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in a box

From your usual component
supplier or direct from ••

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Ellen Steet, Portslade,

Brighton BN4 1EQ
Telephone: (0273)414371
Telex = IDACON BRIGHTON 87443

idvertisement

elektor june 1976 — 601

raiT

Many Elektor circuits are accompanied by designs for printed
circuits. For those who do not feel inclined to etch their own
printed circuit boards, a number of these designs are also available
as ready-etched and predrilled boards. These boards can be ordered
from our Canterbury office. Payment, including £ 0.15 p & p, must
be in advance. Delivery time is approximately three weeks.

Bank account number: A/C No. 1 1014587, sorting code 40-16-1 1
Midland Bank Ltd, Canterbury.

circuit

number

issue

price

% VAT

AUDIO

austereo 3-watt amplifier

HB1 1

5

1.15

(12.5)

austereo power supply

HB1 2

5

0.55

(12.5)

austereo control amplifier

HB1 3

5

1.55

(12.5)

austereo disc preamp

HB1 4

5

0.65

(12.5)

edwin amplifier

97-536

6

1.25

(12.5)

miniature amplifier

1486

6

0.55

(12.5)

equa amplifier

1499

1

1.55

(12.5)

equin

9401*

13

2.15

(12.5)

tap preamp

4003

4

1.95

(12.5)

tap power

tap preamp front panels:

9072*

7

2.-

(12.5)

power

1626A

7

1.65

(12.5)

input

1626B

4

1.65

(12.5)

volume

1626C

4

1.65

(12.5)

tone

1626D

4

1.65

(12.51

width

1626E

4

1.65

(12.5)

730/740 (1C control amplifier)

9191*

8

1.15

(12.5)

disc preamp 76131

4040A

3

1.05

(12.5)

preco, preamplifier

9398*

13

2.-

(12.5)

preco, control amplifier

9399*

13

1.15

(12.5)

dnl

1234

11

0.85

(12.5)

electronic loudspeaker

1527

2

0.55

(12.5)

compressor

6019A

3

1.50

(12.5)

RF

coilless receiver for MW and LW

3166

5

0.85

(12.5)

super-plam, main p.c.b.

601 2-1 b

11

2.05

(12.5)

super-plam, detector a

601 2-2a

11

1.10

(12.5)

super-plam, detector b

601 2-3a

11

1.25

(12.5)

ssb receiver

6031*

11

2.25

(12.5)

mini MW receiver

9369*

9

0.70

(12.5)

FM/TV

pll stereo decoder MCI 31 OP

1477

9

0.75

(12.5)

CA3090AQ stereo decoder

9126*

5

0.80

(12.5)

tv sound

6025

2

1.75

(12.5)

tv sound, front-end

9357*

11

1.30

(12.5)

ota pll

feedback pll fm receiver

6029

7

1.15

(12.5)

(3 boards)

9356*

9

4.05

(12.5)

aerial amplifier

1668

1

1.15

(12.5)

integrated indoor fm aerial

9423*

13

0.80

(12.5)

CARS

car power supply
digital rev counter (control

1563

4

1.50

( 8 )

p.c.b. only!)

1590

1

1.35

( 8 )

car anti-theft alarm

1592

4

1.70

( 8 )

GAMES

beetle

1492

4

2.35

( 8 )

tv tennis, main pcb

9029-1 A*

7

4.40

( 8 )

tv tennis, modulator/oscillator

9029-2*

7

1.05

( 8 )

tv tennis, 5-volt supply

9218A*

7

0.90

( 8 )

tv tennis extensions

9363*

13

5.15

( 8 )

die

9169*

8

0.80

( 8 )

RHYTHM AND SOUND

minidrum gyrator

1465A

2

0.95

(12.5)

minidrum mixer/preamp

1465B

2

0.60

(12.5)

minidrum noise

1465C

2

1.25

(12.5)

minidrum tap

1 621 A

2

0.90

(12.5)

minidrum ruffle circuit

1 621 B

3

1.15

(12.5)

automatic bassdrum

1 621 C

3

0.90

(12.5)

microdrum

1661

2

1.05

(12.5)

rhythm generator (M252AA)

9110*

5/12

0.90

(12.5)

rhythm generator (M253AA)
ic drummer, instruments

9344-3*

12

1.20

(12.5)

mother board
ic drummer, instruments

9344-2*

12

1.70

(12.5)

daughter board

9344-1 *

12

0.30

(12.5)

screening for master oscillator

4011 A

10

0.30

112.5)

master oscillator AY10212

401 IB-2

10

1.30

(12.5)

ancillary supply for m.o.

401 IB-13

10

0.95

( 8 )

big ben 95

5028

2

1.50

(12.5)

7400 siren

9119*

5

0.80

(12.5)

circuit

TIME-KEEPING

mos clock 5314 clock circuit
mos clock 5314 display board
mos clock timebase
versatile digital clock
clamant clock, alarm
clamant clock, time signal
clamant clock, striking system
car clock (2 boards)
car clock front panel
(transparent red plastic)
kitchen timer
digital watch (date only)
digital watch (day/date)

DISPLAYS

twin minitron display
twin led display
twin decade counter
maxi display

UAA170, 270° meter, basic
board

UAA170, 270° meter, front
panel

TEST EQUIPMENT

universal frequency reference

distortion meter

a/d converter

recip-riaa

dil-led probe

frequency counter,
control logic

frequency counter, minitron
display board
frequency counter, led
display board

frequency counter, counter/
latch/display driver
frequency counter preamp
frequency counter,

—5 V supply
tup/tun tester
tup/tun tester front panel
p.c.b. and wiring tester
fm test generator
capacitance meter
versatile logic probe
UAA170, LED voltmeter,
basic board

UAA170, 16 LED display
board

MISCELLANEOUS

tap sensor

mostap

light dimmer

ttl +5 V supply

integrated voltage regulator

automatic call-sign generator

stylus balance

Polaroid timer

number

issue

price % VAT

1607A

1

1.65

( 8

)

1607B

1

1.20

( 8

)

1620

4

0.85

( 8

)

4414B

6

1.40

( 8

)

4015-13

7

1.45

( 8

)

4015-16

7

1.-

( 8

)

4015-27

8

1.35

( 8

)

7036

6

2.20

( 8

)

7036-3

6

1.15

( 8

)

9147*

5

0.85

( 8

)

9397-1*

10

0.80

( 8

)

9397-2*

10

0.80

( 8

)

4029-1

2

1.95

( 8

)

4029-2

2

1.95

( 8

)

4029-3

2

1.95

( 8

)

4409

2

2. -

( 8

)

9392-1 *

12

1.40

( 8

)

9392-2

12

1.90

( 8

)

HD4

5

1.40

( 8

)

1437

1

2.20

( 8

)

1443

3

1.05

( 8

)

4039

2

0.90

( 8

)

5027A+B

2

2.45

( 8

)

9033*

7

1.50

( 8

)

9312*

7

1.30

( 8

)

9313*

7

1.30

( 8

)

9314*

7

1.05

( 8

)

9031-1*

8

1.30

( 8

)

9031-2*

8

0.85

( 8

)

9076*

4

2.05

( 8

)

9076/2A

4

2.30

( 8

)

9106*

5

0.60

( 8

)

9155*

10

0.85

( 8

)

9183*

5

0.85

( 8

)

9329*

13

1.05

( 8

)

9392-3*

12

1 .-

( 8

)

9392-4*

12

0.85

( 8

)

1457

1

0.85

( 8 )

1540

2

1.30

( 8 )

1487

6

0.55

( 8 )

4046

7

1.05

( 8 )

7043b

11

0.80

(12.5)

9017*

10

2.85

( 8 )

9343

12

0.40

(12.5)

9379*

12

1.20

(12.5)

NEW

digibell

9325*

14

1.90

( 8

)

led light show

9403*

14

2.55

( 8

)

fet front, preamp

9413*

14

0.80

( 8

)

fet front, probe

9427*

14

0.70

( 8

)

* with solder mask

All prices include VAT at

the rate shown in

brackets.

602 — elektor june 1976

publisher's notici

elektor decoder

What is a TUN?

What is 1 0 n?

What is the EPS service?
What is the TQ service?
What is a missing link?

Semiconductor types

Very often, a large number of
equivalent semiconductors
exist with different type
numbers. For this reason,
'abbreviated' type numbers
are used in Elektor wherever
possible:

— '741' stands for juA741,
LM741 , MC741 , MIC741,
RM741, SN72741, etc.

— 'TUP' or 'TUN' (Transistor,
Universal, PNP or NPN
respectively) stands for any
low frequency silicon
transistor that meets the
specifications listed in
Table 1 . Some examples
are listed below.

- 'DUS' or 'DUG' (Diode,
Universal, Silicon or
Germanium respectively)
stands for any diode that
meets the specifications
listed in Table 2.

- 'BC107B', 'BC237B',
'BC547B' all refer to the
same 'family' of almost
identical better-quality
silicon transistors. In
general, any other member
of the same family can be
used instead. (See below.)

For further information, see
'TUP, TUN, DUG, DUS',
Elektor 1 2, p. 458.

Table 1 . Minimum
specifications for TUP (PNP)
and TUN (NPN).

VCEO.max

20V

*C,max

100 mA

hfe.min

100

p tot,max

100 mW

^T,min

100 MHz

Some 'TUN's are: BC107,
BC108 and BC109 families;
2N3856A, 2N3859, 2N3860,
2N3904, 2N3947, 2N4124.
Some 'TUP's are: BC177 and
BC178 families; BC179 family
with the possible exception of
BC159 and BC1 79; 2N241 2,
2N3251 , 2N3906, 2N4126,
2N4291 .

Table 2. Minimum
specifications for DUS (silicon)
and DUG (germanium).

DUS

DUG

VR.max
* F,max
' R,max
Ptot,max
^D,max

25 V

100mA

1mA

250mW

5pF

20V

35mA
IOOju A
250mW
lOpF

Some 'DUS's are: BA127,
BA217, BA218, BA221,
BA222, BA317, BA318,
BAX13, BAY61 , 1N914,

1 N4148.

Some 'DUG's are: OA85,
OA91 , OA95, AA116.

BC107 (-8, -9) families:

BC107 (-8, -9), BC147 (-8,-9),
BC207 (-8, -9), BC237 (-8, -9),
BC317 (-8, -9), BC347 (-8, -9),
BC547 (-8, -9), BC171 (-2, -3),
BC182 (-3, -4), BC382 (-3, -4),
BC437 (-8, -9), BC414

BC177 (-8,-9) families:

BC177 (-8, -9), BC157 (-8, -9),
BC204 (-5, -6), BC307 (-8, -9),
BC320 (-1,-2), BC350 (-1,-2),
BC557 (-8, -9), BC251 (-2, -3),
BC212 (-3, -4), BC512 (-3, -4),
BC261 (-2, -3), BC416.

Resistor and capacitor values

When giving component
values, decimal points and
large numbers of zeros are
avoided wherever possible.

The decimal point is usually
replaced by one of the
following international
abbreviations:

P

(pico-) =

10“

n

(nano-) =

10“

(micro-) =

10“

m

(mill i-) =

10“

k

(kilo-) =

10 3

M

(mega-) =

10 6

G

(giga-) =

10 9

A few examples:

Resistance value 2k7: this is

2.7 k ft, or 2700 £7.
Resistance value 470: this is

470 n.

Capacitance value 4p7: this is

4.7 pF, or

0.000 000 000 004 7 F . . .
Capacitance value 10 n: this is
the international way of
writing 10,000 pF or .01 pF,
since 1 n is 10' 9 farads or
1000 pF.

Mains voltages

No mains (power line) voltages
are listed in Elektor circuits. It
is assumed that our readers
know what voltage is standard
in their part of the world!
Readers in countries that use
60 Hz should note that
Elektor circuits are designed
for 50 Hz operation. This will
not normally be a problem;
however, in cases where the
mains frequency is used for
synchronisation some
modification may be required.

Technical services to readers

— EPS service. Many Elektor
articles include a lay-out
for a printed circuit board.
Some — but not all — of
these boards are available
ready-etched and
predrilled. The 'EPS print
service list' in the current
issue always gives a
complete list of available
boards.

— Technical queries.

Members of the technical
staff are available to
answer technical queries
(relating to articles
published in Elektor) by
telephone on Mondays
from 14.00 to 16.30.
Letters with technical
queries should be
addressed to: Dept. TQ.
Please enclose a stamped,
self addressed envelope;
readers outside U.K. please
enclose an IRC instead of
stamps.

— Missing link. Any
important modifications
to, additions to,
improvements on or
corrections in Elektor
circuits are generally listed
under the heading 'Missing
Link' at the earliest
opportunity.

Volume 2
Number 6

Editor

Deputy editor
Technical editors

Art editor
Drawing office
Subscriptions

W. van der Horst
P. Holmes

J. Barendrecht
G.H.K. Dam

E. Krempelsauer
Fr. Scheel

K. S.M. Walraven
C. Sinke

L. Martin

Mrs. A. van Meyel

UK editorial offices, administration and advertising:

6 Stour Street, Canterbury CT 1 2XZ.

Tel. Canterbury (0227) - 54430.

Telex: 965504.

Bank: Midland Bank Ltd Canterbury A/C no. 11014587,
Sorting code 40-16-11, giro: no. 315 4254.

Assistant Manager and Advertising : R.G. Knapp
Editorial : T. Emmens

Elektor is published monthly on the third Friday of
each month, price 40 pence.

Please note that number 15/16 (July/August) is a
double issue, 'Summer Circuits', price 80 pence.

Single copies (including back issues) are available by
post from our Canterbury office to UK addresses and
to all countries by surface mail at £ 0.55.

Single copies by air mail to all countries are £ 0.90.
Subscriptions for 1976 (January to December inclusive):
to UK addresses and to all countries by surface mail:

£ 6.25, to all countries by air mail £ 11,—.

Subscriptions for 1976 (July/August to December inclusive):
to UK addresses and to all countries by surface mail: £ 3.05.
All prices include p & p.

Subscribers are requested to notify a change of address
four weeks in advance and to return envelope bearing
previous address.

Letters should be addressed to the department concerned:

TQ = Technical Queries; ADV = Advertisements;

SUB = Subscriptions; ADM = Administration;

ED = Editorial (articles submitted for publication etc.);

EPS = Elektor printed circuit board service.

For technical queries, please enclose a stamped, addressed
envelope.

The circuits published are for domestic use only. The
submission of designs or articles to Elektor implies
permission to the publishers to alter and translate the text
and design, and to use the contents in other Elektor
publications and activities. The publishers cannot
guarantee to return any material submitted to
them. All drawings, photographs, printed circuit boards and
articles published in Elektor are copyright and may not
be reproduced or imitated in whole or part without prior
written permission of the publishers.

Patent protection may exist in respect of circuits, devices,
components etc. described in this magazine.

The publishers do not accept responsibility for failing to
identify such patent or other protection.

Distribution: Spotlight Magazine Distributors Ltd.,

Spotlight House 1, Bentwell road, Holloway,

London N7 7AX.

Copyright © 1976 Elektor publishers Ltd — Canterbury.
Printed in the Netherlands.

:ontent$

elektor june 1976 — 603

selektor 608

channel quadrupler — Dipl. Ing. H. Weidner 610

A single-beam oscilloscope is often insufficient nowadays for testing electronic circuits. This article describes a
multi-channel switch with which four signals may be displayed simultaneously.

measuring pencil — J. Hajek 612

vhf fm reception 613

Owners of FM tuners may often wish to know what sort of signal level they can expect to receive in the
locality in which they live. This article investigates the rules governing VHF propagation and shows how
received signal strengths may be estimated with a few simple calculations.

triac control 617

a.m. mains intercom 618

Mains intercoms of a more or less reasonable quality are still a bit expensive on the market. Consequently,
there appears to be a fair demand for a cheap a.m. intercom which will be useful in certain applications where
mains interference is not excessive.

fet front 620

HF preamp and FET probe for frequency counter.

missing link: link 75 624

ejektor 625

An invitation to investigate, improve on and implement imperfect but interesting ideas.

vertical fets 628

The Japanese have now developed a semiconductor called 'vertical field effect transistor', intended for use in
high power output stages. This article describes the V-FET's construction and operation, along with its appli-
cation in commercial circuits.

led light show 634

Small is beautiful, as they say, and the LED light show can brighten up the front panel of an amplifier, tuner
or tape recorder.

digibell — R. Janssen 638

A design for an electronic doorbell that plays the well-known 'Westminster Chime'. The only tuning necessary
is a single adjustment to set the entire melody in the required key.

market 641

604 — elektor june 1976

advertisemei

ELECTRONIC COMPONENT DISTRIBUTORS
P.O. Box 25 Canterbury Kent

Telephone: Canterbury (0227) 52139

Elektor

printed circuit boards and binders.
Prices as in this issue

Component kits and individual components
available by return of post from stocks at
Canterbury. All prices include VAT and P.+P.

741-8/1 4DI L £0.22

E.1109

. £6.08

7400

. .£0.15

7038A

. .£3.68

7401

. .£0.15

TBA231 . . .

. £1.02

7405

. .£0.19

CA1310AE.

. £2.27

7447

. .£1.20

CA3080 . . .

. £0.79

7473

. .£0.30

CD4011AE .

.£0.23

7495

. .£0.69

CD4017AE .

.£1.76

74121

. £0.32

CD4049AE .

.£0.67

MM5314N .

. £4.77

TBA120 . . .

. £1.24

SFE 6 mA (6 MHz Filter) £0.90

l/C EXTRACTOR £0.55 NE555V £0.65

l/C INSERTER £1.40 2N3055 £0.54

Crystals for any requirement
PH 100 5-digit 30 MHz freq. counter £99.50

Above types are partial examples.

Write or phone for details.

7 p.m. to 9 p.m. phone Dover (0304) 812332

Stock List free on request.

FM Aerials

The Fuba UKa Stereo range of
aerials provide complete
coverage of high quality and
high performance FM aerials.
The Fuba Uka Stereo 8 is
famous for really good long
distance reception. v

UHF TV Aerials

The famous Fuba XC 3 range
of UHF TV aerials, and the
unique AKV 450 “Active
Capsule” amplifier which
converts the passive aerial to
an active one, will often
provide out of area TV* \ \
channels. v \

XC391

The unique Fuba
indoor active FM aerial
gives a level of performance
not previously obtainable
with indoor aerials.

'Full set of leaflets sent on receipt of large SAE with 9p stamp. Please mark envelope Cat. E.
Prices will be included.

SPECIAL OFFERS for a limited period only.

Stolle Automatic aerial rotator with control unit at £ 39.80 including VAT and 15% discount.
Carr free.

Exa UKW 2 FM aerial 2 elements; anodised type finish, £4.85 including VAT, carr and 20%
discount.

5 Way rotator control cable, 20 metere length £4.00 including VAT and carriage.

Teldis 2 stage ultra broadband mast head amplifier and mains power supply unit, £ 13.70
including VAT and carriage and approx. 25% discount.

All offers apply for
when ordering.’

4 weeks from date of publication. Please refer to this advertisement

All products available from us CWO, Access or Barclaycard.

Audio Workshops Ltd

29 HIGH STREET ROBERTSBRIDGE. SUSSEX. TEL ROBERTSBRIDGE 88058C

(STD 058C

Phoenix Electronics

iSolent) Limited

46 OSBORNE ROAD,

SOUTHSEA, PORTSMOUTH, HANTS.
CALLERS AT OUR SHOP WELCOME

Components and tools supplied guaranteed
from franchise agreements. Member of
AFDEC — the franchised component distribu-
tors association. Our catalogue sent for 20p
including postage. All prices include VAT.
Carriage is 20p extra on each order — mini-
mum value £ 1

TTL -93 TYPES

AVAILABLE

7400

£0.17

7401,2,3,4,5,10

£0.21

7413,70,74

£0.33

7441,2,91

£0.95

7481,2,151,1 57

£1.35

7490

£0.75

7492,3

£0.89

74121

£0.59

74190,1

£2.20

74192,3

£ 1.99

LINEAR CIRCUITS

TRANSISTORS

BC1 07,8,9

£0.11

301 A, 307, 709, 741

£0.39

BC1 77,8,9

£0.15

723 regulator

£0.49

BC1 82L,3L,4L

£0.09

537,558 dual

£0.59

BC204,5,6

£0.14

747 dual

555 timer

£0.69

£0.85

BC207,8,9

£0.09

309K regulator

£ 1.50

BC21 2L,3L,4L

BDY56

£0.10

£1.72

DTL - 1 1 TYPES AVAILABLE

BD1 35,6

2N221 9,20,21,22

£0.37

£0.22

Gates from

£0.29

2N2904,5,6,7

£0.24

Flip-flops from

£0.39

2N3442,BDY53

£0.88

DIODES

AA143.4.0A200
1N914.6 ,4148,9
1N4001-7
1 N5402-6

ZENERS 5%

’/2 Watt 3.3-1 5V
1 Watt 4.7-24V
10 Watt 8. 2-24 V

BRIDGES 1-AMP P.C.

WOO 5 50V
W08 800V

£0.08
£0.06
£0.07-£0.13
£ 0.1 7-£ 0.21

£0.11

£0.22

£0.83

£0.27

£0.40

RESISTORS ’A WATT

Metal film 2% 30R-300K

CAPACITORS

Aluminium electrolyc, Polyester,
Ceramic disc. Tantalum

CONNECTORS, CLIPS.

KNOBS, LAMPHOLDERS,
SWITCHES, FUSEHOLDERS,
FUSELINKS

All available in a wide range of
sizes and designs

SOLDERING

EQUIPMENT

Weller 'Marksman' £3.02

Adcola 'Invader' £3.11

Weller 'Expert' Gun £7.84

'marksman' Stand £2.18

'invader' Stand £1.86

R500 Desolder Iron £11.60

SOLDER AND
DESOLDERING BRAID
AVAILABLE.

WIDE RANGE OF
SOLDERING ACCESSORIES

INTRODUCTORY OFFER TO ELEKTOR
READERS SPECIAL VALUE BARGAIN PACK
INCLUDING:

Small signal transistors — Triacs — Plastic power transistors —
Diodes — HV rectifiers — Zeners. At least 50 pieces of dis-
crete semiconductors. Integrated circuits — TTLand linear.
Panel hardware selection including: Knobs — Jacks — Con-
nectors — Fuses — Aluminium electrolytic, ceramic and
film capacitors.

Total value at least £ 10 — sent with our new catalogue at
an inclusive price of £ 3, post free.

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elektor june 1976 — 605

Join the Digital Revolution

Teach yourself the
latest techniques of

digital electronics

Computers and calculators are only the beginning of the
digital revolution in electronics. Telephones, wristwatches.
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some of the application areas in the next few years.

Are you prepared to cope with these developments?

This four volume course — each volume measuring
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step-by-step with hundreds of diagrams and questions
through number systems. Boolean algebra, truth tables,
de Morgan's theorem, flipflops. registers, counters and
adders. All from first principles. The only initial ability
assumed is simple arithmetic.

#

At the end of the course you will have broadened your
horizons, career prospects and your fundamental under-
standing of the changing world around you

Design of
Digital Systems

Bookl

• • • „ •

• «• • • • * •

Also available - a more
advanced course in 6
volumes:

1. Computer Arithmetic

2. Boolean Logic

3. Arithmetic Circuits

4. Memories & Counters

5. Calculator Design

Computer Architecture

£6.20

plus 80 p

Offer Order this together
with Digital Computer Logic &
Electronics for the bargain
price of £ 9.70, plus 80 p p & p

p & p.

Design of Digital Systems contains over twice as much
information in each volume as the simpler course Digital
Computer Logic and Electronics. All the information in the
simpler course is covered as part of the first volumes of
Design of Digital Systems which as you can see from its
contents also covers many more advanced topics

These courses were written so that you could teach
yourself the theory and application of digital logic.
Learning by self-instruction has the advantages of
being quicker and more thorough than classroom
learning. You work at your own speed and must
respond by answering questions on each new piece
of information before proceeding to the next.

Guarantee — no risk to you

If you are not entirely satisfied with Digital
Computer Logic and Electronics or Design of Digital
Systems, you may return them to us and your
money will be refunded in full, no questions asked.

Designer

Manager

Enthusiast

Scientist

Engineer

Student

Digital Computer
Logic and
Electronics

A Self -instructional Course

C PG.*ne MA (Cantab)

A W Un«m BA (Cantab)

Book 1

Basic

computer

logic

Book Q

1 Logical
circuit

1 elements

Book J

1 Designing circuits
to carry out
‘ logical functions

Book A

Flipflops

L and
r registers

Digital Comptr
Logic and
Electronics

Book

tlrai

£4.20

plus 80 p packing and
surface post anywhere
in the world

Quantity discounts
available on request.

Payment may be made
in foreign currencies.

VAT zero rated.

r Ei4 1

To: Cambridge Learning Enterprises,

FREEPOST, St. Ives, Huntingdon, Cambs PE 17 4BR

* Please send me set(s) of Digital Computer Logic

& Electronics at £ 5.00 each, p & p included.

| * or set(s) of Design of Digital Systems at £ 7.00

each, p & p included.

• or combined set(s) at £ 10.50 each, p & p included.

Name

I Address

* delete as applicable

No need to use a stamp - just print FREEPOST on the envelope

J

606 — elektor june 1976

advertisement

I wouldn t
give
a dime

for an
elektor

circuit

You don’t have to

on average they cost about
half a dime (2 p) each!

HIGH QUALITY
PROFESSIONAL
AUDIO MODULES

Over the years there has been a growing demand for
high quality audio power amplifier modules. At last and
never before has such quality been offered at such a
reasonable price.

All our modules at JPS are fitted with full output
protection, and have a super High Stability Intergrated
Circuit front end containing within itself no less than
twenty transistors.

All JPS products carry a two year guarantee.

POWER OUTPUT: -i r A

170WR.M.S. 13U

FREQUENCY RESPONSE:

D.C.- 21kHz - 0.2dB
POWER BANDWIDTH:

D.C. -20kHz -0.2dB

POWER OUTPUT:

65 W R.M.S.

FREQUENCY RESPONSE:

D.C. 21kHz 0.2 dB

POWER BANDWIDTH:

D.C. 20kHz 0.2 dB

SLEWING RATE:

8.4V per microsecond
T.H.D: .03%

INPUT SENSITIVITY:*
i OdB (0.775V) 150 W
INPUT IMPEDANCE:* 47k
HUM and NOISE:

>100dB below 150 Watts
DAMPING FACTOR:

>200 to 1kHz

POWER REQUIREMENTS:

±55V D.C.

PRICE: £32.02 (inc. VAT)

SLEWING RATE:

8.6 V per microsecond

T.H.D: .03%

INPUT SENSITIVITY:*

OdB (0.775V) 50W 8 ohms

INPUT IMPEDANCE:* 47k

HUM and NOISE:

>100dB below 60W

DAMPING FACTOR:

>200 to 1kHz
POWER REQUIREMENTS:

±35 V D.C.

PRICE: £19.20 (inc. VAT)

*At a small extra charge , these parameters may be changed
to order. Impedance: Max 250 K - Sensitivity: lOOm/V RMS

\

As both modules are totally D.C. coupled, they may also be
ordered as D.C. amplifiers, the Power Response then being
-OdB + 0.5dB - D.C. to 20 kHz

POWER SUPPLIES below are available upon request:-

PS50 (Drives single 50 Watts) £11.0/ PS150'1 (Drives single 1 50 Watts) £18.15
PS502 (Drives dual 50 Watts) £14.57 PS.150'2 (Drives dual 150W'atts) £23.00

N.B. It is not recommended that the D.C. Modules are used for audio

For

For

Q/50 watt modules @ £32.02 fine. VA Tj
Q 50 watt modules (® £1 9.20 (inc. VA T I

Quantity Discounts upon request . . .

NAME

ADDRESS

installations as extreme low frequencies damage loudspeaker systems.

Please send me further information Q

I herewith enclose Cheque/Postal Order for £

made payable to JPS Associates.

associates

All JPS Products carry a full Two Year Guarantee.

BELMONT HOUSE
STEELE ROAD

PARK ROYAL

Postal Code LONDON NW10 7AR

TELEPHONE 01-961 1274

Wl

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elektor june 1976 — 607

B. BAMBER ELECTRONICS

DEPT E, 5 STATION ROAD, LITTLEPORT, CAMBS., CB61QE
Tel: ELY (0353) 860185 (2 lines) Tuesday to Saturday.

ALL ITEM + 8% VAT
(UNLESS OTHERWISE
MARKED)

. BARGAIN OFFER MIXED COM-
PONENT PACKS, containing resistors,
capacitors, switches, pots, etc., All New,
(Random sample bag revealed approx.
700 items) £ 2.00 per pack, while stocks
last.

TRANSISTOR HEATSINKS, to take 2 x
TO 18 transistors, screw in clamps, block
size Ix'/ix Kin, with.holes for mounting

3 for 50p

. MINIATURE 2 PIN PLUGS & SOCKETS

(Fit into K " hole, pins onclosed, with
covers for chassis mounting, or can be
used for in-lino connectors).

Bargain pack of 3 plugs + 3 sockets +
covers 50p

• PROGRAMMERS (Magnetic Devices)

Contain 9 microswitches (suitable for
mains operation) with 9 rotating cams,
all individually adjustable, ideal for
switching disco lights, displays, etc., or
industrial machine programming. (Need
slow motion motor to drive cams, not
supplied) 9 switch version £1.50

•.HEAVY DUTY HEATSINK BLOCKS,
undrilled, base area 2K" x 2", with

5 fins, total height 2K" 50p each

•9V RELAYS, Continental type, 2 pole
change over 35p

• RUBBER MAGNETS K" square, with

mounting hole 20 for 30p

• SPERRY 7-SEGMENT P.G.D.
DISPLAYS, digit height 0.3 in red, with
decimal points, 150V to 200V (nominal
180V) operation. These are high-volt
industrial type and therefore brighter
than normal displays. All brand new,
AT THE BARGAIN PRICE OF 50p PER
DIGIT.

