well in the consumer Then we have the proposal for a univer- EW pod for Harrier was not already market as proved by Alan Sugar's Amstrad sity devoted entirely to information available and why, in peacetime conditions, whose , pre-tax ,profits topped £9 million in technology. It has the backing of a host of equipment development times are so long A last financial year: leading electronics companies but students and the cost so great.

Practical Electronics February 1985 21 cmmoilt ZO 0 0 The Principle and the Product Tom Gaskell BA (Hons) C Eng MIEE

H E electronics industry is one of extremely rapid change. keys to be pressed per character. The right hand is always held TNew products, ideas, and standards spring up continually, in the same place above the keyboard, one finger above each promoting a continuous state of flux and development. As a key, and the shape formed by the fingers pressing the keys bears fairly young industry it is successful in discarding old and out- a relationship with the shape, or some aspect, of the character dated principles in favour of newer, more beneficial ones; if which becomes entered into the machine. That relationship is change can be shown to be worthwhile in any specific situation, sometimes obvious and direct, sometimes humorous, sometimes then that change is almost invariably made. very corny, but inevitably is easily memorable. Fig. 1 shows It comes as somewhat of a surprise, therefore, that for the some of these relationships, based on a slightly stylised layout of production of documentation, text, correspondence, and com- keys. The manufacturers suggest that they can be memorised in puter programs, the primary means of interface between the typically one hour, and certainly I have found this to be the case human being and the machine is still a QWERTY keyboard. as far as friends, colleagues, and myself have been concerned. It QWERTY is the standard layout of typewriter keys which was is very easy indeed to learn to Microwrite; far, far easier than devised very many years ago with the principle intention of touch typing, and I have tried both! Slowing Down the typist to prevent jamming of the mechanism. In this age of mechanical sophistication and electronic USING THE MACHINE keyboards the same requirement is no longer true since we can As each character is entered from the keyboard it is displayed easily prevent jamming by other means. Hence, we are left with on a single line liquid crystal display which can show up to 14 a legacy from a bygone age. The QWERTY layout is slow and characters and two control symbols. The display acts as a complex to learn, with months of training being required before 'window' on the text, and can be moved around within the text, any proficiency is achieved. For many people such training is either following new characters entered or to review what has impractical, so they are reduced to 'two finger' typing, which is already been written under the control of special commands. usually a slow and frustrating exercise. The text, as shown by the display, normally appears to shift to the left as each new character is entered by the keyboard and ap- A NE W IDEA pears at the right hand end of the display. The sixth key on the When a company brings-forth a new idea for entering text Microwriter is a second thumb key, a little below the normal into machines, it is bound to attract considerable interest. A few one, and it acts as a control key, allowing comprehensive control years ago a device called the `Microwriter' appeared. It is a of the machine's functions. It is used either on its own, or with small, self-contained machine with only six keys, which is used other keys in place of the normal thumb key. For example, en- with one hand only. The Microwriter company has been produc- tering the letter 'f' (the First Four keys pressed), but using the ing these devices in modest quantities ever since, and has control key instead of the thumb key, moves the display window recently started to advertise and promote the product in a more in the text Forward one position; 'f' for Forward —it is corny, aggressive way, with various options and accessories now but it works! Doing the same thing with the letter 'k' moves the available. window backwards. In this case, 'k' stands for Korrect, so you use it when Korrecting errors! W HAT IS A MICRO WRITER? A Microwriter is no less than a battery powered portable WILL THIS word processor. It is just a little larger than a paperback book and has very few controls—some connectors, an ON/OFF EVER REPLACE switch, a liquid crystal display, and six keys. It is placed on a desk or held in the left hand, and typed on with the right hand. THE• "OWERTY' (As yet there isn't a left handed version since there would be KEYBOARD? problems connected with the way that the 'alphabet' of letter shapes are formed, as we shall see later.) The Microwriter can communicate over a bi-directional RS232 serial link with printers, full-sized word processors, computers, etc., and can store text either internally on battery backed-up RAM, or on any conventional external cassette recorder. Characters or numerals are entered into the machine by pressing combinations of keys, rather than one key at a time as in the case of the QWERTY system. There are no markings on the keys since they can have different functions at different times, so the user is immediately forced into the excellent prin-, ciple of touch typing, and looks at the display rather than at the keys being pressed. The user, therefore, has to learn all the sequences of keys to be pressed before being able to type correctly. This is the make-or-break aspect of the Microwriter— many people are immediately put off by having to learn a potentially complex typing language. Fortunately, the people at Microwriter Ltd. have been very clever indeed in the choice of

22 Practical Electronics February 1985 EDITING AND WORD PROCESSING When text has been written it can be edited (both deletion and insertion) and reviewed by appropriate use of the control key. To read through the written material, the user has to Jump back to the beginning (control + j) then scroll Forwards (control on its own, followed by control + f); this then moves the display window along the text one word at a time, at a user selectable slow or fast rate, until you tell it to stop. The machine automatically enters 'carriage returns' at the end of each line, and ensures that these are between words, not in the middle of them. Via the control key the user can access tabulation, margin indents, document markers, page separators, alter line length, and do many other complex word processor functions. These become very difficult to memorise, and even more difficult to im- plement, and I would have thought that they would have only limited usefulness to most people. The control key is also used to suitably configure the RS232 link. Although this can be used to load text into the Microwriter, its primary use is to transmit text to a computer, word processor, or printer from the Microwriter. Full handshaking is provided, and there are user selectable baud rates, data lengths, etc., so it will interface with most R5232 based systems. All settings and text are stored in RAM with battery back-up, so nothing is lost when the power is turned off. The machine even turns the power off itself if it is not used for a few minutes, to

E E O ALPHABET - Micro writerEl RECO M MENDED LEARNING SEQUENCE Pressing the control key once, on its own, puts the Microwriter into upper case characters for just one entry, after goo S O C o oi 0 ° % which it reverts to lower case. Pressing it twice in succession, on o cO • 0 % MO P Main feature of the other hand, locks the machine into upper case continuously Streght hoe add a bar at add a bar at flrn vrreorrs e rr,L f go: G is downstroke up for I the top tot R the bottom for L ,OPPOsite to until the two thumb keys are pressed together to revert to lower case. The status of the machine is continuously shown by two Lio g 0 control symbols in a yellow coloured area at the right of the O ct 0 i Ir: 0 Lo• i 0 , 0 display. A re s' ‘sfr First Four , Most Fingers Simple punctuation is provided as part of the normal lower Horizontal of the H Top of the T completely for P Fingers for F FM Radio Make M case letter set, but more complex punctuation and numerals have to be accessed by a 'numerals shift' function. Entering the 0 0 0 letter 'n', but with the control key pressed at the same time, shifts Most 0 0 000 ommon the Microwriter into the numerals mode for one character only; Inger !Index) for The central target Space most com mon letter E - bulls eye entering this combination twice in succession locks in the numerals mode, just like the upper case mode. There's another set of character/key relationships for the punctuation, with num- ( II U0 O a • • • bers being entered by a 'count on the fingers of one hand' type of Ad,oming The dome of the I) The bump of the B First upstroke downstroke Looks like a `I technique. The requirement to shift for numerals is acceptable Either side of the com mon lin e of the A of the N for word processing applications, but would make the 0 _ 0 0 0 1 Microwriter somewhat laborious for writing computer 4... 0 • . • OallilitU 0 0 ^0 0 0 programs, for example. 1:1 First downstroke The upstroke The two side Curl round Make a tail from To avoid timing problems when keys are pressed together, the of theV of the K of the W for C the central° Microwriter works on a key accumulation principle, and the character is only entered when all the keys have been released. 0 Hence, you can start to press keys in any order, so long as at 00-1Q 0 least one of them is being held down at any given time. When all Everything Zig zag between Full MP the keys are eventually released, the result is as if all the keys Xcept your index the keys I or Z come too point Hyphen Com ma that were depressed in that sequence, irrespective of their Com mand Key 0 0 0 chronological order, were pressed simultaneously. This makes Pats of letters have been the keyboard action very 'forgiving', and allows characters to be 0 0 highloghted by outlining entered very slowly and deliberately when required. The speed Apostrophe which can be obtained after only a few weeks' use is very high — 84228 -1 (11/83) © Copyright Microwriter Ltd 1982 07-022 not as fast as touch typing, but certainly up to twice as fast as handwriting. Fig. 1. So metimes corny, but inevitably me morable

Practical Electronics February 1985 conserve battery life. The batteries are rechargable types, and a also with software npackages such as Wordwise and similar. A suitable charger is provided with the machine. Up to 1600 version for the Spectrum is soon to be made available, and words, or typically 5 pages of A4 size, can be stored in the Microwriter are working on versions for other popular personal memory of the machine. (Much more if cassettes are used.) computers too. All this helps to bring the unique qualities of Microwriting to the private individual, schools, colleges, etc.

THE HARD WARE APPLICATIONS — WHO USES ITT The packaging of the Microwriter inspires confidence! It is The most obvious market for the Microwriter is with housed in a very solid injection moulded plastic case. The keys professionals on the move—salesmen, executives, engineers, and are ultra-low activating-force microswitches with moulded keys. anybody who does an amount of documentation, report writing, Their action is light but positive, and their positioning is letter writing, etc. On the train or 'plane they can write their ergonomically spot-on. Inside there is just one main p.c.b. meeting reports, or they can keep notes in the field or by their holding the RCA CDP1802A CMOS microprocessor, four work benches, and either print the results out so that they are HM6116 CMOS 2k Byte static RAMs, and a 2564 8k Byte legible to themselves and to their colleagues, or if necessary CMOS EPRO M, along with an 'intelligent' liquid crystal display dump them onto the office computer or word processor to be above it as a sub-assembly, and other assorted CMOS i.c.s. The tidied up before final printing. There's no duplication of effort, batteries are housed between the microswitches in the upper half the typists no longer having to work from handwritten notes. of the case. It's a well laid out and professionally built product. The small size, portability, and ease of use of the Microwriter With the Microwriter itself comes a good quality soft carrying are attractions which a QWERTY keyboard has never had. case, a battery charger, a cassette recorder connecting lead, Microwriting can never be as fast as good touch typing, so it will some 'crib cards' giving a quick reference to control codes, not be used to replace QWERTY keyboards in typing pools or characters, punctuation, etc., and two instruction manuals; a secretarial offices, but for thousands of unqualified typists it of- new user's guide, and a more complex systems manual for fers a refreshing alternative to the two-fingered struggle, so it setting up communications protocol and the like. The new user's should be of great interest to small businesses, the police, sales guide is effectively the main instruction manual for the machine, personnel (especially those working from home), budding and without doubt is the best manual that I have seen for a novelists, and even to the writers of magazine articles! For piece of consumer electronics. The cartoon characters used schools it has the advantage of allowing the connection of four might annoy some, but they will drive the points firmly home to Quinkeys to each BBC microcomputer, which immediately just about anybody, whatever age or ability. Other product shares out normally limited resources to many more children. If manufacturers would do well to study this manual and compare accepted for these applications, it can only help establish its high standards with their own! Microwriting as a world-wide standard in years to come. There is an optional television interface unit available for the Microwriter which I'm somewhat less happy with. It interfaces THE FUTURE OF MICRO WRITING to the RS232 port, and allows the display of text on a domestic Until recent months the promotion of the Microwriter was a television set or a composite video monitor. It is expensive very low-key process, although some rather more prominent (around the £100 mark) and gives very limited facilities. Writing advertising is now being seen. Over 7000 have been sold, which onto the screen as you enter text works reasonably well, but if can only be the very tip of the potential iceberg. I must express you just want to dump a letter, for example, onto the screen to reservations, however, about the approach that Microwriter are check its layout, the use of the Microwriter becomes somewhat making on the market place, which seems to be rather uncertain more contrived. It's very difficult to put a letter onto the screen and lacking in self-confidence. I first saw a Microwriter 'in the without the top of the letter scrolling off the screen as soon as flesh' in the latter part of 1983, when I had a demonstration and the bottom of the screen is reached. The unit that I tested also a loan from a distributor for a couple of weeks. I expressed a failed to get the ends of the lines correct when dumping onto the great interest when I returned the machine to him, and was screen; parts of words were left at the end of some lines, then the promised more information and a follow-up call shortly. I never whole word reappeared again on the next line. For the majority heard from him, or another distributor I contacted, ever again. of potential Microwriter users I would question the necessity for At the end of January 1984 I approached Microwriter them- the television interface unit—when you've got the hang of selves for information and a review sample to help prepare this Microwriting you probably don't need it. It seems to be more article. I also ordered two Quinkeys for my own use. I am suitable as a shared facility between several users, and generally writing this article in mid August; the review sample only arrived seems to be somewhat of an afterthought rather than an integral three weeks ago! The Quinkeys arrived in the middle of June, part of the Microwriter system. some 19 weeks after they were ordered, and only after telephone calls at the rate of once per fortnight for most of that period. I THE GUINKEY persevered —I wonder how many others did not? For many people, the cost of a Microwriter (£299 plus VAT), I hope that the future is very rosy for Microwriting. Amongst although low by office equipment standards, is too high for them friends and colleagues the Microwriter has created more interest to consider it as a personal purchase. However, they could con- than any other piece of equipment that I can remember. The sider investing in a `Quinkey'. This appears to be an ordinary concept of the Microwriter is a work of genius. The market is Microwriter at first glance, but lacks most of the connectors and potentially vast, the product works well, and the presentation is the display. In fact, it contains no electronics, just a set of superb. The price is a little high, but should not deter the microswitches and resistors which enables up to four of them, professional market, with the lower cost market being satisfied ingeniously, to plug into the analogue inputs of a BBC by the Quinkey. Let's just hope that Microwriter can improve on microcomputer. For just under £50 the full Quinkey package the delivery and planning side of it, put some more aggression provides good value, consisting of the the Quinkey itself, a into the marketing, and produce a commercial, not just a manual, some crib cards, a connecting lead, and the software to technical winner. What a great shame it would be if the run the system. Further Quinkeys on their own cost around £30. Microwriter concept was lost to an overseas supplier, as has The software enables the Quinkey to be used as well as the happened to so many other viable products from the UK. standard BBC QWERTY keyboard, not only with software More information can be obtained from Microwriter Ltd., 31 within the BBC micro such as BASIC, the Acorn DFS, etc., but Southampton Row, London WCIB 5HJ. (01-831 6801).

24 Practical Electronics February 1985 THE LEADING EDGE

DIGITISATION The best example of this is what happens Exactly the same situation exists in at the Economist magazine. This London- magnetic tape factories, where any dirt in Everyone talks about the information ex- based publication also prints in America the atmosphere will end up as non- plosion. The key is digitisation. With digital and the Far East. Printing master plates are magnetic blemishes in the coating and telephone systems what goes down the line sent by airline courier to the Orient. Until a cause dropout. is a series of PCM pulses, rather than year ago they were also sent to America. Air in the so-called "clean areas" is analogue waves. Once you have that situa- The plum job on the EcononlIst was to filtered to Class 100, that is to say less than tion, the sky's the limit. take a day trip on Concorde to New York 100 particles of less than 0-5 micron size in PCM pulses can carry telephone quality and back, with the print plates, for safe every cubic foot of air. The pressure of air speech, high quality stereo radio, TV pic- keeping. Now the magazine text is con- inside these clean areas is higher than the tures, computer data, teletext, viewdata; in verted to digital data and sent by satellite atmosphere outside, so when a door opens fact any information that can be converted direct to a Connecticut printing works, clean air blows out and dirty air leaks in. into an electrical signal. Switching is by which publishes virtually simultaneously The staff must wear full length lint-free microchip, instead of the primitive with London. jump suits, like space clothing, and only a Strowger electro-mechanical relay which Wisely the Economist still sends a back few visitors are allowed in. Usually there is phone systems have used for the best part up text by 'plane just in case the satellite an air shower, where blasts of clean air of a hundred years. link breaks down. But no-one gets the plum flush dirt, dust, dead skin and dandruff off By interleaving different calls in the same job of going along with them any more. every human passing through. data stream, the capacity of a link goes up If only, I think every time I visit one of around 15 times, i.e. a pair of copper wires VIDEO NEWS these plants, factories which press ordinary that normally carry one analogue telephone records would take even remotely com- call, can carry fifteen digitals. With optical Polaroid has joined Kodak in 8mm video. parable steps to preserve cleanliness. The fibres, and the signals carried as light Sony may follow next year but so far official answer is that it's not necessary. pulses rather than electrons, capacity rises everyone else is sticking with their existing Certainly, by comparison, the technology much, much higher. VHS and Beta formats. Ironically by joining of LP production looks like a blunt instru- The British Post Office started working Kodak, Polaroid may well have helped its ment. But it is easy to forget that a vinyl LP on PCM phone links 20 years ago. Few rival succeed. The extra name gives the record is by far the most precise product people know that the PO installed an ex- new format credibility. mass produced from plastics! perimental digital exchange at Earl's Court At the Chicago Consumer Electronics The groove of an LP record is specified in 1968 and had it running until 1975. That Show both companies were demonstrating by IEC standard to be never less than 25 was when talk about System X started. NTSC camcorders using the 8mm cassette. microns (or millionths of a metre) wide and Cynics say that the System was called X Picture quality was good and sound, using preferably not less than 35 microns wide. because no-one really knew what it was f.m. mono, seemed OK. The big question As a "yardstick" a human hair is around 50 going to do or how it was going to do it. mark is over tape supply. microns in width. The IEC puts stylus tip Essentially it's a computer switching ser- Video writing speed is very low; 3.8 radius at between 15 and 18 microns. vice for PCM streams and there are now six metres a second for NTSC and 3.1 metres a Now let's look at a Laservision videodisc, System X exchanges working in London. second for PAL and SECAM. So packing and a compact disc digital audio record. One is at Baynard House in the City of density must be very high. You can get it Both have a spiral of information pits with a London. The first five were prototypes. either from tape coated with metal powder track pitch of 1-6 microns. Once data streams are digitally switched IMP) and coercivity around 1600 oersted. For videodisc the pits are 0-5 microns and connected, the options available open But this needs video heads which are ex- wide, and for compact disc they are 0-6 up wide. There is no problem in providing pensive and may be short lived. The other microns wide. Video pit depth is 0-1 micron conference calls, automatically re-directing way is to use lower coercivity tape coated and CD depth 0-12 microns. calls to other numbers or displaying the by evaporation of cobalt-ferric metal in a In other words there is very little dif- telephone number of origin when you vacuum (ME). No one has yet succeeded in ference in the dimensions; both are at least receive a call. making ME tape reliably in bulk. 50 times smaller than the LP groove. The Kodak started shipping 8mm camcorders laser spot for videodisc playback is ELECTRONIC MAIL to US traders last September. A 90 minute focused to a circle of 0-9 micron diameter cassette costs $24 and the system $2000. and for compact disc it is 1 micron. The Already many people in Britain are using There is no sign yet of a PAL or SECA M layer of protective lacquer in a compact electronic mail, which is a hybrid system of prototype. Although 8mm video almost cer- disc has to be exactly 1-2 millimetres thick, sending digital data down an analogue tainly comes too late and too expensive to or it will affect the laser focus. telephone line. I'm one of them and there catch the domestic market, it could well are quite a few stories to tell about how the form the basis of a new professional cam- system works in practice, as opposed to corder format. PARTY TURN theory Sony has both domestic and pro in- If you collect useless information to bring More of that in a future month. At the terests. Kodak and Polaroid are paying out of the bag at boring cocktail parties, moment I am trying to find out why the Matsushita, Toshiba and TDK to get the here's one for the bag. A CD player rotates main computer used by Telecom Gold for technology right for domestic use. the disc at a speed which varies between electronic mail keeps going wrong and Professional use is the logical follow on. 3-5 revolutions a second and 8 revolutions leaving users like me stranded! a second, to give a constant tracking Why worry about information CLEAN CUT velocity of 1-25 metres a second. technology? There's a very short answer. It That means that for a one hour disc there is always far cheaper to send electronic I have now seen inside several compact are 4-5 kilometres of track on a single side. data down a telephone line, or over a disc and videodisc manufacturing plants in For a laser videodisc the track length is 31 wireless link, than shift people or bits of Britain, Germany and Japan. They all have kilometres! paper from town to town or country to one thing in com mon with a microchip country. factory, that is absolute cleanliness. BARRY FOX

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* Strictly cash with order or credit card (Access or VISA) for out of stock items. only. * All items carry full manufacturers warranty _ ech HI-TECH COMPONENTS, * Delivery is normally from stock but please allow up * A V.A.T. receipt will be supplied with all orders. to 28 days. * Prices quoted are correct at the time of going to * Any query or complaint regarding an order should press but we reserve the right to effect changes be made in writing within 7 days of receipt of the without prior notice. order. No telephone queries will be entertained.

74HC251N 1.03 741522 0.17 4033 2.40 4078 0.25 6502 8086 M E M ORIES - EPR O M 75173N 1.44 F.D. CONTR OLLERS FAIRCHILD • 741C253N 1.03 7415221 0.62 4034 1.00 4081 0.23 FA MILY FA MILY 7517745 2.82 72 . FAST 2532-30Ons . 4.95 1.96 74HC257N 1.03 7415240 1.40 4035 0.54 4082 0.25 6502 ' so 8086 29.50 2532-450ns • 75182 0.50 10177W 30 .00 741001C 0.60 74HC266N 0.92 7415241 0.48 4040 0.41 4085 0.66 101791 15 .50 6502A 4.95 8088-2 22.50 2564-300ns 6.95 75183 0.50 741041C 0.60 74HC273N 2.24 7415242 1.36 4041 0.36 4086 0.40 101791-02 11 .00 6520 2.25 8216 0.75 2708-450ns 3.95 75188 741081C 0.65 74HC27N 0.80 7415243 1.36 4042 0.40 4093 0.23 75189 0.86 6520A 2.45 8237A-5 23.50 2716-450ns 35° 0.86 101793 18 .40 741109PC 0.65 74HC280N 3.26 74L5244 1.40 4043 041 4099 0.50 6522 3.40 8251A 7.50 2„7,16,-3„ ",11- 7.95„ r 75451 BP 0.22 101793-02 11.00 74111 PC 0.52 74HC32 0.40 7415245 1.95 4044 0.43 4502 0.55 6522A • 4.45 8253-5 7.50 4 ' .4"..-'n, 4 ." 7545281 0.29 101795 25 .00 7411381C 0.52 74HC373N 2.40 7415248 0.39 4045 2.00 4507 0.47 2732-450ns 4.45 101797 21 .00 6532 5.45 8255A-5 7.00 754538 p 0.22 7411 381C 1.26 74HC374N 2.40 7415249 1.16 4046 0.55 4508 0.96 2764-200ns 7.95 W01691 14 .00 6532A 5.95 8259A 6.60 75454BP 0.22 741139PC 1.26 74HC393N 1.78 7415251 0.78 4047 0.50 4510 0.45 WD2143 12 .00 6551 5.95 8272 35.00 2„,764,; 2„50n, 5.15 75468N 0.88 741151 1.26 74HC4002 0.64 7415253 0.25 4048 0.40 4511 0.50 82844 9.50 z I o,,,,,,Ons 4.75 75491N 0.31 . 741153 1.26 74HC4017 1.16 7415257 0.78 4049 0.50 4512 0.40 D ATA CON VERTERS 80086 46.65 27 C64-250n s 10.95 75492N 0.41 741157 1.30 74HC4020 1.46 7415258 0.27 4050 0.29 4514 1.00 80088 46.65 27 C64-30 Ons 10.45,n nn AY-3-1015 3.50 ZN425E-8 741158 1.17 74HC4024 1.20 7415259 0.42 4051 0.40 4515 1.84 6800 82 0 2 15.68 27128-250ns '' ." 2N4251-8 3.76 AY-3-1270 9.40 8.00 741161 2.34 74HC4040 1.46 741526 0.30 4052 0.48 4516 0.45 FA MILY 82c54 19.04 27128-300ns 16.00 AY-3-8910 6.40 ZN426E-8 1.90 74f164 . 1.68 74HC4060 1.46 7415261 2.60 4053 0.50 4518 0.40 , rr 82C55A212.98 AY-5-3600 8.84 ZN427E-8 6.68 741175 1.82 74HC4075 0.64 7413266 0.19 4054 1.30 4519 0.25 M E M ORIES RA M r68„9,9, 4,.,',.? 82C59A 15.22 0P8304 4.50 ZN4271-8 12.50 741181 3.90 74HC42N 0.90 741527 0.17 4055 0.72 4520 0.64 '°,'„,'-'4„ t.,'„. 82c82 6.26 4116- 150ns 1.28 1203 0.99 2N428E-8 5.10 741189 5.10 74HC4511 2.51 7415273 1.35 4060 0.50 4521 1.32 ,"`‘ ',..„',- "/4• 82C84A 8.94 4116-200ns 1.20 11398 180 ZN42131-8 9.70 741190 3.20 744-1(4514 3.76 7415279 0.77 4063 0.60 4522 0.84 "' " `'." 82C88 16.80 4164-150ns 4.45 LM301AN 0.30 ZN429E-8 1.60 741191 3.20 74HC4538 2.36 741528 0.17 4066 0.50 4526 0.52 6809P 6.25 4416-200ns 4.70 LM308AN 0.94 ZN432C1-10 20.79 741194 1.68 74HC4543 3.04 7415283 1,00 4068 0.16 4527 0.52 6810 1.70 4532-2000s 245 LM308N 0.56 ZN432E-10 13.00 741201C 0.52 74HC51N 0.64 7415290 0.29 4069 0.23 4528 048 6821 1.70 283 4564-15Ons 4.45 LM311N 0.60 ZN4330-10 25,00 741240 3.16 74HC533N 240 7415293 0.29 4070 0.23 4532 0.68 6840 3.70 FA MILY 8118-100ns 1.95 LM317MT 0.80 2N434 0.98 741241 2.42 74HC534N 2.40 741530 0.17 4071 0.23 4541 0.82 ‘884.,.„5 ,845 280ACPU 1.99 81256-15Ons 25.00 .LM3177 1.06 ZN435 4.38 741 24 3 2.80 74HC589N 1.72 741532 0.25 4072 0.23 4543 0.60 """ 1.70 280ACTC 1.99 8416-200ns 600 LM319N 3.30 ZN436E 1.26 741244 2.96 74HC58N 0.64 741533 0.17 4073 0.23 4553 2.00 6862 3.75 280ADMA7.95 8416-LP-200ns 6.40 1M324N 0.50 ZN440 55.00 741245 6.08 74HC595N 1.84 7415365 0.33 4075 0.46 4555 0.36 6875 4.95 280APIO 1.99 8417-200ns 6.00 LM3371 1.20 ZN441 46.80 741251 1.26 74HC597N 1.72 7415366 0.33 4076 0.48 4556 0.44 68E100 4.30 280A510-06. ,0 8417-LP-200ns 6.40 LM339 0.48 2N447 7.80 741 253 1.26 74HC73N 0.84 7415367 0.34 4077 0.23 4585 0.48 , ‘.68„.80, ,'n.1 .nr.." Z80AS10-17.95 LM339N 0.48 ZN448E 6.66 741257 1.26 74HC74N 0.84 7415368 0.36 - '' ''" 280AS10-27.95 M E M ORIES - RA M 1M348N 0.64 IN448.1 12.48 741258 1.34 74HC75N 0.92 741537 0.17 CRYST ALS 68821 330 280BCPU 5.95 LM3507 3.12 ZN449 2.72 741280 1.74 74HC76N 0.64 7415373 1.50 68840 6.60 * ZER O PO WER ZKXB A1118 1MHz 4.50 2808CTC 5.95 LM358N 0.60 ZNA1341 22.50 741283 1.74 74HC85N 2.02 7415374 0.52 68850 1.58 C M OS * A112A 1 008MHz 2.70 280BP10 5.95 LM3900 0.68 ZNA234E 9.40 74F32PC 0.52 74HC86N 0.80 7413375 0.26 A113A 1 8432MHz 3.50 88854 715 Z8OBS10019.95 MK482028-15Ons 32.00 LM393N 0.48 741352 1.26 7415377 0.46 74HCUO4N 0.80 All 6A 2.4576MHz 2N00 Z8OBS10-119.95 MK4820213-200ns 24.00 LM725CN 100 V OLTAGE REF . 741353 1.26 7415378 1.22 A1208 4MHz 1.25 Z808510-219.95 MK482028-250ns 23.00 741CP 0.16 74F373 3.16 TTL 7415379 1.50 A132A 6MHz 1.30 280510-3 6.00 LM747CN 0.60 ZN404 0.50 741374. • 3.16 - -741538 0' 25 7413: 00 0.11 ---, A140A 8MHz 1.25 zoosio-1 6.00 BIP OLAR PRO MS LM748CN 0.30 2N423 0 .98 741 379 1.83 7415386 0.50 741501 0 .17 A169A 3 6864MHz 2.00 7415390 1.10 280510-2 6.00 TBP185030N 1.54 MC 1413 P 0.80 ZN 458 0 .92 741381 6 .62 741502 0.17 A173A 9 8304MHz 2.75 MC1416 0.80 ZN458A 0.92 741382 4.22 7415393 052 TBP185A030 1. 38 74 .1503 0.17 A182A 19 6608MHz 2.50 MC14411 10.10 7144588 1.12 741398 116 6805 FA MILY TBP24S1ON 2.06 741504 0.25 741540 0..25 T8P24541N 8.88 MC14412 14.20 ZNREF 025 1.90 741399 2.70 741542 0 .25 MC1468052P 17.60 741505 0.25 DIL SKTS TIN MC1458CPI 0.35 ZNREF 040 1.90 741 52 1 2.76 741347 0.30 MC 14 68 18P 7.20 TBP24581N 5.50 741508 0.17 3.16 741348 0.35 1 + 100 + MC146823P 8.80 TBP24SA1ON 1.40 M C14951 6.30 ZNREF 050 1.90 741533 741509 0.25 TBP24SA41N 4.40 MC1496P 0.70 ZNREF 062 1.90 741534 3.16 74LS49 0.34 07070802 8 PIN 0.07 0.05 MC68705K13 755J0 741510 0.17 MC 1723 P • 0.40 ZNREF 100 3.05 741537 6.02 741551 0.17 07071402 14 PIN 009 0.07 MC68705831 40 .00 TBP28122N 3.10 74/538 4.38 /415109 0.27 741554 0.12 7 21 0 MC68705 U 31 36 .00 TBP28LA22N 4.14 MC 3242 A 6.30 0 0 6 2 16 PIN 0.09 ara TBP285166N 1900. MC 3302 P 0 .48 BUFFERS 741538 4'38 7415112 0..5417 741555 0.17 07071802 18 PIN 0 .15 0.10 2.30 07072002 20 PIN 0.19 0.14 74164PC 0.52 7415113 027 7415670 68000 FA MILY 1BP28542N 4.50.50 MC3340P 2.36 811596 0 .80 74F74PC 0 .58 ,„ „„ 1BP28546N 4 MC 3357 P 1.90 * 747313 0.30 07072202 22 PIN 0.2 1 0.15 811597 0.80 74F86PC 0.77 7415114 o0.44 MC68000010 .,t" T8P28586N 5.00 MC3423P1 0.81 741574 0.35 07072402 24 PIN 0.24 0.16 741512 0 '25 MC6800018 `.' 5°." TBP28SA42N 4.50 MC 3441AP 2.90 811598 0.80 741375 0.28 07072802 28 PIN 0.26 0.17 7415122 MC3446AP 2.90 8126A 0.80 0 '42 07074002 40 PIN 0.29 0.18 MC6800818 45330 TBP28SA46N 4.50 HIGH 741576 0.17 MC3447P 4.30 8128 0.80 7415123 0 '53 MC6823018 r1,9....50n TBP28SA86N 8.82 74L578 0.19 8128A 0.80 SPEED 7415124 2.30 r„.. SKTS G OLD MC6845118 .'.". AM27513PVC 3.74 MC3448A 3.99 741583 0.28 DIL UVLU 8T95 CMOS 7415125 0.49 71558685 MC68901P 75 .00 AM27519PC 1.92 MC3470P 6A4 olio 8197A 0.80 7415126 0.29 AM275191 DC 15.00 MC3480 7.76 0..4392 0626 014802 148 PIN 0.16 8798 . 0.80 74HCOON 10.42 741513 0.17 TI 9900 FA MILY AM275250C 15 .00 MC3487 1.80 741390 0.21 06061602 16 PIN 0.210.20 741591 1.30 06061802 18 PIN TM59901- 95 4.50 AM275290C 6.46 NE 555P 0.25 74HCO3N74HCO2N 0.640.42 74151367415132 0.460.73 741592 0.22 06062002-20 PIN 0.22 TM59902 4.50 AM275350C 22.00 NE 556 CP " 5 OPT OISOLAT ORS - 74HC04N 0.44 7413138 0.77 0.28 741593 0.21 1M59918 ., 35.00 8032513-1 9.40 4N25 0.75 74HCO8N 0.42 7415139 0.77 06062202 22 PIN 0.32 803251 3-U 9.40 741595 1M59927 11.60 0.77 06062402 24 PIN 0.42 M E M ORIES E2 PRO M 11010-CP 0.44 4N26 ' 0.75 74HC107N 0.78 741514 0.28 1M59928 13.00 06062802 28 PIN 0.46 4 33 74HC109N 0.50 7415145 1.23 crops 1M 59929 13 .00 X2804AP-300ns 14.95 TL061-CLP 0.28 N 0.90 74HC1ON 0.64 7415148 1.50 06064002 40 PIN 0.66 1M59937 8.70 X2804AP-350ns 13.45 11062-CP 0.47 UHF M O DULATORS 74HC112N 0.86 741515 0.25 4000 Series 1M59980 17 .20 X2804A1-450ns 12.75 1.1064-CN 0-55 DIL SKTS W/ WR AP 2. 74HC113N 0.86 7415151 0.36 4000 0.16 1M 59995 13 .70 X2816AP-300ns 29.95 11066-CP 0.28 UM1111 95 74HC132N 1.28 7415153 0.36 4001 0.15 TURNE D PIN 82816AP-350ns 25.00 11071-Cl 0.28 UM-1233 3.45 74HC137N 1.81 7413155 0.24 4002 0.16 X2816AP-450ns 22 50 1L072-CP 0.56 9090802 8 PIN 0.36 74HC138N 1.20 741315¢ 0.77 4006 0.55 1L074-CN 1'10 9091402 14 PIN a m VOLTAGE REG. 74HC139N 0.78 7415157 0.24 4007 0.16 9091602 16 PIN 0.86 LINE AR/INT. DEV. 11081-CP 0.29 74HC151N 1.16 7415158 0.62 4008 1L082-CP 0.49 7805 0 .75 0.50 9091802 18 PIN 0.96 74HC153N 0.90 7413160 0.80 4009 4702 8.90 11084-CN 1.02 7812 0.75 0.25 9092002 20 PIN 1.08 HCI-55564-5 10.66 1L091-CP 0.39 7815 0,75 74 HC 157 N 1.02 7413161 0.34 4010 0.25 9092202 22 PIN 1.18 74HC15814 1.02 7415162 0.80 4011 (Speech Synthes,$) 1L092-CP 0.72 78H05SC , 7.50 015 9092402 24 PIN 1.28 74HC160N 0.90 7415163 0.804012 0.16 AM79100C 34 •88 11094-CN 1.30 78H12A5C 8.95 9092802 28 PIN 1.50 741-tC161N 0.90 7413164 1.10 4013 015 AM7911 DC 34.88 1L487-CP 0.59 78HGASC 9.95 9094002 40 PIN 1.70 0.40 251525181 C 3.60 TL489-CP 0.59 78105 0.30 74HC162N 1.51 7415165 0.61 4014 25152521PC 3.28 78112 0.30 74HC163N 1.51 7415166 1.95 4015 0.50 TL494-CN 1.99 ZIF SOCKETS 25152538 PC 232 71496-CP 0.59 78115 0.30 74HC164N 0.95 7415173 0.63 4016 0.29 25132539PC 1L507-CP 1.22 78540DM 7.50 74HC165N 2.24 7415174 1.30 4017 0.40 08082402 24 PIN 5.70 261531PC 2.62 78540PC 3.00 74HC173N 1.35 7415175 0.96 4018 0.40 08082802 28 PIN 6.90 261532PC 2.22 7N450-E 6.08 74HC174N 0.80 7413181 2.09 4019 0.30 08084002 40 PIN 8.25 Hi-Tech 2 62 7905 0.95 . ZN451-E 740 7912 , 0.95 74HC175N 0.78 7415190 0.98 4020 0.41 6402 6.40 ZN451-KIT 29.95 components 751078N 0.69 7915 0.95 74HC194N 1.28 7415191 0.75 4021 0.56 75110AN 0.86 LM309K 0.55 74 HC 195N 1.28 74 15 192 0.36 4022 0.42 75150P 0.86 1M317K 7.45 74HC20N 0.40 7415193 1.10 4023 0.23 75154N 1.05 LN323K 4.95 741- K237 N 1.80 7415194 0 .28 4024 0 .40 r i l l 75159 2.30 1M338K 4so 74HC240N 1.38 7415195 0.78 4025 0.16 . a ll a 75160AN 2.60 74HC241N 1.34 7415196 1.10 4026 0.74 75161AN 2.82 74HC242N 2.24 7415197 1.10 4027 0.52 75162AN 4.08 74HC243N 2.24 741520 0.17 4028 0.34 0379 4131 75172N0 1.96 74HC244N 1.32 74L521 0.17 4031 0.93

