illill

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a

INDIA

1.03

TELECOMMUNICATION NEWS • TELECO

INDO-ARAB CABLE
LINK

The India-United Arab
Emirates submarine
cable communication
link was commissioned
recently. This
telecommunication
facility is in addition to
the already existing
International Subscriber
Dialled service and the
bureaufax facility for
facsimile transmission
of documents within
seconds.

The India-UAE cable
system is a joint
international
communication project
with costs being shared
by both the countries.
The system uses a
coaxial cable
connecting Bombay
and Fujariah. It provides
1380, two-way grade
circuits. The total length
of the cable is 1964 km.
The international
telecommunication
traffic stream between
India and the UAE is
one of the largest next
only to the UK and the
USA. About 250,000
Indians live in the UAE.
The Videsh Sanchar
Nigam Limited (VSNL)
formerly known as the
Overseas

Communication Service
of India and the
Emirates

Telecommunications
Corporation Ltd. have
jointly planned and
implemented the
submarine cable
project.

While satellite
communication was
already providing
reliable wide band
communication
capacities, there were
still certain drawbacks
like the propagation
delay of the order of 250
milliseconds on each
satellite hop and the
susceptibility of
microwave satellite

transmission to external
interference. It is an
international practice to
provide alternate
transmission medium
in case of failure of any
one system. This view
was shared by both the
governments and the
submarine cable project
work took birth in 1981.

By this time, optical
fibres emerged as a
contender for the
conventional coaxial
cables. But, optical
communication
technology was proven
only on short routes.
Further, costs involved
were too high for the
required circuit
capacity. Hence,
conventional
technology was chosen
for the India-UAE link. A
memorandum of
understanding was
signed by both the
countries in 1984. The
total cost of the project
is Rs. 80 crores.

When this project was
put for global tender
Japan and USA did not
respond as

manufacturers in those
countries were no
longer producing
copper trunk submarine
cables. They switched
over to fibre optic
cables. Standard
Telephone and Cable
company of the UK was
given the contract for
supply, installation and
commissioning of the
system and in 13
months the project was
completed.

The light weight
unarmoured cable is
used where the depth
of the sea exceeds 800
metres. The off-shore
and fishing activities
are more likely in
coastal area and the
cable laid in such
regions face hazards.
Outside sheath of the
cable is armoured with

high tensile steel wires
for protection. Double
armoured cables are
used in shallow waters.
In some portions, the
cable is laid as below as
3550 metres in the
Arabian Sea.

Initially, investigation of
sea and bed profile,
sub-bottom stratum,
cable fault histories,
water temperature and
its quality offshore and
fishing activities etc.
had been carried out to
determine the basic
route. During the survey
prior to the laying ofthe
cable, sea bottom
profile, topography of
sea bed, quality and
temperature of sea
water, seismic activity,
under current, reefs and
wrecks, marine
plantation and
navigational data were
collected.

As a result of advances
in micro-electronics
and computers which
are being integrated
with communication
systems, the capital
cost of submarine cable
circuit has come down
drastically. The capital
cost per channel
kilometre in 1956 was
580 dollars. It came
down to 70 dollars in
1965 and in 1987, it cost
just 22 dollars.

The first fibre optic
submarine cable will be
commissioned across
the Atlantic in 1988. It
will have a capacity of
40,000 circuits. Instead
of a repeater for every
25 km in a copper cable,
optical fibre requires
repeater once every 150
to 200 km.

The first cable laid in
1956 was retired last
year after 30 years of
service because there
was no need to maintain
it for the meagre 36
circuits provided by it.
Satellites require

replacement every
seven years and next
generation satellite
may last for 14 years.
Satellites, dependable
during peace, can
become a security risk
during global wars. In
the 130 years of
submarine cable
history, no cable was
damaged due to enemy
action. They could not
be tapped unlike
satellite

communication.
However, satellites have
no rival for providing
communication to
inaccessible and
inhospitable places.
India had its first
submarine cable for
telecommunications in
1869-70 when the
Eastern Telegraph
Company of UK laid a
cable connecting Suez-
Aden-Bombay.

The first submarine
cable of India was
commissioned in 1981,
linking Madras and
Kuala Lumpur, covering
a distance of 2509 km.
The India-UAE link is
the second submarine
cable ofthe country.
The signals in the
submarine cables have
to be amplified at
regular intervals and
this is achieved by
providing submerged
repeaters at suitable
intervals. The nominal
repeater spacing for
India-UAE cable is 13.5
km. The cable contains
147 repeaters each
giving a gain of 48 dBs.
Each repeater boosts
the received power by
60,000 times or in other
words the journey of a
speech from Bombay to
UAE is enhanced by
8.82 million times.

A big ship, specially
built for cable laying,
called"Venture" was
used for deep waters
and a small cable

.20

TELECOMMUNICATION NEWS • TELECO

ship"Galaxie" was used
near the shore. When
the cable was brought
to the shore near
Bombay with the help
of a rope tied to a boat,
it was kept floating by
means of inflated
balloons. The submarine
cable was joined to the
land cable in Bombay
Back Bay . After the joint
was accomplished the
balloons were deflated
and the cable slowly
sunk to the sea bed.
Though the first under
water cables for
telephony were laid in
1891, the real long
distance under water
telephony began with
the commissioning of
the transatlantic
telephone cable in 1956.
The invention of
insulating polyethylene
and polypropylene
made the cables more
resistant to moisture.
This ensured a life
expectancy of over 25
years for the cables.
There are now 135
telephone cables on the
ocean beds around the
world. All of them use
copper conductors in
coaxial formation. The
number of telephone
circuits which were 36
in 1956 have now gone
upto 2000 . In some
shorter cables, even
4,000 circuits are
provided.

The real competition to
submarine cables come
from satellites. The
present generation of
satellites provide 25,000
to 40,000 circuits while
the next generation,
Intelsat VI, expected in
1989, will have 120,000
circuits. The cable
technology still has a
future as its capacity
too is increasing rapidly.

UK START FOR NEW
ATLANTIC LINK

Work in Britain on

laying the world's first
transatlantic optical
fibre cable-code named
TAT8-has started. At
Wide-mouth Bay in
Cornwall, the UK shore
end of this £220 million
undersea system is
being installed by staff
from British Telecom
International.

The shore end of the
cable will be floated
ashore from a cableship
secured, and sunk into
position by divers. The
cableship will then
move off to lay the
remainder of the first
12 km of the UK
section of the cable.
Next spring, the main
520 km UK section of
TAT8 will be laid by
BTI's cableship CS Alert.
She will carry out the
laying with the aid of
BTI's remotely-
controlled plough,
which will bury the
cable beneath the
seabed to protect it
from damage by ships'
anchors and trawling.
The UK section of the
cable will be connected
by a further 20 km link
to a special junction
device on the ocean
floor, 540 km south of
Widemouth Bay. This
will join the UK cable to
a similar section from
France, connecting both
to the main 5,000 km
span of the cable to the
USA.

When TAT8 comes into
service next summer, it
will have the potential
capacity to carry the
equivalent of 40,000
simultaneous telephone
calls, or their equivalent
in data, text, facsimile,
graphics, or TV pictures.
TAT8 is the eighth
telephone cable to span
the Atlantic between
Europe and the United
States. Its capacity is
three times greater than
that of all the others

together.

The new cable will form
an important part of a
new global
communications
network, which will
offer customers faster
connections, and
improved quality links
at lower cost. A whole
range of additional
services will be made
possible with the new
digital links.

A second transatlantic
optical fibre cable is
being planned to come
into service in 1991.
Called TAT9, the $400
million system will have
landing points in Britain,
France, Spain, Canada,
and the United States.
The cable's main
transatlantic section
will have the capacity to
carry 75,000
simultaneous phone

The new cables will
help British Telecom to
meet the continuing
growth of the number
of transatlantic phone
calls, which has been
doubling every five
years.

MERCURY SERVICE

THROUGH

VANDERHOFF

Mercury

Communications Ltd, a
wholly owned

subsidiary of Cable &
Wireless PLC, has
appointed Vanderhoff
Business Systems to be
the first distributor for
the Mercury 2200
telephone service. This
uses a Smart Box to
connect customers to
the Mercury network.

The Mercury Smart Box
is installed on the
exchange side of
customers' PABX
equipment. Its purpose
is to work to the
customer's advantage
in deciding when a call
can be more
economically handled
by Mercury and
automatically routeing
it accordingly. Mercury
2200 customers benefit
from call cost savings
of an average of 1 5% on
long-distance
connections and
itemized billing at no
extra charge.

In addition to the
Mercury Smart Box,
Vanderhoff are also
national distributors for
Mercury Paging and are
undertaking the billing ,
of air time to
subscribers.

Further information
from Vanderhoff
Business systems Ltd •
19 Station Approach •
FLEET GUI 3 8QY.

1.21

LOGARITHMIC LCD VU METER

A compact, versatile AF signal level indication unit with a
dynamic range of 60 dB, a dot or bar graph read-out, and a
peak hold function.

Not so long ago, coloured LED
bars were welcomed as the
more robust and faster replace-
ment for moving coil meters in
VU (volume unit) indication
units. An additional, important,
advantage of the LED VU meter
was that it enabled realizing the
peak hold function, which is
useful, if not indispensable, for
determining the recording
level on tapes. The major
drawback of the LED based VU
meter is its relatively high cur-
rent consumption, which poses
considerable problems in port-
able equipment. The VU meter
described here is based on a
liquid crystal display (LCD) with
modest power requirements.
The read-out is logarithmic with
a scale of 60 dB, which is ad-
equate for the dynamic range
of, for instance, a CD player.
The built-in peak hold function
has an option for automatic
reset after approximately 2
seconds. Wire links or jumpers
make it possible to select dot or
bar indication, but it should be
noted that the peak hold func-
tion operates in the bar mode
only.

The proposed LCD VU meter is
composed of 2 units, namely a
logarithmic amplifier and a lin-
ear LC display driver. The
printed circuit boards for these
have the same size to enable

1.22 elektor india January 1988

building a compact indication
unit using a sandwich
construction— see the introduc-
tory photograph and Fig. 1. The
amplifier board holds 2
logarithmic amplifiers for
stereo applications. Both the
amplifier and the display board
can, of course, also work as a
separate module in appli-
cations other than that de-
scribed here: the amplifier, for
instance, is also suitable for
driving a moving coil VU meter,
which is arranged to display a
linear dB scale. Similarly, the LC
display board may be used as
an indication unit in, say, an
electronic thermometer.

The linear LC display

The circuit diagram of this part
of the VU meter is given in Fig.
2. It would have been possible
to use a single display driver
chip with a suitable multiplex-
ing circuit for the LCD but this
would have been at the ex-
pense of the peak hold func-
tion. The inputs of the relatively
expensive driver ICs are pro-
tected against overvoltages by
networks D1-D2-RS and Da-Di-
Re. Selection between the
various available display modes
is accomplished with the aid of
wire links, jumpers or a switch
as summarized in Table 1. The
LCD board has only 4 inputs,

which are readily connected to
the respective points on the
amplifier board— Fig. 3 shows
the completed sandwich con-
struction. The linear scale of
the LCD gives a read-out which
is directly proportional to the
input voltages applied to points
L and R, varying between the
voltage on the respective REF
LO and REF HI input (O.S and
4.5 V). The level of the supply
voltage applied to the LCD
board is governed by the maxi-
mum permissible supply for the
LC display (6 V), and the
minimum supply level for cor-
rect operation of the driver
chips (5 V).

The logarithmic
amplifier

Figure 4 shows the circuit
diagram of 1 of 2 identical
logarithmic amplifiers, and the
power supply for the VU meter.
Opamp Ai raises the input
signal and feeds this to a peak
rectifier circuit. The logarith-
mic amplifier, composed of A2,
A3 and matched transistors T2
and T3, is driven with U(C2),
which is directly related to the
amplitude of the input signal.
The matched transistors are
housed in an IC Type CA3046,

The completed disple

compact as possible.

The linear variation of the recti-
fied input voltage is converted
to logarithmic by means of an
opamp with a feedback circuit
that comprises a conventional
bipolar transistor. Under cer-
tain conditions, the collector
current of a bipolar transistor
rises exponentially with the
base-emitter voltage. Figure S
shows how this phenomenon is
exploited: the transistor forms
the resistance in the negative
feedback circuit of an opamp,
which thus functions as an
amplifier that translates its lin-
ear input signal into a logarith-
mic output.

The voltage transfer of this cir-
cuit is written as

in which a is the current ampli-
fication of transistor T, and kT/q
at room temperature works out
at about ' 26 x 10' 3 . The weak
point of this circuit is that the
term /oo is strongly tempera-
ture dependent. Figure 6 shows
a slightly more complex circuit
whose voltage transfer is less
affected by temperature vari-
ations. The voltage transfer of
this circuit is

The factor kT/q is the same as
in equation [1], while ale o has
been eliminated, ensuring
reasonable temperature stab-
ility. Compensation of kT/q was
found unnecessary for the
given application, since it
proved to have little effect on

: ig. 2 Circuit diagr

the relatively low resolution of
the LCD Returning to the circuit
diagram of Fig. 4, operational
amplifier A4 inverts the
logarithmic voltage, so that the
LC drivers receive a signal with
the correct polarity.

The resolution of the display is
fairly low at 18 bars. The
logarithmic amplifier is dimen-
sioned such that a variation of
the input voltage of 3 decades
results in an output voltage vari-
ation of O.S to 4.5 V. This cor-
responds to 1.33 V per decade.
The full range then cor-
responds to a scale of 60 dB
(-50... +10 dB) as shown in
Table 2 and Fig. 7. Considering
that 0 dB^-775 mV on C2, a
dynamic range of 60 dB means
that the minimum voltage for il-
lumination of the lowest bar is
2.45 mV, which is about equal to
the offset of the input voltage. It
should be noted that the value
of 775 mV on C2 is not related
to the definition of 0 dB as 1 mW
(775 mVims) in a load of 600 O.
The drive margin of the logar-
ithmic amplifier is ensured by
feeding it from the input
voltage for the 5 V regulator,
IC3. Resistors R7 and Rs are di-
mensioned such that the output
voltage of A4 can not rise
above the supply level of the
LCD board.

Construction and
setting up

The components are fitted as
per the directions in the parts
list and Figs. 8 & 9. The LCD
used is the type LTD-321-C01
from Mullard/Videlec. The
outer 2 bars of each row of 20
on this LCD are not used in the
present application. The virtu-
ally symmetrical pinning of the
display, in combination with the
layout of the printed circuit
board, make it possible to fit the
display upside down also. The
contrast of the LCD is maximum
when this is viewed straight, or
from one side. The display is fit-
ted either normally or reversed
—but always at the copper
side— depending on whether it
is to be viewed from above or
below. It is recommended to
use terminal strips for mounting
the LCD Take note of the pos-
ition indicator, which is at the
left side of the LCD when this is
viewed in the normal position,
i.e., facing straight or from
below. The PCB should be held
such that the EPS number is
always upside down. In the nor-

1.24 elektor indie January 1 988

Fig. 4 Circuit diagram of the power supply and 1 of 2 identical logarithmic amplifier channels.

TEST & MEASURING EQUIPMENT

The field of electronic test and measuring equipment is large and still growing. Although
not so long ago even an electronics engineer could get by with a multimeter, an oscillo-
scope, and a signal generator, nowadays even a small laboratory or workshop is
equipped with an array of general purpose instruments, such as multimeters and power
meters, various signal generators, a frequency counter, distortion meter, wave or
spectrum analyser, and one or two oscilloscopes. In many cases, this is complemented
by an LCR meter, Q meter, waveform recorder, a storage oscilloscope, and others.

To help readers find their way in this sometimes bewildering variety of equipment, we
start this month a regular series of reviews of such equipment. Since the oscilloscope,
after the multimeter, is probably the most frequently used instrument in an electronics
environment, the series is started with a review of a number of dual-trace oscilloscopes.
The author of the series is Julian Nolan.

Part 1: dual-trace oscilloscopes (A)

£27.50 each (xlO/xl) it is well
worth considering alternatives
such as the Coline range of
modular probes, which start at
£13.66 (xl); the switchable
xl/xlO version costs £17.84.
high voltages, x 10 probes have
to be used, especially in the
dual trace mode to prevent
over-scanning of the trace.
Although not restricting the
versatility of the instrument, it
can cause a small amount of in-
convenience; a 20V/div range
as fitted to many instruments
would have helped solve this
problem. A xS magnifier con-
trol extends the range of the Y-
amplifiers to 1 mV/div, and, in-
The packaging of the V-212
takes into account the instru-

Table 1. Specification

ELECTRICAL CHARACTERISTICS: - Protection class 1 .