Typo 332 (two digits in one mount)

£1.00 each

Typo 333 (three digits on one mount)

£1.50

(Sorry, no single digit available). Data
Supplied.

BSX20 Transistors 3 for 50p

BC108 (metal can) 4 for 50p

PBC108 (plastic BC108) 5 for 50p

OC200 Transistors 6 for 50p

BSY95A Transistors 6 for 50p

BFY51 Transistors 4 for 60p

BCY72 Transistors 4 for 50p

PNP audio type TO 5

Transistors 12for25p

Telephone Type earpiece insert .... 50p

IK" Polythene chassis mounting fuse-

holders 6 for 30p

LES Lamps. 24V 1.2W 10for40p

Mullard Tubular ceramic trimmers.

1-1 8pf 6 for 50p

I.C.'s, some coded, 14 Dl L type, untested
mixed 20 for 25p

Miniature slider switches, 2 pole 2 way

5 for 50p

DIECAST BOXES

The range of aluminium alloy diecast
boxes has the unique feature of internal
slots for dividing parts, e.g. screens,
printed circuits boards etc. For use as
screened sub assemblies, as rigid chassis,
as junction boxes, for test sets and for

complete equipment.

In the following sizes:

4.3" x 2.3" x 1.2" approx 85p

4.8" x 2.8" x 1.5" approx 75p

4.8" x 3.8" x 1 " approx 85p

4.8" x 3.8" x 2" approx £1.00

6.8" x 4.8" x 2" approx £1.45

4.8" x 3.8" x 3" approx £1.55

6.8" x 4.8" x 4" approx £2.25

8.6" x 5.8" x 2" approx £1.85

10.6" x 6.8" x 2" approx £2.25

* NO INTERNAL SLOTS
PLUGS & SOCKETS

T.V. PLUGS (Metal Type) . . 5 for 50p
T.V. SOCKETS (Metal Type) . 4 for 50p

T.V. LINE CONNECTORS

(Back-to-back sockets) 4 for 50p

DIN 3-pin LINE SOCKETS 15p each

DIN 3-pin PLUGS 15peach

DIN 6-pin Right-angled

PLUGS 20p each

PLEASE ADD 25% VAT TO ALL DIN
& TV SOCKETS.

BARGAIN PACKS

MIXED DIELECTRIC CAPACITORS
(Approx 100) £1.50

ELECTROLYTICS (LOW VOLTAGE

TYPES) £1.50

(Approx 100)

ELECTROLYTICS (HIGH VOLTAGE

TYPES) £1.50

(Approx 50)

RESISTORS (MIXED WATTAGES)
MIXED VALUES £1.00

PLEASE ADD 12,5% VAT TO ALL
RESISTORS & CAPACITOR PACKS

HIGH QUALITY SPEAKERS, 8 1 /*" x 6”
elliptical, only 2" deep, inverse magnot,
4 ohms, rated up to 10 W, £ 1.50 each,
or 2 for £ 2.75 (qty. discount available
+ 12,5 VAT.

WELLER SOLDERING
IRONS

WELLERSOLDERING IRONS EXPERT

Built-in-spotlight illuminates work Pistol
grip with fingertip trigger. High efficiency
copper soldering tip.

EXPERT SOLDER GUN
£6.80 + VAT (54p)

EXPERT SOLDER GUN KIT
(SPARE BITS. CASE. ETC.)

£9.80 + VAT (78p)

SPARE BITS
PAIR, 26p + VAT (2p)

MARKSMAN SOLDERING IRON

Unbreakable heat-resistant handle. Stain-
less steel barrel. Special steel heating
elements with Mica insulation bodded in
ceramic.

SP15D 15W £2.52 + VAT (20p)

SP25D 25W £2.52 + VAT (20p)

SP25D 25W+ BITS etc,

KIT £3.12 + VAT (25p)

BENCH STAND with spring for
MARKSMAN IRONS £1.80 + VAT (14p)

Spare sponges, as for TC PI .

SPARE BITS

MT8 for 1 5W 42p + VAT (3p)

MT4 for 25W 35p + VAT (3p)

TC PI TEMPERATURE CONTROLLED
IRON

Most versatile soldering tool yet
designed. 48W pencil out-performs
uncontrolled irons several times its
weight and consumption. Temperature
controlled iron & PSU.

£18.43 + VAT (£1.47)

SPARE TIPS

Type CC SINGLE FLAT,

Type K DOUBLE FLAT FINE TIP.

90p each + VAT (8p)

ALL SPARES AVAILABLE.

MULTICORE SOLDER

Size 5 SAVBIT 18swg in alloy dispenser

32p + VAT (3p)

Size C1SAV18 SAVBIT 18 swg
56p + V AT (4p)

Size 12 SAVBIT 18swg on plastic reel
£1.80 * V AT (1 5p)

MINIATURE PLIERS

HIGH QUALITY "CRESCENT"

MADE IN USA
£4.35 + VAT (35p)

SIDE CUTTERS

HIGH QUALITY "CRESCENT"

MADE IN USA
£5.45 + VAT (44p)

SOLDER SUCKERS

(HIGH QUALITY, PLUNGER TYPE)

STANDARD £4.50 + VAT (36p)

WITH SKIRT £4.95 + VAT (40p)

Spare nozzles (PTFE)

60p each + VAT (5p)

RUBBER BULB TYPE

A handy inexpensive tool for the quick
removal of solder. Small, lightweight and
easy to use. Teflon tiplets easily changed
or replaced.

No. 881 Complete Tool.

£1.20 + VAT (lOp)

No. 8810 Nozzle only

50p + V AT (4p)

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UNITS from

★

★

★

★ TO DEF 5271-A

1 .0 — 60.0M H z
FAST DELIVERY
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Write for Leaflet AT-1

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Southampton S04 6ZY

(248)

sav i

mu saw it

in elektor and

don't

forget......

Printed circuit boards are available for many
projects published in Elektor. Refer to the
'eps print service' list in this issue and quote
ref. no. when ordering.

The Semicon
International e ~
Transistor Index

Easy alpha-numeric reference to the ratings and characteristics
of some 24,000 transistors of international origin. European,
U.S.A., Japanese. Essential guide for all Engineers, Technicians,
and Buyers. Over 450 pages of basic information. By far the
best manual of its kind available anywhere to-day.

* EXTENSIVE SUBSTITUTION GUIDE
* CV & BS DEVICES & EQUIVALENTS
* TERMINATION DRAWINGS

* ALTERNATIVE SOURCES OF SUPPLY

Remit with order C^Q Elsewhere £10.90

price. UK only. ■ WW Surface mailing.

Please send copies of the Semicon Transistor Index, 6th Ed. to:

Name

Address

□ / enclose cheque/postal orders for £

□ My Access/ Bard ay /In ter bank Card No. is

Refund if not satisfied and book is returned within 14 days.

Semicon Indexes Ltd. 2 Denmark St. Wokingham. Berks. RG1 1 2BB

TEL: WOKINGHAM (0734) 786161

608 — elektor june 1976

selektoi

rasnnrseueKTDrsei.1

Build a Digital Watch —
the easy way

For those who want to make a digital
watch but are deterred by the degree of
miniaturisation involved, a range of
preassembled watch modules is available
from Litronix. Prices have fallen so
rapidly in recent months that it is now
cheaper to buy one of these modules
than to purchase the individual
components for a watch, and it is only
necessary to fit the module into a case
and install batteries to obtain a fully-
working watch.

The timekeeping function is integrated
into a single ion-implanted CMOS chip
and the display drivers are contained in
two silicon bipolar IC’s. These, together
with the LED display, 32.768 kHz

crystal, capacitors and resistors, are
mounted on a ceramic substrate using
hybrid assembly techniques. This in
turn is mounted in a high impact
plastic frame to provide mechanical
protection for the module. Gold-plated
switch contacts are provided around the
periphery of the module to activate
the display and timesetting functions.
The module is powered by two RAY-
0-VAC RW44 silver oxide batteries (or
equivalent) and battery life is said to be
one year with up to twenty interrog-
ations per day.

The cheaper version of the watch
module, the LWM-653 1 , has an hours
and minutes display with a flashing
colon for seconds. One-off price is
around £ 1 5.

The more expensive version, the
LWM6560, retails for about £ 1 8 and
displays hours and minutes, seconds,
day-of-week and date. It also incor-
porates a light sensor to adjust the
display brightness to suit ambient
light and thus extend battery life.

Litronix House ,

593 Hitchin Road, Stopsley ,

Luton, Bedfordshire .

Vegetable Growing by Computer

Researches in Naaldwijk, Holland, wish
to know exactly how fast tomatoes
ripen and how well cucumbers, for
example, grow in greenhouse conditions.
Assistance of a computer has been
called on at the research and experimen-
tal institute for the cultivation of fruit
and vegetables. At the present time this
is the largest research project of its kind
in the world. A Siemens 330 process
computer monitors and controls the
environmental conditions in 24 growing
compartments within the large green-
house.

In addition to the central processing
unit with a main memory of 64 K words
( 1 6 bits each), the computer system
comprises a series of data input/output
devices. These include, process inter-
facing devices for connection to the
measuring and control systems of the
individual climatic chambers. The task
of this process periphery is to collect
800 analog and 80 digital signals, while
also handling 450 digital output signals.
Twenty-six analog signals are recorded
in each of the 24 climatic chambers
(each 56 m in area). These include
temperature values for the air and soil,
relative humidity, C0 2 concentration
of the air, temperature of the water in
the heating system, signals indicating
window positions and the various values
for the irrigation and drainage systems
and the heating system. Sixteen digital
outputs in each climatic chamber
control the motors of the valve drives
and window adjusters. In addition, the
weather station parameters can also be
included in the calculations and control
operations.

The signals issued from each sensor are
scanned once every minute. The process
computer calculates the manipulated
variables and the setpoints of the
secondary analog backup controllers
by direct digital control so that a
smooth changeover to analog control
is possible if required.

Every day an estimated one million

measured values, signals and commands
are exchanged between the process
computer and its peripherals. All
relevant data can be logged in tabular
form, using the typewriter. In addition,
the case history of 256 values over the
the previous 96 hours can be graphically
represented on the colour curve display
station.

The aim of the investigations in
Naaldwijk is not only to research the
optimum conditions for growing fruit
and vegetables but also to determine the
climatic conditions under which the
plants are least susceptible to diseases.

It should then be possible, to a certain
degree, to forego the use of chemical
agents and pesticides.

The investigations are at present con-
cerned with tomatoes and cucumbers.
The research program is later to be
extended to other types of vegetable,
e.g. red peppers, aubergines, beans and
lettuce. Fruit and flowers are also to
be investigated at a later date. At
present, tomatoes grown in Dutch
greenhouses have annual production
value of approximately £ 9.6 million.

Siemens AG

Zentralstelle fiir Information
Postfach 3240, D-8520 Erlangen 2
Federal Republic of Germany

'Noiseless' Discs and tapes

A new process which completely
eliminates surface and background noise
from disc recordings and captures for
the first time the full dynamic range of
the music is announced by dbx, Incor-
porated, manufacturer of noise re-
duction systems for the professional
studio and the audiophile.

The process permits commercial discs
as played in the home to equal the per-
formance quality of studio master
tapes. This is accomplished by elec-
tronically compressing the recorded

elektor

elektor june 1976 — 609

■JUST

afij MH

tHU p

HKfWSi Wilmk
*W$m pmb

ignal by a factor of 2: 1 at the time the
naster disc is cut, and expanding the
ignal by a complementary factor of
:2 at the point of playback. If a dbx
ncoded master tape is used, full
lynamic range and freedom from noise
vill be realized upon playback. Master
apes produced with other types of
loise reduction systems, or with no
loise at all, may be used and the played
)ack disc will sound equal to the
naster tape. Ordinary discs are limited
o a dynamic range of some 60 dB,
vhereas the dbx encoded disc has a
ange well in excess of 100 dB.
rhe dbx process compresses the
lynamic range of the music to a
dynamic range envelope’ which fits
:onveniently within the inherent
imitations of the record medium, then
expands the music to its full original
dynamics at the point of playback,
rhis compression and subsequent
expansion reduces record surface noise
md other unwanted background noise
to inaudibility, so that when the musical
program stops, no sound of any kind is
heard from the playback system.

Hie complete absence of background
noise also makes the quiet portions of
the music easier to hear, and the defi-
nition of individual voices and instru-
ments in ensemble music is dramatically
improved.

A significant advantage of the dbx disc
encoding process is that it does not
obsolete any existing manufacturing
technique or equipment presently in use
in the recording industry, nor does it
increase actual product cost in any way.
On the contrary, dbx encoding offers
numerous opportunities for reducing the
cost of recorded music without compro-
mising quality. For example, with dbx
encoding, record grooves may be placed
closer together, increasing the amount
of music on a record by up to 30%.
Electronic expansion circuitry, similar
in cost and complexity to Dolby B and
quad matrices, is required at the point
of playback to properly decode the dbx
compressed signal. The decoder cir-
cuitry is now available to audio equip-
ment manufacturers for inclusion in
consumer audio components and sys-
tems on a license basis. Also, many
audio component dealers are now selling
the 120 consumer series of compressor/
expander noise reduction systems which
have disc decoding circuitry built in.

The 1 20 series uses the same 2: 1 linear
decibel compression/expansion principle
used in dbx professional studio equip-
ment, but the sensing circuits have been
optimized to best complement the
bandwidth requirements of consumer
grade reel-to-reel, cassette and cartridge
tape recorders. The 120 series is not
compatible with dbx professional
format tape noise reduction systems

used in recording studios.

The new systems allow consumer grade
recorders with signal-to-noise ratios as
low as 45 to 50 dB to produce full
dynamic range tapes which are audibly
free from tape hiss and background
noise. In excess of 30 dB noise re-
duction can be realized with the 1 20
system, along with 10 dB headroom
improvement which reduces the likeli-
hood of tape saturation.

The 120 noise reduction format is also
used by record manufacturers for pro-
cessing of dbx encoded records, and a
120 family decoding device is required
for playing the dbx encoded discs.

Two models are initially available in the
120 family of noise reduction units.
Model 122 is a two-channel record or
playback unit. That is, it will either
record or playback, and is switched
from one function to the other.

Model 1 24 is a four-channel record or
playback unit suitable for the full range
of quadraphonic activities, and having
the added feature that when used in a
two-channel system it can record and
playback at the same time, permitting
the recordist to monitor the decoded or
normalized signal during recording.
Commercial record labels currently
releasing stereo discs in dbx encoded
format include Klavier and Creative
World, and negotiations are in progress
with a number of other lables to release
material in dbx encoded format.

Both Models 122 and 124 will decode
presently available dbx encoded stereo
discs, dbx disc encoding is equally
applicable to the production of
quadraphonic releases as well, regard-
less of whether they are produced in
discrete (4-4-4) or matrixed (4-2-4)
format.

dbx Incorporated ,

296 Newton Street ,

Waltham, Massachusetts 02154.

Ion beams etch chip
structures

New etching process for superfine
structures on semiconductor
chips.

Semiconductor chip structures have
become unbelievably small, and this
trend will continue. The wavelength of
the light beam, used to create com-
ponent contours on chips using the
photomasking processes, is nowadays
often not short enough. This is why
electron beams with their markedly
shorter wavelengths must be used.

Such beams are capable of producing
structure spacings of 1 and less.
However, it is then necessary to use a
different method to create the struc-
tures, which are defined by a photo-
mask. This is because the chemical

Comparison of chemical and ion beam etch-
ing. The chemically etched structures in the
left-hand photo are characterized by under-
cutting below the photo-mask and the curved
side walls. The ion-etched structures in the
right-hand photo are characterized by
smooth, straight side walls.

Siemens Photo

etching processes that are being used
now have an undercutting effect —
whereby the side walls of the structures
are washed away from underneath. This
just cannot be tolerated in the case of
superfine structures in the submi-
crometer range. A process is at the
present time being worked on at the
Siemens laboratories, this process uses
an ion beam, working mechanically
like a sand blasting jet. It cleanly
cuts out even the very finest chip
structures.

The fast argon ions required for this
job are produced in a plasma chamber,
then are directed onto the photo-
resisted silicon chips. The structures
are transferred practically without
change in dimensions independently of
the resist adhesion. The particular
advantage of this process is that the
side walls of the chip structures are
smooth in contrast to chemical etching,
and the angle of the side walls has a
uniform value of around 65 (see
photo).

Siemens AG

Zentralstelle fiir Information
Postfach 3240 , D-8520 Erlangen 2
West Germany

610 — elektor june 1976

channel quadruple

Dipl. Ing. H. Weidner

A single-beam oscilloscope is often
insufficient nowadays for testing
electronic circuits. This article
describes a multi-channel switch
with which four signals may be
displayed simultaneously.

Two-channel oscilloscopes are, by now,
commonplace, and various types of two-
channel switches are available for
extending single-beam oscilloscopes. By
somebody-or-others law, however, we
continue to build circuits which we are
incapable of testing, and even two-beam
displays are often insufficient. Bear in
mind that the available two-channel
switches are expensive, and we are left
with a demand for a simple and reliable
multi-channel switch within the pur-
chasing power of the amateur. The
requirements of such a switch are:

1. four channels;

2. unity gain and a facility for attenu-
ation;

3. Y-position separately adjustable for
each channel;

4. both chopped and alternating
switching modes;

5. facility for selecting each channel
separately.

This article describes a switch to meet
these requirements, with the design
being kept as simple as possible by
starting off with a suitable integrated
circuit.

A survey of ICs available on the marke
led to the selection of the HA240!
made by Harris. This consists of fou
operational amplifiers (opamps), onl\
one of which is activated at any ont
time depending on the information a
the two control inputs (pins 1 5 and 16)
The outputs of the four opamps art
internally connected to the commoi
output amplifier, so that the output o
the activated opamp is available at tht
common output point (pin 10). Other
wise, the IC behaves as expected for ai
opamp. The maximum output voltagt

hannel quadrupler

elektor june 1 976 —611

igure 1. Circuit diagram of the four-channel
witch.

igure 2A. Pin connection diagram for the
IA2405.

igure 2B. Pin connection diagram for the
M 318.

igure 3. Front view of the (German!) proto-
/pe.

ariation is ± 10 V, the gain and attenu-
tion being adjustable in the usual way
vith feedback resistors.

rhe circuit

; igure 1 gives the circuit diagram of the
witch. As can be seen, the four opamps
n IC1 provide the central part of the
ircuit, with their gain and attenuation
>eing controlled by the input resistors
11 . . . R4 and the feedback resistors
. . . R8. The gain of the first opamp
s controlled by the ratio of R1 : R5
similarly for the other opamps); the
naximum gain in this case being unity
0 dB), and the attenuation being con-
rolled by the variable resistors
15 . . . R8. Calibration of the attenu-
ition has not been included (since phase
omparisons are usually of more
nterest) but it would be fairly simple
o include calibration if required, either
)y fitting a calibration scale for the
'ariable resistors, or by replacing them
vith multi-position switches between
ixed resistors. The maximum input
voltage should not exceed ± 10 V, which
s sufficient for most applications,
ilthough the input voltage range could
tlways be extended by using voltage-
iivider probes with an attenuation of
10 : 1 .

Hie Y-position of the signals displayed
pn the screen is controlled by the
potentiometers R17 . . . R20 which
control the voltage to the non-inverting
nputs of the opamps. The values of the
esistors in series with these potentio-
neters have been chosen to give a full-
screen display on the oscilloscope with
he input sensitivity set to 1 V/cm.
Other values may be substituted if other
atios are required.

Since the IIA2405 performs an inversion
petween input and output, IC6 has been
ncluded to invert the signal again so
hat the correct polarity is obtained at
he output of the switch. Also included
lere is a feed-forward circuit R30, CIO,
which improves the slew rate.

VIoving on to channel selection, this is
ichieved by the switch S6, through
which digital information is supplied

2a

HAS4Q5

. 15

14

13

12

11

10

16

s

^2

3

4

5

6

7

8

7044- 2A

Top view 7044 • 2 B

T05 package

612 — elektor june 1976

channel quadrupler

measuring penc

to the two controlling inputs. S6 is a
five-position switch of which positions
1 . . . 4 are used to select opamps
(i.e. channels) 1 ... 4 respectively, by
providing the following binary signals
at the input pins:

pin 1 5 pin 1 6 selected

channel

0 0 1

0 1 2

1 0 3

1 1 4

Position 5 allows the outputs from the
dual flip-flop IC5 through to pins 1 5
and 16, so that all four channels are
displayed on the screen.

The requirement for alternative
switching modes is more difficult to
achieve although in theory both
chopped and alternating mode can be
provided, and indeed have been provided
in this particular circuit. Practical diffi-
culties may however intervene as
explained shortly.

The mode is selected by means of the

Figure 4. Display of a square wave using the
switch. Top: input signal. Bottom: output
signal. X-scale: 2 ps/division. Y-scale: top:
2 V/division; bottom: 0.2 V/division.

switch S5, which connects one of the
two control sections to IC5. In chopped
mode the switching voltage is generated
by IC2 and IC3 of which the latter
(timer 1C type 555) is connected as a
multivibrator producing a square wave
of 1 00 kHz. This signal drives the
monostable IC2, which converts it into
spikes whose negative edges trigger the
flip-flop 1C5; the frequency of the
switching signal is 50 kHz. The output
from IC3 also drives a further mono-
stable IC4, whose output is converted
by the circuit of T3, T4 into negative
pulses which suppress the beam during
switching. The ‘beam suppression’
signal should be connected to the
Z-input of the oscilloscope.

If the oscilloscope is not provided with
a Z-input the simplest solution is to
ignore beam suppression, in which case
IC4, T3, T4 can be omitted. The absence
of beam suppression is only noticeable
when the signal frequency and the
chopper frequency are similar. At this
point the only solution is to use alter-
nating mode in which one complete
signal or channel is ‘written’ on the
screen, then the next signal is ‘written’
etc. This mode can also be useful in its
own right (e.g. when amplitude compari-
sons are of more interest than phase
ones) not just when chopped mode fails.
The switching pulses required for alter-
nating mode come from the oscilloscope
itself at the end of each deflection
period. To make use of these pulses
the sawtooth voltage for the horizontal
deflection (if necessary via a square
wave voltage shaper) or the gate voltage
must be available. This is not true of
many single-beam oscilloscopes, so it is
recommended that such an output be
provided if working in alternating mode
is to be achieved. The gate signal or the
pulse derived from the sawtooth voltage
is amplified by the circuit of Tl, T2 to
provide a signal to IC5.

Technical data

Figure 4 shows a 100 kHz square wave
displayed on an oscilloscope using the
switch with the attenuation set to 10 : 1.
Note that as this setting, the slope of
the edge of the output signal is still
good, but when the ‘gain’ control is
increased to maximum (1:1) the band-
width of the unit is restricted to such
an extent that only sine waves up to
100 kHz can be satisfactorily displayed.
The input impedance of the switch is
less than 100 k, while the input
impedance of most oscilloscopes is 1 M.
When measuring with this switch, there-
fore, the extra loading on the measuring
point must be taken into account.

As far as power supplies are concerned,
three stabilised voltages are needed,
vis: ± 15 V for the opamps and beam
suppression, and +5 V for the ICs. The
current consumption of the circuit is
about 25 mA from each 15 V supply,
and 60 mA from the IC supply. To keep
the circuit as compact as possible, it is
recommended that integrated voltage
regulators be used. In the prototype,
L 1 29 and L 1 3 1 (SGS) were used. H

J. Hajek

measuring

pencil

Here is a device to help with that of
recurring requirement — an extra pai
of hands. This measuring pencil can b<
used as a probe for inspecting voltages
in addition to its conventional appli
cation of writing down the results.

The measuring pencil consists of j
propelling pencil made of a syntheth
resin. A flex is soldered to the push
button such that the propelling mechan
ism is unimpaired, and the other end o
the flex is provided with a plug to fi
the measuring instrument (e.g. a volt
meter). To use the pencil, connect tht
circuit to be tested to the earth termina
of the meter, and the pencil to the inpu
socket. Using the pencil as a probe, the
circuit voltages may now be measurec
at various points and the results writter
down with the same instrument.

The measuring pencil is particularly
suitable for circuits with low voltages
(< 42 V AC or < 60 V DC) as the insu-
lation of the pencil is not then a
problem. The contact resistance
between the measuring point and the
meter is less than 1 £2 in this design,
and when used with modern high
impedance equipment, the measuring
error is negligible. u

HF FM reception

elektor june 1976 — 613

ITHFFM

reception

)wners of FM tuners may often
/ish to know what sort of signal
jvel they can expect to receive in
he locality in which they live.

'he simplest and most accurate
nethod is to obtain a direct
eading using a field strength
neter, but of course very few
leople possess one of these
nstruments. The charts
iroduced by the BBC of the
ervice areas of their various
ransmitters provide a useful
wide, but it is often possible
vith a sensitive receiver and good
ierial to obtain a usable signal
lutside the service area. This
rticle investigates the rules
loverning VHF propagation and
hows how received signal
trengths may be estimated with
i few simple calculations.

: igure 1. The optical line of sight is approxi-
nately Dh = \/2R • h, + \/2R • h 2 . After
ntroducing the radius of the earth this
>ecomes Dh = 3570 • (y/hi + n/F^). h,, h 2
ind Dh are in m. The optical line of sight
days a part in the empirical formula for field
trength calculations.

: igure 2. Bending effects increase the recep-
ion range of radio waves to beyond the
>ptical line of sight. The range is then
Jh = 4120 • (Vh, +S/M.

: igure 3. As a result of reflections at the
roposphere, considerably greater distances
ire bridged. The intensity varies, however, as
i result of cosmic influences.

10000

1000

A

>

a.

0,001

1525 3

1000 km
500 miles

614 — elektor june 1976

VHF FM receptio

4

n

O

O

o

field strength
microvolts/meter

o

o

in

o

in

o

o

o

in

oo

o

o

oo

o

in

CM

o

o

CM

o

in

o

o

o

in

o

n

*7

I

in

CN

in

0 )

O

C

ro

CO

• MM

TJ

(D

0

o

o

o

o

o

o

o

c

o

o

o

o

o

o

o

o

o

o

o

in

o

•

o

•

o

in

•

o

in

CM

o

m

CM

»—

. .

o o
o m
m rM

o o in
o in cm

o

o

o

05

o

oo

o

CD

o

in

o

o

00

o

CM

microvolts/meter

ro

I

in

CN

in

gain in dB

HF FM reception

elektor june 1976 — 615

o

o

Lf)

o

LO

o

o

o

LO

CO

o

o

CO

o

LO

CN

o

o

CM

o

LO

O

O

o

LO

in

CN

in

E

0 )

o

c

03

4 -»

CO

•

T 3

Q)

o

o

o

CD

O

00

O

o

to

o

LO

o

o

CO

o

CM

o

o

Cl

■c

I

in

CN

m

616 — elektor june 1976

VHF FM receptic

Figure 4. The curves of figure 4A and 4B
(land) and 4E, 4F (sea) give the field strength
versus the distance for various heights of the
transmitting aerial. In this it is assumed that
the receiving aerial is at ground level (0 m).
The curves relate to a radiation power of
1 kW. The curves of figure 4C, 4D (land) and
4G, 4H (sea) give the gain which is achieved
for certain heights of the receiving aerial. The
curves give reliable results for the frequency
range of 70 MHz to 150 MHz.

Figure 5. The value of the exponent 'n' in
the empirical formula, as a function of fre-
quency.

In the early days of wireless it was be-
lieved that radio waves of short wave-
length (VHF) could only be transmitted
over line of sight distances. It was
thought that radio waves were rapidly
attenuated once the receiver was below
the optical horizon of the transmitter
(figure 1). This is now known not to be
the case. Due to differing electrical
properties of the layers of the atmos-
phere reflections and refractions of the
radio waves occur, so that the waves
follow a curved path.

Radio waves can thus be received at
reasonable signal strength even when the
receiving aerial is below the optical
horizon (figure 2). Figure 3 shows how
the field strength of radio waves re-
ceived by tropospheric reflection
(shown dotted) are considerably greater
than the field strengths of the ground
waves at the same distance from the
transmitter.

The factors that determine if a usable
signal can be received from a particular
transmitter may be tabulated as follows:

1. transmitter output power (it is as-
sumed that transmitters radiate omni-
directionally);

2. the distance between the transmitter
and the receiver aerials;

3. the height of the transmitting and re-
ceiving aerials (obviously if the aerials
are higher the transmitter and receiver
can be further apart before the receiver
falls below the ‘radio horizon’);

4. the gain of the receiving aerial (rela-
tive to a simple dipole);

5. the minimum signal strength required
by the receiver to produce a reasonably
noise-free signal.

Using a folded dipole aerial at 100 MHz
the signal produced by the dipole is ap-
proximately numerically the same as the
field strength i.e. a dipole in a field
strength of 1 fiW/m will produce a signal
of 1 juV. The signal produced by other
types of aerial can be obtained by multi-
plying by the aerial gain (or adding the
gain in dB).

The curves of figure 4 may be used to
establish the field strength that can be
expected at a given distance from a
transmitter. These curves are based on
a transmitter power of 1 kW, but the
field strengths with other transmitters
can easily be found. This is best illus-
trated by means of some examples.
Example 1. The distance between the
transmitting and receiving aerials is
200 km* on land, the transmitter
power is 100 kW, the transmitter
aerial height is 500 m*, and a folded
dipole at a height of 15 m is used for
the receiving aerial. What is the voltage
expected at the tuner input?

From figure 4B it can be seen that the
expected field strength 200 km from a
1 kW transmitter with a 500 m high
aerial is around 0.1 /iV/m. However,
the transmitter power is actually
100 kW so the field strength is increased

by 10 log ^-^(power ratio!) or 20 dB.

Furthermore, the receiving aerial height
is 15 m, and from figure 4C this gives a
further increase of 20 dB.