26 Practical Electronics February 1985 PART NO. DESCRIPTION MAIL ORDER BBC MICROS AND ACCESSORIES PRICE

ANB01 BBC Model B Micro E325.00 £385.00 ANB02 BBC Model B Micro with Econet I/F ANB03 BBC Model B Micro with Disc I/F £406.00 £445.00 ANB04 BBC Model B Micro with Disc & Econet £17.91 ANB21 DNFS ROM ANB23 Disc Interface Kit (fad DNFS R061) £84.00 ANB14 Speech Interface £40.00 ANK01 1EEE488 Interface Adaptor E283.00 ANB22 Econet I/F Kits £35.00 BBC 45 2 BBC Joysticks E8.00 corn ponents £7.50 GILRAY ROAD, DISS, NORFOLK. TEL: 0379 4131 STAND Monitor Stand SRE1 Sideways ROM Expansion Board for BBC Micro E25.95

BBC DISC DRIVES

HC1 Single 100k 40 track single sided £75.00 HC15 Single 100k (expandable to dual) 40 track E90.00 HC1D Dual (2 x 100k) 40 track single sided E160.00 E156.50 INSULATION DISPLACEMENT CABLE ASSEMBLIES DIP JUMPERS BBC44 Single 400k 80 track double sided 1313C445 Single 400k (expandable to dual) 40/80 track switchable CONNECTOR SYSTEM double sided E180.00 ' IDC JUMPERS Single Ended HEADERS OPEN - - 24 cable BBC44SW Single 400k 40/80 track switchable double sided £159.00 Dual (2 x 400k) 40/80 track switchable double sided E310.00 SHROUDED OPEN STRAIGHT SINGLE ENDED 14 pin 1.73 BBC44D 16 pin 1.90 90' 90* PINS 36" cable IDC socket 24 pin 2.73 10 way 086 0.65 0.47 10 way 1.72 40 pin 3.96 14 way 1.22 0.83 0.59 14 way 2.07 MECHANISMS 16 way 1 34 0.92 0.65 16 way 2.22 Double Ended 20 way 1 36 1.13 0.77 20 way 3.14 6' cable 12"cable 18'cable E70.00 26 way 1 70 1.40 0.95 26 way 3.75 100k single sided Alps 14 2.74 2.84 2.94 E140.00 34 way 204 1.78 1.19 34 way 3.98 400k double sided Epson 16 3.03 3.14 3.25 40 way 2.28 2.07 1.37 40 way 4.23 24 4.18 4.36 4.55 SO way 270 2.54 1.67 50 way 5.36 60 way 3.20 3.02 1.96 60 way 6.36 40 5.89 6.18 6.47 FLOPPY DISCS

SOCKETS DIP PLUGS D-TYPE DISC DRIVE CONNECTING CABLES MD-1C/B Nashua single sided, single density 40 track (10 discs) E12.00 34 way card edge to 34 way card edge 1M 11.30 10 way 0.88 14 way 0.92 PLUGS MD-1DC/B Nashua single sided, double density 40 track (10 discs) £13.00 18.00 34 way card edge to 2 x 34 way card edge 1 5M Nashua double sided, double density 40 track 110 discs) E15. 50 14 way 1.06 16 way 1.06 9 way 1.38 MD-20C/B 34 way card edge to 34 way IDC SKT (BBC) 1M 8.50 E17.85 16way 1.16 24 way 1.60 15 way 1.85 MD-2FC/B Nashua double sided, quad density 80 track 110 discs) 34 way card edge to 2 x 34 way IDC KT (BBC) 1 5M 14.50 20 way 1.38 40 way 2.40 25 way 2.52 BBC Power Cable - Single Drive 3.50 26 way 1.66 37 way 3.34 BBC Power Cable - Dual Drive 4.75 34 way 1.94 TRANS. SPECIAL OFFER 40 way 2.08 CONNS. RIBBON CABLE (PRICED PER FOOT) BBC MICRO 50 Way 2.78 BASF double sided, double density 40 track (10 discs) E14.00 10 way 0.86 GREY RAINBO W BBC40TD 60 way 3.34 CONNECTORS 16 way 1.17 9 0.16 0.25 20 way 1.37 10 0.16 0.25 DIN PLUG 7 PIN 0.40 26 way 1.67 DIN PLUG 6 PIN 0.40 DISC STORAGE BOXES CARD 14 0.21 0.35 34 way 1.87 15 0.22 0.37 DIN PLUG 5 PIN 180' 0.40 EDGE 40 way 2.23 16 0.23 0.39 DIN PLUG 5 PIN DOMINOE 0,40 MDT25/3 33" Flip 'N' file Micro disc box (cap 25) E7.75 £18.77 10 way 1.84 20 0.28 0.48 POWER PLUG (36' CABLE) 3.00 DT25/5 5;" Flip 'N' file lockable disc box (cap 25) D-TYPE £10.65 20 way 3.14 25 0.34 0.60 ANALOGUE INPUT PLUG 2.25 DT60/5 Si" Standard lockable disc box (cap. 601 SOCKETS SWAY DIN SKT 180' 0.90 26 way 3.80 26 0.35 0.62 34 way 4.90 9 way 1.47 34 0.45 0.80 SWAY DIN SKT DOMINOE 0.90 6 WAY DIN SKT 0.90 MONITORS 40 way 5.52 15 way 2.02 ao 0.52 0.92 7 WAY DIN SKT 0.90 50 way 6.68 25 way 2.90 50 0.64 1:14 15 WAY DIN SKT 2.15 60 way 8.06 37 way 3.97 60 0.76 1.35 W ON 9 inch green screen high resolution NEC high quality monitor E125.00 12AMDN 12 inch green screen high resolution NEC high quality monitor £1 35.00 Connecting cables for personal computers 1431 Microvitec 14" RGB colour mohitor E175.00 A comprehensive range of high quaky interconnecting cables for popular micro computers. All cables 1441 Microvitec 14' RGB colour monitor high resolution £410.00 utilise high quality connectors and are individually tested to ensure trouble free use. 1451 Microvitec 14' RGB colour monitor medium resolution £295.00 1431/AP/MS Microvitec 1431 PAL & RGB inputs and sound facility £225.00 Part number Description Computer Video cables CON100 Phono plug to phono plug (2M) 1.20 EPSON COMPUTERS AND ACCESSORIES CON101 Phono plug to BNC plug (2M) 2.95 C0N102 BNC plug to BNC plug (2M) 3.95 PX-8 Epson portable computer (incl. CP/M and s/w) 64k E798.00 C0N107 6 pin DIN to open end (1M) . BBC 1.05 PX-8/120 120k RAM E998.00 CON108 6 pin DIN to 6 pin DIN (1M) BBC 1.50 CX-21 Acoustic coupler £160.00 CON119 Phono plug to coax plug 1.35 P1/10 Disc drive for PX-8 £360.00 C05160 DIN plug to 2 phono plugs Dragon 1.20 P40 Thermal printer for PX-8 and 604-20 E86.91 HX-20 Epson portable computer £411.00 Cassette recorder cables

(ON log 7 pin DIN to open end . BBC 1.25 MATRIX PRINTERS CON110 7 pin DIN to 2 x 3.5mm + 1 ix 2.5mm 1/plug BBC 2.50 7 pin DIN to 5 pin DIN + 2.5mm 1/plug BBC 2.50 CON111 RX80 Epson RX80 100cps matrix printer E204.00 Spin DIN to 2 x 3.5mm I/plugs Spectrum/ZX 2.50 CON118 RX8OF /7 Epson RX80F/T 100 cps matrix printer friction or tractor feed E231.00 Spin DIN 10.2 x 3.5mm + 1 x 2.5mm 1/plug Dragon 2.50 CON117 FX80 Epson FX80 150cps matrix printer • E328.50 MT8OSP Mannesmann Tally MT80 matrix printer friction or tractor feed Parallel printer cables with film ribbon and tear off facility E217.00

CON130 36 way plug 10 36 way plug (2M) Sinus/Apricot 18.00 CON131 36 way plug to 36 way plug (5M) Sirius/Apricot 26.50 LETTER QUALITY PRINTERS CON132 36 way plug to 36 way socket (2M) 18.00 26.50 (0N1 33 36 way plug to 36 way socket (5M) HRS 8-other HRS Thermal printer A/C mains or battery E130.00 IBM/TI PC 19.00 CON144 36 way plug to 25 way male D type (2M) HR15 Brother HR15 Daisy wheel printer (13cps) E326.00 IBM/TI PC 27.50 CON145 36 way plug to 25 way male D type (5M) 111225 Brother HR25 Daisy wheel printer (23cps) E550.00 RML/Apple 19.00 (051 34 36 way plug to 25 way male D type (2M) UCH IDA Uchida DWX305 Daisy wheel printer (20cps) E227.00 CON135 36 way plug to 25 way Male D type (5M) RML/Apple 27.50 Dragon 13.95 CON142 36 way plug to 20 way IDC socket (2M) PRINTER SUPPLIES CON139 36 way plug to 26 way IDC socket (2M) BBC 9.95 BBC 22.95 • CON140 36 way plug to 26 way IDC socket (5M) 11241P160 11 x9; 1 part plain listing paper (2,000) [12.56 TRS80 Lev 1 18.50 CON141 36 way plug to 34 way card edge (2M) 11241P2CI 11 x9; 2 part (otc) plain listing paper (1,000) E15.93 TRS80 Lev 2/ CON143 36 way plug to 34 way IDC socket (21.41 11241P3CI 11 x9; 3 part (otc) plain listing paper (700) E17.86 Memotech 10.95 11370R160 11 x14', 1 part ruled listing paper (2,000) £1 6.20 11370R2NC 11 x14; 2 part (ncr) ruled listing paper (1.000) E22.50 RS232 Cables 11370R2CI 11 x 14; 2 part (otc) ruled listing paper (1,000) E15.00 5.85 12235P1605 12 x9; 1 part plain listing paper with side perfs (2,000) E12.00 i C0N106 25 way male D type to 5 pm' DIN BBC E2.20 CON128 'Universal' R5232 cable (pins 1-8, 20 connected HRtR Brother HR1 ribbon and 20 jumpered as required) 2M 15.95 RIB119 Diablo Hytype II Multistrike film ribbon £1.75 CON I 64 'Universal' R5232 cable as above but 5M 20.95 GP205 Diablo Hytype II fabric ribbon E2.50 E3.00 C06120 25 way male to male 1-25 connected (2M) 16.95 MX80 Epson MX80, RX80, FX80, fabric ribbon E6.50 CON121 25 way male to male 1-25 connected (5M) 22.50 MT80 Mannesmann Tally MT80 film ribbon C0N122 25 way male to male 1-25 connected (10M) 32.50 R113117 Uchida DWX305 multistrike film ribbon E2.75 C05123 25 way male to male 1-25 connected (30M) 68.00 HR5R Brother HR5 ribbon E2.20 E4.00 C0N124 25 way male to female 1-25 connected (2M) 15.45 HR15R Brother HR15 multistrike ribbon E4.00 (ON125 25 way male to female 1-25 connected (5M) 21.00 HR25R Brother HR25 multistrike ribbon (05126 25 way male to female 1-25 connected (10M) 31.00 Brother daisy wheels E14.00 CON127 25 way male to female 1-25 connected (30M) 66.50 Uchida/Qume daisywheels E4.00 C05129 25 way male t09 way male Spectrum 15.95 LAB089361C 3(x1 7/16 Labels - 1 wide ( 8,000) E20.00 (05162 25 way male to 9 way male Mackintosh 15.95 LA80893615 3; 1 7/16 Labels - 1 wide (2,000) E13.00 C06163 25 way male to 5 pin DIN • RML 480Z - 14.95 LA8070363F 211 7/16 Labels - 3 wide (1/10") (2,000) E8.00

27 Practical Electronics February 1985 TOM WilhosICEng

POWER OP-AMPS (TCA365 and TCA2365)

nN E of the most important components The 1 ohm resistor does not have to be high STABILITY available to the analogue circuit designer power (+ watt will do) and the capacitor mug There are many factors influencing stability is the operational amplifier, or 'op-amp'. The be 100nF for the TCA365, or 220nF for the in operational amplifiers. These tend to be in- majority of these, however, are somewhat TCA2365. It is unimportant which way up the volved, complicated, steeped in complex-plane limited in their load driving capabilities. network is fitted; the capacitor can be connec- mathematics, and certainly beyond the scope Simple devices such as the 741 can only out- ted to OV and the resistor to the output, or vice of Semiconductor Circuits! Empirically, put 25mA under short circuit conditions, or versa. Both power op-amps can be used with most electronics engineers and enthusiasts 10mA in normal operation. For much higher either split or single rail supplies, just as would learn some straightforward rules of thumb currents it is usually necessary to add extra be possible with most conventional op-amps. about how to keep amplifiers stable and driving transistors to a conventional op-amp. Figs. 3a and 3c are very straightforward prevent problems of self-oscillation at The TCA365 and TCA2365 are power op conventional op-amp circuits, and apply per- several megahertz. A common 'cure-all' is to amps which allow the designer to use a single fectly well to the TCA365 and TCA2365. For connect a small value capacitor, typically less i.e. in high power applications rather than the minimum offsets, Rg in Fig. 3a and R, in Fig. than 100pF, between the output and the in- more cumbersome 'op-amp plus components' 3c should be included as shown, although in verting (—ye) input. Don't do this to a approach. In practice, they behave as fairly many circuits these are unnecessary and can TCA365 or 2365! Even if it doesn't actually ordinary op-amps with the exception that their be replaced by short circuits for economy. cause oscillation (which it probably will) it will output stages can drive up to 3 amps in the Both these circuits, however, should really certainly make oscillation much more likely. case of the TCA365, or 2-5 amps per only be used for higher gain circuits; +10dB This is basically due to the fact that the op- amplifier in the .case of the dual op-amp or more, or preferably +20dB. For lower gain amps have poor stability at low gains, and a TCA2365. The two i.c.s are very similar, with circuits, and certainly for anything less than capacitor across the feedback loop ensures both sets of specifications being given in 10dB (approximately x3), the configurations low gains at high frequencies. For gains of Fig. 2. The main points to watch are supply of Figs. 3b and 3d should be used. For unity more than 20dB (x 10 gain) the i.c.s are nor- voltage maxima, output currents, and power gain, use typically between 10k and 100k for mally quite stable, assuming that the Zobel dissipation; these all vary between the 365 and both 121 and Rf, with Ro approximately one network is fitted and that P.S.U. decoupling is the 2365. (Note that the output current shown tenth of that value, in Fig. 3h, and typically taken care of. More than 10dB (x3 gain) is for the TCA2365 is 2.5A per amplifier, not between 10k and 100k for R f in Fig. 3d, with normally acceptable, but below this there can for the whole i.c.) Fig. 1 shows the pinouts of Ro one tenth of that and Rg an open circuit. be problems with transient response the i.c.s. For moderate to high power applica- The reason for all this is concerned with tions, heatsinks should be used. These should stability. NON-INVERTING be insulated from the i.c.s' tabs if the internal INPUT connections to the —ye supply could cause INVERTING INPUT short circuits or problems. -YE SUPPLY

The TCA2365 has an 'inhibit' input which OUTPUT

can be used to turn the outputs of the op-amps •VE SUPPLY off, ie. high impedance (approximately 4k). In-

hibiting is effective when pin 6 is taken to the HEATSINK IS —ve supply rail, and the amplifiers operate TCA 365 INTERNALLY normally when pin 6 is taken above 3.0V CONNECTED TO PIN 3 referred to the —ye supply, or left unconnected. Both the TCA365 and the TCA2365 have extensive protection; they are d.c. short circuit proof and have thermal overload and safe f OUTPUT operating area protection. The internal current OP-AMP a INVERTING INPUT limiting makes them ideal for driving complex NON-INVERTING INPUT loads, and especially for driving filament -VE SUPPLY lamps, whose low resistance in the 'cold' state • VE SUPPLY can cause problems with other types of driver. INHIBIT INPUT f NON-INVERTING INPUT BASIC CIRCUITS OP -AMP b INVERTING INPUT Some basic circuits for use with these OUTPUT power op-amps is shown in Fig. 3. In all cases there is an external Zobel network (sometimes HEATSINK I INTERNALLY known as a Boucherot network) fitted between TCA 2365 CONNECTED PE 5314 the output and 0 volts to help to maintain TO PIN 4 4st stability under widely varying load conditions. Fig. 1. Pin outs for the TCA365 and TCA2365

28 Practical Electronics February 1985 TCA365 (Single Op-A mp) TCA2365 (Dual Op-Amp)

Minimum Maximum Minimum Maximum Characteristic Notes Value Typically Value Value Typically Value Units Supply voltage All spec's quoted at +15V for +4 +15 +18 +4 +10 +13 V 1CA365 and +10V for TCA2365 .(or 8V) *(0r36V) *(or 8V) .(or26V) In normal operation: 20 40 _ 30 50 mA Quiescent current with amps inhibited: - - 5 8 mA (TCA2365 only) Temperature range 0 +70 -25 +85 °C Maximum 0/P current Per amplifier 3.0 2.5 A Maximum I/P voltage (Differential) Supply rails Supply rails I/P offset voltage -10 +10 -10 +10 mV I/P offset current -0.2 +0.2 -0.1 +0.1 µA Temperature coefficient (Of input offset current) 0.1 nA/° C Input current 0.2 1.0 0.25 1.0 µA Input resistance At 1kHz 1.0 5 MO I Load resistance = 4700 at +13-0 +13.2 Output voltage V 1 Load resistance -= 4.70 1kHz +11.7 +12.0 +8.0 +8.5 Slew rate 4 4 V is Voltage gain Open loop, at 100Hz 90 70 80 dB I/P common mode +13.4 +13.5 +7-0 4-7.5 Load resistance = 4700 V voltage range -15.0 -15.0 -10 -10.5 Common mode Load resistance =4700 75 83 70 80 dB rejection ratio Supply voltage Gain = x100, frequency =20Hz 50 62 dB rejection ratio Gain = x 10, frequency =100Hz 70 80 Power dissipation Total for package, at 90°C 15.0 6.0 W Equivalent I/P noise Gain = x11, I/P resistor = 10k 3.0 µV Inhibit input For Lc. turned off - o 1.0 V (TCA2365 only) For i.c. turned on 3.0 (+ve V supply) *-- For single supply rail operation

Fig. 2. Specifications (note different supply rails used in measuring spec's.)

RI (overshoot of the output on square waves) and RI stability. Hence, the circuits of Figs. 3b and 3d should be used for low gain applications. Although the actual voltage gains of these circuits are exactly the same as the equivalent gains of Figs. 3a and 3c, the inclusion of Ro actually causes the op-amps to be working in a 'high gain' way. Normally, this is rather un- desirable, since there is no apparent benefit to the user and the amplifier has a much noisier output voltage, but in this application the 'pseudo gain' helps to ensure stability at low Rf real gains, and is to be recommended for use GAIN= GAIN = 4RF FOR OPTIMUM STABILITY. MAKE with any circuitry demanding a gain of less FOR MINIMUM OFFSET. MAKE than x4, or even less than x 10 to be on the Ro = R Rf R i PES6M 10 Inscm safe side. -9 - RI • RI

PO WER SUPPLIES ''P The capabilities of these op-amps to dump VE several amps from the supply rails into a load puts considerable strain on the P.S.U.s used. The best general guidance that can be given is to consider the devices as audio power amplifiers, and to use the, same constraints about removing earth loops, supply decoupling, keeping inputs away from outputs, etc. As with audio power amplifiers, the TC A365 and TCA2365 will overheat very rapidly when os- cillating at very high frequencies, so any de- bugging of stability problems should be done very rapidly, and for short periods only! RI' Ag GAIN = Specifically, it is good practice to take the OV Ag connection to the feedback resistor, input FOR - R FOR MINIMUM OFFSET. MAKE I OROPRT I M.g URM9 STABILITY, MAKE resistors, input decoupling, etc, as appropriate, Rf Rg IPES5m IPES71.4 Ro = R f to the power supply as a separate connection RI Rg 10 from the load, Zobel network, etc, to isolate Fig. 3c. Non-inverting, high gain Fig. 3d. Non-inverting, low gain the input as far as possible from the output. In all cases, each power op-amp should have Fig. 3. Basic power op-amp circuits

Practical Electronics February 1985 29 (ADJUST TO SUIT SENSOR I •vE SUPPLY amps into any suitable load. Output diodes should be added, as shown in the other circuits, if the load is to be an inductive one. 22k SENSOR PRESET Rh DIFFERE NTIAL DRIVIN G RELAY Finally, Fig. 6 shows two power op-amps driving a d.c. motor in a 'bridge', or differen- 8k 2 HYSTERESIS I ICA 365 I SETS 220k tial drive mode. This allows the direction of rotation of the motor to be changed. ICI and IC2 are arranged as comparators with RH and 1, OR ' 2 T0A2365 RL setting the threshold voltage VT, and are designed to be driven by logic signals A and B. in SENSOR If both inputs A and B are at a low level (logic

RELAY 0), both sides of the motor will be at a low

101. PRESET ) 100n 220n 2 level (OV). If both inputs are high (logic 1), IN 1.002 FOR FOR then both sides of the motor will be at a high PEStion TCA365 TCA 2365 level, near to the +ve supply rail. In both these OV cases the motor will not run, since there is no Fig. 4. Simple sensor detector and switch differential voltage across it—both terminals of the motor are at the same voltage. However, if one input is high, and the other 100µF capacitors between its supply rails and proportion to a required effect. For example, a low, the motor will run in one direction or the 0 volts, or simply across its rails in the case of light dependent resistor (e.g. 0RP12) or ther- other. Normally, VT should be set to a suitable single supply systems. mistor would allow the sensing of light level or level for the logic family which is used to con- When inductive loads are to be driven, temperature respectively. The sensor preset trol IC! and IC2; ideally, RH and RL should diodes should be connected between the op- scales the voltage range produced by the sen- be taken from the logic's power supplies, not amp output and the supply rails, as shown in sor at the op-amps non-inverting input, while the +ve power supply as shown, to ensure ac- Figs. 4, 6 and 8. This protects the op-amp's the threshold preset alters the level at which curacy of the threshold voltage. driver transistors from the huge back e.m.f. the op-amp changes state. Rh provides some The TCA365 and TCA2365 are ideal for spikes generated when inductive loads are sud- hysteresis to stop the op-amp 'hunting' or use in controlling motors, relays, magnetic denly turned off. 'chattering' when the sensed value is just on valves, and solenoids. They can also make a the threshold point. good basis for the design of regulated power APPLICATIONS A square wave oscillator is formed by the supplies. Their current limiting makes them es- The uses for these i.c.s fall mostly into the power op-amp in Fig. 5. The mark/space ratio pecially suitable for driving filament lamps realms of control and switching. They will potentiometer adjusts the charge and dis- and other unusual loads, and their op-amp amplify and drive audio signals, but not with charge paths for CT such that their sum is configuration makes for easy interfacing of the fidelity that can be achieved by audio always constant (i.e. the frequency does not these loads with both analogue and digital cir- power amplifiers specifically designed for the vary) but the mark/space ratio can be ad- cuitry. When stability is taken into considera- task. Essentially, these i.c.s are excellent for justed over a wide range. The frequency itself tion these are easy and effective to use, and use on many occasions when an ordinary op- is set by a combination of the value of CT and provide an economic solution to many power amp simply runs out of drive capability. Some the setting of the 100k 'frequency' poten- driving problems. Both i.c.s are available from examples of switching applications are shown tiometer. This circuit is capable, by virtue of Electrovalue, 28 St. Jude's Road, Englefield in Figs. 4, 5 and 6. the power op-amp, of driving pulses of several Green, Egham, Surrey. A simple sensor circuit is shown in Fig. 4 using the power op-amp as a comparator and directly driving relays I and 2. The sensor can be any device which varies in resistance in VE SUPPLY

1N 1.002

MARK/SPACE RATIO MOTOR

I/P A • • in

1N 1N 4002 4002 100n FOR TCA365 100n FOR TCA365 220n FOR TC.A2365 220n FOR TCA2365

I/PR

INPUTS

B A EFFECT ICI, 1C2 TCA365 OR 1/2 TCA 2365

220n 0 0 STOPPED FOR TCA 2365 0 1 RUN CLOCKWISE

1 0 RUN ANTICLOCKWISE EPE59.4 PE6OM 1 1 STOPPED

Fig. 5. Power pulse generator Fig. 6. Bi-directional motor control

30 Practical Electronics February 1983 MICR OPR OCESS OR CO NTR OLLED D C M OT O R D RIVE R S

I AST month we looked at a timer circuit L. triggered by a microprocessor. This month D2 we have another microprocessor based project, to allow the analogue driving of d.c. •Vp motors. Again, the circuit assumes the use of the Z80 microprocessor, although it is very • VE POWER INPUT easily adaptable for other devices. The cir- I .8V TO •20V1 cuitry is shown in Figs. 7 and 8 and the Vero- board layout in Fig. 9. The circuit consists of two separate sections; the decode, and the (POWER ON) OVp driver. Up to 8 drivers can be operated by one OV POWER common decoder. INPUT FROM The address decoding is done in a similar MICRO- {IORO ADO 11 way to last month's project. ICI compares the PROCESSOR CONTROL 12 NIC most significant nibble (4 bits) of the 8 bit port LINES WR TO PIN 14 1C5c address with the settings of S 1 to S4. Each IC5d OF IC5 • 5V SET I/0 switch is turned off to correspond to a logic I, ADDRESS, 82 R3 84 HIGH and on for a logic 0. The corriarison is only 3 81 NIBBLE 41,7 41,7 4k 7 enabled when both IORQ and WR are at logic A= B 4 k7 IN 0 (determined by IC5c), corresponding to the ri. 7 1 / A7 0. 83 83 microprocessor performing an I/O write in- I< struction. IC2 is a 3-to-8 line decoder used for A60 A2 1 Cl B2 74 LS85 the least significant nibble of the port address. 2 A50 Al B1 Address line A3 must be held at logic 0 and 10 9 the other 3 lines then provide the address of A40 AO BO _J the driver circuit required. The least significant A = B nibble of the driver address will therefore be 0 OUT OVL to 7, as determined by the latch output of IC2 FROM 6 used. The outputs of IC2 are inverted, and are MICRO- OVL PROCESSOR < wired to the LATCH inputs of any required ADDRESS BUS 85 driver circuits. Hence, if one particular driver 6 16 T +5V 561, circuit LATCH input was connected to E3 15 LATCH output 3 of IC2, switch S1 was off 00 A3 0 El 14 if and switches S2 to S4 were all on, that driver IC2 01 3 Lf 02 LATCH circuit would respond to address 13H (i.e. 19 TO IC6 A2 0 A2 12 if OUTPUTS FIN 6 in decimal). Driver circuits can thus be 0/P'S 11 if TO provided at port addresses 00H to 07H, 10H 2 0 4 DRIVER Al 0 Al 10 to 17H, 20H to 27H, 30 to 37H, etc. 05 CIRCUITS 741_5138 6 9 1S IC3, with associated components, provides -0 6 \ AO 0 • 7 a 5 volt regulated supply. This can be omitted 0 C5 if the microcomputer's own 5V supply is to be 477, 8 used to power the logic supply to the circuitry. IC4 provides a reference voltage which tracks OVL the Vp power supply. This reference will be approximately 1-8V for a 12V supply. N/C • 5V I C3 I C4i, 412 IC5b TO PIN 7 10011 100n r 25V THE DRIVER CIRCUITRY IC 5o OF IC5 .4 1 DISC 10)i IC6 is a digital to analogue (D/A) converter I PE6114 T .,§c T T IC5 741.502 with a built-in data latch, which connects to OVL the microprocessor's data bus. Data is latched Fig. 7. Decoder circuit in by the required output of IC2. IC7 is a TCA2365 dual power op-amp which drives the motor differentially to provide both forward and reverse control from a single sup- a `13i-Colour' I.e.d., glows green for forward possible. I can assure you, from practical ex- ply voltage. (It's based on an analogue version direction, red for reverse and turns off in the perience, that connecting +12V to the data of the differential driver in Fig. 6). IC7a am- stationary condition. lines by accident will certainly cause some in- plifies the output of IC6 and provides the The use of an 8 bit D/A converter allows teresting permanent changes to the way that positive output phase, while IC7b inverts this 127 forward speeds and 127 in reverse, your computer operates! positive drive signal about a half-rail reference although it is unlikely that the electric motor in Vref, and the half rail reference to IC7 pin 7, voltage set by R17, R18 and VR2, and use will operate all the way down to OV. Note are both derived from the +Vp rail to ensure provides the negative output phase. that OVL, the logic zero volts supply, and the tracking of the motor drive outputs if Vp When the output of IC6 is at OV, pin 1 of power zero volts OVp, have been wired back varies at all under different load conditions. IC7a is near to OV and pin 9 of IC7b is near separately to the power input area around IC3 This circuit has successfully been used to to the +ve supply. When the output of IC6 is to help ensure stability and an absence of control a 12 volt model train set by microcom-

at Vrel; the reverse is true. When IC6's output noise problems with the logic supplies. puter. The only programming requirement is is at half Vref• both power op-amp outputs are GREAT CARE must be taken when wiring to output the relevant motor speed values to at half the supply rail and the motor is up the circuitry and assembling components the port or ports in question. Hence, for a port stationary. Presets VR I and VR2 alter the on the Veroboard, and tests should be done address of 24 (Hex) for example, the assem- gain and offset of the output voltages, and Dl, prior to connecting to the computer as far as bled Z80 machine code for full speed forwards

31 Practical Electronics February 1985 I•13y TO•20V/' •Vp 0

05 • 5V 4 166002 1N6002 • 51/ 0-- (FROM 1C3 C6 100n D,s, 1C7a C7 R11 012 07 0 101 FR0m1C4) 470 060 VRE , v,REF IF- OVp 100n DISC FROM 050 RB C15 MICRO - 04 0 DATA OUTPUT R9 VR1 --° 1000 PROCESSOR RED UP'S °I TO MOTOR 03 0 25V DATA 106 BUS 02 0 IC6 47k 22 7 R10 CB DI 0- = ZN428E-N 106 (•VE GAIN) 07 220,, DO 0 EN 1N GREEN OVL 4002 OVp 0 LATCH 0 (FROM 1C2 PI621 R15 111 1f1 RI -COLOUR OVL 0 1 613 LED 22k (FROM IC31 014 v DB 164002 22k C9 P17 616 T 220n 10 202 1C7b

R18 862 1C7 = 1CA2365 * = CB B C9 SHOULD BE 100n IF TCA 365 15 ARE USED C11

(-BE OFFSET) VR 4 k7

PEW., 0 V L Fig. 8. Driver circuit

LATCH 1ORO 0 OUTPUTS V7171 0

AS @ Al @ A2 @ A3 0

• Si • 52 • • 53 • 54

A4 @ 07 ® 06 AS 0 05 A6 0 DO ® 03 0 A7 @ 02 Cn DO

Fig. 9. Veroboard layout

could look like this: 255 would suffice. (36 is the decimal don't forget the heatsink on IC7! The i.c. has 3E 00 LD A,OFFH equivalent of 241-I, the port address, and 255 been placed at the edge of the board to allow ; Put required value in Accumulator. the decimal equivalent of OFFH.) For full for this. The resulting motor speed control D3 24 OUT (24H),A speed reverse use the value 00H (0 decimal), provides a simple illustration of a typical use ; Output the Accumulator to the port. for stopped use 07FH (127 decimal), and for for power op-amps, either as two single In BASIC, the simple instruction OUT 36,- slower speeds use values in between. Finally, devices or a pair as used specifically in Fig. 9.

