functiongenerator

soldering -ironregulator

NiCad-chargertimer

ELEKTORA./

POWER

0A.4

0

FREQUENCYIC Hz

ICC! Hz1 kHz ti

Hz tO kHz8

OUTPUT

41101.111111.1111.11111111momiiiimmiluniiniiiiiiimmut

UNEARI Ce CPUs74 SERIES

750 030751 0.33745 0_33745 0307404 036745 0-30745757759740574107411741274137414741674177537021742271237457426742774287430743274337437745743974437441

74434.74447446744647407,0744375)74517453745475374707472747374747475747675)7481

0.400100.300300.300.330300.500-700.360 400_309600360.360.400.400320930330360260300.400100.400.300.701401.101.031.00

1..480.50%0.380%o.ssasa0460.450520100.46OAS1.730

74134 1.4874244 1-5755 1.10746 0.574% 2-1071934 0367481 0.7074924 0.70753A 11.557494 1.107458 0.1017496 0.607437 7-1074100 1.9074107 115074109 0.7574110 0.7574111 0%74115 1.7074118 1.1074119 1.7074120 10074121 0.5574122 0.7074123 0107415 0.1674125 035urn ass74132 0.7574135 0,7074141 0.8074142 7-9374143 - 23074144 27074)45 1.1074147 1.707415 1.4074150 1.7574150 0.7074153 01074151 1.40741% 0574155 03074157 0.00741% 1.75741613 1.1074161 01074162 1-1074163 1.1074164 123741% 1.107411E6 1-4074167 4.0174170 20074172 42074173 1.4074174 1574175 1.0574176 10074178 ISO74179 15074193 1.0074181 3574102 1.4074184 19070554 1.9374191 13074191 1.3374192 1.1074193 1.157415 1.10741% 093741% 13374197 1.1074138 220741% 22074221 1.1074251 1.487459 1.507455 0.9374273 20074276 1.4074273 1.7074279 0.937063 1.06742% 3.2074750 0%74293 0907558 19374351 25743654 0937454 010743674 0.93742634 0.7074376 11074.390 1.10

74.37400759374430

1.201.101.201.40

7415 SERIES

741500 028741401 028741502 0.2874503 026745.504 028745.548 05741538 023741509 0.5745)0 923741511 023744.332 0.2374513 0_34741514 0.52741515 02374152) 023741521 05741522 05745.524 050741526 005741527 02374528 0575533 05741532 0.28741533 028741537 0574533 023741540 028741542 0416741547 0_90741.548 OSO745.551 033741554 0.31741.5% 0307414734 0307415744 038711575 0.48241.529A 0.43741578 0.42741583.4 0707415E5 0_8074156 0.36741593 054745591 0.93741592 0.40741593 0547415358 0 7574155 0907415107 0.437415109 0.43741_5112 01574/5113 0707415114 0.457415122 0.707415123 0574051241629

7451.40125

0.507415126 050701.515744.5133 050755136 OAS7415138 0.607415133 0907415145 1.107415147 1.75745143 1.407445151 0.707415152 2.03741515 0.7074/$54 2.007415155 0.707415156 0.707415157 0107415158 0.7074151604 0657531614 0.7574151624 0.7574151634 0.757415164 0.757415165 1.30741.5165A 130741-5151 13074151E8 1.307415170 1.2074L51734 1.107415174 0.757415175 0.757415181 2.007415)40 1.937415193 0.907415191 093715192 093745153 99074151944 0757551954 0.7574151% 0937415197 050755221 190741510 0907415241 09374055 0.507415243 0937415244 0.907445245 5607415247 1.1074525 1.1075525 1.107415251 0.75741 5x3 0.757415256 0.907452574 0.707415258.9 0.7074.10w.47415263 0.757415261 1207115335 0037415273 1.25741559 0.707.022E0 1.90711.32E3 0.16741.4Z0 055745292 9.43741583 093741525 1.40741557 5.1:07415293 1.03741559 2507415231 3.70741.5324:54

3_502901201.20210110193

5200.520520501.001.100.751.10

74453037415362741535374153567415333741536174153557415366741.6357744.570744.53737414374744_5335741.5377

7413378 1.107415379 1.407415381 453745330 0537415350 1.1074153564 1237415393 1.40711540 1.93741.5.115 1.407415467 1.407414540 1.407415541 1.40741.54-41 7.03755510 19937415612 19.007415626 2257115E02 225741.5629 1.407415E40 3.03MICA* 1 3.37415E41 2.37415642 2.507415612-1 3 CO7415603 2.5374145.07-1 3-48744..V54 3.537415E46 20374156441 4.3741-5E5 0571156% 0.937415570 1.93715.590 370745E64 6507415E87 0574522 6_5374C53 65074055 6_5074CMS 6.50740928 6.934000 SE RIES

53143020564707533433340104.3114312.431343144)1543164517431840194CQO415143724323402440:64,32640274029icrza00304031403240334034433543354037403803551401249554443464046404740484049409340514055334:st5764056axe40E0406340%567433356743%43E957040500724.373407543754077437547615E040265.06ACE95935344%405057456£574001 0.364932 03503 0454 09645)5 3 60455 0.9044-507.450 03545136451460

11012451346144515461645174518451945204E2140M4576462745.445254531

021024050.700.50.4001596000.5.24

0.369100.700.380.5093DEO0200.930.700300.480240.930.409630.750.51.51.51752_5)0.702531.101.032-539E00550-530.60_601930.5)0.600550_50350.469E00.630.930.50.664.50.700E60.402.3)0.5024

0.240_240-240_240.240240550250.250-240250_600.751200_350900.900.52730.75090

1270.55056

1.61.101.1007_230.430-50.51.150.60.700.E00.551.000_75

4532 0.65.t.i1 IW4535 2704538 0.754539 0.754511 0.934543 054%1 1.035-5 24045E5 054556 0.504%7 2.404560 1.4045% 1.40455 240455 1.700072 0.4544" 0934564 0.484755 0.604724 10014411 1.5014-112 7.534472. 3.0014419 28)14.693 4201.4..5 4_501454X4 69014.-9 2.0522100 1.5022101 7.0351-5 7.004514 0.434.3CE5 1.274357 0364568 .4043100 1

0.53

43101 15515 1.3343103 2.0343104 11041105 1.5340106 0.485107 05540103 12040109 0.E043110 2.543114 2_255147 193401E3 1.0340173 1510174 1.5.0413175 1.54015 1.0040133 1.0340154 1.0340244 1.5043241 1.504057 1.805373 1.9740374 1.93WC% 0.75WC:97 0.759598 0.75Full rangeof 74S Er74HCseries instock.Ask forfull list.

zif sockets21.2.1: Tin

5.507.038.00

1116 ECL

MEM

AD7581 15.00ADCOE03 11.90AM79100C 31.00AN1013 2.03451-5050 1.43413-1270 7.505113.150 3.504538910 4905346912 5.0CA3019A 1.00CA30230 1.10CA3346 0.70CA3359 320CA3090 150CA3000E 0.70CA356 0.600CA336% 210CA309040 3.75CA3135 0535431307 133CA31406 0.45CA31407 I.3CA3146 2-25CA31608 052CA3161E 1.83CA.3I 4.40CA316% 2.70CA3243E 1.50CA3290G 2.701371302 1260DACOECO 2.25DACC603 25D503 - 393HA13S9 1.90IC12105 6.75IC17611 295ICL75) &CO1517653 2501CL9338 3_03IC7.02168 22.101517217 7.50/503755 1.03151755 1.40LC71201 3.03157133 3.03LC7431 3_50157137 3.521141347 15011351 0 6)LF353 0.510-355 090LF301141 0.5LF-57 1.00113331 3.00144105711 4.501.15014 0331.3.907 0.45103300074 0.7511.010 2.541311 0.ea15.1318 1701.419 1513.4324 0.45LIA3347 1.151.443352 1231.14335 1.6011.13313 0.401.1.110 0.031.1,615841 053L.5377 21014:3544.8 1.500.133574 1206 M..141,61 1.700,13E2 2.0004333 3.25LM294 2201.5395-1 1.0311035 2.701.405 1.800.100001 1901.10133274 1.1047.L.M0szt9

30.7505Lma12.5709 0251,.51710 0.48

151711 1.3L517-5 0.61.0175001 103LL1733 0.5101741 0.1617.1747 0.70LIAM 0.3315.57011 4.93180014 1.501.311801 3.03

1.11.11830 2531551971 3.3'LM7872 3.001031396 6001.141889 4_511705117 3.00180372 0350.15100 0.801703303 1.001013311 LBO1843914 3.8)1843315 3.401.103316 3.401.413600 1.508515131 2_30

0 5371275151SL

2034 .53

1.533733 4007.51310 1.5714C1413 0.93MCI445 250M(1455 0.503C14351. 230MC156 0.70705340 220l4C3101 0.317,15633 0.655.101001 3.40034404'740 9007.455035 7.931441.320 5.0381152 4.00M00515211. 393

54%55 02274666 0-674554 4936506 123NE566 15055567 1250E570 46074571 10315532 0.937436533241 1.8)741053?75-E.14P 120?i5635AP 150OP43754 500P11024 5.00RC4135 055654151 203RC4148 1.50604558 0555559 220550240 055991903 16.00SA01024A 115SFF95364 8_0051.493 1035707631371 3_035117602374 13574763351 1035777011575 2.1557476477 800snaszas 4.00500556 493517E650 15SP056Al2 7.5SF4815 750147120 123TA130 140747204 150TA7156 0.937007722 1507,473:0 1_53

VOLTAGE REGULATORS1A FIXED VOLTAGE PLASTIC 70270

VE5V6V8V12 V15 V13 V24 V

7835 0.4879:97573 tum7812 cuss7575 aJmn's 0.50825 030

-YE

73057908791279157915

71324

0.50050oaooso050oao

43.5.1

14 FIXED VOLTAGE PLASTIC TOW

5 V 5106 0336 77sCa.7.411 13.30E m.ce ow-4- 70,12 0.33

OTHERREGULATORS

SWITCHINGREGULATORS

003000 1.40 !C00-000 2.531.04355 3.50 0=7 103731-105KC 544 1-40 30073012 693 11.457 3.0378005 9.03

RCM3'1° 2.53% 1_50

VARIABLE 14 250

15,531 TT 1.931003100 24011013377 25101350T 4.031.70354( 15.00

OPTO

REGULATORS

C75.47XC7 042579M312C

0535.752256.752.501.40

ISOLATORS1LD71 1.30 1141121L074 2-20 711113107725 1.00 711116MC52403 1_90 071377.4.0...,3 1.50 zom111111 070

DISPLAYS

0.700.700.701931.75

00704 RED 1.4001707 RED 1.40FNEL-57 140F740651117301.03F00507711175 1.03044674,91704 1.0070.51071.131707 1.037014055 1.75

M.A.. 44543PAL70:61054.59.1111311TIL7E)01730MARESIO4.447.8940

2.032205.70

190650

1902.502_53

DISPLAY DRIVERSa;e6

_511374L 753161;7!,4175UD1:5154

4 534503.503503.503203200.9)

0.5)290I-901.801900.70070

OTHERS24.1777 0.505705 10BPN21 29)

-P71 1.