Line voltage: - 1 10,120,220,240 VAC ± 10%. Externally ad-
justable. Power 30 Watts. Line frequency 50,60.400 Hz

MECHANICAL CONSTRUCTION

Dimensions: - W 310 mm. H 130 mm. D 370 mm

Housing: — aluminium sheet

Weight: — approx. 6.5 kg

Y AMPLIFIER ETC.

Operating modes: —

CH 2 alone or inverted

alternate or chopped 1250 kHz! CH 1/CH 2.

CH 1 + CH 2.

Frequency range 0. . . 20 MHz (-3 dBI. Decreases to 7 MHz at
Risetime <17.5 nsec.

Deflection factor 10 steps: 5 mV/div. . . 5 V/div ± 3% extends
to 1 mV/div; by x5 control, increases error by 2%. Min sensi-
tivity 12.5 V/div: variable control; fully anti cw.

Input coupling AC, DC or Gnd.

Input impedance 1 MQ/25 pF; Max input voltage 300 V (peak '
including DC voltage), or 500 Vp-p AC at 1 kHz or less.

X-Y MODE

CH 1 X-axis, CH 2 Y-axis. X Bandwidth DC to at least 500 kHz.
Less than 3° phase shift at 50 kHz.

TIMEBASE

Deflection factor 0.2 trsec/div . . .0.2 sec/div ± 3% with 1/2/5

Expansion x 10, extends max. timebase speed to 20 nsec/div;
expansion error s ± 2% extra.

Uncalibrated control full cw extends range to 0.5 sec/div.
TRIGGERING

Trigger modes: - Auto (bright line). Normal, active TV (line and

Trigger coupling: - AC only.

Trigger sources: - CH 1. CH 2, Alternate Line, Ext.

Triggering slope: - positive or negative, switchable.

Triggering sensitivity: - Internal < 1.5 div at 20 MHz, External
£ 800 mV at 20 MHz, Normal mode.

MISCELLANEOUS

CRT-make Toshiba, measuring screen 100x80 mm,
accelerating voltage 2 kV; beam rotation by front panel

0.5V dp (± 3%L frequency * kHz. 66 ' amP '' IUde appr0 *-
Z modulation 5 Vp-p noticeable modulation: Max input voltage
30 V (DC + peak AC).

CH 1 output at least 20 mV/div to 5 MHz.

Covered by 2 year warranty.

Hitachi V-212

Hitachi is a Japanese company
which is perhaps' best known
for its consumer products, es-
pecially in the video and hi-fi
fields. The V-212 is one of a
comprehensive range of os-
cilloscopes manufactured by
the company, covering from the
V-058G, a dual trace S MHz ultra
compact scope, to units such as
the VC-6155, a 100 MHz DSO.
The V-212, which can be pur-
chased for £320+ VAT, is the
dual trace version of the
cheaper V-211. The accessories
available include carrying
cases, rack mounting kits, and
viewing hoods. High-quality
probes are also available, but at

I J|

Fig. 1. Hitachi Type V212 o:

ment’s very compact design,
and the cardboard box in which
it is packed is, therefore, not
much bigger than the instru-
ment ifself, which is held
securely in place with poly-
styrene cutouts. On inspection,
the Hitachi turned out to be a
relatively small at 310 mm
(W)xl30 mm(H)x370 mm(D):
the absence of the normal
swivel stand adds to its com-
pactness. A small one-position
stand is fitted to the underside
of the instrument to facilitate
tilting, and for those who re-
quire the scope to be easily
portable there is a carrying
strap on one of the sidepanels.
One advantage of the small
stand is that it can easily be
tucked under the scope, thus
making the stacking of other
pieces of equipment above or
below the scope possible. The
V-212 is supplied with a good
length of mains lead, connect-
ing to the scope via a standard
IEC socket. Power consump-
tion is low: only 30 W at 240 V.
Unusually, the scope is also
equipped with a vertical signal
out BNC socket, which pro-
vides at least 20mV/div into
50 Q.

The specifications are shown in
Table 1. From these it can be
seen that the maximum Y ampli-
fier sensitivity is an excellent
1 mV/div, while the minimum is
5 V/div (calibrated) or approx.
12.5 V division (uncalibrated).
When measuring relatively
deed, increases the versatility
of the Y-amplifiers throughout
the range, providing a cali-
brated step outside the stan-
dard 1-2-5 sequence, ie., in a 2-
4-10 sequence. This does how-
ever introduce a ± 2% increase
in Y amp error, bringing the
total to a maximum of ± 5%. Put-
ting this into perspective in
relation to, say, a waveform of
typical total deflection of
40 mm, it may be that with even
a ± 5% Y amp error, a total
deflection error of more than
+ 2 mm is unlikely to be
generated. In the x5 mode,
however, the Y amps are limited
in bandwidth to 7 MHz (-3 dB).
On the whole I did not find this
restriction limiting as the full
bandwidth is still usable at
5 mV, at which sensitivity the Y
amps performed very well at
their maximum bandwidth, be-
ing well inside their -3dB
specified limit. The input amps
also exhibited practically zero
drift durinq their warm ud

TABLE EXPLANATION

TRIGGER FACILITIES— The triggering facilities offered by the
scope, eg alternate triggering, TV sync, auto trigger, etc.

TRIGGER PERFORMANCE— Is an indication of how well and
easily the scope triggers on a wide variety of waveforms, as well
the maximum triggering frequency.

CRT BRIGHTNESS— This is an indication of the brightness
available on a fully triggered waveform at the maximum deflec-
tion speed. Note: some scopes have internal brightness presets,
setting the maximum and minimum brightness; this is not taken
into account.

CRT FOCUSING— The standard of the focusing over the whole
range of deflection speeds and display modes.

Y-AMP PERFORMANCE— An indication of the maximum sensi-
tivity of the Y-amp, along with its performance across the band-
width.

INTERNAL CONSTRUCTION— This rating assesses the scope's
internal construction, the main criterion being the quality of the
PCBs and other components, the general nearness and layout
with a view to servicing and the mechanical robustness.

EXTERNAL CONSTRUCTION— The strength and quality of the
materials used, along with the finish are among the criteria here.

OVERALL SPECIFICATION— This takes into account other
features which may be provided on the scope, such as trigger
hold-off or a third channel, as well the general specification of
the scope.

EASE OF USE— This assesses the general layout of the controls,
and ease of use for a first time user, and not the ease of oper-
ation of the range switches etc.

MANUAL— Takes into account the actual information included
in the manual which is likely to be useful to the user.

period making instant measure-
ments easier.

The vertical modes of the V-212
are fairly standard, including
alternate and chopped
(250 kHz) modes for dual trace
operation. Only one channel (2)
of the V-212 is invertable for sub-
traction purposes, this being
implemented, as are some of
the other functions, by pulling
an associated control (in this
case CH 2 position) to its out
position. This does have advan-
tages in that it helps provide an
uncluttered layout, but it also
means that when this 'second-
ary' function is operated, it is
very easy to offset the 'primary'
function from its original value.
Triggering on the Hitachi is of a
very high standard, incor-
porating the unsual feature of
an alternate channel triggering
mode. This permits stable, fully
triggered traces to be pro-
duced in either dual trace
mode from two non-synchron-
ized sources, as each channel is
triggered independently. This
is invaluable for taking
measurements where more
than one signal source is being
used within a circuit, and is also
helpful for single trace
measurements, enabling the
stable display of either channel
without having to manually alter
the triggering channel. Active
TV frame and line triggering
are also provided on the V-212,
making triggering on video
signals an easy task. The per-
formance of this was good, trig-
gering even at very low levels
and over an acceptable range
of line and frame frequencies.
Two notable exceptions from
the V-212's triggering facilities
are HF and LF coupling, and
although it is possible to get
around this problem when
these functions would normally
be required by fine adjustment
of the triggering threshold, the
necessary filters would have
made operation easier. Selec-
tion of the triggering criteria is
made by a number of lever op-
erated switches, making for
fast, reliable and convenient op-
eration of the scope. Trigger
sensitivity was satisfactory at
5 mm internally and 200 mV ex-
ternally in the 20 Hz to 2 MHz
range, increasing to 10 mm in-
ternally and 800 mV externally
in the 2 MHz to 20 MHz range.
Generally the triggering per-
formance was very good, with .
the alternate triggering being a ;

mally only found on models
outside this price range. A
stable trace was produced in
nearly all cases; the trigger
threshold control did, however,
prove to be sensitive and it was
very easy when pulling this
control out (for triggering on
the trailing edge of a signal) to
offset it outside the triggering
threshold, thus causing the
timebase to free run, producing
an unlocked trace.

Maximum timebase speed is
200 ns/div; this is however ex-
tendable to a maximum deflec-
tion speed of 20 ns/div (not
100 ns/div as stated in the
manual) by means of a x 10 con-
trol, although naturally this is at
the expense of trace intensity.
Speed selection is by means of
a 19-position rotary switch, the
minimum speeds being 0.2 s/
div (calibrated) or roughly
0.5 s/div (uncalibrated). On the
maximum deflection speed of
20 ns slight defocusing occurs
towards the end of the trace,
which is unfortunate, because
for the remaining speeds focus-
ing from the Toshiba tube is ex-
cellent for a 2 kV acceleration
voltage. Despite this, the per-
formance of the scope in this
area is particurly good, many of
its rivals not offering a 20 ns/div
sweep speed, although, as I
have said, accurate measuring
over the last third of the trace at
this speed is limited by the
2 mm wide trace over this area.
The screen itself is filtered a
light blue and has full gradua-
tions for risetime measurement.
The V-212 is equipped with Z-
modulation and CH 1 vertical
signal out facilities; the BNC
connectors for both these func-
tions are mounted on the back
panel. For noticeable intensity
modulation a 5 V p-p signal is
required, the input bandwidth
for this function going up to
2 MHz. The CH 1 output on the
other hand provides a buffered
output from channel 1 which
could be used to drive, for
example, a counter/timer, thus
providing an accurate readout
of frequency, etc.

Aluminium plays an important
part in the V-212’s construction,
both the outer housing and
frame are manufactured from
this, which contributes to the
scope's light weight of 6.5 kg.
Plastic is used for the front
fascia surround, and this could
prove to be fragile, especially
around the top corners if the
scope is used in rugged con-

1.28 elektof India jenuary 1988

Fig. 3. Internal view of V212

ditions. Robust feet/cable
holders are featured on the rear
panel and protect the instru-
ment to a large extent from any
damage which may occur if, for
example, the instrument is
dropped while being carried.
In contrast to many other
scopes, all the controls have a
very positive and fairly light ac-
tion, making for easier, more
precise operation. Some, how-
ever, notably the Y amplifier
fine controls, protrude a good
distance from the front panel,
making accidental damage
more likely in the event of a fall.
My only major criticism of the
Hitachi, if it can be called that,
is the internal construction. The
main circuitry is mounted on
two PCB’s of equal size, but
larger components, such as
voltage regulators, etc., are
mounted on the chasses itself
for good heat dissipation. This
wide variety of mounting points
coupled with the three remain-
ing PCB's housing the tube
base, etc., necessitates the use
of a large number of wire con-
nections and links, giving the
inside of the Hitachi an appear-
rence not dissimilar to one of
the company's tapes. All of the
interconnections appear to be
of a very high quality, however,
and I have been assured by
Hitachi that the number of inter-
connections in no way affects
the reliability of the scope. This
is proved by the fact that Hitachi
oscilloscopes using the same
construction technique are of-
fered for hire by some of the
electronic equipment rental
companies, where reliability is
obviously at a premium.
Ignoring the number of inter-
connections, internal construc-

tion was generally good; the-
large number of connections
making the mounting of all high
power dissipation components
on the subframe possible. The
internal construction itself is ex-
tremely compact: the two main
PCBs are mounted horizontally
above one another at the front
of the instrument. Unlike the Y
amplifiers, the EHT section of
the circuit is completely
shrouded, thus helping to pre-
vent the build up of dust, as
well as helping to prevent any

possible shock should be outer
housing be removed.

Not surprisingly, most of the
semiconductors are manufac-
tured by Hitachi themselves;
other components come from a
variety of manufaturers and are
fairly standard, ranging from
miniature resistors to the in-
dustry standard 78 and 79 series
monolithic fixed voltage
regulators.

The 56 page manual contains a
number of detailed sections,
among which how to set up to
scope initially, and a particu-
larly good section on measur-
ing procedures. There are no
sections on calibration or ser-
vicing, and the roughly A5 size
of the manual makes the circuit
diagrams small and and in
place difficult to understand as
they are spread out over a num-
ber of pages. There is also no
circuit description. Overall,
although containing some good
sections, the manual missed out
on several important points and
could have been accurately
summarized in a considerably
shorter space.

Conclusion

The Hitachi V-212 is generally a

Other Hitachi scopes under £1000
20 MHz

V-222: As V-212 plus alternate magnify, swivel stand, scale illumi-
nation, uncal. indicators. Probes are also included. £395+ VAT.

V-223: As V-222 plus sweep delay, 1 /isec to 100 msec. £450 +VAT.

V-225: As V-223 plus on-screen cursor measurement of voltage
and time difference. £550+VAT.

40 MHz

V-422: As V-222 plus signal delay line, 12 kV accelerating
voltage. £580+ VAT.

V-423 and V-425: As V-223 and V-225 respectively, but with in-
creased bandwidth. V-423: £650; V425: £695.

60 MHz

V-650F: Similar to V-422 + dual timebase, trigger view, delay
multiplier: £780+VAT.

PORTABLE

V-209: 1 mV sensitivity 3.5” tube, lightweight miniature format,
battery/mains, NiCd batteries included : £680+VAT,

well-thought out scope, with
some advanced features, and is
competitively priced at
£320+ VAT. Triggering is par-
ticularly good, having an alter-
nate triggering facility and this
coupled with the scope's ex-
cellent CRT, which is one of the
best 2kV tubes I have seen,
make it well worth looking at.

The scope’s small size also I
makes it eminently suitable for
those users who include por-
tability high on their list of
priorities. It does have one or
two minor shortcomings, such
as its internal construction,
which, although of a fairly high
. standard, does possess a large
I number of interconnecting

wires, which could make ser-
vicing difficult. However, I am
quite happy that they will in no
way affect reliability. The
manual is not really up to stan-
dard, despite its length, pro-
viding only the initial 'set up' in-
formation, which admittedly is
j good. Summing up, the V-212
should represent a good choice

for most users who need a flex-
ible scope for a wide variety of

The Hitachi V-212 was supplied
by Hitachi-Denshi (U.K.) Ltd •
13-14 Garrick Industrial Centre
• Garrick Road • Hendon •
London NW9 9AP.

Crotech 3133

The company of Crotech was
formed in 1981, and now
designs a wide range of test
equipment from frequency
counters to signal generators.
The 3133 is one of a range of six
oscilloscopes manufactured by
the company. The range ex-
tends from the single trace 3031
at £199 to the 3339 which
features a 30 MHz bandwidth,
as well as a VDU mode, en-
abling the scope to act as a
monitor, at £570. The new 3133
is priced at a competitive £319.
The 3133, which replaces the
3132, is unique in its price range
in that it incorporates a compo-
nent comparator and a power
supply outlet in its design, and
has a bandwidth of 25 MHz
(-3dB), Probes are also sup-
plied, but these are of the
'crocodile clip' xl design, so
their usefulness for RF work is
limited. A xl/xlO probe may
be purchased as an optional ex-
tra, along with a light hood and
trolley.

The 3133 is somewhat unusual

in its layout, with the CRT
situated in the centre of the
scope and the Y-amp and
timebase/triggering controls
positioned at either side of it.
This gives the scope the
average size of 330 (W)x395
(D) mm, although the height is
somewhat higher than normal at

165 mm. The weight of the 3133
is also on the somewhat heavy
side at 8.5 kg. A three position
swivel stand is Fitted, which,
given the external graticule of
the tube, is just as well, since it
enables the scope to be pos-
itioned to minimize the small
parallax error. Mains connec-

tion is by means of a fixed lead, I
ie., no socket, which is a pity,
since it is of only average length
so that in some cases it may be
necessary to extend its length.

As I have already mentioned,
the 3133 incorporates some
rather unusual features, these in
the main being the power
supply, component comparator
and the more common trigger j
hold-off facility.

The front panel layout is fully
colour coded, and this should
make first time operation no
problem, as well as contribu-
ting very significantly to the
scope's ease of use. Most of the
functions are selected by a
series of push-button switches,
which are arranged in four
groups: CH 1 input coupling; '
CH 2 input coupling; Display
mode; and trigger functions
etc. While these provide an eas-
ily identifiable, and in some
ways more flexible, method of
function selection, I found that
operation is perhaps slightly
more time-consuming than the
more usual 'slider' type
switches.