32 Practical Electronics February 1985 EUD3 'CV ffN N WAD SIMPLIFIER / 4111111:111111Z 1111111 % 1111144

See and hear software coming down the line and get the LOAD level right first time, every time

M AINS M O NIT O R PR OJE CT EVERYDAY ELECTRONICS and com uter PROJECTS

FEBRUARY 1985 ISSUE ON SALE FRIDAY, JANUARY 18

3 3 Practical Electronics February 1985 JOHN M. H. BECKER

NY electronics enthusiast needs a signal generator and GENERATOR CHIP frequency meter nearly as much as a soldering iron and A An XR2206 function generator chip has been chosen in multimeter. The last two should be part of anyone's preferance to the normally selected type 8038 as it has a workshop but the degree of enthusiasm does not necessarily greater variety of waveforms available, together with a wider warrant the expense of highly accurate generators and coun- sweep range on each selected setting. The oscillograms ters. Often only an indication of approximate frequencies is show the wide range of waveforms available. The basic fre- required, together with a unit that makes readily controllable quency range is selected by Si, bringing in the desired fre- sounds with suitably shaped waveforms. quency setting capacitor C4—C7. The frequency generated

Fig. 1. Block diagram of the Signal Generator and Frequency-Voltage Converter

IRATE

\ 0 SWEEP GEN VCO BUFFER .•-•-•-•••• ••0 FREQ CONTROL SHAPE LEVEL SELECT SELECT

f OUT

0 ExT f INPUT F-V 0 METER

SLOPE RANGE SELECT SELECT 'PE S 76A

This unit has been designed as a reasonable quality, can then be controlled by either a varying voltage or a vary- moderate cost, dual purpose unit suitable for average and ing current. For normal manual selection of the desired fre- addicted constructors alike. It produces well shaped quency, current control is used, and is relative to the waveforms of frequencies ranging from 2Hz to 78kHz in four resistance of the total of VR4, VR5 and R8. In this mode tunable ranges, and includes automatic ramp control of a VR5 is taken directly to ground by S5. As the resistance of frequency sweep, both upwards and downwards. Ad- these potentiometers decreases, so the output frequency ditionally it includes a frequency to voltage converter that rises in relation to the formula: f = 1/1R x (C/1000) ) x can be coupled to an ordinary multimeter, or digital 1000, where C is the value of the selected capacitor C4 to voltmeter to give a direct read out of the approximate fre- C7 in microfarads, and R is the total resistance in circuit with quency being generated, or fed in from an external source. It pin 8 of IC2. is intended for use with an existing power supply or, for short V24 provides coarse tuning of the frequency, and VR5 periods with batteries, from 9V up to 18V dc. Provision has fine tuning. The maximum resistance range that is permissi- also been made to mount discrete power supply compo- ble with IC2 is from 1K to 2M, though is limited to a max- nents directly onto the p.c.b. so that the unit can be fully imum of about 1 M in this unit. This allows a reasonable independent of other equipment. overlap between the switched ranges, without making the

Photograph illustrating the external assembly of the Signal Generator and F-V Converter

34 TEST AP, OJECT

FREQUENCY GENERATOR SPECIFICATION... Basic switched frequency ranges = (1) 2Hz to 81Hz, (2) 20Hz to 851Hz, (3) 200Hz to 8400Hz, (4) 1970Hz to 78800Hz. Coarse and fine tuning of selec- TOLERANCE ted frequency range. Switch selected waveforms — The figures quoted refer to those obtained on the sine, triangle, square, ramp, pulse, and variations (see prototype and may vary slightly in other units in accor- photographs 1-6). Sweep modulator—rising and fall- dance with normal component tolerance factors. ing ramps, switch selectable, rate 6 to 40 cycles per minute. Frequency outputs—switched, buffered or un- FREQUENCY TO VOLTAGE CONVERTER buffered via amplitude control from nil to 5V peak to Good linearity from 200Hz to 30kHz directly peak. Fixed OV/A-5V amplitude square wave derived readable on a standard multimeter or digital voltmeter. from internal oscillator or external source up to about Accessible internally and externally. 80kHz. Four switched reference frequencies. +VE 544-B564-BS2A -C ARE GANGED POWER90 TO 18VLINE DC +VE 16 PINICI 4= =TL084 PIN 11= DV 01010k 15 007 10 S2A SHAPE.] TR2 to 41,7 470R4 S 4A 1N4148DI02 C3 011VR 6 50k 251, RB 1. 1-YE 1N4 48 22p 104 IC 2 500 2 87 Cl. 862200

[Rork VCO SO 52C 9 10 22,u R13580k go VRS J Stt's • S6A o VRG 2 SWEEP!10k ' 1 25k IM 914 028 100kRIO ..1?1 (COARSE FINE 1801, TEST5613 V R 3251, R911, 100kR17

+VE CIO +VE VR11 mim 100 n T100n T 100nonem C18* 1M2ROD 021101, 2501, CI4 R19 *C18 USED IN 1001,922 VRIO100k 0235101, 013 22,u 4k7 DIFFERENT POSITION 0 7 WITH OPTIONAL PSU Cli IC 1d C12 5 2 403 ?04 100n 100k J62 100n IC3 025 024 940 OCT EXTERNAL FREQUENCY 100n 10k 1000 INPUT TO F-V CONVERTER 1001, 026100k 10kR28 -I-VE 030Ok 031 J1(1

F ROEU W (NOTOPTIONAL INTEGRAL POWERPART OFSUPPLY PROJECT) 400mW +I 10 VOLT METER

A I_PE574A

Fig. 2. Co mplete circuit diagra m of the Signal Generator and Frequency-Voltage Converter

Practical Electronics February 1985 35 tine tuning too coarse. Switching in VFij by bb instead ot O UTP UT KO UTIPJLi VR4 and 5, a preset reference frequency can be selected. In most instances it is preferable for the amplitude of the The i.c. contains its own current controlled amplifier and the different waveforms seen at the final output to be roughly amplitude of the signal generated as seen at pin 2, is pre- equal. As previously seen there is an inherent level difference settable by VR6. This controls the sine, triangle, and ramp between the three main waveform ranges, IC1C is thus in- waveform maximum levels. The squarewave however is cluded to even these out. The gain of this stage is of course derived from a different section and is at approximately full dependent upon the relationship of the total input resistance line level amplitude as determined by the current through to the value of the feedback resistor R16. The choice of the load resistor R12. The shape of the triangle and ramp resistors R13—R15 ensures a reasonable match of the levels. waveforms is predetermined within IC2 itself. For sine wave The inverted phase output from IC1C is decoupled by C9, related waveforms, shaping is preset by VR8, and the sym- taken via S3 to the level control VR9 and then to the output metry trimmed by VR7. via S9. However the frequency pass range of IC1C is less than that of the range available from IC2. For normal audio W AVEFOR M SELECTION applications, the frequency response of IC1C is sufficiently Three basic waveform selections can be chosen with S2. adequate, but distortion becomes more prevalent as the With S8 open, the choice is sine, triangle and square. In frequency rises above about 30kHz, as shown in the os- position 1 (sinewave) the output comes from pin 2 of IC2, cillograms. and VR8 is in circuit, controlling the sine shape. In position Additionally the loading of C9 causes square wave distor- 2, (triangle wave), the output again is from pin 2, but at a tion at lower frequencies. S3 is thus included to bypass IC1C level approximately twice that of the sine wave and VR8 is so that the output is unbuffered allowing the full range of out of circuit. In position three (squarewave), the output is IC2 to be used. Note though that the unbuffered output also taken from pin 11 IC2. With S8 closed the squarewave is contains a d.c. bias that is approximately half line level with directly fed to the control pin 9, and internal circuitry of the S2 in positions 1 & 2, and that the phase is inverted. chip is automatically switched by it to produce ramp related waveforms in the first two positions of S2. In this mode the frequency of oscillation now becomes affected by the value S WEEP OSCILLATOR of R9 and the formula changes to: f = (2/C/1000) x (1/R) x When testing out some circuits it is sometimes preferable 1000, using the same parameters as before. Effectively this for the frequency range to be swept upward or downwards means that the frequency with S8 closed will be approx- at a controlled automatic rate rather than by manual control imately twice that with it open. In position S2, looking at the of a potentiometer. The ramp generating circuit around IC I A inverted output of IC1C, the rising ramp is sine shaped, & ICI B provides this control. The frequency range of ramp followed by the steep drop. In position 2 the rising ramp is generation is determined by Cl with larger values giving linear, again followed by a steep drop. Study of the second slower rates. VR1 provides the tuning of the sweep rate formula though will show that the steepness of the drop is setting. The direction of the ramp produced is governed by related to values of R9, and the controlling resistance on pin the direction of voltage flow through D1 and D2. S4 selects 8. As- the two resistances approach equality, so the the diode routing, and reverses the polarity of the controlling steepness lessens, and a falling ramp also develops. The voltage through VR1 in relation to the reference level at C2. best ramps are thus created with the resistance on pin 8 at The changing d.c. voltage produced by the ramp controls IC2 the greater end of the scale. In position 3 the output is again via VR2, S9, VR4 and VR5. In this mode voltage control of from pin 11, but consists of a mark-space pulse, the duty IC2 is being employed in addition to current control. For cycle of which determined by the formula: RAARA + RB), correct operation of IC2 the voltage sweep seen at the wiper where RA is the resistance on pin 7, and RB that on pin 8. of VR2 must lie below 3V, above this and the oscillator of The negative going pulse length is moderately constant IC2 will cease. VR2 thus needs adjustment to keep the throughout the range for the same capacitance selection. sweep voltage within this range. The frequency control The mark-space factor is also reflected in the shape of the range provided by the varying voltage is less than that ramps with a flattening of the apex, but is really only produced in the manual mode, and VR4 and VR5 are used to noticeable at small values of capacitance. select the desired band width.

M W W W N

11 1 11 11111 1 11111 0 Sine (normal) S2 1 Triangle (normal) S2 2 Square (normal) S2 3

Sine (ramp) S2 1 Triangle (ramp) S2 2 Square (pulse) S23

36 Practical Electronics February 1985 i gak emithdbi

Sine (high freq) S21 Triangle (high freq) S2 2 Ramp (high freq) S2 3

FREQUENCY TO VOLTAGE CONVERTER put 5V squarewave. S9 can switch in this frequency output IC3 performs the f-to-v conversion, producing an output in place of that produced directly by IC2. This means that an voltage that, within the range, is related linearly to the fre- external frequency of indifferent level and shape can be quency fed in. The range available is determined by the gain converted for controlling circuits that require a 5 volt given to the feedback via 827 and VR11, with a slew rate squarewave. The external loading permissible though is and ripple reduction level set by C14. High values for C14 limited by the value of R30 and too great a load will reduce will give reduced ripple for lower frequency signals, but will the voltage. increase the time taken for the voltage to stabilise when the frequency is changed. The relative minimum output voltage PO WER SUPPLY in the absence of an input frequency should be as close to Most enthusiasts probably already have power supplies in zero as can be set by the bias control VR10. VR11 is used to their workshop capable of driving this unit, and so a separate set the maximum range. The output voltage is referenced to one is not included. The minimum voltage requirement is 9V, an intermediate level of about 5V as set by Zener diode D5. and the maximum permissible +18V as dictated by the limits The negative lead of the meter used to monitor the voltage is of IC3. The current drawn is about 30mA, up to 20mA of taken to this level, and the positive lead to the output from which is consumed by IC2. This current is a bit too high for pin 12, IC3. If the meter negative lead were to be taken to the unit to be powered for long periods from a battery sup- the normal OV or ground line then the reading would also ply, though one could be used briefly in an emergency. Alter- contain the reference voltage of 5V and inaccurate readings natively a battery eliminator might be suitable, providing it would result. For stable operation of the conversion, the in- can tolerate the current without the voltage dropping below put frequency seen at pin 11, IC3 should be at a constant 9V and that the ripple content is negligible. The printed cir- level of about 1V p-p. To maintain this amplitude even for cuit board though includes positions for the mounting of the low level input signals, the signals are taken via the gain rectifier and voltage regulator as shown in the suggested op- stage IC1D for external signals which gives an amplification tional 12V power supply circuit. This supply was not used in of about, a little over 100. The signal is then attenuated to the prototype and is not regarded as an integral part of the the optimum level by diodes 03 & D4. For internal fre- project. The transformer should be bolted to the metal box, quency reading, the signal is taken direct from the output and normal mains electricity safety precautions observed. of IC1C, and similarly attenuated. S7 selects the choice of Note that with this suggested power supply C18 has its internal or external frequency monitoring. In addition to positive end connected to a different track position, and it producing a frequency related voltage, IC3 also produces a may be necessary to mount it vertically rather than horizon- square wave output of 5V amplitude. There is a slight time tally. The use of a heat sink with the regulator i.c. should not lag between the edges of the input frequency and of the out- be necessary.

COMPONENTS.

RESISTORS C13 56p polystyrene MISCELLANEOUS 470µ, 25V elect. R1,R7,R15,R17,R22, P.c.b. and p.c.b. clips (4 off) R25—R27 100k (8 off) Round knobs (6 off) 82,83,R1 8,819 4k7 14 off) I.c. sockets, 16 pin, 14 pin 12 off) R4 470 SEMICONDUCTORS Jack socket, 3.5mm R5 47k ICI TL084 (quad op-amp) Jack sockets mono (2 off) 86 18k IC2 XR2206 Box and rubber feet 88,R10,R11,R12,R21 Meter terminals 12 off) IC3 9400CT (AS. 307 070) R28—R30 10k 18 off) DI—D4 1N4148(4 off) R9,R24,R31 1k (3 off) D5 5V1 Zener, 400m W R13 680k R14 180k S WITCHES S1,S2 3P4W (2 off) R16 390k POTENTIO METERS 820 1M2 S3,S5,S7—S9 SPDT 15 off) R23 510k VR1 100k mono rota S4,S6 DPDT 12 off) All resistors +W +5% VR2 10k skeleton VR3,VR7 25k skeleton (2 off) CAPACITORS VR4 1M mono rota C1—C3,C8—C10,C17 22µ, 10V elect. (7 off) VR5 25k mono rota Constructor's Note C4 1µ, 63V elect. VR6 50k skeleton A complete kit of parts is available from: C5,C11,C12,C14—C16, VR8 500 skeleton Phonosonics, 8 Finucane Drive, Or- C19,C20 100n polyester (8 off) VR9 10k mono rota pington, Kent BR5 4ED. Price £54-00, C6 10n polystyrene VR10 100k skeleton inclusive of VAT. Post and packing C7 in polystyrene VR11 250k skeleton £1.00.

111121101,

Practical Electronics February 1985 37 ASSE MBLY * DOTTED LINE SHO WS CONNECTION OFC18 IF OPTIONAL PSU IS USED 16 After the straight forward component assembly and sub- ** IC4 AND RECTIFIER ARE PART OF OPTIONAL 1 sequent joint checking procedure has been carried out, wir- PSU AND NOT INTEGRAL PART OF PROJECT. ing should be commenced in a methodical fashion, ticking off each wire on the wiring diagram as connections are made. First connect up all the panel controls between themselves. Secondly wire up to all the p.c.b. points closest to the

front panel. Finally connect up the rear and remaining con- 0-4 R22 1-• nection points. These latter wires should preferably be 5( R21 brought under or round the edges of the p.c.b. Taking them 18 2 (.Cli .,!) r over makes the wiring untidy. Keep the wiring short, but 5.4 R20 1••• long enough for turning the board over for examination R2 without over straining the connections (too much flexing of •-•I R17 1-0 3 taut wires can cause breaking at the joins). The prototype ® 5 97 4 51 915 I-•• ® • 19 has the meter terminals on the front, but with hindsight, 04 R6 k mounting them on the back would be better. 1.

The regulator IC4, and the rectifier R EC1, are part of the 0 5 '4 =1:1-0 0 optional power supply, together with the transformer Ti. 6 These components may be omitted if not required as the • 5.1 R10 f•-• . 219 „ C 6 ) . unit will run quite efficiently from any 9V battery. R 9.4 911 1-4 14 21 ® 7 106) 22 5.1 913 23 SETTING UP 8 C7 24 A fair selection of presets has been included to enable the 9 maximum accuracy to be obtained throughout the unit. The 25

only really critical one is VR2, as the sweep control may not 26 operate if this is incorrectly set. Inadequate setting of the 10 .4.- - €1 11 0 (0 C5 41) • C20 • 27 others will only cause lack of linearity. If an oscilloscope is 1111 R9 I-5 28 not available intelligent decisions will need to be made, +

listening to the sounds while adjusting the presets. 12 • R8 1..5 First, S1 position 1 (lowest freq), S2 position 1 (sine), S3 29 13 on (buffered output), S4 either way, S5 off (sweep off), S6 acR 30 off (manual freq control), S7 off (internal f-v), S8 off (standard waveforms), S9 off (vco output), VR1-3 midway, 31 41926 1-.• VR4-5 max clockwise (highest freq), VR6-8 midway, VR9 ▪ 923 fr• max, VR10-11 midway. Switch on and check that pin 3 32 ICI A, pin 3 IC2 are at approximately half line voltage, and I (II C15 0) that the positive end of D5 is at about 5V. Plug in to normal C13 4 R213 k amplifier. If no sound is heard then check the wiring, and 4,4 R24 kl OS R30 k 9 that the switches are wired the correct way up. Assuming (5 C12 16 that sound is heard, check that VR4 and 5 vary the fre- *) C I') VR1 • 931 1-5 111-1 R 7 1.41 KO) 33 quency, and that Si changes the ranges. Switch on S6, and •-1R25 I-. l''"E =I HI adjust VR3 to the desired fixed frequency on the second range of Si. In the author's unit this was set for approximately 440Hz. Check that S8 brings in the ramp associated IPE573A1 T14 '± 5

Fig. 3. (Above) Showing the p.c.b. design and component layout of the Signal Generator. (Left) Photograph illustrating the internal view of the chassis assembly showing the switch, sockets and p.c.b. layout

IOW 111111117 en- ingpingrom

3 S Practical Electronics February 1985 1INPUT OUTPUT,

EXT. POWER SUPPLY INPUT Si PIN 9 ONLY USED AS CONVENIENT OV TAG PCB PINS 29 8. 30 GO TO TRANSFORMER 12V TAGS IF USED, IN WHICH CASE PCB PIN 27 363 IS NOT USED

r TEST INT/EXT FRE0 F -V 3 2

VCO RANGES 1 - 4

VR4

SHAP E 1 RiU TPUT 32 IVCO 7 VCO 6 FSWEEPI. FINE FlIATE 3 Lcc sE

19 2 22 12 11 S5 CO I 4

1 562 SKI

2V -0, -F40 011, 1 5

IMETE_Ri METER SWEEP SWEEP PESTS Al L -V +V ON/OFF SLOPE

Fig. 4. Wiring diagram of the Signal Generator

ranges of waveforms, then switch back to the normal range, about 5 volts, then after the initial adjustment has been and to squarewave. Monitor the output jack socket and note made the meter can be switched to its lowest range for the squarewave amplitude level. Switch to triangle wave and greater precision. Set meter to a range for monitoring exac- adjust VR6 until the amplitude is similar without flattening tly 1V. Switch S7 back so that the 10kHz signal reaches IC3. of the waveform peaks. Switch to sine wave and adjust VR8 Very carefully adjust VR11 until a precise voltage of 1 volt is for the best sine shape, then VR7 for the best sym metry. If obtained. necessary readjust VR8. The maximum frequency that can be read will be about Switch S3 to bypass and check all waveforms can be 30kHz to 35kHz, beyond this IC3 will fail to respond and switched in, though as previously stated they will be at show a constant reading of around 3-5V. Applying a lkHz widely varying levels. Switch S6 back to manual control, signal should produce approximately 0-1V. Tracking then S5 to sweep control. Check that a ramp waveform ap- downwards in frequency, linearity will be roughly maintained pears at pin 1 ICI A, and that switching S4 varies the direc- until about 200 Hz or so, depending on the accuracy of the tion, also that VR1 varies the rate with the ramp in both setting of VR10 and VR11. Once the boundary extremes directions. Return scope probe to the output jack socket, and have been established, a direct reading of frequency can be adjust VR2 for the smoothest sweep response. If the wiper is taken from the multimeter by converting the voltage into the too far to the OV end the generator frequency will dwell at readily calculable frequency. Thus if 1V = 10kHz, 3V --r-- the high end, with it too far towards IC1 the generator will 30kHz, 0.5V = 5kHz, 0.05V = 500Hz, etc. Check that cut out at the low frequency end. With careful adjustment a an external frequency can be monitored in the same way, smoothly varying rising or falling sweep range can be set. then finally that a squarewave output of about 5V is Switch off the sweep control and set a frequency output available from pin 8 to IC2. from IC2 of precisely 10kHz. Check that an attenuated ver- After setting up the f-v converter the frequency controls of sion of this frequency reaches pin 11 IC3 via S7. With the the unit can be calibrated and control legends applied to the external input jack socket grounded (as it will be without a panel, using a rub down lettering like letraset or similar, then jack plug in), switch S7 to external. Connect a multimeter coating them with a suitable spray protector. If care has across the meter output terminals and adjust VR10 for a been taken in the setting up, the end result will be a mar- reading of exactly zero volts. Start off with a meter range of vellously versatile dual purpose new unit for the workshop.*

Practical Electronics February 1985 39 rings, not all of which are perfectly circular,, Having satisfied myself that it really was a and their composition is unknown. new star or nova, I made a telephone call to If all goes well, we should learn more about the observatory at Herstmonceux. I was, of them in January 1986, when the Voyager 2 course, fairly sure that the star had already spacecraft makes its pass of Uranus. been reported —and so it proved; it had been Meanwhile, there is speculation about the discovered some hours earlier by Kentaro possibility of a ring-system round the outer- Osada in Japan, before darkness fell over most giant, Neptune, but the presence there of England. I imagine that I was about sixtieth in a large retrograde satellite (Triton) may have the list of independent discoverers; the star prevented any rings from being formed. could not possibly have been overlooked by Again, we pin our hopes on Voyager 1, which anyone with more than a rudimentary will rendezvous with Neptune in the late knowledge of the constellations. summer of 1989. The most remarkable fact about Nova Cygni was that it brightened up by at least nineteen magnitudes in only a'few hours. This HALLEY'S CO MET was a record, both for amplitude and for Halley's Comet is, of course, still much too speed. Its decline was also unusually quick. I faint to be detected except with very powerful estimated its magnitude as 1.8 on 30 August, so that it was then much the brightest star in instruments, but recent studies show that it the constellation apart from Deneb; but it had RIN G MASTER may prove to be somewhat brighter than had dropped to below 3 by 1 September, below 5 Perhaps the most interesting development been expected. Unfortunately, this does not by 4 September, and faded below naked-eye during the past few months has been the visual mean that it will be a brilliant spectacle, as it visibility by 7 September, when I saw it as detection of the ring-system surrounding has been on many past returns. fiery red—in fact, as red as any star I have Uranus. The rings were first found indirectly, It should become a naked-eye object at the ever seen. Within a few months it had become because they produced a series of occultations end of 1985, before perihelion passage on 9 too faint to be observed except with powerful of a faint star; subsequently, D. A. Allen and February, 1986, but British observers will telescopes. J. Crawford, at Siding Spring Observatory in need clear skies. When at its best, after Apart from Nova Cygni, only three novae Australia, photographed them in infra-red. perihelion, the comet will be in the far south— well placed for Australians and South seen since 1930 have attained the first Studies of them have now been carried out magnitude: DQ Herculis (1934), CP Lacertae by Richard Terrile and Bradford Smith, using Africans, but not for Europeans, who will not see it at all until it has faded considerably. (1936) and CP Puppis (1942), though others the 2.5-metre reflector at the Las Campanas have become visible with the naked eye— Observatory in Chile together with a highly notably HR Delphini, which was discovered in sensitive CCD or Charge-Coupled Device. 1967 by the well-known English amateur The ring-system is clearly shown, together NOVA CYG N I—A NE W LOOK George Alcock and had a very prolonged with all five known satellites—Miranda, Ariel, On the evening of 29 August, 1975, I went maximum of around the fourth magnitude. It Umbriel, Titania and Oberon. The pictures into my observatory to make some routine ob- is still above magnitude 13, and probably will show the great power of the CCD, which is at servations of variable stars. When I looked up not fade much further, as this was also its pre- least thirty times more sensitive than any at the familiar constellation of Cygnus, I had a outburst magnitude. photographic plate. surprise. There, shining down unmistakably, However, the exceptional behaviour of The rings of Uranus are quite unlike those was a bright star which had certainly not been Nova Cygni has led to particularly detailed of Saturn. Terrile and Smith find that their there on the previous night. I estimated its studies of it, and efforts have been made to albedo or reflecting power is only about 2 per magnitude as 2.4, slightly fainter than detect a cloud of debris round it. This has now Gamma Cygni, the central star of the "cross" cent, so that they are blacker than coal-dust. been a successful operation. They are also narrow; there are at least eight of Cygnus.

THE SKY THIS MO NTH

Winter skies are always glorious, thanks to the Epsilon Aurigae, at the apex of the triangle, is an ex- presence of Orion, the Hunter, and his magnificent tremely luminous supergiant, at least 60,000 times as retinue, but at the moment the dearth of bright planets powerful as the Sun. Every 27 years it fades down by continues—apart from Venus, which is at its very best in almost a magnitude, not because it is intrinsically the evenings. Mercury is, in theory, a morning object, variable but because it is being eclipsed by a companion and may indeed be glimpsed just before sunrise, but it is which has never been seen at all. well south of the celestial equator, so that European ob- The nature of the invisible secondary is still a matter servers are unfavourably placed. for debate. It was once believed to be a very young star, Mars may be seen in the south-west during the early not yet hot enough to shine; there were also suggestions evening, and moves from Aquarius into Pisces by the end that it might be a black hole, but it now seems more of the month, but its magnitude is now only 1.2, and no likely that it is a relatively small, hot star with an telescope will show much upon its surface. Saturn, in associated extensive shell of material. The last eclipse Libra, rises well before the Sun, but is low down and by ended in 1984, so that for more than two decades no means prominent, while Jupiter passes through con- nothing further will be happening. junction on 14 January and is therefore out of view Look at the 'Kids" and you will see that Epsilon is now altogether. There are no eclipses this month, and no the brightest member of the trio. The faintest, Sadatoni bright comets are expected. The Moon is full on 7 or Zeta Aurigae, is also an eclipsing binary with a period January, and new on the 21st. of 972 days, but we know much more about it; the During winter evenings the brilliant yellow star primary is a red supergiant, while the secondary is a Capella is almost overhead (a position occupied by the much smaller and hotter star. equally brilliant Vega during evenings in sum mer). Close It is sheer coincidence that these two exceptional beside Capella lie the three fainter stars making up a eclipsing binaries lie side by side in the sky. There is no triangle. They have been nicknamed the Haedi or 'Kids', true connection between them; Epsilon is much further and two of them are very remarkable objects. away from us than Zeta.

.40 Practical Electronics February 1985 Using the 82-inch reflector at the 1918, both of which became much mdre 150,000 light-years from us. Pulsars are McDonald observatory in Texas, G. and A. de brilliant than Nova Cygni. Indeed, for a brief rapidly-spinning neutron stars which slow Vaucouleurs have recorded the debris un- period Nova Aquilae outshone every star in down as they age. From the measured mistakably. The cloud shows up as an ellip- the sky with the exception of Sirius. slowing-down of the Large Cloud pulsar, it tical blur, 3.5 x 2.5 seconds of arc across, has been estimated that the outburst occurred with an integrated magnitude of about 161. about a thousand years before our present-day Presumably it is expanding; and if the distance view of it. of the nova is 4,500 light-years, as seems The rapid increase of Nova Cygni 1975 likely, the expansion rate is approximately 800 SUPER N OVAE raised initial hopes that it might be a miles per second. There is a fundamental difference between supernova—something which astronomers ordinary novae and the much more powerful would warmly welcome, because it cannot be supernovae, which are much less common. said that our knowledge of supernova Only four supernovae have been seen in our mechanism is at all reliable (there seem, in- Galaxy during the past thousand years; those BIN ARY SYSTE M deed, to be two quite different types of super- of 1006, 1054, 1572 and 1604—all before the novae, one of which involves the collapse of a According to modern theory, a nova is a invention of the telescope, though supernovae binary system, made up of an ordinary main massive star while the other indicates the com- are so luminous that they may be detected in plete destruction of a white dwarf). sequence star together with a white dwarf. external galaxies many millions of light-years We could learn much more if we had the White dwarfs are stars far advanced in their away. opportunity to study a relatively nearby super- evolution; they have used up their nuclear From the few accounts which have come "fuel", and have become very small and nova with modern equipment. Nova Cygni down to us, the 1006 supernovae, in the almost incredibly dense. was therefore something of a disappointment; southern constellation of Lupus, became as In a nova, the white dwarf pulls material but it is still extremely interesting, and it will bright as the quarter-moon, while the other away from its larger, less dense companion, be important to find out how the newly- three outshone Venus. The 1054 supernova discovered cloud of debris develops. and there is a build-up of material around the has left the gas-cloud of the Crab Nebula, There is one rather sobering thought. When dwarf, leading eventually to instability and a which contains a pulsar. we look out into the Galaxy, we are also look- violent, usually short-lived outburst. For many years the Crab was regarded as ing into the past. Nova Cygni exploded well Associated debris is only to be expected, and unique, but recently a very similar supernova has been detected with many former novae— over four thousand years ago; the expanding remnant, including a pulsar, has been found in such as Nova Persei 1901 and Nova Aquilae cloud we see today was produced long before the Large Cloud of Magellan, more' than astronomy had become a true science!

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Practical Electronics February 1985 41 A selection of readers original circuit ideas. Why not submit your idea? Any idea published will be awarded payment according to its merits. Each idea submitted must be accompanied by a declaration to the effect that it has been tried and tested, is the original work of the undersigned, and Ingenuity that it has not been offered or accepted for publication elsewhere. It should be emphasised that these designs have not been proven by us. They will at any rate stimulate further thought. Articles submitted for publication should conform to the usual practices of this journal, e.g. with regard Unlimited to abbreviations and circuit symbols. Diagrams should be on separate sheets, not in the text.