C R 4112(R,37OP 4151

1.201_Z)1.20

TakA, tax, 448180,51 127199800 0.80TBASIO 0.93534820 0.911890230A 0.75

784950TE1450

2257(3109 5 037C4210 350TCA203 357TCA940 1.75TDAIC04/4 5.001041010 25TE1A1022 457TDAI024 1.1017911705 3.5704.290 33TDA2003 1501042300 2405/42305 1.23104.520 3211792030 1.931114.541 4.031092931 493TDA2593 5.03TDA2551 7.007043560 9.935743310 7.501797000 350TEA1002 7.035.1361CP 0.4071.4" 0.4011.064 0.90non 0.4011.072 0.70-rune 1.105031 035TILED 0-5511.033 0.75TU384 10011.094 20071170 0.507143)C 1231/4A1033.9 5135LIA759 320U42240 15U44170 1.701.5114931A 5.501.11.62001A 050LW/2032A 0.9001700034 093U1N2:044 093415068 290ULIC332U10230301.412E04 190UPC575 275UP554-1 2110UPC115*1 143UPC110501 3.93XR210 4.00XR236 4.00X02707 3.75X05211 5.75X02216 6.7555240 121214404 120211414 093271419P 1.75278905 15514245 1.30vans 350771553 3.0054427/38 6.005442369 4-5754442551 22554417E 9 -CO7344636 7.50514433CP 3 0)211113346 2.032461040 6.532719134.1 23.0328 A2105. 550

*ATTENTION*ALL PRICES ARE

SUBJECT TO CHANGEWITHOUT NOTICE

SCRS LOW PROM DIL SOCKETS BY TEXAS

10Efaa5525CQA502363:068025E10953L%2534MOB36834

8335

6.5012.5.03 SO

15-005.538-032.502-606_50

12.033358.0)

17.2016.0036 CO5.00

tee3.4 4.2)81085 6509CE6 MOO9339 17.50875

2P.O.A.5,151 9)631785163) 120077459336 12.00WO% 14-50£5) 2.83MCA 3.75259 05

SUPPORT DEVICES'.091 12.03

1112 8.03501 4.53520 3 006522 3.5T.46V 26066V-4 5.50E632 523t51,4 5506321 150EBEI21 2206623 12.-5C840 1755540 EXO650 11%

.553 250

6E52 2.53054 6-505551 8.030379 5.038151 853815 5078156 4.03506 2.25512 2.500216 1.60054 3008226 3_CD8228 2_709243 4_508250 960137514 5.038253(5 60095554C-5 5.5062E6 24.036157C-5 4.036259C 5 653575 nee43279 5-57Ms 7.50e232 450E283 4.500237 P.0.4.8980 119300500.

7;29 24 001159933 25 CO773011 tam71459514 14.432E34110 2.8)ZEC4P10 325(44A- 2.50MGACTC 3252004RT 6502E397AR7 LEOT.M.445:' 0 14.0317.159931 593Thism2 5.5ZECIADMA 993700.00/13 9.00

RAMS CRYSTALS I INTERFACES ICS231615)2)0127102210782111A-35211.4202114312114-4121475273 101)411615 20341165 17541113-3 5.0041E4.151711 5504164-15 55341m -2o 450441645 5.034632-20 2.5044316441.3 2-035101/5501 3.705516 650611EP-3 50061164.P-3 5506254-15 26.110S51-46

7451%745201752553415

3

6.004002535.034.003.50250103323

1501.60

3_502786_009.576.3

ROMS/PROMS232224510

1504ma751E07452574526874533774547374547474557074551

82523745573

825329625)8

4752-502032.031532-251702.254.754.036 531035.531.601.501.75

EPROMS

516 5V2515353532532-3325615032716-5V2716-553227324.27735-3327324.52761527256-302725625270542527152527128-30552716

3.53

450553

5526 503-m3505534_537.006.035 605 00

54 CO6.0314.60150316005.00

CRTCONTROLLERCR76027 18.03CR16645 9.03873364 LODV633S 3303EP30156 33.002.3357 35.00MPW5 6-511,143580441 7511405547 653SFF90.54 8.035059318 310311.15.44,7 14.00TMS3513 20.037015325 1500

15 901 70054570 SepCIA 60371 140616A103Y200pC)560 456461:510. 30071C4A 3597753525 13092444444 14071

%5:5: 4400

34.000. 6006.4 470, 70P6.4 5:00 9065A1CC0 75694 5071 95612A55(11)05651573Y 1306

7 290:0 130p112560 500-432z90 700

TEciiNom.vric Inert)

DISCRETEDISPLAYS

ZEDS125'RED 111.239 0.12GREEN111211 0.16YELLOW111212 020Rect LEDs

030550 1E0

10 LED000.0 100Barcraph.Reef 205Green 2.302°nt.220 0.1510..222 0.18111226 0.2211132 07511178 0551I315 1.20T001 12371

1411111M1111Turned PinLow Noble

Socket

BC1079BC10ES137103.-C

0141C161(177BC179C182/1C13.1!LC2124LC2130.C2141103270338C477131216778547/8

sarstac

18016020p400404030p30p159200

ID110016p1644369509

169

5 r,14,

30,0, 250

L,=/135668C55%CY71CY72131310132013513136

014130240S132448F565FE7F259F337FP9)481

18016024p36p30p75pEOp40040p40075075p40p50p4.0940p3641320

DC COM1ECTORS

22c7Ers kHz 1.031 CO MHz 27015:2 08-47 225210 MHz 226257613 MKT

11_12012.457E0 14Hz (S)

25025 7,11-12 2.502 652 MHz 2503.12 MHz 1.753.276 MR4 1.5035795 MHz 1.1334.00 Sltiz 1504.191 41144 2004.5 MHz 1934.90 M74 2.504.3152 0100 2.505-50 MHz 1.506.00 MHz 1.406.144 MHz 1.407_00 MHz 157.1E8 MHz 1.759_00 MHz 1508167 7000 1.751000 MHz 1.75105 WO 2.5310.70 M.144 150ILCO MHz 3.031200 MHz 1.501400 MHz 1.75143)8030: 1.6314.75550Hz 2_5015 CO 7.1144 2.03155 MHz 20317.734 03)4 2.0013.03 MHz 1.7018.0370H: 1.7018.432 MHz 1.5019933 MHz 15023.000 MKT 1.7524403 MHz 150483414, 1.75115 81440 250FX01030 12.03

DISCCONTROLLERSE2435272FD1771F0179181/17%1793f0FDA

C427932)027371401081ViC72743

6326.0350320.0320.032139322_0336.0232031903843

CHARACTER GENERATORS

PG3513LIC7 5)

60-3-25131-C7.00

101495464 12.005311656760 7.50574745262471

10.0313AUDRATE

GENERATOR81(14411 7.50CO446116 65347025 7.50

KEYBOARDENCODER

447-42375 11.50AY5-36E0 7.507443302 69074.3 6.50

UHFMODULATORS6 MH: 3.75

MR/ 4.50SOUND ErVISSON12 1100 1293

53%11 %COAM5510 3.50AME4525213-500002.5538351352264.53151 15903261532 15Amnioac 3193DACEOC91-V

28.43101.0131 6.03

0P32CA 3.53

043531 5.00D54630 1.40D56631 700105395 150056833 25136E835 1.50135530 25013201 457451436 091MC1463 0.60MC3446 2537.5353 457MC345 4.75MC3-05 0507.1515 25MC3-157 257,10454 3.3010.40044 3505(14411 9_0301(11412 75075407 0907515 0.9375109 1575110 0_905112 1.405113 155114 1.545115 1.4075121 1.40msz? 1.40751929 1575154 15751% 220516) 5.0075161 350751E2 4.0075172 35515 0.937515 0.6075183 aro75% 1.50551 0.5075452 0_9375453 0.7075154 0.7075483 1.505151 0_657550 0.5ST26 150179 1815 15203190 15ST97 1.203193 1591/55 1.403)1548 223811597 1.40811593 22)8115130 5909372 10392354 15957AP 1500,8 110

REAL TIMECLOCK

y(45lep 1.53545453174456 53515 547'...e4 53 50

TELETEXT -DECODER

5495320 6.005495133 7005495141 16.0151445353 900

UARTSA0,1101541 103AY -51013P 100COME017 32011552 150TR1002 3.03

RIME WRAP SOCKETS ST TEXAS

pn 300 18 00 50p 74 00 75014 Des 429 20 pet 60p 29 4.1-. 100,lap. 450 22 50 65o 40511 1300

15 Dr16 pr.

ZoTRANSISTORS8P592 518FYQBEMM.125017.13831M-.13031MJS1U55M.RECESMPF102MPF103241APP1C67.141341271P23C114137811P31C1141325waxTIPMC

309329919

Z5p

2250150p15p40p40p409939

40p45,,400809

1400

7_ w_.2_.14 54.1-0.0.0e41ta3 .97.0 1450 1750 250 2200 0350

!00 801 120.9 1500 )60p 1900E0500000 1200 1956 2400 320p 3400

200p

3904

EURO CONNECTORS

009 50,-0000441512 7 32 154 3000 50940000 2 32 000 3500 40098754e0 3 - 32.0000 459 -,400 2 . 32024000044 - 5c-1 -215 1151 7 21..*. 160p 1556IDMI 41617 31.wer 1700 1706017:416122,325551inn 2300 27502 s % 0.00 Arg R0 2750 32093.32 417 St 41,0 2600 33003 324004 An7 Pin 3756 40061 DC So A -8 3750

A C .... 350pFc 2 22 040 10.4004 00.0:10 00.009 -3.

MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON NW10 1EDSHOPS AT: 17 BURNLEY ROAD, LONDON NW10

(Tel: 01 208 1177 Telex: 922800)305 EDGWARE ROAD, LONDON W2

Sip

11141C

TIPC2CT1P47511541141551141135T1P295571P326526216321(2219A5402224V424131270615210306A7.53:6024564

150050060965p97p

1113p193p7009097040

390,330,334430950p33PYap600

n 040 70-, 9)

6041

2 34-r2283502zua-pa2A293ni,s2637732708192123866

i6VOW)V,6245V440718a. -,r292,6393285273012337040T4573

IXIOES

05127 12p 00203 00 540734 Sp00,47 10p 01.707 106 t k4036, 7 76aDApp 004 11/4914 49 3551012 17400491 96 .54146 40 ;7.5403'4 1461495 2, ZO31 2 - 5922

BRIDGES1457: 19p

700300

010 306

,',....1:Xii: 456 6.41000 10061107030 600 65050 120p10. 010 959 441001 1505/.44; '.' 100p 70.0707118095.4577, 60p 4094000 20420

5.404 D CONNECTORS

eza

fy.Ys 4/b 36 1lag 1.42 44435l674416o '70

1 No 2 slp 2.370W4xce 4000 100 60 53

wz Cotcins I,T. czzoT7 .5, Ceraas T,p. Cate03C54401.04014e.s.s. 4540

Ko1500

71601815

ea,

100s

4.0

1 :Co -ES,

l'ILFASE 111150p p&:1) VAT(Expoirl: no VAT, p&p ni Cost

Orders from Government Depis. & Colleges et,: welcome

Detailed Price List on reques![AL- jStock items are normally by return oi post

=1:M3rrS4

Elektor Publishers Ltd.. Elektor House,10 Longport, Canterbury CTi 1PE,Kent, U.K.Tel.: Canterbury (02271 54430. Telex: 965504.Office hours: 8.30 - 12.30 and 13.30 - 16.30.

Editor: P.V. HolmesAssistant editor: E.J.A. KrempelsauerUK editorial staff:R.E. Day. G.P. McLoughlin, L. SeymourOverseas editorial staff:P.H.M. Baggen, A. Dahmen, I. Gombos,P.E.L. Kersemakers, R.P. Krings,P. v.d. Linden, D.R.S. Meyer,G.C.P. Raedersdorf, J.F. van Rooij,G.O.H. Scheil,

Editorial secretariat:C.H. Smeets, G.W.P. WijnenHead of design:K.S.M. LValra,.en

Laboratory staff:J. Barendrecht, G.H.K. Dam, K. Diedrich,G.H. Nachbar, A. Nachtmann,R.A.F.M. Salden, A.P.A. Sevriens,J.P.M. Steeman. P.I.A. TheunissenPublishing manager:A.J. Brieley

Advertising manager:S. Brooks

The circuits are for domestic use only. Thesubmission of designs or articles to Elektorimplies permission to the publishers to alterand translate the text and design, and touse the contents in other Elektor publi-cations and activities. The publishers cannotguarantee to return any material submittedto them. All drawings, photographs, printedcircuit boards and articles published inElektor are copyright and may not bereproduced or transmitted in any form or byany means, including photocopying andrecording, in whole or in part without priorwritten permission of the publishers. Suchwritten permission must also be obtainedbefore any part of these publications isstored in a retrieval system of any nature.