* 1 kilometer (km) = 0.62 miles;

1 meter (metre, m) = 39.37 inches.

The expected field strength is thu
40 dB up on 0.1 fiV/m or 100 time
(voltage ratio!) i.e. 10 /iV/m. Since th
aerial is a simple dipole the signal inpu
to the tuner (assuming negligible losse
in the aerial downlead) is 10 /zV, whicl
is adequate for most tuners.

Example 2. The distance between th
transmitter and receiver is 175 km am
the path is across the sea. The trans
mitter power is 100 W and the aeria
height is 500 m. The receiving aerial i
a 4 element Yagi array with a gain o
10 dB mounted at a height of 10 m.
From figure 4F it is apparent that th
received field from a 1 kW transmitte
would be 1 /zV/m. However the trans
mitter is only 100 W, so the fieh

strength is reduced by —10 log

- 10 dB.

From figure 4G the aerial height o
10 m provides no additional increaS'
(0 dB), so the output voltage from
folded dipole would be 10 dB down oi
1 fjiV. However, the aerial provides ;
gain of +10 dB, which cancels out thi
10 dB loss due to the reduced trans
mitter power. The voltage at the inpu
to the tuner is thus 1 /zV.

Example 3. This may be useful fo
would-be spies . . . The distance be
tween transmitter and receiver i
150 km, the height of the transmittinj
aerial is 50 meters, and the power i
100 watts.

What type of receiving aerial must b<
used to deliver at least 0.5 to the re
ceiver?

Figure 4B shows that the basic fielc
strength from a 50 meter transmittinj

VHF FM reception

elektor june 1976 — 617

aerial at 150 km is 0.01 juV/ meter.
Since a voltage of at least 0.5 fiW is
required at the receiver input, the basic
gain requirement is equal to

2° log ■ 34 IB.

However, that’s for a 1 kW transmitter
but the power in this case is only 1 00 W.
Therefore the field strength is reduced

by a further 10 log — 10 dB.

Therefore, the receiving aerial will have
to give a total gain of 44 dB (10 dB for
the low transmitting power and 34 dB
for distance). One possible way to
achieve the 44 dB gain figure is to
attach a folded dipole to a balloon
floating at 250 meters. A more prac-
tical (?) solution is a 6-element yagi
array with a gain of 14 dB mounted at
50 meters.

Example 4. This is of a more practical
nature, and can be modified for indi-
vidual circumstances. A 4-element aerial
with a gain of 10 dB is mounted at a
height of 20 meters, what receiving
range can be expected for reasonably
noise free FM stereo broadcasts?

First, some assumptions must be made:
most FM transmitters have power out-
puts of 100 kW or more with aerial
heights of over 200 meters; most re-
ceivers need approximately 100 juV for
noise-free stereo reception.

Adding the basic receiving aerial gain
(10 dB) to the gain due to receiving
aerial height as derived from figure 4C
(22 dB), a total aerial gain of 32 dB is
found. Since the receiver requires
100 /iV, the 32 dB aerial gain means
that a field strength of 2.5 £/V/m is re-
quired at the aerial. If the transmitter
power was 1 kW a look at figure 4B
would show the distance.

However, the transmitter power is
100 kW. This means that the field
strength at the receiving aerial is in-

creased by 10 log

100

1

= 20 dB for

any given distance. 20 dB in field
strength is a factor 10, so if a 100 kW
transmitter gives the required 2.5 yu V/ m
at a certain distance, a 1 kW transmitter
would give a field strength of

y~= 0.25 juV/m at the same distance.

According to figure 4B, if the trans-
mitting aerial height is 200 meters a
1 kW transmitter will give a field
strength of 0.25 yuV/m (so the 100 kW
transmitter will give 2.5 juV/m) at a
distance of 1 50 km.

Or, looking at it the other way round,
using the 4-element aerial at 20 meters
height with an ordinary receiver it
should be possible to get good (stereo)
reception from any transmitter within a
range of 1 50 km over land.

Of course, the results obtained from the
graphs of figure 4 are true only where
the transmission path is over the sea or
over relatively flat terrain. If the re-
ceiving aerial is on top of a hill then the
received field strength will be greater
since the effective height of tile aerial is
greater. Conversely, if the receiving

aerial is in a valley the field strength will
be less since the effective height of the
aerial is smaller and the aerial will be
screened by the walls of the valley.
Instead of using graphs, the received
field strength may be calculated empiri-
cally from the equation given below,
which takes account of the terrain by
including a term for the distance to the
optical horizon (obviously the distance
to the optical horizon is greater for an
aerial on flat terrain than for one
mounted at the bottom of a valley).

The equation is as follows:

E _ 88 • VP • h, • h 2 • Dh' 2
b XDn

Where E is the r.m.s. value of the field
strength in volts per metre;

P is the effective radiated power in
watts;

hi is the height of the receiving aerial in
metres;

h 2 is the height of the transmitting
aerial in metres;

Dh is the distance of the optical horizon
in metres (figure 1 );

X is the wavelength in metres;

D is the distance between transmitter
and receiver in metres;
n is a frequency dependent exponent
(see figure 5).

Both the curves of figure 4 and the
empirical equation apply only for nor-
mal atmospheric conditions. During
unusual weather conditions (such as
inversion layers) VHF reception at
distances of several thousand kilometres
have been observed. This, of course,
is not the norm, and is really of interest
only to those interested in DX activities.

M

triac control

In simple triac phase angle control the
trigger circuit contains only R4, PI, Cl
and the diac. Cl cannot fully discharge
in that circuit, so on later half-waves
the triac fires sooner. This gives a
‘snap-on’ effect called hysteresis.

Adding resistor R2 and R3 and diodes
D1 . . . D4 leads to equal starting con-

ditions for every trigger-cycle. In this
way, hysteresis effects are avoided.

Triac control units are notorious for
causing interference on radio and TV.
The easiest way to eliminate this is to
add the LC low-pass filter consisting of
LI, C2, C3 and Rl. Coil LI should be
placed in the neutral line. M

BTW

10-400

618 — elektor june 1976

A.M. mains intercom

Mains intercoms of a more or less
reasonable quality are still a bit
expensive on the market.
Consequently, there appears to be
a fair demand for a super simple
and cheap a.m. intercom which
despite a modest performance will
be useful in certain applications
where mains interference is not
excessive.

The type of mains intercom we are dis-
cussing here has already become popular
as a babyphone. The house mains wiring
is used not only to power the two posts
of the intercom, but also as the signal
connection. Each post is therefore
plugged in and the exasperating task of
laying out and rolling up lines is elim-
inated. Intercoms using the mains as
their signal connection are, however,
susceptible to mains-born interference.
The unit described here uses amplitude
modulation (a.m.), as do most of the
commercially available units. This gives
a reasonable compromise between sim-
plicity and performance. It is worth
noting here that a more complex
design using frequency modulation
(f.m.) to obtain high quality results

will be published in a future issue of
Elektor.

Arrangement

Every intercom post consists of a
transmitter and a receiver. Figure 1
shows the block diagram of one such
post. In the position ‘speak’ (or ‘trans-
mit’) a simple oscillator produces a
carrier which is amplified by an output
stage. The resulting signal is amplitude
modulated by the amplified microphone
signal. The high frequency signal is then
fed into the mains via a special trans-
former. In the position ‘listen’ (or
‘receive’) the high frequency signal
transmitted from another post is picked
up from the same transformer (at
point A) and fed to a high frequency
preamplifier. From there it goes to a
modest low frequency amplifier where
it is brought to a level sufficient to drive
a small loudspeaker.

Switching between ‘speak’ and ‘listen’ is
achieved by switching the supply volt-
age between transmitter and receiver.

Transmitter

The transmitter for the intercom is
shown in figure 2. The oscillator is a
simple multivibrator built around T3
and T4. The output from the oscillator
is fed to a class C output amplifier T6,

via a buffer stage T5. The collector volt-
age of this output stage is controlled by
the amplifier T2/T7 which is adjusted to
its maximum. This amplifier is in turn
driven by the microphone amplifier Tl,
whose gain may be varied by the poten-
tiometer PI in order to vary the modu-
lation depth. The final result is that an
amplitude modulated high frequency
signal is fed into the mains via trans-
former Trl. Diodes D1 . . . D4 protect
the output stage against voltage peaks
at switch on. Capacitors C9 and CIO
isolate the circuit from the mains.

Receiver

The receiver, which is very simple in
design, is shown in figure 3. The trans-
mitted signal is picked up at point A in
the transmitter circuit and fed to the re-
ceiver. The received signal is amplified
considerably by the circuit around T8
and T9, and then detection takes place
in the simple demodulator D7, D8, Cl 5.
The automatic gain control (a.g.c.) cir-
cuit formed by R18, D5, D6 is designed
to operate only on very high input levels
so protecting the listener from high level
mains-born interference.

The low frequency amplifier is simple
but adequate. The output power is
about 250 mW, which is sufficient for
good intelligibility. The volume may be

4.M. mains intercom

elektor june 1976 — 619

930 1-2

12V

2b0mA

B = B40C400

Figure 1. Block diagram of one post of the
mains intercom. Each post is a combination
of an a.m. transmitter and a conventional
'direct' receiver.

Figure 2. Circuit diagram of the a.m. trans-
mitter. Either high or low impedance micro-
phones may be used.

Figure 3. Circuit diagram of the receiver and
the l.f. amplifier.

Figure 4. A suitable power supply for the
intercom. SI switches between transmitter
and receiver.

controlled by P3.

It is advisable to set P2 as low as practi-
cable (i.e. so that the modulation is at
the audible threshold) as a considerable
number of components will then remain
below the detection level hence limiting
the interference on reception as much as
possible.

Conclusion

The simplicity of this design gives more
than a hint of the quality if its perform-
ance. Since the transmitting power is
fairly low (about 1 W) and interference
suppression cannot reasonably be com-
pared with that obtained with a narrow-
band f.m. system, good performance
can only be expected in a conventional
one-family house. For a number of

applications, this will be sufficient.
Thanks to the low transmitting power
though, the current consumption is very
low, and a simple supply will do,
figure 4 shows the circuit diagram of a
suitable supply using an IC LI 30. The
switch SI changes the supply between
transmitting and receiving circuits.

The circuit is not very critical and can
therefore be built without too much
difficulty. The only obstacle may be the
transformer which must be wound. For
the prototype, a potcore AL250 with a
diameter of 18 mm was used. Various
manufacturers (e.g. Siemens, ITT and
Philips) supply these potcores in a range
of versions and sizes. u

620 — elektor june 1976

FET front

Specification

Usable Frequency Range: 20 kHz-45 MHz
Sensitivity: 4 mV r.m.s. at 20 MHz

Input Impedance: 1 M in parallel with 5 pF
Rise Time: approx. 5 ns

Trigger Level: adjustable

HF preamp and FET probe
for frequency counter

The frequency counter design
published in the November 1975
issue of Elektor was accompanied
by a design for an input
preamplifier (Elektor 8,

December 1975 p. 1235). Whilst
this design gave good performance
from 0-20 MHz it was decided
that for r.f. work a preamp with a
higher sensitivity would be
useful, since it is here that signal
levels are smallest.

To avoid problems due to input
cable capacitance the preamp is
equipped with a FET input probe.

To be of any practical use in the ma-
jority of applications a frequency coun-
ter must have a high input sensitivity
and high input impedance. The fre-
quency counter described in Elektor 7
has, in its basic form, the input connec-
ted direct to the TTL logic circuitry,
whose input impedance is low and
asymmetric. In addition the input volt-
age swing required to trigger the logic
circuitry is of the order of 2 V. This is
clearly not of much use except for per-
forming measurements on other logic
circuits.

The preamp described in Elektor 8 had
an input impedance of 1 M in parallel
with a few picofarads and an input
sensitivity of around 40 mV, rising to
100 mV at 20 MHz. It was felt that for
r.f. use a higher input sensitivity was
desirable, and it was decided that by
sacrificing the low-frequency response
(for reasons explained later) a high gain

could be obtained with a simplified
circuit.

With the original design the preamp was
mounted in the frequency counter case.
However with this design there was a
problem: reactive loading of the signal
source by the capacitance of the input
cable, which can be over 100 pF/m for
coaxial cables. For this reason it was
decided to split the new preamp design
into two sections, a FET probe with a
high input impedance and low output
impedance capable of driving a coaxial
cable, and a preamp, mounted in the
case with the counter, to provide most
of the gain.

Design Targets

The performance requirements for the
preamp are similar to those given for
the earlier design, except that higher
input sensitivity is aimed at, while the
low-frequency response is unimportant,

© = 1,4 v

Parts List to Figure 1

Resistors

R 1 = 4k7
R2 = 1 k
R3 = 2k7
R4 = 1 k8
R5 = 100 n
R6,R9 = 220 n
R7 = 68 n
R8 =47 n
R10 = 1 k5
R 1 1 ,R 1 3 = 470 n
R 1 2 = 10 k
PI = 1 k

Capacitors

Cl = 100 n
C2 = 470 n
C3,C5,C6,C1 1 = 10 n
C4 = 47 m/6 V
C7,C10 = 15 m/ 3 V
C8 = 220 p
C9 = 100 p

Semiconductors

T 1 ,T3 = BF494.BF1 94.BF1 95
T2 = BC557.BC1 57

FET front

elektor june 1976 — 621

since the circuit is specifically intended
for r.f. work. The requirements are
tabulated below.

1. Bandwith. It was decided that the
usable frequency range of the preamp
should extend from the top end of the
audio band to above the upper fre-
quency limit of the counter ( 1 8 MHz).

2. Input sensitivity. It was decided that
10 mV was a useful value and could be
obtained without resorting to complex
circuitry.

3. Input impedance. This should be as
high as possible i.e. input resistance
should be high and input capacitance
low.

These design requirements are met, and
in some cases exceeded, by the new
design. The usable frequency range of
the preamp + probe extends from below
20 kHz* to above 45 MHz. At 20 MHz
the input sensitivity is around 4 mV,
whilst at 45 MHz it is still only 17 mV,
which is better than the l.f. sensitivity
of the original design. These figures
refer to the r.m.s. input voltage necess-
ary to cause an output voltage swing
that will reliably trigger the TTL
Schmitt input of the frequency counter.
The impedance of the probe input is
1 M in parallel with 5 pF.

Preamp Circuit

The preamp circuit is shown in figure 1
and consists of a simple, three-stage,
direct coupled amplifier. To minimise
the effect of transistor capacitances and
stray circuit capacitance the resistor
values around the circuit are kept low.
As a consequence of this the low-
frequency response is sacrificed, since to
extend the l.f. response down into the

* Frequencies below 20 kHz can be
measured , provided the rise time is suf-
ficiently short - less than 10 ps.

audio band excessively large value
electrolytics would have been required
for C2 and C7 (especially C7). Quite
apart from the size consideration the
parasitic inductances of such large
electrolytic capacitors can cause un-
desirable resonances at higher fre-
quencies.

The preamp is provided with two in-
puts, an a.c. input, which is normally
fed from the probe output, and a d.c.
input intended principally for low-
frequency measurements on logic cir-
cuits. At low frequencies the d.c. input
sensitivity is compatible with TTL
logic levels. The a.c. trigger level control
PI sets the d.c. operating point of T3
and hence determines the input level at
which it will turn on. With this control
it is possible, when measuring complex
waveforms, to trigger the frequency
counter from either the fundamental
or one of the harmonics as required.
Figure 3 shows the effect of varying the
trigger level control. The upper trace of
each oscillograph is an 18 MHz input
signal with a high 3rd harmonic content.
The lower trace in each case is the out-
put of the preamp, with different set-
tings of the trigger level control.

The graph of input sensitivity versus fre-
quency for the preamp is given in fig-
ure 2. This shows the input voltage
(r.m.s. mV) required for a 4 V peak-to-
peak output swing. As can be seen from

Figure 1. Circuit diagram of the preamplifier.
PI adjusts the triggering level.

Figure 2. Graph showing the preamplifier
sensitivity as a fuction of the input signal fre-
quency.

Figures 3a, b, c. Oscilloscope shows the effect
of trigger level adjustment by control PI (see
text).

622 — elektor june 1976

FET front

LI

®= 1 V D1 =D2= 1 N4148

(§)= 3 V * see text

©=4,2V

Parts List

Resistors

R1 = 1 k
R2 = 1 M
R3,R7 = 180 n
R4 = 2k2
R5 = 3k3
R6 = 68 H
R8 = 18 ft

Capacitors
Cl = 3n3
C2 = 10 m/ 6 V
C3,C5 = 1 n
C4 = 220 m/ 4 V
C6 = 100 n
C7 = 150 p

Semiconductors

D1,D2 = 1N4148

T1 = E300,BF245C

T2 = BF494,BF194,BF195

Inductors

LI = choke 100 mH

the graph the required input voltage
rises sharply above about 30 MHz, until
at 45 MHz it is about 22 mV. Even so
this is better than the original preamp
design and is further improved by the
addition of the probe, which also pro-
vides some gain.

Probe Circuit

To reduce the cost and simplify the
circuit it was decided to use a single
FET as the input stage instead of the
dual FET used in the original circuit.
T 1 operates as a source follower to
provide a high input impedance, with
T2 providing a gain of about 2 and an
output impedance of 68 £2 to drive
the coaxial cable. Diodes D1 and D2
clamp the input voltage to ± 0.6 V
maximum to protect the FET. The
equalization network in the emitter
of T2 helps to maintain a relatively
flat frequency response, though of
course a ‘ruler-flat’ response is not
important in this application, provided
the input sensitivity is adequate over
the required frequency range.

The FET used in this circuit is the
tried and trusted Siliconix E300. Other
FET’s, such as the 2N5397, 2N5398,
BF245C and BF256C may also be
suitable. If an alternative FET is used it
should be selected for a zero gate volt-
age drain current of at least 10 mA. R3
should then be selected to give a drain
current of 3 to 5 mA with the device
in the circuit.

Frequency Response

The gain of the probe circuit versus fre-
quency is shown in figure 5 with the
probe fed from a 50 £2 source. At the
low frequency end the gain is about
2, and the response exhibits a slight rise
up to about 60 MHz, after which it
falls off. If the probe is fed from a high
source impedance then the shunt capaci-
tance of the probe impedance quickly
attenuates the signal at higher fre-
quencies. This is shown in the dashed
curve for a source impedance of 10 k.
When the probe is combined with the
preamp the overall frequency response
is as shown in figure 8. At 1 MHz the

FET front

elektor june 1976 — 623

Figure 4. Circuit diagram of AC FET probe.

Figure 5. Fet probe gain as a function of fre-
quency. The probe is terminated into 50 £7.
Spectrum analyzer display shows frequencies
from 100 kHz to 50 MHz (left to right). The
input signal to the probe was 0 dB. The gain
of the probe by itself isn't of much import-
ance, because its main job is as an impedance
match.

Figure 6. Preamplifier p.c. board and com-
ponent layout (EPS 9413).

Figure 7. FET probe p.c. board and com-
ponent layout (EPS 9427).

Figure 8. Probe-plus-preamplifier sensitivity as
a function of the input signal frequency.

input sensitivity is around 2 mV, while
at 45 MHz it is still only 17 mV, which
is sufficient for many applications.
Figure 9 shows an oscillograph of the
preamp output to the probe at 40 MHz.

The upper trace is the 40 MHz input
signal (scale 20 mV/cm) whilst the
lower trace is the preamp output (scale
1 V/cm). The timebase speed is 20 ns/
cm.

Construction

A p.c. board and component layout for
the preamp is given in figure 6, and for
the probe in figure 7. Normal r.f. prac-
tice should be followed when mounting
the components on the boards i.e. the
component leads should be kept as
short as possible, especially the transis-
tor leads.

The preamp may be mounted in the fre-
quency counter case, and is connected
to the FET probe by a length of 50-
75 £2 coaxial cable. The supply lead to
the probe can be run alongside the
cable. The housing for the probe is a
matter of individual taste. The board
is sufficiently small to fit in a small
box folded from sheet aluminium. A
test prod made from brass rod may be
connected to the probe input through
an insulating bush in the end of the
box so that the probe may be used as
a hand-held unit.

The ground connection to the probe
input may be made with a crocodile
clip on a flying lead. Alternatively
the probe input connections may be
made using 4 mm sockets, as shown
in figure 11. Short Hying leads ter-

624 — elektor june 1976

FET front

missing link

Figure 9. Probe-plus-preamplifier response at
an input signal frequency of 40 MHz (see
text).

Figure 10. Excessive DC input signal levels
should be cut down to approximately 0.5 V,
since the maximum frequency limit is con-
siderably lower for large signals than for small
signal levels.

Figure 11. The completed FET probe.

minuting in test prods or crocodile
clips may be then be plugged into these
and connected to the circuit under test
so that the user’s hands are left free.
The unit could also be used with a prod
made from 4 mm brass rod which
would plug into the signal input socket.

Power Supply

Both the preamp and the FET probe
can derive their supply from the +5 V
rail in the frequency counter. The —5 V
supply which was necessary with the
original preamp design is not required.
The total current consumption is
around 25 mA.

Operation

In use the probe/preamp combination
requires no adjustments except for the
trigger level control and should function
as soon as power is applied. In the event
of a malfunction test point voltages are
provided in figures 1 and 4 as an aid
when faultfinding.

THE
SHIE

Bli.ll

Cumulative index of 'Missing Links'.

The Link will appear each year in the
June issue of Elektor. It contains an
index to all Missing Links concerning
articles published in the previous year.
The intent of the link is to assist the
home constructor by listing corrections
and improvements to Elektor circuits in
one easy to find place. A simple check
of the Link will show whether any
problems were associated with a project.

Tunable Aerial Amplifier (El);

February 75, page 229.

Steam Whistle (El ),

April 75 (E3), page 458.

TV Sound (E2);

June 75 (E4), page 660.

CA 3090 AQ Stereo Decoder (E5);

February 76 (E10), page 230.

BC5 1 6/BC5 1 7 Transistor problems;

March 76 (El 1 ), page 354.

Diagram for the CA 3080, page 755 of
E5, is incorrect; see September 75,
page 952.

TV Tennis (E7);

January 76 (E9), page 148;

May 76 (E13, page 508.

Also for good ideas see

March 76 (E 1 1 ), page 3 1 8.

Lie Detector (E7);

April 76 (El 2), page 454.

TCA 730/740 (E8);

January 76 (E9), page 148.

Pre-amp for counter (E8);

April 76 (El 2), page 454.

Missing Links concerning articles in
volume 2:

Feedback PLL for FM (E9);

February 76 (E10), page 230.
Capacity Relay (E9);

February 76 (E10), page 230.

Digital Master Oscillator (E10);

April 76 (El 2), page 454.

Morse Typewriter (El 0);

May 76 (E13),page 508.

ejektor

elektor june 1976 — 625

These pages offer our design staff — and,
we hope, our readers! — a long wished
for opportunity to eject more-or-less
wild ideas.

It often happens that promising ideas
cannot be converted into practical cir-
cuits. The problem may be lack of
specialised knowledge, lack of equip-
ment or even simply lack of time.

Several examples of this kind of thing
are still floating around the Elektor
laboratories, such as a spot-sinewave
generator and an OTA-gyrator. For the
time being, development of these pro-
jects was stopped after unexpected
technical problems arose. We simply
cannot afford to spend any more
development time on these projects at
the moment.

Sometimes projects are put on ice at
an even earlier stage, especially when it
is obvious from the start that develop-
ment will cost a disproportionate
amount of lab time. In this case the
design may never get past the block
diagram stage, or it may be de-
veloped bit by bit in the course of
(several) years. An example of this type
of thing is the one-line intercom. That
basic idea dates back to 1971, but it is
only now nearing completion. It is
rather frustrating to see a recent Philips
Press release describing a very similar
arrangement developed at their research
laboratories

This means that our design staff are
regularly coming up with interesting
ideas that are only published several
years later, if at all. Our readers also
regularly submit circuits that contain an
interesting idea, but are not (quite) suit-
able for publication because of technical
imperfections. Usually our editorial
staff can add the final touches, but this,
too, costs development time and man-
power — which is not always available.
Somehow, we want to eject these ideas.
Somebody may be able to use them or
carry on where the designer stuck.

From now on, interesting ideas which
can not (yet) be implemented in practi-

cal circuits may be published in
‘Ejektor’. It is not the intention to use
these pages for publishing ‘dud’ circuits;
on the contrary, the intention is to
publish interesting ideas. This may, of
course, include circuits that look as if
they should work but don’t. Also, some
of the ideas may well prove completely
impracticable on fundamental theoreti-
cal grounds. If so, we hope that the
reader who discovers this will let us
know . . .

Our editorial and design staff are quite
enthousiastic about the new oppor-
tunities offered. It should also be quite
a challenge to our readers.

We hope to be able at a later date to
publish practical circuits based on the
ideas presented here, after our readers
or our design staff have found time to
investigate them further.

OTA gy rotor

Comparison of the basic gyrator
formulae with the basic OTA formulae
shows that the OTA should be an ideal
active device in gyrator circuits.

Using an OTA gyrator it should be
possible to construct a filter that can be
swept through the whole audio band ,
while maintaining either constant
bandwidth or constant Q. Such a filter
could be used for spectrum analysis ,
electronic music (synthesiser!),
equaliser, LF PLL, etc.

The basic principles of the gyrator were
discussed in a previous article (‘How to
gyrate — and why’, Elektor 2, p. 255).
It was shown that when a gyrator is
used to simulate a parallel LC tuned
circuit (figure 1), the following formulae
apply:

Q = VSgR,

where: f Q = resonance frequency;

g = gi = g 2 = gyration constant;

Q = quality factor;

C = Ci = C2 ;

R= Ri = R 2 .

Note that both resonance frequency and
quality factor are linear functions of the
gyration constant (g).

The gyration constant is equal to the
absolute value of the slope (or trans-

9051 — 3C

102E-1

626 — elektor june 1976

ejektor

conductance) of the two amplifiers used
in the gyrator, so for each amplifier:

•out = ± g-Vin

(the + sign for the non-inverting ampli-
fier, the — sign for the inverting ampli-
fier).

Compare this with the basic OTA
formula:

•out = ± Sm- V in-

The similarity is obvious!

A bias current sets the value of g m . For
a CA 3080, say, the transconductance
equals:

gm = 19.2 x IabC-

This means that if OTAs are used in a
gyrator circuit, the gyration constant is
a linear function of the bias current
OABC)-

From this it follows that the resonance
frequency must also be a linear function
of the bias current. The quality factor
will also be proportional to the bias
current, provided the input impedance
of the OTAs is large compared to R.
If, however, the OTA input impedance
determines the value of R, the quality
factor will be almost constant over the
whole band.

This means that a simple DC adjust-
ment will suffice to sweep such a filter
over a 1000 : 1 frequency range
(0.1 pA < I ABC ^ 1 00 At A), while main-
taining either constant bandwidth or
constant Q!

A possible circuit is shown in figure 2.
The only thing wrong with it is that it
doesn't work properly . . . Provided the
input signal level was kept very low, the
filter worked as expected. At slightly
higher signal levels, however, a sort of
‘lock-on’ effect occurred: the output
level suddenly jumped to a much higher
value, and maintained this higher value
over quite a broad frequency range.
Outside that range it would suddenly
drop back again to the original low
level.

Literature: 4 How to gyrate - and why’:
Elektor 2, p. 255; ‘ OTA V Elektor 6,
p. 927.

one octave lower

Musicians nowadays tend to use more
and more bass guitars, bass clarinets,
and the like - as far as possible, that is.
For this reason, they are faced with the
problem of having to buy and carry
around more and more (expensive)
instruments.

Electronic circuits that would transpose
the sound of particular instruments
down over one or two octaves would
be a welcome relief.

A = Compressor
B = filter

C = expander

E103

Several factors determine the ‘sound’ of
a particular instrument: wave shape,
attack, decay, non-harmonic sounds
(e.g. wind noises), changes of harmonic
content as a function of amplitude, etc.
For this reason it is not normally
possible to retain the same ‘sound’
when the original signal is passed
through a simple divide-by-two stage
to transpose it over one octave.

There arc, however, several possible
approaches to the problem; the best
approach for one instrument may be
of no use for any other instrument.
A few ideas will be given here — further
development is left to electronic
musicians or musical electronics engin-
eers

Guitar. It has been found that a simple
divide-by-two circuit followed by suit-
able filters can give quite reasonable
results for a guitar. However, during the
decay time the system tends to ‘stutter’
as the input signal drops below the
trigger level of the divider, so this basic
system is musically useless. It will there-
fore be necessary to add a compressor
stage in front of the divider to keep the
input to this at a relatively constant
level; an expander before or after the
filters can restore the original amplitude
relationships.

A block diagram of this arrangement is
shown in figure 1 .

Trombone. Several brass instruments
(and several string instruments as well!)
have a spectrum consisting of both even
and uneven harmonics with a gradually
decreasing relative amplitude. To trans-
pose an instrument of this type over one

octave, it should be sufficient to add
one ‘sub-harmonic’ to the original signal.
This must be done in such a way that
the original fundamental becomes the
second harmonic of the new, added,
fundamental — with the correct ampli-
tude relationship.

An advantage of this system (sketched
in figure 2) is that the original ‘sound’
is retained to a very large extent.

Clarinet. Several woodwinds, including
the clarinet, have a spectrum consisting
mainly of uneven harmonics with
gradually decreasing relative amplitude.
The even harmonics are at a much
lower, and fairly constant, level of
approximately —20 dB.

To transpose the sound of this type of
instrument it should be possible to use
the same basic system as that described
for the trombone. The difference is that
in this case the new ‘sub-harmonic’
fundamental must be one-third of the
frequency of the original fundamental.
This means that a divide-by-three stage
will have to be used, and that the
instrument will be transposed over one
octave plus one quint .... this could
be a nuisance!

ejektor

elektor june 1976 — 627

R 1

filter without
phase-shift

A problem that occurs regularly in
control systems using negative feedback
is instability at high frequencies. If the
system contains a non-minimum phase
element , say, the total phase shift at
high frequencies can beco??ie 360 ° while
the total gain around the loop is still
more than unity.