THER MISTOR HE conventional bridge circuit recom- Tmended for thermistors is somewhat inaccurate. Better results can be obtained using the arrangement shown here. The THER MO METER op.amp, IC2 acts as a voltage source, with current measured by the meter ME!. This configuration corrects for most of the thermistor's non-linearity. An offset current 5009A flows through R5 and VR1, and sensitivity 250mA 750uA 50°C is set by VR2 and R6. Assuming a full- 25°C 75°C scale current of 1 mA, an output of 1m ImV/°C is conveniently obtained at the 0°C 100°C output and this can be used to drive a CONSTRUCTION OF TEMPERATURE PROBE chart recorder, for example. The supply USING GLASS BEAD TYPE THERMISTOR voltage is regulated by IC 1, and a 3-way switch allows the battery to be checked. Resistor values for two types of NTC f PE155.1 thermistor are given in Table I. JA-03 is metal-sheathed (RS no. 151-120) CALIBRATION OF METER 1mA FS D and VA3704 (Mullard no. 2322-627- Construction and calibration of the Thermistor Thermometer 11472) is a glass-bead device. Both have a resistance at 50°C, of the order of 1k7. PT RI 52 65 R6 R7 Kettles and ice-buckets are unpredic- 30 70 100 JA - 03 7k5 5k6 22k 1k2 0 C. °C table gadgets! Calibration was done at 10, ERROR '33 - 20 *1-7 -26 VA3704 10k 6k2 10k 1k 100 50 and 90°C, using a water-bath and AT .4.0 -2-5 •2.2 -32 TABLE 1 laboratory-grade mercury thermometer. TABLE II 2 The error curve is cubic, with a deviation i0 30 50 70 90 within 2 or 3 degrees centigrade over most of the range, increasing near the 0° and 100°C limits. C. J. D. Catto, Elsworth, Cambridge. 'Cl 0 5V 78 LOS

ImV /°C RI * OUTPUT * See toblel 0 0 ** See lext

C3 VIII 56 SET ZERO 120 TURN)

63 IC2 - 10n LM312 100 VR2 500 } SE T F.S. R4 01 0.P. Si Posifions 120 TURN)

9, 1. OFF NENE 30 2. BATT. CHECK 3. 0°C

06 *

57 On

PROBE PE 10M

42 Practical Electronics February 1985 LOGIC RECORDER +5v 20 DATA 00 0 1E1/2 1-I514 HE logic recorder is designed to fill the IC3 PIN 5

Tgap between the logic probe and the Id a logic analyser by displaying a sequence of •—/ W 7455 0 R o6 " +5V D8 eight data bits on a bank of 1.e.d.s. Data is stored synchronously with the system clock after a trigger pulse from the circuit k O under test. IC2d 71LC S4273: IC1b 74L586 Data is fed into IC4, an octal D-type 741.500 ARMED I 04 R 7 SIT flip-flop wired as a shift register, though a A012/

74LS164 shift register could be used in- 0111 stead. D2 represents the most recent data. IC2c IC3 74 L585 IC2b 74L593 Suppose that latch IC! a/b is set so that TRIGGER 74L586 , 7 R5 D4 D 10 is unlit. IC! pin 6 is high so IC3 is reset, its 'A' output is low, IC Id is disabled R2 11, and IC lc is enabled via IC2b. When the R4 Die,/ I TRIGGER EDGE !Cid 741_500 ARM button is pressed the latch sets, ONO 02 lighting DIO and freeing IC3 to count. On RI IC2a IC 10 74 5585 745500

the rising edge of IC2c pin 8, the single-bit CLOCK counter in IC3 clocks, disabling IC lc and the ARM button and enabling IC 1 d to IC3 PIN ID £ 7 ' . „ 1/2 PIN 7 clock IC4 and, via IC2d, the 3-bit section IN5400 r IPE1632.0) of IC3. Os ) After eight clock pulses from the system under test, IC3 pin 11 goes low, resetting the latch via Cl. Provided that the ARM button has been released the logic recorder resets and displays the data received until it is rearmed. May be 1 or 0 IC2a and IC2c are used as programmable invert8rs to select the desired trigger D7 D6 D5 D4 D3 D2 Dl DO ZX SPECTRU M and clock edges. Dl protects the recorder I I X X X X X X against reverse polarity on its power 128 64 32 16 8 4 2 1 BUFFERED supply leads which are connected to the 1 1 I 0 1 0 1 1 test circuit. e.g. D2 and D4 are low INPUT PORT G. Strange, 128 + 64 + 32 ,- 0 + 8 + 0 + 2 + 1=235 Loughborough, (6 BIT) Leics. Table 1. Showing example of 1N127 com mand AosT designs for input ports use I devices such as the 74L5245 octal transceiver, but during the current chip IC1a Id b shortages, these devices are either impos- SKI 74L502 745502 IC C lCl d ICI PIN 14 sible to obtain or very expensive. There are 74 LSO 2 74 LS 02 202 PIN 16 other possible buffering chips, such as the 74LS126, but these are more difficult to I.. 1 1 W / W 111 / W 1 01 1 02 IOR O OV T 1008 T n design a circuit layout for. In my design I have used the 74L5365 RD C IC2 PIN B Hex buffer/driver with gate enable ICI PIN T Vcc inputs—the only disadvantage is that we 16 5 now have only 6 inputs. 1C2 E1 7455365 The circuit itself is very simple: the port 2 V is I/O mapped by A7 and address 0E 2 SSK2c decoding is performed by IC!, a 74LS02. Thus when the following control lines are low —IORQ to indicate an input output operation and RD to indicate the CPU wishes to read from the I/O port indicated bc by the address on the address bus. The outputs of IC2 are put onto the databus of 5 the computer. Cl and C2 are decoupling

6 INPUTS capacitors. cc Since the circuit is mapped by A7 being low, an IN127 command will give 255 if OV GNO all inputs are high (logic 1), as will be the case if they are left unconnected. If bit I (DO) is low then the result will be 254. Possible results are summarised in Table I. Thus the result of an IN127 command in this case would be 235. A. Moran, Reading, IPE1625G Berks.

Practical Electronics February 1985 43 one every time it receives a clock pulse. For a 5 pin DIN, the sixth output is connected to reset and thus counts through 0,1,2,3,4 and 5. Six pulses are allowed to enable the screen to the tested separately Ingenuity (note however that this is often connected to the middle pin). The clock used to drive IC I is produced by a standard CMOS oscillator based around IC2 (a 4011 quad Unlimited NAND), the NAND inputs being shorted together as shown to act as inverters. This i.c. type was chosen merely so that fewer INTERPRETATION CLOCK PULSE No gates were left unused. A hex inverter c F: Fox DIN LEAD would serve just as well. IC3 and IC4 are 4050 hex buffers used to dtive the 1.e.d.s. The clock frequency is normally about I kHz, providing an apparently constant TESTER display. In this mode any broken connections will immediately show up as unlit

• P.S . 09/10 • I.e.d.s. at 13'. By pressing switch S I the 68k resistor RI, is disconnected and the " 70 7 7 n1'; ' AVE you ever wondered whether all clock frequency reduced so that a more Hyour problems might just be due to a detailed representation of the condition of faulty DIN lead? If so, you'll no doubt the DIN lead is given. Two common types have discovered what an awkward opera- of 5 pin DIN lead exist; straight through tion it can be to test one; but here is a and mirror image. simple solution. STRAIGHT THROUGH —L.e.d.s at `A' The following design will test DIN leads and 'B' should light in the same order. for open circuit, short circuit and wrong MIRROR IMAGE —L.e.d.s at 'A' and 'B' CROSSED .0.05 connections all in one go. Whereas with a should light in opposite orders. Crossed continuity tester you need to test each pin leads can thus be detected by incorrect individually, this circuit gives an im- orders at `B'. mediate indication of the connections (or Any two 1.e.d.s lit simultaneously at one lack of connections) between pins at either end in this mode indicate shorted leads at end. that end. ICI is a 4017, which is a decade coun- Some sample displays are given. Using i°14FZ: ter with decoded outputs. It sends each pin CMOS logic, the unit can be readily high, in sequence, moving on to the next powered by a 9V (PP3) battery. C. Walden, Selby, S. Yorks.

(Above) Some possible fault indications CI R26 100n Nim 6M8 (Belo w) Complete IC2a RI IC2b 4011 68k 4011 circuit diagram of the

DIN Load Tester +VE +VC +VE

01 1 4

02 14 ICI 6 I C 3 D3 14 4050 4017 04

D5 14 ,o

14 06

4111 1.••••

R4 470 '.,.470 70 814-17 470

• 09 85 470

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44 Practical Electronics February 1985 An instant answer to every calculation you will ever make? With a Hewlett- Packard Professional Calculator, the answer is yes. We introduced Calculators for Professionals —

,e3SSS le 9, sophisticated, powerful calculating facilities—around ten years ago, and tarajg our range has a calculator built for the kind of work you do. There is a professional calculator for scientists and engineers, for software and computer specialists, for higher mathematics activities and for business users. Pre-progranuned for your needs Each one is pre-programmed to perform your usual calculations automatically—and in addition, all of them can be programmed by you so you can solve your problems in your own way. So wherever you are, you can have

A complete manual of instructions and programs has been written for each of the HP professional calculator range. answers you can depend on, always at your fingertips. With the minimum of effort, in the minimum of time. Each has a memory that will store information even with the power off. And will come with an owner's handbook, so you are operational right from the start. You can see the Hewlett-Packard professional calculators at your dealer. Or complete the coupon below, and we will send you full details of the Hewlett-Packard professional calculator range and how it can help you. Hewlett-Packard Calculators for Professionals 11

SEND TO , FREEPOST, EnclonT Section, Hewlett -Packard Etd , Eskdale Road , W innersh , • Wolungham, Berkshire, RG11 1BR. Please send me details of the Hewlett-Packard professional calculator range (together with details of mylocal stockists). I am particularly interested in 0 Science and engineering applications DI Software and computer applications 0 Higher mathematics applications 0 Business applications

ttcts°5. Name Position ev‘s- t\'` o caVa o ok ties' Company

13C, e ses' trgs' • It Address 4Y ° ° 1est•osb"1 tes1. .01 ‘,,te O Pe a‘ we's' vot0 so , 000° • 6;,'°?'' tivs °V 0 0 " so °,,,astte4litts Postcode E a H E W L E T T c n es, tita ti‘t to • asNa a. Tel No. PREL 03 P A C K A R D im MI MI MI 1111 11111

Practical Electronics February 1985 45 Superior Quality Precision Made SUPER HY-LIGHT STROBE KIT VARIABLE VOLTAGE TRANSFORMERS Designed for Disco, theatrical uses, etc. INPUT 230, 240V ac. 50/60 OUTPUT 0-260V. Approx. 16 joules. Adjustable speed. Price £45 + £2 p&p1Total inc. NEW POWER RHEOSTATS 200W 1 A Max. VAT £54.05; Case and reflector price £15 + E2 p&p (total inc. VAT 0.5KVA 2/12 A Max. £19.00 New ceramic construction, heavy duty brush £19.55): Foolscap SAE for further details including Hy-Light and IKVA 5A Max. 07.00 assembly, continuously rated. Industrial Strobe Kits. 2KVA 10A Max. £41.00 25 WATT 5/10/25/50/100/150/250/300/500/1k0 3KVA 15A Max. £54.00 1.550 £3.80 + 30p p&p (E4.71 inc. VAT). ULTRA VIOLET BLACK UGHT 5KVA 254 Max. 299.00 50 WATT 2500 £5.50 + 50p p&p 126.90 inc. VAT). FLUORESCENT TUBES 10KVA 50A Max. 2181.00 100 WATT .1/5/10/25/50/100r250/500/11if1/1.5k0/2.550/3.5k0 15KVA 75A Max. £275.00 £9.50 + 75p p&p (211.78 inc. VAT). 4h 40 watt £10.44 1212.00 inc. VAT) Black Silver Skirted Knob calibrated in Nos 1-9, 11/2in dia brass bush. 211 20 wan 0.44 + £1.25 p&p (0.99 inc. VAT) 3-PHASE VARIABLE VOLTAGE TRANSFORMERS Ideal for above Rheostas 30p ea. + VAT. 18in. 15 watt £500 a 75p p&p atm inc. VAT) Dual input 200-240V or 380-415V. Star connected 13in. 10 wan 000 + 75p p&p 1(5.46 inc. VAT) 3KVA 5arnp per phase max. £113.40 All V.V.Ts INSULATED TESTERS NE W! 12in. 8 wan 01.60 + 50p p&p 24.71 inc. VAT/ 6KVA lOarnp per phase max. £170.10 plus carriage Test to I.E.E. Spec. Rugged metal construction 9in. 6 wan £3.00 + 50p p&p 124.02 inc. VAT) 10KVA 16amp per phase max. £345.45 and VAT suitable for bench or field work onstant speed 6in. 4 watt 2100 + 50p p&p (24.02 inc VAT) Comprehensive range of TRANSFORMERS L.T. ISOLATION & AUTO clutch. Size L 8in., W din., H 6in. weight 61b. 230V AC Ballast Kit for either 6in, gin or 12in tubes £5.50 p&p 55p 1110-240V). Either cased with American socket and mains lead or 500V. 300 megohrns. £49 p&p (2 1258.65 incl. 1(6.96 inc. VAT). open frame type available for immediate delivery. Leaflet on request. VAT). 10000 1000M0 255 + p&p E21265.55 incl. For 13in. & 18in. Tubes £6 p&p 75p (27.76 inc. VAT). 1,-/ite VAT) SAE for leaflet. For 12V DC op. 12in. & 13in. tubes only £5.50 p&p 75p 1E7.18 inc. 12V D.C. BILGE PUMPS 400 G.P.H. 15th. head, 3arnp, £8.00 + £1.00 p&p VAT). SPECIAL OFFER! 175 WATT SELF-BALLASTED BLACK UGHT MERCURY BULBS. (210.35 inc. VAT). AUTO TRANSFORMER tapped 90-260V. 3.5KVA 1 phase totally enclosed in metal Available for either B.C. or ES, fitting, price £10.80 + p&p (1.25 (total 700 G.P.H. 10ft. head, 3.5amp, £11.50 + (1.50 p&p case, ml Woden. Price, MOO + carriage at cost + VAT. N.MS. inc. VAT 213.851. 2I4.95 inc. VAT). 4, " 1750 G.P.H. 15ft. head, 9amp, 215.00. 4' 21.75 p&p - GEARED MOTORS LT. TRANSFORMERS 5 rpm 2401 AC MI. by Carter, MS El p&p 10.11 inc. VAT). NBAS. (219.26 inc. VAT). "Special Offer" 0-6.3V-0-6.3V at 10 Amp (12V 0 10 Amp or 6V at 20 20 rpm 115V AC Synchronous, torque approx. 8015/in, 220.00 + £4 p&p (Total inc. SINGLE DIAPHRAGM COMPRESSOR NMS 5 t I Amp) Price £9.00 p&p (2.00- inclusive of VAT £12.65 N.M.S. VAT f27.60). N.M.S. Max. 20P51. One CFM approx. 240 volts AL. £18 + £2 p&p (223 Inc. VAT) TRANSFORMER 240V operation, £9.15 + £2.00 p&p (Total inc. VAT £12112). 20 rpm Torque 201b.m. reversible 1/80th he. 1196 AC. Pnce, 0.50 + p&p £1.80 ROBOT ENTHUSIASTS EPROM ERASURE KIT The following two Motors are ideally suited for experimenters in (Total inc. VAT 212.991 Why waste money? Build your own EPROM ERASURE for a Suitable TRANSFORMER for 230-240V AC operation. Price, £5.20 A- p&p 2).40 this field: fraction of the price of a made-up unit. Complete kit of parts less 1. ESCAP precision Swiss-made ironless rotor, 6V DC geared (Total inc. VAT E7.59). N MS. 31.3 rpm GEARED MOTOR, Torque 351b in reversible I I5V AC inc start capacity. MOtor with 70-1 gearbox. 6V DC - 16 r.p.m. 3V -0 r.p.m. amazing case to include 12,8 wan 2537 Angst. Tube. Ballast unit, pair of hi-pill leads. Neon indicator, safety microswitch, on/off switch Price: £1155 + p&p Motel inc. VAT 05.581 N.M.S. power; no load current; only 10 ma. approx. Size: 4 x 21/2 cm. Ex- Suitable TRANSFORMER 230V AC operation Price £450 + 50p p&p ITotal inc equiprnent, tested and guaranteed. ONLY £4.50 + 50p p&p (total and circuit. LESS CASE: Price £13.60 + 75p p&p (Total inc. VAT £16.50). VAT 25.751. inc. VAT 0.75). Warning: Tube used in this circuit is highly dangerous to the CRONIN 37 rpm 2001.0 Jr, approx. 110V AC, reversible geated motor. Price: 05 2. 12/24V D.C. Reversible Precision built motor manufactured by Escap - will operate from 24V down to 2V DC - Current consump- eyes. Unit must be fined in suitable case. p&p £4.50 1E4502 inc VAT). N.MS. tion negligible. A range of speeds between 2 to 36 r.p.m. Suitable TRANSFORMER for above £10 p&p 21501E1322 inc. VAT). obtainable: 6 Volt DC-9 r.p.m. N/16 MA, 12V DC -18 r.p.m. N/L 10 SOLID STATE E.H.T. UNIT 57 rpm 240V 1/22 he continuously rated REVERSIBLE 50Ib in. manut by MA, 24V DC - 36 r.p.m. N/L 18 MA. Total length of motor and Input 230V A.C. Approx. 15KV. Producing 10mm spark. Built-in 10 sec Wynstruments. New. Ideal for garage doors, curtains etc. ONLY £12.00 a 0.00 gearbox 90 NVM. Max. Dia 42 M/N1. Shah length 15 M/M. Shaft Dia timer. Easily modified for 20 sec, 30 sec, to continuous. Designed for p&p (mnd. VAT £1610), inclusive capacitor. 6 M/M. Approx. half manufacturers price: £15.00 p&p (2.00- total boiler ignition. Dozens of uses in the field of physics and electronics, 71 rpm Torque 10Ib in. reversible 1/751, h p. 1100 AC motor. Price £9.50 + 0 80 e.g. supplying neon or argon tubes etc. £650 + 90p p&p frota( inc. inclusive of VAT £19.55. PAP (Total inc. VAT £12.991. VAT 0.50) N.M.S. Suitable TRANSFORMER for 230-240V AC operation. Price - £520 + p&p (1.40 VBL4 CENTRIFUGAL BLOWER (Total inc. VAT 27.591. N.M.S 240V AC powerful 1/50 h.p..23A motor. 218,00 + (2.00 p&P (Total inc. FROM STOCK AT PRICES 24V DC 200 gmi 101b/in, MI by either Parvalux or Cater. Ex-equip tested MOO + VAT £23.00). N.M.S. 0 50 p&p (Total inc. VAT 00931. 12/24V DC Centrifugal Blower £7.50 + £1.00 p&p (Total inc. VAT THAT DEFY COMPETITION 730/240V AC SYNCHRONOUS, 2 rpm, 6 rpm, 6 rev per day Any type. 0.111 + 50p 29.781 N.M.S. AC GEARED MOTORS C.F. BLOWERS p&p (Total inc. VAT £510). DC MOTORS AC CAPACITORS CHECK METER MICROS WITCHES STROBE KITS 200-24011 AC. Stamp, fully reconditioned. 050 + 21.75 p&p (Total inc. VAT EXTRACTOR FAN COOUNG or RELAYS FLASHTUBES 210.641 Ouiet smooth ru nn ing. Size 43/4 x 43/4 x 11/2. Supplied for 240V ac. operation. Price 24.75 + 21 p&p (Total REED SWITCHES CONTACTORS SANGA MO WESTON TIME SWITCH inc. VAT £6.62) N.M.S. SOLENOIDS AL. or D.C. SYNCHRONOUS Type S251 200/250 AC.) on/2 off every 24 hours, 20 amps contacts with override PROGRAMME TIMERS MOTORS switch. Dimaeter 4" x3". Price 131.50 + £150 p&p 1(12.65 inc. VAT & p&p). Also available with solar dm RAT Other types available from stock 240V A.G. SOLENOID VALVE WIDE RANGE OF XENON TUBES N.M.S. New Manufacturers' Surplus Designed for Air/Gas at 0.7. Water 5 psi. Inlet-outlet 343. Forged brass WRITE/PHONE IN YOUR ENQUIRIES R&T Reconditioned and tested body. Manuf. Dewraswitch Asco. PRice £5.50 + El p&p (E7.48 inc. Goods normally despatched within 7 days. VAT) N.M.S.

Ample parking space SERVICE -r RADING CO Personal callers only. Open Saturdays Showroom open 57 BRIDGMAN ROAD, CHISWICK, LONDON W4 5BB. Tel: 01-995 1560 9 Little Newport StreetLondon WC2H 7JJ Monday-Friday ACCOUNT CUSTOMERS MIN. ORDER £10 Tel: 01-437 0576

MARCO TRADING

RESISTOR KITS 74LS DIODES LINEAR IC's TRANSISTORS 29p 1.80 LSOO 13E338 0.38 N916 0.04 44119 0.12 CA3011 1/4W Pack 10 each value E12 10R-1M AG128 30p LS01 28p BFX28 0.28 N4001 0.05 AAI29 0.18 CA3012 1.75 Total: 610 resistors ONLY £4.48 AC176 28p 28p BFX84 0.24 N4004 0.06 AAY30 0.16 CA3014 2.38 1.502 AF239 ' 68p /14 W Pack 5 each value E12 10R-1M 0.06 BAI 00 0.24 LSO3 28p BC107 0.10 BFX85 0.26 N4005 CA3018 1.10 0.26 N4007 0.07 BY126 0.12 Total: 305 resistors ONLY £2.75 32p BC108 0.10 BFX87 CA3020 2.10 LSO3 N4148 0.05 BY127 0.10 /12 W Pack 10 each value E12 2R2-2M2 8C109 0.10 BFY50 0.21 CA3028A 1.30 LS013 28p EIFY52 0.21 N4149 0.06 BY133 0.16 A.B.C. 0.12 CA3035 2.55 Total: 730 resistors ONLY £5.25 LSO9 28p VFY90 0.90 N5400 0.12 BY184 0.40 BC147 0.09 CA3080E 1.80 V2W Pack 5 each value E12 2R2-2M2 LS10 28p BSX20 0.34 N5401 0.15 0A47 0.10 BC182 0.09 CA3085 1.20 N5402 0.15 0A90 0.08 Total: 300 resistors ONLY £3.50 LS11 28p BC182L 0.09 BU208 1.55 0.16 0491 0.09 CA3086 0.68 25p BC184 0.09 BU407 1.65 N5404 LSI2 N5406 0.18 0/195 0.18 CA3090A0 5.00 33p BC184L 0.09 MJ2955 0.90 SOLDERING AIDS TELECOM EQUIP LS13 N5408 0.20 04200 0.06 CA3130E 140 BC212 0.09 0C45 0.58 Antex 1 5Wiron 5.00 BT Plug & 3M lead 2925 LS14 58p S44 0.06 0A202 0.15 CA3140E 0.60 BC212L 0.09 0071 0.50 Antex 18Wiron 5.00 BT Master Socket 22.85 LS15 25p 0.52 S921 0.08 IN914 0.04 HAI336W 3.15 BCY70 0.15 0072 Aetna 25Wiron 5.20 BT Sec Skt 21.95 LS20 28p TIP31A 0.44 LM324N 0.55 15p/M, B0131/2 0.34 Aetna Elements 2.00 OT 4-core cable LS21 28p TIP32A 0.02 MIN.D CONNECTORS LM339 0.65 0.95 £12.00/100M 00133 0.56 Antex Bits LS22 28p TIP33C 0.88 LM348 0.90 150 BD135 0.32 9 15 25 37 Antes stands LS30 33p TIP34A 0.72 4.50 BDI36 0.36 PLUGS way way way way LM380 1.65 Desolder Tool 28p 7IP2955 0.60 LS32 8E115 0.32 Solder Lug 52p 65p 811p £1.45 LM381N 1.45 Spare nozzle 0.45 ROTARY POTS 71P3055 0.60 LS37 23p 8E184 0.32 Right Angle 89p £1.34 £1.98 £3.48 LM382N 1.45 25W Kit-iron with 13A plug & 71543 0.88 0.25W Carbon Log & LIN 1K-2M2 LS74 38p 8E185 0.32 SOCKETS LM386 0.95 stand ONLY £6.20 71588 0.40 32p ea. 23/10. LS122 70p 8E194 0.08 Solder Lug 78p 98p £1.33 £2.48 LM387 1.45 2N3055 0.45 Any 100/228.00 LS138 45p 8E195 0.10 Right Angle £1.18 £1.78 22.70 £4.15 NI -CAD CHARGER 0.68 LM389N 1.20 8E196 0.10 2SC1096 95p 95p 98p £1.00 LS139 68p COVERS LM3914N 2.55 Universal charger to charge PP3 6E197 0.10 2SC1173Y 0.82 LSI51 75p 0.92 LM3915N 2.60 AA C. D. PRICE: 0.00 6E200 0.20 25C1306 V E R OBO A RD LS155 50p C-MOS ML23213 2.10 0.20 2SC1307 0.40 8E224 2122 x 31/4 8Sp LS157 45p 2SC1957 0.76 4000 24p 4021 513p 40364 2.75 555 0.35 NI -CADS 8E244 0.26 21.00 LS158 58p 4038 7Sp C-moss555 0.88 21/2 v5 0.28 2SC2028 0.73 4001 24p 4022 96p 3 4.45, 4/16.00 0F244A 21/2 x 17 23.07 LS160 60p 2SC2029 2.10 4002 25p 4023 35p 40394 2.80 741 0.25 0.95, 10/8.00 BF244B 0.30 AA 31/40 17 21.06 50p 4040 60p SAS560S 1.85 LS161 70p 6E259 0.32 2SC2078 1.05 4007 250 4024 HP11 2.30, 4/950 31/4 x 15 21.15 72p 2SC2166 1.20 4011 24p 4025 24p 4042 50p SAS5705 1.85 2.35, 4/8.75 L5162 13E262 0.30 33/4 + 17 24.10 3SK88 0.65 4012 24p 4027 45p 4043 42p SL901B 5.20 IS 163 80p 6E263 0.30 43/4 x 17 3/4 24.95 40673 0.80 4013 56p 4028 45p 4044 50p SL917B 6.25 LS166 1.95 8E337 0.38 VOLTAGE Pkt 01 100 pins 50p 4014 60p 4029 75p 4046 60p TA7205AP 1.50 LS170 1.75 REGULATORS Spt facecutter 21.48 4015 60p 4030 35p 4049 38p TA7222P 2.12 LS244 1.00 2.90 78L05/12/15 30p Pin Insert. tool 21.85 4016 40p 0031 1.30 4050 36p TDA1004 LS245 250 55p Vero Wiring Pen & Spool 23.50 4033 1.25 4051 70p TL072 98p 7805/12/15 MICRO 280ACTC 3.30 4017 60p 1.5257 73p 68p 7905/12/15 65p Dip Board 23.85 764250n/s 4018 60p 4034 1.46 4052 60p TL081 5.80 ZBOADMA 9.00 23.50 Vero Strip 21.25 LS393 1.15 4020 85p 4035 70p 4053 60p TL084 1.28 LM317K Z8OACPU 3.70 280APIO 3.40

ORDERIN G: A) components are brand new and to full specification. 1985 CATALOG UE MARCO TRADING (DEPT PE2) Please add 45p postage/packing (unless otherwise specified) to all orders Our latest 123 page cata- then add 15% VAT to the total. Either send cheque/cash/postal order or logue over 4000 items The Maltings send/telephone your Access or Visa number. Official orders born fully illustrated. Send 65p schools, universities, colleges etc most welco me now for your copy. FREE High Street (Do not forget to send for our 1984 catalogue - only 65p per copy.) withorders over £5.00 Wem, Shropshire SY4 5EN Al) orders despatched by return of mail NE W RETAIL 1000 squ ft shop now open Mon-Fri 9005.00. Sat 9-12.00. Tel: 0939 32763 Telex: 35565

Practical Electronics February 1985 46 all in your M A RC H issue! M TV' BBC SPEC CH SYNTHESISER One of the best BBC projects yet, giving effective speech synthesis for less than fifteen pounds.

This is to be a new regular item for BBC Micro enthusiasts. The page may be viewed as an I/O port configured for bidirectional operation because we invite you, the reader, to contribute your hints and dis- coveries. It promises to be an exciting page with the aim of making an important contribution to understanding the BBC machine. You have one month to prepare for the interface. So order your copy from your Newsagent now! MOND If you're interest is in the sports, training or medical field then you'll always need to measure pulse/heart beats. This instrument will monitor heart beats from 40 to 200 beats per minute to an accuracy of within 1 beat per minute and display the result on an I.e.d. display.

e— T h fl -SPECIAL lifffill

P R A C TIC AL ELECTRONICS R O B OTIC S - MI C R O S - ELE CT R O NIC S- INTE RF A CIN G M ARCH 1985 ISSUE ON SALE FRIDAY, FEBRUARY 1

Practical Electronics February 1985 47 FREE! READERS' ADVERTISE MENT.SERVICE RULES Maximum of 16 words plus address and/or phone no. PE Private advertisers only (trade or business ads, can be placed in our classified columns). Items related to electronics only. No compute,- software. PE cannot accept responsibility for the accuracy of ads, or for any transaction arising between readers as a result of a free ad We reserve the right to refuse advertisements. Each ad, must he accompanied by a cut-out valid "date corner". Ads. will not appear (or be returned) if these rules are broken.

W ANTED service manual or circuit for Cossor TELEPRINTERS Creed 713, 54R and 54N. Also £99 each. Acron DES £80. Tel: 01-892 1909. 1049 MK4 'scope, to borrow or buy please. J. two C37 and J37 tape recorders. Offers invited , M ONO valve amplifier, 3 watt, and motor, in Rudrum, 2 Princes Road, Eastbourne, Sussex or why? Mr. John Radley, 81 Drayton Avenue, portable timber cabinet. Two available. £10 each BN23 6HG. Tel: Eastbourne (0323) 29440. West Ealing, London W13 OLE. Tel: 01-997 if collected. Tel: Oxford (08651779855. W ANTED Watford Ultimum system any condi- 4835. AVAILABLE B0139-14.0, BC146 Micro TA tion. Phone Burntwood (05436) 6043 SYNTHESISER, 4600, mostly working (not 7806, 09 and 12 vol. reg.s all new for less than evenings-ask for Steve. completely finished). Large wooden case. Inter- half price + p&p. Write to: Saied Z. Fathy, No. W ANTED MCP40, Tandy or similar graphics nal amps/speakers. Large patchboard £180. Mr. 25, Alric Avenue, Neasden, London NW10. printer and Thandar PFM200A frequency meter Gaskell. Tel: Cambridge (0223) 893593. FOUR mains PCB relays type 265/4A/G2v. or similar. Cheapish please! Dr. Andrew Brown, SAFGAN 12 MHz dual beam oscilloscope, un- D.P.C.O. £5 or £1.40 each including postage. Department of Oral Surgery, John Radcliffe used, as new conditon, with manual and X10 David White. Tel: 0248 722697 (evenings). Hospital, Oxford 0X3 9DU. Tel: Oxford (0865) probe set £150. Peter Cunningham, 11 Berwyn 'NIGHTRIDER' car lights sequencers, drives 65164. Avenue, Penyffordd, Nr. Chester, Tel: Caergwrle nine channels van-speed. Easy wiring all 280A computer system including 10MB 760172. negative-ground cars £40 complete. Mr. S. M. Winchester back-up cartridge drive. Can be seen FOR sale PE August 1977 to October 1983. ETI Budzinski, 16 Laburnum House, Malpas Road, working. £170 or split. Tel: 0223 277272. February 1978 to March 1982. Offers to: R. M. London SE4 1BL. DISCS! DD/SS £1.35. DD/DS for SS drives James, Yew Tree House, Preston Wynne, OSCILLOSCOPE Heath 10-4555 £150 ono £1.45. Disc boxes: 50 disc £8, 10 disc £1.95. Hereford H R 1 3PE. also other instruments P.C. bridge etc. Offers, Martin Harlow, 194 Old Woking Road, Woking, W ANTED high resolution graphic board for good condition, sold separately. Mr. A. Ewing, 9 Surrey GU22 8H R. UK101 (Sprite from Premier). J. Ockier, Mgr. Croft Crescent, Markinch, Glenrothes, Fife KY7 FLUKE 8000A DMM £40, p.s.u. and many un- Christiaensstraat 16, 8880-Tielt, Belgium. 6EH, Scotland. used i.c.'s and components. For more informa- 300 watt switched mode PSU. Set to 60 amps W ANTE D AY-3-1270 linear i.e. or tion send SAE. Mr. T. Pomphrey, 347 Church 5 volts. 6" x 5" x 14". Diagrams available. Mr. RS-3-1270. Mr. J. F. Wilso, 233 Broomlee Road, Redfield, Bristol BS5 8AA. Tel: 0272 P. Kirton, 4 The Grove, Shaw Heath, Stockport, Close, Newton Aycliffe, Co. Durham. Tel: Aycliffe 558980. Greater Manchester SK2 6QU. Tel: 061 480 312130. PYE 'Westminster' 70cm TX/AX fitted 5 4690. W ANTED two track record head for B & 0 repeater channels +2 Simplex, 15W TX 0/P, TECHTRONICS 515A 15MHz single beam record 1800 RTOR deck. Mr. C. Bressington, 17 tone burst. £75. D. C. Chapman, 6 Pickhurst oscilloscope £50. Advance SG66 audio Station Road, Ystrad Mynach, Mid-Glamorgan. Green, Hayes, Bromley, Kent. Tel: 01-462 2178. generator £40. Eddystone 830 Receiver £95. Tel: 0443 813005. 4.8K ZX Spectrum and full size keyboard now Tel: Peterborough 235042. EIGHT Philips LVC 150 2÷hr. video tapes. Har- fails to output logo when switched on £40. Ralph TELEQUIP MENT double beam oscilloscope dly used. Offers plus postage. Mr. L. T. Hill, 14 Lovelock, 14 Knightley Road, Exeter EX2 4SR. model D43. Full working order. Also instruction Rothesay Terrace, Bedlington, Northumberland. Tel: Exeter 75892. manual. £60. Buyer collects. Mr. Naylor, 26 Tel: Bedlington 825967. W ANTED, loan or purchase, handbook/service Highfield Road, Stretford, Manchester M32 819F. W ANTED data or specimens of early transistor sheets Waltham music centre STM 50 or Tel: 061 8654320. types. Good prices paid. Write for full details: Mr. photostat. Costs paid. Mr. W. Hammond-Haley, PE November 64 to December 81 less five. Andrew Wylie, 18 Rue de Lausanne, 1201 Sleaford Road, Dunston, Lincoln , Some extras. Plus most 82-83. All mint. Offers. Geneva, Switzerland. LN4 2EZ. Tel: Metheringham (0526) 20661. 4 Phil Simpson, 37 Larkholme Parade, Fleetwood MICROSYNTH Synthesiser built and tested PE Quasar cassette deck, not working, £15 FY7 8LL, Tel: 03917 6317. with speakers and homemade stand £150. 8 ZX81, 16K Ram, tapes £35, two unused TDM W ANTED PE December 1975 or copy of Stourton Road, Witham, Essex. Tel: Witham 1010's £5. Mr. J. C. D. Darwent. Tel: Dronfield Minimix item from that issue. Call weekday even- 514556. 413667. ings only. John Colson 01-2533176. CO MPONENTS transistors mainly OC/AC/BC, UK101 with Cegmon and 8" disk system. Needs PRACTICAL Electronics from 1967 to 1983. capacitors, resistors, chips, pots, relays, motors memory expansion. £200 or best offer. Mr. S. Instruction manual for Tektronics 5458 and other. 16 lb. £20. Mr. Turner, 4 Mill Fields, Morgan, 17 Willenhall Road, Bilston, West oscilloscope. Offers. Buyer collects. Mr. L. T. Newtown, Powys. Tel: 0686 27862. Midlands WV14 6NW. Tel: Bilston 403416. Cowell, 69 Crew Road, Haslington, Crewe, W ANTED service circuit diagrams Sugden C51 TEXAS TI-53 17 months old, working, £7. L. Cheshire. Tel: 0270 581157. A51 purchase hire to copy. Good price paid. Stewart, 32 Cross House, Wolverhampton WY2 RANGER P.E.C.B. two for sale working order. Richards, Maesyffnnon, Caehopkin Road, Aber- 3EX. Offers invited.' Will separate if required, 27MHz crave, Swansea. Tel: 0639 730629. W ANTED PE January, March, April 1984; July legal. Mr. G. T. McDermid, 4 Aspian Drive, Cox- 10 x 8255A £70 the lot or £8 each. Also printer 1983, April 1980, February 1978 and all before heath, Maidstone, Kent ME17 4JZ. Tel: 0622 leads for Dragon 32, BBC £9.95 each. R. July 1977, Kenny Robertson, 82 Willow Drive, 46354 (evenings). Vowles, 3 Orchard Waye, Uxbridge, Middx, Airdrie, Lanarkshire, Scotland M L6 8JX. TANDON disc drive D/S D/D 80 track 640k UB8 28N. Tel: 0895 54720.