Patent protection may exist in respect of cir-cuits, devices, components etc. described inthis magazine. The publishers do not acceptresponsibility for failing to identify suchpatent or other protection.

Elektor is also published in Dutch, French,German, Greek, Italian, Spanish, Turkish and(in part) Swedish in association with Alit omElektronik.

Distribution in U.K.:Seymour Press Ltd., 334 Brixton Road,London SW9 7AG.

Copyright 1984 Elektor Publishers Ltd.,Canterbury.

Printed in the Netherlands. ABC

news, views, people 12-18

electronic candle 12-22Has all the charm of the traditional item -without the drawbacks.

the XR2206 in the function generatorWhy this old IC is still the one to use for a new function generator. This articleshows how we have capitalised on the XR2206's good points and negated itsdrawbacks to provide a simple, but very effective, new function generator.

shorthand BASICMany computers provide a sort of shorthand to simplify and speed up the processof typing in BASIC programs. Here we provide the same facility for the JuniorComputer and other 6502 -based machines.

function generatorMade -to -measure sine, square and triangle waves are very useful for testing cir-cuits. This new function generator can provide them all but is neither expensivenor difficult to construct.

12-24

12-27

12-30

time switch 12-36Adds a touch of sophistication and user -friendliness to cheap battery chargers.

missing link 12-39

how to make your own PCBs 12-40

cumulative index 1984 12-41

musical greeting cards 12-44How to use them for something useful.

give your soldering tip a longer life 12-47A modern economy circuit that may increase the life expectancy of your solderingtip

computer -controlled slide fader 12-50This circuit rot only enables slide pictures to fade into each other on the screenbut can also be used for controlling the gating angle of other electrical appliances

slot -car controller 12-61Provides a power source and improved speed control in one small circuit.

microprocessor -controlled frequency meter (part 0) 12-64A look at the features of this sophisticated menu -driven frequency counter. Theconstructional details will be featured in next month's issue.

market

switchboard

appointments

readers' services

index of advertisers

12-66

12-71

12-75

12-80

12-82

A selection from next month's issue Al:' -controlled frequency counterII VHF. UHF TV modulator guitar preamplifier hybrid power amplifier rumble detector Commodore cassette interface

12 -OR

elektor december 1984 advertisement

liaz meat? atemttE34, February 1978Infrared Light Gate/ThrowingSons. Light on LEDs/Formant- the Elektor Music Synthesiser181/Slowort/off/C1.10S FunctionGenerator/ZenerTester/Develop-merit Timer/Experimenting withthe SUMP (4).

E38. June 1978114 GHz Counter/Constant Am-plitude Squarewave to Saw -tooth Converter/Servo PolarityChanger/ Monopoly Dice/ MiniCounterlDigital Clock Using theSC/MP/Programmable Call Gen-erator/TV Sound Modulator!Automatic Stereo Switch/TrafficLight Controller/Easy Music.

MS=E54, October 1979Touch Tuning/Battery Saver m -sedan ce Bridge/New Programsfor the SC/MP/Digital Rev Court-terADigifaradStiort-interval LightSwitchiPC8 for Variable FuzzBox/Gate-dipper/Strain GaugellPlayed TV GarnevPrograrnmableSequencer.

elektorott..cgior

E55, November 1979Topamp/Flash Sequencer/Elec-tronics the Easiest Way/Re-mote Control Motor Switch/Home Trainer/Fuel Economiser/I Played TV Games 121/Short-wave converter/lonospherei LowVoltage Dimmer/I See yourPoint/Servo-controlled Motor.E58, February 1980Aerial BooneriFet °comps inthe Fonnant/TV InterferenceSuppression / Elektor Voccder121/Aerial Ampfifiers/Digisplay/Analogue Delay Technology/Ex-tending the 1/4 GHz Counter/Digital Thermometer.E65, September 1980BK RAM +4.13 or 16K EPROMon a Single Card/Precision PowerUnit/Electronic Linear Ther-morneterfThe Josephson Corn-puterNOX Printed CircuitBoardrEjektor: Measuring Multi-path/High Speed Readout forElektenninal/Musical Box/Elec-trorytology/Curve Tra-...erUsingthe Vocoder.

E66, October 1980Programmable Slide Fader/TouchDoorbell/Switched Capacitors!More TV Games/The JuniorComputer Memory Card/RemoteControl Slide ProjectoriVideoPattern GeneratoriLCD TuningScale/Dual Slide Faders.

E67, November 1980An rpm. Indicator as anEconomy GuideiDraught Detec-toriHow to Recycle Dry CellBatteriesfEnergy Saving Know-how/Simple Fuel EconomyMeter/Automatic Pump Control/Long Life Technique in LightBurps/Automatic Curtain Con-trol/Fridge Alarm/Know the insand outs of your Central HeatingSystem/Energy Saving MotorControl/Coffee Machine ^ itsh/Operational Hours Counter_

E68, December 1980Canned Circuits: 23 of the bestentries which include MidnightRaid Detector/A Flash in theCan' / Canometer / Canine De-fence.870, February 1981Audio Pcrwer Meter/Noise Re-duction / Process Timer / Highvoltage from 723 / JuniorsGrowing Up/The Voiced/Un-voiced Detector / EmergencyBrake for the Power Supply/150 W DC to DC Converter forthe Car/Low Noise 2 MetrePre-Ampf21i Digit DVIAIViagne-phon.

E72, April 1481Transistor Match-rnakeri Unrrer-sal Power Supply/InteiekttHu.m id i ty Sensor/Logic Analyser II/C rystalcontrolled Stroboscope/Junior Cookbook.

E73, May 1981Camping Clock / FrequencyDoubter/The Fully FledgedJunior Computer/Talk to Com-puters/Choke Alarm/Bar Codes/Logic AnaryOroWaveforrn Gen-eratoriSophisticated Softwarefor the Junior Computer/Read-ing Bar Codes.

E77. September 1981DFM + DVM/Revolution Coun-ter/Digital BarometerldB Con-verterITV Game Extended!Disco Lights Controller/QUADESL 63/Analogue LED Display/Volt/Arnmaer for Power Sup-plies/Chattering Chips/TransistorIgnition Update/Soldering Alu-minium.E89, September 1982Gas Detector/Rapid LoadingGames/The Elektor Connection!Inductive Sensor / DarkroomComputer Part 1 / Applikator/Home Telephone Synem/Syn-thesised Sound Animation/TimeReceiver for the Rugby PASE/Three Phase Tester.

Lefeiltor

doinweicic-den ewe bumfelsonwee... yardstickears aweentdirenerrdw ri.evr

1.410111r

E90, October 1982DSB Demodulator/L.C.D. Ther-mometer/Ultra Sonic DistanceMeasurement/Electrolytics RunDry/Darkroom Computer Part

Wave BandSSB Receiver/16 Channels withonly Five ICsIPre-amp for theSSB Receiver / Active Aerial /Transistor arid IC Data.891, November 1982Drum Interface/Talking Dice/Model Train Lighting/GuitarTuner!Cerberus!Floppy Disc In-terface for the Junior/Cub-sitar Bell/Mini-Organ Extension/Kitchen Timer.E93, January 1983

Iliohnimeter/accessories forthe Crescendo power amplifier/Darkroom computer tips/Chipsfor digital aucko/3 A computersupply/Traffic-light control sys-tem / Tomorrow's music / Upperand lower case on the Elekter-minal.

c-.1 4 .- enseeeidp-eowesioee ;

E94, February 1983Prelude part 1NAM - video/audio modulator I Main beamdimmer/Prelude dass A head-phone amplifier/Fuse protector/Acoustic telephone modern/Double dice/Chips for digitalaudo part 2.

E96, April 1983Low power digital thermometer/MC/MM phono preanp/Mem-brane switches/Interlude/RCequalizer/7day timericontrot-ler/Ainior program tester/Pre-lude (part 31/Programmabledarkroom timer/Talking clockextension.

E97, May 1983Wattmeter/ASCII keyboard/Pre-lude p.s.(Multitester/Maestro(part 1)/What is power?/Parallel-serial keyboard converter/Morsecorwener/78L voltage regulators.. and 79LIMorse decoding withthe 280A.

E99/100, July/August 1983Summer Circuits Double Issuecontaining over 100 projects.E101, September 1983Video Graphics / Autotest /64k on the 16k Dynamic RAMCard / high-speed CMOS /VDUCard / Personal FM / PrecisionVoltage Divider / Alarm Exten-sion / Junior Synthesizer /Simple MOSFET Test.

E102, October 1983Basicode-2 Music Ouantisizer /Solid-state Darkroom Lighting /High -voltage Regulator / Anem-ometer / Programmable PowerSupply / Basicode-2 Interfacefor the Junior Computer / Elec-tronic Voltage Regulator / Bat-tery Eliminator / TransistorSelector / FSKleaner / EPROM-mer using the Junior Computer.

E103, November 1983-Doorbell - or telephone -operated flashlight/Power Con-troller for Model Railways/Droaupling in Digital Circuits!CPU Card/Decimal to BinaryConverter/Movement Detector/Electronic two-tone Metronome/Pseudo Stereo/Universal Ter.minal/U hresonic/Infrared Ba-risal -tick Battery/Crescendo re-visited.

8104. December 198364 -way 2 -dimensional Bus Board/ME/HE USB Marine Receiver/LED Ornaments/SymmetricalPower Supply/Video Amplifier/Locomotive Headlamp Reverter/Frost Warning Driice/DiscoPhaser/Banking Prograrn/N OV-RAM. Data Storage without Bat-teries/Bus Extension/ + Cumu-lative index 1983.

ekitor

8105, January 1984GyrophoneiHow accurate isyour watch? /Digital CassetteRecorder/Audio Signal Embel-lisher/Universal Active Filter/from Thermometer to Thermo-stat/Audio Sleuth at work /landDirection Indicator/Z80 EPROMprogrammer/Home-made lowcost Wiring ProbelAddress de-dna-EIDE, February 19846502 Tracer/Diesel Tathometer!Programmable Disco. Display

tester with a cfifference/Revers-ing Buzzer/Memory timing/Mating Logic Farnilies/C.apaci-mnce Meter/Bari code 2for Juniorplus VDU Card/Constant Volt-age Source/CS Chip Selekt/Video Sync Box.E107, March 1984Petrol Saver/Triac Control Board/UHF Video and Audio Modu-lator/ GET & GO/Elabyrinth/Varistor Protection Circuits/Real -Time Analyser (part 1)/Applicator/Tape Timer.E108, April 1984Optical Mernories1Controliing theFloppyc9sk Drive Motor/PulseGerxrator/Using the Pulse Gener-ator/Intelligent EPROM Eraser/Z80 SmulatorIMetronorrie Exten-sion/Real-time Analyser, part 2/Variable A.C. Power Supply/IceistiChip Selektfrape ContentsDetector.8109, May 1984Noise Squeich(Short.vave PocketRadio/Floppy Tester/SwitchingPower Supply/Analytical VideoDisplay:Aviary Illumination/Howmany Watts7itilini Crescendo/alook at EXOR and EXNOR Gates!EPROM Cwix. /Digital CassetteRecorder revisited/Real-time Ana-lyser. part 3/RS423 interface.