ELECTRICAL CHARACTERISTICS

Line voltage: - 115,220,230,240 VAC. internally adjustable.
Power 40 Watts. Line frequency: 27-65 Hz.

MECHANICAL CONSTRUCTION

Dimensions: — W 330 mm, H 165 mm, D 395 mm

Weight: - approx. 8.5 kg

Y AMPLIFIER ETC.

Operating modes: —

CH 1 alone.

Inversion capability on CH 2 only.

Alternate or chopped (120 kHz) CH 1/CH 2.

CH 1 + CH 2.

Frequency range 0 . . .25 MHz (-3 dB).

Deflection factor 12 steps; 2 mV/div. . . 10 V/div ± 3%; no vari-
able attenuation controls.

Input coupling AC, DC or Gnd.

Input impedance 1 MQ/25 pF; Max input voltage 400 V (DC +

TIMEBASE

Deflection factor 0.2 ysec/div . . .0.5 sec/div ± 3% with 1/2/5
divisions.

Expansion x 5. extends max. timebase speed to 40 nsec/div (vari-
able control fully anti cwl, expansion error s 2% extra; typical
variable control error ± 2%.

TRIGGERING

Trigger modes: — Auto (bright line); Normal; active TV (line and

Trigger coupling: - AC. DC, HF reject.

Trigger sources: - CH 1, CH 2, Line. Ext.

Triggering slope: — positive or negative, switchable.

Triggering sensitivity: - Internal < 0.5 div at 25 MHz, External <
1 V at 25 MHz, Auto mode.

MISCELLANEOUS

CRT-make NEC, 13 cm front faced round tube (viewing area
approx. 100x80 mm); accelerating voltage 2 kV, beam rotation
by front panel adjustment.

Compensation signal for divider probe, amplitude approx. 0,2 Vpp
(± 3%). frequency 1 kHz.

Z modulation 20 Vp-p for complete blanking (— ).

Power Supply: 5 V at 1 Amp, +/-12 V floating at 200 mA

X-Y MODE

CH 1 Y-axis. CH 2 X-axis. X Bandwidth DC to 1 MHz (-3 dB).
Phase shift at 50 kHz s3°.

Component Comparator: — test voltage 8.6 V r.m.s., test current
28 mA max; line frequency = test frequency.

Covered by 2 year ’Blue Chip’ warranty.

1.29

The Y-amplifiers, which are
positioned to the left of the
tube, surprisingly have a band-
width of 25 MHz: 5 MHz more
than the 20 MHz offered by its
direct competitors. Perform-
ance of the Y-amps is certainly
good, meeting the 25 MHz
bandwidth well inside its -3 dB
limit. The 2 mV/div maximum Y-
amp sensitivity is effective
across the whole bandwidth,
allowing accurate measure-
ment of low amplitude RF
signals. This range extends up
to a useful 10 V/div. I found cali-
bration accuracy on all of these
ranges very good, and well
within the quoted + 3%. It is a
pity, however, that both Y-
amplifiers have no variable con-
trol. This among other things
makes accurate risetime
measurements difficult, unless
the deflection amplitude of the
signal matches that of the
risetime graticule. Both Y-amps
have a 14 ns risetime to accom-
modate their wider than usual
bandwidth and this does, of
course, help in giving more ac-
curate high frequency pulse
deflection representations than
the more common 17.5 ns
risetime. This reduced risetime
is largely due to the use of
faster FETs in the input stage
and in my view is well worth the
trouble, not only having the ad-
vantages outlined above, but
also that at 20 MHz the attenua-
tion is way below the -3dB
level, enabling more accurate
vertical measurements to be
made across the whole upper
bandwidth.

The display modes on the 3133
are fairly standard, with the ex-
ception that in single trace
mode only CH 1 can be dis-
played, instead of the more
usual switchable CH 1/CH 2 op-
tion. This is certainly not a
major setback, but it can entail
a certain amount of lead swap-
ping, or trace repositioning, if,
for example, it is necessary to
display a signal connected to
CH 2 for a full 8 cm vertical
deflection amplitude. A 1kHz
200 mV (± 2%)p-p divider
probe compensation square
wave output is provided.

An ever increasingly popular
feature is the trigger hold-off fa-
cility, which is now finding its
way into the 'under £350' price
bracket. This, along with the in-
crease in bandwidth and
slimline appearence, is one of
the main differences between
the new 3133 and the older 3132.

1.30 elektor india January 1988

Trigger hold-off facilitates I
stable triggering on complex
and irregular waveforms, and as J
such is useful for displaying, for I
example, complex pulse trains |
in digital work over a wide
range of timebase speeds. The i
3133’s hold-off facility coped
with a wide variety of timebase |
speeds and waveforms, ranging
from a simple double pulse to a
complex pulse train. Other trig-
gering functions include the
more standard HF reject and TV
synchronization. Triggering
performance is good for- the
vast majority of waveforms.
When the scope is in auto
mode and the TV frame sync is
in operation, however, it is diffi-
cult to lock on to the frame sync
pulses during a steady video
signal; a changing video signal I
with a low signal content makes
this next to impossible. No
problems were encountered in
the line sync mode and reliable
TV (both frame and line) trig-
gering was present in Normal
mode. AC and DC coupling and

Normal and Auto modes are
also provided, making trigger-
ing effective across a wide
range of signals. Alternate, or
Vertical triggering, is not a
feature of the scope, and conse-
quently non-synchronized
waveforms cannot be stably
displayed on both traces.
Triggering sensitivity is very
good, typically being 2 mm up-
to 25 MHz internally, which is
well inside the 0.5 div deflec-
tion quoted, or approximately
700 mVp-p externally, again
well inside the quoted 1 Vp-p.
To obtain these sort of sen-
sitivities, fairly critical adjust-
ment of the triggering
threshold is, however, required,
although triggering on the
quoted sensitivities is more eas-
ily accomplished.

Timebase speeds range from
0.2secs/div to 0.5 »secs/div;
the maximum speed being in-
creased to 200 nsec/div by the
use of a variable control. Cali-
bration accuracy of the
timebase is ± 3%, the variable

control, when fully clockwise,
adds about 2% to the error. A
x5 control is provided, which
increases the maximum deflec-
tion speed to 40 nsec/div and
brings the maximum error at
this speed to approximately 7%,
which I found acceptable for all
tests carried out on the scope.
The maximum sweep speed of
40 nsec/div gives a 1 division
horizontal resolution for a
25 MHz sine wave and should
be enough for most purposes.
The 3133 is one of the few
scopes which still use an exter-
nal graticule CRT. On the 3133,
parallax error is kept to a
minimum by sticking the
graticule template directly onto
the CRT, and, although a small
parallax error is obviously still
present, I found that the extra
measuring error incurred when
taking measurements is practi-
cally zero, if the screen is view-
ed from a constant angle. The
external graticule does, how-
ever, slightly obscure the trace
along its markings to a small ex-
tent, and in some circum-
stances it may be necessary to
slightly alter the viewing angle
to clearly observe the whole of
a low intensity trace. The 2 kV
CRT itself is round and because
of this the trace cannot be ob-
served at the comers of the
viewing screen. However,
under normal conditions, this in
no way affects the measuring
capability of the instrument, as
most measurements are taken
at or around the centre of the
screen. It may, however, slightly
affect dual trace operation,
causing a small adjustment in
waveform amplitude or position
on, for example, a pulse
wavetrain, where viewing of the
initial leading edge could
otherwise be partly obscured.
Automatic focusing is not incor-
porated, and consequently a
small adjustment is necessary
when, for example, changing
deflection speeds from
50 msec/div to 40 nsec/div in
order to maintain the optimum
focus of the trace. The focusing
of the CRT at low to medium in-
tensities is quite good, although
at higher intensity's slight
defocussing did occur,
although with the good
brightness available this is not
surprising. Despite this, the
tube's performance on the
focusing side does not quite
match that given by some of the
better 2kV internal graticule,
rectangular tubes. The CRT is

protected by a deep blue
plastic faceplate and is
mounted in a bezel which also
has camera mounting cut-outs.
The cost saving on the external
graticule tube allows extra
features, such as the power
supply, to be incorporated. This
has three outputs which consist
of a negative ground S V 1 Amp
supply, suitable for driving TTL
etc., and to floating ground out-
puts which can be configured
as ± 12 V (200 mA each), +24 V
or -24 V supplies, suitable for
driving a whole host of devices
from op-amps to CMOS logic.
This facility should prove useful
to most users, even those who
already have their own power
supplies, mainly because in
contrast to the average power
supply, with perhaps 1 or 2
supply rails, the 3133 has 3,
already configured to supply
simultaneously both analogue
and digital circuitry. For those
users who already have a com-
prehensive power supply, this
feature may be of more limited
use, but I feel still worth while.
The component comparator
consists of two component
testers, which generally display
a V-I type curve of the compo-
nent under test. The test signal
is an 8.6 V r.ms. sine wave,
which produces, for example, a
sharp right angle for a typical
diode, or ellipse for a capacitor.
Although it does not provide
any accurate information as to
the component’s value, it does
provide a very clear indication
of whether the component is
operational, if it is, for example,
’leaky'. Component com-
parison is also possible with the
3133 two testers, enabling a
known good device to be ac-
curately compared with other
examples. It is also possible to
compare complete circuits with
this technique, each circuit ef-
fectively having its own
'signature'. Initially, I was a little
sceptical of the component tes-
ter, mainly because I was un-
sure if its usefulness, in view of
the fact that the vast majority of
scope users possess a mul-
timeter. This opinion was, how-
ever, quickly changed by the |
component tester, which j
proved to provide a quick and I
very clear method of both
testing and comparing compo-

1 CATEGORY

£5

Ooo,

. -

nents, allowing.the user in most
| cases to see their actual charac-
| teristics.

Both the internal and external
| construction are of a very high
j standard. Internal construction
| is based around a relatively
i large number of PCBs, totalling
j seven in all. The timebase, Y-
j amplifiers, power supply, etc.,
are all mounted on different
[ boards, thus making servicing
greatly easier. All the PCBs are
silk screened with the various
component identification
numbers, and, where appro-
: priate, their function. Both the
| attenuator stage in the Y-
amplifiers and the EHT section
are fully shrouded, as is the
! CRT. The components them-
; selves come from a wide var-
| iety of sources and all appear to
be of a good quality. All internal
j wiring is neatly grouped, giv-
ing the inside of the scope a
! very neat appearance. External
j construction of the scope is to
the same high standard, being
| almost completely aluminium.
This also includes, unusually,
the front panel, which is silk
screened with the appropriate
markings. None of the front
panel controls extends beyond
the display bezel, which further
increases the robustness of the
scope. With the construction in
mind, it is not surprising to 1
learn that among the users of
the 3133’s predecessor, the
3132, are British Nuclear Fuels,
GEC, UK AEA and several large
industrial companies.

A comprehensive manual and a
book entitled Getting The Best
From Your Scope are included
with the 3133. Both are very
good, the manual covering in-
itial setting up, servicing and j
calibration, while the book
deals with a wide range of ap-
plications, including TV servic-
ing. The manual also includes a !

full circuit diagram, as well as
diagrams of both mechanical
construction and PCB layout.

Conclusion

The Crotech 3133's extra func-
tions and higher than normal
bandwidth turn what otherwise i
would perhaps be an unexcep- |
tional scope into one which is I
well worth looking at, es-
pecially when the price of £319
is taken into account. While the ,
CRT gives a reasonable per-
formance, its external graticule
can make accurate measure-
ments slightly more time con- I
suming. It is probable, however,
that the extra bandwidth and
functions offered by the 3133
over its rivals will be worth this
to the many users who require a
scope which can be used for a J
large number of applications.
The high standard of construe- I
tion is also one of the 3133's I
assets. The 3133 is particularly |
suited to new users of scopes,
as it is particularly easy to
operate and it is supplied with
two good manuals. To sum up,
the 3133 certainly represents !
value for money, offering as it i
does a number of useful extra
functions and a reasonable per-
formance, while maintaining a i
very high standard of construc-
tion. If you require a versatile j
scope, with a wide range of
features along with good con-
struction quality, I can certainly
recommend it.

I have been informed by
Crotech that they intend to im- j
prove the TV triggering per- J
formance of the 3133; the review I
model was a pre-production ■
prototype

The Crotech 3133 was supplied
by Crotech Instruments Ltd,, 2, J
Stephenson Road, St. Ives, Hun-
tington, Cambridgeshire PE17
4WJ. Tel. (0480) 301818

Other Crotech

DUAL TRACE

3132— Preceding model to 3133,
main differences 20 MHz band-
width, no trigger hold-off,
design. Currently £285+ VAT.

3337—30 MHz version of 3132,
main differences 10 kV ac-
celeration voltage, no compo-
nent tester, signal delay. Cur-
rently £425+ VAT.

3339-Same as 3337, except
VDU mode facility and the ad-
dition of a component tester
and power supply. Currently
£570+ VAT.

SINGLE TRACE
3031 and 3032— single trace,
20 MHz, component tester, 3031
9.5 cm rectangular tube, 3036
13 cm round tube. Currently
£199 and £220 respectively
(both +VAT).

Next month, Julian Nolan
reviews the Gould OS300 and
the Grundig MO20 oscillo-
scopes.

PHILOSOPHISE NATURALIS
PRINCIPIA MATHEMATICA

or

MATHEMATICAL PRINCIPLES
OF NATURAL PHILOSOPHY
by

ISAAC NEWTON
1687 - A TERCENTENARY
CELEBRATION - 1987

by Dr. T.R. Carson, University of St. Andrews, Department of Physics & Astronomy.

Isaac Newton was born on 25
December 1642 in the manor-
house at Woolsthorpe, near
Grantham, Lincolnshire. He
died on 20 March 1727 at Ken-
singon, London and was buried
in Westminster Abbey. Thus he
lived under seven monarchs, as
well as two protectors, in what
can surely be described as an
age of revolution. Against this
politically turbulent back-
ground the world of learning
was undergoing, after a simi-
larly turbulent start, its own
albeit quieter evolution. The an-
cient philosophy of Aristotle,
despite the efforts of Aquinas,
had already sunk into decline.
Of the three Philosophies,
Metaphysical, Moral and
Natural, the latter was poised
for its most dramatic develop-
ment. Man's place in the
physical universe had been
redefined by Copernicus and
Bruno. Bacon and Galileo had
initiated a new science, based
on observation and mathemat-
ically precise description, so
immediately exemplified in
Kepler's three laws of planetary
motion. The most influential
philosopher of the seventeenth
century was Descartes, whose
attempt to construct an all-
embracing philosophy of the
world, failed even to resolve his
own conflict between reason
and authority. Nevertheless it
had a lasting impact on the

1.32 uleklor India January 1988

future development of natural
philosophy through its re-
duction of all reality to matter
and motion. Newton's "Prin-
cipia” represented the next
step along this road. Matter was
invested with certain intrinsic
properties, both active and
passive, while motion became a

series of events in space and
time subject to quantitative
analysis based on premises of
cause and effect. Later on the
combination of Descartes'
analytical geometry and
Newton’s differential and inte-
gral calculus would become
powerful tools in forging a com-

plete mechanistic philosophy.
Due to the death of his father
two months before his birth,
Newton spent his early years
with his maternal grandmother
in Woolsthorpe. In 1654 he
entered the grammar school in
Grantham, but left in 1656 to
help manage the family farm,
returning to school in 1660 to
prepare for college for he
showed a remarkable precocity
in mathematics. In 1661 he
matriculated at Trinity College,
Cambridge, where he became
a scholar in 1664 and graduated
B.A. in 1665. He became a
fellow of Trinity College in 1667
and in 1669 was elected Luca-
sian professor of mathematics
in succession to Isaac Barrow
whom he had impressed as "a
very ingenious person" and "a
man of exceptional ability and
remarkable skill". He was
elected to fellowship of the
Royal Society in 1672 and
represented the university in
parliament in 1689 and in 1701,
and was finally appointed to the
post of Warden of the Mint in
1696 and Master in 1699. In 1703
Newton became president of
the Royal Society, which office
he retained for life. He was
knighted by Queen Anne on
the occasion of her visit to Cam-
bridge in 1705.

During the years 1665-1666, at a
time of enforced absence from
Cambridge due to the plague,

at Woolsthorpe, Newton made a
number of advances in optics,
mathematics, mechanics and
gravity. It was mainly with the
last three topics that the "Prin-
cipia” would be later concern-
ed, but it was during this rural
retreat that the seeds of that
bountiful harvest were sown.