If a low-pass filter is added inside the
loop to reduce the gain to a safe level at
high frequencies , the law of
conservation of misery dictates that the
point where the phase shift is 360 will
also move down to a lower frequency -
where the gain is still more than unity ,
in spite of the additional filter!

What is needed is obviously either a
completely new design , or else a filter
that does not introduce phase shift in
the frequency band that matters.

The basic principle of a filter of this
kind was published in an earlier issue of
Elektor: the ‘Frequency dependent
resistor' (Elektor 5).

The circuit is repeated here (figure 1 ).
It should be made clear that this is only
a basic block diagram; it is also assumed
for the present that the amplifiers have
infinite gain and zero phase shift.

In this case the total transfer function is:

’- 2 .( 4 - ) !

Vi JC or

in which

T = R 2 X C

The input current is therefore:

_ v i ~ v o v i — 2v i _
h * r

R

i

R

_v 0 _

R i Ri co 2 t 2

x v;

which means that the input impedance
is:

z; = - 1 = Ric
« •

2„2

This is a real resistance — with current
and voltage in phase — but increasing
with the square of the frequency.

If the output is left open, this frequency
dependent input resistance can be used
to construct a filter without phase
shift — the limitation being the fre-
quency where the amplifiers start to
introduce phase shift. It’s a fundamental
law that there must be phase shift some-
where!

To give an example, if a signal is fed in
via a resistor and the output is taken
from the input of the frequency depen-
dent resistor, the result is a high-pass
filter without phase shift at the roll-off
point.

Literature: Elektor 5, p. 712.

COMING SOON

The next Elektor is the July/ August
‘Summer Circuits’ issue. It contains over
100 projects and design ideas, from con-
trol units for solar heating panels to
speech garblers.

Some circuits are basic design ideas,
such as a monoflop using a single 7400.
Others come with p.c. board layouts
and are complete functional units, an
example is a pulse generator with vari-
able pulse width and repetition rate.

It should be made clear that this issue is
not a review of circuits already pub-
lished, nor is it a preview of designs that
will be published in the coming year.

— dark room timer

— rain synthesiser

— car clock

— kettlestat

— current source

— battery indicator

— antenna amplifier

— logic tester

— wind machine

— min/max temperature indicator

— digital contrast

— power supply

— SSB adapter

— wideband frequency doubler

— headphone adapter

— pulse generator

— over 84 other circuits

628 — elektor june 1976

vertical fet's

pa:

SWISS':

WMm

C .

•Ivlv.v.v

« ■ : : -:

plete control of the signal from the
driving amplifier.

However, this is hardly ever the case in
practice, since power transistors are not
capable of following fast input signal
variations, due to the non-linear dif-
fusion capacitance between the base and
emitter. This capacitance increases as
the collector current increases. There
exists a certain switching delay which is
characterised by the transition fre-
quency, fj. In addition, the phase dis-
crepancy between the input and output
signals, which is caused by charging and
discharging this virtual capacitor, can be
worsened by the output transistors clip-
ping (although this clipping should be
prevented in the preceding stage by
limiting the driving swing to an ampli-
tude that will not drive the final output
signal against the power supply voltage).
These transition imperfections cause a
reduction in efficiency, i.e. an increase
in the heat dissipated, so much so that,
in some cases, it may be necessary to
install a cooling fan.

High fp transistors capable of following
fast input signal variations at large ampli-
tudes are more vulnerable than low
t'X types under overload conditions, due
to their construction and manufacturing
technology. In particular, it is the
second breakdown phenomenon, occur-
ring at high collector voltages during
high heat dissipation, that can lead to
their complete destruction. This danger
can be avoided by respecting the Io^CE
diagram that shows the Safe Operating
Area (SOAR), which indicates the safe
combinations of collector voltage and
current. It can be seen that for high
fX types this area is considerably
smaller than that for the more robust
2N3055 family, and good protective
circuitry is badly needed.

Transistors respond inversely with the
emitter current, i.e. as the emitter cur-
rent rises, the response falls off. A water
tap provides a suitable metaphor:
between the order to turn off the water
and the completion of the action, the
water continues to flow, with the
volume of the wasted water being
dependent on the number of turns that
the tap was turned on. Unlike electronic
valves and FETs, the base of a bipolar
transistor always draws some current,
which can be of considerable magnitude
in the case of high power transistors.
It follows from the above considerations
that there is an urgent demand for an
alternative high power active semi-
conductor with improved characteristics
and higher safe ratings for heat dissi-
pation, current and voltage. There are,
admittedly, improved transistors such as
the low emitter concentration (LEC)
types, but at the moment they are only
suitable for small signal applications.
The demand for transistors for large
signal applications still remains. How-
ever, it appears that it is in this region
that the V-FET will be useful.

Horizontal FETs

Before discussing the new V-FET, it is
worth mentioning some aspects of the

There is always something new
under the rising sun. The Japanese
have now developed a
semiconductor called Vertical
field effect transistor', intended
for use in high power output
stages. The V-FET performance
and basic characteristics are vastly
superior to the common bipolar
transistors.

This article describes the V-FET's
construction and operation, along
with its application in commercial
circuits.

Circuit Requirements

As unlikely as it may seem, a firm
market seems to be developing for
heavy, (i.e. 60-1 20 lbs) stereo output
amplifiers capable of feeding some
1 50-350 watts to the 8 £2 load of each
channel. Obviously, the quality of these
‘audio power houses’ is dependent on
the characteristic properties of the
active elements used in their output
stages. Consider some of the difficulties
which are associated with high output
power. First, there is the problem of
high heat dissipation in the final transis-
tors. Then, the transistors themselves
are subjected alternately to high col-
lector potentials and currents, with the
condition becoming more critical as the
output power increases. It may even be
necessary to arrange the output transis-
tors in series-parallel, using the same
principle as the coachman who replaces
a single horse with a four-in-hand, so
that the output is increased although
the effort by each horse is less.

Further considerations for the output
circuit designer are the switching proper-
ties of the transistors to be used. In
the familiar class B final stage, the two
halves alternate between a current-
conducting and a current-blocking func-
tion which is, ideally, under the com-

vertical fet's

elektor june 1976 — 629

1

VGS

1

1

1

f

VGS

= 0 V

/"J

r I

1

I

I

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= _ 1

V

1

1

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= _2

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9425-2

V DS

Figure 1. Conventional (horizontal) FET con-
struction. The hatched area around the gate
indicates the depletion zone caused by the
non-conducting state of the pn junction. With
a constant Vqs, an increase in the drain cur-
rent causes the depletion zone to grow as
indicated by the dotted line, until it impinges
on the edge of the substrate. At this point
further increases in the drain potential Vqs
fail to cause an increase in the drain current
which may be regarded as saturated.

Figure 2. Drain current Iq expressed as a
function of Vqs with parameter Vqs for the
FET of figure 1. The dotted line shows the
knee potential as a function of Vqs-

conventional (horizontal) FET, which is
only suitable for low power applications
such as circuits with high input im-
pedance and low noise. Figure 1 shows
the construction of an ordinary
n-channel FET. A positive potential
between drain and source causes elec-
trons to flow from source to drain. The
gate is made of p-type material, and
when a negative potential with respect
to the source is applied to it, the
pn junction becomes non-conductive.
Now the junction is surrounded by a
depletion zone (hatched in the figure)
which is completely empty of majority
charge carriers. Figure 2 shows a family
of output curves. For a given Vqs, the
drain potential VdS and the drain cur-
rent Id increase linearly at first. The
current increase extends the depletion
zone until the point at which the zone
touches the opposite edge of the sub-
strate (shown by the dotted line in fig-
ure 1). Any further increase in Vqs fails
to increase id, so the FET virtually
behaves as a constant current source for
any higher values of Vds* The output
curves also show that more negative
values of Vqs cause the ‘knee’ to occur
at a lower Vqs so reducing the corre-
sponding saturation current. The pos-
ition of the knee for varying Vqs is
shown by the dotted line.

Vertical FETs

Both Sony and Yamaha have now devel-
oped high power FETs whose properties
are very promising. The construction
and manufacturing technology of the
Sony and Yamaha devices are similar in
that both may be considered to be made
of a large number of ‘mini-FETs’ work-
ing in parallel, but in other respects the
two devices are quite different. Sony
have developed both p-channel and
n-channel V-FETs, whereas Yamaha
have only developed an n-channel type.
Consequently, the circuits utilising these
new devices differ considerably in their
design, as will be discussed later.

Figures 3 and 4 show the construction
of the Yamaha n-channel device. Com-
pared with the horizontal junction FET,
the current flows vertically. The drain is
located at the bottom of the crystal and
its mechanical connection to the casing
has a very low thermal resistance, which
is vital since practically all the heat
produced inside the device is developed
in the drain and must be led away from
there. The channel is made of N" type
material into which a grating of P + type
material, the gate, has been embedded.
In figure 4, each square represents a
separate FET, at 5 to 10 micron
spacings. The entire chip size is about

5 mm by 5.5 mm and it consists of tens
of thousands of FETs, all working in
parallel.

The output characteristics of these FETs
are shown in figure 5, and a major dif-
ference from those in figure 2 is im-
mediately obvious: there is no knee, or
corresponding saturation voltage.
Readers once familiar with the output
curves of the old faithful triode will no
doubt be struck by the resemblance,
which has already been used in the
publicity given to these new devices, as
nostalgia is a great selling point. Those
readers will remember the one-upman-
ship in the triode-fitted amplifiers
against the pentode-equipped counter-
parts with their inherent current-
saturation effects. However, the com-
parison is not really fair, as modern cir-
cuits with high negative feedback (made
possible by the elimination of the out-
put transformer) display hardly any dis-
tortion of this kind. On the other hand,
it is much easier to trim an amplifier
which is inherently devoid of clipping
and other nasties, than one which is full
of these distortions. V-FETs present
other advantages than merely being free
of these annoyances.

The family of output curves in figure 5
may also be used to describe the oper-

630 — elektor june 1976

vertical fet's

3 , 4

ation of p-channel V-FETs. In this case
the drain current consists of a stream of
holes (positive charge carriers) flowing
vertically from source to drain. Vpg is
therefore negative. The gate is made of
n-type material and is positively biased
with respect to the drain.

Figure 6 shows the transfer character-
istics for an n-channel V-FET. Again, a
close resemblance to the triode transfer
curve may be recognised. The curve
slopes much more gently near zero drain
current than the steep exponential curve
peculiar to the conventional bipolar
transistor. This property of the V-FET
is favourable for rounding the cross-over
point in class B power stages. It must be
admitted that the slope of the transfer
characteristic can be adversely affected
by fluctuations in the supply voltage or
in the drain-source potential (such as
would be caused by a drain load im-
pedance). This is due to the negative
feedback acting on the drain potential.
The equivalent effect with thermionic
triodes is the difference in transfer
characteristics between the dynamic and
the no-load output.

Performance Figures

The data sheet gives some interesting
figures for different types of V-FETs.
Particularly impressive are the maxi-
mum ratings for the Yamaha 2SK77
type, they are not likely to be equalled
by any conventional power transistor.
All types permit a very high maximum
drain-to-gate potential, which is the
highest potential found in a V-FET. All
types are completely free from second-
ary breakdown effects, since the density
of the drain current is the same through-
out the channel. This is due to the
absence of current crowding and also to
the manufacturing technology which
permits an extremely low level of con-
tamination in the n- (or p-) channel.
Although the V-FET is basically a

Figures 3 and 4. Construction of the Yamaha
developed n-channel V-FET, which may be
considered as a large number of FETs working
in parallel. The chip size is about 5 by 5.5 mm
for the Yamaha 2SK77 type, and about 3 by
3 mm for the Sony 2SK60 and 2SJ18 types.
Maximum dissipation rating is mainly depen-
dent on the chip surface area, which gives rise
to 200 watts for the 2SK77 and 63 watts for
the 2SK60 and 2SJ18.

Figure 5. Drain current Ip as a function of
the drain-to-source potential Vqs with gate-
to-source potential Vqs as parameter. These
output characteristics for the 2SK77 V-FET
show similarity to thermionic triode charac-
teristics.

Figure 6. Transfer characteristics for the
2SK77 V-FET : drain current Ip as a function
of gate-to-source potential Vpg with drain-to-
source potential Vpg as parameter. Any load
in the drain circuit causes the slope of the
dynamic transfer characteristic to drop, with
the exception of the curved portion near the
cut-off point. These characteristics show that
the optimum quiescent current (i.e. a working
point where the slope has half the gradient of
the full swing slope for a class B stage) should
be about 400 mA.

Figures 7 and 8. Stripped version (figure 7)
and complete circuit diagram for one stereo
channel of the Yamaha B-l output amplifier.
This circuit clearly resembles the direct-
coupled output circuit for thermionic valves
and 800 loudspeakers.

voltage-controlled device, the gate does,
nevertheless, draw some current, as the
input impedance is not quite so high as
in the horizontal FET. This input cur-
rent consists of an inherent leakage cur-
rent through the barrier between gate
and channel, and a capacitive current
caused by the charge and discharge of
the source-gate capacitance and the
virtual capacitance due to the Miller
effect on the gate. Consequently, the
currents required to drive the 2SK77 are
so high that a source-follower driving
stage is needed (see figures 7 and 8), for
which the type 2SK75 has been devel-
oped (see table). In spite of this, V-FETs
offer some important advantages over
conventional power transistors. For one
thing, the input capacitance is smaller
and almost independent of the drain
current. For another, the transition
speed of all these V-FETs is 5 to
10 times faster and the power switched
at these frequencies is 2 or 3 times
higher than for the fastest bipolar tran-
sistor. High frequency distortion at the
cross-over point is practically non-
existent, especially with optimum set-
ting of the quiescent current in the
output stage.

An exclusive and very recommendable
V-FET property is the negative tempera-
ture coefficient of the drain current, i.e.
the current decreases as the crystal
temperature increases. There is, there-
fore, no risk of thermal runaway in
class B power stages in contrast to cir-
cuits with conventional transistors
where, if there is insufficient thermal
stabilisation of the standing current, the
current rises as the temperature does,
the temperature rises as the current
does, which ever-increasing circle is only
terminated when the transistors give up
the ghost. Thanks to the absence of this
cumulative effect, V-FETs need no
preventative measures against thermal
ru naway.

vertical fet's

elektor june 1976 — 631

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V-FET Circuitry in Practice

Two commercial circuits featuring
V-FETs are discussed here, namely the
Yamaha B-I type, which is a separate
final stage, and the Sony TA 8650,
which is an integrated amplifier con-
taining both the pre-amplifier and the
output stage. The discussion is confined
to the final stages; power supply, filter
and protective circuitry are not treated
(the Yamaha circuit has in total
39 FETs, 1 13 transistors, 3 LEDs,
64 diodes and 7 zeners!). Both circuits
feature class B output amplifiers, and
the dynamic transfer characteristics
involve a relatively high quiescent
current (400 mA for both). This, in
combination with the high supply vol-
age, results in fairly high quiescent heat
dissipation (64 watts per channel in the
B-I) in the final stage, but this is no
problem for these V-FETs. The tempera-

ture protection in the B-I was intended
originally to safeguard other com-
ponents, for example the expensive
computer-quality electrolytic buffer
capacitors (rated at 80°C).

A condition not found in conventional
transistor circuitry, and only revealed
on close inspection of figure 5, is that
the drain current will rise out of all
proportion if power is supplied to the
drain without sufficient bias (positive
for n-channels, negative for p-channels)
on the gate. Even for short durations,
an excessive drain current of this magni-
tude will endanger not only the V-FET
itself, but also the associated series
resistors and probably the power unit as
well. This condition only occurs at the
moment of switching the power on or
off. To prevent this, the circuit must be
designed such that at switch on, the
power is applied first to the pre-

amplifying stages, so enabling the gate
bias to build up before power is applied
to the final stage; conversely, at switch
off, the power is removed from the final
stage before the pre-amplifier.

The requirement for a bias voltage of
opposite polarity to the drain voltage
calls for more than one stabilised (or
unstabilised) power supply; if they were
of the same polarity, some of the drain
supply which is vital to obtain the full
output voltage swing, would be diverted.
To avoid this, the driver stage is
supplied with a separate power supply.

Yamaha B-I Amplifier

This stereo output amplifier will con-
tinuously deliver 160 watts per channel
into an 8 £2 load, with the harmonic and
intermodulation distortions remaining
well below 0.1%. Figure 8 gives the
circuit diagram for one channel of the

JTT

TR504

TR505

TR518

d y

X

TR506

@1

TR507

TR512

I

I

TR513

R,

I

I

JL TR510

X_i

X

TR511

TR514

-©40V

TRa

■©85 V

TRb

I

R

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9425-7

632 — elektor june 1976

vertical fet's

output stage, but the principles of oper-
ation can best be explained from the
stripped diagram in figure 7. The basic
design of the circuit may now be seen to
bear some resemblance to the once-
familiar, single-ended, push-pull power
stage featuring two pentodes (EL 86)
feeding an 800 12 loudspeaker. This
resemblance is due to the circuit being
equipped in all signal handling stages
with FETs and the single polarity
n-channel V-FETs. In this Yamaha
design, the power pair consists of two
Darlingtons (TR518, TRa and TR514,
TRb) series connected as far as DC is
concerned, and with the load connected
to the drains of the first pair and the
sources of the second. The arrangement
requires the two halves of the final stage
to be driven in push pull, with the
lower half being driven by the voltage
between the TR514 gate and the —85 V
supply rail, and the upper half by the
voltage between the TR5 1 8 gate and the
load. Ra and Rg are coupling resistors
from the penultimate stage which pro-
vides the phase inversion. Bootstrapping
makes the drain impedance of the
TR512 appreciably higher than that of
the TR513.

The V-FETs TR518 and TR514 (type
2SK75) in the output stage are arranged
as source followers; both are tied to the
—200 V rail via constant current cir-
cuits. This not only stabilises the quiesc-
ent current for these drivers, but also
applies the entire output current swing
from TR5 1 8 and TR5 14 to the gates of
TRa and TRb respectively.

The B-I pre-amplifier stages are com-

posed of three differential amplifiers in
cascade with long tail pairs consisting of
constant current circuits. The first stage
is an n-type dual FET TR501 . The input
signal is applied to the left hand gate
while the right hand gate receives a
fraction of the output signal, so pro-
vidingnegative feedback (since the input
and output are in antiphase). A dual
FET with both elements on the same
chip is necessary here since any differ-
ence in the DC characteristics of the
two would produce an offset voltage at
the output. Each half of the second dif-
ferential stage consists of two cascode
connected P-FETs (TR504, TR506 and
TR505, TR507). The two cascode
output FETs (TR506 and TR507) oper-
ate in a common gate configuration
resulting in the almost complete elimin-
ation of capacitive feedback due to the
Miller effect. A further advantage is that
linearity is guaranteed over a consider-
able drain potential swing. This is par-
ticularly advantageous in the third
differential stage, which is also cascoded
and built around the N-FETs TR510,
TR512 and TR51 1, TR513. It operates
as a phase inverter for the output stage.
The details in figure 8 need a little more
explanation. Control VR501 is used to
set the DC offset in the output stage to
zero. Control VR504, which together
with R536 forms the Ra resistor of
figure 7, adjusts the balance between
the upper and lower halves of the out-
put stage. The quiescent currents for the
output FETs TRa and TRb are adjusted
via the constant current circuit TR508
in the third differential stage, whereas

the quiescent current for the driven
TR518 and TR514 is stabilised by the
constant current circuits TR515 and
TR517. Variation of the direct currents
through TR510, TR512 and TR511.
TR513 causes the TRa and TRb bias tc
vary, and with it the drain currents.
TR508 is fed by a portion of the poten-
tial across zener diode D503, and the
controls VR502 and VR503 are used tc
set the quiescent current. The base and
emitter of TR5 1 9 are strapped via series
resistors between the positive and nega-
tive power rails (±85 V): the collector is
connected to the quiescent current cir-
cuit. This circuit makes the TRa and
TRb quiescent currents practically inde-
pendent of power supply (for the final
stage) fluctuations.

Sony TA 8650

The Sony circuit differs from the
Yamaha in the basic design concepts, as
it has recourse to both n-channel and
p-channel V-FETs. It has therefore beer
possible to make the output stages com-
pletely complementary, the same as
when conventional transistor power
stages are being used. The TA 8650.
featuring this complementary principle,
is capable of delivering 80 watts into
each 8 £2 loudspeaker with barely
measurable distortion.

Figure 9 shows the essentials (to a level
suitable for this discussion) of the cir-
cuit of one output amplifier. The final
stage, which is a class B amplifier, uses
three n-channel V-FETs (type 2SK60)
in parallel for the positive half
(T7 17 . . . T7 1 9 in the figure), and three

vertical fet's

elektor june 1976 — 633

p-channel (type 2SJ18, T720 . . . T722
in the figure) for the negative half. In
this configuration they form a com-
plementary source follower feeding the
common load. The output stage is
powered by ±60 volts. The parallel con-
nection enables each half of the output
stage to dissipate about 190 watts.

The V-FETs in the positive half are
biased negatively, while the negative half

Figure 9. Simplified circuit diagram of one
channel of the output stage in the Sony
TA 8650 integrated amplifier. This stage is a
complementary source follower with an
inherently low internal impedance, even with-
out negative feedback. The six output FETs
must be selected to have a very small spread
in the transfer characteristics between them,
since the current distribution in the three
parallel outputs in each half and in the two
halves themselves must be equal.

Table.

Characteristics of
specific V-FETs

2SK75

n-channel

Yamaha

2SK77

n-channel

Yamaha

2SK60

n-channel

Sony

2SJ18

p-channel

Sony

maximum

dissipation at

25° C

Pd

20 W

200 W

63 W

63 W

maximum

crystal

temperature

T i

1 50° C

1 50° C

1 20° C

1 20° C

maximum

drain-gate

voltage

v DGO

200 V

200 V

170 V

-170 V

maximum

gate-source

voltage

v GSO

-30 V

-40 V

-30 V to -50 V

30 to 50 V

maximum

•d

0.5 A

drain current

20 A

5 A

-5 A

maximum

•g

10 mA

gate current

1 A

0.5 A

-0.5 A

gain

M

40*

7.5**

A * # #

4* * *

slope

internal

s

30 mA/V*

1.5 A/V**

0.25 A/V***

0.25 A/V***

resistance

Rj

1k3*

5**

16***

16***

* with V ds = 80 V and l D = 10 mA

** with V DS = 30 V and l D = 2 A

** with |V DS | = 20 V and |I D | = 1 A

has a positive bias. In the no signal state,
the potential at the junction of the
sources is zero. For this reason the
respective gates are connected crosswise
across resistor R737. The necessity of
providing these gate-to-source bias po-
tentials calls for a voltage for the pen-
ultimate stage (T711 . . . T7 16) exceed-
ing that for the final stage. The required
supply used in this case is ±85 volts.

The final stage is driven from a low
impedance circuit: the emitter followers
of T715 and T716. The sum of the
drain-to-source bias potentials for the
output FETs appears across the resistor
R737. The emitter followers T715 and
T716 are powered via the constant cur-
rent circuits T713 and T714, which are
in turn fed via a diode-resistor network
from the ±85 V supply rails. Control
RT701 is used to set the potential dif-
ference across R737 and thereby the
quiescent current for the output stage.
This complex circuitry eliminates the
effect of power supply fluctuations
upon this quiescent current.

N.B. The six output FETs are selected
for accurate equality of |Vqs| at a
constant drain current, which is impera-
tive for uniform current and dissipation
distribution among the six power FETs.
Unfortunately, this means that a failure
of any FET in the final stage will mean
replacing all six.

The driver stage T715, T716 is sym-
metrically controlled via resistors R735
and R736, by the pre-amplifier. The
latter is composed of three differential
stages, the first of which is designed as
an n-type dual FET T601 operating on

634 — elektor june 1976

vertical fet's

led light show

the difference between the input signal
and an inverse feedback signal derived
from the output circuit via the potential
divider of R608 and R616. This first
stage feeds the amplified signal to the
second stage, T602, T603. The T607
collector circuit in the third of these dif-
ferential stages includes a current mirror
T604 fed from the collector of the
other transistor T606 in the third stage.
This circuitry guarantees symmetrical
control of the driver and hence the
output stage.

Conclusion

The object of this article has been to
provide our readers with some insight
into the properties and possible appli-
cations of these new beasts. The high
quality of the commercial circuitry
described goes without question,
especially as regards the absence of
cross-over distortion (although this has
been achieved at the cost of a quiescent
dissipation that equals the maximum
output power of some small conven-
tional power amplifiers!)

Despite the impressive figures the rela-
tionship between quality and price is
not in all cases more favourable than
that for equipment using conventional
bipolar transistors with a few FETs
thrown in. In this respect, it is worth
noting that Sony offers two interesting
alternatives in the shape of amplifiers
TA 4650 and TA 5650, which are con-
siderably lower in price and have an
output power only 2 or 3 dB down.

H

LEDs are now finding applications
in more and more varied fields and
here is a unit to introduce them
to the world of discos and the
trendy scene. Small is beautiful, as
they say, and the LED light show
can brighten up the front panel of
an amplifier, tuner or tape
recorder.

The light show described here is fairly
inexpensive and simple to build, and is
distinguishable from conventional light
shows, not only by its use of LEDs
(light-emitting diodes), but also by its
filtering system and the lack of a
(hazardous) high voltage. It is intended
as a decorative addition to an audio set-
up by installing the LED light show in
the front panel (say) of the amplifier or
tuner, perhaps. This will give an attract-
ive (even if somewhat miniaturised)
visual rendering of the music; the dis-
play is enhanced by the use of three
different colours.

Design philosophy

Consider the requirements of a light
show: its task is to accentuate audio
information with a visual display. The
audio information will be from various
sources (e.g. musical instruments), each
of which has a characteristic frequency
spectrum and amplitude. Rather than

attempting to respond to the complete
frequency spectra, the light show is
designed to select a number of fre-
quencies which are representative of the
incoming signal. As for the problem of
varying amplitudes, the light show uses
dynamic compression of the audio sig-
nal. If the visual information possessed
the same dynamic range as the music,
the difference between minimum and
maximum light intensity would be
annoying. Another consideration is that
visual selectivity is much less than
acoustic selectivity, so the frequency
bands chosen for visual representation
are deliberately restricted. It is gener-
ally accepted that audio frequencies
are divided into three groups for dis-
play: low, medium and high. However
the boundaries which lie between these
groups are not so well defined. Many
applications leave overlaps between
these groups, but in this case it has been
found that leaving gaps gives a better
solution (see figure 1).

Figure 2 is a block diagram of the light
show. The compressor which is used tc
reduce the dynamic range of the audic
signal can be of a much lower quality
than one for use in an audio circuit. The
only restriction is that the harmonic
distortion produced by (say) the middle
channel should not be visible on the
high channel. The characteristic of the
compressor should not be such as tc
amplify noise or hum which would then
be displayed during quieter passages
Even so, the visual effect is still im-
paired by peaks, but since the response
of the amplifiers A1 ... A3 is unimport-
ant, they are designed to limit on a
fairly low input signal to mask non-
linearities in the compressor. The filters
feeding A1 ... A3 are low-pass, band
pass and high-pass, respectively. In the
circuit described here, use is made ol
double-T filters. This facilitates the
early-limiting design of the amplifiers
The double-T filters are of simple
design and give good selectivity, bul
they have the disadvantage of beinfc
peaked. This can be remedied b>
damping the filters, bearing in mine

ed light show

elektor june 1976 — 635

the restriction, still, that the frequency
Dands must not overlap.

[n designing the amplifiers A1 ... A3 it
nust be remembered that the pro-
gramme material upon which this type
}f device is most commonly used con-
:ains a predominance of the low fre-
quencies. The gains of A1 ... A3 must
therefore be such as to overcome this
disparity.

rhe point at which the light show is
;onnected into the audio circuit can
/ary between a pre-amplifier and a
100 W output amplifier. The com-
oressor should not only be resistant to
the very high levels which may well
occur, but must also continue to func-
tion normally when they do. In addition,
the input impedance must be suf-
ficiently high so that the circuit to
which it is connected is not loaded by
it.

[n most light shows, the loads of the
amplifiers A1 ... A3 are driven by
triacs or thyristors, either via an iso-
ating transformer or an optocoupler.
Mo relationship between light intensity
and amplitude can be obtained, since
the condition controlling the lamp state
ts binary, i.e. the lamp is on if the ampli-
fier output is above the trigger voltage,
and off if it is not. How the relationship
is obtained in this particular design is
explained shortly.

The Circuit

Figure 3 gives the circuit diagram for
the light show. The compressor is
formed by the circuit around IC1 (741),
which is connected as a non-inverting
amplifier whose gain may be varied
from 20 dB to 60 dB by means of PI.
When the emitter voltage of T1 becomes
greater than +6.5 V D1 and D2 start
conducting, thus reducing the input
signal and hence the output signal until
equilibrium is restored. Since the time
constants in the control circuit are
fairly large, it takes some time for
equilibrium to be restored. Asymmetri-
:al compressors require a fairly slow
control rate because otherwise motor-
boating (low frequency oscillations)
could easily occur.

rhe output of the compressor stage is
fed to the three double-T filters, as
»hown. These filters have enough output
current to drive the LEDs through
220 £2 resistors, allowing the relation-
ship between amplitude and light
ntensity to be retained.