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Signature Date Please read the RULES then write your advertisement here - one word to each box. Add your name, address and/or phone no. Name & Address: COUP O N VALID FOR POSTIN G BEF ORE 1 FEBRU ARY 198S (One month later for overseas readers.)

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494 4P .*

1444 Practical Electronics February 1985 RICHARD B. H. BECKER SYSTEM DESIGN AND MECHANICAL ENGINEERING.

TIM ORR COMPUTER INTERFACE AND CONTROL ELECTRONICS. ROBOT /h.4111M11\111111II\ A = SA W M r U M M I = M r an ••••• 1 =• • V E MINNI d men or ME M . = = ,•••• t,

HE ELECTRO-MECHANICS and the electron ics of both ro bots Thave now been explained in previous parts, and the p.c.b.s and parts lists have been published. The actual construction and PART SIX computer control of the robots is the last thing to be considered, beginning this month with NEPTUNE.

CONSTRUCTION Construction starts with axis 0 and progresses upwards from Onto mounting rings on axis 1 cylinder the lower arms are fit- there. The hydraulic cylinders of the NEPTUNE are supplied ted and to the upper end of these are fitted axis 2 cylinder with pre-assembled. First axis 0 cylinder is fitted to its sensor poten- the upper arms attached to it (Fig. 6.3). To the end of the upper tiometer, on a bracket beneath it, and then to the base plate and arms is fitted axis 3 cylinder which provides the wrist raising front plate (Fig. 6.1). There are support brackets to ensure a function. rigid structure and there are triangular brackets with feet on A pair of mounting plates is used to secure axis 4 cylinder to them to prevent the robot from tipping over when under load. the front end of axis 3 cylinder (Fig. 6.4). This applies to NEP- The top slot in the rear plate is for fitting the computer interface TUNE H only, where it provides wrist yaw, a function immen- leads to the edge connectors on the interface board. The slot sely useful when picking up objects lying flat or in other difficult beneath it is for the cables leading to the power supply which fit positions. It also greatly assists spraying into corners. Yaw is a onto the rear plate later. feature usually found on only. the most expensive of robots used Next the top plate is fitted. Being 3mm steel this is quite in industry. Axis 5, the wrist rotation cylinder fits to the axle of heavy but this is necessary to ensure rigidity. On top of axis 0 axis 4 cylinder by means of a short plate. On NEPTUNE I cylinder goes the shoulder rotating axle with axis 1 mounting where there is no wrist yaw, axis 5 fits to the top of axis 3 cylin- plate on top of it (Fig. 6.2). The weight of the arm is carried by a der. The gripper clamps onto the axle of axis 5 cylinder with a large thrust ball race fitted round the axle. Through the axle single set screw enabling it to be rapidly changed. The NEP- passes the plumbing/wiring harness which is secured to axis 1 TUNES are supplied with a choice of gripper types. The robot is cylinder fitted to the mounting plate. now ready for plumbling and wiring.

Fig. 6.1. (above): base plate and axis 0 cylinder

Fig. 6.2. (opposite): shoulder-rotating axle with axis 1 cylinder fitted to the mounting plate

Practical Electronics February 1985 49

It The harness is strapped onto the arms at the fixing holes with again are made with "banjo" push-on fittings and hollow bolts. cable ties. The position for these is marked, with dabs of paint, After wiring up the power supply (Fig. 6.9) and connecting to on the harness. The pipes press into 'banjo' fittings attached to the computer interface board (no need to connect to a computer the cylinder ends with Delrin hollow bolts and the cables are yet) the system is ready for commissioning. The sump of the trimmed and soldered to the sensor potentiometers (Fig. 6.5). hydraulic power pack is filled with water and the pump is The solenoid operated valves, which control the water flow, operated with its outlet and inlet connected together with one of fit with hollow bolts to a Delrin manifold (Fig. 6.6) which acts the plug-in pipes. This expels the air from the pipe which, after like a printed circuit board routing the water to the correct valve. switching off the pump, is plugged into the manifold as the The other end of the valves fit to bored Delrin bars to which the pressure source; the return pipe is taken from the outlet of the restrictors and flow rate control valves also fit (Fig. 6.7). manifold to the sump. After pressurising the system and check- Brackets to which the solenoid driver boards will fit are screwed ing that there are no leaks the axes are tested one at a time by to the solenoids and ensure correct alignment for the boards plugging in a solenoid driver board and the axis operated by which clip onto the connector tags of the solenoids (Fig. 6.8). means of a potentiometer on C N401 extend-contract connector. This arrangement avoids soldering to the solenoids and greatly This will drive out most of the air. The rest of it will gradually simplifies maintenance in that the boards can be rapidly un- disappear by dissolving in the water when under pressure. It plugged from the system. Connections to the plumbing harness then comes out of solution when returned to the sump.

Fig. 6.4. Shoulder, upper arm and wrist assembly

Fig. 6.3. Lower and upper arms fitted

Hydraulic cylinder assembly Fig. 6.5. Plu mbing and wiring loom

50 Practical Electronics February 1985 All the solenoid driver boards may now be fitted (Fig. 6.10), the computer interface board connected to the computer and the "NEPDYN" program run. This sends and returns the chosen axis between 2 points and generates, on the monitor screen, a graph of error in the axis position against time. The error is the difference between where the axis is, as measured by the ADC, and where the axis has been told to go. With the aid of this program the restrictors are set to achieve rapid convergence of Fig. 6.6. Hydraulic control manifold the send and return graphs without any overshooting. After setting the restrictors of each axis, the pre-sets on the solenoid driver boards are set so that sending position 0 from the computer, by means of the "NEPTROL" program, sends each axis to just before the end of its travel. The pre-sets on the interface board are set to match the positions of the simulator (Fig. 6.11) with the positions of the robot. The interface board is next mounted over the manifold assembly (Fig. 6.12) which is then slid into the robot base and bolted down. Following fitting of side plates and covers the robot is then ready for use.

OPERATION OF THE ROBOT Operating the robot basically consists of using POKE and PEEK instructions sent to the robot as if it were part of the memory of the computer. To move axis 0 of the NEPTUNE II

Fig. 6.7. Assembly sho wing restrictors and flow-rate control valves

Fig. 6.8. Completed hydraulic flow-control sub-system for all seven axes

Fig. 6.10. All sub-assemblies completed and wired up for testing

Fig. 6.9. Power supply Fig. 6.11. NEPTU NE simulator arm

Practical Electronics February 1985 to position DO, the start of the 'memory' is first defined. This is Fig. 6.12. Control and servo also the address for the most significant byte of axis 0. The least electronics ready for installa- significant byte is at the next address. On the BBC, POKE and tion in robot base PEEK are represented by `?' and hexadecimal numbers are indicated by `&'.

10 A=8cFC00 20 ?A=DO DIV 16 30 ?(A+1)---(DO MOD 16)*16

The data DO can be any integer from 0 to 4095 (2 12-1) because it is a 12-bit control system. On the NEPTUNE lit is an 8-bit 1111111111111111111111111111110111111111111111111111111111111 system so the range is 0 to 255 (28-1) so only one byte is sent tylIMPrimpormieserigrorimmis, for each axis move. For the msb the data is divided by 16 and the remainder ignored. For the lsb this remainder is multiplied oas000iwsooretbo°• ••• ,+•• • , , • by 16 because it is the top 4 bits of the lsb that are used. The addresses of the axes follow successively so to move axis 4 to position D4 the instructions are as below. Similarly for axis 4 40 ?(A+8)=-D4 DIV 16 50 ?(A+9)=(D4 MOD 16)*16 120 ?(A+14)=132 Similarly for axis 5 130 ?(A+14)=4 140 ?(A + 14)=132 60 ?(A+10)=D5 DIV 16 150 DA4=?(A+17)*16+?(A+16)/16 70 ?(A+11)=(D5 MOD 16)*16 Reading the simulator is performed similarly but at the mul- The servo system of the robot then makes the axis go to this tiplexer axis address 8 bits higher so to read simulator axis 0: position with no further computer intervention but with the ADC the position of the axis can be followed as it is moving. To 160 ?(A+14)--136 operate the ADC it is written to at A+14. Data bit 7 is toggled 170 ?(A + 14)=8 180 ?(A+14)=136 and the multiplexer axis address set up. The axis address is in the bottom 4 data lines (see Table 1 October 1984). Axis 0 is at 190 DS0.----?(A+17)*16+?(A+16)/16 address 0000. The msb is read at A+17 and the lsb at A +16. If the simulator is constantly read and the data returned to the 80 ?(A+14)=128 robot then the robot will follow the movement of the simulator. 90 ?(A + 14)=0 100 ?(A+14)=-128 NEXT MONTH: details of the assembly and use of 110 DA0=?(A+17)*16+?(A+16)/16 MENTOR.

The complete NEPTU NE 2 robot system, sho wing the pump, computer and monitor, and the simulator

Practical Electronics February 1985 Don't put it off any longer!

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04,17 0.090 B0Y70 0.160 BU111 I 400 30A530 0.750 2437770150 JAPANESE P0085 0.420 LED A8119 0.090 BCY71 0103 BUM 0.700 18A540 0.750 29 37720.900 TRANSISTORS PU80 Otto LED Orr, 0/0/32 0.090 BCY72 0160 8004 0.750 113/1560 0 700 25 37731.000 20473 0.300 P07200 1 350 RED 0.050 AC107 0.280 82115 0.260 E10205 0.700 18A800 0.350 25 40310250 204104 0.320 PCf801 1100 00126 0170 130124P 0.500 130208 0 750 18,181030.600 2510360.250 23A198 0.220 000802 0 570 LED One AC127 0150 B0124 13013 1302084 0.800 1841320 0.750 2N 40370250 234203 0.300 P00806 1150 YELLOW 0.100 00128 0.150 50128 0150 11U20(10 1.200 114920 0.800 ON 44430.760 PC6200 1 000 Ilk /11411k11M Mak 4111 234473 0.370 LEO 3mris - -- . ------og. mil 401280 0.230 130131 0150 80326 0 8511 784950 0.800 ON 44440.760 25054 0.250 PCL81 0.540 GREEN 0 100 - - AC14111 0.230 80132 0.250 50406 0.850 18/1990 0.800 ON 50610.200 20877 O 2,0 PL519 Otto ...: E.,= . _• -.. -. --._ - m Fz- . -- •_ -... 7- • 401426 0.220 130135 0.200 90407 0 750 TC4800 0.800 25 52940.300 258337 1.200 PCL132 0 630 LEO 5risKs = m-ii km AC1538 0.230 82136 0200 00408 1.000 10A9411 0.850 25 52960.300 200105 0200 PCL84 Otto RED 0.050 00176 0.180 110137 0.200 00500 1120 10407700 000 ON 6106 0.400 2SC460 0.210 POLES 0.550 for low-cost training in 4017611 0.200 B0138 0.200 B0526 0.800 10014120.600 19 8107 0.400 200400 m o P0086 0 550 LEO 5mm 00187 0.150 80139 0200. BY126 0.060 10020020 8010 214 6109 0.400 YELLOW 0.101 200733 0.400 PCI.805 0 550 401876 0.200 00140 0200 03127 0 080 30620031 500 500300200 00.850 0 0 40780 0.170 80144 0.900 BY133 0.010 TOA20201 400 3N 128 0 550 2301161 1.100 LED 5mm 2SC1172Y 1500 P ACIIIIIK 0.230 05143 0.650 GREEN S IN real-life robotics BD150 0300 87164 0.220 70/20301.400 20s09 ,027.907 020400 04 500 40418 0.480 BD157 0.3110 BYI76 0150 MA25220.800 P0008 7000 N 914 0 020 00119 0160 80158 0.380 50179 0.350 10A25300 800 • pyg, 0.700 Inc advanced design 09 57 Neptune 2 makes a the lowest cost real-lie 2301307 1 000 _. 0 p .0 00142 0 600 130166 0.300 00182 0 320 10425320 750 N 4001 0.040 industrial robot .320 N 4002 0 040 25015200.250 Kre 40749 0.450 80175 0.300 B0184 0 TOA25400 700 P05000 1.600 77 ,0 electro-hydraulically powered. using a revolutsonary water based , .5 4.00 34 0 040 2500216299 11001 0 BRIDGE 40767 0.220 80177 0.300 07187 0.320 10425600 700 system no messy hydraulic 01111 ...... 00152 0.220 00179 0 320 6Y196 0200. 10A25930.800 RECTIFIERS .110 20020781 200 It performs? servo-controlled axis movements (ti on Neptune 1) - more 01124 0.250 961181 0.450 01206 0 N 4005 0.040 14050Y 0 150 than any Other robot under E 10.000 4025 0.250 13E1201 0.300 05207 0.110 72426900 700 N 3020 0•040 2E2 02'0 2 1 30000 8 1/01000 0180 01726 0.250 00202 0.180 94223 0320 fle29 0.150 N 4007 0.060 40060/ 1472004 0 190 its program length is limited only by the memory of your computer. N 414, 0 020 20 234 0 370 41127 0250 82203 0.420 PA 10 0150 TIP294 0 220 0 . BZYB8 Range 10740040 210 Think what that can do for your BASIC programming skills! N 5100 0 090 254135 4000 2•710 30/0 060 14/60000.230 0139 0.220 130204 0.420 71P29C 0.250 64113712 1 500 01239 0.220 02223223 0.310 0A270 0.400 71P30 0160 95407 0.100 7300 Zeners 1A/8000 0.280 And it's British designed. British made. N 5402 0100 147205 1.500 00112 0.700 132225 0310 0A3086 0 .250 Tip31A 0.240 82061 Range 2400000 350 N 5403 0,110 UP05 75 1.000 24720000 360 00113 0 .800 00232 0110 CA 3089 1.500 11P32 0.240 20 70 3040730 ogler lemurs novae 05215 1.000 130237 0210 003240 0.900 OP320 0.240 N 5404 0,780 2,040040 420 Leakproof. hiCUOniesS roiling diaphragm seMs 05017 1000 80238 0.240 01060 0.230 71533 0.500 N 0405 1.120 2u,600113.540 Burned PA latched vet Nude trverlPe for BBC vA 20 and Spear... (Popoff, N 5406 0.130 a 24,800V0.580 00433 0.280 11534 0100 611300103 1200 contra 5ystenl fa on Neptune i I tuno 1100 80437 0.280 5101327 0700 TiP41A 0220 9 0407 0730 SOCKETS 34,200V0.660 Speoat cectotry loteuttai compensate", N 5408 0:130 , 0,, 0.000 2114 2.300 33/10090 .610 47102 1.800 B0535 0.380 4-12500 1.000 710410 0250 Rad, a/samovars Cylinder Couplings For wide angular movements 07 706 11013 80536 0.310 61.12501 1.100 110424 0.220.14 pm 0.08(1 300600V 0.710 25322 :166) ...... O.P.T AenNontral on Neptune 2 lot acc,one norm, .n Bo w 0.400 51.12955 0.550 TIP420 0250 6A/20061 1N 76071 0 000 2732 4.99.777 Easy access /or servicing and vievano al woriang pans 60115 0100 00538 0400 MJ3000 1150 71547 0.400 VOLTAGE 7840 0120 69,30090.000 2764 7.000 2540000 Powers., - lilts IS kb Aherne 50148 0100 130032 1.000 4J3001 1150 TINS 0 400 7000147000 20 pin 0140 4116 0.750 50154 0.060 110/165 0.800 61J8290 0300 17549 0 400 7803 0150 22 pin 0160 1.600 Hand nein simulator for processing treparesAIX option) 606 6 ON 69157 0120 60180 0160 14J8304 0300 TIP110 0 470 7812 0.350 24 pm 0 180 , m02 , ,/,,, Neptune rooms are Awn alt form as lolioWs 50101 0.130 10181 0 180 INJE340 0 350 TiP112 0.540 7815 0 350 2001 , 0200. 1.-M38- 0- 075-00 ELECN NYTIC 50103 0150 BF183 0.200 000350 0.500 P5115 0.450 7810 0 350 40 /6/1 0.250 Neptune I robot 0181w. power supply' t i7S0.00 AOC opton 'component, fa to man control board] 0600 L4. 311 1.060 470010.16V 501050 0.1110 BrI84 0200. 000520E520 0300 T15117 0.560 782 4 0 050 LM709 010431 CAN 0000 N205E1 0140 00185 0200. 5116295580 900 T7PI20 0.430 NeptunePPE 7i7056 i soma..... electrons, ./ meady woo 6435.06Neptune Isenulator .256006.16.00 . CopperM AN* AnsaPPP!, 037.90 7905 0.350 LM723 0320 80107 0.070 Br194 0.050 T15121 0.460 7912 0.400 OPlAnel nth thee fregered grtkper r 675.00 130108 0.070 BF195 0.050 0447 0.060 115122 0.470 vAtes Ela 11503087 0M741 7915 0 400 LM741 Neptune 2 roman is 1,0,, 0,14,0 Li U5.00 kpc ,,,,,,,,,,, 014.50 50109 0070 BF196 0.060 0490 0.040 115125 0.470 2 532 7918 0 400 B0115 0100 80199 0.060 0091 0.040 T15126 0560 Neptune 2540000 electrons, 'ready ouoisi 447300 Commodore VIC 20 COnnettOr lead 0n0 TAN A Word I I CSO 7924 0100 008(1 0 400 Ml...' OM 1n0. 74r 80118 0.110 80200 0.160 04200 0.070 '15127 0.560 FCCEI2 0.400 T------0 Neptune 2 simuwor 85200 Sirvier Lc Scwourn connector iead 81100 50140 0.190 7805 0 280 ECC63 0.430 9E555 0150 T51PLE10 Elf257 0180 01202 0070 1152955 0.310 All pion Aclosevo of VAT sad Aloe wad do nil ol Istorel. ISA 00141 0.190 130258 0.180 0C28 1.000 1103054 0.380 78012 0200. E0053 0.400 9E556 0 400 051195 00142 0.190 8f 259 0.1110 0029 0100 11530550310 7805 0283 60085 0400 816551 10003862.260 80743 0,708 g033, 0.000 0015 1.000 17087 010, 74018 0180 60181 0.490 350 0 300 mentor it all.Brinsts in design and manufacture anci c omes in. lorm Ar an ostonorknoly AP 00147 0.055 80337 0.200 0045 0.500 '390 0.150 74024 0.350 801184 0.520 89653 mentor 80748 0.055 88338 0.200 0071 0 300 601.130 0.570 600 0.000 On , '1591 0180 1113098 1 000 0C149 0.055 K082 0250 01155 7 U M 0300 7072 0 500 1.613178 2.200 desk-top robot mentor fol. lot Ire power supprol 0550.00 00157 0165 80423 0.210 25 29040 200 601.84 0.570 600 0100 00200 1100 01.13171 1 500 mervor Cantroirvearcnas 1.000 25 2 905 0200. 130055, 00159 0.055 80458 0190 00521 80085 0 570 'rvs Tom . , ewrivai0Pow•ed tf ainir, deady 004 8035.00 25 2906 0.180 L6132384.200 BCI82 0.060 8E459 0110 0 6012 1.000 M I6 0 490 800 0.320 robot/ nas 6 axes of movement. sanataneousY pop,. Woulota Vector. 25 2907 0.110 054723 0 320 0F929 0.200 FRO 0.310 80)(70 Ann.ofBrOke0 a gives smoom operation. 39200 09821. 0 060 00560 1000 7811000 5 700 21129260.080 EEO 0.340 500 0290 00783 2060 056134 0.200 o0561 1.000 4.3 4.. 2N 3019 0.280 785051(05.200 Ad ...d9."...... ' 001000500?Components Id to soma BC1831. 0.060 89085 0.200 Ern 0 430 878701 toe in eduCationat esAblervflen13 011ser ern VONA PoardI 019.50 ON .3063 0.180 7801)1C 110 0, ',man 044007 iongale Nonce 'ant) nylOn 80184 0.060 01087 0.150 020088 0800 80183 0.450 500 0110 26 30540350 790010 2 5 Dearhgs, integre contra electronics and• BBC connenor lead 002.50 1301841 0.060 BT988 0150 02010B 0800 • . ' 60184 0.510 1311701 214 30550.320 791100C 6.700 power soppy. speciatoroavy for menu, Comma .. viC 20 connector. lead 00212 0 060 B M° 0.140 E134 1.900 BOO 0 060 214 305560 380 ETU 0.310 BYX71 / t onspensonon, cpponal On-Oavd NIX. and Ana okso-in pond 8,4.50 10212L 0.060 B M, 0140 505560 1100 25 34400.sao Tx'sa-hesdsamaator mlne teacrungPers0ant SNP. Dt Spann/co COnneetor lead 615.00 130213 0.060 0r052 0140 SAS570 1100 0087 0.310 600 0 800 213 34420.050 L.ae Neptune. ANN Of S Pragf am •ngos M 502131. 0.060 BFY56 0 .250 5576003/11 400 PC97 1.030 NM . Only by yOur Computer s rnemoN All pp. onlonn A VAT aod 00214 0 050 81157 0.250 A7601351 400 502141. 0 060 E1044 8150 947602361400 Please add 50p P&P and VAT at 15 /.. Govt. Colleges, etc 50237 smo 50100 0.140 097405341 too o ders accepted 50230 0170 65919 0.150 w o ma70, Quotations given for Large Ouantities 80300 0160 13SX20 0.150 S5761150.700 CYBERNETIC APPLICATIONS LIMITED 00301 0180 85821 0.160 SN762260 900 Please allow? days for delivery 60302 0180 05X26 0160 S57622701030 All brand-ne w Co mponents. All valves are new and boxed Ai yborns le ' PORTVJAY TRADIN G ESTATE. AN D OVER. HA NTS 710 3PE 80029 0190 80303 0.180 Ring for items not listed. We stock 3,000 items pplic atle m s TEL 107641 50093 Telex. 477019 80327 0 060 132976 0.180 120000 0520 80382 0 060 B1106 0.900 14006-60 8120 .. 60337 0 060 91109 0.900 000720 80328 14052 1-2 0.060 07 776 0100 TAG44430.7601 50557 0.060 81119 1.000 7A044440.760 GRANDATA LTD. 5032 1 500 81320 1 000 TAW° 0160 9 & 12 THE BROAD WAY, PRESTON ROAD 90033 1 500 00104 1.000 18412050.450 WE MBLEY, MIDDLESEX, ENGLAND 80834 1.500 00106 0.800 78A395 0.600 80142 0.200 90108 1.000 18A396 0100 Telephone: 01 -904 2093 81 904 1115/6 53 60456 1.150 00700 1100 104020 0.750 Telex: 932885 Sunmit TOOLTRONICS 13 PIECE TOOL KIT AND CASE BRAND NEW LCD MINIATURE TOOLS • DISPLAY - MULTITESTER 13-piece tool set hbused ri RE 188m attractive moulded -platic' LCD MEGOH M,INPUT IMPEDANCE case with clear sliding cover PRECISION • 31/2 IP digit • 16 ranges plus hFE test facility for • 1 off 5' snipe nose "radio" JEWELLERS' TOOLS , plIers with side cutters • 1 PNP and NPN transistors • Auto zero, auto polarity • Single-handed, push-button operation Rustproof Tempered Handles and Blades. Chrome , off 41/2 ' side cutters • 1 off Plated Handles. Swivel Heads for use on Precision 41,7 end cutters • 2 off hex. • Over range indication • 12.5m m (/12 -inchl large work. "Allen" key drivers 2mm and LCD readout ' Diode check • Fast circuit 2.5m m; 2 off cross-point protection • Test leads, battery and instructions SCREWDRIVER SET "Philips" drivers No. 0 and included. 65121 precision screwdrivers in hinged plastic case. - No. 1 (with tom my bar) . 6 Sizes -0.8. 14; 2, 2.4, 2.9 and 3.8m m £1.75 off precision screwdrivers. Max. indication . 1999 or 1999 Sizes from lmin to 3.5m m • Polarity indication Negative only NUT DRIVER SET ------. , Positive readings appear 5 5T31precision nut drivers in hinged plastic case. With without i sign turning rod. Sizes -3, 3.5, 4, 4.5 and 5mm £1.75 ONLY £7.50 ORDER No VP102 Input Impedance 10 Megohins TOOL SET Zero adjUst Autom'atic 55T41 precision instruments in hinged plastic case. LOW COST CUTTERS/PLIERS - SPECIAL DRIVERS Sampling -time 250 milliseconds Crosspoint (Philips) screwdrivers - HO and H1Hex Temperature rang 5 C to 50 C key wrenches. Sizes - 1.5, 2 and 2.5mrn. f1.75 Miniature round nose cutters insulated Power Supply 1 PP3 or equivalent 9V WRENCH SET handles 4/12 inch length. Order'- No. Y043 battery 5 5751precision wrenches in hinged plastic case Sizes ,! FLEXY DRIVER ohsumptIon 20mV17 -4.45.5. 5.5 and 6min £1.75 Miniature long nose pliers - insulated , A .flexible shaft.- screwdriver . for those Size 155 • 88 • 31min handles 5/12 inch length. Order No. Y04:4. awkward to get at screws. Overall length 81 4 RANGES inch. Order No, FS-J Flat blade.4min FS-2 DC Voltage 0-200rnV SIGNAL INJECTOR Miniature bend nose pliers Cross point No. 1 £1.75 Nith. insulated handles 51/2 inch 0-2-20-200-1000V Acc, 0.8% length. Order No. Y045. AC Voltage 0.200-1000V Ace. 1.2% DC Current 0-200uA' Miniature end nippers' - 0.2-20-200mA, 0-10A. Acc, 1.2% insulated Resistance 02-20-200k ohms • handles 4/12 inch length. GRIP DRIVER 0-2 Megohms. Ace. 1% Simple push button operation. Oscillates at Order No. Y046. 8 inch long screwdriver with spring loaded 700-1kHz with harmonics to 30MHz. 1.4V pip Miniature snipe nose pliers with sioe grip on and to hold screws in position while BI-PAK VERY LOWEST PRICE output. Impedance 100. Ideal for trouble cutter and sorrated jaws - insulated reaching into those difficult places. £45.00 each shooting with audio equipment. One "AA" handles 5 inch length. Order No, • Order No. S0-1 Flat blade 4ron , penlight battery supplied. 0/N . vpg6 £2.50 Y042. SD-2 Cross point No , £1.20 Leather case for 188rn £2.50 EACH ALL A T £1.55 each each. LOGIC PROBE MULTITESTER ANTEX SOLDERING IRONS BA BOX SPANNER SET MODEL 0/NO PRICE Contains one of eaCh size: ORA, 2BA. 46A, 689 1.000 Ouv including test leads & SX 25 watt 1931 £5.40 889. Fixed Chrome Vanadium Steel shaft ,n Battery Autorncatic levelling. 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BI-PAK SOLDER- 0/No. VP112 £4.75 AND DRILL KIT DESOLDER KIT Complete pce Kit .comprises MINIATURE VICE 1 Expo Mini Dialr10,000RPM Kit 'comprises: 0/No-: VP80 Miniature plastic and metal 1 High Quality 25 Wan BATTERY TESTER 124 chc.incl. 3 collets & vice with strong suction base General Purpose Tests all types of battery including 3 s Twist Bits for portability. Singlb action tandard, NICAD, Alkaline, etc. Takes Lightweight. Soldering. 1 Sheet PC13 TranSfers 210rnm' to secure or release suction. Iron, 240v mains incl. all standard sizes including 6V 150rorn • . Plastic jaws with rubber pads • 3/16" (4.7Mm) bit. 1 lantern batteries and watch/ 20m m wide, open out to hearing aid cells. Also tests fuses 1 Etch Resist Pen - Quality Desoldering Pump" . and lamps by means of internal 40m m. Dims. 85 x 65 x . High Suction with automatic 7 1/25t pack FERRIC CHLORIDE 9V (PP3I battery. Can also be 60m m approx. ejection. Knurled anti-corrosive crystals FANTASTIC VALUE used to recharge NICAD casing and- Teflon nozzle. 1.5 metres , 3 sheets copped clad board, ' of De-Soldering braid on plastic • batteries by means of external 0/No, VP95 ONLY £1.60 2 sheets Fibreglass copper clad' beard dispenser. 2 yds (1.83m m) Resin 3.12V d.c. power supply (not Cored Solder on Card. 1 Heat Shunt included). Dims: 185 x 103 x Full instructions for rnakinv your - Full instructions provided. 30inm (approx.) too tweezer Type. own PCB boardS METRIC & 0/No. VP101 £7.00 Total Retail Value over C12.00. , • • is Retail Value over f15.00 BRITISH OUR SPECIAL KIT PRICE £9.95 • • ORDER NO VP81 MEASURES POWER SUPPLY OUR BI-PAK SPECIAL KIT PRICE Power supply fits directly into AUTOMATIC WIRE STRIPPER I 13 amp socket. Fused for £9.95 Will clamp 5 different sizes of wire, strip and Sled tapes in sturdy ABS plastic case. Silk • safety. Polarity reversing remove the insulation in one single operation. socket. Voltage switch. Lead wrist strap. These yellow coated convex tapes RATCHET SCREWDRIVER KIT Accepts wires of dia., linm, 1.6m m. 2mm, 2.6rnm with multi plug input - 240V have inch and metric graduations. Automatic and 3.2m m. Has hardened steel cutting surfaces, AC 50Hz, Output - 3, 4, 5. 6, Comprises 2 standard screwrinver blades 5 & push-button return. 2m long x 13m m wide. spring loaded insulated handles. 7,5.9 & 12V DC Rating - 7mm size. 2 cross point size 4 & 6. 1 Ratchet 0/No. VP89 0/No. 1997 £5.45 300ma mwse. 0/No. 137 ONLY £3.75 handle 5-in-1 Kit. 0/No. 3296 £1.45 each.