Newton himself wrote later "...
from Kepler’s rule of the
periodical times of the planets
[Kepler’s third law] ... I de-
duced that the forces which
keep the planets in their orbs
must be reciprocally as the
squares of their distances from
the centres about which they
revolve: and thereby compared
the force requisite to keep the
Moon in her orb with the force
of gravity at the surface of the
earth, and. found them answer
pretty nearly. All this was in the
two plague years of 1665 and
1666 ... for in those days I was in
the prime of my age for inven-
tion and minded Mathematics
and Philosophy more than at
any time since . . . between the
years 1676 and 1677 I found the
proposition that by a centrifugal
force reciprocally as the square
of the distance a planet must
revolve in an ellipse about the
centre of force as focus
[Kepler’s first law] . . . and with a
radius drawn to that centre de-
scribe areas proportional to the
times [Kepler's second law]".

Christian Huygens had already
published in 1673 the rule of
centrifugal force for uniform
circular motion. What Newton
did was to define the concepts
of quantity of motion (momen-
tum) and force, and the laws
relating to them. He also made
the conceptual move from cen-
trifugal to centripetal force and
generalised from the circle to
the ellipse, having already
postulated the universality of
the gravitational force on the
falling terrestrial body and that
acting on the Moon and other
heavenly bodies. The story of
the apple falling from the tree
in the garden at Woolsthorpe
was told by William Stukely in
recounting his conversations
with Newton in 1726, and also
by Voltaire who obtained it from
Newton's step-niece. The tree
was cut down in 1820 but a por-
tion of the trunk may be seen in
the library of the Royal
Astronomical Society in Bur-
lington House, Piccadilly.

The events leading up to the
publication of the "Principia”
began with the visit to Newton

elektor mdia January 1988 1 .33

PHILOSOPHIZE

NATURALIS

PRINCIPIA

MATHEMATICA

NEWTON, Tria. Cdl. C.aub. Soc. Matlicfcos

lore Lucafuno, & Socictatis Rcgalis Sodali.

I

MPRIMATUR-

S. P

E P Y S, PR/ESES.

JM 5 . i486.

CO N D INI,

Juffii Sir null

•t RtgU ac Tv pis TofiiJii Simicr. Profile apud

plur.

cs Bibliopotas. Amo MDCLXXXVII.

illustrissima:
SOC1ETATI REGALI

a Scrcnifliino

REGE CAROLO II

A D

PH1LOSOPHIAM PROMOVENDAM

FUNDATjE

ET AUSPICIIS

POTENTISSIMI MONAR.CH/E

JACOBI II

FLORENTI.

Tradjtumhunc humillimc D. D. D.

J s. NEWTON.

in 1684 of Edmund Halley (soon
assistant secretary of the Royal
Society and editor of Philo-
sophical Transactions) to pose
the question, prompted by a
discussion with Robert Hooke
and Christopher Wren, as to
what orbit a planet would follow
if attracted to the Sun by a force
varying inversely as the square
of the distance. Halley, im-
pressed by Newton’s im-
mediate answer, asked for the
proof, which Newton sent and
was received by Halley with
such great satisfaction that he
visited Newton again to discuss
the matter. He reported to the
Royal Society the "curious
treatise, De Motu (On Motion)”
which Newton had promised to
send to the Society. This was re-
ceived in February 1686,
Halley’s intention being to
secure the position until
Newton could publish his work,
as he was encouraged to do by
Halley and by the Royal Society.
In April 1686 the Royal Society
received a manuscript, in the
hand of namesake and ama-
nuensis Humprey Newton, of
what Halley referred to as an
"incomparable Treatise on Mo-
tion" entitled "Philosophiae
Naturalis Principia Math-
ematica" and dedicated to the
Society by Newton. This was in
fact the first part of the ’’Prin-
cipia", comprising the "Defini-
tions", "Axioms or Laws of Mo-
tion” and "Book I — On the Mo-
tion of Bodies”, bearing the full ;
title of the whole work. The
Society resolved to have tl.e
manuscript printed without
delay at its own expense, and
furthermore entrusted Halley to
supervise the printing. For
financial reasons the Royal
Society shortly ordered that
Halley print it at his expense
which he engaged to do. In
June 1686 Newton informed
Halley that he had intended the
"Principia" to consist of three
books, of which the third would
concern the system of the
world, which he now proposed
to suppress because "Philos-
ophy is such an impertinently
litigious Lady that a man had as
good be engaged in Law suits
as have to do with her”. Newton
realized that the title of the
whole work would no longer
be as appropriate, considered
changing it, but on second
thoughts retained the former ti-
tle to help the sale of the book.
Halley begged Newton ’’not
to. . .deprive us of your third

book”, adding that it would
make the "Principia" accept-
able to "those that will call
themselves philosophers with-
out mathematics, which are by
far the greater number".
Newton deferred to Halley and
duly delivered to him "Book II
— On the Motion of Bodies in
Resisting Media" in March 1687
and "Book III — On the System
of the World" in April 1687. On
5 July 1687 Halley wrote to
Newton that he had "at length
brought your book to an end,
and hope it will please you”.
Halley had written a latin ode, •
dedicated to Newton, with
which he prefaced the work. In
his own preface Newton paid a
glowing tribute to the assist-
ance which Halley had given
him. The title page bore the
"imprimatur” of Samuel Pepys,
President of the Royal Society.
The number of copies printed
is unknown but has been
estimated as high as four hun-
dred. Newton received twenty
for himself and forty for
disposal through booksellers.
The price to the trade was six
shillings in sheets, reduced to
five shillings for cash, but nine
shillings leatherbound and let-
tered!

News, emanating from Halley
and John Flamsteed (first
Astronomer Royal), of the im-
pending appearance of the

"Principia” had generated
much excitement Reactions to
the book were quick to follow
publication. Two reviews ap-
peared in French (Journal des
Scavants, Bibliotheque Univer-
selle) the latter being attributed
to John Locke, one in Latin (Acta
Eruditorum), and one in English
(Philosophical Transactions) by
Halley. Readers were left in no
doubt as to the scope and scale
of Newton’s achievement.
Newton’s work appealed par-
ticularly to mathematicians like
James Gregory (St Andrews and
Edinburgh) and his nephew
David Gregory (Edinburgh and
Oxford). Perhaps the first con-
tinental student of Newton was
Nicolas Fatio de Duillier, a
Genevese mathematician who
was instrumental in spreading
news of the "Principia" to
Huygens in Holland and to
Leibnitz, otherwise known for
his controversy with Newton re-
garding the calculus, in
Germany. An early casualty was
Descartes' philosophy, particu-
larly as it applied to mechanics,
including his theory of vortices
relating to celestial motions.
However, to Newton the con-
cept of action at a distance with-
out mediation was an absurdity,
a point of some importance
when considering the later rev-
olution due to Einstein. Newton
also made it clear that while in-

voking gravity as a cause of
(change of) motion, he was
making no statement regarding
the cause of gravity itself and
permitted himself but one ref-
erence to God in the first edi-
tion. Richard Bentley, Master of
Trinity College, in his Robert
Boyle Lectures (1692), noted that
the dispositions of the planets
relative to the Sun were critical
for the sustenance of life
thereon, leading him to
"discern the tokens of Wisdom
in the placing of our Earth”.
George Berkeley, Bishop of
Cloyne, attacked Newton's con-
cepts of absolute space, absol-
ute time and absolute motion as
inadmissible since they enter-
tained "something besides God
which is eternal, uncreated, in-
finite, indivisible, unmutable".
Joseph Addison too upheld the
thinking of Descartes, although
both Berkeley and Addison
would later publish defences of
the Newtonian philosophy.
Leibnitz considered that gravity
"without any mechanism. . . or
by a law of God... without
using any intelligible means,
... a senseless occult qual-
ity...". Roger Cotes (first Plu-
mian Professor of Astronomy),
editor of the second edition
(1713) of "Principia" under
Bentley’s supervision, advised
Newton to counter the criticism
of Leibnitz. For the second edi-

tion Newton thus prepared the
famous General Scholium con-
taining the sentence ”. . .And
thus much concerning God: to
discuss of whom from the ap-
pearance of things, does cer-
tainly belong to Natural
Philosophy. . .”. Herein too is
found the famous declaration
”. . .hypotheses non fingo. . . (I
frame no hypotheses)”, which
must be taken only in the con-
text of the cause of gravity, for
Newton framed many hypoth-
eses. The third edition (1726)
was prepared for Newton by
Henry Pemberton who also, a
week after Newton’s death, an-
nounced a translation of the
"Principia”. This was never
published and the first English
translation was that of Andrew
Motte in 1729. Fatio was the
author of the epigram on
Newton’s tomb: "Sibi gratulen-
tur Morales, Tale tantumque
extitisse Humani Generis
Decus (Let mortals rejoice that
there has existed such and so
great an ornament of the human
race)”. Amongst the many
tributes that have been ac-
corded Newton’s "magnum
opus" few are as generous as
that of Laplace in referring to
the causes "which will always
assure the "Principia" a pre-
eminence above all the other
productions of the human in-
tellect".

stereo pan pot

This circuit offers the possibility of stereo
image width control from stereo, through
mono, to reverse stereo. The circuit com-
prises two emitter followers and a linear
stereo potentiometer.

If x is the ratio of the resistance between the
sliders of the pots and the lower ends of the
pots to the total resistance then it follows
that the outputs L' and R' are given by:

L' = R(l-x) + Lx

R’ = Rx + L(l-x)

Therefore, when x = 1, L' = L and R' = R
(normal stereo); when x = 'A, L' = R’ =
V4 (L + R) (mono); when x = 0, L' = R and
R' = L (reverse stereo).

The low output impedance of the emitter
followers ensures that, when the poten-
tiometer is in either the extreme clockwise
or anticlockwise position, crosstalk travelling
along the potentiometer tracks cannot
appear at the outputs. Good channel separ-
ation in the stereo and reverse stereo modes
is thus maintained.

INFORMATION THEORY
AND ENCRYPTION

by B.P. McArdle

Anyone who is, or becomes, involved in encryption operations
and cryptosystems must wonder about their connection with
Information Theory. In this article, Brian McArdle briefly explains the
areas of overlap and difference.

Consider a channel where a
message xi drawn from a set
|xi,X2,X3,. , ,,Xn] of n possible
messages, as illustrated in fig-
ure 1, is transmitted between
sender A and receiver B. The
message could be just a letter
from an alphabet of n letters or
a symbol. However, it is infor-
mation of some type and is ex-
changed between A and B. The
electronic representation of xi
could be a particular waveform
or a set of binary digits (bits)
etc. For example, the English
alphabet of 26 letters requires a
set of 5 bits to represent a letter
and since 2 5 = 32 there are 6
redundant combinations. For
the present the method of
signalling is not being con-
sidered. If each xi has pro-
bability Pr(Xi)=pi of being
chosen for transmission by A
the information entropy of the
channel is given by the
equation

H = — E pdogzCpi) (1)

The minus sign makes H
positive because every pt<l.
The base of the logarithm does
not have to be 2 but this means
that the dimension of H is bits. If
a particular message xi has
pi= 1 which means that pi=0 for
i/j, then H=0. If all messages
are equally likely to be trans-
mitted (uniform distribution)

H = log?(n) (2)

which is the maximum value
and is also the number of bits
required to represent a
message. The larger the value
of H the greater the uncertainty
in the information transmitted
over the channel. If H=0 there
is no uncertainty and the re-

etoktor indie January 1988 1 .35

ceiver B does not receive false
information. If the channel is
very noisy such that the signals
are corrupted during trans-
mission this adds to the prob-
lems of the receiver. However
the techniques used to reduce
the effects of noise are not be-
ing examined in this article.
And the technical limitations of
the channel, such as in the
Hartley-Shannon Law are not
considered.

A priori and a
posteriori information

The receiver may have some
advance information before the
message is sent. This is known
as a priori information and the a
priori probability is the prob-
ability that it is correct. The a
posteriori information and the
associated a posteriori prob-
ability refer to the transmitted
message after it is received.
These are commonly used
parameters in Information

Encryption operation

If x. is encrypted as illustrated
in figure 2

£k(xO = yi (3)

the electronic representation of
y. instead of x. is transmitted. It
is easier to keep track of the ex-
planation by taking the xi 's and
yi 's to be letters but this is not
essential. The encryption oper-
ation is varied by changing the
parameter K called the key. This
is the secret information and
should be known only to
sender and receiver. The
plaintext (or cleartext) and
ciphertext are xi and yi respect-
ively. An unauthorized listener
(cryptanalyst) on the channel
would probably know the
method of encryption but not
the actual key in use. The
strength of the encryption oper-

ation is determined by the diffi-
culty in deducing the key from
the ciphertext. Modem cryp-
tosystems also require that the
key should not be deduced
from a matched plaintext-
ciphertext pair(s). However, this
point is not developed further
because we are not actually
analysing particular systems.
The relationship between En-
cryption and Information
Theory is now considered by
outlining the results of a famous
paper.

Shannon's theory

Shannon (Ref.l) in his paper
compared the effects of
secrecy operations to the prob-
lem of noise. The letters of the
ciphertext should appear ran-
dom with no preference for any
particular letters) but only the
correct key will produce a
meaningful message after
decryption. He assumes that a
cryptanalyst knows or can
deduce -the method of encryp-
tion (which we will not examine
here) and has unlimited
ciphertext but no plaintext-
ciphertext pairs. He explains
the requirements of a crypto-
system using the following
parameters:

(a) entropy of the plaintext H(X)
computed as per equation (1);

(b) entropy of the ciphertext
H(Y) computed as per equation

(l);

(c) key entropy H(K) computed
as per equation (1);

(d) key equivocation computed
according to the equation

with joint and conditional prob-

abilities being used. We need
not be concerned with the
various steps in the analysis but
he deduces the following result

H(K/Y) = H(K)-H(Y) + H(X) =
H(K) — nD (S)

where D is defined as the Re-
dundancy. The dimension is
bits per symbol which is usually
a letter. This parameter re-
quires further explanation
because it is central to the
theory and conclusions.

Most languages have a
peculiarity that certain letters
occur more often than other let-
ters. Consider a message which
is encrypted by replacing each
letter with another letter ac-
cording to some rule. A good
cryptosystem will result in a
ciphertext which has a uniform
distribution of letters such that
no letter or group of letters oc-
curs too often. This means that
H(Y) and H(X) have different
values. Although they are both
measures of uncertainty, the dif-
ference between them is a
measure of redundancy. Ob-
viously, H(Y) will be larger than
H(X) from equation (2). For
English D=3.2. If H(Y)=H(X),
then D = 0 and H(K/Y)= H(K) and
even unlimited amounts of
ciphertext encrypted with the
same key do not reveal the key.
Thus one of the most important
conclusions of the paper is that
cryptanalysis is only possible
because of language redun-
dancy.

The 2nd important parameter is
the Unicity Distance given by

U = H(K)/D (6)

whose dimension is symbols or
letters. This is the number of let-
ters of the ciphertext required
to determine uniquely the key
(remember that Shannon as-
sumes that a cryptanalyst knows
the method of encryption and
has unlimited ciphertext but no
plaintext).

Example 1

Consider a simple substitution
as follows:

Plaintext: ABCDEFGHIJK
LMNOPQRSTUVWXYZ
Ciphertext: GZWJPABIMT
DNECSOYXVHLFKQRU.
The number of possible tables
which is the equivalent of the
various keys is 26 - such that

H(K) = LOGj(26-) (7)

:. U = 28{approx.) • (8)

which agrees very well with
practical results. Any reader
who wishes to know the actual
techniques to deduce the
tables should refer to (Ref.2).

Example 2

Consider the Data Encryption
Standard (Ref.3) which turns a
64 bit plaintext block into a 64
bit ciphertext block using a 56
bit key block (Fig. 3).

H(K) = log# 8 ®) = 56 (9)

U = 18(approx.). (10)

From Shannon’s Theory, this
means that 18 blocks are re-
quired to establish that a
decrypted message is mean-
ingful text. If 8 bit ASCII is used,
then 18 blocks = 144 symbols.
However, since the ASCII
alphabet has 128 symbols, the
result is not too different from
example 1. In reality, a crypt-
analyst could not try each key of
2 s6 possible keys but the
example does illustrate the
principle quite satisfactorily.
The other parts of Shannon’s
paper need not be considered
in presenting a short overview.
However, his results are de-
duced using many of the
parameters and formulae which
are now part of Information
Theory.

Conclusions

Encryption is not really a
branch of Information Theory.
There are important areas of
overlap but the theories and
techniques for the evaluation of
modern cryptosystems, such as
the Data Encryption Standard or

RSA Public Key Cryptosystem
(Ref.4) have become subjects in
their own right. Any student
who wishes to study Cryp-
tology would be well advised to
start with basic Information
Theory and Shannon’s paper.

Appendix

Equation (4) can also be written
in the form

H(K/Y) =

I Pr(kjyi).log 2 Pr(ki/yO (11)

where m is the number of poss-
ible keys. The other form is
commonly used in text books.