Construction and Operating

rhe circuit should preferably be given a
netal housing, and a screened lead
should be used between the input
socket and the compressor input, with
:he screening connected to the housing
it the input socket. The connections
Tom the filters to the LEDs can be
made with ordinary connecting wire.
\fter construction and careful inspec-
:ion of the completed circuit, the light
show is set up in the following way:
idjust PI to give maximum gain (slider
igainst R4) and then P2 . . . P4 (sliders
igainst C5). Connect the compressor

input to the loudspeaker or to the pre-
amplifier output so that the audio signal
is fed to the light show (it is better to
avoid classical and choral music while
setting up). Now adjust PI . . . P4 so
that the light display gives the best
(subjective) match with the music. The
setting is a matter of personal taste and
it may be found that taste demands
different settings for different types
of music. If instabilities occur in any of
the channels, a lower value must be
selected for the corresponding resistor,
R 13, R 19 or R25.

Figure 1. Two ways of dividing frequencies
into groups or channels. The light show gives
better optical effects if the second method
of leaving gaps between the groups is em-
ployed.

Figure 2. Block diagram of the light show
which at this level of detail appears the same
as a conventional one, consisting of com-
pressor, channel filters and channel amplifiers.

A printed circuit board and component
layout are shown in figure 4.

Compres-

sor

%

%

2

%

3

<g>

9403-2

636 — elektor june 1976

led light shov

01,02,04,06,08 = 1 N4148

ct

a i
33k

C2

560n

lOOn

D1

02

R3

C3

C4

100/i

10V

C7

'470k

47/J

JOV

<N

C15

R19

-*

CN

CN

33n

C17

4x1 N4001

IC4

100n

R21

’0.

HI 1 220fl

— )12V

R22

C18

4n7

R23

C19

R24

{3E EH'

C20

n

4n7

R25

LED

lOn

J

9403-3

Parts List for Figure 4.

Resistors:

R1 = 33 k

C5 = 330 n

R2,R3,R9,R 1 5,R21 =470 k

C6 = 470 n

R4 = 100 n

C7 = 47 p/10 V

R5,RS = 47 H

C9.C10.C11.C12 = 680 n

R6,R7,R25 = 100 k

C14.C16 = 18 n

R10,R12,R16,R18,R22,R24 = 4k7

Cl 5 = 33 n

R 1 1 ,R 1 7,R23 = 2k2

Cl 8.C20 = 4n7

R13.R19 = 220 k

C19 = 10 n

R14,R20,R26 = 220 n

C21 ,C22 = 1000 /i/16 V

PI = 10 k

P2,P3,P4 = 470 k

Semiconductors:

Capacitors:

IC1.IC2.IC3.IC4 ■ 741

T1 = BC 547B

Cl - 560 n

D1,D2,D4,D6,D8= 1N4148

C2,C8,C1 3,C1 7 = 100 n

D3 = 5.1 V/400 mW zener

C3 = 470 p/3 V

D5,D7,D9 = LED

C4 = 100 p/10 V

D10,D11,D12,D13= 1 N4001

Figure 3. The LED light show makes use c
the cheap 741. Channel separation is achieve
by means of damped double-T filters.

One advantage of this filtering method is the
when connected to an FM receiver the stere
pilot tone gives no trouble.

Figure 4. Printed circuit board (EPS 9402
and component layout for the light show ci
cuit of figure 3. The printed circuit has bee
designed so that either TO-5 or dual-in-lin
packages may be used.

led light show

elektor june 1976 — 637

4

pp

\o <H ho ^ 9

QQQQO nn

O O

IIC2I

0 0 1 T

uuuuuuu 6

o- R12 -o

QQOQQOO

°IC3°

o ,C3 o

06

uouuooo
0~|rib |-o 0-[ht7 |-o ° ^ °

1 car ^

IT

QDQOQQQ

^IC4^

O O 1 “T“

uouuuuu 1 6

in

CU

DC

Oil
1 01

□Cl

T c ' lf

O- RS4 -O 0 -|r53 | 0

638 — elektor june 1976

digi bell

Like the 'Big Ben 95' circuit
published in Elektor 2 this is a
design for an electronic doorbell
that plays the well-known
'Westminster Chime'. Unlike the
Big Ben circuit, where each note
had to be tuned individually, the
programming of the Digibell is
carried out digitally. Therefore
all the notes are automatically
in tune with each other, this
means the only tuning necessary
is a single adjustment to set the
entire melody in the required
key.

Most electronic chimes rely either on an
individual oscillator for each note, the
oscillators being switched in the appro-
priate sequence, or else use a voltage-
controlled oscillator where different
control voltages are switched in the
correct sequence to control the oscil-
lator frequency. The disadvantage of
both these systems is that each note
must be individually tuned, and if the
tuning of one note drifts this spoils the
entire melody.

In the Digibell the notes are obtained by
digital frequency division from a single
frequency. This is accomplished using a
programmable divider. Therefore the
notes are always in a fixed harmonic
relationship.

The natural notes in an octave (i.e.
omitting sharps and flats) are in the

following frequency ratios to the funda-
mental (C):

CDEFGABc
1/1 9/8 5/4 4/3 3/2 5/3 15/8 2/1

It follows that the period of each note,
relative to the fundamental, is the recip-
rocal of the appropriate frequency ratio.
Using period rather than frequency will
greatly simplify the calculations re-
quired for the counter programs. There-
fore, the programmed count for a par-
ticular note is proportional to the
period of that note.

A simple counter cannot deal with
vulgar fractions, so the next step is to
give all the fractions a common denomi-
nator (in this case 180). The numerators
can now be expressed as integral

14

1n5

1n5

R5

-•

1/2 7473

16

11

14

16

11

clear 0 load

1C 5

down 74193 botrow

GND

At B1 Cl D1

10

R6

G

0

m

O

if)

T

2k 2 P2

\

A

h I

10

N3|

4

5

13

3l D4 D5 06l

" ” " T

clear Q load

1C 6

down 74193

borrow

GND

A2 B2 C2 02

15

1 10

D1T D2-“

Li

112 34567 91Q11

A

10 9

13

D

8

14

12

D7

012 3456789

IC3 ©

7442

GND

A B C D

*-o

16_

8

08^

13

1

o

Ji FF1 CM

clockl

IC7

clear 1

T5 —

12

15

14

* 13

12

12

9

8

11

BD

8 C

1C 2
7490

©

A

GND

4 1 Jj

14

o

10

R3

X

*

co

<0

r

T-- L 3

R4

if)

N 1.2.6.7 = 1C 1 =7400
N 3,4,5 = 1C 4 =7400
D1 . . . D8 = DUG

looj^fev 1 oop/s v

1

clock/

FF2 Clear 2
IC7 g™

1/2 7473

4

8

6

D-

11

rb

V

P*.

R 1

fN

R2

r*

I

X

, jL

5V

<s>

/

9325-1

< 2 >

digibell

elektor june 1976 — 639

numbers and converted into binary code

(since

this is what the

counter will be

programmed with).

This results in the following table:

Note

Decimal

Binary

c'

90

0101 1010

b

96

01 100000

a

108

01 101100

g

120

01 1 11000

f

135

1000011 1

e

144

10010000

d

160

10100000

c

180

10110100

B

192

1 1000000

A

216

11011000

G

240

1 1 1 10000

It is evident, from the above table, that
if the programmable counter is set to
count to 90 and is fed with a clock fre-
quency 90 times that of c' then the out-
put frequency will be c\ If it is set to
count to 180 and is fed with the same
clock frequency then the output will
be c, one octave below c'. I bis is how
each note is synthesised from a single
clock frequency. Since each note bears
a fixed frequency ratio to all the other
notes it is obvious that the only tuning
necessary is to adjust the clock fre-
quency until the melody is in the re-
quired key.

The Westminster Chime uses only the
notes G, c, d and e in the sequence e, c,
d, G, G,d, e, c, so at first sight it appears
that division ratios of 240, 1 80, 1 60 and
144 are required. By coincidence how-
ever, it happens that these numbers are
all divisible by four, so the division
ratios can be reduced to 60, 45, 40 and
36. This means that the programmable
counter can be of shorter length, and
that the programming is simplified.

Figure 1. Circuit diagram for Digibell.

Figure 2. Truth table for the counter
program.

Figure 3. Timing Diagram which shows se-
quencing of the Digibell.

In addition to getting the notes right it
is also important to achieve the correct
tempo. T he first three notes each have
a duration of one crotchet, while the
fourth note has a duration of one minim
(two crotchets). This is followed by a
rest of one minim duration. The fifth,
sixth and seventh notes are each of one
crotchet duration, while the final note
has a duration of one minim. The total
duration of the tune is thus 1 1 crotchets.
When designing the circuit that per-
forms the sequencing this must be
taken into account.

The Circuit

The circuit of the Digibell is given in
figure 1. The clock pulse generator
consists of two NAND gates N 1 and N2.
They are connected as an astable multi-
vibrator whose frequency and duty-
cycle can be adjusted with PI and P2.
The programmable counter consists of
two presettable up-down counters
type 74193. These are connected to
count down from a preset number to
zero, the number being loaded into the
data inputs Al-Dl, A2-D2 before the
start of each count. The operational
sequence for the presettable counter
is as follows:

initially the borrow output of IC6 is
low. This lakes the load inputs of IC5
and IC6 low, so the data on the inputs
A1-D2 is loaded and the count com-
mences. During the count the borrow
output is high, but when the count
reaches zero it again goes low, the data
is reloaded, the count recommences and
so on.

Since the borrow output is low for only
a small proportion of each count the
output waveform is very asymmetric
and is not suitable for use as an audio

tone. For this reason FF1 is connected
to the borrow output and produces a
square wave with a 1:1 mark-space
ratio (50% duty-cycle) at half the fre-
quency (i.e. one octave below) the bor-
row output.

To produce the Westminster Chime
melody the programming numbers cor-
responding to the four required notes
must be fed to the data inputs of the
presettable counter in the correct se-
quence. This is controlled by a second
counter (type 7490), and a 7442 BCD-
to-decimal decoder.

When the bell-push SI is pressed the Q
output of FF2 goes high, enabling the
astable multivibrator N6/N7, which
feeds clock pulses at about a 2 Hz rate
into the A input of IC2. These are
counted by the 7490 and the BCD out-
puts of the 7490 are decoded by the
7442. The 10 outputs of the 7442 go
low in turn, at each step feeding a
different number into the data inputs
of IC5 and IC6 via the encoder compris-
ing N3, N4 and D3 to D6. (Note that
the 7442 has active low outputs, i.e. out-
puts are normally high and go low when
enabled by the appropriate input code).
On the tenth clock pulse the D output
of IC2 goes low, clocking FF2 back to
its original state (Q output low) until
the next time the bellpush is pressed.
The correct tempo of the melody is
achieved in the following manner. If
each note were sustained until the next
clock pulse occurred then the notes
would simply slur into one another
without a pause. This is avoided, and
the rest in the middle of the tune is
included, by means of N5 and diodes
Dl, D2, D7 and D8.

At the start of the sequence the 0 out-
put of IC3 i low so FF1 is held in the

COUNT

IC3 OUTPUTS

IC5,

IC6 DATA INPUTS

BINARY

DECIMAL

NOTE

01 23456789

D2C2 B2 A2D1 Cl

B1

A1

0

0111111111

0

0

1

0

1

1

0

0

44*

—

1

1011111111

0

0

1

0

0

1

0

0

36

e

2

1101111111

0

0

1

0

1

1

0

1

45

c

3

1110111111

0

0

1

0

1

0

0

0

40

d

4

1111011111

0

0

1

1

1

1

0

0

60

G

5

1111101111

0

0

1

0

1

1

0

0

44*

—

6

1111110111

0

0

1

1

1

1

0

0

60

G

7

1111111011

0

0

1

0

1

0

0

0

40

d

8

1111111101

0

0

1

0

0

1

0

0

36

e

9

1111111110

0

0

1

0

1

1

0

1

45

c

* Not important as output of FF1 disabled during rest

3

clock

1 1 1

i i i i

l 1 1

1

“i r

“1 1 — 1 1

~l 1 — 1

clear FF1

T

L

J

1

J FF1

1 1 L

_J L_

_l

|

J L_

1 1 1 1

1 1

Q FF1

mm

1^1

r j |

l.y.w.vl Kw.v.vJ

1 .•#•••••••• vl r.v.v.v.l

— J |

|V.V.V.V.V.V.V.V|
r-y v.wv.vi

•

-J mXil

9325-3

640 — elektor june 1976

digibef

clear state and there is no output.
During notes 1, 2 and 3, pin 12 of
N5 is high and pin 13 is switched
alternately high and low by the out-
put of N6. The output of N5 thus
gates the J input of FF1 so that there
is an output only when the clock pulse
(output of N6) is low. The first three
notes thus have a duration of half a
clock pulse.

On the fourth note pin 12 of N5 goes
low, so the output remains high what-
ever N6 does. The J input of FF1 is thus
high and the fourth note has a duration
of one clock pulse. On the fifth step
output 5 of the 7442 goes low, so FF1
is held in the clear state via D1 and
there is no output. This is the rest.

The next three notes are all of half a
clock pulse duration, but on the final
note pin 13 of N5 is held low, via D7,
the output of N5 holds the J input of
FF1 high and this note has a duration
of one clock pulse.

To make the sequence of operations
clearer, a truth table for the counter
programming and a timing diagram
for the sequencing are given in figures 2
and 3. Figure 4 shows a p.c. board and
component layout for the Digibell. For
use as a doorbell the output of FF 1
must be amplified to a level suitable
to drive a loudspeaker. The output

/I

Parts list for figure 1

Resistors:

R1 ,R2 = 2k7

R3 = 68 k

R4 = 15 k

R5,R6 = 1 50 12

PI ,P2 = 2k2 adjustable

Capacitors:

Cl ,C2 = 1 n5
C3,C4 = 1 00 m/6 V

Semi-conductors:

D1 . . . D8 = DUG
IC1JC4 = 7400
IC2 = 7490
IC3 = 7442
IC5JC6 = 74193
IC7 = 7473

SI = Push button switch

Figure 4. p.c. board (EPS 9325) and com-
ponent layout.

Figure 5. A possible amplifier for use with the
Digibell.

9325-5

attenuator R3/R4 may or may not bt
required, depending on the sensitivity
of the amplifier used, or they may bt
replaced by a potentiometer of betweer
10 k and 100 k to provide a volume
control.

market

elektor june 1976 — 641

Divide-by-Four Gigahertz
counter from Motorola
Semiconductors

Communications engineers will be
interested in a new integrated
circuit from Motorola known as
the MCI 699 dividc-by-four
gigahertz counter.

This is a very high speed device
for prescalcr applications. The
clock input requires an a.c.-
coupled driving signal of
160 mVpp amplitude (typical). A
sine-wave signal is acceptable for
frequencies from 50 MHz to
1.2 GHz. Below 50 MHz wave-
shaping is recommended. With
pulses which have good rise and
fall times (in the order of 1 to
2 nsec), the MC1699 has no
lower limit on clock frequency.
The clock toggles two divide-by-
two stages and the complemen-
tary outputs (50% duty cycle)
are taken from the second stage.

DIVIDE -BY- FOUR
GIGAHERTZ COUNTER

V'm + 2V d.c. Vout

COUNT FREQUENCY
TEST CIRCUIT

Ins/div

OPERATING
CHARACTERISTICS
AT 1-2GHz

ins/div

OPERATING
CHARACTERISTICS
AT 1-5GHz

The MCI 699 includes clock
enable and reset inputs both
compatible with MECL1 1 1 volt-
age levels. The reset operates only
when either the clock or the
enable is high and provides in-
creased flexibility for counter
and time measurement require-
ments.

The MCI 699 is supplied in a flat
ceramic package (F Suffix) for
compact assemblies and soon will
be available also in a DIL ceramic
package for easier mounting.

Motorola B. V.

Emmalaan 41, UTRECHT,

The Netherlands

Microwave Power
Transistor

Motorola have just announced a
state-of-the-art microwave power
transistor, the MRF 835. Charac-
teristics specified at 870 MHz
using a 12.5 V DC supply arc
15 watts output power, 7.0 dB
minimum gain and 50% ef-
ficiency.

High gain, high power transistors
actually consist of a few hundred
transistors in parallel. Current to
and from these doped regions is
carried by metal conductor
stripes deposited on top of the
die. These stripes must withstand
high current densities. In order
to achieve good prefomiance at
frequencies as high as 950 MHz
Motorola make these ‘fingers’
extremely narrow. However, in
conventional designs, aluminium
in narrow lines with high current
density migrates, thus causing
early failure of the device. In
the MRF 835 Motorola have over-
come these problems by using a
gold metallisation system -
because the automatic weight of
gold is higher than that of alu-
minium the migration is greatly
reduced and the mean-time-
between-failure figure is increased
1,000 to 10,000 times.

The MRF 835 is designed specifi-
cally for mobile radio applications
at frequencies around 900 MHz
and incorporates Motorola’s
‘Controlled Q’ built-in matching
network which ensures broadband
performance.

Motorola B. V.

Emmalaan 41, UTRECHT
The Netherlands

High current digital
clock

AMI Microsystems have intro-
duced a new digital clock module
which offers a high current out-
put for direct drive of large LED
displays as used in clocks, clock
radios, and timers/ elapsed-time
counters.

Designated S1998A, it provides

more than 8 mA per segment, and
can be directly substituted for
the industry-standard S1998 in
high current, low voltage display
applications. The 1998A directly
interfaces with both solid-state
LED displays, and fluorescent/
gas discharge displays. The time-
keeping function operates on
50 Hz or 60 Hz inputs, and the
display output is available with
either AM/PM indicators or
24-hour format options.

Other outputs include timed
radio turn-off, and radio/alarm
enable. A power failure indication
is provided to inform the user of
an incorrect time display. The
S1998A also incorporates a
presettable 59-minute count-
down timer, an alarm with snooze
feature, and unlimited snooze
repeat.

Clock input noise rejection cir-
cuitry eliminates the need for
external filtering of the line fre-
quency input. Reset-to-zero
circuitry is included for timer/
elapsed time applications, and
blanking control also allows the
use of several circuits in parallel
with a single display for multiple
event timing.

The S1998A, which can operate
from power supplies between
8 and 26 V, is pin compatible
with the S1998, MM5316,
EA5316, and FCI3817.

AMI Microsystems Ltd.

108 A Commercial Road,

Swindon, Wiltshire, England.

Low profile 1C socket

Molex have announced the avail-
ability of a range of low profile
dual-in-line integrated circuit
sockets.

Designated the 6197 series, they
consist of a 94 V-0 black poly-
ester polarized housing containing
either 14 or 16 discrete pin
sockets. These utilize side-wiping
contacts, which offer significantly

greater contact surface than the
more conventional edge-bearing
type. Contacts are of 60Cu 30Zn
cartridge brass, and are available
in a variety of finishes including
tin plate and gold over nickel.
Optional contact materials such as
phosphor bronze, and alternative
special contact finishes, are also
available.

Molex Electronics Ltd.,

1 Holder Road, Aldershot,

Hants GUI 2 4RH.

Multi-family logic probe

Designed to simplify and speed
logic circuit testing, this new
S 125 model 545 A logic probe
from Hewlett-Packard indicates
digital states and pulses in both
high level (CMOS) logic and low
level (TTL) logic. An unambigu-
ous single lamp indicator displays
high or low level or detects bad
level and open circuit conditions.
CMOS and TTL operation is
selected with a slide switch.

CMOS logic threshold levels are
variable and set automatically.
Now, nearly all positive logic up
to +18 volts dc can be sensed
using one probe. These families
include: TTL, DTL, RTL,

CMOS, HTL, HiNIL, NMOS
and MOS.

Another feature of the model
545A is a built-in pulse memory
which, along with the display, will
catch intermittent pulses. When

a logic change occurs, the
indicator lamp turns on and
remains lighted until the memory
is reset.

Pulse stretching is provided so the
operator can sec fast pulses as
short as 10 nanoseconds with the
blinking display. Pulse trains to
a frequency of 80 MHz are
detected in TTL logic, and to
40 MHz in CMOS logic.

Light and rugged, this hand-held
model 545A is fully protected
against voltage overload. Power
required for TTL operation is
4.5 to 15 volts DC, and for CMOS
operation is 3 to 18 volts DC.

To use the 545A, the operator
connects the probe to the circuit’s
highest level power supply, sets
the slide switch to the appropri-
ate logic family, then probes.
Open, pulsing, or stuck nodes and
gates are quickly detected.

Hewlett Packard, P.O. Box 349,
CH-1217 Meyrin 1 Geneva,
Switzerland

642 — elektor june 1976

market

Figure 1. Block diagram of an
Echo Sounder. The ultrasonic
transducer T operates both as
transmitter and as receiver.

Figure 2. The circuit of an Echo
Sounder constructed around
LM1812. The transmission fre-
quency for underwater distance
measurement is about 200 kHz.

Figure 3. This block diagram is
intended to complement figure 2
to make clear at which stages the
external components are connec-
ted to the 1C.

Figure 4. A Sodar equipment with
the LM1812 for operation in air.
It operates with a transmitting
frequency of 40 kHz. The ef-
ficiency is improved by the stage
enclosed on the right of the figure,
the purpose of which is to extend
the internally produced 1 jus pulse
to 5 ps.

LM1812 Universal
Ultrasonic Transceiver

The National Semiconductor
LM1812 IC consists of a 12 W
ultrasonic transmitter, a selective
receiver and indicator drive cir-
cuitry on a single chip. It is
available in an 18 pin D1L plastic
package. The circuit was devel-
oped primarily for use as an
underwater echo sounder (Sonar).
As well as measuring water depth
it can also be used to locate the
position of shoals of fish and
other immersed or sunken
objects.

The IC may also be used with
ultrasonic transducers in air,
which opens up a completely
different range of applications.

For example, it is possible to
measure the level of corrosive
liquids where a sensor cannot be
dipped in the fluid. Other
possibilities include collision
warning systems and intruder
alarms (ultrasonic radar -Sodar).
Finally, it is also possible to trans-
mit data over the ultrasonic link
so that communication or remote
control systems are possible, both
in air and underwater. One appli-
cation would be the remote
control of model submarines,
which is virtually impossible by
any other means.

In order to understand the oper-
ation of the circuit a block
diagram of an echo sounder is
given in figure 1. The transmitter
(block A) feeds the ultrasonic
transducer T with a burst of 1 ps
pulses for the duration of the
transmitting phase (about 800 ps).
In under water applications the
pulse repetition frequency is
about 200 kHz. During this
period the receiver (blocks

C to F) is switched off to avoid
damage by the high transmitter
power. This is indicated symboli-
cally by switch S, but is of course
accomplished electronically
within the IC.

The ultrasonic pulses applied to
the transducer are coupled into
the water and spread out as
spherical wavefronts. When the
sound waves strike the bottom or
some other objects they are
ultimately received by the trans-
ducer and converted back into
electrical impulses. These are
amplified and detected by the

receiver which is now activated.

The time duration between
transmission and reception of the
burst of pulses is proportional to
the distance between the trans-
ducer and the reflecting object.

In the common type of commer-
cially available echo sounder the
timing is carried out electro-
mechanically using a constant
speed motor (M). The motor has
a disc attached to its shaft the
periphery of which are mounted a
small neon lamp and a magnet,
180° out of phase. Once every

Legend for figure 1

A Transmitter, power stage
B Modulator
C Receiver

D Surge Value Detector
E Pulse Sequence Detector
F Integrator
G Indicator Driver
H Indicator

I Control, Keying Ratio
K Control, Transmitter
M d.c. Motor

S Transmit/Receive Switch
T Ultrasonic-Transducer
Pt Gain Control
P 2 Interference Suppression
Control

Legend for figure 3

A Transmitter, power stage
B Modulator
C a Receiver, 1st. stage
Cb Receiver, 2 nd. stage
D Surge Value Detector
E Pulse Sequence Detector
F Integrator
G Indicator Driver
I Control, Keying Ratio
S Transmit/Receive Switch
T Ultrasonic-Transducer
Pi Gain Control
P 2 Interference Suppression
Control

a = Transmit Pulse Sequence
b= Measurement Range

market

elektor june 1976 — 643

mHRKeTmHRKeTmm

he* mn

PF F

Mum m

mnujpiip)

revolution the magnet induces a
pulse in a pickup coil (block K).
This pulse triggers the transmit-
ting sequence by controlling the
modulator (B).

The ultrasonic wave sent out by
the transducer is of course subject
to the inverse square law, and
since it must traverse the distance
between the transducer and the
reflecting object twice it is atten-
uated very severely by the time it
returns to the transducer. Energy
absorption by the reflecting
object and the efficiency of the
transducer must also be taken
into account, and it is evident
that the receiver must be very
sensitive.

The receiver consists of a
multistage amplifier (block C),
with gain control provided by the
potentiometer PI. This is
followed by a threshold gate
(block D), which allows only sig-
nal exceeding a certain amplitude
to pass. This ensures that noise
and delayed echoes from very
distant objects cannot cause a
spurious indication.

The signal is further processed in
blocks E (pulse sequence detector)
and F (integrator). These together
form a pulse width detector,
which performs two functions. It
is first determined whether a valid
echo has been received by
ensuring that the received signal
is of the same duration as the
transmitted signal. If more than
five consecutive pulses in the
sequence are missing then no
indication of depth is given. This
ensures that any interference
pulses strong enough to pass the
threshold gate will still not cause
a spurious indication. The degree
of interference suppression may
be adjusted by P2.

If a valid echo has been received
then the output driver (block G)
is triggered and produces an out-
put pulse that is stepped up by a
transformer to strike the neon.

The angle through which the
motor shaft (and hence the neon)
has turned before the neon strikes
depends on the distance between
the transducer and the reflecting
object. The rotating disc is
mounted behind a circular scale
with transparent divisions marked
off in fathoms, feet or metres.
Figure 2 shows a practical circuit
for an echo sounder using the
LM1812, while figure 3 shows
how the external components
associated with figure 2 tie in
with the internal circuitry of the
LM1812. The pulse induced in
the pickup coil L3 by the rotating
magnet activates the transmitter.
The 200 kHz sinewave oscillator
is tuned by LI and C3 (it also
tunes the receiver gain stages. See
figure 3). The output of this
oscillator is amplified and limited

MOD

to provide a 200 kHz squarewave
that is used to trigger a mono-
stable that produces the 1 /is
pulses. After amplification by
the transmitter output stage the
pulses appear across the trans-
ducer T.

L2, C2 and the capacitance of
the screened transducer lead form
a parallel resonant circuit that can
be tuned to the transmitting fre-
quency by adjusting the core of
L2. In this circuit an LED D1 is

used rather than a neon. If
additional receiver gain is required
then an extra stage of amplifi-
cation may be connected between
blocks C a and Cb-
This system relics for its accuracy
on the speed stability of the d.c.
motor. Slip rings must be used to
make connection to the neon
unless a rotating transformer is
used, and the system inevitably
suffers from mechanical wear.
However, it is cheap and provides

an easily interpreted analogue
readout, and echo sounders using
these principles are popular with
small boat owners.

A completely electronic system
can be constructed by replacing
the motor arrangement with an
electronic digital counter. The
transmitter can be activated by a
rectangular pulse of about 1 ms
duration. This also opens a gate to
the clock input of the counter,
which is fed by pulses from a

644 — elektor june 1976

market

Figure 5. Additional circuit for
triggering an acoustic alarm in
anti-collision devices or burglar
alarm systems.

Figure 6. Pinout of the LM1812.

stable clock pulse generator. The
combination of R2 and D1 in
figure 2 can be replaced by a
5k6 resistor, and when the
returning unltrasonic signal is
received a negative going pulse
(from about +V b down to 1 V)
is available at pin 14. This can be
used to store the count and to
reset the counter ready for the
next count. Simply by choosing
the appropriate frequency for
the clock pulse generator the out-
put of the counter can be made
to read in fathoms, feet, metres
or any required units of length.

Underwater Communications

Information can be amplitude-
modulated onto the carrier by
feeding a low-frequency (e.g.
audio) signal into the modulator
input pin 8, rather than simply
switching the transmitter on and
off with digital signals. The
received signal must be taken out
of the receiver at a point before
the signal processing stages
(since after signal processing it
is no longer an amplitude modu-
lated carrier). A convenient point
to take off the signal is at the LC
circuit L1/C3, connected to pin 1,
which tunes both the transmitter
and the receiver. The signal can
then be fed into a high input
impedance buffer stage followed
by an AM detector and audio
amplification stages.

It is also possible to use other
modulation techniques that arc
not so wasteful of carrier power
as AM, notably Frequency
Modulation (FM) and Pulse
Width Modulation (PWM).

Notes for Tables I and II

Note 1 : If the 1C is operated at
higher temperatures, then load
derating should be allowed for.
This should refer to a chip
temperature of +125°C and a
thermal resistance of +167°C/W.
This applies to an 1C soldered
into a printed circuit board with
stationary surrounding air.
Because the system is being used
for pulsed operation, the heat
resulting from the dissipation in
the enclosure is only slight.

Note 2: During the measure-
ment of the sensitivity, an
attenuator of 500:1 was fitted, to
ensure reliable measurements at
higher input levels.

Note 3: The 'Modulator

Threshold Voltage' is the volt-
age which has to be applied to
pin 8 to bring the system into
the 'Transmit' condition. The
current flowing in pin 8 should
be limited to 1 ... 10 mA.

LM1B12

Pulse sequence detector

Interference limiter

Display control

Ground

Display output

+Vb, transmitter

+Vb

Key sequence limiter

Ground

Table I

ABSOLUTE MAXIMUM RATINGS

Supply voltage +V b (Connections 12, 6 and 4)

Dissipation (Note 1)

Operating Temperature Range T amb
(Ambient)

Storage Temperature Range

Maximum Lead Temperature during soldering
(Solder duration 60 s max.)