8110, June 1984Portable Distress Signal/2X Eirten-sioralDisco Drum/DaisywheelTypewriter Printer Interface/Maxi-mum and Minimum Memory!Leadecid Battery Charger/Wire-less Microphone/Merging BASICPrograms/Echo Sounder/VersatileAudio Peak Meter.

E111/112, July/Augon 1984Summer Circuits Double Issuecontaining over 100 projects

8113. September 19848114. October 1984

Back numbers of Elektor currently available are detailed above, with a brief description of their contents.Send for your copies now, using the pre -paid Order Card inside the back cover of this issue.Prices are as follows: any one issue (except July/August) £ 1.50

additional issues, each £ 1.30July/August (Summer Circuits) £ 3.00

Prices include postage and packing. Overseas orders requiring airmail postage add £ 1.50 per issue (£ 2.00 for July/Augustissue) (Prices subject to change without notice)

12-04

/.//c

/7

bigger and better.A' 4

Nicad Batteries & ChargersHigh quality nickel cadmium rechargeable

batteries. Equivalent in size with popular DryCell sizes e.g. HP7 ( AA ), UPI 1 (C ), and HP2 (D).Minimum life 600 ( 300 PP3 size )fullcharge discharge cycles. Batteries must becharged front a constant current source only.All batteries are supplied only with a residualcharge and should be charged before used.

DATA & PRICESType V(nom) Capacity Stock No - 1-9 10.49A.A 12V 500rnAH 01 -12004 080 0.74C 12V 12AH 01-12024 235 1.99D 12V 1 2AH 01-12044 200 2.00PP3 8.4V 1 lOrnAll 01-84(64 3.70 350

CH/450To recharge up to 4 AA size NiCadsSize:112 x 71 x 37 mm 01-00409 4.95

CH1I22To charge PP3 type NiCads.Size; 70 x 50 x 32mm 01-00159 430

CH8/RX

Will recharge AA. C. D and PP3 size cells with auto-matic vol tage selection. Will recharge followingcombinations: 4xD.4xAA,41-C., 2xPP3.2xD 2x -C.2x/3 - 2x.A.A. 2.1:D 1xPP3,2xC 2xk4. brc1 xPF9.2xAA 1xPP3. Marge rate: IlrnA for PP3.45m.A for AA size, 120mA for C and D size. for 16hrs. Power: 240V 50Hz. Ou tput Voltage: ZSV for AA,C and D size, 11.0V for PP3 size. Weight: 0.475kg.Size:199 x 109:55mm.

01-02204 9.45

HT320High quality. high specification meter at a

reasonable price. In addition to the usual ranges.facilities are provided for measuring transistorparameters such as lceo and Hfe.Meter movement fully protected against overloads.3 -colour mirrored scale in robust case. Suppliedcomplete with comprehensive instructions, testleads, transistor test leads and batteries (2 x HP -7.1 x PP3).

DC Volts: 0.1V. 05V, 2.5V, 1014.50V. 25011.1 kV(20kfliV). AC Volts: 101/.50V. 250V. IkV(18kil V).DC current: 25triA, 25rnA, 250m.A.Resistance: 2 k.20k,2.51.2051z_ AF Output: -10dB to-22dB for IOVAC(OdB 0.775V. 6000). Leakage(Iceo) 15µA. 15m.A.150mA. Hie: 0-1000(Liclb).Weight: 410gms.

56-83201 14.00

RF Generator LSG17

A stable wide -range generator for the hobbyist.service technician. schools. coil eges. etc.Frequency range:A 100kHz -300kHz. R 3(Xfidiz to1MHz (Harmonics 96-450MHz) C 5MHz,D 3.0MHz-11MHz, LIOMHz-35504z.

F32MHz-150Miz.Accuracy:kI3 i.Outputgreaterthan 100mV(no load) Ext. artal osc for 1 to 15)41-1zcryt al. Power required: AC I 00, 115 or 230V 3VA.

Size & Weight: 150(H) x 238(W)x 134,D)rnm.2.5Kgapprox_

56-90017 115.00

Linear ICsStock No. Price

1/351 Fli-FET °pomp 61-1)3510 0.49LF353 Dual version of LF35I 61-03530 0.81LMISON IIV AF power arnp 61-00380 1.45114381 Stereo pre -amp IC 61-00381 327NE541 14 pin DIL semi driver ICNESS&N Multi -purpose low

cost timer

61-00544

61-05550

ISO

021uA741GN OIL low cost op -amp

TDAI062 RF ocillator and mixersystem for 1-200MHz

IDA 1083 Portable radio AM FMaudio in one IC

61-07411

61.01062

61-01(553

0.42

1,95

1_95

FLA1383 1SW PA from I4V

MC I 496P Double balanced mixer

iltidulatorMA2002 8W into 2 ohms

power ampL1.,523 1W max 3-12V

power ampCA.30E44 EMT amp,detector.

mute, AFC. AGC system

61-01388

61-01496

61-02002

61-02283

61-03089

2.35

1.25

125

1.00

2.84CA3130E BLMOS op amp 61-31300 080CA3140E BLMOS version of 741

MC3359 Low current dual convex -

lion Ni3F)4 IF and det

61-31400

61-03859

0.46

295LM3900 Quad norton amp 61-39000 120L51390% 8 -pin DIL LED flasherI1/41344 I 2 Two balanced mixers IF amp

with AGC for AM SSB

1047555 Low power CMOS versionof 55 tinier

61-39090

61-04412

61-75550

Of'S

1.95

0.98HA11225 Low noise FM IF 61-11225HAI 2017 FC.dEi S N Olen° premp

0 001% TIM 61-12017MC14412 300 baud MODEM controller

(EuroUS specs) 61-14412

1.45

OSO

685

Selected LinesPB2720 EitidB Piezo Buzzer 43.27201 055105115A 107Filter 20-10152 2.1011151118.AA 10 645 Filter 20-11152 3.49FC177 LCD Freq Meter 39-17700 20.00051161 Min LCD Clock 40-80161 825BBC to Centronics Cable 03.10019 725Dragon to Centronics Connect Cable 03-10017 725Cl? Computer Cassette Tape 21-00012 0.558 x 03" IC socket 28-00800 0.1214x03' IC socket 28-14000 0.1316x03'IC socket 28-16000 0.1361' KL1T-A Relay 46-80000 0.489V KL1T-ARelay. 46-80001 0.48121' KL1T-A Relay 46-80002 0.48CM 20P COAX Relay 46-90120 1196CX520D COAX Relay 46-90520 26.980340D COAX Relay (BNC) 46-90540 2698

BooksBeginners Guide to Amateur Radio 02-11262 450Beginners Guide to Electronics 02-04134 4.50Active Filter Cookbook 02-21168 12.70CMOS Cookbook 02-21398 11.85TTL Cookbook 02-10358 11_00Design of ActiveFilters 02-21539 10.15Design of Op -amp Circuits withexperiments 02-21537 9.30

Effectively Using the Oscilloscope 02-21794 930The a Spectrurn 02.00100 595Practical Design of Digital Circuits 02-11831 10.45Electronic Projects for HomeSecurity 02-05351 380

Electronic Telephone Projects 02-21618 78055 Tuner Applications Sourcebook 02.21538 6.40Television Engineers Pocket Book

7th Ed 02-21313 8.50EleLtionics Pocket Book 02-21309 75099 Practical Electronic Projects 02-21635 590More Electronic Projects in theHome 02.21307 3.80

The Ft.dio AmateursQuestion andAnswer Reference Manual 02.02157 5.95

Basic Programming on the BBCMicrocomputer 02-06640 595

Using Microprocessors andMicrocomputers:The 6800Farnily 02-98728 11.05

2-80 Microcomputer DesignProjects 02-21682 1270

Z8000 Microprocessor:A Design Itmdbook 02-37345 16.10

6800): Principles andProgramming 02-21853 12.70

8085A Cookbook 02.21697 1355Handbook of Ekctrortic TablesPrimulas 02.21532 11.00

Popular Circuits: ReadyReference 02-04585 1395

Semiconductor Data BookI I th Edition 02-04797 9.00

elektor december 1984

Airbornecommunications...Racal has taken a world lead inair/ground data communications viasatellite with the announcement thatthe first phase of testing hardwareand proving the systems viability forthe unexploited civil market is welladvanced.In conjunction with British TelecomInternational and INMARSAT (Inter-national Maritime Satellite Organisa-tion), Racal is using its Jetstreamaircraft for trials of the satellite datacommunications equipment. Preciseposition and other flight data isbeing relayed to the ground viasatellite link, enabling ATC (air trafficcontrolland other operating staff tokeep a higly accurate fix on the air-craft's location at all times.The system will pave the way formore effective air traffic control on aglobal scale, the passing to and froof meteorological and operating dataas well as other information both foroperators and for passengers..Currently, long-range communicationwith aircraft is by h.f. radio with allits attendant propagation andreliability problems. The satellitesystem will not only overcome thesedifficulties but may also reduce costssubstantially, and give operators thecertain knowledge they can contactaircraft at any time and in any placeoutside the polar regions.

...and surveillanceThe British Aerospace DynamicsGroup and the Electro-Optical andData Systems Group of Hughes Air-craft of California have reached anagreement under which Hughes willbe responsible for the promotion andsales to the US Armed Forces ofBritish Aerospace's Linescan 2000and 4000 airborne surveillancesystems. A further agreementlicensing Hughes to manufacturethese systems in the US is expectedshortly.The Linescan systems produce veryhigh quality infrared imagery(developed for the surveillancesystem of the Tornado aircraft),which may be viewed immediately inthe carrying aircraft, or, via adatalink, at a ground station, or berecorded for later analysis.The type 2000 is designed for man-ned and unmanned aircraft and heli-copters, while the 4000 is intendedfor high performance aircraft conduc-ting high-speed, low-level recon-naissance.

Computer -literategenerationBy the time the current generation ofschool children and students com-plete their education, Britain will bethe only country in the world with

E

EDEan entire generation literate andversed in computers and computertechnology.Every single one of the country's10.6 million pupils and every one ofthe half a million students haveaccess to a computer at some stageduring their education - and mostlyon a daily basis.Thanks to the government's far-sighted programme "Micros inPrimary Schools", launched a coupleof years ago, 18 000 primary schoolshave been able to buy microcom-puters for their classrooms. Higherup the age groups, 5800 secondaryschools have computers as do 868polytechnics and 45 universities.As if these figures are not impressiveenough, Britain has the highestnumber of computers in the home inthe world. An astonishing 2.7 millionhomes - 12 per cent of the total -

own their own computer. Allowingan average of three people per home,this means more than one third ofthe entire population uses andunderstands microcomputers. (LPS)

Marconi in Spain...A consortium comprising MarconiRadar Systems, Page Iberia, andEquipos Electronicos S.A. has beenawarded a £20 million contract forthe supply of primary radars, displaysystems, installation, and systemdesign under a f60 million Spanishair traffic control modernization plan.Marconi Radar will supply sets ofdrawings, and all manufacturingwork will be carried out underlicence in Spain. Testing will be toMarconi specification.As well as eight type S511c

Approach Control Radars (a higherpower version of the successful 5511which, among others is in service allover the UK, Bombay Airport, andQueen Alya's Airport at Amman), thecontract calls for an IndependentWeather Channel, which enables airtraffic controllers to superimpose anelectronic map of rain and stormareas on the radar screens withoutobscuring aircraft 'blips, and aprimary radar plot extractor whichenables radar signals to be sent overnormal telephone circuits.

...and in AmericaMarconi Communication SystemsLtd. have signed an agreement withTelecommunications Technology Inc.(TTI) of California for a version ofMarconi's successful AutomaticCross -connect Equipment (ACE) usedin the Kilostream data service ofBritish Telecom.Under the agreement, TTI arelicensed to modify existing ACE tomeet U.S. transmission standards.Initial development will be carriedout in Chelmsford and then transfer-red to California.