References

(1) Shannon, Claude E.; Com-
munications Theory of
Secrecy Systems. Bell
System Technical Journal,
volume 28 (1949).

(2) Friedman, William F.;
Elements of Cryptanalysis.
Aegean Park Press: U.S.A.
(1976).

(3 ) Data Encryption Standard.
FIPS PUB 46 National Bureau
of Standards, Washington
DC, U.S.A. (1977).

(4) Rivest, R.L. and Shamir, A.
and Adleman, J.; A Method
for obtaining Digital
Signatures and Public Key
Cryptosystems. Communi-
cations of the ACM, volume
26, number 1 (1983).

ELECTRONIC AND MAGNETIC QUANTITIES.

Quantity Symbol SI Unit Abbr Quantity Symbol SI Unit Abbr

1.36

1.37

READERSHIP SURVEY

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MULTI-FUNCTION
FREQUENCY METER

An advanced, versatile and user-configurable test instrument
capable of accurate measurement of frequency, frequency ratio
and time interval. In addition to all this, it can be used as a
period and event counter.

S2 is used for checking
whether the internal oscillator
works, but not for veryfing the
frequency of oscillation. It
should be noted that input B is
only used for measuring fre-
quency ratios and time inter-
vals. The frequency of the
signal applied to input A should
be higher than that applied to B.
Similarly, the pulse transition on
input A should occur before
that on input B.

The protective networks fitted
at the inputs of Ns and N6
enable applying alternating
voltages as well as CMOS or
TTL (digital) pulses. For small
alternating voltages applied via
C1-C2, diodes D1-D2 or D3-D4
do not have a limiting effect, so
that inverters Ns-N6 operate as
amplifiers. When the input am-
plitude is greater than about
2 Vpp, the inverters operate as
buffers. Limiting of the input
signal takes place when the in-
put signal at the digital inputs is
lower than -0.6 V or higher
than + 5.6 V. This means that AC
coupled input voltages are
clipped to about 6 Vpp. The in-
put sensitivity stated in the cir-
cuit diagram is an average and
frequency dependent value.
When the Type 74HCT04 in
position IC2 (Ns. . .N10 incl.) is
replaced with a 74HCU04, the
input sensitivity increases by a
factor 5 to 10.

The circuit around N7 ,..Nio
incl. and XOR gates N3-N4 is
used for measuring time inter-
vals, ie., the period that lapses
between the positive edges of
the signals applied to inputs A
and B. A bistable internal to the
ICM7226B is set and reset by
the pulse transitions at input A
and B, respectively. When the
bistable is set, the oscillator
pulses are internally fed to the
counter input. Evidently, the
longer the bistable remains set,

The multi-function test instru-
ment described here is based
on the 8-digit counter/timer IC
Type ICM7226B from Intersil
(GE/RCA). This chip combines
all the functions expected from
a good and versatile counter,
and requires very few external
components. The chip handles
frequency measurement from
DC to 10 MHz, period measure-
ment from 0.5 11s to 10 s, unit
counting up to 10 million events,
frequency ratio measurement,
and time interval measurement.
The inputs of the proposed in-
strument can accept a wide
range of alternating (analogue)
voltages as well as digital
pulses at TTL or CMOS levels.

The counter, IC3, has an on-
chip timebase oscillator which
operates at 10 MHz (Xi). It is
possible to use a 1 MHz quartz
crystal provided Se is closed.
Similarly, S7 makes it possible
to apply an external clock
signal of 100 kHz or more to pin
33. When switch S6 is closed,
the position of the decimal
point on the display is con-
trolled externally via the
respective input, pin 20. The
decimal point can thus be pos-
itioned as required for the
prescaler used. Switches S6-S7-
S& and the associated diodes,
D6-D7-D8, are intended for the

above options on the frequency
meter, and may be omitted
when the relevant function is
not required. It is, of course,
also possible to replace the
switches with wire links for per-
manent operation in a particular
mode.

The maximum input frequency
applied to input A of the instru-
ment is 10 MHz in the frequency
and unit count modes, and
2 MHz in the other modes. The
counter modes and functions
that can be selected with the
range switch, Sta-b, and the
function switch, Sza-b, are sum-
marized in Table 1. Position 6 of

Circuit description

The circuit diagram of the fre-
quency meter is given in Fig. 1.
It would be beyond the scope
of this article to give a detailed
description of the internal oper-
ation of the ICM7226B, and the
following is, therefore, an
outline of the simple peripheral
circuitry needed to obtain a
complete instrument. A
prescaler for extending the in-
put frequency range to 1.2 GHz
will be discussed in a forth-
coming issue of Elektor India.

Switch S2: FUNCTION

The ICM7226B has internal
timebase circuitry, display
decoders, segment and digit
drivers. The 8-digit read-out is
composed of common cathode
LED displays multiplexed at
500 Hz and a duty factor of 0.122
per digit. Leading (non-signifi-
cant) zeroes are blanked when
the meter is set to frequency
measurement in kHz or period
measurement in tis- LED D9 in-
dicates an overflow condition,
i.e., the counter is "full”, and all
digits read 9.

1 (K1) frequency (Ml

2 (K8) period (TaI

3 (K2) frequency ratic

4 (K51 time interval (f

5 (K4) unit counter

Switch S«: RANGE

Position

1

Fig. 1 Circuit diagram of the multi-function frequency meter.

the more pulses are counted,
and the higher the read-out on
the display. Push-button prime
is pressed before measuring
the time interval for a single
event. Inverters N10-N9
generate a brief pulse for chip
input A; N8-N7 a slightly
delayed pulse for input B. The
internal logic in the ICM7226B
is thus primed ready for
measuring the interval for one
event, delimited by the positive
. edges of the pulses applied to
instrument input A and B. Press-
ing prime is not required when
these inputs are driven with a
repetitive signal, as the first
alternating signal states cause
automatic priming of the
counter chip.

The read-out can is retained
("frozen") as long as the hold
switch, Ss, is pressed. The
counter's internal circuits— and
hence the read-out— can be
cleared at all times by pressing
the reset key, S3. Capacitor C7
is connected in parallel with S3
to prevent hang-ups at power

1.42 eleklor India January 1 988

on. The 3 push-buttons can be circuit diagram are fitted on a securely and slighly off the

fitted on the counter's front single printed circuit board, board to prevent sharp solder

panel as suggested in Fig. 2. whose track layout and compo- points piercing the insulating

The power supply for the fre- nent mounting plan are shown material and causing short-

quency meter is of conventional in Fig, 3. Commence the con- circuits with the grounded

design, and requires no further struction with fitting all the wire metal can. It is recommended

detailing. links. Do not forget the 8 short to use good quality sockets for

ones underneath the displays! all integrated circuits. The dis-

. Electrolytic capacitor Ciz is fit- plays are also fitted in 10-way

Construction ted at the track side of the sockets, made from terminal

Virtually all parts shown in the board. Make sure that it is fitted strips or 14-way IC sockets. Use

iq. 2 Lav-out of the readv-made front oanei fail for the frenuencv meter.

£1 ®

Fig. 3 Track layout and component overlay ot the PCB for building the frequency meter. Capacitor C12 is fitted AT THE TRACK

short lengths of strong wire to
ensure the correct height of the
displays above the board. LED
D9 is a high brilliance type
whose leads are lengthened
make its top is level with the
displays in the sockets. Voltage
regulator IC4 should be
mounted with a heat-sink. The
range and function switches,

S4 and S2, are soldered direct
onto the board, or with short
lenghts of left over component

wire, to minimize stray induct-
ance and capacitance. This
measure effectively prevents
unwanted effects such as in-
determinate illumination of
digits ("ghosting"). As already
stated, function switches S6-S7-
Se may not be required on the
front panel of the instrument. In-
puts A and B are made in
flange-type or single hole BNC
sockets. Two more of these are

remiireH when it ic intended to

Capacitors:
Ci;Cz=1p; 63 V
electrolytic)

Ce;C8=39p
Ce=40p trimmer
Ci2>47ty; 26 V

Semiconductors:

Di . . .Ob incl.-1N4148
D6;07;Da= 1N4148 {see text)
De= high brilliance LED (red)
Dio. . . Did incl. = 1N4001
Dh= red LED
IC1-74HC86 or 74HCT86
IC2 = 74HCU04 or 74HCT04
IC3-ICM7226BIJL or
ICM7226BIPL f
IC4-7605

LDi . . . LDa incl. = common
cathode LED display
HD 11070*

S2= 2-pole 6- way rotary switch
for PCB mounting."

S4= 2-pole 4 or 6-way rotary
switch for PCB mounting. "
Se:S7;Sa= miniature SPST
switch Isee text).

Xi = 10 MHz quartz qrystal.
T0220 style heat-sink for IC4.
Verobox enclosure Type
■ 4775-1411.

PCB Type 87666 (available
through the Readers Services).
Front panel foil Type 87286F
(available through the Readers

Mains transformer 8 V: 0.5 A
Mains entrance socket, fuse
(100 mA), and DPDT switch.
Knobs for rotary switches.

BNC sockets as required.

* Available from Universal
Semiconductor Devices Limited

• 1 7 Granville Court •

Granville Road • Hornsey •
London N4 4EP. Telephone:

(01 3841 9420. Telex: 25157
usdco g. Fax: 01 348 9425.

Switch with adjustable stop,
e.g. Lorlin Type CK1045 ICirkit
stock no. 53-21045).

extend the frequency meter
with the prescaler to be in-
troduced. Inputs EXT. OSC, EXT.
dp, and output buff, osc, can be
made in suitable sockets on the
rear panel of the enclosure. The
signal at buff, osc can be used
for setting the oscillator fre-
quency to 10.000 MHz precisely
with the aid of trimmer capaci-
tor C9. It is also possible to use
the signal for driving other cir-
cuits, provided the buff, osc out-
put is fitted with a 10K resistor to
the +S V rail.

The supply voltage for the
prescaler is available on 2
soldering pins next to the ext.
dp input

The completed PCB is mounted
vertically in the moulded
guides provided in the bottom
plate of the Vero enclosure. The
ready-made front panel foil for
the frequency meter can be
used as a template for drilling
the metal front panel provided
with the enclosure. The shafts
of the rotary switches, Sz and
S4, are cut to size to enable fit-
ting suitable knobs. The LED
displays are fitted in a rec-
tangular clearance cut in the
front panel. The visibility of the
read-out is enhanced by the
semi-transparent bezel in the
ready-made front panel foil.
The overflow indicator, D9, is
fitted immediately below the

right-hand side of the display
bezel. The position of
various controls and indicators
is evident from Figs. 2 and 4.

It is, of course, possible to use
ready-made mains adapter with
8 VAC output for powering the
instrument. In many cases, this
is safer and less expensive than
incorporating a mains 1
former. When it is still intended
to furnish the frequency r
with its own, internal, n
supply, the mains socket and
fuse (100 mA) should be fitted
safe locations onto the re:
panel of the enclosure. The
mains transformer should be
preferably an 8 V, O.SA type.
The current consumption of the
circuit is about 55 mA with all
displays blanked, and 175 mA
with all displays illuminated. H

Reference:

Component Data Catalog 1987 :
ICM7226A/B p. 14-80 ff. Intersil
GE/RCA International Limited
• Beech House • 373-399 Lon-
don Road • Camberley • Sur-
rey GU15 3HR. Telephone:
(0276) 685911. Fax: (0276) 685255.

NUMBERS AND THE MACHINE

by C.H. Freeman

Computer science depends largely on the properties of real
numbers. The correct use of these requires an understanding of
the mathematic basis of the real number system. Unfortunately,
many people shy away from anything mathematical, even if it
has only to do with numbers. This article attempts to allay these
misgivings.

Modern man counts in base ten,
that is, he uses the ten in-
dividual symbols 0, 1, 2, ... ,8, 9.
Obvious, you might say, but it
hasn’t always been so. Some
races have been known to
count in base 20 (by using their
toes and fingers in arithmetical
operations) and the concept of
zero itself is quite new; conse-
quently, the Romans, who had
no representation for zero, had
endless trouble with arithmetic.
In general, an n digit integer,
No, can be represented by

No = dnR" + dn-i/? n_1 + ...
+rfiJ? 1 + d°R 0

No = l dj?

where d\ d 1 , ... , dn are the
decimal symbols in the coun-
ting system and R is the number
base we are working in. When
we count in decimal, the sym-
bols used are 0, 1, 2 9 and

R, the base (or radix), is 10. Thus
we can represent, say, 50465 as

5x10* + OxlO 3 + 4 x10 s +
6x10’ + 5x10°

Now, although this suits us
humans very nicely, digital
systems do not use ten discrete
values when representing
numbers; the engineering
problems introduced in using
such a system would be too
great. Instead we use base two,
more commonly referred to as
binary. The binary system has
just two decimal digits in its
counting system: 0 and 1. Now,
this is handy because a switch,
be it electronic, mechanical,
hydraulic, pneumatic etc., can
be either on or off and can thus
be made to represent a single
binary digit (or bit. the deriva-

tion arising from Binary digiT).

have 16 individual symbols in its

So, using the above expression,

counting system and after go-

a string of binary digits, such as

ing through the symbols 0-9 we

11001, can represent the

run out! Mathematicians, when

decimal number

faced with problems such as
these, invariably do the decent

1x2* + 1x2 s + 0x2 s +

thing — and cheat; In this

case

+ 0x2’ + 1x2° = 25

the letters A-F are pressed into
service and the full counting

and we can now see how any

system runs 8 1, 2, 3, 4, 5, 6, 7, 8,

positive decimal integer can be

9, A, B, C, D, E, F.

represented in binary, and also

how to transform a binary
number into its decimal equiva-

Binary addition

lent. But what about translating

Two binary numbers are added

decimal into binary? What do

together in the same way two

we do then? The answer is, we

decimal numbers are added

simply divide our decimal

together: by adding together in-

repeatedly by 2, recording the

dividual digits, paying due at-

remainder at each stage of the

tention to any carry

division. The series of re-

generated. As there are

ust 2 1

mainders, when read 'from the

igits in the

binary system,

bottom up', form our binary

there are 4

possible

sums

number. Let’s try an example,

which can be formed. These

converting 229 into binary

ire

229 t 2

sum carry

114 remainder 1

0 + 0 =

57 remainder 0

28 remainder 1

14 remainder 0

Using this principle, w

can

generate a table of binary

numbers alongside

their

decimal equivalents. Part of

thus 229 = 11100101. Check this

such a table for a 4 bit binary is ,

for yourself by converting the

shown in Table 1.

What we have just discovered
about converting decimal to

TABLE 1.

and from base two applies

2 3 22 2’ 2°

DECIMAL

HEX

equally well to base 3, base 7,

base 9 or, in fact, any base you

care to name. Actually, two

2

2

other bases, base 8 and base 16

3

3

(known as octal and hexadeci-

0 10 0

4

4

mal respectively), are import-

0 10 1

5

5

ant, but more of this later. For
the moment, though, you may
well be wondering about base

16 (or hex as it is usually
known). After all, base 16 will

1111

15

P

It is at this point that octal and
hex become interesting. By col-
lecting adjacent bits into
groups of four, we can write just
one hex digit in place of each
group. To illustrate, consider

59 = 111011 = 0011 1011 =

= 3B (hex)

and it can be seen that hex no-
tation can act as a useful 'short-
hand' when writing long binary
sequences. Note how we pad
the number out with leading
zeroes in order to obtain two
4 bit groupings. A similar tech-
nique can be adopted using oc-
tal by gathering bits into groups
of three thus

59 = 111011 = 111 Oil = 73 (octal)

Signed integer
representation

So far we have considered
binary representation of
positive integers only. What
happens if we want our com-
puter to hold a negative in-
teger? Our system has so far
made no allowance for such
eventualities so what can be
done? Fortunately, three
possibilities exist. They are

(a) sign-magnitude
representation.

This is the simplest possible
method and relies upon the fact
that computers hold numbers in
fixed length registers. These
registers are usually 4, 8, 16 or
32 bits in length, but the import-
ant fact is that their length is
constant. If we have an n bit
register, we can use the most
significant bit as an indicator (or
FLAG) to represent a positive or
negative number. It is usual for

elector india January 1988 1 .45

this bit to be set (ie. 1) when
representing a negative num-
ber and reset (i.e. 0) when
representing a positive. The
rest of the n - 1 bits hold the ab-
solute value of the number. The
greatest absolute value which
can be held in such a register is
2" _1 -1 so it follows that if a
number is held in an n bit
register in this form

(b) diminished radix
complement.