0°C

-65° C

18 V=
600 mW
. . +70° C

. +150°C
+300° C

Pin

Function

^ext

(min)

Vmax

(Instantaneous
value V s )

'max

1

LC-Circuit

30 V

2

Input 2nd. stage

18 V=

50 mA

3

Output 1 st. stage

18 V=

4

Input 1st. stage

50 mA

6

Transmitter Output

36 V

1 A

(Transmitter 'Off')

for 1 fis

7

Modulator Output

75 k

18 V

8

Modulator

50 mA

9

Pulse Width,

passage through zero

7 V

11

Key Sequence

Limitation

50 mA

12

+v b

18 V=

13

+V b -T ransmitter

18 V=

14

Display Output

25 V=

1 A

(if 'Off')

for 1 ms

16

external Display

Control

2 M

18 V

17

Interference

Limiter

50 mA

18

Pulse Sequence

Detector

50 mA

Table II

(+V b ~ 12 V, T amb ~ +25 C)

Parameter

Conditions

Min.

Typical

Max.

Unit

Sensitivity

Note 2

200

600

/jV (V ss )

Transmitter (V sat )

rl = io n

1.3

3.0

V

Transmitter Leakage

Pin 6 = 32 V

0.01

1.0

mA

Current

Pin 8= 0 V

Modulator

Threshold Voltage

Note 3

0.55

0.7

0.9

V <V S )

Supply Current

5

8.5

20

mA

Indicator Driver

Vsat

1.5

3

V

Leakage Current,

Pin 14 = 16 V

0.01

1

mA

Indicator Driver

Pin 17= 0 V

market

elektor june 1976 — 645

Operation in Air

Figure 4 is a circuit for an echo
sounder or distance measuring
instrument operating in air. This
is almost indentical to the circuit
of figure 2, with two exceptions.
The transmission frequency is
lowered to 40 kHz by altering LI
and C3, and the pulse length of
the internal monostablc is
extended to about 5 ps by the
circuitry around T1 (shown in
dotted box). These modifications
give a better transducer efficiency
for operation in air.

This type of circuit could be used,
as mentioned earlier, in vehicle
collision warning systems or
liquid level sensors. Other appli-
cations include intruder alarms.
The circuit would be set up so
that echoes from the area to be
protected would not trigger an
alarm, but any movement of an
intruder in the vicinity of the
transducer would cause the
reflected signal to be received
earlier. Another posibility would
be to set up the circuit so that the
received signal level from the
protected area would not trigger
the alarm. Any movement of an
intruder within this area would
alter the signal level and this
could be detected and used to
trigger an alarm. An alarm control
circuit is given in figure 6.

Literature

T. M. Frederiksen, W. M. Howard.
‘A Single-Chip Monolithic Sonar
System \ IEEE Journal of Solid-
State Circuits, December 1974,
Vol. SC9 NO. 6. pp. 394-403.

* LM1812 Ultrasonic Transceiver \
March 1975, National
Semiconductor GmbH.

National Semiconductor Limited,
The Precinct,

Broxbourne, Herts.

Automatic LCR Bridge

With this new automatic
LCR Bridge, the user need only
select the function L, C, or R -
the instrument selects the
measurement range and equivalent
circuit. Besides producing 3 , /idigit
LED readouts in capacitance,
inductance, and resistance, it also
provides readouts in D, C/D and
L/D with the accuracy of manual
bridges at rates as high as
1 reading per second. Accuracy is
typically 0,2% of reading.
Parameters of components such as
semiconductors, pulse
transformers, filter coils,
electrolytic and film capacitors,
or the internal resistance of a dry
cell can be quickly and easily
determined in production and in
the laboratory with this new
Hewlett-Packard Model 4261 A
Digital LCR Meter.

Measurements ranges are 0.1 pico-
farads to 1.900 microfarads and

0.1 microhenries to 190 henries at
1 kHz measurement frequency.
Resistance is measured from
1 milohm to 19 megohm in
8 ranges and dissipation factor
from 0.001 to 1.900. At a
measurement frequency of
1 20 Hz, capacitance can be
measured from 1 picofarad to
19 millifarads in 8 ranges;
inductance can be measured from
1 microhenry to 1900 henries in
8 ranges.

Two test signal levels, 1 volt and
50 millivolts, are available. Three
internal bias voltages or external
bias can be selected as well as
internal or external triggering. A
range hold function can be used
where a series of repetitive

measurements must be made.

In addition to autoranging, the
Model 4261 A will automatically
select the appropriate equivalent
circuit depending upon the value
of the component under test.
However the user may select a
parallel or series equivalent circuit
manually if he wishes.
Measurements arc made with the
five terminal method - easily
converted to four, three or two
terminals, depending upon the
measurement requirement and the
value of the device under test.
Three test fixtures are available
as accessories - one
direct-coupled for five terminal
measurements, a four terminal
fixture and a three terminal
fixture.

A pull-out instruction card on the
front panel is a ready reference
for measurement procedures.

Hewlett Packard, King Street
Lane, Winnersh, Workingham,
Berkshire RC1 1 5AR.

Low-cost production

A low-cost, automatic test unit
for electronic components, circuit
boards or other assemblies, with a
test capacity from 40 to 100 test
points has been introduced by
Ancom Ltd.

Designated the ‘Sentitest’
production test monitor, it
incorporates several features that
the latest experience in this field
has shown to be desirable. It is a
bench-top unit, built to a modular
construction and designed for
simple programming and ‘instant’
servicing.

Intended for use by unskilled
operators, the Sentitest is

basically an automated
multimeter, which switches its
ranges and function according to
a simple pre-set programme
requiring just the wiring-up of
resistors and diodes.

Testing can be carried out at low
signal levels to avoid damage in
the event of wiring or component
faults.

Operation is by a single
push-button with plain language,
the read-out is by go/no-go
coloured lamps, and there is an
analogue meter to help analyse
faults when required. Additional
output points are available for
data-logging or alarm purposes.

In the automatic mode it will scan
up to 100 test points in about
10 seconds; it can also be set to
re-cycle for life testing, or to
locate an intermittent fault.

In the manual mode, the test
programme is sequenced at the
operator’s own pace by pressing
the button.

A digital indicator numbers the
test points as they are scanned
and, for subsequent fault analysis,
any test point can be recalled by
dialing its number on a manual
dial.

The item under test is held by a
suitable jig, to make solderless
contact with the required test
points, on top of a box section
carrier which plugs into the top of
the test unit. The carrier contains
all the jigging and programme
logic for the particular item.
Programme changes are made
simply by interchanging carriers,
so that with a library of suitable
carriers, a single Sentitest unit can
cover a wide range of test needs
and quickly be changed from one
to another.

The test unit itself is built up
from plug-in modules comprising
a power supply, one analogue
circuit board, one logic board and
‘decade extender boards’ (DEB’s).

The basic unit incorporates one
‘master’ and four ‘slave’ DEB’s for
up to 40 test points. Capacity can
be extended in steps of ten test
points at a time by up to six more
DEB’s (i.e. a total of 100 test
points).

With the increasing acceptance of
the cost benefits of ATE within
the electronics industry, which
now extends to very sophisticated
computerised digital equipment

costing many thousands of
pounds, Ancom believes that
there is an equally growing need
for low-cost ATE.

Ancom Ltd, Denmark House,
Devonshire Street, Cheltenham,
Glos. U.K.

$ 15.00 Microprocessor

For the designer who doesn’t
really need the performance of a
general-purpose microprocessor,
a specialized unit is now available
for $ 15.00 in quantity lots.

Built by National Semiconductor,
the unit, called SC/MP (Simple
Cost-effective Applications Micro-
processor), will be good for simple
control and timing functions
usually taken care of by Random
logic.

SC/MP is expected to find
application in appliance controls,
small building security monitors,
fuel-injection units for cars as
well as traffic-signal control,
word-processing terminals and
scales and electronic toys —
’’Anything that doesn’t require
speed or too much computation”.
The 8-bit PMOS microprocessor
operates at 2 ps cycle time, it
requires a single 12-V supply,
with a comfortable margin of
± 2 V. And it generates its own
timing right on the chip, as
opposed to a need for other chips
to handle this function.

Multiple SC/MPS can communi-
cate with one another when they
all share a common bus. Logic
built on the chip allows each
SC/MP to sense when the bus is
in use. Only when one SC/MP
stops transmitting or receiving,
the one next to it can take over.

If it declines, the one adjacent to
it is given a chance.

A simple control system can be
configured using only the SC/MP
and a program memory, which
can be selected from a wide range
of standard memory parts. This
system can access up to 4 kilo-
bytes of memory to provide the
control logic for almost anything
previously controlled by sheet-
metal logic: electronic games,
small-intersection traffic control
signals, simple industrial systems,
appliances, and vending machines.
A five-chip system, composed of
the SC/MP, a two-chip bidirec-
tional transceiver, address latch,
and buffer element, can interface
to 65 kilobytes of memory for
more complex control functions,
as in credit-card verification,
business and accounting machines,
text-editing typewriters,
intelligent stand-alone terminals,
and measurement systems.

National Semiconductor GmbH
D 808 Furstenfeldbruck
Industriestrafie 10
West Germany

646 — elektor june 1976

market

AD2700 10 VOLT REFERENCE

FINE FINE TEST

ADJUST 10V ADJUST 15V POINT

® © © © ® (9) (5)

© ® © @ ® © ®

COMMON

ANALOG DEVICES' AD2700 10.000 0.001V REFERENCE FEATURES
LOW PRICE AND *0.03% MAXIMUM OUTPUT ERROR AT +70 C

Synthesized signal
generator

A new synthesized microwave
signal generator, Model 8672A
from Hewlett-Packard, covers
the range 2 to 18 GHz in one
solidstatc package only 5 1/4”
high. With AM/FM and calibrated
output usually associated only
with signal generators, 8672A
also offers the resolution, spectral
purity, stability, and pro-
grammability of a high-quality
synthesizer. Yet its price is well
below equipment commonly
used in the past to synthesize
microwave signals over com-
parable ranges. A companion
instrument, Model 8671 A, covers
the range 2 to 6 GHz with FM
capability only. Both machines
arc programmable via the HP
Interface Bus.

Frequency resolution of the
8672A is 1 kHz in the range
from 2 to 6.2 GHz, 2 kHz from
612 to 12.4 GHz, and 3 kHz
above 12.4. Frequency stability
is better than ± 5 in 10 1 0 parts
per day with the internal fre-
quency standard. Spurious
signals are more than 70 dB
below the carrier at 6 GHz,
more than 60 dB down at
18 GHz. Single-sideband phase
noise (in a 1-Hz bandwidth) is
more than 78 dBc 1 kHz away
from a 6-GHz carrier; 100 kHz
away, it’s -109 dBc. Calibrated
output is from +3 to -120 dBm;
attenuation is displayed digitally
on an LED readout. In overrange,
power levels to +10 dBm are
typically available below 6.2 GHz,
and to +7 dBm at other fre-
quencies. Power can be internally
leveled ± 1.25 dB; connections
are provided for leveling
externally.

Modulation signals are externally
supplied but internally moni-
tored. AM 3-dB bandwidth is
more than 500 kHz at 6 GHz,
more than 100 kHz at 18 GHz.
AM depth is selectable in two
ranges, 30% per volt and 100%
per volt, controlled linearly by
varying the input signal. FM input
rates to 10 MHz are possible up
to peak deviations of 10 MHz. Six

ranges of peak deviation are
offered, from 30 kHz per volt to
10 MHz per volt of input. Peak
deviation may also be displayed
on the front panel meter. FM and
AM are entirely independent, and
may be applied simultaneously.
Without exception, all front panel
controls arc remotely pro-
grammable. Frequency changes
typically settle within 1 kHz of
command in less than 15 milli-
seconds. RF output can be
programmed over its full ampli-
tude range in 1-dB steps as well
as OFF (without unpowering
the instrument). AM or FM, or
both at once, may be remotely
applied.

The lower-priced 8671 A has the
same spectral-purity, resolution,
and switching-speed performance
as the 867 2A; it is likewise
totally programmable via the HP-
IB, and it has the same FM specs.
8671 A lacks AM capability, out-
put levelling, and calibrated out-
put attenuator. Its frequency
range is 2 to 6.2 GHz.

First customer deliveries are
expected in June.

Hewlett Packard
7, rue du Bois-du-Lan,

P.O. Box 349 ,

CH-121 7 Meyrin 1 Geneva ,
Switzerland

Precision Voltage
References

Analog Devices Ltd., announce
the availability of a new ± 10 V
and -10 V precision voltage
reference, together with an im-
proved performance version of
the recently introduced 10 V
reference. Designated AD2702,
AD2701 and AD2700/L, respect-
ively, the new units are ideally
suitable for application in 12-bit
A/D and D/A converter circuits,
combining high performance
thin-film technology, automatic
laser trimming and volume
hybrid assembly, with small size
and hermetically scaled 3-terminal
terminal references.

Designed to now operate over the
extended temperature range of
-55°C to 1 25°C, AD2700/L

features ± 0.03% total maximum
error guaranteed from -25°C to
85°C, and load regulation over
the 0 to 20 mA range of ± 0.004%.
Military versions - AD2700/U
and AD2700U/883 - feature
screening to MIL-STD-883A,
5004.2, Class B, ans +0.03%,
-0.05% total maximum error
over the full -55°C to 125°C
temperature range.

The new Analog Devices AD2701
and AD2702 offer identical
specifications to the AD2700 but
having -10 V and ± 10 V ouputs,
respectively.

Available in 14-pin DIP packages,
AD2700/L, AD2701 and
AD2702, each feature an accu-
racy to within ± 0.001 V and
minmize voltage noise (0.1 to
10 Hz) to below 50 m Vp-p.
Maximum output current is
20 mA and short circuit protec-
tion is provided.

Analog Devices Ltd.,

Central A venue,

East Molesey,

Surrey. 01-941 0466

High Sensitivity
Microphones

Two new Vi" Measuring
Condenser Microphones with
improved sensitivity have been
developed by Briiel & Kjaer.

These microphones have the same
sensitivity as 1” condenser micro-
phones. Both are intended for
general and low level sound
measurements and are delivered
with individual calibration chart.
The 4165 is a free-field micro-
phone with a linear 0° incidence
frequency response from 4 Hz
to 18 kHz ± 1 dB and a sensi-
tivity of 50 mV/Pa. It fulfils the
requirements to microphones in
ILC R 123, IEC R 179 and ANSI
S 1 .4-1971, Types 2 and 3.

The 4166 has a linear random
incidence frequency response
from 4 Hz to 8 kHz ± 1 dB and a

sensitivity of 50 mV/Pa. It fulfils
the requirements to microphones
in ANSI S 1.4-1971, Types 1,2
and 3.

Briiel & Kjaer
23 Linde a lid

DK-2850 Naerum Denmark

Burglar Alarm

ANTEX has launched what is
believed to be the first D.I.Y.
burglar alarm kit which complies
with the strict standards of
B.S.4737.

The illustration shows the control
box of the battery-operated
version (Model A 1 B). The mains-
operated Model A 1 MB is suit-
able for the average 3-bedroomed
house.

The electronic circuitry which
provides the owner with a variety
of useful facilities is housed in a
strong, tamper-proof steel box.
Special precautions were taken to
prevent false alarms, the bane of
so may alarm systems.

ANTEX Ltd.,

Mayflower House,

Plymouth, Devon.

market

elektor june 1976 — 647

Audible warning modules

Roxburgh Electronics Ltd have
released a scries of micro-
electronic buzzers capable of
providing audio frequency
outputs in excess of 90 dB at
20 cm. lliey have been designed
for case of installation, and for
direct connection to associated
integrated circuitry.

'Hie SMB series, which requires a
power supply of 1.5Vd.c., and
the MB series, which operate
from 3 V, 6 V or 1 2Vd.c., each

provide a continuous alarm out-
put. The MBF series is available
for applications requiring an
intermittent alarm, and operates
from 6 V or 12Vd.c.
niese two ranges are comp-
lemented by the RMB-24 series,
which operates from a power
supply between 20Vd.c. and
28Vd.c., and similarly provides
an audio frequency output
exceeding 90 dB at 20 cm.

Roxburgh Electronics Ltd ,

22 Winch el sea Road,

Rye, Sussex

Memories that plug in

For small- and medium-scale data
systems Siemens is now supplying
two memories designed for word
lengths of 4 bits and 8 bits. These
semiconductor memories are
mounted on Euroboards fitted
with plug connectors and are
arganized on the 4K by 4 bit
(static) and 8K by 8 bit (dynamic)
7asis. Bit prices of .55 p for the
16K memory and .3 p for the
54K memory make th«*se plug-in
memory systems a good choice
for such equipment as point-of-
sales terminals, data display
terminals, metering and regu-
lation systems and particularly
microprocessors of all kinds.

Hie 4K by 4 bit matrix of the
mialler memory system is con-
structed from 16 static IK MOS
RAMs of the SAB 2102 type.

\ start pulse and two control
levels (address mode, read-write)
Are used as control signals. So as
not to overload the address lines
capacitively, a register is provided
for driving the memory with only
Arief information (around 150 ns),
riie cycle and access times are
1.10 ms and 1.05 ms respectively,
lob control, input and output
'egisters and a decoder complete

the memory system, which is
plugged in via a 31 -point pin
connector.

The memory section of the 8K by
8 bit system comprises
16 dynamic 4K MOS RAMs of
the HYB 4060 type each with a
capacity of 4096 bits. The total
capacity is thus organized into
8192 words by 8 bits. Due to the
dynamic character of the
modules, one of the 64 rows in
each of the memory modules is
automatically refreshed at
intervals of 32 ms. During these
refresh periods no operating
cycles are performed by the
memory; any signals that arrive
are buffered. The cycle and access
times are 650 ns and 450 ns
respectively. All input and output
signals transmitted via the
60-point plug connector arc TTL-
compatible as with the 4K x 4 bit
system.

Monolithic 16K memories arc no
longer dreams of the future, 64 K
memories will not be long in
coming either. Nevertheless,
there will always be certain cases
where such memory capacities
are best built up from several
individual modules on a discrete
basis. With such systems, word
lengths consisting of several bits
can also be processed directly, if
the appropriate number of indivi-
dual memories are connected in
parallel. The total memory
capacity of 16K is then the result
of 4K by 4 bit (8K by 8 bit for
64K). If a 16K single-chip
memory were used, a word length
of, for example, 4 bits would fix
the capacity at a minimum of
64K, but this represents a
capacity in excess of that required
for most of the envisaged appli-
cations. Quite apart from this,
the distribution of a capacity
among several chips on a plug-in

board offers advantages with
regard to manufacture and
operation.

Siemens A G,

Zentralstelle fur Information,
D-8520 Erlangen 2,

Postfach 3240,

West Germany

Safer wafer breaker

Using a patented technique, the
WB610 actually separates chip
segments after the first and prior

to the second break in the scribed
wafer. This exclusive feature
reduces chip damage to a
minimum.

First step in operating the WB610
wafer breaker is the application
of an adhesive film to the back
of the scribed wafer. The film-
backed wafer is placed on the
unit's break table and properly

aligned. After pressure and speed
have been adjusted to the correct
level, the breaker roller is passed
over the wafer.

The first break having been
completed, the break table is
rotated by 90°. Then, the wafer
is stretched slightly on the film,
thereby separating the chip seg-
ments. The final step is passing
the roller over the separated chip
segments to complete the second
break.

With other wafer-breaking
techniques most chip damages
occurs during the second break.
Because of its exclusive chip
separation feature, the WB610
eliminates the major cause of
damage by separating chips before
the second break.

When operated properly, the
machine should reduce chip loss
by as much as 40 to 60 per cent
of normal.

Laurier Associates, Inc.,

Executive Drive, Hudson,

N. H. 03051

Cesium standard

The Hewlett-Packard 5062C
Cesium Beam Frequency Standard
offers both the precision of the
best lab standard with the
ruggedness of military hardware
in a compact package. It maintains
3 x 10" n accuracy over a wide
operating temperature range and
requires only 20 minutes of
warm-up time even from — 28°C.
Operating temperature range:
-28°C to +65°C. Ruggedness:

passed the 400-lb hammer blow
test under operating conditions.
With a calculated MTBF of
25,000+ hours, the 5062C is
highly serviceable. Twelve critical

circuits are monitored by the
front panel meter. The unit is
5% "high and will fit into a
standard 19" rack. The basic
5062C weighs 50 lbs.

This new frequency standard is
ideally suitable for navigation,
communication, guidance
systems, among other on-line
system applications where high
performance in field environments
is required.

Optional digital display clock and
standby battery available at extra
cost.

Basic unit costs around £ 10,000.

Hewlett Packard, King street lane,
GB- Winnersh,

Wokingham RG1 1 5AR,

Berkshire

Troposcatter amplifier

MPD announces the availability of
a 250 W solid state Tropo
amplifier operating in the fre-
quency range 755-985 MHz. The
Model PWA7598-25 1/2726
delivers 250 W cw saturated
power with an input power level
of 0.5 W. The amplifier is
essentially transparent to NPR
noise loading.

Applications for this amplifier is
as a troposcatter transmitter on
off-shore oil riggs such as those
located in the North Sea, the
Persian Gulf and any place else
where troposcatter over-the-
horizon communications are
utilized.

Features of the amplifier include
circulator protected output for

load protection against open or
short circuits, B + reversal
protection, thermal overload
protection, and the unit also has
alarms (visual and remote) for
RF input failure and low power
output reduction. The unit comes
with built-in test equipment
(BITE) to determine if an RF
transistor has failed.

Specifications:

Frequency range: 755-985 MHz
Bandwidth: 230 MHz @ 1 dB

Power output (50 f2):

250 W cw saturated
RF input range: 0. 5-3.5 W

Input VSWR: 2 : 1

Load VSWR: Circulator protected
Harmonics: —30 dB minimum

Microwave Power Devices, Inc.
Adams Court, Plain view,

N.Y. 11803

648 — elektor june 1976

market

advertisement

Digital Cavity Wavemeter

Baytron Company, Inc. manufac-
turers and developers of milli-
meter wave components and
systems, is proud to introduce the
most dcstinctive contribution to
waveguide passive device tech-

nology in a decade-direct reading
digital cavity wavemeter.

direct reading up to
40 kV

The latest high-voltage meter
from Brandenburg Limited, the
Model 109M, offers direct reading
of e.h.t. voltages up to 40 kV.

The instrument’s very high
impedance of 60 Gf2 means that
the current drain on the circuit
under test is very small. This
gives the meter a significant
advantage over conventional
multimeters which can draw as
much as 50 m A, thereby reducing
the voltage under test. The
instrument’s rugged construction
makes it ideal for routine
measurements taken, for example,
during cathode-ray-tube servicing.

Some of the features of this
device are as follows:

Digital readout - 8 mm LED
characters; high resolution -
1 MHz; accuracy - 0.06% absol-
ute error; excellent repeatability
— zero backlash; and no spurious;
resonances - TM 110 and TM 0 io
modes eliminated.

The Wavemeter will carry the part
number 10E-49 followed by
BAYTRONS ‘band’ designation,
eg. Ka thru D. The digital pro-
cessor and readout is always

included in the package consisting
of the two devices. These devices
range in price from under $ 4,000
to over $ 10,000. It is suggested
to order as soon as possible since
demand has accounted for much
of the first years production.
Delivery is 20 weeks frofn date of
order.

Reine Electronics B. V.,

Postbus 6 730,

Den Haag 2040,

The Netherlands.

The instrument uses the latest
semiconductor operational
amplifiers to give a readout with
a linear mirror scale, with div-
isions of 1 kV. The instrument is
battery operated, and incorpor-
ates a battery test facility; battery
life is 600 h. The high-voltage
probe, with a special attachment
for c.r.t. measurements, is
available as an accessory.

The model 109M costs £ 100
(plus V.A.T.) and the probe £ 5
(plus V.A.T.).

Brandenburg Limited,

High - Voltage Engineering
Division,

939, London Road,

Thornton Heath,

Surrey. CR4 6JE.

Model number

Operating

Suggested list

cavity &

frequency-

price F.O.B.

processor

GHz

fact

10E-49 Ka

26.5- 40.0

$ 3,650.00

10E-49 B

33.0- 50.0

$ 3,950.00

10E-49 Q

40.0- 60.0

S 4,225.00

10E-49 V

50.0- 75.0

$ 4,500.00

10E-49 E

60.0- 90.0

$ 5,050.00

10E-49 R

75.0-110.0

$ 5,625.00

10E-49 N

90.0-140.0

S 6,475.00

10E-49 T

110.0-170.0

$ 7,325.00

10E-49 G

140.0-220.0

$ 8,450.00

10E-49 Y

170.0-260.0

$ 9,850.00

10E-49 D

220.0-325.0

$ 11,250.00

Will be exhibiting a variety of working projects
selected from current and future issues of
ELEKTOR Magazine at

The International Home
Electronics & Domestic

Appliances Exhibition 23-27 may

plus

The Public Show

Sound & Vision’76 28-31 may

national exhibition centre, Birmingham

( ha! no 3
V Stand no 5015

ITS

CONNOISSEUR

5C09

ioi5

Back numbers of Elektor magazine and our own printed circuit
boards will be available. Our editorial and advertising staff look
forward to meeting you there.

DECCA

.on

ELEKTOR PUBLISHERS LTD.

6 Stour Street, Canterbury, CT1 2XZ.

Tel: 0227 - 54430 - Telex: 965504

advertisement

elektor june 1976 — 649

CHINAGLIA DINO - ELECTRICAL AND ELECTRONIC TEST EQUIPMENT MANUFACTURERS

CHINAGLIA

PRESENT THE

DOLOMITI

20 kft/V a.c. and d.c.

A NEW HIGH SENSITIVITY MULTIMETER
WITH ALL THE FEATURES YOU WILL EVER NEED

Accuracy: D.C. ranges, ±2.0%, A.C. & H ranges ±2.5%.

39 ranges: d.c. V, 0-1 50 mV, 500 mV, 1 .5 V, 5 V, 15 V, 50 V, 150 V, 500 V,
1 .5 kV; d.c. I, 0-50 ^A, 500 fi A, 5 mA, 50 mA, 0.5 A, 5 A; a.c. V,
5 V, 15 V, 50 V, 1 50 V, 500 V, 1.5 kV; a.c. I, 5 mA, 50 mA, 0.5 A,
5 A; dB —10 to +65 in 6 ranges; £1 0-0.5 kl2, 5 kH, 50 k£2, 500 kH,
5 MJ2, 50 MH; pF 50 kpF, 500 kpF.

Automatic overlaod protection and high current range fusing.

Scale mirror and fine pointer for accuracy of reading. Single knob main range
switching and all panel controls. C.E.I. Class 1 movement with sprung jewel
bearings. Extended 92 mm scale length for extra clarity. Compact ABS case
125 x 131 x 37 mm. Weight 650 g with batteries. Supplied complete with
carrying case, fused leads, handbook and full 12-month guarantee. Optional
30 kV d.c. probe available.

Meter £ 33.15 incl. VAT (80p P. & P.)
30 kV Probe £ 10.80 incl. VAT

For details of this and the many other exciting
instruments in the Chinaglia range, including
multimeters, component measuring, automotive
and electronic instruments please write or tele-
phone.

Instruments Ltd.

19 MULBERRY WALK • LONDON SW3 6DZ TEL.: 01-352 1997

babani press

new to elektor from babani

0 >^°

^ 0 &

0 ?

O 9

A®

O FIRST BOOK OF TRANSISTOR EQUIVALENTS & SUBSTITUTES

A handbook containing 73 pages of transistor equivalents and
substitutes including British, German, Dutch, USA, Japanese
and European manufacture 40 p

O SECOND BOOK OF TRANSISTOR EQUIVALENTS & SUBSTITUTES

Complementary to the first book with over 56,000 additional
equivalents and substitutes covering virtually all known types
at time of publishing 95 p

O HANDBOOK OF INTEGRATED CIRCUITS (IC's) EQUIVALENTS

& SUBSTITUTES

115 pages of most available types of integrated circuits which
have equivalents or substitutes 75 p

O PRACTICAL ELECTRONIC SCIENCE PROJECTS

12 construction projects including Electroscope, Gieger radiation
counter. Digital clock etc. with circuit diagram & parts lists 75 p

o PRACTICAL STEREO AND QUADRAPHONY HANDBOOK

Stereo recording, 10 plus 10 stereo amplifier, Quadrasonic
reproduction etc. are detailed in its 90 pages 75 p

If you do not wish to spoil your copy of Elektor please make a note of
the books you require with your name and address and send it to us
with'your remittance.

further paperbacks now available

O PRACTICAL ELECTRONIC PROJECTS

A selection of construction projects with circuit diagrams and
parts lists including a simple to build, portable radio receiver,

21 watt amplifier for guitars and a simple tester for Digital ICs ...

O 79 ELECTRONIC NOVELTY CIRCUITS

Circuits include Burglar alarms. Reaction tester game. Wide range
frequency doubler. Simple capacitance and Transistor tester.
Intercom and signalling device etc. etc.

Interchangeabilities and equivalents of solid state devices used
are also given

O WORLDS SHORT MEDIUM & LONG WAVE FM & TV BROAD-
CASTING STATIONS LISTING

91 pages of lists giving station, country, KC/S and KW ratings

O THE COMPLETE CAR RADIO MANUAL

Includes the selections of a radio and its installation, aerials,
suppression and fault finding 90 pages

Q MODERN TAPE RECORDING HANDBOOK

Covers microphones, sound effects, tunes and editing, fault

finding etc. contained in its 91 pages 75 p

O DIODE CHARACTERISTICS EQUIVALENTS & SUBSTITUTES

European. USA, Asian, Japanese, USSR and Military service
types etc. including rectifiers and zener diodes. 25000 entries
with index in 9 languages, over 1 50 pages 95 p

O RADIO TV AND ELECTRONICS DATA BOOK

Over 90 pages of facts and figures including wavelengths and
frequency tables. International morse code, the Q code. Resist-
ance wire data and many others 60 p

O RADIO TV INDUSTRIAL & TRANSMITTING TUBE & VALVE
EQUIVALENTS

Handbook of equivalents, British, European and USA desig-
nations of valves, CRT's and tubes. New system pro-electron

CRT's tubes etc. etc 60 p

Please send me (tick box)

I enclose remittance of for the books and 20 p post and

packing.

Name .