Family favouritesAs part of the celebrations by Philipsof their outstanding television setproduction record as reported in theNovember issue of Elektor, thecompany commissioned a researchinto the likes and dislikes of BritishTV viewers. The research reveals thatTerry Wogan is everybody's favouriteall-time male TV personality - evenputting Clint Eastwood into secondplace. It is understood that JimmyYoung is demanding a recount!Felicity Kendall is the all-timefavourite female personality - andwe wouldn't argue with that!Top TV programmes are, ratherpredictably, Dallas and CoronationStreet. Notable high spots in tele-vision viewing history include NeilArmstrong's TV spectacular to endall TV spectacular's, but even thiswas shown a clean pair of heels by- who else but Charles and Dianaat their 1981 Royal Wedding! Thiswas voted "the most memorabletelevision programme" ever watchedin every region of the British Islesand among all social groups.The clear winner of "the first pro-gramme I ever saw" was the Coron-ation of 1953. However, younger agegroups obviously have different'views'. Top of the polls here includesuch eternal favourites as AndyPandy, Bill and Ben, and theWoodentops!

Dolby success down underA recently announced decision bythe Australian minister for communi-cations makes the Australian Broad-casting Corporation's TV and radio

12-18

e!ektor december 1984

services via the AUSSAT satellite thefirst national user of the new Dolbydigital sound system, along withPlessey Scientific Atlanta's B -MAC(Multiplexed Analogue Component)transmission for the picture. It sets astandard for future satellite transmis-sions in the country.Australia is the first country toannounce a firm decision in favourof the system. Practically all majorAmerican companies involved insatellite broadcasting are alsoreported to be seriously interested.Various European broadcasters,including the BBC and the IBA, aretesting the Dolby digital system forits potential application in conven-tional terrestrial services.Dolby Laboratories claim low cost,good quality sound, even under badreception conditions, as well as lowand flexible bit -rates as the mainadvantages of its system over con-ventional digital PCM systems.

The rise and fall of PCsThe phenomenal growth in the per-sonal computer market since 1980 isexpected to rise to a peak of 1.9million units this year and then likelyto fall of to 1.2 million by 1988,according to a new Market Assess-ment Product Group report, the firstfull market study carried out in thiscountry. The report does not see the

off as an indication of thedemise of the home computer, butmerely of the market becomingmature.In the longer run, the report states,it is conceivable that home com-puters will become major items ofhousehold equipment. For instance,as a home work station, with a link

to the place of employment, com-puters have a strong future.At present, there are some thirty-eight brands of computer on themarket, many of which are relativelysmall and lack the public awarenessof established names. How longmany of them will survive is notclear, but a reduction in the numberof models available seems inevitable.The major established brands shouldescape virtually unscathed, butsmaller ones look vulnerable, par-ticularly if MSX quickly gainspopularity.Sinclair remains undisputed marketleader with a forty-three per centshare, followed by Commodore(twenty-two per cent), and Acorn(and BBC) with ten per cent.

The best of BritishThe Automobile Association hasawarded a £1.3 million contract toSoftware Sciences, a subsidiary ofTHORN EMI, for the supply of thecountry's most advanced Commandand Control communication system.The AA will use the system for itsLondon breakdown and informationservice - to match men andmachines, quickly and effectively,with the 1.1 million working callsreceived at its London OperationCentre each year.The new system, which is plannedto go into operation in 1986, willinclude eighty terminals, 500 datatransmission print-out units in AApatrol vehicles, an up -dated vehicledeployment method, an automaticstreet gazetteer, a sophisticated com-puter information retrieval facility,electronic telephone call distribution,and high -quality digital map displays.

British astronauts openLondon TeleportThe London Teleport, British TelecomInternational's satellite earth stationin the Docklands, was officiallyopened in October by two of Bri-tain's astronauts, Mr CristopherHolmes and Lt Col RichardFarrimond.The Teleport, the world's first inter-national earth station to be installedin a city, currently transmits six tele-vision channels to cable TV networksaround the UK and Europe. The pro-grammes are beamed to satellites ingeostationary orbit some 22 300miles above the equator and receivedback by cable networks in the UKand Europe a quarter of a secondlater.As well as offering considerablepotential for the development offurther cable TV distribution, theTeleport will also be able to providespecialized communication servicesfor London's business community,including videoconferencing anddigital communications facilities.

Shine on, optical fibre!-

A nei.v study by Frost Ed- Sullivan,"Opto-Electronic Components inEurope" (#E696), shows that whilecathode ray tubes (CRTs) will con-tinue to dominate the fifteen compo-nent categories analysed due to theiruse in microcomputers systems, theywill grow more slowly than theaverage annual gains of fifteen percent that the market is anticipated toregister through 1989. Optical fibresand fibre -optic connectors andcouplers, by contrast, will each showtwentyfive per cent increases: theirtotal market is expected to rise froma 1983 base of £420 million toaround £1000 million by 1989.Opto-electronic components will beused most in telecommunicationsand communications, which aloneaccounted for twentynine per cent ofthe market in 1983 and will representnearly thirty per cent by 1989. Ofparticular importance be sub-marine cables using fibre optics.By region, the UK is the premiermarket at twenty-seven per cent,followed by West Germany attwenty-five per cent, and France attwenty-three per cent.

The boom goes onAccording to "Data CommunicationsMarket" (#12881, a new study byFrost Et Sullivan, personal computerswill continue to enter the businessenvironment in record breakingnumbers for use both as stand-alonesystems and as major bases for datacommunications. One indication ofthe latter is the constantly increasingdemand for modems: the modernmarket in the USA is expected tohave a value of $4000 million in 1988,up from 1984's figure of $1180million.Although, the report says, due tocomplexities and technologicalintricacies, the application of digitaltechnology to data communicationshas been slow, in future decades allmodes of point-to-point communi-cations will at some time be underthe control of a digital processor.The next five years will be pivotal forthe industry: the report expects thatby 1990 the separate industries ofdata processing and communicationswill have melted into one, and thatby 2000 the officie automationgroups will have been assimilated.Another market that will boom,according to the study, is themultiplexer market: up to $2000million by 1988 from 1984's figure of$500 million.

Seafox for Chinese navyFollowing months of negotiationsand technical evaluations, ThePeople's Republic of China andMarconi Communication Systemshave signed a contract for the supply

12-19

elektor december 1984

of h.f. shipborne radio systems.The contract includes elements fromthe Integrated CommunicationsSystems similar to those fitted in allthe latest Royal Navy warships andin ships of several overseas navies.The control system uses equipmentfrom the Marconi Seafox Naval Com-munication System that is also inservice with the Royal Navy.

Oxford/Cambridge wrangleAcorn Computers, the Cambridge -based BBC micro manufacturers,have failed in a bid to block advertis-ing claims by Research Machines,based in Oxford, of sales to overseventy-five per cent of schools andcolleges in the UK.Acorn complained to the AdvertisingStandards Authority (ASA) whenResearch Machines first ran the con-troversial advertisement about salesof their 480Z micro network systemsto the educational sector of themarket. The ad compaign was thensuspended pending judgement bythe ASA.In early October, the ASA gave per-mission for the advertising campaignto go ahead after they had upheldthe figure which shows ResearchMachines to have a significant shareof the educational computer market.

Hands across the ocean...GTE Microcircuits of Tempe (Arizona)and Plessey Semiconductors Limitedof Swindon have entered into a co-operative agreement, the first phaseof which will result in a fully com-patible family of high speed CMOSgate arrays.The family will consist of CMOSgate arrays ranging in size from 640to 10 044 gates, and offers systemdesigners a choice of operating fre-quencies up to 40 MHz. Softwaredevelopment tools for complete pro-duct simulations, testability analysis,and automated routing are alsoavailable.The agreement provides for joint pro-cess development and processexchange, as well as development offuture products. The programme hasbeen enhanced by the transfer of thePlessey Semiconductor 2 microndouble -layer CMOS process, whichwill be used in the fabrication of thegate array family.

...and across the borderThe West German electrical firm ofSiemens and Dutch electronics giantPhilips have announced plans for thejoint development and production ofa new generation of memory ICs.Total development costs are expectedto be around £250 million, half ofwhich is said to be provided by thetwo countries' governments.

No explosion with thiscomputerThe world's first truly hand-heldmicrocomputer specially designedand fully certified for use in hazard-ous conditions in mines, paint stores,.petro-chemical installations, and onoil -rigs, has been developed by theScottish mining engineers AndersonStrathclyde of Glasgow. Type -codedthe CS21, the unit is intended to actas an electronic notepad, portabledata capture unit, work study ter-minal, calculator, calendar, stop-watch, and electronic tape recorder.As versatile as a desk -top computer,the CS21 measures about200 x 100 mm, weighs less than1 kg, and is certified to full BritishGroup 1 safety standards whcih arerecognized throughout the BritishCommonwealth. (LPS)

Spinning orderBritish Aerospace Precision Productsat Stevenage have been awarded anorder worth nearly £3 million for theirminiature rate gyro known as theDual Axis Rate Transducer (DART)by Texas Instruments. The DARTswill be used in the next productionbuild of the Paveway III laserguidance kits for the United StatesAir Force. Further substantial ordersare currently being negotiated. (LPS)

More power into smallersilicon chipsA £63 million programme of researchinto a key area of silicon chip

vEPEOPLE

technology has been announced bythe Minister for InformationTechnology, Kenneth Baker, whorevealed details of thirty-five co- .operative projects which will aim atestablishing the technology requiredfor the next generation of siliconintegrated circuits. The projects arebeing funded by the Alvey Pro-gramme, a joint venture betweenBritish industry and government tosupport advanced technologyresearch.The programme is concerned withthe vital field of Very Large ScaleIntegration (VLSI) technology, whichis the leading edge of microelec-tronics research. As microelectronicsis the key to our industrial future, theprogramme will help keep the UK atthe forefront in important areas.The thirty-five projects involve fifteendifferent firms, ranging from themajor semiconductor companies tosmall equipment manufacturers withno more than a dozen employees. Atotal of twenty-four universities,polytechnics, and other researchinstitutions are also involved in theco-operative programme.

Spirit of the EECAfter the launching in 1983 of theESPRIT Information Technology Pro-gramme, close to one hundredtransnational R D projects haveno..; been started. Subject to thefinal signature of contracts, the Com-mission of the European Com-munities will commit up to ECU 200million this year; this sum will bematched by the industrial par-ticipants in the programme.The ninety projects for the mainphase of ESPRIT were selected byindependent experts out of a total of441 proposals put forward earlier thisyear. These represented a total fund-ing requirement of nearly ECU 1900million, as compared with the totalof ECU 1500 million agreed for thefirst five years (1984...1988) of theESPRIT main phase.The ESPRIT programme bringstogether industry, research labora-tories, and universities across Com-munity frontiers. In some cases the1984 contracts include up to tenpartners, although the averagenumber is four. There are no excep-tions to the basic ESPRIT rules offifty per cent co -funding by industryand the Community, with at leasttwo separate industrial partners fromdifferent EEC countries in eachproject.The programme focusses research onthe key technologies of microelec-tronics, software, advanced infor-mation processing, office systems,and computer integrated manufactur-ing. These areas are all covered inthe 1984 contracts an projects weresubmitted from all the EEC countries.

12-20

elektor december 1984

Talking typewriter for theblind...An electronic aid for the blind andpartially sighted which convertsBraille symbols into standard printedtext and provides a simultaneoussynthesized speech output to guidethe writer has been developed at theUniversity of Essex. The system,called the Essex Speech Writer, isclaimed to be the first of its kind.The speech writer consists of aspecial keyboard, a microcomputerwith speech synthesizer, and a vir-tually silent ink -jet printer. Thekeyboard has nine keys spaced in alayout similar to that of a machinealready familiar to blind writers, thePerkins Brailler. The output of thePerkins machine is an embossed tapecarrying Braille text unreadable tomost sighted people. The newmachine produces no tape, but con-verts the symbols entered at thekeyboard into printed text with asimultaneous synthesized speechoutput.