For an n digit number N, in
base R, we can form what is
known as its diminished radix
complement by applying the
formula

DRC = (/?"— JVr)-l

The name of the complement
depends upon the base in
which operations are being
performed and takes the name
of the highest decimal digit in
the system. Thus the DRC of a
decimal number is known as its
nines complement, whilst that
of a binary is referred to as its
ones complement. With the
above equation as a
springboard, it is not difficult to
show that the ones complement
of any binary can be formed
simply by inverting each bit,
that is changing 1 to 0 and 0 to
1. For example,

0001

1110 represents -1

Thus in an n bit system the
greatest positive number will
be held by only n - 1 of the bits.
Therefore, the greatest positive
number = 2" * 1 - 1. The greatest
negative will be represented by
a 1 in the most significant bit fol-
lowed by n-1 zeroes. Hence
range = 0 to ± (2 n 1 — 1)
inclusive

(c) radix complement
representation.

The radix complement of an n
digit number Nx in base R can
be calculated using the equa-
te = R«-N,

and the radix complement of a
binary number is referred to as
'os complement. It should
be clear that adding a number

1.46 elaktor india January 1988

to its twos complement will
result in all zeroes plus an
overflow carry. If the system in
use ignores any digits in excess
of n then the above equation
reduces to

RC = -Nx

in other words, the radix com-
plement represents the
negative of a number in the
same number of bits.

Computer circuitry can easily
form a twos complement by
firstly inverting all the bits of the
number (to obtain a ones com-
plement) and then simply ad-
ding 1 to the least significant
bit. For us mortals there exists
an easier method of translating
a binary into its twos comple-
ment. Starting with the least
significant bit, we copy all the
bits in the number up to and in-
cluding the first occurrence of
one. The remaining bits are
then inverted. Table 2 shows
comparative representations
for a 4 bit register. Note that in
the case of twos complement
representation

and the minimum negative
number cannot be negated.

Why bother?

If all this seems as if it is merely
some abstract mathematical
stuff, then let me assure you that
it is not. All this maths has a very
practical consideration in the
design of computer hardware.
You see, it is easy to build cir-
cuitry which can perform inver-
sion of a binary and addition of

two binaries, but it is far less
simple to build circuitry which
can perform subtraction direct-
ly. This means that the process
of subtracting one binary
number from another is in-
variably reduced to two distinct
operations: forming the com-
plement of the subtrahend, and
then adding this complement to
the minuend. This leaves us
with the decision as to which
complement to use: ones com-
plement or twos complement?
If we choose to use twos comp-
lement, we simply add and then
discard any carry which may
arise from the most significant
digit. If we use the ones com-
plement, however, any such
carry must be added to the
least significant digit. If this
generates further carry digits,
they must be also added until
no further carries are

generated. This end-around-
carry means that arithmetic per-
formed with the twos comple-
ment system is a much simpler
business than all that mucking
about in ones complement.
Consequently, twos comple-
ment is the method computers
will normally use when

representing negative num-
bers. Let’s look at an example,
subtracting 13 from 42 to leave

Ones comp, of 13 = 110010,
1 = twos comp. = 110011

101010 + 110011 = 1011101

then it actually is. To a person,
performing such a process
seems quite alien, but com-
puter circuitry finds the pro-
cess beautifully simple. And
speaking of simplicity, the
world of numbers is not limited
to the simple system of integers.
We must now examine how we
can represent the system of
natural numbers in binary.

The real world

In our earlier look at binary
numbers we saw how an n digit
integer, No, in base R could be
represented in the following
manner:

No = dxxR" + dn - 1 tf' 1-1 +

+ . . . + d\R' + doR°

We now extend this to enable
us to represent any finite length
real number using the follow-
ing representation:

Now, when we use binary t
represent such a number, w

+ d- 2x2- 2 + ...

and it should be easy :
we can hold a binary fraction i
a register, using the mos
significant bit to represent 2~ :

that

0010

OOOI

OOOO

1010

1001

1000

0.000

0.125

0.250

0.375

0.500

0.625

0.750

0.875

Table 3 shows a three-bit
register holding binary frac-
tions in just such a way, along
with the decimal equivalent of
its contents. This table also
shows the method of converting
a binary fraction into a decimal
fraction. By inspection, it
should also be easy to see that
such an n bit register can hold
values in the range

0.0 to (1.0 - 2-")

in steps of 2~".

Before going any further, we'll
take a look at how we convert
decimal fractions into binary
fractions. Decimal integers, as
we saw earlier, are converted
into their binary equivalents by
repeated division by two, re-
cording the remainder at each
stage. Decimal fractions, on the
other hand, are repeatedly
multiplied by two. At each
stage, the resulting integer part
is separated from its fractional
part and forms a bit in the
resulting binary. The process is
better illustrated by example
than by words so let's convert
0.375 into binary:

0.375 x2

0 + 0.750 x2

1 + 0.50 x2

1 + 0.0 process completed.

0.375 = 0.011

Try converting a few decimals
into their binary equivalents,
and then convert them back
into decimal again. You'll soon
get the hang of it! Now we know
how to convert a decimal real
into a binary real let's think
about how we can store such a
number inside a computer.

If we think of a binary number
as having two separate consti-
tuents, an integer part and a
fractional part, then it would
seem an obvious move to store
such numbers in the following
way:

N BITS

FRACTIONAL

PART

leading us to suppose we can
store numbers in steps of 2~ N .
In fact, this is a very poor way to
store numbers. When very
large or very small values are
represented in such a way, it is
found that there can be vast
amounts of 'wasted space'. This
is inevitable whenever such a
fixed point system is adopted
and a much better bet is. . .

Floating point
representation

Floating point representation
relies on the fact that any
number in base R can be split
into two parts, its mantissa, M,
together with its corresponding
exponent, E, and depicted as

MxR E

In decimal, of course, this cor-
responds to the familiar ex-
ponential notation (powers of
ten) we all know and love. If we
consider the binary number
101.1101 (for example) then it can
be written in mantissa and ex-
ponent form as

101.1101x2' or 10110.1X2- 3 or
0.1011101 x2 4

The last notation is, in fact, the
usual method of writing binary
reals, with the most significant
set bit coming immediately
after the decimal point. Such a
number is said to be NOR-
MALIZED: In point of fact this is
almost exactly how computers
do store real numbers within
their memories, as two distinct
series of bits representing man-
tissa and exponent. You've
probably also noticed by now
that numbers stored in this way
will have the most significant bit
of the mantissa apparently
redundant (as it appears it will
always be zero). This is no ac-
cident. Negative as well as
positive mantissas and ex-
ponents must be catered for
and in such cases the mantissa
is held in twos complement
form, the most significant bit
being taken as a sign bit.
Remember that such a bit will
usually be set if the number it
represents is negative, and
reset if the mantissa is positive.
The exponent is also held in
twos complement form (see
below)

Let's try and illustrate this by
considering a fictional com-
puter holding numbers in two 4
bit registers:

SIGN 2‘‘ 2- 2 2- 3

SIGN 4 2 1

The mantissa, remember, is
normalized so it can take the bit
patterns (ignoring the sign bit
and considering 2“' as the
most significant bit)

111, 110, 101, 100 corresponding
to the decimals

0.875, 0.750, 0.625, 0.500
and for negative mantissas the
possible range which can be

-1.000, -0.87S, -0.75, -0.625

and we get the range for our
mantissa

-1.0, -0.875, -0.75, -0.625,

0, 0.5, 0.625, 0.7S, 0.875

The exponent can take the
range +7 to -8 in steps of 1, of
course. The numbers we can
represent in our 'machine',
therefore, will be

0.875 x2 7 = 112
0.750 x 2 7 = 96

0.625x2- 8 = 5/2048
0.500 x 2-® = 4/2048
0

-0.625 x2-® = -5/2048

MBITS

INTEGER

PART

-0.750x2-® = -6/2048

- - 0.875 x 2 7 = -112

- 1.000 X 2 7 = -128

Notice that because of the twos
complement method of storing
our mantissa there are two
numbers which cannot be
negated: the minimum positive
real and the minimum negative
real.

A 'proper' computer would, of
course, use many more bits than
4 to represent numbers but the
principle is exactly the same as
that outlined for our 4 bit
example above.

Range and
accuracy

It is clear, judging by the
example above, that there are
some decimals which can
never be represented exactly,
for the reason that there simply
aren't enough bits available to
fit the number in. For example,
109 = 1101101

109 = 0.1101101 x2 7

But the binary equivalent is too
big to fit into our 4 bit mantissa.
In cases such as these there are
two options open. We can simp-
ly 'chop off (or TRUNCATE) the
excess bits and store as

0.110x2 = 96

or we can ROUND the number
up (or down accordingly) to

0.111x2 = 112

Whatever happens, it should be
realized that there will in-
variably be a degree of error in
computer arithmetic. Usually
.such errors present no big
problems and can be allowed
for.

As far as range is concerned, if
a machine stores numbers as M
bit mantissas and N bit ex-
ponents, the greatest possible
positive mantissa will be equal
to

0.111 ... Ill

and will be equal to i-2- <M " l)

and the greatest possible expo-
nent will be given by 2 W_ 1 — 1.
So,

1.47

greatest positive number -

(1_2-(m-D)x( 2 w - 1 -1)

As far as the smallest positive
real is concerned, the mantissa
will equal 2 _1 and the expo-
nent will be 2" (2 "~ >

Smallest positive number =
2- 1 x2-< aV ' l >

Try and work out the largest
and smallest negative reals
which can be represented. So
there you have it! Computer
arithmetic is not just so much
arcane theory, but is a
fascinating branch of mathemat-
ics: a branch which is in con-
stant daily use in fields as

diverse as spacecraft navigation
to preparing and printing your
gas bill. The modem world is so
very heavily dependent upon
computers that it is doubtful
whether it could function with-
out their assistance. Love them
or loathe them, you’ve got to ad-
mit that we need them!

The author would like to
acknowledge the help of Mr. G
Parkes, dept, of compute
science, University of Hull, fo,
his assistance in the prepara-
tion of this article

multiple voltage supply

Many circuits using, for example, both op-
amps and logic circuits, require more than
one supply voltage. The circuit described
here is designed to supply four voltages of
+12, +5, -7 and - 1 2 volts, with a maximum
current of SO, 3 00, SO and again 50 mA
respectively.

The positive supply voltages are produced in
the normal fashion, using positive voltage
regulator ICs; for the negative voltages it
would be possible to use the special ICs
which have been designed for this purpose,
however these are both fairly expensive and
often difficult to obtain. For this reason an
alternative solution was sought. Although
the 723 was designed for positive voltages,
it can also be adapted for negative output
voltages if, instead of being used as a series-
regulator, it is connected as a shunt stabiliser
(IC3 and IC4).

Shunt stabilisers suffer from the dis-
advantage that a constant power is taken
from the mains transformer, irrespective
of whether they are feeding a load. This

means that this type of circuit is not
particularly efficient; however in this case,
where the maximum current is only 50 mA,
the power loss is negligible.

The negative output voltages can be adjusted
by means of PI and P2. After adjustment,
the series-connected potentiometer and
resistor can be replaced by two series-
connected resistors. All the voltages supplied
by the circuit are short-circuit proof; that
is to say that shorting the outputs will not
damage the supply. The positive outputs
are provided with the usual current limiting.
In the case of the shunt regulators for the
negative voltages, the short-circuit current
is determined by the dropper resistors R7 and
R 1 3. These should be rated at 2 W (or more)
to prevent overheating.

Note that it will not always be necessary
to use such a complicated transformer
(8-0-8- 1 (> V). If the S V supply does not
have to deliver much current, a 0-8-16 V
ti e. an 8-0-8 V!) transformer can be used.
1)2 and C 2 are omitted in this case.

TOP-OF-THE-RANGE

PREAMPLIFIER-3

This concluding part of the article deals with the construction of
the preamplifier. Additionally, it gives a detailed discussion of the
various types of capacitor, both myths and realities.

The preamplifier contains three
printed-circuit boards: mother
board, bus board, and supply
board. The dimensions of the
boards have been chosen to
allow the unit fitting in a stan-
dard 19 inch cabinet with a
height of 2 units (88 mm). The
mains transformer is fitted in a
separate aluminium enclosure,
the dimensions of which are not
critical. In addition to the PCBs,
two foils are available through
our READERS SERVICES: one
for the front panel and one for
the rear panel.

High-quality

components

It is important to use only high-
quality components to ensure
optimum performance. All re-
sistors should be metal film
types with a tolerance of 1%,
although that of Rr and Rs
should preferably be 0.1%. If
these prove unobtainable, sel-
ect a pair of 1% resistors that are

identical in value, or very nearly
so, with the aid of a digital
multimeter.

All opamps are Type OP-27,
while the dual transistors are
MAT-02s. Do not use the OP-37
in the line amplifier, because
this type has off-set compen-
sation only for gains greater
than 14 dB.

All capacitances in the signal
paths are formed from a parallel
combination of an MKT and an
MKP capacitor (M= metal; K=
plastic; T=polytherephthalate;
P= polypropylene). Frequency-
determining capacitors in the
IEC compensation section (C9 ,
C10, Cn) are 1% MKS ^poly-
styrene) types. Electrolytic
capacitors in the power supply
are all PCB mounting types.
Decoupling capacitors shunt-
ing electrolytic capacitors may
be MKT or ceramic types.

It is advisable to use silvei-
or gold-plated phono input
sockets: these guarantee free-
dom from oxidation and conse-

quent contact potentials be-
tween plug and socket.

The relays on the bus print
must, of course, be of prime
quality. Four possible types are
shown on the component list.
The excellent SDS type is unfor-
tunately polarized, and its coil
connections are exactly the re-
verse of the others: if this type is
used, therefore, its coil connec-
tions must be reversed.

The volume control poten-
tiometer must be of the highest
quality: in the prototype a
stereo version from Alps was
used with excellent results.

The balance potentiometers are
rather less critical, but should
still be of very good quality:
they should definitely not be
carbon types, but conductive
plastic or cermet. Bourns or
Spectrol models are rec-
ommended.

The switches are not critical
components, since they only
switch direct voltages to the

A few tips to make the total cost
come down somewhat. The
OP-27 may be replaced by a
5S34, which is a lot cheaper and
still a good-quality device, but it
may give off-set problems. The
MAT-02 may be replaced by an
LM394, but the overall quality
will come down slightly. In this
context, if moving-coil pick-ups
are unlikely to be used, only
one MAT-02 per channel is re-
quired as already explained in
Part 2. Cost reductions on the
capacitors should be well con-
sidered: whatever you do, never
use electrolytic capacitors in
the signal paths — at the very
least MKT types should be used

Construction

The mains transformer, which
can either be of the laminated
or of the toroidal type, should
be mounted in an aluminium
case (see Fig. 13). From one end
of this case the— non-earthed—

eleklor India janusry 1988 1 .49

mains cable should emerge,
and from the other a fairly heavy
three-core cable terminated
into a suitable plug. This plug
mates with a corresponding
three-pin socket at the rear of
the preamplifier enclosure.
This arrangement is absolutely
essential to keep any hum from
the preamplifier circuits.

Next, the supply board should
be completed. The voltage
regulators should be fitted onto
adequate heat sinks, which can
be fitted to the board with self-
tapping screws.

When the board is completed,
it can be mounted at the right-
hand side of the enclosure. Do
not forget a screen between it
and the mother board. The
alternating voltage from the
mains transformer is taken to
the board via the double-pole
mains switch.

Mains on-off indicator Du
should now also be connected
to the supply board.

The earth connection on the
supply board is then connected
to the enclosure via a short
length of heavy-duty cable.

The supply may then be
switched on to test whether the
direct voltages are present: if
so, they should be set to ±18 V
with the aid of the two presets
—Pi and P2 .

The bus board can be complete
fairly quickly. First screw all the
phono sockets to the board (in-
puts at the track side). Tighten
them by hand and then solder
them lightly to the board: this
prevents them coming loose
when later the corresponding
plugs are withdrawn and
plugged in again. Then tighten
the socket nuts with a suitable
spanner. After that all other
components, including the
relays, can be fitted onto the

Some resistors are soldered
direct to the centre terminal of
the sockets.

The connections between
socket and board at the tape
and line outputs are made
with a short length of equip-
ment wire. The remaining con-
nections are provided with
soldering pins to make them
easily accessible during the re-
mainder of the work.

Remove any resin from the
board with a brush dipped into
white spirit or alcohol, and then
seal the track side with a suit-
able plastic spray. Take care
that no spray gets into the
sockets or relays. This cleaning
and insulating of the board re-
duces the risk of cross-talk to a
minimum.

The board is then mounted to
the rear panel of the enclos-
ure with the aid of insulated
spacers: this obviates any possi-
bility of the tracks or sockets
touching the enclosure.

The earth connection adjacent
to the sockets must be connec-
ted securely to the enclosure to
become the case earth: this
same point should be connec-
ted to the central earth point on
the supply board via a short
length of cable.