Use your credit card Fling us on Ware 3182 Send your orders to Dept PW9 BI-PAK PO BOX 6 WARE. HERTS NOW and get your order even taster Goads SHOP AT .1 BALDOCK ST W ARE, HERTS nomially sent 2nd Class Mail TER MS CASH WITH ORDER. SAME DAY DESPATCH ACCESS Remember you must add VAT at 19% tO your BARCLAYCARD ALSO ACCEPTED. TEL (0920) 3182. GIRO 388 7006 Total order ADD 15% VAT AND 75p PER ORDER POSTAGE AND PACKING BI-PA K Postage add 75p per Total order Sequential Logic Techniques iri

M.TOOLEY BA and D.WHITFIELD MA MSc C Eng WEE

I AST month we carried out a detailed This simply consists of two two-input This truth table shows rather more I—investigation of the operation of a AND gates, a two-input OR gate and clearly than its predecessor how the universal shift, register. This month we an inVerter. The truth table for this SELECT input operates; the X's in the shall turn our attention to another arrangement is given in Table 5.1. As truth table being used to denote the device which finds a wide range of ap- "don't care" states. plications in the digital world, the data A B s Nt The switch equivalent of a four-way multiplexer. o o 0 o data multiplexer is shown in Fig. 5.3. Data multiplexers, or data selectors o o 1 o as they are sometimes known, o 1 o 0 generally have one output and several 0 i 1 1

inputs. Any one of the inputs can, by 1 0 0 1 B OUTPUT placing appropriate logic levels on its 1 0 1 o DATA INPUTS 1 1 o 1 control inputs, be routed to its output. c 1 1 1 1 Data multiplexers thus provide us with a means of sending several different Table 5.1. Truth table for simple two- digital signals along a com mon signal way data multiplexer line. T so T si In essence the data multiplexer acts -6 77-17j can be seen, whenever the SELECT in- SELECT INPUTS as a multi-way switch however, by vir- put is at logic 0 the output, Y, takes the Fig. 5.3. Simplified switch equivaiern tue of its internal logic and unlike its state of the A input wheras, when the of a four-way data multiplexer conventional analogue counterpart, the SELECT input is at logic 1, the output device will only operate with digital takes the state of the B input. Here the output, Y, can be connected signals. By grouping together the states for to any one of the four data input lines, The switch equivalent of the sim- which the output remains unaffected A to D, by means of an appropriate in- plest form of data multiplexer is shown by one or other of the inputs (we shall, put on the two select lines, SO and Si, in Fig. 5.1. This two-way arrangement for obvious reasons, call these the The truth table for the four-way data

r — "don't care" states!), the truth table of multiplexer is shown in Table 5.3. The SELECT OUTPUT the two-way multiplexer can be corresponding Boolean expressions INPUTS {' A T h j •-- OUTPUT B I A reduced to that shown in Table 5.2. are:- T _J A B s Y Output Select Inputs 'PEON, SELECT 0 x 0 0 Y = A SO . S1 Fig. 5.1. Simplified switch equivalent 1 x 0 1 Y = B SO. Si of a two-way data multiplexer x o 1 0 1 1 1 Y = C SO. Si is equivalent to a single-pole double Y= D SO.S1 throw (SPDT) logic switch. The two x don't care switch states are controlled by means We shall now investigate the operation 1 of a third select input. When a logic 0 Table 5.2. Simplified version of table of a practical four-way data multi- appears on the SELECT input the 5.1 plexer, the 74L5153. switch moves to position A whereas, when a logic 1 appears on the SELECT DATA INPUTS SELECT INPUTS OUTPUT input the switch moves to position B. The internal logic of the two-way A B C D SO Si Y data multiplexer is shown in Fig. 5.2. 0 x x x 0 0 0 1 x x x 0 0 1 A x 0 x x 0 1 0 x 1 x x 0 1 1 x x 0 x 1 0 0 x x 1 x 1 0 1 x x x 0 1 1 0 x x x 1 1 1 1

x = don't care

Fig. 5.2. Logic arrangement of a two- 1 way data multiplexer Table 5.3. Truth table for a four-way data multiplexer IPractical Electronics February 1985 UE

THE 74LS153 any of the data (DO to D3) or select (SO The circuit used for our practical in- The 74LS153 contains two four- and Si) inputs. vestigation of the 74LS153 data mul- way data multiplexers which have The internal logic of the 74LS153 is tiplexer is shown in Fig. 5.6. It should com mon select inputs. The pin connec- shown in Fig. 5.5. This clearly shows tions of the 74LS153 are shown in Fig. how the EN inputs are gated with the 5.4. The two halves of the device select, inverted select, and data inputs at each of the four four-input AND gates on both sides of the device. The

outputs of each set of AND gates are 01 then combined in a four-input OR gate. The 74LS153 is effectively nothing more complex than a two-pole four- way switch! The complete truth table for the 74LS153 is shown in Table 5.4. This truth table is, of course, identical for each half of the device. When both select inputs (SO and Si) are at logic 0, the output (Y) reflects the state of the DO input. With SO at logic 1 and Si at Fig. 5.6. Practical arrangement used to logic 0, the output takes the state of PE4SH demonstrate the action of the 7415153 the D1 input, and so on. Fig. 5.4. Pin connections for the 7415153 SELECT INPUTS DATA INPUTS ENABLE OUTPUT (referred to as A and B) are conveniently brought out to pins on opposite SO Si DO D1 D2 D3 EN Y sides of the package; the A-side using x x x x x 1 0 pins 1 to 7 whilst the B-side uses pins 0 0 x x x 0 0 9 to 15. Supply connections, using the 0 0 x x x 0 1 conventional pins 8 (OV) and 16 (+5V), 1 0 0 x x 0 0 are com mon to both halves of the 1 0 1 x x 0 1 1 device. 0 x 0 x 0 0 0 1 x 1 x 0 1 Each half of the 74LS153 has its 1 1 x x 0 0 0 own active low enable, EN, input. 1 1 X-,OX X XXX X x x 1 0 1 When these inputs are taken to logic 1 the corresponding outputs immediately x = don't care go to logic 0 irrespective of the state of Table 5.4. Truth table for the 7415153 data multiplexer

A /\

EN 00 DI D2 03 / SO 00

(6 1 15 (4' (31 (10)

• • • • • • • u YYu

IPE49/Aj YB

Fig. 5.5. Internal logic of the 7415153

. Practical Electronics February 1985 56 be noted that only one half of the Finally, S4 should be adjusted to In order to enable the normal counting device is used. In order to provide four produce a logic 1 input whilst S3 sequence, the two master reset inputs, different data inputs which may be remains at logic 1. In this condition D1 MR1 and MR2, are taken to logic 0 readily distinguished from one another, should be seen to flash 'on' and 'off' in and the four Q outputs then have fre- DO is fed from the clock whilst D1 and sympathy with the inverted clock. (i.e. quencies of 16Hz, 8Hz, 4Hz and 2Hz D2 are fed from the Logic Tutor's when the clock led. is 'on', the output approximately. momentary push buttons, Si and S2 led. is 'off', and vice versa). We can The 7414 and 74LS153 devices respectively. The remaining data input, sum marise these observations as should be left in sockets D and E whilst D3, is fed from an inverted clock signal shown in Table 5.5. the 7493 should be inserted in socket derived from a 7414 inverter. The rele- B checking, as usual, that pin-1 aligns vant half of the device is enabled by SELECT INPUTS OUTPUT with 61. The following links should hard wiring the EN input to logic 0 Si SO then be made:- whilst the two latching Logic Tutor (S4) (S3) (D1) B1 to 814 switches, S3 and S4, are used to deter- 0 0 DO (CLOCK) 132 to 63 mine the state of the select inputs, Si 0 1 D1 (S1) 63 to logic 0 1 0 D2 (S2) and SO respectively. 65 to +5V (supply) 1 1 D3 (CLOCK) The 7414 should be inserted into B10 to E4 611 to E5 socket D whilst the 74LS153 should Table 5.5. Outputs provided by the be inserted into socket E with the usual circuit of Fig. 5.7. (Note: brackets 612 to OV (com mon) orientation convention (pin-1 of each indicate Logic Tutor functions) 613 to E3 device to the respective connection 614 to E6 marked on the Logic Tutor PCB) being A PRACTICAL APPLICATION OF 616 to D4 observed. The following links are THE 74LS153 D1 to logic 0 (via a 471.tF 25V cap) required:- We shall now turn our attention to a D1 to D2 (via a 470 ohm 0.25 W) simple practical application of the D2 to D3 D1 to clock 74LS153 four-way data multiplexer. D7 to OV (com mon) D2 to E3 (data input D3) Let's assume that we wish to provide D16 to +5V (supply) D7 to OV (common) digital selection of the output frequen- El to logic 0 D16 to +5V (supply) cies of a four-stage binary counter. The E2 to S3 El to logic 0 (active low enable) four Q outputs of the binary counter E7 to D1 (D1 shows oip freq.) E2 to S3 (select input Si) can be fed to the four data inputs of the E8 to OV E4 to S2 (data input D2) multiplexer whilst the two select inputs E14 to S4 E5 to Si (data input D1) are fed with a two-bit control signal. E16 to +5V (supply) E6 to clock (data input DO) The circuit of a suitable arrangement (A total of 20 links and 2 components) E7 to D1 (D1 indicates the is shown in Fig. 5.7. ICla forms a sim- output) The two select inputs should first be ple relaxation oscillator in which the E8 to OV (common) set to logic 0 using S3 and S4. The output frequency is determined by the E14 to S4 (select input SO) output indicator (led. D1) should then time constant, Cx R. IC1b forms an in- El 6 to +5V (supply) be seen to flash rapidly 'on' and 'off' verting buffer, the output of which is a with a frequency of approximately rectangular pulse wave having a duty (A total of 13 links) 16Hz. The three other possible settings cycle of approximately 1:2 and a fre- of S3 and S4 should then be tested. The select inputs should initially quency of approximately 32Hz. This both be set to logic 0 by appropriate signal is then fed to the CLOCK input of NEXT MONTH: De-multiplexers and adjustment of S3 and S4. The output IC2, a 7493 four stage binary counter. time domain multiplexing. indicator, led. D1, should then be seen to flash 'on' and 'off' in sympathy with I LOGIC 0 the clock which is connected to the DO 470 input line. 3 S4 should now be adjusted to MR1 MR2 32Hz produce a logic 1 on the SO line whilst CLOCK 0 IC2 S3 remains at logic 0. In this condition 7493

the led. will stop flashing and become IC10 1C1b 03 02 01 00 CLOCK T extinguished. Now depress Si to 1, 3 7414 "."---1 .-• produce a logic 1 on the D1 input. The 2Hz 4Hz led. will become illuminated whilst Si 47T ov 8Hz 16Hz is held down and will become ex- 6 tinguished again when Si is released. 03 D2 D1 DO T S3 and S4 should now be adjusted S3 5 2 S1 SELECT IC3 to produce logic 1 and logic 0 on the OUTPUT OUTPUT 74LS153 TO D1 S1 and SO select inputs respectively. FREQUENCY 64 • 1‘. 0 S2 should now be depressed to EN

produce a logic 1 on the D2 input. The PE 52 OV led. input will become illuminated for LOGIC 0 as long as S2 is held down. Fig. 5.7. Simple application of the 74LS153

Practical Electronics February 1985 57 Heathkit IFS A PLEASURE TO BUILD

Bring the enjoyment back into your hobby You'll find Heathkits available for Amateur Radio with a kit from Heathkit. The beautifully Gear • Car Test Equipment • Kits For The Home illustrated documentation and step-by- • Self-Instruction Courses • Computer Kits • Test step instructions make building a Heathkit Instrument Kits • Kits For Weather Measurements. a relaxing, absorbing pleasure! Choose from their huge range of fascinating kits All the most popular kits and educational products and self-instruction electronics and are fully detailed in the 1984 Maplin catalogue (see computing courses. outside back cover of this magazine for details) or The Heathkit range includes the ultimate for the full list of Heathkit products send 50p for in amateur radio kits, computerised the Heathkit International Catalogue weather stations, a highly soph- complete with a UK price list of all isticated robot, a 16-bit comp- items. uter kit and a range of home (or classroom) learning courses. These state-of-the-art courses All Heathkit products available in have easy-to-under- the UK from: stand texts and illustrations, divided into sect- Maplin Electronic ions so that you can progress at your Supplies Ltd. own pace, whilst P.O. Box 3, Rayleigh, the hands-on exper- Essex, SS6 8LR. iments ensure long- You'll be proud to say, Tel: (0702) 552911. term retention of the "I built it myself!" material covered. (For shop addresses see back cover.)

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These digital multinieter cases are moulded in high 44 PAGE GOOD SERVICE impact black plastic and are offered at an extremely attractive price to clear stocks. PRICED AND THOUSANDS OF DP2010 - 110x 80 , 20mm, this too has cut-outs for STOCK ITEMS range switches and terminals with a smart alumin- The unit has 2 • 3V motors, linked by a magnetic ILLUSTRATED ium fascia marked with ranges etc. Battery accessi- clutch, thus enabling turning at the vehicle, and a PHONE YOUR ORDER ble by removeable cover on back 75p. gearbox contained within the black ABS housing, CATALOGUE ACCESS OR reducing the final drive speed to approx 50rpm. DP100 - Same size as above, but this was for use Data is supplied with the unit showing various as a digital thermometer, so there's only a single BARCLAYCARD options on driving the motors etc. £5.95. Suitable. 9mm 0 hole in the front panel 75p. ON REQUEST Two new types of wheels can be supplied (the Official orders welcome - minimum invoice aluminium discs and smaller plastic wheels at now charge f10. No. min. on CWO. sold out). Type A has 7 spokes with a round black Our More has enormous stocks of tyre and is 100mm dia. Type B is a solid heavy duty components and is open from Minimum Access wheel 107mm dia with a Ilat rigid tyre 17mm wide. 9 530 Mon Sat Come & see us'tm ode f500 Photo shows gearbox with one of each type of ELECTROVALUE LTD 28 St. Jude's Road. Englefield Green. Egham. wheel on it G R E E N W EL D Surrey TW20 OHB Phone Egham (0784) 33603. Telex 264475 PRICES - Gearbox with data sheets - £5.95 ea 443C Milbrook Road Southampton North Branch, 680 Burnage Lane. Manchester M19 1NA Wheel type A. £0.70 ea SO1 OHX Tel 107031 772501/783740 Wheel type 13 £0.50 ea AU, PRICES INCLUDE VAT JUST ADO 60p POP Phone 061 432 4945 Please mention this publication when replying

58 Practical Electronics February 1985 Mono/Stereo Ch & Ff JOHN M.H.BECKER PART TWO

T HE clock signal that causes the delay chips to sample and about 64ms to 7.68ms, cascading two delays doubles the transfer their charges from stage to stage is produced by delay times. With the modulating oscillator switched out of IC9 (Fig. 6). This is a standard linear voltage controlled circuit the unit can of course be used as a standard reverb or oscillator chip that produces a squarewave output the fre- short-echo unit, though these effects will not be so pronoun- quency of which is related to the value of C24, the current ced as those obtainable with the September 1984 PE Echo- through VR9, and the voltage present on pin 9. The single Reverb unit. output from IC9 needs to be split into two opposing phases as required by the delay chips. If a normal phase split were PO WER SUPPLY to be given then the opposing edges of the antiphase square The unit has been designed to operate from two 9 volt waves would coincide. This overlap is prone to causing batteries producing +9V/OW-9V, and drawing between system noise from the delay chip outputs even though the 13mA and 20mA, depending on the clock oscillator rate. IC2 TDA1097 is basically a low noise device, capable of a 77dB and IC3 though do not like a total voltage drop across them signal-to-noise ratio at a 100kHz clock frequency, though in excess of 16V, which also means that controlling voltages this degrades slightly with lower clock rates. The overlap on must not exceed this either. The positive voltage delivered to the edges of the clock is eliminated by the flip flop stage IC2, 3, 9, 10 and 11 is thus reduced to a more suitable level ICI 0 in conjunction with the NAND gates ICI 1a—b. C25 and by the drop across the resistor R62 in the delay line bias R83 slow down the mutual triggering of the flip flop and divider network. The voltage at R62 is within limits with all gates, resulting in a twin phase output having a short delay i.c.s in circuit, but may rise if any of the said 5 are not in their between the respective squarewave edges. Oscillograms sockets when power is applied. IC9-11 will not mind, but Fig. 7a to 7c show the 'with' and 'without' effect of the IC2 and 3 may object. The unit may be operated from a overlap elimination. stabilised power supply if preferred. The acceptable range is Varying the voltage applied to pin 9 of IC9 varies the clock from +5V/OW-5V to +9V/OW-9V. If it is necessary to run frequency. For the automatic modulation of the clock a con- from a power supply greater than +9V/OW-9V then two stantly varying voltage is produced by the low speed triangle voltage regulator devices should be inserted between the wave oscillator around IC8a—b, and having a frequency power supply and the unit as shown in Fig. 9. The voltage governed by the resistance of VR7 and the value of C22. drop across the regulators must be greater than 2V, and R62 (Oscillogram Fig. 8.) Decreasing either increases the output may be replaced by a link wire. frequency. The modulation can be switched in and out by S4, and the level varied from nil to full by the depth control CONSTRUCTION VR8. C23 slightly rounds off the triangle peaks at faster The component layouts for both boards are shown in Figs. modulation speeds. The modulating frequency range is con- 10 and 11. The short link wires on the p.c.b.s can be made trollable between about 50 milliseconds and 30 seconds, from resistor cut-off leads shaped to the correct spacing the clock frequency range is between about 12kHz and with thin nosed pliers. Sockets should be used with all i.c.s. 100kHz. For a single delay chip the delay time range is thus The wiring diagram for the unit is shown in Fig. 13. Bring the

TO R62/C19

063 10k IC11b 024 401113 470p

6 12 ICIO 11 IC9 4013 4046 10 CLOCK TO

9 IC11a IC2 &3 1 I C29 C31 C27 5 682 40116 1 106 65 4 100n 100n 4 Op RBI 1M2 minC25 56p

IC8 -PING= —VE IC8 -PIN 8, -I-VE C30 C32 C2B VR9 IC11-PINIG. +VE 100n T 100n T 470 7 100k ICII -PIN 7 . —SE —V 0 0

PP 16276

Fig. 6. Circuit diagram of the Clock Circuit

Practical Electronics February 1985 59 USIC PROJECT

Fig. 7a. Usual appearance of two Fig. 7b. Close up of overlap Fig. 7c. Accentuated overlap square-waves without overlap removal as used in unit removal Fig. 7. Clock edge overlap of two anti-phase square-waves

OPTIONAL REGULATOR FOR REDUCING VOLTAGE FRO M EXISTING PSU OV TO UNIT TO LEVEL SUITABLE FOR CHORUS UNIT

-V

[PE1633G1

Fig. 8. Modulation oscillator Fig. 9. Optional regulator circuit waveform connecting wires neatly around the edges of the p.c.b.s to eyes of an eagle, thoroughly check all the p.c.b. joins with a the controls. The clock leads to IC2 and IC3 should be magnifying glass. Only after all checking has been done brought forward past C19, turn left at the front panel, then should the i.c.s be inserted into their sockets, remembering along to the small p.c.b., turn right and connect. Do not take that IC2, 3, 7, 9, 10 and 11 are MOS devices and require the them on what appears to be the shorter route across the normal handling precautions. The main point being to keep main p.c.b. as this would direct them across some parts that yourself and equipment free of static electricity by touching might pick up any stray radiation signal. Unless you have the a grounded source before handling them.

6123 . 0 ® •-f R54 1.4 N R27 • 14 R72 4.4 R55 4-• .4 MEM I+ C9 • CI •-f87I 4.1 825 CI8 CB .4 R30 1-• • CIO • OH C2 R 3 ILO W EI zits •-f R29 Fs •-f 832 4-• .4 R5 1-• OH 82 1.50 KEINI MEM. R33 1.4 Emu Ell can 0-4 C11 1.56 Ken.. LEM" •••1 R35 .4 57 .4 815 1.0

11...4 CI 7 Fer C12 1-• I ' R5 7 Ifte 0-1 C 3 HD C7

*-1 R42 1..0 14 R34 . t .4 R8 1.10 RI4 141 I H CI6 •1 R22 11+ C13 IL* EMI 637 RIO 1, 11 IF 04 +1 1 .41 ▪ R40 .-4 866 1.• 404 5I3 • ci 5 • -• IA ft lk 1111 111 ilht R39 h• -11 0-1 812 1.0 R59 R60 1C2 .4 511 he C28 14 538 4.0 • • • • 11 1 R45 6117 11.i86 16

.„ f R7 .011 :64 11,1 135:,..r hi I 0.4 666 ly 1 1 .4 818 1 1 R67 h. 862 RIO • 1347 106 01 R69 1-• .1-1 R654 • 1348 14 820 15 H. 568 C20

0-4 R49 1-• R73 I It 121f 9 R ; 3-75

I11- 111

[0616306] I0 11 111 T

Fig. 10. Component layout of the Main Board

60 Practical Electronics February 1985 19 20 21 22 23 24 25 SETTING UP This is quite straightforward and specialised equipment is not needed. First, VR1 to VR3 midway, VR4 max resistance (anticlockwise), VR5 and VR6 min, VR7 to VR9 max, Si to S4 off. Plug in a music signal from a prerecorded source into the X1 socket. Check that the output level reaching the main amplifier used is the same as the original. Switch on S3 enabling the VCA, and bringing up VR6 a change in amplitude and tonal quality should increase. Rotating the clock oscillator speed control VR9 to its maximum resistance will slow down the delay and emphasise the double tracking effect. This will be more apparent with staccato sounds rather than mellow drawn out notes. Adjust VR3 around its midway point until minimum waveform distortion is heard,

26 27 28 29 PEI631 Gi which will also coincide with the best delay effect. If an oscilloscope is available, the waveform balance will be obvious Fig. 11. Component layout for the Clock Board when monitoring the output at VR1 and VR2 in the presence of a strong input signal. (Oscillograms Figs. 12a and 12b.) Switch on S4 bringing in the sweep modulator. Varying VR8 will vary the modulation depth, and VR7 will vary the modulation rate. Switch off S4, reset VR9 to slowest clock speed, VR6 to maximum level, switch on S2 for feedback enabling. Slowly bring up VR5 and a hollowness to the signal should come in. Maximise VR5 and carefully reduce the resistance of VR4 Fig. 12a. Sine-wave with VR3 un- Fig. 12b. Sine-wave with both VR1 until the circuit almost goes into full balanced but VR1 correct and VR3 correct feedback howl. If howl occurs, sharply Fig. 12. Traces seen at the wiper of VR1

BATT 2

15 27 29 28 21 20 FRONT PANEL

53 52 54 MIX FEED LEO BACK PCB PIN 12 NOT USED LINK PCB PIN 138.22 LINK PCB PIN 168.25 LINK PCB PIN 17 8.24 Fig. 13. Wiring diagram LINK PCB PIN 18 8.23 REAR PANEL , (PE1632 NOTE RI 8. 628 ON JACK SOCKETS

Practical Electronics February 1985 91 Fig. 14a. Clock residual with VR1 Fig. 14b. Clock residual with VR1 Fig. 14c. Sine-wave signal with VR1 unbalanced (no signal) balanced (no signal) unbalanced but VR3 correct

Fig. 14. Traces seen at the wiper of VR1 reduce VR4 and start again. Aim for the closest possible to matter of personal preference, but the author feels that as the howl point. Howl is more likely to occur with strong bass with any effects unit, moderation is the keyword. Certainly notes. Switch on Si to couple the two delay circuits in series overemphasis of an effect is dramatic, but it is easier to and so produce the double emphasis. If necessary back off become tired of an over dramatic effect than one which VR4 slightly as the increase in level may kick the circuit into produces a discrete change. In general terms music having a howl again. If an oscilloscope is not available VR1 and VR2 high harmonic content, but otherwise of a simple nature, will should be left midway and ignored, otherwise adjust them benefit most. Mellow or full orchestral sounds will not show for the best balance point of the residual clock frequency in the same degree of change. In the first case there is insuf- the absence of an input signal. (Oscillograms Figs. 14a to ficient harmonic information available in the signal for the ef- 14c.) Switch on S4 and experiment with the various settings fect to fully develop. In the second case, the sound is already until familiar with the control options available, if necessary so full that the effect will probably be lost amongst the tonal readjusting VR3 or VR4. complexity unless the *original sound is full of spiky waveforms. The harsher sounds of voice, drums, harmonic- USE ally rich synthesiser and organ music produce excellent There are no restrictions to the type of signal fed in effects as the waveforms involved are complex. Pure sine provided that the amplitude is less than the distortion level, tones and muted waveforms, especially in the lower octaves, and that the type of music lends itself to enhancement will be less apparent. For the chorusing effect a slower clock within the factors discussed earlier and sum marised below. oscillator speed is preferable as the delay time is greater, for It will soon become obvious which type of music requires flanging, faster clock speeds are better as the phase shift which particular control setting for the best effect. This is a occurs then at a more marked rate and spacing.

Mir lei. illir Photograph illustrating the internal details of the Chorus and Flanger Unit

Practical Electronics February 1985 P.E. AUDIO EFFECTS AND OTHER SUPER SOUND KITS! CODE STD BOX BLK BOX BASS BOOST: Increases volume of lower octaves SET 1389 £8.46 £11.46 BLOW BOX: Voice operated VCF & VCA for fascinating effect6ET 214 £24.33 £28.33 CHORUS (SIMPLE): Multiplied solo enhancement SET 162 £31.40 £34.90 COMPRESSOR: Limits & levels maximum signal strength SET 133 £10.86 f13.86 ENVELOPE SHAPER: Note triggered ADSR unit with VCA SET 174 £17.15 £20.65 EQUALISER: Variable combinations of Low, Mid, Top & Notc16ET 217 £22.33 £25.83 EQUALISER: 10 Channels fully variable SET 134 £37.83 £41.83 FADER: Voice operated with 5 response controls SET 167 £14.21 £17.21 P.E. MONO-STEREO ECHO-REVERB (SEP84) 200ms echo, lengthy FLANGER (SIMPLE): Fascinating phased resonance effects SET 153 £22.74 £26.24 reverb, multi-tracking kit as published - BLK box: SET 218 £55.66 FREQUENCY CHANGER: Tunable note & waveform modifier SET 172 £34.46 £37.96 FREQUENCY DOUBLER: Guitar octave raiser & tone changer SET 98 £9.80 £12.80 FUNKY-WOBULO: Modulates a singing voice SET 149 £12.40 £15.40 FUZZ: Smooth distortion, retains attack & decay SET 91 £10.57 £13.57 GUITAR OVERDRIVE: Heavy fuzz with selectable qualities SET 56 £19.73 E23.23 GUITAR SUSTAIN: Extends note decay time, with noise gate SET 222 £22.81 f25.31 GUITAR TO SYNTH INTERFACE: With voltage & trig outputs SET 173 £32.81 £36.37 HAND CLAPPER: Auto & manual variable clap effects SET 197 £22.69 £25.69 V ag HEADPHONE AMP: 2 watts into phones or speaker, variableSET 156M £12.03 £15.53 P.E. FILTER-SHIFT PHASER (OCT84). Enhanced Phasing with JABBERVOX: Voice disguiser with reverb & tremolo SET 150 £2364 £27.34 METRONOME: With audio output & visual beat & downbeat SET 143 £13.81 £16.81 modulated filter shifting. Kit as published - BLK box: SET 226 MIC PRE-AMP: Variable again & switched tone response SET 147 £7.13 £10.13 £39.13 MIXERS: Several in catalogue MOCK STEREO: Splits mono signal into stereo simulation SET 213 f19.87 £23.37 MULTIPROCESSOR: Flng, Rvb, Faze, Fuzz, Wah, Trem, Vib SET 189 f57.14 £61.14 MUSIC MODULO: 8 variable tremolo & wah guitar effects SET 196 E18.79 £21.79 MUSICAL CALL SIGN: Programmed call sign generator SET 121 £12.91 E16.41 NOISE GATE: Reduces tape & system noise SET 145 E9.97 £12.97 PHASER (SIMPLE): Auto & manual rate & depth controls SET 164 £18.40 £21.90 P.E. RING MODULATOR (NOV84). With multi-waveform VCO, REVERB: (SIMPLE) Mono/stereo, variable depth & delay . SET 203 £25.54 £29.54 Noise Gate & Auto-level Control. Kit as published - BLK box: RHYTHM GENERATOR: Computer driven, 9 drum effects SET 185 f30.64 £3464 SET 231 £39.99 RHYTHM GENERATOR: 15 pre-programmed.rhythms, 9 effectsSET 170 £35.64 £39.14 ROBOVOX: Versatile robot type voice modifier SET 165 £21.03 £24.53 SPEECH PROCESSOR: Clearer speech and level control SET 110 £9.68 £12.68 STORMS EFFECTS: Auto & manual wind, rain & surf effects SET 154 £15.86 £19.36 SWEEP GENERATOR: Auto sine wave 20Hz-15KHz, variable SET 169 £16.41 £19.91 TOM-TOM SYNTH: Sound triggered, multivariable SET 190 £15.05 £18.05 TONE CONTROL: Bass, mid, treble, gain & cut SET 139 £13.17 £16.67 TREBLE BOOST: Increases volume of upper octaves SET 138T £8.13 £11.13 voir wir• TREMOLO: Mono variable rate & depth modulation SET 136 £9.71 £12.71 P.E. MONO-STEREO CHORUS FIANGER (JAN85). Superb dual VOLTAGE CONTROLLED FILTER: 12dB, variable modes SET 178 £17.02 £20.52 mode music enhancement. Kit as published - BLK box: SET 235 VOCODAVOX: Modular vocoder, 7 chans, extendable SET 152 £64.31 E68.31 VODALEK: Robot type voice modulator £55.66 SET 155 £12.44 £15.44 VOICE OP SWITCH: Variable sensitivity & delay SET 123L £13.41 £16.41 BLK BOX - steel & aluminium, black plastic finish. STD BOX - plain aluminium, lipped lid. WAH-WAH: Auto, manual & note triggered SET 140 £17.26 £20.76 SET codes include PCBs, parts, instructions, boxes, wire, solder. MAIL ORDER: Add 15% VAT & ft P&P to all orders (ove rsea s details in ca t). Payment CWO, CHQ , More details & kits in catalogue - send S.A.E. (Overseas £1 or 5 !RC's). PO, ACCESS, VISA. Details correct at press. E&OE. Despatch usually 10-14 days. PHONOSONICS, DEPT PE52, 8 FINUCANE DRIVE, ORPINGTON, KENT, BR5 4ED. Tel: Orpington 37821 (STD 0689, London 66), Mon-Fri 10-7.

ORIC AND SINCLAIR COMPUTERS ACORN COMPUTERS Electron £173 (£179) £199. BBC Model B £404 (£357) £387. Kenda double density it ismIlm m I i.5cO U ceo eel.o n m disk interface system £149 (031) £141. FREE CAREER BOOKLET vitico.:7tiv:. - ,111111111111 MME See below for suitable disc drives. IR110115TA:CtiMs, •:=0111111M OI WI CUMANA DISC DRIVES IXIBINIE BNI NN MIlll To suit disc interfaces of Sinclair spectrum, BBC B and Videogenie. Single:- 40 [ Train for success, for a better job, better pay Oric 1 computer 48K £85 (£82) £92. Oric track single sided £176 (E158) £178, 40 tr Enjoy all the advantages of an ICS Diplo ma Course, training Atmos computer 48K £171 (£158) £168. double sided £218 (£195) £215), 801r ss you ready for a new, higher paid, more exciting career. Oric Colour Printer £134 (E123) £140. Sin- £207 (£186) £206. 801r ds f234 (£209) 229. clair flat screen TV (£113) (£105) £115. Dual:- 401r ss £299 (£280) £320, 401r ds Learn in your own home, in your own time, at your own pace, £395 (£353) £393, 80tr ss £372 (£334) £374, through ICS home study, used by over 8 million already! Sinclair £187.Spectrum Sinclair Plus OL Computer £406£182 £ 80tr ds £437 (£390) 430. 1761 Look at the wide range of opportunities awaiting you. £385 £410. Sinclair Spectrum 48K £131 PRINTERS i£131 £143. Microdrive £51 (£50) £60. Whatever your interest or skill, there's an ICS Diplo ma Course R5232 interface 1 £51 (£50) £60. Special there for you to use. offer:- Microdrive + Interface 1 + 4 car- Send for tridges £102 (£100) £120. Blank micro- your FREE CAREER BOOKLET today - at no cost or drive cartridges £5.50 (£6) £7. Standard obligation at all. floppy disc interface for Spectrum £102 (£92) £112. (See Cumana disc section for suitable disc drives). Fuller FDS keyboard for spectrum £52 (£52) £62. Fuller master G Ohver 40 oose yOuandtal k Level subjects from which to unit 206 (£56) £62. Interface 2 120.45 (£20) passport to career success. £24. 32K memory upgrade kit for 16K spectrum (issue 2 and 3 only) £31 (£28) COMPUTER £30. Spectrum .Centronics printer inter- RADIO AMATEUR S face £51 (£47) £52. ZX printer has been PROGRAMMING LICENCE replaced by the Alphacom 32 £71 (£69) £82. 5 printer rolls (state whether Sinclair Oki Microline 80 £138 (£135) £165. Brother INTERIOR or Alphacom) £13 (£16) £21. ZX81 com- HR5 £162 (£146) £170. Shinwa CTI CP80 ELECTRONICS puter £15 (£44) £54. 16K ram packs for £225 (E218) £248. Cannon PW1080A £332 DESIGN ZX81 £28 (£25) £30. (£299) £329. Epson RX80 £277 (£251) £282. Epson RX80F/T 014 (E286) £316. COMMERCIAL COMMODORE COMPUTERS Epson FX80 E399 (£358) £388. Combined 1 1 WRITING FOR Commodore C16 Starter Pack £145 (£142) matrix printers and electric typewriters:- ART PROFIT £162. Com modore Plus/4 £305 (£281) Brother EP22 £173 (£166) £186. Brother £301. Commodore 64 £222 (£215) £235. EP44 £258 (f235) £260. MCP40 Oric colour TV, RADIO & Convertor to allow most ordinary mono printer/plotter £134 (£123) £140. Interfaces CAR MECHANICS cassette recorders to be used with the Vic to run the above printers from Vic and the AUDIO SERVICING 20 and the Commodore 64: £9.78 (£9) Commodore 64 £45 (E41) £46. We can £11. Bargain package:- cassette convertor supply interfaces to run the above print- compatible cassette recorder £37 (£38) ers from Sharp computers £58 (£52) £55. £44. Commodore cassette recorder £43 UK101, SUPERBOARD AND BOOK-KEEPING & ACCOUNTANCY (£44) £50. Printer interfaces for Vic 20 and VIDEOGENIE the Commodore 64:- Centronics £45 (£41) We still support these Computers. Write £46. R5232 £45 (£41) £46. Disc drive £233 for our list. Please send FREE DETAILS for the course ticked above. (£209) £234. 1520 printer/plotter £165 COMPUTER REPAIRS (£149) £159. MPS801 Printer £235 (1220) We offer a world-wide repair service. Name £245. Light pen £29 (E29) £33. Write for a quotation. SWANLEY ELECTRONICS Address The Computer Export Specialists Dept PE, 32 Goldsel Rd., Swanley, Kent BR8 8EZ, England. P Code Please allow 7 days for delivery. ICS Dept. EDS 25 041 221412P 2926 Tel: Swanley (0322) 64851. Official orders welcome. UK prices are shown first and C 8 Elliot Place .../ : >---... include post and VAT. The second price in brackets is for export customers in Europe q : ::::;- :7. 'F 7:: • and includes insured air mail postage. The third price is for export customers outside Clyde way Centre or 01 622 9911 Europe (including Australia etc) and includes insured airmail postage. CAUL: (all hours)

Practical Electronics February 1985 63 DRA 100 DOPPLER RADAR INTRUDER ALARM

The incredible 'MINI 20' 28 ranges 20kfl/V d.c. & 41(11/V a.c. (With protective fuse)

Accuracy: 2% d.c. and resistance, 3% a.c. 28 ranges: d.c. V 100mV, 3V, 10V, 30V, 100V, 300V, 600V. d.c. I 50µA, 600µA, 6mA, 600mA. a.c. V 15V, 50V, 150V, 500V, 1500V. a.c. I 30mA, 300mA, 3.0A. Ohms 0-2k0, 0-2M0 dB from -10 to +62 in 6 ranges. Dimensions: 105 x 130 x 40m m.