...sight for microcomputersImage analysis is now available foruse with any microprocessor that hashigh resolution graphics and aneight -bit parallel port at no morethan the cost of the microcomputeritself, thanks to a vision systemdeveloped by Digithurst of Royston,Herts.The basic system, called MicrosightI, uses a standard closed circuit tele-vision camera to capture images,passing them through a special inter-face, and transferring the data aseight -bit digitized video signals. Themicrocomputer's RAM stores thecaptured image in monochrome andthe software can be used for simplemapping and object recognition.With the addition of Microsight II, itis possible to input pictures of tele-vision quality and store them ondisk. The further addition ofMicroscale software allows enhance-ment of picture detail measurementof defined areas of the picture, thusproviding CAD type facilities.

Thwarting the piratesThe illegal copying of computer pro-grams from floppy disks costs soft-ware companies a fortune in lostsales revenue and although encodingtechniques exists they are no deter-rent to experienced software pirates.But now Expert Software Inter-national Ltd of Edinburgh has comewith a method of ensuring that com-mercially produced software will onlyfunction if it is run from an author-ized disk.The company describe theirCopylock process as "fingerprinting",whereby prior to the recording ofprograms disks.are encoded with the

software company's encryptiondetection sode which is imperviousto all known copying techniques.The protection process, which is partof the disk formatting, does notaffect the software and is invisible tothe program user.According to the manufacturers,unlike other anti -copying systems,their process allows copies to bemade on suitably formatted diskswhose numbers can be controlled fordistributor purposes.

No wedding bellsIt will probably never be known towhat extent the letter from theNational Computer Users Forum(NCUF) to the Secretary of State forTrade and Industry augmented theopposition of the Office of Telecom-munications Policy (Oftel) to value-added -network services (vans) in thegovernment's decision to veto theproposed joint venture between thefirm that sells most of the world'scomputers, IBM, and the firm thatoperates most of Britain's telephonelines, British Telecom.The NCUF was concerned that theproposal would divert resources fromthe implementation in the UK ofinternational standards for OpenSystems Interconnection to whichthe European Community is commit-ted. Open Systems Interconnection,or OSI, makes possible communi-cation between computers of dif-ferent makes and in differentlocations.The NCUF was anxious to avoid thesetting up of what might create amonopolistic service by combiningvans and bearer services. This wasparticularly worrying since the jointventure proposal included plans toimplement electronic mail (an OSIstandard) at a very early stage viaIBM's proprietary network standard,Systems Network Architecture(SNA). The NCUF did not believe itto be in the long-term nationalinterest to create a situation wherethe UK is not in line with the rest ofthe European Community.British Telecom and IBM UK Ltdhave expressed their disappointmentwith the DTI's decision and said thatthey believed that their proposaloffered the best possible stimulus tothe emerging marketplace for vans.They feel that the refusal to grant alicence represents the loss of animportant national opportunity sincethe development of an OSI marketand of a bridge between OSI andSNA should be based on an assuredcommercial foundation and that thejoint venture would have providedthat foundation better than any otherroute.It is certain, however, that the DTI'sdecision will please our Europeanpartners, particularly France andWest Germany, who have opted to

support OSI rather than SNA. OSImay still be in its infancy, but itappears to be a certain way to makethe European information industryflourish in the face of American andJapanese competition.

PeopleDr Geoffrey Phillips, Head of RadioFrequency Group at BBC EngineeringResearch Department, has beenpresented with the first -ever IBCAward in recognition of his inter-nationally acclaimed work over theyears in forstering the efficient use ofthe radio spectrum.

Dr Peter Troughton has beenappointed Managing Director ofBritish Telecom Enterprises. Thisfollows the resignation of Mr ColinCrook from the Board of BritishTelecom to take up an internationalappointment with an American -basedmulti -national computer company.

On 1st October, the Directors of theMarconi Company Ltd accepted theresignation of the company's chair-man, Sir Robert Telford CBE, andimmediately resolved to appoint SirRobert as President of the Companyfor life. The position of Life Presidentof The Marconi Company has beenheld by only one other person:Guglielmo Marconi, the founder ofthe company.CTM Computertechnik Muller GmbH,the West German business systemsmanufacturers, have made twoappointments for its start-up UKoperation: Mr Ian Co!dwell asManaging Director and Mr AlanColvin as Marketing Director.

12-21

electronic candleelektor december 1984

Figure 1. The mechanicalpart of this electroniccandle needs to be madecarefully to achieve arealistic result. It is prob-ably best to use a realcandle if possible.

Elektorlights acandle towish allour readersa MerryChristmasand aHappyNew Year

iIThe circuit

The electronics

VelitterieltrePerOtAkAOSEftlfttratkiktiktiltalsitkulAWIlftfteriellaquench this candle, shown in figure 2, isclearly very simple. It consists of littlemore than two ICs and two transistors. Italso works in a very straightforward man-ner. There are two pick-ups (an LDR andan NTC), each of which is followed by anamplifier (Al and A2) and a flip-flop con-taining op -amps A3 and A4. The flip-flopswitches the lamp in the candle on andoff via Tl and T2.This is how the candle is lit. A burningmatch is brought close to the LDR (R2)whose resistance then drops and reducesthe potential at the non -inverting input ofAl. A large negative voltage is output fromthis op -amp, making the output of A3'high. The lamp is then lit via the two tran-sistors. Positive voltages at the output ofAl have no effect because they areblocked by diode Dl. The sensitivity ofthis part of the circuit (the light intensity atwhich it reacts, in other words) is presetby means of Pl.Blowing out the candle is a completelydifferent procedure. The NTC (R7) is pre-heated by means of R6. (For this reasonthe circuit must always be let warm up fora minute or so otherwise it cannot be

84108-1 blown out.) When the NTC is cooled by

electronic candleWe are now approaching a season that is steeped in tradition. It is atime of gifts, carol singing, 'peace on Earth' and so many otherthings that give this time of year a special 'mood'. As ever, we try topublish appropriate circuits and certainly this electronic candle fitsthe bill. Like most candles, this one can be lit with a match andblown out. Apart from that, however, this is a very unusual candle.Read on and find out why.

The idea of an electronic candle is notcompletely new but its success is assuredbecause the effect achieved is fascinating.The idea of this circuit, basically, was to'electrify' an ordinary candle, replacingthe wick with a small bulb but retainingthe rest. Above all, the character of thecandle should remain the same so it mustbe lit with a match and can be blown out.The biggest part of this trick (for that iswhat it is) involves fixing (and hiding) twocomponents just beside the light bulb.The parts in question can be seen in thesketch of figure I: an LDR (light depen-dent resistor) for lighting the bulb and anNTC thermistor (negative temperaturecoefficient) to register the breeze thatquenches the candle. Most of the timespent on the rest of the circuit will involvemaking the candle look as realistic aspossible; the electronics is hardly likely tocause any headaches.

needed to light and

blowing on it or touching it with a wetfinger its resistance increases and causesthe potential at the non -inverting input ofA2 to rise. This op -amp then outputs alarge positive potential that is passed tothe flip-flop via D2 (which blocks negativevoltages). The output of A3 then jumps'low' causing Tl and T2 to switch the bulboff.

Building the circuitMost of this circuit is located on theprinted circuit board shown in figure 3.The exceptions are the LDR/NTC/lampcombination and the transformer. Thereare two points to note about the circuit.First of all, either a 6 V or a 12 V lamp canbe used; in the latter case R22 must bereplaced by a wire bridge. The secondpoint is that the choice of what type ofvoltage regulator is used for IC3 dependson the transformer voltage. Use a 78L08with an 8 V transformer or a 78L10 with a 9or 10 V type.

12-22

2 electronic candleelektor december 1984

*R2

LOS

57RTC

-1

100 .-ISO .1-1

La1

5

A1A2 = IC1 = TL 072; TL 082A3,A4 = IC2 = TL 072; TL 082

In a project like this the most importantthing is the appearance of the finisheditem. The sketch of figure 1 gives an ideaof how it could be done. The mostrealistic result is achieved by using a real

candle and hollowing it to make room forthe lamp, LDR and NTC. Even the printedcircuit board might fit into a very thickcandle but it is not such a hardship if thishas to be mounted in a separate case. 14

Parts list

Resistors:

R1, R19, R20 = 470R2 = LDRR3, R8, R11, R12, R14,R15 = 100 k

R4 = 4k7R5 = 10 kR6 = 100R7 = NTC, 100...150R9, R17, R23 = 47 kR13, R16 = 150 kR18, R21 = 1 kR22 = 47 4P1 = 100 k preset

Capacitors:C1 = 330 nC2...C6 = 10 p/16 VC7 = 470 p/25 VC8 = 100 n

Semiconductors:D1, D2 = 1N4148D3. . . D6 = 1N4001T1 = BC547T2 = BD139IC1, IC2 = TL072, TL082IC3 = 78L08, 78L10

Miscellaneous:

F1 = fuse, 100 mA slowblowLa = lamp bulb, 6 V/50 mAor 12 V/50 mATrI = mains transformer,8...9 V/150 mA (e.g. belltransformer)

= see text

Figure 2. The electronicsconsists of a pair of ICsand transistors and a fewdiscrete components.

Figure 3. The componentlayout on this printed cir-cuit board includes thepower supply section,with the exception of thetransformer.

12-23

the XR2206 in thefunction generatore!ektor december 1984

the XR2206 ir thefunction generatorIf a special IC is used in a circuit it usually meansthat the number of components needed is greatlyreduced. There is, after all, an extremely largenumber of semiconductors in one 'black box',sometimes even in exactly the right configuration fora particular application. This is the case with theXR2206 used in the function generator describedelsewhere in this issue. What this does not mean,however, is that the design can be made in no timeat all. There is a lot more to it than simply using anapplication found in the manufacturer's data book.

a few remarksabout the ICand the design

Figure 1. This photoshows an XR2206sinewave complete withthe typical spikes.

Figure 2. Again asinewava provided by a2206 but this one isgenerated by the Elektorfunction generator. Thetops of the sine couldactually be made a bitrounder. This would lookbetter but would increasethe distortion.

Function generators based on the almostlegendary XR2206 usually have a fewfaults that are well known to users of thisIC. There are dirty spikes on the peaks ofthe sine and triangle waves, these twowaveforms become more and more similarto each other above 100 kHz and theamplitude decreases gradually then also,the frequency scale is not correct forasymmetrical waveforms (sawtooth andpulse waveforms), and the so-calledsawtooth is more like an asymmetricaltriangle. Apart from these points the ICworks well...One of the aims of the new function gen-erator is to do away with these disadvan-tages. We must, however, first of all knowthe reason for the `errors' before we cansee how to solve them.