The mother board should be
completed in the following
order resistors; capacitors;
mechanical parts; semiconduc-
tors. Make sure that non-
insulated capacitors (if at all
used) can not touch the screen-
ing at the top. Do not use
sockets for the ICs.

At the front of the board, three
supply rails have to be pro-
vided. To do this, first fit
soldering pins in all the holes;
then cut narrow strips of brass
or tin sheet, and solder these to

Parts list (Fig. 151

channel Idashed |'| in the

) identical

| Resistors tail melal film):

I Ri-20RF
R;-49R9F
Rt= 100RF
R.;Rso = 1K0F
Rs=49K9F
R6 = 150RF
Rr;Ri = 1K5F
R>:Ri.:Rn = 392RF
R.r = 348RF
R 11 = 3K48F
Ri« = 3K16F
Ris = 22K1F
Ri* = 1K21F
Rw = 16R5F
Ru:R«i;R«=2K2F
Ri9 = I21KF
R» = 475KF
Rji:Rs2 = 20KF
| R»;R»-15KF
Rh-4K75F
R« = 3K92F
Rrs;Rt«:R«r=1M0F
Rrr = 475KF
Rm = 27K4F
Rr.= 182RF

Rm;Rm;Rm;Rm;Rm;Rh;Rh;

Rtr = tORJ
Rn;R« =22RJ
Ris = 6K8J
Rm;R«;R»i - tOKF
Rsi - 100KF

Pi = 10KJ log potentiomeler
le.g. Bourns Electronics' I
Pr - 10KJ log stereo pot meter
le.g. Alps RKGA-2 10k AX2"I

Capacitors:

Ci = 220pJ polystyrene
Cr;C)= lOOpJ polystyrene
Ct = 47pJ polystyrene
C»;C.:Cij;Ci.:C«- lOpJ MKT
Cr;Ci);C4i = 4,i7J MKP
Ci = lOnOJ polystyrene
C»;Cn = 330n0F polystyrene
Cio = 1nOF
C.i=2p2J MKP
Cie;Ci? =470nJ MKT

Cu= 10OpM;3 V; tantalum
electrolytic

Ci9;C2i;Ctt:C25;C26;C3i ;Cir;
C<2;Co;Cu;C« - 220nJ MKT
C2o;C29;C3o = lOOpM; 25 V
C23;C2<;C22;C2e;Ca4;C<s;C<i;

C49 = 1000pM; 25 V
C 3 S = lOOnJ MKT
Cso:Cji;Ch;Cs3;Cs»:Cs3 = 22nOK
ceramic

Semiconductors:

Dr = 1N4148
Db - LED red
Ti;T2;T3 = MAT-02
T. = 2N2291

ICi;ICa;IC«;ICs = OP-27 •

IC3 = LF41 1

Si = 2-pole DIP switch
St = 8-pole DIP switch
Ss-SPST miniature
Reo = sub-miniature PCB mounting
relay; 2-pole change-over; 12 V
le.g. Meisei MI-12 or M1B12H;
Siemens W11V23102-A0006-
A111 * * ; Omron G2V-2;

SDS DS2E-M-12I*

16 silver- or gold-plated phono

PCB 86111-3
•Distributors in UK:

Cambridge: Hi-Tek; telephone
102231213333

Sevenoaks: Jermyn Distribution:
telephone 107321 450144
Harlow: STC Electronic
Services; telephone (02791
26777

"Armon Electronics; telephone
01-902 4321

' • Electrovalue; telephone
107841 33603 or 061-432 4945
'May also be available Irom
Electromail; telephone
105361 204555

General note: many special audio
components are available from
Sage Audio, Bingley, West
Yorkshire, telephone 102741
568647

Kord Audio Products, The Green,
Nettleham, Lincoln, telephone:
(0522) 750702

8611 MIMS

Fig, 17. Template for drilling

the pins a few millimetres
above the board (see Fig. 14).
Next, all connecting points
should be fitted with soldering
pins. At this stage, only the
pin for the earth connection to
the supply board should be
soldered to the screening layer
at the top of the mother board.
Finally, the board is cleaned,
and its track side insulated with
plastic spray, in the same man-
ner as the bus board.

The mother board can then be
mounted in the enclosure. All
connections to switches and
potentiometers can then be
made, as can those between the
mother and bus boards (at the
right of the motherboard at the
line section). Screened cable is-
not necessary for the latter, as
these connections are only a
few centimetres long.

Next, the connections between
the supply and mother boards

The switching connections to
the bus board may be made
from flat cable terminated at
both ends into a plug to mate
with the corresponding sockets
on the boards. It should be
noted that socket Ki on the
bus board is fitted 180° differ-
ent from the position shown
in Fig. 4 on page 43 in the
November issue of EE. In re-
ality, pin 1 is located where

pin 10 is shown.

Finally, the connections be-
tween the MC-MD sockets and
the associated inputs at the
mother board, and those be-
tween the MC-MD amplifier
output on the mother board and
the bus board should be made.
These should be in good-qual-
ity screened audio cable or
flexible coaxial cable (TV type).
When all connections are made
and checked, the mains may be

1 .52 slektor I

Technical specification

Input sensitivity
Phono: MC (low!

MC (high)

MD How)

MD (high)

CD P

Maximum input voltage at 1 kHz

Phono: MC (low) 1 mV

MC (high) 2 mV

MD (low) 20 mV

MD (high) 40 mV

Tape, tuner, aux 2 V

CD 4 V

0.1 mV into 47K
0.2 mV into 47K
2 mV into 47K
4 mV into 47K
200 mV into 45K
400 mV into 20K

Phono: MC (low) 6 mV

MC (high) 12 mV

MD (low) 120 mV

MD (high) 240 mV

IEC IRIAA) correction
±0.2 dB over the frequency range o
input impedance: 47K; standard inp
can be preset from 10R to 47K and

Output (line out)

Nominal output voltage 1 .2 V

Maximum output voltage 10 V
Output impedance <100R

Maximum output current 20 mA

Third-harmonic distortion
(at 1 kHz)

output voltage 100 mV

Phono: MC (low) <0.1%

MC (high) <0.05%

MD (low) <0.01%

MD (high) <0.01%

Tape, tuner, aux <0.005%

CD <0.005%

f 20 Hz to 20 kHz. Standard
ut capacitance: 50 pF. Values
from 50 pF to 500 pF.

1.2 V 10 V

<0.01% <0.02%

<0.01% <0.02%

<0.005% <0.02%

<0.005% <0.02%

<0.005% <0.02%

<0.005% <0.02%

(over range 20 Hz to 20 kHz and ou
Phono: MC <0.02%

MD <0.01%

Tape, tuner, aux <0.008%

CD <0.008%

of 1.2 V)

Intermodulation distortion
(60 Hz: 7 kHz; 4:1; SMPTE)

Tape, tuner, aux, CD <0.003%

linputs short-circuited; output 1.2 VI

CD P '

.: MC (low)
MC (high)
MD (low)
MD (high)
tuner, aux

>70 dB
>76 dB
>86 dB
>92 dB
>105 dB
>105 dB

Line amplifier
(terminated into 47K)
Frequency range

Phase charac-

Cross-talk (at 10 kHz)
line inputs (L*— R)
L/R to other inputs

10 Hz - 50 kHz (±0.1 dB)
1.5 Hz - 500 kHz (-3 dB)

<±0.5° (15 Hz - 120 kHz)

<-70 dB
<-80 dB
>4 V/ps

Fig. 18. Circuit for making comparative measurements of differ-
ent types of capacitor.

switched on. Adjust Pi and P* to
obtain exactly + 18.5 V on the
supply rails on the mother
board.

Next, measure the direct
voltage at the output (pin 6) of
the LF411 (IC 3 ); this should not
be more negative than —14 V. If
it is, lower the value of Ris till
the reading is —14 V. This
voltage depends to a large ex-
tent on what make of input tran-
sistors is used; normally, R 15
need not be altered from the

stated value. As a safety check,
measure the direct voltage at
the output (pin 6) of IC 2 : this
should be not more than 5 mV,
and preferably 0 V.

The preamplifier should amply
meet the specifications given
earlier, which are minimum
values. The prototypes ex-
ceeded the figures given in
almost all cases: for instance,
distortion measurements §ave
values that were only about half
the figures stated. H

1.53

ELEKTOR INDIA
TEST EQUIPMENT

As reported elsewhere in this
issue, this month we start a
regular series of reviews of a
variety of test and measurement
equipment. The series starts
with a review of a number of
dual-trace oscilloscopes, and
will continue with storage
oscilloscopes, signal gener-
ators, power supplies, multi-
meters, frequency counters,
pulse generators, LCR meters,
and more. Since it is, however,
appreciated that many readers
in schools and small
workshops, laboratories and
electronic design centres re-
main interested in constructing
some test equipment them-
selves as an attractive alterna-
tive to the more costly commer-
cial equipment, we thought it
helpful to remind you all of the
number of test equipment pro-
jects that have been published
in Elektoi India over the past
few years. The accompanying
photograph shows that the ma-
jority of the Elektor India instru-
ments are housed in a standard
Verobox enclosure, which
makes for a neat and uniform
appearance.

A comprehensive
series

Shown to the left in the photo-
graph is the LCR Meter on top
of the Computerscope. Below
in the centre stack is the Loud-
speaker Impedance Meter.
Then come the Microprocessor
Controlled Frequency Meter,
the True RMS meter, the Digital
Sine-wave Generator. The 2-
channel and standard, single-
channel, version of the VLF
Add-on Unit for Oscilloscopes
seen on top of the stack are
housed in flat Verobox enclos-
ures. The right-hand stack is
composed of the Pulse Gener-
ator at the bottom, supporting
the Digital Capacitance Meter,
the Dual Variable Power Supply,
the Function Generator, and the
Spot Sine Wave Generator. Seen
in front are, from the left to the
right, the Altimeter/Barometer,
the Autoranging Digital Multi-
meter, and the Temperature
Probe plugged into a DMM.

No attempt was made to photo-
graph all published items
related to electronic test and
measurement— not shown for

instance, are the analogue
Capacitance Meter, the Audio
Sweep Generator, and a host of
smaller projects for testing
components, AF, RF and digital
circuits.

Overview of publications:

■ Audio Sweep Generator.
December 1985.

■ Autoranging Digital Multi-
meter. July 1987,

■ Capacitance meter (digital):
March 1984.

■ Capacitance meter (ana-
logue): June 1987.

■ Computerscope'. November
1986 and February 1987.

■ Digital Sine-wave Generator.
March 1987.

■ Function Generator. January
1985.

■ Loudspeaker Impedance
Meter. October 1986.

■ Microprocessor-controlled
Frequency Meter.

February 1985, and
March 1985.

■ Pulse Generator. May 1984.

■ RLC Meter. March 1985.

■ Spot Sine- Wave Generator.
June 1987 and July 1987.

■ Temperature Probe for

DMM'. January 1987.

■ True RMS Meter. January
1987.

■ Variable Dual Power Supply.
May 1986.

■ VLF Add-on Unit lor
Oscilloscopes'. March 1987.

uihat's yjatb?

The most 'interesting' figures on
the specification list of an audio
power amplifier are those relating
to the rated output power. This
article reviews the various kinds
of watt that one can meet in a
specification. Since the purpose
of using the amplifier is to
reproduce music at a 'correct'
level, it will also be necessary to
consider the efficiency of the
loudspeakers that are to be driven.

It is rather too easy to manipulate with
the ‘watts’ in the power-amplifier
specification to produce an inflated
rating. The idea is to sell a relatively
low-power job to the unwary - at a
high-power price - on the premise that
all the fellow wants is a higher watt-
rating than the chap next door. This
technique has been developed to such a
fine art that there are even protests
from within the industry - from re-
sponsible manufacturers and their as-
sociations - hampered, unfortunately,
by the fact that it is not immediately
obvious just what is a realistic watt-
rating.

Well, . . . what’s watt?

It seems logical to assume that the
maximum ‘undistorted’ sound level a
given combination of amplifier and
loudspeakers will produce depends on
the maximum amount of *undistorted’
drive power available.

The assumption is correct, up to a point

- the point at which the loudspeaker
becomes the factor limiting a further
increase in the ‘undistorted’ sound
pressure.

Whichever factor sets the limit, there
comes a setting of the gain control at
which the reproduction is no longer
‘undistorted’. Some listeners immedi-
ately detect this as a Tough edge’ to the
loud music passages, others actually like
the effect — and happily turn the ‘fi’ up
‘hi’er.

When the system really saturates (so
that there is quite unmistakable severe
distortion) the usual reaction is to
assume that the power amplifier is
‘clipping’. That may well be - but it
‘ain’t necessarily so’. The discovery is
invariably made too late, after an invest-
ment in new parts or in a new ready-built
amplifier of higher rating has failed to
noticeably increase the available
‘racket’. What has happened is that
more watts have become available for
heating up the speaker’s drive-coil (and
possibly tearing the cone loose from its
moorings). This can easily mean a
further considerable investment — and
this time without a trade-in!

It is one of the physical facts of life that
a high quality loudspeaker of reasonable
dimensions inevitably has an efficiency

- i.e. the ratio of acoustic watts de-
livered to electrical watts consumed -
in the order of 1 ... 5%. The balance is
simply waste heat!

The distortion in the sound radiation
from a loudspeaker, as a function of the
applied drive-power, is a difficult thing
to measure. One therefore rarely finds
figures on this in the manufacturer’s
published specification. The situation
regarding permissible drive power seems
to be this: there are two limiting factors
to the drive power a given loudspeaker
will ‘accept’; there is the instantaneous
peak power input at which saturation-
distortion or even actual mechanical
damage will occur, and there is a con-
siderably lower continuous power level
(certainly in the case of mid-range and
tweeter units) at which the continuous

heat production causes the maximum
allowable temperature rise in the
‘motor’ (i.e. the moving coil). A
measurement with a steady sinewave as
loudspeaker drive will encounter the
latter limit first, so that some kind of
‘tone burst’ seems to be required. The
duty-cycle of this tone burst needed to
bring the limits together would have to
be determined for each type of loud-
speaker tested and quoted in the specifi-
cations — assuming that this is meaning-
ful to the customer working out the
permissible amplifier rating!
Manufacturers would clearly prefer a
standardised procedure that would
enable dissimilar units to be compared
by prospective users. Presently used test
signals are therefore obtained by
‘frequency-weighting’ a wideband noise
signal until its spectral power-density
(both ‘instantaneous peak’ and ‘con-
tinuous’) corresponds to that of ‘typi-
cal’ music (whatever that may be). This
solves the maximum-power problem
nicely — but not the distortion-measure-

If the customer is going to use a power
amplifier capable of overheating (or
mechanically overdriving) any of the
loudspeakers in the system, he will
simply have to refrain from doing silly
things with the volume and tone con-
trols. Damage rarely occurs before
severely-distorted reproduction has
given fair, warning . . .

Amplifier sinewave rating

The amplifier’s ‘continuous’ or ‘sine-
wave’ rating is, to put it crudely, its
heating-ability. The rating is obtained
by having the amplifier deliver a steady
sinewave output of specified frequency,
into its rated load resistance - at a level
for which a specified small deviation
from the input waveform (i.e. a speci-
fied amount of distortion) is caused by
non-linearities in the output circuit.
Manufacturers normally specify a level
that the worst product made (due to
component tolerances etc.) will reliably

A stereo power amplifier is invariably
eleklor India January 1988 1 .55

m

rated on the basis of 'both channels
driven’ simultaneously — the situation
that makes the severest demands on the
power supply circuits.

What one actually measures in this test
is the maximum average power, equal to
the product of ‘effective’ (‘RMS’) volt-
tage across and ‘RMS’ current through
the load resistor. The Root /Mean Square
value of a time-varying quantity is its
mathematically-derived ‘effective value’:
the value of a steady direct voltage or
current of the same heating ability. The
intermediate values within a representa-
tive time-interval are ‘squared’, then the
squares are ‘meaned’ (averaged) and the
‘root’ of this average taken as the result
(‘the root of the mean of the squares’).
For a sinewave the RMS value is known
to be ‘one over root two’ (about 0.71)
times the peak value.

One occasionally encounters a ‘con-
tinuous peak’ power rating. It is the
product of peak voltage and peak cur-
rent (i.e. ‘squarewave power’) and is
precisely twice the sinewave rating - its
only claim to (commercial!) merit.