Address

75 p

75 p

60 p

75 p

Postcode

650 — elektor june 1976

advertisement

15 TUP

I5TUN

JC

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C

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5

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□

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advertisement

elektor june 1976 — 651

cylinde

andteisu^

^Tp.ctronjcs

IC5

1 Q

1/2 7473

Clock

Clear

K

_L_

|2

I 3

ELEKTOR BACK
ISSUES ARE
STILL AVAILABLE

This is a selection from the contents of the
various issues:

number 1:

— tup-tun-dug*dus

— equa amplifier

— mos clock

— distortion meter

— tap sensor

— electronic loudspeaker

— steam whistle

number 2:

— minidrum

— universal display

— dil led probe

— tv sound

— big ben

— modulation systems

— how to gyrate

number 3:

— tap preamp

— pll systems

— fido

— time machine

— compressor

— disc preamp

— a/d converter

— led displays

number 4:

— tup-tun tester

— interference suppression
in cars

— thief suppression in cars

— supplies for cars

— cybernetic beetle

— the moth

— quadro in practice

number 5:

'Summer Circuits' issue, with
over 100 circuits: amplifiers,
generators, dividers, universal
frequency reference, im-
proved 7-segment display,
receivers, power supplies,
rhythm generators, measuring
equipment, etc.

Prices for single copies:

1 to 4 and 6 to 8 —

number 5 —

from number 9 —

(prices include p & p)

U.K. and overseas
surface mail

50 p
85 p
55 p

overseas air mail

00220 038

— Axe 1 IC4

74121

.

s'

■ • ••

•V

y.

ffl

■

m

■ ■

■■■■

lab

and leisur*

m

..'a

"

4C6

,<ir

watch

Oder

' 2 )

if

PpEg

9343

a** ^

Poiaro«d«

85 p

110 p

90 p

number 6

— edwin amplifier

— versitale digital clock

— phasing

— disco lights

— ota

— dual slope dvm

— car clock

numbers 7 and 8

sold out

numoer 9

— feedback pll for fm

— function generator

— racing car control

— simple mw receiver

— digital master oscillator

— pll-ic stereo decoder

number 10

— call sign generator

— morse decoder

— speech processor

— morse typewriter

— digital wrist watch

number 11

— tv tennis extensions

— ssb receiver

— tv sound front-end
adapter

— dynamic noise limiter

— integrated voltage
regulators

number 12

— preco

— ic rhythm generator

— Polaroid timer

— led meters

— stylus balance

number 13

— integrated indoor fm
aerial

— equin (2)

— digisplay

— versatile logic probe

652 — elektor june 1976

advertisement

BDXIM CKDM*

BEGINNERS' GUIDE TO ELECTRONICS

T. L. Squires £2.55

A short cut for those wishing to obtain a quick aquaintance with
modern electronics

I.C. OP-AMP COOKBOOK

£8.15

Covers'*! he basic theory of 1C OP Amp in great detail, also includes

“ ilTu

W. J. Jong
Covers the

250 practical circuit applications liberally illustrated

TTL COOKBOOK

□ .Lancaster £5.80

Complete and detailed guide to TTL. how it works, how to use it
and practical applications

110 OPERATIONAL AMPLIFIER PROJ-
ECTS FOR THE HOME CONSTRUCTOR

R.M.Marston £2.85

Outlines the essential characteristics of the OP-Amp and presents
1 10 useful protects.

110 SEMICONDUCTOR PROJECTS FOR
THE HOME CONSTRUCTOR

R.M.Marston £2.85

This book introduces the reader to useful new devices such as the
FET. SCR and 1C. with full constructional details of.many useful
circuits.

UNDERSTANDING CMOS INTEGRATED
CIRCUITS

R.Molen £3.25

Begins with basic digital ICs, covers semiconductor physics. CMOS
fabrication technology and design.

INTEGRATED ELECTRONICS

J.Millman £5.00

Using an integrated circuits approach this text leads the reader step
by step from semiconductor physics to devices, models, circuits and
systems

LINEAR PRINCIPLES EXPERIMENTS
AND PROJECTS

E. M. Noll £5.80

An introduction to one of electromc’s most exciting devices.

DESIGNING WITH TTL INTEGRATED
CIRCUITS

Texas Instruments £5.55

Covers the entire family of TTL and practical applications of the
circuits in digital systems.

OPERATIONAL AMPLIFIERS DESIGN
AND APPLICATION

G. Tobey (Burr-Brown) ^ 4.70

Completely up to date, this work covers the entire field of oper-
ational amplifiers.

BEGINNERS' GUIDE TO TRANSISTORS

J. A. Reddihough £2.55

TV SERVICE HANDBOOK

G. King £ 5.00

Thoroughly practical handbook, deals in detail with modem re-
ceivers.

COLOUR TELEVISION SERVICING

G. King £ 5.90

A practical handbook, dealing with all modern receivers

MAZDA BOOK OF PAL RECEIVER
SERVICING

O. Seal £ 5.30

A practical handbook with over 200 illustrations

THE OSCILLOSCOPE

G. 2 wick £2.10

Starts from the first principles and takes the reader to an advanced
level.

HOW TO USE VECTORSCOPES OSCILLO-
SCOPES AND SWEEP SIGNAL GENER-
ATORS

S. Premises ^ ^

It goes into the whole subject deeply, in 250 heavy illustrated pages.

99 WAYS TO USE YOUR OSCILLOSCOPE

A. Saunders £ 1.80

□escribes how to solve practical problems using a scope

WORKING WITH THE OSCILLOSCOPE

A. Saunders ^ ^ .85

A book devoted to circuits and illustrations of waveforms that
should be present.

HOW TO USE YOUR VOM VTVM AND
OSCILLOSCOPE

M. Clifford ^ 1 *80

This book aims to give you knowledge and help you perform a wide
variety of essential tests on many different kinds of sets, appliances
and equipment.

ELECTRONICS SELF-TAUGHT WITH

EXPERIMENTS AND PROJECTS

J. Ashe ^ 2.20

Covers basic principles of electronics Projects include a large
number of simple circuits.

LOGIC CIRCUITS

N. M. Morris £3.10

Aids the understanding of logical problems, discusses principles
including integrated circuits.

AMATEUR

ELEC-

INTRODUCING
TRONICS

, _ .. , , £ 1.60

I. R. Sinclair

The book for the complete novice of any ago, as no pievious knowl
edge is assumed.

ELECTRONICS MUSICAL INSTRUMENTS

N.Crowhurst £2.05

This book looks at the fascinating subject of electronic music from
almost every angle.

EXPERIMENTING WITH ELECTRONIC
MUSIC

R. Brown and M. Olsen “ *

Practical Experiments offer scope for originality and research.

BASIC MATHS COURSE FOR ELEC-
TRONICS

H. Jacobowitz £ 1.70

Ohms Law and all maths for electronics written in an easy, under-
standable way.

ELECTRONICS UNRAVELLED

J. Kyle £2.20

A new commonsense approach to the basic principles of electronics.

DIGITAL ELECTRONIC CIRCUITS AND
SYSTEMS

N.M. Morris £2.60

The ideal book for the enthusiast confused by logic and digital
techniques.

INDUSTRIAL ELECTRONICS

N.M. Morns £3.20

The book concentrates mainly on semiconductor devices and circuits
solutions to the many numerical problems are given, S I. units are
used throughout.

HOW TO BUILD ELECTRONICS KITS
V.Capel £2.10

Instructs the reader on how to check components, how to assemble
and how to cure faults.

FOUNDATIONS OF WIRELESS AND
ELECTRONICS

MN. G. Scroggie £ 4.25

Ninth edition of this ever popular basic theory book which starts
from scratch.

RADIO, VALVE & SEMI-CONDUCTOR
DATA

A. M. Ball £2.50

Tenth edition, gives data on 1.000 valves and CRTs. 9,800 transis-
tors, diodes, rectifiers and optical devices.

All prices include Postage and Packing.

To: Technical Book Services Ltd, Dept. E,
25 Court Close, Bray, Maidenhead,
Berks. SL6 2DL

TTLs by

7486 32p

C-MOS ICs

TEXAS

7489 291p

4000

19p

7400

13p

7490 43p

4001

19p

7401

15p

7491 81p

4002

19p

7402

15p

7492 48p

4007

19p

7403

17p

7493 43p

4009

67p

7404

17p

7494 81 p

4011

19p

7405

17p

7495 7 Op

4012

19p

7406

41p

7496 84 p

4013

55p

7407

39p

7497 29 Ip

4016

54p

7408

17p

74100 116p

4017

123p

7409

22p

74107 32p

4018

247p

7410

15p

74110 55p

4020

27 Op

7411

24p

74118 9 Op

4022

180p

7412

25p

74121 32p

4023

19p

7413

34p

74122 62p

4024

125p

7414

65p

74123 73p

4025

19p

7416

32p

74126 75p

4026

200p

7417

32p

74132 75p

4027

81 p

7420

15p

74136 81p

4028

152p

7421

43p

74141 7 Op

4029

189p

7422

19p

74145 75p

4030

59p

7423

36 p

74148 173p

4042

150p

7425

33p

741 50 135p

4043

218p

7427

40p

74151 77p

4046

150p

7428

39p

74153 92p

4047

168p

7430

15p

74154 164p

4049

68p

7432

28p

74155 82p

4054

210p

7437

28p

74156 82p

4055

21 Op

7440

15p

74160 107p

4056

145p

7441

7 Op

74161 107p

4060

250p

7442

64p

74162 107p

4069

40p

7443

1 16p

74163 107p

4071

29p

7444

1 16p

74164 130p

4072

29p

7445

81p

74166 136p

4081

19p

7446

75p

74174 131p

4082

29p

7447

81p

74175 92p

4510

142p

7448

75p

741 76 131p

451 1

200p

7451

17p

74177 108p

4518

108p

7453

17p

74180 108p

4528

130p

7454

18p

74181 322p

7460

16p

74182 89p

TEXAS

7470

29p

74185 146p

75 series

7472

27p

74190 155p

75107

175p

7473

32p

74191 156p

75450

120p

7474

48 p

74192 130p

75451

78p

7476

32p

74193 130p

75452

78p

7480

54p

74194 116p

75453

78p

7481

103p

74195 83p

75454

78p

7482

75p

74196 99p

7483

85p

74197 108p

MULLARD

7484

103p

74198 214p

MODULE

7485

130p

74199 197p

LP1 186 810p

VOLTAGE REGULATORS

Fixed-Plastic 3 Terminals

1 Amp

+ve

-Ve

5 V

7805

150p

7905

21 5p

12 V

7812

150p

7912

215p

15 V

7812

150p

7915

215p

18 V

7818

150p

7918

215p

24 V

7824

150p

7924

215p

LM309K

5 V

1 Amp

T03

150p

VARIABLE

723 14pin OIL 45p

LOW PROFILE OIL SKTS BY TEXAS
8 pin 14p 16 pin 16p

14 pin 15p 24 pin 54p

OP.AMPS

301 A Ext. Comp. 8pinDIL 40p

536T FET Op.Amp. TO 99 300p

709 Ext. Comp. 8/14 pin OIL 30p

741 Int. Comp. 8/14 pin OIL 25p

747 Dual 741 14 pin OIL 70p

748 Ext. Comp. 8/14 pin DIL 40p

776 Prog. Op.Amp. TO 99 160p

1458 Dual Op.Amp. 8 pin DIL 70p

3130 CMOS Op.Amp. 8 pin DIL 108p

3900 Quad. Op.Amp. 14 pin DIL 60p

LINEAR I.C4

CA3028A

Dill. Cascade Amp.

T099

1 12p

CA3046

5 Transistor Array

14 pin DIL

55p

CA3048

4 Lo Noisa Amp.

16 pin DIL 250p

CA3053

Diff.Cascade Amp.

T05/DIL

55p

CA3089E

FM IF System

16 pin DIL 250p

CA3090AQ

FM Stereo Decoder OIL

500p

ICL8038CC

VCO Fun. Gen.

16 pin DIL 300p

LM380N

2 W Audio Amp.

14 pin DIL 115p

LM381N

Stereo Pre Amp.

14 pin DIL 200p

M252

Rhythm Generator

16 pin DILIOOOp

MC1310P

FM Stereo Decoder

14 pin DIL 220p

MFC4000B

*iW Audio Amp.

PCB

75p

MFC6040

Electronic

Attenuator

PCB

140p

NE555V

Timer

8 pin DIL

40p

NE556

Dual 555

14 pin DIL 108p

NE561B

PLL with

AM Demod.

16 pin DIL 350p

NE562B

PLL with VCO

16 pin DIL 350p

NE565

PLL

14 pin DIL 200p

NE566V

PLL Fun. Gen.

8 pin DIL

ieop

NE567V

PLL Tone Decoder

8 pin DIL

200p

2567

Dual 567

16 pin DIL 400p

SN72710

Diff. Comparator

14 pin DIL

54p

SN72733

Video Amp.

14 pin DIL 150p

SN76013N

Audio Pwr. Amp.

with int. HS

OIL

175p

SN76023N

Audio Pwr. Amp.

with int. HS

OIL

175p

TAA661B

FM/IF Amp.

Lim/Dct.

OIL

15 Op

TBA641B

Audio Amp.

OIL

300p

TBA800

5 W Audio Amp.

OIL

1 12p

TBA810

7 W Audio Amp.

OIL

125p

TBA820

2 W Audio Amp.

OIL

lOOp

TDA2020

20 W Audio Amp.

OIL

375p

XR2240

Prog. Timer/

Counter

16 pin Dl L

400p

ZN414

TRF Radio

Receiver

T018

140p

OPTOELECTRONICS

PHOTO-TRANSISTORS

LEDS

OCP70

33p

TIL209 Red

15p

OCP71

12 Op

TIL211 Green

32p

2N5777

43p

TIL 32 Infrared

81 p

LDRs

0.2”

ORP12

60p

Red

17p

ORP60

75p

Green

29 p

ORP61

75p

Yellow

32p

SEVEN SEGMENT DISPLAYS

3015F

1 30p

DL707

160p

DL704

16 Op

DL747

250p

OPTO-ISOLATORS

TIL112 IIL12)

151p

ILCA55

27 Op

ORIVERS

75491

78p

75492

97p

TRANSIS-

TORS

AC127

13p

AC128

12p

AC176

12p

AC187

14p

AC 188

14p

AD149

46 p

AD161

39p

AD162

39p

AF115

18p

AF116

18p

AF117

18p

AF139

35p

AF239

43p

BC107

lOp

BC108

lOp

BC109

Up

BC147

9p

BC148

9p

BC149

lOp

BC157

Up

BC158

13p

BC159

13p

BC169C

15p

BC171

12p

BC172

Up

BC173

13p

BC177

20p

BC178

17p

BC179

20p

BC182

12p

BC183

12p

BC184

14p

BC187

32p

BC212

14p

BC213

12p

BC214

17p

BC478

32p

BCY70

20p

BCY71

24p

BD124

7 Op

BD131

39p

BD132

43p

BD135

54p

BD136

55p

BD139

79p

BD140

87p

BF115

24 p

BF 167

2Sp

BF173

27p

BF 1 78

30p

BF 194

13p

BF 195

lip

BF 196

17p

BF 197

19p

BF200

40p

BF257

34p

BF258

39p

BFR30

37p

BFR40

37p

BFR79

37p

BFR80

37p

BFR88

37p

BFX30

32p

BFX84

28p

BFX85

27p

BFX86

28p

BFX87

22p

BFX88

26p

BFY50

17p

BFY51

IGp

BFY52

17p

BRY39

39p

BSX19

20p

BSX20

20p

BU105

175p

BU108

312p

MJE340

49p

MJ2955

Sip

MJE2955 107p

MJE3055

70p

MPSA06

37p

MPSA12

62p

MPSU06

78p

MPSU56

98p

OC28

70p

OC35

70p

OC71

25p

TIP29A

50p

TIP29C

62p

TIP30A

GOp

TIP30C

72p

TIP31A

5Gp

TIP31C

GOp

TIP32A

63p

TIP32C

85p

TIP33A

97p

TIP33C

1 20p

TIP34A

124p

TIP34C

IGOp

TIP35A

243p

TIP35C

290p

TIP36A

297p

TIP36C

3G0p

TIP41A

70p

TIP42A

7Gp

TIP2955

7Gp

ZTX108

Up

ZTX300

16p

ZTX500

19p

ZTX504

GOp

2N697

14p

2N698

32p

2N706

13p

2N708

19p

2N918

43p

2N930

19p

2N1131

19p

2N1132

19p

2N1304

23p

2N1305

23p

2N1306

30p

2N1613

22p

2N1711

22 P

2N1893

32p

2N2219

22p

2N2222

22p

2N2369

15p

2N2484

32p

2N2904

22p

2N2905

22p

2N2906

22p

2N2926RB 9p

2N29260G1 Ip

2N3053

19p

2N3054

43p

2N3055

54p

2N3442

151p

2N3702

14p

2N3703

14p

2N3704

14p

2N3705

14p

2N3706

12p

2N3708

lip

2N3709

Up

2N3707

14p

2N3773

240p

2N3866

9 Op

2N3904

22p

2N3905

22p

2N3906

22p

2N4058

19p

2N4060

19p

2N4123

22p

2N4124

22p

2N4125

22p

2N4126

22p

2N4371

142p

2N4348

173p

2N4401

34p

2N4403

34p

2N5089

34p

2N5401

62p

40360

43p

40361

41p

40362

43p

40410

59p

40409

59p

40411

243p

40594

8 1 p

40595

92p

FETs

BF244

45p

MPF102

37p

MPF103

37p

MPF104

37 p

MPF105

37p

2N3819

27p

2N3820

GOp

2N3823

54p

2N5457

32p

2N5458

32p

2N5459

32p

3N128

81p

3N140

92p

3N141

81p

40603

63p

40673

54p

UJTS

TIS43

34 p

2N2160

86p

2N2646

38 p

2N4871

37p

PUJT

2N6027

GOp

DIODES

SIGNAL

OA27

9p

OA70

lOp

OA81

lOp

OA85

Up

OA90

7p

OA91

9p

OA95

9p

OA200

8p

OA202

lOp

1N914

4p

1N916

Up

1N4148

4p

RECTIFIER

BY 100

31p

BY 126

15p

BY127

15p

1N4001

6p

1N4002

6p

1N4004

7p

1N4005

7p

1N4007

8p

ZENER

2.7 to 33 V

400 mW

lip

1 W

22 p

TUNNEL

AEY11

75p

VARICAP

BB105

33p

NOISE

Z5J

140p

BRIDGE

RECTIFIERS

1 A 50 V

25p

1 A 100 V 27p

1 A 400 V 31p

1 A 600 V 37 p

2 A 50 V

37p

2 A 100 V 44p
2 A 400 V 56p

4 A 100 V 75p
6 A 50 V 65p
6 A 100 V 70p

TRIACS
Amp Volts

3 400

130p

6 400

162p

6 500

194p

10 400

200p

10 500

270p

40430

108p

40486

108p

40669

105p

DIAC

BR100

27p

SCR THYRISTORS
1 A 50 V T05 43p

1A100VT05 45p

1 A 400 V T05 50p

3 A 100 V STUD 53p

3 A 400 V STUD 81p

7 A 400 V T05 ♦ HS 87p

7 A 400 V T05 + HS 97p

8 A 50 V Plastic 142p

12 A 400 V Plastic 173p

16 A 100 V Plastic 173p

16 A 400 V Plastic 195p

16 A 600 V Plastic 238p

BT106 1 A 700 V STUD 150p
C106D 3 A 400 V Plastic 59p
MCR101 ft A 15 V T092 27p

2N3525 5 A 400 V T066 97p

2N4444 8 A 600 V Plastic 200p
2N5060 0.8 A 30 V T092 36p

2N5062 0.8 A 1 00 V T092 40p

2N5064 0.8 A 200 V T092 43p

VAT INCLUSIVE PRICES. Add 20p P & P - no other extras
MAIL ORDER ONLY. Minimum Order £ 2

TECHNOMATIC LTD

54 Sandhurst Road, London NW9

advertisement

elektor june 1976 — 653

FND 500 JUMBO 0,5" CC LED now only £ 1,02

SINTEL for CMOS

CD4000 ....

0.17

CD4027 ....

0.46

CD4052

.... 0.77

CD4085 ....

0.59

CD4001 ....

0.17

CD4028 ....

0.74

CD4053

.... 0.77

CD4086 ....

0.59

CD4002 ....

0.17

CD4029 ....

0.94

CD4054

.... 0.95

CD4089 ....

1.27

CD4006 ....

0.97

CD4030 ....

0.46

CD4055

.... 1.08

CD4093 ....

0.66

CD4007 ....

0.17

CD4031 ....

1.82

CD4056

.... 1.08

CD4094 ....

1.53

CD4008 ....

0.79

CD4032 ....

0.88

CD4057

...20.35

CD4095 ....

0.86

CD4009 ....

0.46

CD4033 ....

1.14

CD4059

.... 3.64

CD4096 ....

0.86

CD4010 ....

0.46

CD4034 ....

1.56

CD4060

.... 0.92

CD4097 ....

2.95

CD4011 ....

0.17

CD4035 ....

0.97

CD4061

... 16.43

CD4099 ....

1.50

CD4012 ....

0.17

CD4036 ....

1.82

CD4062

.... 7.33

CD4502 ....

0.98

CD4013 ....

0.46

CD4037 ....

0.78

CD4063

.... 0.90

CD4510 ....

1.12

CD4014 ....

0.83

CD4038 ....

0.88

CD4066

.... 0.58

CD4511 ....

1.28

CD4015 ....

0.83

CD4039 ....

2.86

CD4067

.... 2.95

CD4514 ....

2.56

CD4016 ....

0.46

CD4040 ....

0.88

CD4068

.... 0.18

CD4515 ....

2.56

CD4017 ....

0.83

CD4041 ....

0.69

CD4069

.... 0.18

CD4516 ....

1.12

CD4018 ....

0.83

CD4042 ....

0.69

CD4070

.... 0.18

CD4518 ....

1.03

CD4019 ....

0.83

CD4043 ....

0.83

CD4071

.... 0.18

CD4520 ....

1.03

CD4019 ....

0.46

CD4044 ....

0.77

CD4072

.... 0.18

CD4527 ....

1.30

CD4020 ....

0.92

CD4045 ....

1.15

CD4073

.... 0.18

CD4532 ....

1.16

CD4021 ....

0.83

CD4046 ....

1.10

CD4075

.... 0.18

CD4555 ....

0.74

CD4022 ....

0.79

CD4047 ....

0.74

CD4076

.... 1.27

CD4556 ....

0.74

CD4023 ....

0.17

CD4048 ....

0.46

CD4077

.... 0.18

MC14528 ..

0.86

CD4024 ....

0.64

CD4049 ....

0.46

CD4078

.... 0.18

MC14534 ..

6.04

CD4025 ....

0.17

CD4050 ....

0.46

CD4081

.... 0.18

MCI 4553 ..

4.07

CD4026 ....

1.42

CD4051 ....

0.77

CD4082

.... 0.18

MCI 4566 ..

1.21

RCA 1975 CMOS Databook 400 pages of data

and other useful information

New MOTOROLA McMOS Databook

MCM 14552 8.05

Clock Chips
MK50253 .. 5.60
MM5314 ... 4.44
AY51224 .. 3.66
AY51202 .. 4.76
MK 50250 .. 5.00

Displays

5LT-01 5.80

DL704E ... 0.75
FND500 ... 1.02

Flat Cable
20WAY 1 M 1.00
10M for .... 8.50
10WAY 1M 0.60
10M for .... 4.80

Vorocases
751410J .. 2.64
75141 ID .. 2.94
751 41 2K .. 4.00

sheets and 200 pages of circuits, applications

£2.67 (No VAT)

£2.77 (No VAT)

ADVANCED CLOCK KIT

Complete kit including attractive slim case for 6 digit alarm clock with bleep alarm, snooze,
high brightness driving of Jumbo LED displays, automatic intensity control - with optional
add-ons of touch switch snooze control and crystal control/battery back-up £ 26.80

P.E. CAR CLOCK with Journey Timer

6 digit clock for use in any car with 12 V battery, with an independent journey timer
incorporated. Bright Jumbo LED display comes on with ignition — automatic intensity
control. Complete kit of all parts needed including case. PCB's and all components. Full
instructions £ 39.50

Easy to Build E.E. DIGITAL CLOCK (Jan. issue). Kit of all components, including case etc.,

for this attractive clock with 12 mm green display. Full instructions £ 15.70

32.768 kHz Min. Xtal: High accuracy/stability for clock or watch £ 3.60

50 cps Crystal Timebase Kit — will provide stable 50 cps for any clock 1C giving time accurate
to within a few seconds a month; contains small PCB, 32.768 kHz Xtal, 3 CMOS IC's.

trimmer, zener, C's, R’s, 1C skts £ 6.28

MK5030M CMOS watch 1C for LED display with date and seconds £ 12.50

Display PCB's are available for clocks & counters (up to 8 digits)

SOLDERCON 1C PIN SOCKETS

The sensible method for lowest cost sockets for IC's, displays, CMOS, TTL

Strip of 100 for 50 p 400 for £ 2.00 1000 for £4.00 3000 for £ 10.50

8-way Boss Switch: 8 ultra-min. toggle switches in 1 6 pin Dl L £ 2.60

ADD VAT at 8% (higher rate does not apply to any of the above)

1 5 p p&p on orders under £ 3. Free p&p on books and orders over £ 3.

Price List & Data sent free with any order, or on request (an sae helps)

Official Orders welcomed, written, phoned or telexed, from Univs, Polys, Schools, Govt.

Depts, Nat. Inds., Rated Cos. etc. Fastest delivery for R & D

Export orders: no VAT, add 35 p (Europe) £ 1 (overseas) for Airmail p&P.

(No Export outside Europe for databooks and transformers).

IMTEL

SINTEL 53(K) Aston St.
Oxford Tel. 0865 49791

F.M. Tuners. 8-transistor chassis with Stereo-decoder and L.E.D. indicator £ 10.90

Aircraft-band receiver. Just place near any radio £ 3.90

Echo-chamber. (Endless tape). Variable delay £ 34.50

Field-strength indicators. 1-250 MHz £ 3.30

Stereo Amplifiers complete. 3-watt. 8-ohm £ 2.75

10-watt Amplifiers. 12 volt D.C. 3/8/ 15-ohm £ 3.90

Cartridges. Acos GP 104. Ceramic/Diamond £ 1.50

Cartridges. Acos GP 101. Crystal/Sapphiro/Compatible £ 0.50

Speakers. 2’/j”-8-ohm £ 0^35

Speakers. Car Stereo. 8-ohm, 5-watt. In cabinets £ 2.50

Dynamic Tape Mikes with remote-control facility £ 0.90

Crystal Tape Recorder Mikes £ 0 . 6 O

Crystal Mike Inserts with bracket £ 0^20

Indicators. 12-volt L.E.D. In Chrome Bezel £ o.35

'Bargain Bags' 4lbs Caps/Resistors/Transistors/Diodes £ 4 . 00

Controls. Volume/Pre-set (Rotary & Slider) Assorted 100 £ 2.50

Transistors. 20 NPN/PNP. All new and marked £ i.oo

Transistors. 100 NPN untested £ l!oO

Diodes. 100 Germanium untested £ o.50

Diodes. 100 Silicon untested £ 0.50

Diodes. 100 Zener untested £ g.50

'Pack 1’ 100 resistors. 100 ceramics. 100 diodes £ 1.00

Pack 2' 100 resistors. 100 ceramics. 100 polystyrene £ 1.00

'Pack 3' 100 resistors. 100 S/Mica/Ceramic. 100 Polyester £ 1.00

ALL ABOVE ITEMS PLUS 12’/*% VAT

Fluorescent 12-volt Camping Lights. 21” 13-watt £ 4.90

12” 8-watt £ 3.90

Disco type 3-Channel flashing light units. Built-in mike. No connection needed

to amp £17.50

Multimeters. AC 0- 1000V. DC 0- 1000V., 0-100 m A. 0-150 kohm £ 3.50

Multimeters. AC 0-500V. (10 ranges) DC 0-500V. (12 ranges)

DC Current 0-25 p A to 0- 1 0 amps ( 1 0 ranges)

Resistance 0- 1 00 ohms to 0-16 Mohms. (4 ranges) £ 1 1 .30

Panel Meters. 0-50 pA. 2 3 /*" x 1 7 /*" £ 2.50

Soldering Irons. 15-watt. Pencil Bit £ 1.20

Servisol Switch Cleaner (with Snorkel) £ 0.50

Copper-clad Fibre Glass Board. Single-sided. Square foot £ 1.00

Double-sided £ 1.25

'Fotolak' Light sensitive spray for printed circuit making £ 1.30

Developer for same £ 0 39

Ferric Chloride for etching £ 0^40

ALL ABOVE ITEMS PLUS 8% VAT

G.F. MILWARD. 369 Alum Rock Road. POSTAGE: Below £ 10 50p

Tel. 021-327 2339. Birmingham B8 3DR. Above £ 10 Free

D

gS ELECTRONICS

SEMICONDUCTORS

54 Montagu Street Kettering Northants Phone Kettering 83922

shop open Monday to Saturday 9.00 to 6.00 early closing Thursday 1.00 p.m.