The 28 ranges cover all likely re- SIMPLY THE BEST quirements. Operation is straightforward, just turn the selection * The best because its blanket coverage means switch to the required range.

that all doors and windows can be covered This special offer is a wonderful without the need for individual switches and opportunity to acquire an essen- wiring. tial piece of test gear with a saving of nearly £10.00. * The best because its low power RF radiation THE IDEAL INSTRU MENT pattern is unaffected by air disturbance - unlike FOR THE CONSTRUCTOR ONLY £21.60 ultrasonic or passive IA systems. (complete with carrying case, leads and instructions) * The best because movement can be detected 'SUPER 20' through brick walls. Intruders can be deterred A SUPER PROTECTED UNIVERSAL MULTIMETER

before they intrude! I Q+ * The best because the system can be enlarged by the addition of passive detectors such as reed switches, heat detectors, personal attack I*20KWV buttons etc. ! AC AND DC

* The best because the size of the protected area 20 super • miselco is variable. Careful adjustment of the transmit- *39 RANGES ters allows "safe areas" to be created, enabling legitimate callers to avoid triggering the alarm. *INDESTRUCTIBLE I automatically protected * The best because it represents top value, the on all ranges but 10A DRA 100 in kit form costs less than most perimeter wiring systems - and offers so much more protection for your money. Accuracy: d.c. ranges and 0 2% a.c. 3% (of f.s.d.) 39 ranges: d.c. V 100mV, 1.0V, 3.0V, 10V, 30V, 100V, 300V, 1000V. Standard Kit (including 2 transmitters) £119.00 + VAT d.c. I 501.,A, 100µA, 300µA, 1.01.imA, 3mA, 10mA, 30mA, 100mA, 1A, 10A Pair of extra transmitters £29.00 + VAT a.c. V 10, 30V, 100V, 300V, 1000V; a.c. I 3mA, 10mA, 30mA, 100mA, 1.0A, 10A. ft 0-5.0kil, 0-50ka 0-500k0, 5m0, 50M12. Special Offer dB from -10 to +61 in 5 ranges. Dimensions: 105 x 130 x 40m m. Extended Kit (including 4 transmitters) £139.50 + VAT These special offers is a wonderful opportunity to acquire an essential piece of test gear with a saving of nearly £20.00.

The DRA 100 is available from (complete with carrying case, leads and instructions) ONLY 03-50

PRICES Our prices include VAT and postage and goods are normally despatched by return. POWERTRAN cybernetics 111 For details of these and the many other instruments in the Alcon range, including multimeters, components measuring, automotive and electronic instruments, please write or telephone:

PORTWAY INDUSTRIAL ESTATE, IteCbSt Instru ments Ltd. ANDOVER, HANTS. SP10 3PE. = 33 TEL (0264) 64455 19 MULBERRY WALK LONDON SW3 6DZ • TEL 01-352 1897 TELEX: 918867

Practical Electronics February 1985 64 • / M. ••••• I M O 111. • IN"; r • OIL• 9• •I •••• 1111 I • 416•011 • • i •0 • • and MICROPROMPT

ECON O MIC DIGITISER Table 1 shows a typical BASIC program 5 REM : X/Y PLOTTING ROUTINE Sir—Here is a low cost, easy to make project for illustration, and the following notes apply: 10 13=61340:Q=61342 for use with an X/Y plotter, that can be con- 5-30 Initialisation of the PIA (A and B) for 15 U=61344:W=61345 input. nected to the expansion interface of the UK 17 POK EU + 2,255:POKE W +2,255 101, or virtually any other micro. VIA (A and B) for output. 20 POKEP+1,0:POKEP,O:POKEP + 1,255 The system consists of a flexible arm, 40-180 Loop for storing data in memory. 30 POKEQ +1,0:POKEQ,0:POKEQ + 1, 190-280 Loop for playback to X/Y 255 equipped with two linear potentiometers and a recorder. pointer. This pointer moves over a limited sur- 40 INPUT "READY FOR START";A$ If the digitiser is used with the UK 101, it face of 20 x 20cm. The voltages, generated by 45 R=5000:S=6000 may be used with the PE-Expansion Interface 50 FOR N=1 TO 200 the movement are a measure of the position of published in Jan-July 1981. the pointer. Those potentials cannot be used 60 POKEP+ 1,60:POKEP+ 1,52 I do not use the internal A/D and D/A con- directly for X/Y plotting, because of their non- 70 V=PEEK(P)/100 linear output. verters, because I wanted a binary indication 80 POKEQ + 1,60:POKEQ + 1,52 A solution of that problem is found, by the for the D/A output and also there is only one 90 H=PEEK(Q)/100 application of the formula, which gives the output in the interface. You will find the 100 L=150 schematics joined. relationship between X, Y and the angles of 110 Y=L *COS(V)+L*COS(V+H):Y= rotation V and H. The potentiometers must be of good quality INT(Y)+255 and very linear. A resolution of approximately If now the analogue values of these angles 120 X=L*SIN(V)+L*SIN(H + V):X= 2mm is possible on a surface of 20 x 20cm. INT(X) are translated to digital, the calculation with a During storing in memory, the values of X BASIC program becomes possible. 130 PRINT X,Y and Y are continually displayed, and must be The BASIC program can be perceived as a 140 POK PR.V integer, positive and between 0 and 255. 145 POKEU,X:POKE W,Y limited loop with continuous conversion, so The value of L (line 100) is a multiplication 150 R=R+1:5=S+1 that the manual movement of the pointer can constant to certify an optimum sweep between 160 NEXT N be digitally stored in memory. It permits also 0 and 255. 180 PRINT"END OF LOOP - direct writing to a high resolution display. The number 255 (line 110) is added to in- 190 INPUT"DO YOU WANT A vert the value of Y, which is negative in this PLAYBACK";B$ area. 195 IF BS="Y" THEN 210 Line 50 in the program is the number of 200 IF BS="N" THEN 40 points you wish to fix. The movement of the 210 R=5000:S=6000 pointer shall not exceed 3cm/sec. 220 FOR N=1 TO 200 Line 255 defines the speed of playback, and 230 X=PEEK(R):Y=PEEK(S) 240 POKEU,X:POKE W,Y 250 R=R+1:S=S+ 1 Prototype digitiser 255 FOR D=1 TO 50:NEXT 260 NEXT N 270 PRINT"END OF PLAYBACK" 90° 280 GOTO 190

Table 1. Suggested

200mm software for calculating Potentiometer • Coupling piece the angular co-ordinates VR1( V) --Al alloy or PSU brass tube Potentiometer VR211-1)

Fig. 1. Mechanical construc- r tion of the digitiser

Wooden board Fig. 2. Sample of handwriting traced and stored from the digitiser

InE1560Pj

Zz-f/7

400mm

Practical Electronics February 1985 65 _ _ I 2 I

* BAKER * 0 0 0 0 .. 01 GROUP PA. DISCO APAPUFIERS post £2 150 watt Output, 4 input Mixer pre-amp. Illustrated £99 150 watt Output, Slave 500 rm.,. Input 3 Speaker Outputs .. ... £80 • • • • • ••••: • : 4/• % 150+150 watt Stereo, 300 watt Mono Slave 500 rnv. Inputs £125 150 watt PA Vocal, 8 inputs. HigNLow Mixer Echo Socket £129 100 watt Valve Model, 4 inputs, 5 Outputs. Heavy duty . .. £125 14Y 1 C So. • • 60 watt Mobile 240v AC and 12v DC. 4-8-16 ohm + 100v line £89 go o • • Reverb•Unit for Microphone or Guitar £35 PP El. s • s•iP ••• Electronic Echo Machine for mic/guitar £85 PP El. Deluxe £95. BAKER LOUDSPEAKERS Post £2 each Type Model Size Watts Ohms Price P.A./Disco/Group DG50/10 10 50 8/16 £18.00 and MICROPROMPT Midrange Mid 100/10 10 100 8 05.00 Hi-Fi Major 12in 30 4/8/16 £16.00 depends on the type of X/Y recorder (graphic, 1/151.1 Hi-Fi Superb 12in 30 8/16 f26.00 scope, screen). D/A FROM VIA P.A./Disco/Group 0G45 12in 45 4/8/16 £16.00 CONVERTER PORT A Hi-F) Woofer 12in 80 8 05.00 Hi-Fi Auditorium J. Ockier, D7) 15in 60 8/16 £37.00 P.A/Disco/Group DG75 . 12in 75 4/8/16 f20.00 Belgium. P.A/Disco/Group DG100 12in 100 8/16 06.00 TO X/V P.A./Disco/Group DG100/15 15in 100 8/16 £35.00 RECORDER DISCO CONSOLE Twin Decks, mixer pm amp £145. Carr £10. Ditto Powered 120 watt £199; or Complete Disco 000. D/A FROM VIA 120 watt £300; 150 watt £360; 300 watt £410. Carr £30. CONVERTER PORT B DELUXE STEREO DISCO MIXER/EQUAUSER as above plus L.E.O. LCOosorJ 07) V.U. displays 5 band graphic equaliser, left/right fader, switchable inputs for phone/line, mike/line. Headphone Monitor, Mike Talkover Switch £1 24 PP E2 Fig. 3. Block diagram of principle As above with 7 Band Graphic 038.

P.A. CABINETS (empty/ Single 12 £32; Double 12 08. carr, £10. IMTH SPEAKERS 75W £54; 90W E73; 150W £82; 200W 00. HORNBOXES 200 Wan £32, 300 Watt £38. Post £4. DO) A/D WATERPROOF HORNS 8 ohms. 25 watt £22. 30 watt E25. 40 wan CONVERTER TO PIA PORT A 03. 20W plus 100 volt line £38. Post £2. FOR V 07) MOTOROLA PtEZO ELECTRONIC HORN IWEETEK 339in square £6 100 wens. No crossover required 4-8-16 ohm. 73/8 x 34in. £10

CROSSOVERS. TWO-WAY 3030 cis 30 won 0. 60 watt 3. 100 watt Et CA2 ( %Tar 3 way 950 cps/3000 cps 40 wan rating. £4, 60 watt £650, 100 watt no. LOUDSPEAKER BARGAINS Please enquire, many others in stock 4 ohm, Sin. 7 x Oin. 050; 6/12 in, 8x 5in. O. 8i0. 0.55. 6/12 in. 25W 050. II ohm, 25/8in In. 12; 5x 3in, 6x 4in, 7 x 4in, 5in. f2,50; 61/2in, 8 x Sin 0; Ilin, AID TO PIA 0.50; 10in. £5; 12in. £6.130. 25W BM 80. hi-fl SOW L1250. CONVERTER r 15 ohm, 21/ein, 31/2in, 5x In 6 x Iin. E250. 61/20 IOW B. 8in. £4. 10in. £7. PORT B FOR H 3 ohm, 3m. £2; 5 x 3in, 6x40. 7 x 4in. 12.50.120 ohm, 31/4in dia. £1. 07) Make Model Size WattsOhms Price Post AUDAX WOOFER 5½in El GOODMANS HIFAX 71/1 x4 1/4in 100 8 00 £2 CA2 (5pTir r GOODMANS H13 WOOFER 8in. 60 8 £1350 El WHARFEDALE WOOFER 8in. 30 8 050 £2 Fig. 4. Block diagram of the CELESTION DISCO/Group 10in. 50 8/16 121 £2 AKAI WOOFER 120. 80 8 £16 £2 digitiser GOODMANS HPG/GROUP 12in. 120 8/15 00.00 0 GOODMANS HPO/DISCO 120. 120 8/15 00.00 £2 MK DISCO/GROUP 150. 4/8/16E44 E4 GOODMANS HP/BASS 15in. 250 8 E72 E4 GOODMANS HPEI/BASS 18in. 230 8 04 £4

METAL GRILLES Bin. £3.00, 18/n. £3.50, 12in. £4.50, 15i0. £5.50, " TO 01G TAL NPUTS FROM PIA 18in. £7.50. PORT 0r9 PORT 13,1 0 1 3 4 5 6 7 RCS SOUND TO UGHT CONTROLLER KIT Printed circuit. Cabinet. 3 channels. 1,000 watts each. Will operate from Hi-Pi or Disco. £19. Post Cl. 1614101 Ready Built Deluxe 4 Channel 4,000 wan sound chaser + speed + program me controls £69. Mk.2 16 programmes, £89. PP £2.

OFFSET MAINS TRANSFORMERS Price Post (Zero Y0 ,4 in Zero out/ 250-0-250V 80mA. 6.3V 3.5A. 6.3V 1A. 0.00 £2 350-0-350V 250mA. 6.3V 6A CT £12.00 Shrouded £14.00 £2 250V 60mA. 6.3V 2A. £4.75 El 220V 25mA. 6V 1 Amp £3.00 220V 45mA. 6V 2 Amp £4.00 Et Low voltage tapped outputs available Fig. 6. A plan view sho wing the 1 amp 6, 8, 10, 12, 16, 18, 20, 24, 30, 36, 40, 48, 60 £6.00 £2 TO CA FOR ditto 2 amp £10.50 3 amp £12.50 . 5 amp £16.00 £2 STARTPULS ANALOGUE INPUT VIA geometrics of the digitiser. Good 31-26-0-26-33 volt 6 amp £14.00 £2 . 0-50041 LOW VOLTAGE MAINS TRANSFORMERS £5.50 each post paid 0- 255VOLT quality highly linear poten- 9V, 3A; 12V, 3A; by, 2A; 20V, 1A; 30V, 1/12 A; 30V, 5A+ 17-0-17y, tiometers must be used to obtain 2A; 35V, 2A: 20-40-60V, 1A; 12-0-12V, 2A; 20-0-20V, 1A; 501/. 2A. £8.50 post 50p MINI-MULTI TESTER Fig. 5. The ADC channel a resolution of around 2m m Pocket size instrument op v. DC volts 5, 25,250. 500. AC volts 10, 50, 500. 1000. DC 0-25010a; 0-250rna. Resistance 0 to 600K. De-Luxe Range Doubler Meter, 50,000 o.p.v. 7 x 5 x 2in. Resistance 0/20 meg in FROM DIGITAL OUTPUTS VIA PORT A- X. PORT B- 5 range. Current 50pA to 10A. Volts 0.25/ 1000v DC. 10v/1000v AC. f25.00 post Cl Si 02 03 04 D5 D6 PANEL METERS 50pA, 100pA, 500pA, I mA, 5mA, 100mA, 500mA, +5V 1 amp, 2 amp. 5 amp, 25 volt, VU 21/4 0 2 x 11/4in. 3.50 post 50p

EQUIPMENT CASES. Black Vinyl Covered Top, Ali Base 4 x 21/2 x 21/4i0. U.501 6 x 4 x 11/2in. £3.60; 8 X 5 x 2in. £4.00; 11 x 6 x 3in. E5.50; 11 0/4 060 Sin. (9.00; 15 0 8 x 4in. £12.00.

ALI ANGLE BRACKET 6 . /34 v 3/4in. 30p. ALUMINIUM PANELS 18 s.w.g. 12 x 12in. £1.80; 14 x gin. £775. 6 x 4in. 55p; 12 x Bin. £1.30; 10 x lie. 969; 80 6in. 90p; 140 3M. 72p; 12 v 5in. 90p; 16 x 10in. £2.10; 16 x 6in. £1.30. ALUMINIUM BOXES. MANY OTHER SIZES IN STOCK. 4 x 21/2 x 2in. 0 20; 3° 2 x lie. El; 604 0 2in. £1.90; 8 0 6 x 3 7 Is 3 14 115 3 7 IV 13 2 in. £3.00; 12 x 5 x 3in. £3.60; 6 0 4 x 3in. £2.20; 10 x 7 x 3in. £3.60. 16 ci IC2 CD 4042 C 040 42 HIGH VOLTAGE ELECTROLYT1CS 32+32/500V E2 20/500V 75p 8+8/500V £1 32+32/350V 75p DO DI 02 03 04 05 06 07 32/350V 45p 8+ 16/450V 75p 32+32+32/450V £1.50 1 # 1), 2 I to I ti I I +1 32/500V 95p 16+16/350V 75p 16+32+32/500V .. £2

0620k SINGLE PLAY DECKS. Post £2. Make Drive Model Cartridge Price To X `I recorder GARRARD Rim 6200 Ceramic £22 or oscilloscope OUTPUT BSR Belt 12 Volt Ceramic £20 BSR Belt P232 Magnetic 08 BSR Rim P207 Ceramic £20 7 X 10k AUTOCHANGER BSR Ceramic £20 AUTOCHANGER GARRARD Ceramic £24 20k SMOOTHING 1000 CIRCUIT DECCA TEAK VENEERED PUNTH space for small amplifier Board cut for BSR or Garrard 183/4in. x 14 1/4in. x 4in. £5. Post El

156511 TINTED PIAST1C COVERS for Decks. £5 each. Post El 17 7/8 x 13 1/3 x 31/4in. 18 1/4 x 12 1/2 x 3in. 211,20 14 1/4 x 21/2in. 17 x 12 743 x 31/2in. 14 1/13 x 130 31/4 14/12 x 13 1/3 x 23/4in. 225/0 x 13 7y8 x 3in 1641 0130 4in 21 x 13343 x 4/12 in Fig. 7. Converting back to analogue for driving a plotter RADIO COMPONENT SPECIALISTS

Dept 4, 337, WHITEHORSE ROAD, CROYDON SURREY, U.K. Tel 01-684 1665 I ACCESS' Post 65p Minimum. Callers Welcome. VISA Lists 34p. Same day despatch Closed Wed. 66 * * * *

We're all "I'V critics. Whenever we moan from our armchairs we're carrying out the function, even though it's without an audience or a reward. I'm no exception. The other night I was watching a programme called "It'll Be V.T.'s views and opinions are entirely his own and not necessarily those of PE Alright On The Night". Presented by that brilliant jester, Denis Norden, it purports to be a collection of rejected sequences resulting from cockups by distinguished performers while recording their programmes. 'VE JUST had an idea. It doesn't happen through hell with the old girl. But we It is passable entertainment and Iall that often. So when it does I like to tell emerged with enriched minds. moderately funny. And, I suppose, acceptable somebody about it. Then there was old Bandy Andrews. I take to the gullible. But, because I have that kind I've been thinking that as we become more off my hat to him as well. He firmly believed of mind, I suspect that some of these boobs and more a buccov\-linishing civilisation, our that the only worthwhile subjects in the are specifically produced in order to provide a ability to communicate with each other, in curriculum were simple addition, division, relatively inexpensive spin-off. Alright, such the way we have been doing since the dawn of. multiplication and subtraction. These were conning is perfectly legitimate if it keeps mankind, is going to take a nasty knock. the intellectual vitamins on which he thrived. people happy and laughing. Here's an extreme instance. If and when Anyone who resisted the same diet was On the other hand, if these lapses from we reach the stage where we wish our beyond the pale. professional standards, which betray a rather workmates good morning by punching up the Finally there was Charlie Atkinson —long irresponsible approach to the job, are salutation on a keyboard—even though we since departed for that great big college of genuine, then ought we not to be just a little may be no more than an office apart—then calligraphy in the sky. It was he who trained concerned? sooner or later there can only be one conse- us to express our callow thoughts in Television is a voracious consumer of time, quence: total atrophy of the vocal chords. splendidly-rounded hands that were a joy to talent and, above all, money. Money, by the There's a lot in the old saying, if you don't behold. It was his good luck to pass on before way, which you and I help to provide by pass- use it you'll lose it. the ballpoint pen —which some people feel ing our crisp oncers across the Post Office And think what that could lead to in the killed individual style stone dead —came into counter every year. years after you and I are laid in earth. universal use. Thinking along those lines, it's not easy to The end of live theatre as we know it. The accept as a matter of mirth —perhaps even af- death of opera. The finish of slanging fectionate sympathy—the banalities which matches in the House of Commons. The such programmes offer. demise of spicy revelations at posh cocktail Sorry Denis. I'm sure it's not your fault. parties. Wholesale redundancy of bingo " We must all accept, in- callers. No more air-cleaning rows between deed embrace, progress * * * * married couples. No more whispered exchanges of sweet nothings between young as our sires did the According to a recent newspaper report, lovers. The start of mute TV and the passing wheel." the robots of the future are going to be a lot of radio. The amputation of vocal links with more cuddly. Apparently 'not tonight darling' people of other lands ... Try that little lot for will not be a feature of their synthesised starters. Of course, cynics will say that out of vocabulary. Sounds promising. such evil there comes much good. A spokesman for Cardiff University claims No more screeching prima donnas. The I agree that our education in those days that whispering words of love and affec- end of pompous party political gas. The boon was pretty elementary. But it had soul and tionate snuggling-up will present no problems of being able to get happily stoned at social . substance. It nurtured the development of for these romantic devices. functions without having to endure a load of latent talents and equipped us for the years Moreover, he promises us, they will be en- inconsequential chitchat. No more having to ahead. Some of us even got places on the dowded with limitless energy. Sounds even bear—though Mum might be upset—the strength of it. more promising. twice-weekly yap of Coronation Street. No But will there be anything in the circuitry more having to study impossible foreign * * * * to handle that well-known limitation—the languages. Enhanced matrimonial bliss, made headache? possible by the blessing of mutual silence. Leaving aside the emotional ramblings, Goodbye, the saints be praised, to Russel let's look at things in perspective. * * * * Harty and Michael Parkinson; and a merciful The computer, the microprocessor and all In the meantime, it is reported that deliverance from all that is worst in imported their derivatives, with us and yet to come, American 'iv. cannot fail to play an enormous part in our America has added a new category to census statistics:—Robots. future lives. Nobody but an idiot would deny * * * * that. We must all accept, indeed embrace, The first robot count is underway this progress as our sires did the wheel. month and will be aimed at robots on factory There's another aspect worth considering, But I can't help feeling that we still need assembly lines. The special census form also has a section to collect information about now that we're diving at an ever-increasing the basic support of established educational home robots. pace into the electronic age. How is the practices as a preliminary to hurling ourselves A more frightening rumour is the news keyboard syndrome going to affect the way headlong into the fresh technologies. There is that special robots are being seriously con- we educate our children? What, for example, no substitute for a grounding in the three Rs. sidered for duties as "personal" and home is to be the fate of the good old three Rs? Nothing can replace the human larynx as a If you can bear a moment of near-geriatric channel for human understanding. security guards. These robots are, it is nostalgia, let me recall Miss Richardson. She Someone is bound to say that writing as I claimed, programmed to deliver varying was a grey-haired lady who was totally do for an electronics journal I ought to be degrees of bodily harm; from simple electric dedicated to thumping the rudiments of good more aware of which side my wafer is dif- shocks to "dismemberment". English into the skulls of her elementary fused. Point taken. As I said at the beginning, It appears that the only obstacle is the expected multi-million dollar lawsuits that school charges. She had no time for anyone it's just an idea. But I still reckon that Miss could be lodged by injured parties.—A case unwilling to share her love of the glories of Richardson, Bandy Andrews and Charlie language and gems of literature. We went Atkinson still have a job to do. for Robot against Robot?

Practical Electronics February 1985 67 PRACTICAL ELECTRONICS PRINTED CIRCUIT BOARD SERVICE Printed circuit boards for certain PE constructional projects are now PROJECT TITLE Order Cost available from the PE PCB Service, see list. They are fully drilled and roller tinned. All prices include VAT and postage and packing. Code Add £1 per board for overseas airmail. Remittances should be sent MAR '84 to: PE PCB Service, Practical Electronics Editorial Offices, Spectrum Autosave 403-01 £1.83 Westover House, West Quay Road, Poole, Dorset BH15 APRIL '84 1JG. Cheques should be crossed and made payable to IPC Microstepper Magazines Ltd. 404-01 £10.74 MAY '84 Please note that when ordering it is important to give project Sustain Unit title, order code and the quantity. Please print name and address in 405-02 £2.82 Block Caps. Do not send any other correspondence with your order. Audio Signal Generator 405-03 £4.28 Readers are advised to check with prices appearing in the 405-04 £2.51 current issue before ordering. JUNE '84 Cross Hatch Generator 406-01 £3.52 JULY '84 NOTE: Please allow 28 days for delivery. We can only Simple Logic Generator 407-01 £7.73 supply boards listed here or in the November 1984 issue. EPROM Duplicator 407-02 £3.74 Alarm System 407-03 £3.19 PROJECT TITLE Order Cost Oscilloscope Calibrator 407-04 £4.23 Code AUG '84 FEB '81 Comm. 64 RS232C Interface 408-01 £3.02 Slave Light Dimmer 102-01 £1.88 Field Measurement 408-02 £3.19 MAR '81 „ 408-03 £2.76 27/28MHz Converter 103-01 £1.79 Digital Dice 408-04 £4.23 Microphone Mixer 103-02 £1.83 Simple Logic Analyser 408-05 £2.93 Period Power Tester 103-03 £2.25 Alarm System 408-06 £4.24 APRIL 81 408-07 £3.14 Speech Processor 104-01 £1.55 408-08 £3.23 Mini Drill 104-02 £1.50 SEPT '84 MAY 81 Parallel to Serial Converter 409-01 £2.92 Digisounder 105-01 £6.65 Through the Mains Controller 409-02 £2.88 Thermometer 105-02 £1.49 409-03 £2.71 JUNE '81 OCT '84 pH Meter 106-01 £2.06 Logic Probe 410-01 f1.90 SEPT 81 NOV '84 Horologicum 109-01 £3.16 Computer DFM Adaptor 411-01 £2.76 - 109-02 £3.11 DEC '84 109-03 £2.97 Ni-Cad Charger 412-01 £240 Analogue Frequency Meter 109-04 £2.87 JAN '85 109-05 £2.47 Ignition System Outrider Car Computer (Set of 2 boards) 501-01/2 £9.10 109-06 £2.28 FEB '85 Modular Audio Power System APRIL '82 Pt-1: Power Amp Board 502-01 £4.19 Med. Resolution Equaliser (UK 101) 204-01 £1.73 Spectrum DAC/ADC Board £3.69 Enlarger Timer 204-02 £4.02 502-02 AUG '82 Automatic Photographer 208-01 £1.94 Home Alarm 208-02 £3.21 SEPT '82 Waveform Digitiser 209-01 £8 24 PE PRINTED CIRCUIT BOARD SERVICE FEB '83 Please send me the following p.c.b.s. Radio Booster 302-02 £1.80 MAR '83 Order Code Quantity Price Into the Real World 303-01 £3.99 Accessory PSU 303-02 £1.35 41 Digit Frequency Meter 303-03 £3.69 APRIL '83 Phaser 304-01 £3.41 JUNE '83 Program Conditioner 306-01 £2.30 I enclose cheque /PO for £

SEPT '83 Name Guitar Active Tone Control 309-01 £2.27 Ground Communication System 309-02 £2.13 Address BLOCK CAPITALS PLEASE 309-03PLEASE £2.31 CAPITALS BLOCK

DEC '83 312-01 Expanding the Vic 20 £5.18 III NM IM MM M M M M M M M M MN NM .1

68 Practical Electronics February 1985 W 1 ,• •• • v1 ,. .• = m egiomm .••• ...••••• ••••••••-••••A an• ICC-L 1. 11 Z r-..i.J. E; t i -J.: 1 1. C.P.LNI 1L S G1 Re-chargeable Nickel-cadmium batteries in stock Ex-equipment but 10 CH A PEL ST REE T, LO N D O N, N W1 T EL: 01-72 3 87 53 1.6MB 8" FLOPPY DISC DRIVES - yen/ little used condition DEAC 10001)1( Button Stacks 6 cells - 12V Size 21/4 x diam Capacity IAH £3 inc. VAT Ip&p 25p1. DEAC New Stock 60000KZ Button stacks 3 cells - 3.6V Site 11/4 x 0/4" diam. •• • Capacity 6AH £1.50 inc (p&p 20p) • • After our recent sell-out of the DRE7100 FODs, we are pleased Also available - PCB's from which these to offer another bargain package as follows: BRAND NEW batteries have been removed containing American 'MEE Corp model M-700 DOUBLE SIDED 8" Disc Transformer, Diode rectifiers, smoothing Drives. Massive storage capability up to 1.6MBytes. Full IBM capacitors, DPDT Relay, fuses etc ONLY £1.50 compatability. External power requirements are -E5V at 12A each inc. VAT Ip&p 75p1 Complete board & and +24V at 1.1A. Full spares/back-up available UK (Elcoma- lotteries E5 Ip&p Ell ties). Current list is over £315.