A better waveformThe difference between a normalXR2206-based function generator and thenew Elektor design is shown by the twophotographs of figures 1 and 2. These donot require any further comment. Thediagrams in figures 3 and 4 show wherethis difference in the waveforms comesfrom. -The standard layout is seen in figure3, whereas figure 4 shows the basics ofthe new design. The heart of both is, ofcourse, the same XR2206 whose internalsare illustrated in figure 5. Where do thosespikes on the sine and triangularwaveforms come from? All the tests car-ried out suggest that the principal causewill be found in the circuitry connected topins 13 and 14 (waveform adjust). Withinthe IC these two pins are connected to adifferential amplifier that makes asinewave from the triangular signal. Evena very slight capacitive load on pins 13and 14 will cause spikes to appear in thesignal, and this could be caused by evena short length of cable or by the tracks onthe printed circuit board. The only sol-ution for this is to keep all connections topins 13 and 14 as short as possible, withextremely short copper tracks betweenthe IC pins, the switch and the preset.This is the reason why the circuit of figure4 uses a BS170 (V FET) for switching closeto pin 14. Another cause of the spikes isthe fact that the 2206 consists of a squarewave and triangle generator followed by atriangle to sinewave converter. The squarewave's sharp edges corrupt the otherwaveforms as well. If nothing is connectedto the sinewave output (pin 11, which islinked to the collector of a switching tran-sistor in the IC), or if it is short-circuited,the sinewave is completely 'clean'. As soonas a resistor is connected from pin 11 tothe positive voltage supply line the spikesre -appear. A combination of square waveand (undistorted) sinewave in the samegenerator is only possible if the outputvoltage of the square wave at pin 11 iskept very small and this output is notloaded too heavily. In figure 4 pin 11 onlyhas to drive transistor T2. The basecurrent for the BSX20 is provided viaresistor R15. If the internal transistor con -

12 -24

nected to pin 11 conducts it simplyremoves the base current of T2. The base -emitter junction of T2 prevents the outputamplitude of pin 11 from rising above0.6 V. The square wave at the collector ofT2 still has a peak to peak value of 16 V,which is not very favourable for pin 11.The solution here is to short the output ofT2 if a triangular or sinewave output ischosen. In this way the square wave isvery effectively suppressed when it is notneeded.

Optimal amplitude adjustmentThe amplitude setting, by means of theAM input (pin 1) also appears to havequite an effect on the waveform. Cross -talk(for want of a better word) between thesquare wave and triangle/sine wave output(pin 2) will be reduced if a positivevoltage is applied to the AM input. This iswhy pin 1 in figure 4 is at +4 V. At -4 Vthe output voltage would have been justas large but there would have been morelikelihood of distortion.The amplitude of the output voltage at pin2 is effected by the resistance on pin 3 ofthe IC. To retain the same output ampli-tude when switching between sine andtriangle the resistance at pin 3 must beabout 2.7 times as high for a sine as forthe triangular wave. Many 2206 -based cir-cuits simply switch the resistance at thispin but our experience shows that this isnot to be recommended. Wires and tracksto the switch then make the circuit very

3

O

1. Symmetry2_ Ampritule3. Other (1.c..14. Wroeform adiust5. Frequency range

Frequency selection

the XR2206 in thefunction generatorelektor december 1984

0

OCk

T

57

7

S

2206

10..26V

I0

T

sensitive to distortion and changing theresistance also changes the d.c. level atpin 2. This problem could be solved byduplicating P5 and P6 and then switchingbetween these two branches. That is notwhat we have done, however. Theamplitude and d.c. level are fixed for bothwaveforms with P5 and P6 and theamplitude correction needed is carriedout at the output by means of voltagedivider R23/R24. The impedance of thisvoltage divider could only be kept low byincluding an emitter follower (T3) before

4

ve01..4al _toy

Cl

15V

53 IS

BV

1000

C3 C4 ,

s,

I

C

ST7133

5051153

BS 170

ICI /\AXR-2206

se.n.Tau rs.oe.:ST j ovrI al a 3

P7

2

8V

8V

=10

MIM

SX 20

Sle

CV- SYNC OUTPUT

0.6 L

53

8V

25

64125-3

0

1 0

JUL

Figure 3. This is the nor-mal layout used with the2206. Very few externalcomponents are used butthe results achieved arenot very good.

Figure 4. The Elektorfunction generator usesquite a few external com-ponents. Here it is seenwithout the output ampli-fier and power supply.

I... 111610... 11514$

e. 103 ... 1100164. 11116I 1]_.11]516

EST,F.: :GE.T....,EN:V

841284

12-25

Figure 5. This blockdiagram shows theInsides of the XR2206.The actual oscillator inthe IC (VCO) suppliestriangle and squarewaveforms. The frequencycan be set by means ofpins 7 and 8 (these areused to define the charg-ing and discharging cur-rents for the capacitorconnected between pins 5and 6). A sine shaperforms a sinewave fromthe triangle. Theamplitude (pins 1 and 3)can be changed using themultiplier. Adjustmentpoints 16/15 and 14/13 areconnected to the sineshaper.

Figure 6. If the frequencyis set by means of apotentiometer acting as avariable resistor the curveof frequency with respectto wiper position is farfrom linear. This gives ascale division that is notvery user friendly.

5

AM 0

muLT

2206

Symmetry asliust.

Wrestorm adsrn

SYNC.

04u

FSK

64125-5

6 00(WV 90

I BO70

Celt= II

60

50

0

30

20

o100 90 80 70 60 50 40 30 20 10

P1 (kill 64125-6

it. A high -impedance voltage divider (suchas 5k6/3k3) would, of course, do awaywith the need for the emitter follower butit would introduce more distortion andwould make the circuit more sensitive tonoise.

Frequency setting: linear andstableThe basic circuit of figure 3 uses avariable resistor (P1) to select the desiredfrequency. In this way the frequency isbarely effected by changes in the supplyvoltage but the scale division is not veryusable. The relationship between theresistance value (position of the wiper)and the frequency is shown in figure 6. Alinear frequency scale is obtained if thevoltage, rather than the resistance, at pin 7is varied. This idea is implemented infigure 4. In this case P2 forms a voltagedivider by means of which the (linear)wiper voltage is fed to RIO. To prevent thefrequency from being effected by vari-ations in the supply voltage the poten-tiometer is connected not to the supplybut to the output of a low -drift op -amp(IC2). This LF356 buffers the voltage pres-ent on pin 10 of the 2206; this pin actuallyprovides an internal reference voltagefrom the IC. There are two advantages tousing the reference voltage for P2: the fre-quency remains stable and the voltageacross P2 cannot become higher than thatat pin 7 (which is also connected to thereference voltage). The op -amp also'decouples' presets P1 and P3. With this

arrangement the maximum frequency canbe preset using P3 without effecting theminimum frequency already set with Pl.The voltage from pin 10 is also used as areference for external frequency settingsvia the VCO input. In this way theoptimum frequency stability is achieved.

No compromiseThe next point on the list is the 2206'sability to generate asymmetric waveforms.To do this the time constants for thesawtooth and pulse waveform must beswitched. This is achieved by tying theFSK input (pin 9) to the square wave out-put (pin 11) so that the capacitor betweenpins 5 and 6 is charged by the currentfrom pin 7 and discharged by the currentfrom pin 8. This is by no means a perfectsolution for a number of reasons. The dif-ference between charge and dischargetimes cannot be made great enough sothe sawtooth looks more like art asym-metrical triangle. The frequency scale ofthe potentiometer on pin 7 is no longercorrect as this now determines only abouthalf of the period duration; the restdepends on the 'resistance or current atpin 8. The external frequency control (viathe VCO input) must have an extra switch.Finally, the square wave fed through theprinted circuit board and switches frompin 11 to pin 12 corrupts the otherwaveforms. Our answer to these points isstraightforward: it is better to have noasymmetrical signals than bad ones.Regarding the stability of waveforms andamplitude above 100 kHz there is also onlyone acceptable solution: the frequencyrange should not extend beyond 100 kHz.The power supply used is completelysymmetrical. This enables it to workwithout decoupling capacitors and thesquare waveform is very good even at lowfrequency.All these 'improvements' on the 2206 areonly possible if a double -sided printedcircuit board is used. This is the only waythat the critical tracks can be kept asshort as possible and/or far enough fromeach other. This also enables the wiringbetween the board and switches, sockets,and potentiometers to be kept shorter andsimpler. This sort of printed circuit boardrequires a lot of care in the design stagein order to find the best layout. In this wayit is more than simply a way of intercon-necting the components: it is an essentialpart of the circuit.

ConclusionEven when a circuit is based on a specialIC that contains almost exactly the layoutrequired a lot of work is needed tofinalise the design. No part of the projectmay be overlooked. We have designedthe function generator carefully in orderto allow the XR2206 to do its job as well aspossible. What is also important is that wehave not pushed the IC to its limits. Doingthis could only have meant that the circuitwould be full of compromises. 14

12-26

One of the less pleasant aspects of programming is having to spendhours just typing in a BASIC program. You arrive at line 8760 andhave to type: P-O-K-E-P-T-,-A-S-C-(-M-I-D-S-(-X-$-,-S-,-1-)-) ... orsomething similar and wonder how secretaties can type the wholeday long.Fortunately there is a cure for this ailment. Shortened forms of theBASIC instructions can be used: for example 0 for POKE, C. for ASC,M for MID$ and so on. All that is needed to enable this shorthand tobe used is a small machine code program intended for 6502 -basedsystems, and the Junior Computer in particular. Then you canconcentrate on your program instead of having to worry about thetyping.

The purpose of the machine code pro-gram given here is to provide an abbrevi-ation for a number of BASIC instructions(particularly the long ones, like RIGHTS)so that they do not have to be typed outlonghand every time. A single letter willbe enough to identify an instruction if it ispreceded by the ASCII code 1BHEx, inother words if the Escape key is firstpressed. This indicates to the computerthat the next character is not an ordinaryone and should be treated as theabbreviation for an instruction. An Rfollowing an Escape would then giveREAD, and P would give PRINT. The firstfunction of our routine is to filter theEscape code. The following charactermust be one of those that corresponds toan abbreviation. When this has been con-firmed the program then outputs the com-plete instruction as if it had been typed inletter by letter via the keyboard.

Two look -up tablesThe whole routine is relatively simple butit does make use of some rather clevervector manipulations. The flowchart shownin figure I should make it easier tounderstand. Clearly this 'program' is reallyonly a subroutine and the user exits fromit by means of an RTS command. Theclever part consists of changing the return

address to our routine just before leavingit using the RTS instruction. But let's startat the beginning.When BASIC is waiting for somethingfrom the user, or, to be exact, from thekeyboard, it enters a wait loop that it onlyleaves when it receives the ASCII codefor CR (carriage return). This characterreceiving loop is where we enter thescene. In order to do this we must changeone vector: the address of the receptionroutine (RECCHA, for example) isreplaced by the address of the routine towhich we want to send the processor,which in this case is the address of labelSHHAND at EE00HEX In the Junior Com-puter and similar systems this change isdone at the level of the DOS input/outputdistributor. This distributor is made up oftwo bytes, one for inputs (2321HEX) aridthe other for outputs (2322HEX). Each bitin these two bytes corresponds to aspecific input or output routine (keyboard,RS232 output, Centronics output, memory,etc.), whose addresses are found in alook -up table (2301...231F). In this tablewe replace the address for the routine toreceive a character from the keyboardwith the address of the routine describedin this article.We are then at the cold start entry offigure 1. A character is first read from thekeyboard and analysed. If it is not thecode for the Escape key the routine stops

shorthand BASICelektor december 1984

short-handBASTCshort-handBASECshort-handBASIC

allows BASICprograms to betyped two orthree times asfast as normal

12-27

shorthand BASICelektor december 1984

Figure 1. This flowchartshows how the abbrevi-ation routine itself deter-mines from which entry itis started. Its decision isbased on whether theprevious character re-ceived is the last in achain corresponding tothe abbreviated instruc-tion.