AA 119

10

BC 517

POA

OA 200

10

AC 126

16

BC 547

12*

OA 202

10

AC 127

16

BC 548

12*

OC 28

75

AC 128

16

BC 549

12*

OC 35

50

AC 176

19

BC 557

15*

OC 42

40

AC 187

19

BC 558

15*

OC 44

18

AC 188

19

BC 559

15*

OC 45

16

AD 149

50

BCY 70

15

OC 70

15

AD 161

50

BCY 71

15

OC 71

15

AD 162

50

BCY 72

15

OC 171

30

AF 1 14

25

BD 131

40

OCP 71

75

AF 1 15

25

BD 132

40

ORP 12

70

AF 116

25

BD 139

65

TIL 209

20

AF 117

25

BD 140

75

TIP 31 A

50

AF 118

45

BD 242

POA

TIP 32A

55

BA 145

16

BF 194

10*

TIP 41 A

70

BA 148

16

BF 195

10*

TIP 42A

85

BA 154

16

BF 196

10*

TIS43

30

BA 191

POA

BF 197

10*

ZTX 107

10

BB 103

30

BF 198

12*

ZTX 108

10

BB 104

70

BF 199

12*

ZTX 109

10

BB 105

35

BF 200

30

ZTX 300

20

BB 109

POA

BF 254

30

ZTX 500

20

BB 110

30

BF 255

30*

IN 914

5

BC 107

10

BF 494

POA

IN 4148

4

BC 108

10

BF 495

POA

IN 4001

4

BC 109

10

BFX 29

28

IN 4002

4

BC 139

25

BFX 30

28

IN 4003

4

BC 140

30

BFX 34

POA

IN 4004

5

BC 141

26

BFX 41

POA

IN 4005

5

BC 142

20

BFX 84

25

IN 4006

6

BC 143

24

BFX 85

25

IN 4007

6

BC 147

10*

BFX 86

25

2N 1613

20

BC 148

10*

BFX 87

35

2N 2646

45

BC 149

10*

BFX 88

25

2N 2926B

10*

BC 157

10*

BFX 89

60

R

10*

BC 158

10*

BFY 50

15

2N 2962

10*

BC 159

10*

BFY 51

15

2N 2962Y

10*

BC 160

35

BFY 52

15

2N 2926G

10*

BC 161

35

BR 100

30

2N 3053

16

BC 177

18

BR 101

30

2N 3054

45

BC 178

18

BRY 39

40

2N 3055

50

BC 179

18

BRY 56

50*

2N 3819

20

BC 182L

12*

BU 105/02 200*

40603

75

BC 183L

12*

BU 108

250*

40673

75

BC 184L

12*

BY 100

25

BC 212L

12*

BY 127

15

BC 213L

12*

E 100

40

BC 214L

12*

E 300

55

BC 237

16*

MJE 340

50*

BC 238

16*

MJE 341

80*

BC 239

20*

MJE 2955

120

BC 261

20

MJE 3055

75

BC 262

25

MPF 102

30

BC 337

15*

OA 81

12

BC 338

15*

OA 90

9

BC 516

POA

OA 91

9

DISCOTHEQUE EQUIPMENT

ULTRAVIOLET BULB: 75 w 'Balck Magic*. No control gear required. ES or BC

fitting 240 v AC £ 7.50

SOUND TO LIGHT

Pulsar Zero 2250: £ 27.50

3 channels of 750 w eacn. Connects to any amplifier and automatically compensates
for any change in output level. No need to adjust anything to keep lights operating with
different records or volume settings.

Pulsar Zero 3000: £ 69.50

3 channels of 1 kw each. Connects to any amplifier and offers full control facilities:
normal sound to light, variable speed sequence, manual, low/full brightness switch and
special music sequence position-sequence speed on each channel is independendtly
varied by the music input giving unique and constantly varying output which still relates
to the sound input.

STROBE

Pulsar Super Strobe £27.50

Frequency variable, 4 to 20 Hz, 4 joule output, suitable for small and medium halls.
Attractive case, free standing or wall mounting.

FITTINGS

100 w BC or ES spot bulbs, red, yellow, green, blue, clear £ 1.20

Swivel spot bulb holders. Wall, ceiling or spot bank mounting, BC or ES £ 1.70

Spot bank with three holders and cable, BC or ES £ 17.50

74 Series TTL

7400 12 7404 12

7401 12 7405 15

7402 12 7406 30

7403 12 7408 15

7410 13
7413 31
7432 25
7441 62

7442 55
7445 71
7447 79
7474 26

7476 26
7483 75
7486 26
7490 40

7491 55

7492 45

7493 40
74100 89

74121 28

74122 28
74141 63
74145 58

OTHER COMPONENTS

Zener diode 1 w 3.3 v to 200 v E24 Series

Zener diodo 400 mw 3.3 v to 47 v E 12 Series

Resistors, Carbon Film VJ w 5% E 12 Series

Capacitors C280 2 50 v dc .01 jiF to 2.2 pF E6 Series ....

Veroboard 0.1” and 0.15” 2 Vi” x 5"

Sub. miniature presets. Fit 0.1 ” board

Resistors, wire wound, 2.5 w, 0.22 to 10 Ohms E24

Resistors, metal film, (MR 25 type) 1% 4R99 to 100 k E 96
Potentiometers: Single gang have nylon shaft

5 k | 10 k J 25 k | 50 k | 100 k|250 k | 500 k) 1 m

2 m

Single gang

log and lin

log

30 p*

Single gang & DPST

log

log and lin tog

log

&

lin

log

50 p*

Tandem

log and lin

log

80 p*

Tandem & DPST

N/A | log | N/A

95 p*

10 11 12 13 15 16 18 20

22 24 27 30 33 36 39 43

47 51 56 62 68 75 82 91

E 24 » whole series and multiples
E 12 = bold figures
E 6 = boxed figures

74174 83
741771.00
741961.34

BULK OFFERS

IN 4001/2 30 p/10

IN 4003/4/5 45 p/10

IN 4006/7 50 p/10

IN 4148 20 p/10

BC 107/8/9 75 p/10

741 8 dil £ 1.95/10

NE 555 £ 1.60/ 4

Red LED £1.00/10

Yellow/Amber/Green LED .£1.50/10

BFY 50/1/2 £ 1.50/10

BC 212L 80 p/10‘

SPECIALS

Few only left in stock: 8 track 12 V + or
— earth car cartridge player. Used and
untested, but complete .... £ 5.00*

LW MW & FM portable casette radio,
battery/mains, internal and remote
microphones, carrying handle, used,
untested, but complete .... £ 10.00

ORDERING

INFORMATION

VAT add high rate to
rate to all others.

items, standard

A

POST free on orders over £ 5.00, other-
wise please add 30 p. Overseas please add
freight costs and state method of de-
spatch required (BFPO excepted).

DELIVERY by return 1st class post
unless otherwise requested. Express
delivery available by City Link or
sccuricor if required. Phone for details.

PAYMENT Cash, Cheque or Postal order
with order Access or Barclay card by
phone or letter for orders over £ 2.00.

GUARANTEE All devices are brand new
and full spec unless otherwise stated.
Any faulty item returned unused and
in good condition within seven days will
be exchanged or refunded.

654 — elektor june 1976

advertisement

Build tf-vowse/fi

Designed by

TEKAS ^

Featured by PRACTICAL WIRELESS
ISOLE U.K. DISTRIBUTORS - HENRY’S

Build the Texan stereo amplifier, then you can bo doubly proud I For a start,
you'll own a superb homo ontortainmont
unit. And have had all the pleasure of
doing it yourself, with the Henry's kit.

Look at the Texan specification

Incorporating fully integrated stereo preamp
and power amp, with 6 IC’s. 10 transistors,

6 rectifiers and zener diodes. Plus stabilised,
protected circuitry, glass fib pcb: Gardeners
low-field low-line mains transformer; all
facilities and controls. Slim design, chassis
14}" * 6" x 2" overall. 20 watts per channel
RMS, less than 0.1 % distortion at 1 KHz.

★ Can be built Stage by stage
Ath for leaflet 20.
ir E verything necessary
supplied. Full after sales service
and guarantees.

KIT PRICE

£35.00

Inc. VAT 4- Cl p&p

Built and tested
£45.00 inc. VAT
+ 11 .00 p&p.

THE NATURAL FOLLOW-ON - THE TEXAN FM TUNER KIT!

KIT PRICE

£25.95

Inc. VAT +

60p p&p.

Build the matching Texan stereo tuner ! Features
advanced varicap tuning. Phase lock loop decoder
Professionally designed circuit. Everything you need is
in the kit. From the glass fibre pcb to the cabinet itself.
Excellent spec : 2.5 uV aerial sensitivity. 500 mV output
(adjustable). Tuning range 87-1 02 MHz. Mains
powered.

Built and tested £30.95 inc.VAT +50pp&p

VIDEO SPORT

all the electronic excitement
you could wish for!

An up-to-the-minute game. Plugs
into your own TV aerial socket
Switch on. And you're away !
Choose your game - football, tennis
or hole-in-lhe-wall Absolutely
safe. For you. Your children. And
your TV. Mams powered.

List Puce C42.50

HENRY'S PRICE-ONLY £29.50

me. VAT -F
50p p&p.

For this new edition, we have made
hundreds of changes and additions.

It has over 200 pages, containing
vutually everything for amateuis and
professionals. And you'll have no
bother at all finding everything you
want, because there’s a complete
alphabetical index as well as a section
index. Together, they put you right on
couise for the items you need. From
Sinclair protects to educational kits. I
Oscilloscopes to panel meters. Coils to /
capacitors. Transistors to valves.
Loudspeakers to microphones - all at /
competitive prices. Over 200 I,
pages of vital statistics - just for \
you! So send now for your copy.

FREE to Educational Establishments when
ordered on official headed notepaper.

25p carr./pack.

H&wus

st LF-StHVICE
3 «9 F0CWXfi E

' c *

404/6 EDGWARE ROAD, LONDON W2 01-402 8301
LOWERMLES FLOOR. 231.TOTTENHAM CT. RD.. LONDON W1 01-636 6681
94/96 UPPER PARLIAMENT STREET, NOTTINGHAM. 0602-40403

All mail to Henry 's Radio. 202 Cdgwata Road. I ondon Vi 2

new

MIDLANDS
STORE

Technology
spoken here :

New this month are 520 MHz divide-by-ten ICs, the 11C90 at £14.00; a new
extruded aluminium heatsink for the TDA2020 for 70p, when purchased
with the 1C, and a new series of cases, especially conceived for our range of
tuner modules, for AM, FM, and now TV sound "off-air".

5600

EC3302

7252

7253

9001

9002
9007
AB47

Varicap Mosfet with 4 tuned RF cett
Varicap FET/Bipolar mm. tunerhead
Top quality tunerset VHF to audio
Varicap tuned with 3 meter outputs
Tunerset with built-in stereo decoder.

Varicap tuned.

Edgewise illuminated meters: 35uA.

35 x 14mm as used with Larsholt
7252/7253

Frequency scale 88-108
Signal strength scale 0-10
Tuning meter scale 3-0-3
Muliiturn varicap control pot. 40 turn 100k 0.35

TV SOUND SYSTEM

7700

7701

5700

5770

8011

8005

"Off-air” UHF TV sound receiver
Varicap tuned, with interstation
muting, and sound detection at 38MHz
Chassis and cabinet for above
(available March 1976)

UHF TV varicap tunerhead
Tunerhead + 4 way pre selector
6 station electronic station selector,
incorporating a muting output, AFC
lock and scan tuning. Built.

A kit of accessories for the 7252/3
tunerset, to provide power stabilizer
MPX filter and audio gain, meter drives.

Special Offer Packs
S07448 6 x 7448 4 6 x DL704
SO7001 CT7001 + 6 x DL704 ♦ Socket
SOFM KB4400 4 KB4402 + 586 4 7BA220K

Logic

T1C90 14.00

Varicap Diodes
MVAM 1 2.75
MVAM2 1.05
BA102 0.30

BA121 0.30

MV104 0.45

10.00

Radio/MPX and linear ICs

5.00

CA3089E

1.94

CA3G90AQ

3.75

24.00

MC13I0P

2.20

MC1350P

0.70

24.00

SN76660N

0.75

TBA651

1.81

UA720PC

1.40

TBA810AS

1.09

2.50

TCA940E

1.80

2.50

(Prices for heatsinks, when

2.50

purchased with ICs: 14peach

k 0.35

810/940).

TDA2020

2.99

NE560

2.50

NE561

2.50

26.00

NE562

2.50

NE565

2.50

7.50

NE550

0.80

5.50

8.60

Toko filters for

AM/FM/TV/MPX

MFH41T

1.65

14.99

CFT470C

0.55

SFE6.0MA 0.80

CFS10.7

0.40

4.99

BBR3132

2.25

BLR2007

1.60

BLR3107

1.60

10.00

12.50*

OTHER AM/FM COILS

3!oo

IN OUR LISTS

a free price and stock list •

which has been

ambit

revised extensively during March. There is a new Larsholt
Signalmaster FM tuner * and a companion 25+25W audio
amplifier kit, as well as further details on our broad range
of specialist wireless and audio products.

PP 22p per order, VAT is generally at 25% - and the min.
CWO charge is £1. Min. invoice £7.50, Catalogue 40p .

C 8% VAT)

INTERNATIONAL

25 High Street, Brentwood, Essex, CM14 4RG. Tel: 216029; Tlx: 995194.

printed circuit boards,

name plates,
labels

and panels.........

Specialising in medium and short runs, backed up
with full Art and Tooling services from:

C.M. TECHNICAL SERVICES,

130 Lancaster Rd., New Barnett, Herts. Tel:
01 440 0919

publishers announcement

The government has announced that as from Monday 12th of April
the higher rate of VAT is reduced from 25 per cent to 12 1 /? per cent.
Some of the advertisements in this issue of Elektor may still show
VAT at 25 per cent due to lack of time for amendment. We rec-
ommend that readers should check with the advertiser regarding the
rates quoted before ordering. The publishers can not be held respon-
sible for any error in VAT rates quoted.

As our Editorial Staff will be at the
HE DA and Sound and Vision exhibitions
in Birmingham from May 23rd to 31st,
the Technical Queries 'phone-in' will not
operate on Monday May 24th and 31st.
We shall, however, be pleased to talk
with you in person and answer your
queries at our exhibition stand:

Hall No. 3,

Stand No. 501 5,

National Exhibition Centre,

Birmingham.

advertisement

elektor june 1976 — 655

I

Look through this issue of ELEKTOR and you will find that
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different

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1-24

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£2.36 *

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£1.30 *

£1.08 *

I.C. SOCKETS

LINEAR I.C.'s

£1

£1

£1

£1

£1

£1

1 4p
1 4p
I 4p
.06
1 5p
.17

14p *
14p *
46p *
.17 *
.17 *

44p *

93p *
.25 *

53p *
.31 •

. 1 7p •
I4p *
.27 ‘

84p *
Up *
.86 *
65p *
. 0 ? *
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47p *
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99p *
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46p *
46p *

.85 •
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75p*

1 9p *
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1 9p *
19p •
47p *
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1 9p *

85p *
85p ‘
.04 *
,96 *
44 •
87p *

3h DECADE DVM IX.

rpul

Th Is jfate-of-fhe-art MOS LSI chip confainj
oil the logic necetiary for o 3; decode, dual
slope integrating, automatic polarity detecting
DVM Supplied with free data and circuit
booklet. AY-5-3507

OUR PRICE ONLY £6.59.* 151

(Data and Circuit Booklet* alone ?0p.)

The AY-57224 tick tock

Another marvel from G .1 . A 16 pin
1 2“?4 hr . Clock I .C . with 25 pin capability
and low external part* count. Supplied with
manufacturer* defoiled leaflet £3.95p*(inc.
VAT) (Leaflet alone 20p.) Full Kit
(excluding cote) available toward*
end of 1975. Phone Clive for detail*.

m

MU L LARD MODULES

Still make the jimplett, highly
reliable F .M . tuner

X.

I- >. r

LPI186 Varactor front end £5.38

LP1185 I.F. Strip £6.22

LP1400 Multiplex decoder £5.62

VAT IN<

Z

Pin Socket*, pin* in ttripi
of 100. Ju*f *nip off what
you need. 65p per strip
Dual in line 71

8 pin I3p, 74 pin 26p

14 pin 15p 28 pin 3 Op.

16 pin I5p 36 pin 39 p.

TOS

8 pin 3 Ip .

KJpin 35p.

FREE CIRCUITS

Our 8 Page A4 Audio I.C. Booklet
it tupplied FREE with purchote* of
Linear I.C.’t worth £1, or more
(35p . if told alone) Contain* circuiti
and pin connection*

15 Amplifier* ?50 mW to 20 watt*

5 Audio Pre-Amplifier*

Tape Pre-Amplifier
Power Driver

Instrument Amplifier (Bifer)
Generol Purpote Mini Amplifier
D.C . Controlled Gain Control
Micro-mini radio (2 I.C'*)

PROTO -DARLINGTON

Vceo 25v 2N5777

Vcbo 25v
Vebo 8v

II 750 mA „ ///

Pd 200 mW J- ) -

Hfe 2500 >/J

35 p

- LIGNT

NEW LED Linear Cursor*
each device contain* 10 light
cmj fting diode* in a 20 pin dual-
in-line package. Ideal for jolid
Jtate analogue meter* or dial*

Type 101 RED £2.26.* Complete

wi th leaflet .

74 TTL

7400

7401

7402

7403

7404

7408

7409

7410
7413
7417
7420
7427
7430
7432
7437

7441

7442
7445

7447

7448
744 7A
7470

7472

7473

7474

7475

7476
748?

7485

7486

7489

7490

7491

7492

7493
7495

74100

74107

74121

74122
74141
74145
74154
74174

74180

74181

74192

74193
74196

24

25-99

100-

Up*

I2p *

10p

•

Up*

1 2p *

lOp

•

Up*

1 2p *

lOp

•

15p*

i?!p*

lOp

•

16p*

13 P *

Up

•

16p*

I3 P *

lip

•

I6p*

13p*

lip

•

I6p*

13p*

lip

•

?9p*

24p*

?0p

•

27p*

22 : P *

20p

•

16p*

1 3p *

lip

•

27 P *

22-p*

I8p

•

16p*

13p *

lip

•

27p*

22;p*

I8p

•

?7p*

22;P*

I8p

•

75p*

62p*

50p

•

65p*

55p*

43p

•

85p*

71p*

57p

•

81p*

75p*

65p

•

75 P *

62p*

50p

•

95p*

83 P *

67p

30p*

25p*

?0p

•

25p*

21p*

I7p

•

30p*

25p*

?0p

•

32 P *

26p*

21 P

•

47p*

39p*

3 1 p

•

3?p*

26p*

21p

•

75 P *

6?p*

50p

•

.30 *

£1.09 *

87p

•

32p*

26p*

?lp

•

49p*
65p*
57 P *
45p*
67p*
£1.08 *
35p*
34p*
47p*
78p*

68p*
£1 . 6 ? *
£1 .00 *
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£3.20 *
£1.35 *
£1.35 *
£1.64 *

40p*

55p*

46p*

40p*

55p*

89p*

?8p*

28p*

39p*
63p*
58p*
£1.48 *
83p*

88p*

£2.50 *
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£1.34 *

£1

3?p *
*

36p *
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??P *
23p *
3 1 p *
53p *
48p *

86p *

67p *
7 1 p *
.90 *

90p *
90p *
99p *

555 <8 pin diplV 55p

555 (TO-991T 8lp '

556 (14 pin dip' £1.29

703 (RF 'IF Amp'
709 (8 pin dipt
709 (TO-99)

709 (M pin dip)

710 (8 pin dip'
710 (TO-99)

710 (14 pin dip)
71 KTO-99)

711 (14 pin dip)
720 (A. M. Radio
723 (TO-99)

723 (14 pin dip
741 (8 pin dip
741 (TO-99)

741 (U pin dip)

747 M4 pin dip)

748 (8 pin dip)
748 (T0-99>

748 (14 pin dip)
753 IF.M. Ijt. I

75491

75492

68p

38p
45p
39p
39p
45p
44p

51 P
44p
,) £1.76
£1 .09
55p
30p
43p
36p
£1.04
42p
46p
49p
F)

£1.08
88 P
El. 10 '

AY-1-0?12
AY -I -5051
AY-5-1224
AY-5-3500
AY-5-3507
AY-5-4007

Regulator* 100 mA
78I05V/C ( T 0-92' 60p *

78LI2WC (T0-92) 60p *

78L15WC (T0-92) 60p *

Regulator* 100mA
78L05AWC (TBA625A) <?0p
78L12AWC (TBA625B) 90p
781 1 5AWC (TBA625C) 90p

Regulator* 500mA
78M05HC £1.35 *

78MI2HC £1.35 *

78MI5HC £1.35 *

78MI8HC £1.35 *

78M24HC £1 .35 *

Re gulator* lA

7805 KC (T0-3) £2.09 *

781 ?KC (T0-3) £2.09 »

78I5KC (T0-3) £2.09 *

78I8KC (T.V3) £2.09 *

7824KC (TO-3) £2.09 *

Regulator* lA

7805 UC (T0-220) £1.72 *

78 1 2UC (T 0-220) £1.72 *
781 5UC (T0-220) £1.72 *

78I8UC (T0-220) £1 .72 *

7824UC (T0-220!£l .72 *

BHA0002

CA21I1

CA3045

CA3046

CA3053

CA3065

CA3075

CA3078

CA3080

CA308I

CA3082

CA3089E

CA3097E

CA3123E

CA3130

CA3401E

CA3600E

£6.93
£1 .44
£3.95
£6.59
£6.59
£7.94

£3.01

£1.19
El .69

88p

59p
£1 .60
£1 .64
£1.26
59p
£1 .86
£1 .86

(TDA1200) £2.43
£1.67 *

£1 .76
84 p

(L M3 900) 68p
£1 .44

L005T1 (TO. 3)
L036T1 (TO. 3)
L037T1 (T0-3)
LI 29 (SOT -3?)
L 130 (SOT-32)
L 131 (SOT-32)

£1 .46
£1 .46
£1 .46
85p
85p
85p

ICL8030

£3.52

LM30IT (TO-99) 65p

LM301S (8 pin dip)59p
LM301 A T(T0-99) 67p

LM301 A S(8 pin dip) 59p
LM307 T (TO-99) 59p

LM307 S (8 pin dip) 57p
LM308 T (TO-99) £1.96

LM308 S (8 pin dip) 98p
LM308A T (TO-99) £7.92

LM308A S (8 pin dip)£6.90

LM309K

LM339

LM370N

LM37I

LM372N

LM373N

LM377N

LM380

LM381

LM382

LM703

LM1820

£2.34

£2.25

£2.85
£2.08
£1 .99
£2.99
£2.71
£1.25
£1 .85
£1 .66
68p

£1.03

LM2111

LM3900

LM3909

LP1 186

LP1185

LP1400

MC1303L

MC1306P

MC13I0P

MC1312P

MC1314P

MC1315P

MC1327P

MC1330

MC1339P

MCI 350

MC1351

MCI 352

MC1357

MC1358

(CA3065)

MCI 375

MC1455(555T)

MC1456CG

MCI 458CP1

MC1468G

MC1495L

MC149GG

MC3302P

MC3401P

MFC4000B

MFC4060A

MFC6030A

MFC6040

MM5314
MM5316

£1.12

69p

66p

£8.60

£6.95

£9.02

£1.94

85p

£ 2.10

£2.52

£4.34

£4.85

£1.48

89p

£1.60

68p

92p

92p

£1.60

£1.23
£1.56
65p
£1.77
89p
£2.30 *
£4.48
£1.01
£1.65

81p

87p

85p

85p

£ 1.01

£4.80

£9.99

MVR5V (T03)£1.45
MVR12V(T03) £1.45
MVR 1 5V(T03) £1.45

NE5401

NE546A

NE555V

NE556

NE560Q

NE561B

NE562B

NE563

NE565N

NE566V

NE567V

SD6000

SL414A

SL415A

SL437D

SL440

SN75491N

SN75492N

£1.25

£1.16

59p

£1.29

£5.06

£5.06

£5.06

£2.96

£2.63

£1.87

£2.63

£ 1.22

£2.09

£2.75

£7.50

£2.85

88p

£ 1.10

2N414 Leaflet free with devices ( 10p atone )

MCI310; 2, 4 & 5 Leaflet free with device* (lOp alone)

SN76001N (TAA611) £1 .82
SN76003N £3.30

SN76013N £1-98

SN76023N £1.98

SN76 227N(MC!327) £1 .89
SN76537N £1.86

SN76544N £1.81

SN76550-2(TAA550)89p
SN76552-2 81p

SN76660N(TBA1 20) 75p
SN76666N (C A3065) £1 . 1 2

TAA?63

TAA300

TAA310A

TAA320

TAA350

TAA370

TAA550

TAA570

TAA700

TBAI20S

TBA231

TBA?81 (723)

TBA500Q

TBA520Q

TBA530Q

TBA540Q

TBA550Q

TBA560CQ

TBA625A

TBA625B

TBA625C

TBA65I

TBA720Q

TBA750Q

TBA800

TBA8I0S

TBA810AS

TBA820

TBA920Q

TBA990Q

TCA270Q

TCA760

TCA800Q

TCA830S

TCA940

TDAI054

TDA1200

TDA1405

TDA141?

TDAI415

TDA2010

TDA2020

ULN2I11A

ZN414

£1.50
£2.16
£1.87
£1 .44
£2.43
£3.45
75
£2.75
£5.03

£1.25
£ 1.02
£2.59
£3.16
£3.85
£3.27
£3.72
£5.29
£5.29
£1 .03
£1 .03
£1.03

£1 .87
£2.79
£2.79
£ 1.11
£1.24
£1.24

86p

£4.71

£4.71

£5.24
£2.16
£7.24
£1 .04
£2.25

£1 .50
£2.43

80p

8 Op

80p

£3.00

£3.75

£1.52

£1.26

Lifronix Double Digit Ditplay*
0.5" Common Anode; 2 R/H
Decimal Point*

DL721 ± 1.9
DL727 0.0 to 9.9

Suitable for Clock*, Meter*,
Instrument*, Channel Indicator*
Our price £4.75 * eoch

LED DISPLAYS

NEW

DIGITAL SWITCH

I o

I. u.

Low co*t Red GoAiP
Motorola MLED 500
in a T092 package

ia *

U

• U Mj

41 V *> o

mi

< < < o

• • • •

u u O u

BCD encoded digital switch
Reading 0 to 9. Suitable for
digital clock alorm setting
DVM input Scaling etc.

I to 9. £1 .49 each *

0.33 LI front x DL 707 Series
0.33" Montanto MAN 50770/8(^3600
0.33, Xciton XAN 70 Serie*

KVjntanto MAN 4000 Serie*
Litronix DL747 'Jumbo' Series

NOTE:

0.43,

0.63

J ■/ -/ */ all £1 .82* each (Red only)

on £1 .82* Each (Red, green, yellow, Orange)
/ .// . oil £1 .49* Each (Red G reen, yellow)

\/ J y y * oil £2.3?* Each (Red, Green, Yellow, Oronge)
:// all £242* Each (Red onfy)

Common Cofhode a* Common A node (Red only)
MAN 4000 Serie* pin out* are 14 pin dil the tame at MAN 50; 70 ond 80 series.

LIGHT EMITTING DIODES

tout'd

Free *nop~on plastic retainer

0.125" 0.16"

dio Jen*
(T1L209)

dia . lent

0 . 2 "
dia. lent

(MLED 650)

1*

10*

100*

1*

10*

100*

1*

10*

100*

Red

I6p

1 5p

13p *

27 P

24p

22p*

18p

I6p

Up *

Green

27p

24 p

22p*

33p

30p

27 P *

30p

27p

25p *

Oronge

27p

24 P

22p*

33p

30p

27 P *

30p

27p

25p *

Yellow

34p

3 1 p

29p*

35p

32p

29p*

35p

33p

3 Op *

Our Bulk Buying Power enable* a
repeat of our Special Offer:
0.337, (LIT 707) 90p.*(inc. VAT)
0.63 (LIT 747) £1.99 .*(inc. VAT)

OPTO ISOLATORS

I L 1 4N25 or T1L116
6 pin induttry standard packoge
2. 5KV isolation £1.00,*

MAINS TRANSFORMERS

Secondaries

6-0-6V
9-0-SV
1 ?-0-l 7V
20-0-20V
24-0- 24V
28-0- 28V

100 mA
100 mA
100 mA
I A

500 mA
1 A

97p.

97p.

97p

£4.55

£2.48

£6.18

0-9-17 V

0-1 2-15- ?0-?4-30V
0-24-30-40-48-60 V
0-19-25-33-40-50 V

lA

£2.70 *

__IA

£1.95 *
£2.48. *
£5.18 *
£3.40 *

__2A_.

£2.27

£4.15.

£7.02

£4.53

4A_

£2.64 *

p.p. on transformer* 10% of price, min. 20p

t

M6800 has taken

the gamble out of
microprocessors

Seven reasons why you'll always win with M68Q0.

1 . Programming language.

So easilv learned that it makes your transition
to MPU's that much easier.

2. Unlike competitive ranges, the M6800 family
is capable of further development while still
maintaining upward compatibility.

Example: The M6900 series is now being
defined to meet defined customers'
requirements.

3. Very efficient programme code.

Wide instruction repertoire, including seven
addressing modes.

4. Sub-function devices already available.

5. Single power rail. 5 volt.

6. Interfaces easily with TTL and CMOS.

7. Second sourced by AMI across Europe.

Heres the M6800 family today: —

MC6800

MC6820

Microprocessor.

Peripheral Interface Adapter.
MCM6810 Static RAM.

MCM6830 ROM.

Asynchronous Communications

4 /

Interface Adapter.

Low Speed Modem.

MC6850

MC6860

Alternative N-Channel Si Gate RAMs for
large systems: —

MCM 38102 IK x 1
MCM6814' 4Kx 1
MCM 68 15 4K x 1

Static 16-pin.
Dynamic 16-pin.
Dynamic 22-pin.

Recent new devices include: —

Dynamic Memory Refresh Controller.

%7 v

MCM681 12A 256 x 4 Static RAM, 16-pin.

MCM 683 17 16K Static ROM, 24-pin.

An 8K x 1 erasable and electrically
reprogrammable ROM (MCM 68708) was
introduced in the first quarter of 1976.

And there's more to come!

MOTOROLA

Semiconductors

Motorola Ltd. Semiconductor Products Division
York House, Empire Way, Wembley. Tel: 01-902 8836.