* * STEPPER MOTORS * * * * NO W LOWEST PRICE EVER £160 - INCLUDING MANUAL INC CARRIAGE & INC VAT * * Brand new stock of 'ASTROSYN' Type 20PM.A055 stepper HEWLETT-PACKARD 141A Storage Oscilloscope. All these units are sold motors. 28V DC. 24 steps per rev. 15 oz -in torque 10OPPS HEWLETT-PACKARD 1707A dual trace 75MHz £750 in full operational * 19M BYTES WINCHESTERS * Body length 2/12 ', diameter 2, shaft 1/4" diam x 4,/4" spirally TEKTRONIX 454A dual trade 150MHz sweep delay.f.150- condition and threaded Weight 160, Price each £11.50 (p&p 50p) Connec- TEKTRONIX 453 dual trace 50MHz sweep delay f SAO- calibrated to spec. Now available again, UNITED PERIPHERALS 3100 tions supplied INC VAT TELEQUIPMENT D75 dual trace 50MHz sweep delay E450 All prices are subject Minidisc Drives I3x8" sealed plattens) capable of SONY/TEKTRONIX 335 dual trade 35MHz ponable. to additional VAT over 19MB. Sold in un-tested, un-guaranteed condi- * * STEPPER MOTORS * * TEKTRONIX 7704 frame and plug-in units, & carriage tion for just £125 inc VAT, carriage and copy of GOULD 05100013 dual trace 20MHz. ISecuricor) + Ito In stock -- used, but excellent condition, 4-phase steppers 50 handbook. steps/rev motor with (removable) gearbox giving a 300:1 reduction 6V DC operated Complete with a driver board requiring lust a single * * TEST EQUIPMENT * * * MULTI-RAIL LINEAR PSU's * by rail and pulse input Motor measures 1" x 2" diameter, gearbox MARCONI T11313A 01% Universal Bridge x 23/4" output shaft WAYNE KERR Bat Universal Bridge Recent stock of brand new COUTANT ESM-Series 3/16" Sold complete SULLIVAN R4000 Inductance Bridge Power Supplies at surplus prices. Model ESM15.2 Mb connections, CCT MARCONI TF2604 Electronic Multi-Meter giving regulated, stabilised DC outputs 5V m 15A diagram of motor, CCT MARCONI MEGA Audio Power Meters E85. and ±12V to ± 15V 1.5A each and an un-stabilised details of half-stepping fti MARCONI 10502 RF Power Meters DC-1GHz lOw fsd E350. 24V Oi 2A. 240V AC input. Measures 5x 8 x 11". Fully etc All for lust £8 we UNAOHM FORA PAL Colour-bar and Pattern Generator f275. enclosed. In original cartons with handbooks. £45 VAT Ip&Fi KORTING P2512 PAUNTSC Colour Panern Generator £275. each + VAT (p&p £21. ROHDE & SCHWARZ 'SOW AM Signal Generator 03-1GHz DATRON MODEL 1051 Digital Voltmeter SYFIW.M..1SOLATORS ROHDE & SCHWARZ Resonance Frequency Meter 470MHz-2 50/10. * SWITCH-MODE POWER SUPPLIES * SPERRY UNIVAC M4000 optoLsolator units providing 2KV of insula- ROHDE & SCHWARZ Polyscop SWOB It Fully tested and guaranteed PSU's now at LOWEST EVER tion between Modems and Terminals 25 way 'D' connectors BRUEL & KJAER Heterodyne Voltmeter 0 5-240MHz PRICES. Manufactured by FARNELL, GOULD/ADVANCE (RS232C Interlace) in and out Measures On 5ir 7" Complete with AIRMEC Display Oscilloscope 279, 4-trace, 14 x 0" CRT £195. 453 BOO 5V fi, 10 amps £18 12V 16A (110V in) 020 handbook 06.50 Inc VAT& p&p RIKADENKI 3channel Chart Recorder Model 13-341 454 E850 5V (ii 20 amps 00 5V iii 60 amps £35 BECKMAN TURNS * 125W MAINS INVERTERS * ** STEPPER MOTORS ** 19V (ni 15 amps £35 12V M 15 amps £40 All prices now include VAT, packing and posting COUNTER DIALS 12V DC Battery Input to 230V AC, Output Brand new stock of 'ASTR OSYN' bt 125 watts crystal-controlled 50Hz Type 20P M-A055 stepper motors. Miniature type (22mm diem) Counting up to 15 time-base oscillator, fully enclosed in 28V DC. 24 steps per rev. 15 oz-in * CENTRIFUGAL BLOWERS * urn "Helmets" Brand new wnth mounting instructions Only f2.50 blue-steel cases with integral 13A socket. torque le 10OPPS. Body length 'TORIN' Type U6261. 230V Cap'Start (supplied), very each inc VAT & p&p Dimensions approx. 4 x 6 x 10". BRAND powerful 1200 W, 3,000 rpm) centrifugal fans for large NEW. £50 VAT (p&p £2). 2f/2", dia meter 2", shaft /14 " dia m In rack cooling or enclosure extraction applications. * CROSS-HATCH GENERATORS * 4/14 " spirally threaded. W eight * MAINS STABILISERS * Overall dimensions 20012 ems, outlet 6 x 4 cms. LABGEAR COLOURMATCH CM6004PG. 16oz. Price each £11.50 (p&p 50p). Small quantity available of brand-new Gould BRAND NE W. Surplus stock. £15 each inc. VAT, p&p UHF teIevision pattern generators giving Connections supplied. INC. VAT. El .50. cross hatch, dot and grey scale panerns ECVN250A constant voltage transformers 190- Fully tested and guaranteed NOW JUST 260V AC input to 240V AC output Ii 250 watts £45 each VAT Ip&p LII f27.50 inc VAT & p&p * TEKTRONIX * * INSTRUMENT COOLING FANS * LABGEAR COLOURMATCH CM601000 Gated Rainbow colour * SWEEPERS * FILE MANAGER SYSTEM MODEL • Recent stock of BRAND NEW 5-bladed axial * pattern generators Cross-hatch/dot & gated rainbow IRGB) TELONIC 2003 System 800-1500MHz E325 4907 Option 31 (Third disc drive) • cooling fans measuring 31/2 x 31/2 o r * colour bar patterns £155inc TELONIC 942000 with 500-900MHz plug-in £175 4051 Graphic System compatible • (shmline tans) UNAOHM E06/34 PAL Colour bar & pattern gm n U75, KNIGHT K0-687 3-220MHz £150 GPIS (IEEE 488-1975) compatible • 230VAC 10 wens £7.50 + VAT * PLEASE NOTE All rhe pre owned equipment shown has been careloIN tested in our workshop and KORTING 82512 PAUNTSC Colour & pattern gen E275 115VAC 13wans 5.50 + VAT * reconditioned where necessary It Is sold in first class operational condition and most items carry a three Mail Order customers please add £2 50 postage each item months guarantee for our mail order customers we ay e a money back scheme Repairs and servicing to all * NO These fans are under l/2 RS price Postage each 50p * equipment at very reasonable rates PLEASE ADD 15% VAT TO ALL PRICES EQUIPMENT WANTED * Quantity discounts available for 10 Or

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BL O C K C APS PLE ASE O R TELEPH O NE US COUNCIL 1011 101 401111.011411101 COR1115001101K1 COl LIGE 0734 51515 OR British National Radio &Electronics School Reading,Berks.RG1 1 BR TELE X 22758 , CACC 124 HR SER VICE) N MI M O I MO M I N M M M EI MI N

Practical Electronics February 1985 69 SMALL ADS N O TI C E T O R E A D E R S The prepaid rate for classified advertisements is 36 pence per word (minimum 12 words), box number 60p Whilst prices of goods shown extra. Semi-display setting £12.00 per single column in classified advertisements are centimetre (minimum 2-5 ems). All cheques, postal correct at the time of closing orders etc., to be made payable to Practical Electronics for press, readers are advised to and crossed "Lloyds Banks Ltd". Treasury notes should always be sent registered post. Advertisements, check with the advertiser to together with remittance, should be sent to the check both prices and Classified Advertisement Dept., Practical Electronics, availability of goods before Room 2612, IPC Magazines Limited, King's Reach ordering from non-current Tower, Stamford St., London, SE1 9LS. (Telephone issues of the magazine. 01-261 5846).

BRAND NEW CO MPONENTS BY RETURN Electrolytic Capacitors 16V. 25V, 50V. HO ME SECURITY CONT. 047. 1 0, 22. 47 & 10 Mfds. - 5p. 22 & 47-6p. 100-7p. 150V-80). 220-8p. 150V-10p), 470-11p. 1400-16p), 1000/15V-15p. 1000/25V-25p. 1000/40V-35p. 4700V/25V-70p. Sub miniature bead Tantalu m electrolytic.. 0 1, 0 22, 047, 1 0 @ . 350, 4 7 @ 6 3V - 14p. When replying to Classified Advertise- 2 2/35V, 4 7/25V-15p. 70/25V, 15/16V-20p. 22/16V, 33/100, 47/6V, 68/3V & 100/3V-32p. ments please ensure: 15/25V, 22/2 W, 47/10V-35p. 47/160-80p. Sub mini Ceramic Caps. E12 Series 100V. 2% 70 pf. to 47 p1 -3p. 56 pt. to 330 pf.-4p. (A) That you have clearly stated your 10% 390 Pf- to 4700 pl.-4p. requirements. Vertical Mounting Ceramic Plate Caps. 50V. El 2 22 pf. to 1000 pf. E6 1500 pf. to 47000 pf --2p. Polystyrene E12 Series 63V. Horizontal Mntg. (B) That you have enclosed the right 10 pf. to 820 pf.-3p. 1000 pf. to 10,000 pf.-4p. Miniature Pol 250V Vert, Mtg. E6 Series. remittance. 01 to 068-4p. 1-5p. 15, 22-6p. 33, 47-10p. 68 - 12p. 1 0 - 15p. 1 5 - 22p. 2.2 - 24p. Mylar (Poi ) Film 100V. Vertical Mounting. (C) That your name and address is 001, 0022. 0047-3p. 01, 022-4p. 04, 05. 0 1-5p. written in block capitals, and High Stability Miniature Film Resistors 5%. E24 Series 0 51R - 10M0. - 1p. >1.a/ E12 Series 1R0 to 10M0. - lip. ID) That your letter is correctly ad- 1W E12 Series lOR to lays. - 5p. '.1A/ metal film E12 Series 10R-1M0. 5% -- 2p. 1%-E24 -- 3p. dressed to the advertiser. 1N4148-2p. 1N4002-4p. 1N4006-6p. 1N4007-7p. BC107/8/9-12p. BC147/8/9, 8C757/8/9, 8E195 & 7-10p. 8 Pin i.c's. 741 Op. amp.-18p. 555 Timer-24p. This will assist advertisers in proces- Dil Holders 8 pin-9p. 14 pin-12p. 16 pin-14p. LED's. 3 & 5mm. Red-10p. Green & Yellow-14p. sing and despatching orders with the Grom mets for 3mrn.-lip. Grom mets for 5mm-2p. minimu m of delay. 20m m. Q.B. Fuses 15, 25, 5. 1, 2, 3 & 5A-5p. 20m m. Anti Surge 100mA to 5 0A-8p. 20m m. Fuseholders P.C. or Chassis Mtg.-8p. Battery Snaps (pairs) PP3-6p. PP9-12p. 400rnW Zener diodes E24 series 2V7 to 33V-8p. RECEIVERS AND COMPONENTS Prices VAT inclusive Post 20p (Free over E5.001 THE C.R. SUPPLY CO. 127, Chesterfield Rd., Sheffield S8 ORN.

BOURNEMOUTH/130SCOMBE. Electronic components specialists for 33 years. FORRESTERS (NATIONAL RADIO HO ME SECURITY SUPPLIES), Late Holdenhurst Road. Now at 36, Ashley Road, Boscombe. Tel. 302204. Closed Weds.

SEC URIT Y / 01 111111=1 ALAR MS TURN YOUR SURPLUS capacitors, transistors, etc into cash. Alar m Syste ms Manufacturers of Contact COLES HARDING 8c CO., 103 South Brink, Professional Alarm Wisbech, Cambs. Tel. 0945 584188. Immediate settlement. FREE COMPREHENSIVE CATALOGUE! Equipment, for DIY • LO WEST DISCOUNT PRICES & the TRADE. Send • HIGHEST QUALITY EQUIP MENT now for our New 16. page Brochure, Full RESISTORS 1,000 MIXED Jkw. I/4w, V.tw, 2%, 5%, 10%. C. Film • FREE DIY DESIGN GUIDE of Information & the 4.3.45 inc 151'. D. J. 1100KER, Romney Marsh Electronics. CENTLRION • FULLY ILLUSTRATED Lowest prices. ALARMS Pennywood. Clark Road, Greatstone, Romney Marsh. Kent ORM 0000 TN28 SPII. • MICROCHIP CIRCUITRY VISA • Q UICK DESPATCH SERVICE CENTURION Dept PE • FULL INSTRUCTIONS Tel (0484) 93 Wakefield Road, BELLS TELEVISION SERVICES for service sheets of Radio, TV, SEND SAE OR PHONE Huddersfield. etc £1.50 plus SAE. Colour TV Service Manuals on request. C-TEC SECURITY, Dept PE 21000 HD5 9AB or 35527 24 hr. SAE with enquiries to B.T.S., 190 Kings Road, Harrogate, 60 Market St, Wigan WN1 1HX. W. Yorks. N. Yorkshire. Tel. (0423) 55885. Telephone (09421 42444 CFNIURION .5 o Registerea Trademark of Centur.on Alarms '

O R DE R FO R M PLEASE WRITE IN BLOCK CAPITALS Please insert the advertisement below in the next available issue of Practical Electronics for

insertions. I enclose Cheque/P.O. for £ (Cheques and Postal Orders should be crossed Lloyds Bank Ltd and made payable to Practical Electronics)

NA ME PRACTIC AL ELECTR O NICS ADDRESS Classified Advertisement Dept, Room 2612, King's Reach Tower, Stamford Street, London SE1 9LS. Telephone 01-261 5846 Rate: 36p per word, minimum 12 words. Box No. 60p extra.

Company registered in England Registered No 53626. Registered Office King's Reach Tower, Stamford Street, London SE1 9LS. 2/85

70 Practical Electronics February 1985 EDUCATIONAL/TUITION BOOKS AND PUBLICATIONS

FULL SIZE, top quality service sheets £2.50 + 1.s.a.e. CTV/ IMPROVE YOUR PROSPECTS Music Centres £3.50 + I.s.a.e. Repair data almost any named TV-Video £10.50 inc. circuits. L.s.a.e. brings any quote free with skills that employers want - learn magazine/price lists. T1SPE, 76 Churches, Larkhall, Lanark- the easy way with modem home study shire. 0698 883334. courses from Ideal SthouIs. MODERN ELECTRONICS FOR SALE Train for success in the fastest ever growing industrial sector. P.E. BACK NUMBERS Nlay 76 to February '82. ()Hers: Tadley COMPUTER PROGRAMMING 3743. The demand for Programmers is increasing constantly - don't miss out! PRACTICAL ELECTRONICS MAGAZINES. Believed to be complete For tree booklet write today to set From issue sine. (Ater, 01-642 4029. AC/DC CO MPONENT PACKS il IDEAL SCHOOLS OSCILLOSCOPES: Tektronix 516 (dual) £1411. 128117 £65, Du- e (Ref. PE2) Pack mont 511MIlz dual £140-12NI. Try-out welcome. Insured City Description Price IDEAL 6 G'ialt6:,r,'°nr(i. delivery + £7. P1)1'! 1/1)5 system £370. Teletypes £41/. No. S1NCLARE 111-316 1779. Tel: 041-248 5200 TF 11 12 RED 5mm LED £1.00 TF 12 30 500mz ZENERS 5% £1.00 IF 15 COURSES SPECIAL OFFERS. SE250C signal injector £2.20. 15 watt ampli- 50 1 amp Rect. Diodes in 4000 fier board £7.65. Antex C s/iron £5.95 P&P 40p. Thousands . series f1.00 of components in stock. Phone or write for price list. TF 16 6 1 amp Bridge Rect £1.00 SPECTRU M RADIO & ELECTRONICS LTD, 36 Slater IF 17 100 Transistor pads f1.00 FULL-TIME Street, Liverpool LI 4BX. 051-709 4628. TF 18 20 A/S Fuses 20mm £1.00 TF 19 10 3A Rect. Diodes £1.00 TF 110 2 ORP 12 f1.00 TRAINING MISCELLANEOUS 'IF 111 5 BR 100 DIAC £1.00 IF 112 10 BC109B D M COURSES IF 113 10 LC's all different D M ADAPTORS - Power supplies for calculators. TV games, com- IF 114 50 BFR 86 £1.00 puters etc. Send for details. RTE ELECTRONICS, Britania IF 115 12 8 pin DIL sockets f1.00 Mill, Rossendale. Lancs. BB4 RBA. IF 116 20 10mm Horiz. Pre set r 15 M O NTHS (10 values) £1.00 B-TEC NATIO N AL CERTIFIC ATE BURGLAR ALARM EQUIPMENT. Ring Bradford (0274) 308920 IF 117 10 Slide Pots - 3K in TELEVISION & for our catalogue or call at our large showroom, opposite all the same D M VIDE O SERVICIN G Odsal Stadium. IF 118 10 Mixed Pots f1.00 IF 119 10 Feed throughs f1.00 15 M O NTHS SUPERB INSTRUMENT CASES by Bazelli. manufactured from IF 120 25 Electrolytic Caps DIM IF 121 B-TEC NATIO N AL CERTIFIC ATE PVC. Faced steel. Vast range, competitive prices start at a 50 Polyester Caps f1.00 low £1.50. Punching facilities at very competitive prices. IF 122 100 Mixed Resistors - in CO MPUTIN G TECH N OLOG Y BAZELLI, (Dept. 23), St. Wilfreds, Foundry Lane, Halton, Incl. Wire Wound £1.00 Lancaster LA2 6LT. TF 123 100 Mixed Transistor Hardware £1.00 9 MO NTHS IF 124 25 5mm LED clips and rings £1.00 B-TEC HIGHER CERT (HN C) in THE SCIENTIFIC WIRE CO MPANY IF 125 10 BC 107 D M 811 Forest Road, London E17. Telephone 01-531 1568 C O MPUTIN G TECH N OLO GY IF 126 10 BC 108 £1.00 ENA MELLED COPPER WIRE & ROB OTICS IF 127 6 Green 5mm LED £1.00 S WG 1 lb 8 oz 4 oz 2 oz IF 128 6 Yellow 5mm LED £1.00 8 to 34 3.63 2.09 1.10 0.88 IF 129 150 Mixed nuts/bolts/washers/ • PRINCIPLES OF ELECTRONICS 35 to 39 3.82 2.31 1.27 0.93 • TELEVISION (MONO/COLOUR) 40 to 43 6.00 3.20 2.25 1.61 approx. self tapper ROO 44 to 47 8.67 5.80 3.49 2.75 IF 130 25 Mixed Electrolytics Axial D M • VIDEO CASSETTE RECORDERS & 48 15.96 9.58 6.38 3.69 IF 131 25 Mixed Electrolytics Radial ULM CCTV SILVER PLATED COPPER WIRE IF 132 50 Mixed Polyester Axial £1.00 14 to 30 9.09 5.20 2.93 1.97 IF 133 50 Mixed Polyester Radial £1.00 • COMPUTERS & MICROPROCESSORS TINNED COPPER WIRE IF 134 15 BC 337 • INDUSTRIAL ROBOTICS 14 to 30 3.97 2.41 1.39 0.94 £1.00 Fluxcore IF 135 20 500MA A/S 20mm Fuse £1.00 Solder 5.90 3.25 1.82 0.94 TF 136 50 Mixed Ceramic Discs £1.00 Short courses (from 6 weeks) Prices include P&P VAT. Orders under £2 add 20p. IF 137 50 Mixed Ceramic Plates O M with previous electronics SAE for list of copper and resistance wire. IF 21 200 47 pf 160V Polystone Cap f2.00 Dealer enquiries welcome. knowledge. IF 22 10 LM 3900 N f2.00 IF 23 10 Mixed OIL f2.00 Courses com mence COMPUTER LEADS, made to order. Please send S.A.E. with IF 24 5 4700 mf 25V Tag Elect 2"x1" f2.00 Jan '85, April '85, September '85. requirements to: S & A LEADS, 94 Ladies Grove, St Albans IF 25 10 1000 ml 63V An Elect f2.00 AL3 SUB. Prospectus from: IF 26 50 .022 ml 400V RAD POLY £2.00 IF 27 10 100 mf 250V Ax £2.00 ELECTRONIC ORGAN KEYBOARDS and other pans being cleared IF 28 10 2.2 mf 160V Polyester RAD £2.00 out as special oiler. ELVINS ELECTRONIC MUSICAL LONDON ELECTRONICS IF 29 10 VDR's - £2.00 INSTRU MENTS, 40a Dalston Lane, London E8. Tel. 111-986 IF 210 10 Mixed TTL 174 series) f2.00 8455. COLLEGE IF 211 4 2N 3055 H1RCA) f2.00 IF 213 200 CLEARING LABORATORY, scopes, generators, P.S.U.'s, bridges. IN 4151 Diodes £2.00 Dept: AA, 20 Penywern Road, IF 214 200 IN 4148 Diodes f2.00 analysers, meters, recorders etc. Tel. 0403-76236. London SW5 9SU. Tel: 01-373 8721, IF 51 100 White/Red 5mm LED £5.00 HEATHKIT. U.K. spares and service centre. CEDAR IF 52 50 BC 108C £5.00 ELECTRONICS, Unit 12, Station Drive, Bredon, Tewkes- TF 54 /12 KG Reel 22g ersin multicore £5.00 SERVICES bury, Glos. Tel. (0684) 73127. IF 55 10 2N3055 H1RCA) £5.00 IF 56 5 OCP71 £5.00 IF 57 3 INVENTORS 10,000 mf 40V Comp. grade elect 6.00 Think of something new? CABINET FITTINGS IF 58 720 /14 W Carbon film lw-10Mw Write it down! - ten values f5.00 Fretcloths, Coverings, Handles, Castors, IF 59 25 1,000 ml 25V Axial £5.00 A merican industry offers potential Flight Case Locks & Parts, Jacks, XLRs, IF 510 25 1,000 ml 25V Radial £5.00 royalties for your innovations and new Bulgins, Reverb Trays, P & N rnic Stands, products. We offer free confidential ALL PRICES INCLUDE VAT - ALL GOODS ASS Glassfibre Horns, BRAND NEW & NORMALLY DESPATCHED disclosure registration and initial CELESTION POWER BY RETURN POST. consultation in London regarding your Speakers TERMS: Cash with order. POST & PACKING: idea's potential value. Write without Please add 75p to total order. delay for your free information package. Send AC/DC ELECTRONICS A merican Inventors Corporation 30p cheque/ 82, Broad Street, Dept PT P.O. for I Ilust ra ted COMPONENTS Westfield, Massachusetts 01086 catalogue: Adam Hall (PE Supplies), United States of America. Unit G, Carlton Court, Grainger Road, DEPT P.E., 45 CHURCH STREET, Southend-on-Sea. A fee based marketing company. ENFIELD, • MIDDLESEX.

Practical Electronics February 1985 71 TREAT YOURSELF LOOK - IT'S HIS NEW YEAR SPECIAL! THIS NEW YEAR

Call in and see our new counternow open. We are the main stockists COMPLETE for 'BEARPARTS', the new 9.00 - 5.00 Mon -Fri & 9.00 -12.00 Sat Too far to call? Don't worry, export/mail name in electrical, SOLDERING KIT (For the Hobbyist/Electronics order is our speciality. Why not write and electronic and audio Engineer) find out more. components. FOR LESS THAN £10!! 24 hr onswerphone 1101C1 Ani for credit cord orders Interested? Send S.A.E. Comprises of:- Tel 0244 536699 and receive your • Antex Miniature 15W 240v AC Soldering Iron • Antex Iron Stand c/w Sponge • Desolder Pump SYSTEMS • 2 mtr Solder ONLY £9.85 • Desolder Braid Please add 80p P & P 'BEARPARTS' ELECTRONIQUE • 13A Plug + 15% VAT BEARPARTS sample pack. (U Y.) LTD Desolder

...... , CONTENTS OF PACK: Pump 26 Engineer Park, Sandycroft, BC 612 Transistor, Red LED, 1N4004 Diode, 11 646 Diode, 560pf 200v Capacitor,10k,150k Resistors, Deeside, Clwyd CH5 2QD. Soldering 2k Multiturn Potentio meter, 4BA Crimp Eyelet, Tel: (0244) 536700. } 1Rubber Grom met, Instrument Wire, Sleeving. Iron Stand c/w Sponge Iron 88/72 NOTE PIANOS BAND-BOX t 1 I . i'i LII--1 C SPECIALISTS SINCE 1972 PROGRAM MABLE BACKING TRIO Using Patented electronic technique to give 7,7, a'A MASTER RHYTHM advanced simulation on Piano Key Inertia. THE CLEF CMS PROGRA M MABLE DRU MS COMPONENT KITS - tilt including Keyboard ...... 88 NOTE £266 .- '''• 72 NOTE £234 As The above may also be Published ' purchased in four pans. i; in P.E ,,) SQUARE FRONT ' :L.. KEYBOARDS 88 NOTE £60 As Published in P.E. 4..1 . The FULLY programmable digital synthesiser . . ..,. 49 NOTE £29 THREE PIECE BACKING BAND that you can AFFORD 73 NOTE £50 Generates the sounds of three in- Twenty-Four e Rhythm program mable - THE NEW CLEF COMPUTER MUSIC SYSTEM JO NOTE £19 strumentalists to back Soloists Drum Machine with twelve instruments. is so user KEYSWITCH ITEMS DRU MS + BASS + KEYBOARDS programmable that you need a Eight sections are extended to 24/32 ALSO AVAILABLE BBC Micro to run it! 32 harmonically pro- measures for two bar program m ing. Over 3,000 chord changes 160 scores) on 132 different chords - 16 gra m mable oscillators. 32 programmable en- Sequence operation and instrument tone ALL PRICES INC. VAT. CARR & TELEPHONE ADVICE. chord sounds. Master Rhythm also velopes. 5 octave touch sensitive keyboard, adjust. COMPLETE KIT £79 S.A.E for full Specs & MANE PRICES. VISA-ACCESS- AMERICAN EXPRESS. Competitive quotes can be required. up to 4 OSC/ENVS per note. Real time se- STRING ENSEMBLE £198.50 given for export, Allow 114 days for normal despatch. FULL KIT £265 BUILT £370 quencing. Massive potential for future soft- ROTOR-CHORUS £98.00 MICROSYNTH P.C.B. & ELECT KITS ware. Complete syste m (without BBC Micro) CLEF PRODUCTS (ELECTRONICS) LIMIFED £86.90 £495 built. Phone or write for details. Modular PERCUSSION SYNTH P.C.B. & ELECT (Dept P.E.) 44A BRAMHALL LANE SOUTH BRAMHALL systems also available. KITS £97.90 STOCKPORT CHESHIRE Ski 1AH TEL 061-439 3297 .

OVERSEAS ORDERS INDEX TO Overseas readers are reminded that unless otherwise stated, postage and ADVERTISERS packing charges published in advertise- AC/DC Electronics 71 ICS lntertext 63 ments apply to the United Kingdom Adam Hall Supplies Ideal Schools 71 only. Ltd 71 ILP Electronics 4 Readers wishing to import goods from A.D.E. 70 the United Kingdom are advised to first Alcon Instruments . 64 London Electronic American Inventors 71 College 71 obtain from the advertiser(s) concerned an exact quotation of the cost of sup- Bensham Recordings 72 Mapplin Supplies 58, plying their requirements carriage paid Bi Pak 54 Cover IV home. B.N.R.S. 69 Marco Trading 46 Centurian Alarms 70 Phonosonics 63 Cirkit Holdings 5 P.E. HYPERCHASER Powertran .. Cover II, 64 Clef Products 72 14 CHANNEL PSEUDO INTELLIGENT I Computonics 70 LIGHT UNIT Ralfe Electronics 69 I *16 Programmes *Manual Rash Buttons C.R. Supply Co. 70 a* Manual/Auto Programme *Strobe Outputs R.C.S. 66 * Individual Dimming *Sound To Light Cybernetic Not just a light unit but a sophisticated & comprehensive effects unit. A full kit Riscomp 53 of parts including P.C.B., Face, Case, etc. Reprint of article on request. Applications 53 a &Alta a a PRICE INCLUDING P&P £84.95 Scientific Wire Co. 71 P.E. STAR DESK Electrovalue 58 Service Trading 46 8 + 4 CHANNEL LIGHT MIXING DESK *8 Channel Twin Preset Mixer *Strobe Outputs G.C.H.Q. 20 Skybridge 20 *4 Independent Channels *4/8 Channel Sequences *8 Programmes *Manual Rash Buttons Grandata 53 Swanley 63 *1KW Output/Channel (can be boosted to 2KW/Ch) Greenweld 58 Systems Electronique72 81111118111111 *Timed Crossfade *Soft/Hard Sequence A truly magnificent unit ideal for clubs, groups, drama, etc. A full kit of parts inc. PCB, Facia, Case, etc. Reprint of article on request.PRICE INCLUDING P&P £209 Henry's Electronics. 20 Tandy 19 BENSHAM RECORDING LTD Hewlett Packard 45 T.K. Electronics 6 327 Whitehorse Road, Croydon, Surrey CRO 2HS Hi-Tech 9 am-5 pm. Mon-Sat. Please allow 14 days for delivery ma. Components 26-27 Watford Electronics.. 2-3

Published on Jipproximately the 7th of each month by 11'(' Magazines Limited, Westover House, West Quay Road, Poole, Dorset BH15 IJG. Printed in England by Chapel River Press, Andover, Hants. sole Agents for Australia and New Zealand - Gordon and Gotch (Asia) Ltd.; South Africa - Central News Agency Ltd. Subscriptions INLAND £13 and OVERSEAS £14 payable to IPC Magazines Ltd., "Practical Electronics" Subscription Department, Room 2816, King's Reach Tower, Stamford Street, London SE! 9LS. PRACTICAL ELECTRONICS is sold subject to the following conditions. namely that it shall not, without the written consent of the Publishers first having been given, be lent, resold, hired out or otherwise disposed of by way of Trade at more than the recommended selling price shown on the cover, and that it shall not be lent, resold, hired out or otherwise disposed of in a mutilated condition or in any unauthorised cover by way of Trade or affixed to or as part of any publication or advertising, literary or pictorial matter whatsoever. 'al Ali new in the 1985 Catalogue From a gentle purr to a mighty roar, the tightly controlled power of the beast is yours to command! Our huge range of top quality electronic components at very competitive prices are all detailed in our catalogue, and with well over 600 new lines PROFESSIONAL QUALITY in our 1985 edition and many design improvements, it's well worth getting a copy. Here are just a few examples from the catalogue. HIGH POWER LOUDSPEAKERS (The items below are NOT kits). * Most phono and jack plugs now with integral strain relief sleeve - gold-plated A new range of superb quality loudspeakers. types also available from 14p (gold from 70p) * Virtually indestructible high temperature * Stereo Disco Mixer with cross-fade, talk-over, cue monitoring, aux input, voice-coil reinforced with glass-fibre slide controls. Only £58.95 (AF99H) * 100% heat overload tolerance * Advanced technology magnet system * Rigid cast alloy chassis * Linen or Plastiflex elastomer surrounds * 5-year guarantee (in addition to statutory rights) * 10-Channel Stereo Graphic Equalisers -3 models - basic; with peak level Available in 5, 8, 10, 12, 15 and 18 inch models with 80 and some 160 meter; and with spectrum analyser - from £77.95 impedances and with input powers ranging from 50W to 300W e.g. 5in. 50W 95dB 80: XG39N /160: XG4OT £17.95§ 8in. 100W 98dB 80: XG43W £29.95§ 10in. 100W 100dB 80: XG46A £29.95§ * Digital Delay Line permits Slap-back, Doubling, Flanging, Chorus and Echo. 12in. 100W 101dB XG49D £29.95§ 11 controls. Only £195.00 (AF98G) 12in. Twin Cone 100W 100dB 80: XG50E / 160: XG51F £31.95§ * Video Enhancer improves picture quality when recording from one VTR to Note - the output power doubles for each 3dB increase (ref 1W (i' 1m). another, and with TV's with monitor input. Only 28.95 (XG59P) * Detailed descriptions of the exciting new 74HC range of IC's which combine the advantages of CMOS and TTL. From 46p * Keyboards: sloping keys, two-tone grey, mounted in steel frame, very smart PRECISION GOLD MULTIMETERS cases (extra) available. 61 keys, only £33.95 (YJ12N) 79 keys, only £37.95 (YJ13P) * 1% Resistors now 50ppm/°C, 0.4W, only 2p each! * Auto transformers 120/240V 50VA, £10.75§, (YJ56L). 100VA £14.95§ (YJ57M). 150VA £16.95§ (YJ58N). 250VA £21.95§ (YJ59P). * Digital Clinical Thermometer. Only £13.95 (FK51F) • ) 4 4 ,

A new range of very high quality multimeters offering truly amazing quality at the price. Check our 1985 Catalogue for all our other fascinating Pocket Multimeter, 16 ranges, opooniv DC/AC £6.95§ (YJO6G) new lines. M-102BZ with Continuity buzzer, battery tester and 10A DC range, 23 ranges, 20,0000N DC £14.95§ (YJO7H) M-2020S with Transistor, Diode & LED tester and 10A DC range, 27 ranges 20,0000N DC £19.95§ (YJO8J) MrANESS M-5050E Electronic Multimeter with very high impedance, FET input, 53 ranges including peak-to-peak AC, centre-zero and 12A AC/DC ranges £34.95§ (YJO9K) Pick up a copy now at any branch of W.H. M-5010 Digital Multimeter with 31 ranges including 200 and 20p.A DC/AC FSD 1! Phone before 2pm for Smith or in one of our shops. The price is ranges, continuity buzzer, diode test, and gold-plated PCB for long-term same day despatch. still just £1.35, or £1.75 by post from our reliability and consistent high accuracy (0.25% +1 digit DCV) £42.50§ (YJ10L) Rayleigh address (quote CAO2C).

N.B. All our prices include VAT and Carriage. A 50p handling charge must be added if your total order is less than £5 on mail order (except catalogue). Post this coupon now for your copy of the 1985 catalogue. Price £1.35 + 40p post and packing. If you live outside the U.K. M APLIN ELECTRONIC SUPPLIES LTD. send £2.40 or 11 International Reply Coupons. I enclose £1.75. Mail Order: P.O. Box 3, Rayleigh, Essex SS6 8LR. Tel: Southend (0702) 552911 SHOPS • BIRMINGHAM Lynton Square, Perry Barr, Tel: 021-356 7292. Name • LONDON 159-161 King Street, Hammersmith, W6. Tel: 01-7480926. Address 1 • MANCHESTER 8 Oxford Road, Tel: 061-236 0281. • SOUTHAMPTON 46-48 Bevois Valley Road, Tel: 0703 25831. • SOUTHEND 282-284 London Rd, Westcliff-on-Sea, Essex. Tel: 0702-554000 Shops closed all day Monday. • PE 2/85

Indicates that a lower price is available in our shops. All offers subject to availability. Prices firm until Feb 9th 1985. ofess

Once again, Powertran and E&MM combine to bring you Specification versatility and top quality from a product out of the Memory Size: Variable from 8 bytes to 64K bytes. realms of fantasy and within the reach of the active musician. Storage time at 32 KHz sampling rate: 2 seconds. Storage time at 8 KHz sampling rate: 8 seconds. The MCS-1 will take any sound, store it and play it back from a keyboard (either MIDI or Iv/octave). Pitch bend or Longest replay time (for special effects): 32 seconds vibrato can be added and infinite sustain is possible Converters, ADC & DAC: 8 bit companding. Dynamic thanks to a sophisticated, looping system. range: 72 dB. Audio Bandwidth: Variable from 12 KHz to 300 Hz. All the usual delay line features (Vibrato, Phasing, Flanging, ADT, Echo) are available with delays of up to 32 Internal 4 pole tracking filters for anti-aliasing and secs. A special interface enables sampled sounds to be recovery. stored digitally on a floppy disc via a BBC Programmable wide range sinewave sweep generator. microcomputer. MIDI control range: 5 octaves. The MCS-1 gives you many of the effects created by top +1N/octave control range: 2 octaves with optional professional units such as the Fairlight or Emulator. But the transpose of a further 5 octaves. MCS-1 doesn't come with a 5-figure price tag. And, if you're prepared to invest your time, it's almost cheap! Digital Delay Line

troduced in 1982, Powertran's DL has brought digital quality ffects to thousands of 'clans. Still available in at only £179.00 + VAT.

Write or phone now to place an order. VISA Powertran Cybernetics Limited, Partway Industrial Estate, Andover, Hants, SP10 3PE. Telephone: 0264 64455 POWERTRAN cybernetics ltd