ABSANDASCCHRSCOSDATADEFDIMDISKENDEXITEXPFORGOSUBGOTOINPUTINTLEFTSLENLISTLOGMID$NEWNEXTNOTPEEKPOKEPOSPRINTREADREMRESTORERETURNRIGHTSRNDRUNSGNSINSPCISORSTEPSTOPSTR$TAB(TANTHENTRAPUSRVAL

BA

HC

D

K

J

F

3L

MFF (OCHE)()N

E

0LF (OAHEX)

R

P

BS (08HEX)

9

CR (ODHEX)

5

SP (20HEX)0

WS

MT (09HEX)7

YU

T

Table 1. The BASIC in-terpreter has itself a look-up table where it can findthe reserved words cor-responding to instruc-tions. This table allows usto reconstitute the com-plete instructions fromabbreviations.

immediately and the character is treatednormally. If, on the other hand, the charac-ter in question is the Escape code thecursor starts flashing to indicate that thespecial abbreviation routine is in oper-ation. The next character can either bethe Escape code again, in which case theroutine is stopped, or one of the abbrevi-

1

stop tuner Mining

the input net., muttpoint to the midnut entry

ranee bit 7 of theMaranter n AHOLDto WO

Input/output distributor:

the input net., minpoint to the mid nonentry

COLD STAR)ENTRY

IJr/ tOanith".')

',tart cursor fin -sin;

ItetiT, 1 Marano.(kryboarel)

---I

rood a otorantsr fromthe taWe at S*734

the input note, rout:Pont to the navy,ran entry

chancter in trans-ferred to BASIC viaAHOLD

1281: 10 64 Be It 45 4E C4 46 IF D2 4E 45 58 04 44 41 .1..01.F0J401.0A

1291: 54 CI 49 4E 5/ 55 04 44 4/ CO 52 45 41 C4 4C 45 T.11IP1.01.W A.IX

1211: D4 47 IF 54 CF 52 55 CE 49 C6 52 45 53 54 4F 52 .40.111.1.9ESTIA

1290: C5 47 4F 53 55 C2 52 45 54 55 52 CE 52 45 CO 53 .6051.1.BEILB.RE.5

1201: 54 41 1:41 4F CE 45 44 49 04 54 52 41 DI 45 53 49 TO.O.EDI.TRA.041

l'A.41: C4 44 4? 53 CB 44 45 Ch 51 F 48 C5 51 52 49 4E .019.DE.PO4.P101

12E1: 04 43 4F 4E DI IC 49 53 04 43 4C 45 41 02 4E 45 .CCH.L1S.CLEAJE

12F1: D7 54 41 42 AS 54 CF 46 CE 53 51 43 AO 54 49 45 .743.T.F.SK.TIE

1314: CE 4E 4F 04 53 54 45 DI 49 AD AA AF DE 41 4E C4 .40.STE

1311: 4F D2 BE E0 EC 53 47 CE 49 4E 44 41 42 D3 55 53 O. -58.0118.M

1321: D2 46 52 C5 51 4F 03 M 51 D2 52 4E C4 4C * C7 .FR.P0.92.R4.1.0.

1331: 45 58 DI 43 * 03 53 49 CE 54 41 CE 11 11 SI 51 E4.03.910A....P

CAI: 45 45 C8 4C 45 CE 53 54 S2 A4 56 41 CC 41 53 C3 EE.U.STR.III.AS.

1351: 43 4a 52 FA 4C 45 46 54 Al 52 49 47 43 54 A4 40 CHZ.LEFT.111941.14

1361: 49 44 Al 11 4E CA 53 CE 52 C7 4F C4 46 C3 4F D6 10..N.S.R.0.F.0.

1371: 4F CD 55 CO 42 aa 44 C4 2F ES 49 C4 54 CD 4C 03 O.U.8.0./.1.7.I.

ations listed in the look -up table repro-duced in the listing. The 6502's Y registerserves as an index while this table isbeing referenced. Whenever the charac-ter received after the Escape correspondsto one of those in the table the processorcan locate the complete instruction basedon the contents of index register Y. All ithas to do is seek it in another look -uptable located in the BASIC interpreterstarting at address 0284HEX. As we cansee from table 1, all the instructionsknown to the interpreter are found there.In order to distinguish them from oneanother the ASCII code for the lastcharacter in each instruction has beenchanged. Its bit seven, which is normally'0', is set to '1' and then serves to indicatethe end of an instruction. An example ofthis is seen at 0286HEX; this addressshould contain 44HEX (the 'D' in END) butit actually contains C4HEX.

Changing the vectorsNow we have arrived at the mostinteresting part of the program: the coldstart entry. The processor then loads acharacter from the look -up table indexedby register Y and examines its bit 7. If it islogic low it is not the last character in thechain so there are more that must beloaded to complete the instruction. Thisexplains the changing of the vector forthe input distributor so that in order toreceive the next character the processorreturns to the warm (rather than cold)entry to our routine. As soon as thecharacter received has been converted toBASIC (the character is stored in bufferAHOLD while the RTS instruction is car-ried out) we return to the abbreviationhandling routine, this time by the warmstart entry. A new character is then loadedfrom the look -up table. If its bit 7 is logichigh this means that the instruction is nowcomplete. The cursor flashing can now bestopped and then the input distributorvector is again changed so that it onceagain points at the cold start entry to ourroutine.Before the last character (stored inAHOLD while the RTS instruction is beingexecuted) is transferred to BASIC its bit 7must be reset to zero. The whole abbrevi-ation routine is carried out in a fraction ofa second. The user presses the Escapekey and then R, for example, and theword READ appears immediately on thescreen.The complete listing of this machine coderoutine is given in table 2. The outlinesthat are shown in the flowchart of figure 1axe easily picked out. There are still somethings that should be said, however. As wehave dealt with the working of this routinein some detail it should be quite easy tochange it to suit any system other than theJunior Computer. The flashing cursor isjust an 'accessory; it could be replacedby another signal if you prefer. Note theabsolute addresses: the input distributor(IOTABL), the buffer for the character thatis being transferred (AHOLD), the

12-28

shorthand BASICelektor december 1984

11:8: 1949

9922:

163#:

8171:

331:

:11:

4129:

9137:

914i:1151:

1171: Eiii9:39: Rif

:1.6 9221: 3111331: 1849

1:41:9:54:92:4:827i: Eiii823:

$233:

12:8: Eiii433:

1248:

1354:

9361:

321: Ti1231: 1913 C9 134396: 345143: 1997 648411: 1413 Al

143: 149A E0 fi143: FAO OD re9449: 311 II 34-454: 1112 ED 11 re1461: 915 A2 434479: 317 29 13 FE1493: ElIA C9 SI9494: EOM 99 46139: (HE C9 738511: £129 ES 111579: 1122 29 DT*134: 1824 3 8$1541: E125 Cl 35951: 323 CO 79 31564: E1179 Ti 45

1157i: DIM CA1533: 195 It F45579: E959 31 E3

1311: 302 ES1911: 1123 Ai FF9621: Ei35 CA9631: (736 Ft H#644: E1331651: Ein 39 $4 42*SEC EIX 19 FA1E71: EtE 31 F5

E444 X IC Ea1691: E143 AC 9C Et4194: Ei146 CE

1711: (147 99 94 12173: El44 E0 63 231739: 1140 3 IC1741: El* EC EC Ei11751: E452 A2 42

1761: EVA AI (11771: (156 EE 11 73173: En? EC 12 23173: EIX 6I831: EIX A9 I:;tall: [157 Ti 48 re

E162 AO 11 Di

CFS $0419

9C1171F40 M311 COMES 713 MCA DIF1113

CA1611iV. FOP 9iPETTA4D II NODfCLESW CIFFP -11: 'MICRO. 114Y 1414'. HEW J.

KIER TFEUITMEN

05659 IIFTJT DISN19 TkIE

1914a.

CPT XOWS1S

ik 1WILE 1

Ttlf1

93113

18146

$2311

#D391

AR

$7363

SEW

EaE3(4.. 93.,TDES

7E4042 i 47E13

103.-LI4 Tan

sizi;

if 11,11.41...XPeti

CRT XOW-SS FEBISTEP

4ii WEISTES FILE

ACOMIAT89 Hip71014C6VaY Y-BLF1E9

Kam C7041:47121 F701 .Zr936AD

M51C 031140 LCCKP T48.1

34.19E, 411 KOCHI 611 Of:WM FP31 FEY33:R3Of SIB IS IT ESCAK9BEO FICA IF YES. W41041185 IF SO. PETRI TO MEM

FICLR LCA111 HA

ETA AP ELECT CIESCP. ONUS_ 71315114LCA ;Tr.!4:91:1D1 la SET 3.86 FOR FLA941.915 055:7ETA WILE124111 $4? LEA? 314X. TAKE KU2511 FECE$A EET 94341.4490 0119140 9909

/MAP Of1/1 $61KC SENO 5.7401 IF 0.TFACTER CWIN $78ECS SE44781 TAO IF DWARF; )44421M ICI TLFH OW. IS XV! IWO FAPITXOFDI 618 15 IT EWE?al; 103104 IF YES. ETIF81 TO 893ICOn Dar COFRE 81139 TAMEEE2 FWD Ftup 111 1504 WA&DE( FEXT TEY

EP_ X.47,34 IF FDT PM. LIP Ta311 11,...13.143 Wig? MERE PhD LET FEM 0119990

FWD MX 75460 X ANDW101 47T Y FDA LOCH), IN EASIC 034$-V4 148.E

WOW CD !Ea BASIC calm139 S4.EY 4.1P11.43 AT 03WEVI 031910? 349(14

SKIP NY ILT YET PRIMP SX11 C1IW57 C1111:812LOST 9:64-01 COE YET'EFL SaP fir LOD. BXX311 MO1931139 HY MDT Of

Ail STY 1131143 SALE Y -MISTERCEIDD LOY TINY WALL 9-PESISTER

DIY DEMENT DAR.POKEPlOAY EASC01 ET CIE OANCTER 9791 CaiVeC,STA MID HID OffiXTER POI EASIC 1/f1:1311 LAST04 LAST OW. FLOW TIEN T.FteriSTY TEM SSE Y-WEISTDIMIN $42 EE100 AX6E5 -11 TO XLIMN $a MID Y-WEIST3

5109E STX 10TC8. 4iC815 IN X- AD Y-TEEISTER TOSTY IOTTEL .11 WIC [FRIT VECITS TAXI91$ REM TO MSIC

IASTCH U117( 140.RA CR SELECT CLRE.T DYTP8. P31519LEA WILE

HU: E465 29 if1941: ($47 ED re*938: UM A? 7FKat 136C M 63 231879: fig ED 63 231991: 372 A2 FT19.91: 1174 At if4934: £976 CE Cl311:4921:

9931:

1741: 5111-4410 11.10 9a.1*999:I764: 1973 = '2 001971: Fill 46 = 'T Fx

Ei7A 4E = HUT

MS: 379 44 = '0 DATA!Hi: WC 49 '1 IffLITMI: 370 31 = '1 D1311129: EiN 52 = '91131: EiN FT ,FF

1141: 1434 47 = 'S SOTO1151: £431 10 = 180 91)91661: OH FT = STF8971: 383 fa = 413 WETCP£113: 1134 2EWI: 145EH: EWE r. = '2 el1111: 337 57 = '4 51191131: Et93 FT = STT113: 1431 FT 1FF1144: E494 59 = '1 TPA=1159: ELM 'X EXIT113: EtX 'X 01941171: EM 44 = $44 CET1191: EtE 4f = '0 331E1191: E#1 58 'P PPM1214: WI FT = STT1211: 1191 X 'L LIST1221: E992 FF = *FF123: E993 IC = 41,21244: (*54 89 = 'Pet161: E125 FF - 4991264:599691 = 1171123: E997 29 5PC41291: un 54123: Eli? 2D)31a:Etii.- 'S STEP1211: Esira FF = ICC

IM1: UPC W = AT13.4: EP) FT = SU.130:151: El* FT- = 431361: EMI 41 = 'A *01271: (MI FT =1331: Et* FT333: EIA3 FT 177RH: E4i4 FF1411: ES* 33 = 584143: EMS M Da!AN: E47 42 = '8 A%1441: 35:9 55 = LISP.1451: EFA9 TT = SIC1