The value of a ‘continuous’ rating is that
it enables one to make objective com-
parisons between different amplifiers.
It also provides a ‘reference’ output
level at which a distortion measurement
(necessarily a steady-state operation)
can be carried out. Assuming that the
system limitation is not in the loud-
speakers, since if it were the whole
matter would become rather compli-
cated, the question can be raised: to
what extent is the sinewave power
rating of an amplifier relevant to its
ability to deliver an undistorted music

The waveform of a music signal is rarely
even remotely similar to a sine wave-
form. The ratio of peak value to RMS
value (the ‘crest factor’) can exceed
15 dB for much of the programme, de-
pending of course on the kind of music
involved and on the extent to which
dynamic-range compression has been
applied during recording and trans-
mission. When the music signal is driving
the amplifier momentarily just to its
peak output (i.e. genuinely undistorted
full-drive), one may assume that the
average power delivered will be well
below the amplifier's continuous rating.
Let us not complicate matters by trying
to account for the effect of current
limiters in the output stage. The simple
situation is that the amplifier’s peak
power capability is determined by the
momentarily available supply voltage.
There will come a point (see figure 1)
at which the ‘on’ transistor ‘bangs its
head’ against the supply rail - the wave-
form being flattened (‘clipped’) by the
inability to go higher.

Music power rating

The specification sheets of many com-
mercial amplifiers give not only the con-
tinuous power rating, but also the
‘music power’. This latter figure is then
always higher than the continuous fig-
ure. The music power rating does not
follow from any standard measurement

procedure; it is simply an indication by
the manufacturer of the output power
his amplifier will momentarily deliver
(i.e. during instantaneous peaks in the
music signal).

One must therefore be careful when
comparing amplifiers on the basis of
their music power ratings. On the other
hand, the rating is quite relevant to the
unit’s performance in a practical situ-
ation and cannot be dismissed as a mere
commercial trick.

The essence of the ‘music power’ con-
cept derives from what (watt) happens
when the amplifier’s power supply cir-
cuit is not voltage-regulated. The situ-
ation is that an undriven class B output
stage draws only a relatively small
standing or ‘quiescent’ supply current,
so that the fairly hefty reservoir capaci-
tor has no difficulty in providing an
almost ripple-free feed voltage close to
the peak value of the transformer
secondary ‘open’ voltage. When drive is
applied there will be a tendency for the
feed voltage to drop (and for the ripple
to increase) — causing the ‘clipping
level’ of the amplifier to fall. This
process takes time however (because of
the aforementioned hefty reservoir ca-
pacitor) — so that a momentary full
power demand will be met at full volt-
age. Only when the average demand
becomes appreciable will the supply
voltage reduction noticeably reduce the
available output power. Note that the
relative power reduction is roughly pro-
portional to the square of the relative
voltage reduction, because a reduced
voltage swing inevitably means also a
reduced current swing - and the
product of voltage and current is power.
Figure 2 illustrates the on-load behav-
iour of the simple supply circuit of
figure 3 . Charge flows out of the reser-
voir at a rate proportional to the current
demanded (charge is measured in
ampere-seconds). The charge loss has to
be made good by a surge-current, that
occurs one hundred times per second,

Figure 3. A typical unregulated power supply

shown as R is in fact due to the copper-

reservoir electrolytics will enable a longer
•burst' to be met at full power - but the

whenever the instantaneous secondary
voltage (minus the drop in the rectifier
diodes) exceeds the voltage across the
capacitor. The internal resistance of the
rectifier circuit (actually the effective
‘copper resistance’ of the transformer
windings) determines the magnitude of
these surges - and therefore the drop in
supply voltage that must occur with a
given combination of capacitor value
and load current. V, is the no-load (or
better ‘quiescent load’) supply voltage;
V 2 is the considerably lower full-load
voltage (continuous full drive). The
charging process occupies a greater part
of the hundredth-of-a-second (mains
half-wave) interval - and the voltage
drops much faster during the full-load
discharge process, it will not be difficult
to see why power-electrolytics have a
•permissible ripple-current’ rating in
addition to their nominal capacitance!
The designer of the power supply has to
make a difficult choice here. A very low
transformer winding resistance (both
primary and secondary) will make for a
very ‘good’ supply. It unfortunately also
means a relatively bulky and expensive
transformer — and a more violent
‘switch-on’.

Note that providing electronic regu-
lation of the power supply circuit will
enable the ‘continuous power’ to be
made equal to the ‘music power’ rating
- but at the price of more transformer,
more electrolytic and more heat sink!
The only advantage of regulation is that
the output stage can be continuously
operated closer to the transistor voltage
maxima, without requiring allowances
for mains voltage tolerances. In return
for the hardware investment one
obtains, in essence, that a power rating
slightly higher than even the permissible
‘music power’ can be guaranteed under
all load conditions. This may be justifi-
able under certain professional circum-
stances.

After all that . . . what's watt?

The ‘continuous’ and the ‘music’ power
ratings of an amplifier give information
that is relevant to the unit’s ability to
deliver an undistorted audio signal.

All other power ratings, such as ‘square-
wave power’, ‘peak music power’,
‘±2 dB power’ etc., reflect more upon
the abilities of the advertisement copy-

The amplifier’s power rating is by no
means the only parameter - or even the
most important one - relevant to the
enjoyment of undistorted music repro-
duction. M

1.58

selex

everyone must think of his
own procedure for fixing the
meter and the circuit.

You can buy any center zero
meter with 50-0-50 pA
rating, that is, a meter
which has a zero in the
centre of the dial, -50pA on
left side full scale, and +50
pA on the right side full
scale of the dial. As the
accuracy required is not
very critical you can even
use a cheaper centre zero
meter used in radios and

The left and right full scale
points of the scale are to be
marked with -30A and
+30A,

indicate charging as well as
discharging current from
the battery. After completing
all the connections, the

switched on. For alignment,
we can use the current that
is used by the dimmers.
First withall lights switched
off, the zero adjustment is
used to set the needle of
the meter to zero. Then the
dimmer is switched on.
knowing the power required
by the dimmer is necessary
to calculate the current
drawn. 45/40W systems
generallydraw about 8.5 A
in the dimmer position and
60/55 W systems generally
draw about 1 1 A in dimmer
position. -

To avoid misinterpretation
of the current drawn, it is
better to insert a paper
between the ignition
contacts during calibration
of the meter; so that the
current drawn is only the
current for dimmers. The
needle of the meter swings
towards left, showing that
the battery is supplying
current. The potentiometer

is adjusted so that the
meter reads the known
value in ampers on the dial
marked form 0 to -30 on the
left side.

Now to see how the
charging current is
indicated by our meter, first
remove the paper that was
inserted between the
ignition contacts. Start the
engine and keep it running.
The starting current is quite
large but it does not
damage the meter as we
have connected a diode
across the meter in our
circuit. ?The diode is
connected with cathode at
plus pole and anode at the
minus pole of the meter.

The charging current can be
checked even with a
battery charger, with the
minus pole of the charger
connected to the common
earthing point and the plus
pole connected to the plus
pole of the battery.

Ml =± 50jiA Center Zero meter.
Di = IN 4001 diode

Figure 3:

Photograph of the
charging/discharging current
measuring circuit.

1.59

POWER AMPLIFIER

selex

"I want to build a power amplifier for my cycle!"
"A power amplifier?”

"Yesl"

"For the bicycle?"

"Yes. I want more power from the dynamo, so that I
can connect more lights to it, or I can get a more
powerful headlight."

"Oh, If you think it was so easy, why no one else has
thought of it before?"

”1 don't understand myself, why no one else thought of

"Because it is not practically possible. You can t
amplify the power of the dynamo with an amplifier. You
must install one more dynamo if you want more
power."

"But, with two dynamos, I have to work harder driving
my bicycle."

"That’s how it is. You cannot get more power out of
anything without putting more power into it. Not
evenfrom an amplifier."

"Then why do you call it a POWER AMPLIFIER?"

’’An amplifier amplifies power, it does not generate
power. It can amplify a weak signal with the help of c
additional power supply, the signal from the record
player or the cassette player is too weak to drive the
loudspeaker, so it is amplified by the amplifier, and it
draws the necessary power from the power supply."

"Exactly, something like that I need for my dynamo"

"Then you will also need a power supply for your

1.60 elektor india January 19S8

Dynamo Amplifier, and you will have to connect it to
the mains!"

"Oh, well, but if I could connect the mains supply to my
cycle. I wouldn't need the dynamo either. I can connect
the headlight diretly to the mains"

"You are right, moreover, the output power of an
amplifier is much smaller than the input power.”

"You mean power is lost in the amplifier?"

"Yes, a 90 + 90 W stereo amplifier takes about 320 W
power from the mains and the remaining power is lost as

"Heat is also power?"

"Naturally, power is required for generating heat"

"Now I understand, the power input is equal to the
power output and the losses put together"

"Unless the device stores energy."

"Like an accumulator?"

"Yes. you are right, but even in that case, the stored
energy is later given out by the accumulator. If you take
this power output into consideration, the effective
output will always be equal to the input."

"Does your stereo amplifier always consume 320 watts
of power? That's a lot of power for an amplifier."

"No, it does not always consume that much power. It is
the specified power input when it is actually delivering
the speciried powre input when it is actually delivering
90 + 90 Watts to the speakers. Generally it operates at
much lower output power, and the power drawn from
mains is also just what is required."

NEW PRODUCTS • NEW PRODUCTS • N

DIGITAL DISPLAY DD-3

"Aqeel Enterprises has
introduced Digital Delay
DD-3 for Entertainment &
Orchestra Programme. This is
analog type using BBD delay
System. The delay time can
be varied from 20 ms to 500
ms as per specific
requirement. For musical
notes of longer duration long
delay will be needed where as
notes changing at a faster
speed lesser delay time. All
this is possible by controlling
the 'DELAY' control and
'REPEAT' Control.
Microphones inputs have been
provided for Misc use.

The Digital Delay DD-3
employ the latest and most
advanced design and
circuitory. Excellent
performance and stability
under extreme operating
conditions and voltage
fluctuations is ensured to
maintain high quality and
satisfaction for the user.

The Mixer can be put to
varied uses. A good artist can
achieve excellent sound
effects by selection of various
controls of the mixer.

There are different models to
suit different requirements
(STEREO & MONO).

For further details please
contact:

M/s. AQEEL ENTERPRISES
404, Gali Matia Mahal,

Jama Masjid,

Delhi 110006.

Phone: 267902

PROXIMITY SWITCHES

Hans Turck GmbH & Co. KG.,
situated at Mulheim in West
Germany manufacture
Inductive and Capacitive
Proximity Switches.
Proximity Switches with
sensing distance upto 60mm.
and with other technical
parameters are available for
use in every application.

For further information
please contact:

ARUN ELECTRONICS
PVT. LTD.

2-E Court Chambers
35 New Marine Lines
Bombay 400 020
Phone: 259207/2521 10
Telex: 1 1-6136 PREN IN

JOYSTICKS

"Datec Pilot" computer-
compatible-joysticks are
are reported to be only
indegenously manufactured
joysticks for personal
computers. The joystick is
useful add-on for personal
computer users in defining
X, Y co-ordinates in CAD/
CAM programs, various
controls, picture disposition
and of course in spare time,
for playing games.

At present three types of
joysticks are manufactured.

* "Datec Pilot pc" for IBM
PC & PC/XT compatible,

* "Datec Pilot bb" for BBC &
SCL Unicorn,

* "Datec Pilot ap" for Apple
II computers.

The Datec joystics is
indigenous. It does not need
any interface and plugs
directly to the game I/O port
or the Analogin port of the
computer. It is housed in a

sturdy cabinet and has sober
colours to match computer
environments. It has
proportional-control and
omni-directional capability. It
has an autocentering
mechanism and is built for
easy handling and smooth
operation.

For further information
please contact:

DATEC INDIA
3/23 Desai Building
83 Mugbhat Lane
Bombay 400 004
Phone 342787

LUXMETER

OPTO India has introduced
sensitive and Portable.
LUXMETER for
measurement of light levels.
This is suiable for all
photometric measurement in
science and research as well as
quality testing labs.

Its response is claimed to
meet with internationally
accepted standard Cl E
observe's curve (equivalent
to average-human eye
response) with cosine

correction. The range of the
instruments are 0-1999,
0-19990, 0-199900.

For further information
please contact:

AG A RIVAL SALES
ENTERPRISE
34, Ganesh Bazar
Jhansi 284 002

PCB TERMINALS

Asia Electric Company have
now introduced PCB
Terminals which are specially
designed for electronic Printed
Circuit Boards. Named as
Type MUT 2.5, these
individuals can be stacked
together, for the required
number to form a Multiway
suitable for international
standard module dimensions.
The connection is by
soldering pins on the Printed
Circuits Board and screw
clamping the wire
termination. The size of the
conductor is upto 2.5 sq. mm
and is rated at 500V-15
Amps. The housing is
moulded from special grade
Industrial Polyomide.

For further information
please contact:

ASIA ELECTRIC COMPANY
Katara Mansion, 132A,

Dr. Annie Besant Road, Worli
Naka, Bombay 400 018

NEW PRODUCTS • NEW PRODUCTS • N

MOTOR DRIVER
The L6202/03 is a high
efficiency mixed technology
motor drive 1C (60V, 5A).
MULTIPOWER BCD is a new
technology which combines
bipolar, CMOS and POWER
DM OS on the same chip.
Both, technology and circuit
have been developed by SGS.'

For further information
please contact:

M/s. SGS

SEMICONDUCTORS (PTE)
LTD.

28 Ang Ko Kio Industrial
Park 2, Singapore 2056

HIGH PRECISION DC
SHUNTS

High Precision DC Shunts
with accuracy class 0.2
calibrated on Micro-Processor
based Test Bench is now
available. Temperature
stability in the order of 10
PPM ohms. Ratings upto
2000 Amps available, with
75 mV.

For further details please
contact:

AUTOMATIC ELECTRIC
LIMITED

Rectifier House, Wadaia
P.O. Box No. 7130
Bombay 400031
Phone 4129330
Telex 11-71546

IONAIRE

"lonaire is an electronic
negative-ionized-oxygen
generator manufactured with
knowhow from Innovative
Systems, USA which creates a
fresh, invigorating and clean
atmosphere by
ionconditioning and cleansing
the air of all pollutants and
suspended particles. Health-
giving ionized oxygen, which
is depleted from the air due
to various factors like
pollution, is replenished by
this device, lonaire finds
application in offices,
photographic and other
laboratories, computer rooms,
homes, restaurants, hospitals,
clinics etc."

For further information
please contact:

M/s. ZEEBEETRONICS
16, Commissariat Road
Bangalore-560 025
Phone: 572365

MARKEM PRINTER

The 527 system is designed
for small production runs as
well as special or pilot lot
applications. Capable of
printing up to a 1" x 2"
(25.4mm x 50.8mm) area,
the 527 will mark your DIP'S,
card edge connectors and
other large components
having at least one flat
surface. Print quality and
registration are maintained

by means of easy adjustments
and a precision worktable
assembly.

Motor driven and actuated
by a foot switch, the model
527 will cycle at rates of upto
3000 per hour. The ink plate
system is compatible with the
entire range of MARKEM
inks and is extremely easy to

Specifications: Imprint area
1" x 2" (25.4mm x 50.8mm),
Max. part thickness 1-3/8"
(34.92mm), Cycle rate Upto
3000 cycles/hour. Mount
Bench, Weight (approx.) 35
lb (15.9 Kg.).

For further information
please contact:

KELL Y CORPORATION
14 13, Dalamal Tower
Nariman Point
Bombay-400 021
Phone: 244286
Telex: 1 1-5858 KELY IN

ELECTRONIC
SOFTSTARTERS
Jeltron series LC1
manufactured in technical
collaboration with M/S.
Motortonics, Inc. of U.S.A.
are Low Cost High
Performance Electronic
Softstarters for three phase
induction motors. The LC1
applies a gradually increasing
voltage which in turn provides
a smooth, stepless, adjustable
acceleration at the time of
starting the motor. A second
starting ramp is available as
an option for the applications
where the mtoor has to start
with different loads at
different times. Also, for the

friction loads which stop tc
abruptly with a jerk, an
adjustable smooth stop
option is available which
ramps down the applied
voltage linearly in a
predetermined time. The
starting torques and start
times for both the start
ramps as well as the stop time
e field settable. These
starters are available for
motors ranging from 2-700
HP.

For further information
please contact:

M/s. JELTRON
INSTRUMENTS INDIA
PVT. LTD.

6-3-190/2, Road No. 1
Banjara Hills
Hyderabad-500 034

AUTO RANGE PANEL
METER

PRESTIGE ELECTRONICS
introduce their Autoranging
digital Panel Meter Display
is 3% Digit 12.5mm Red,
Green or Yellow. Range
selection is automatic
depending on input voltage.
Ranges are 1.999V, 19.99V,
199.9V & 750V DC overall
accuracy is 0.25% ± 1 Digit
for DC & 0.7% ± 1 Digit for
AC models. Dimensions are
48 x 96 x 190mm (’/a Din
size) Cutout 45 x 96mm.
input supply is 230V ± 10%.

For further details contact:
PRESTIGE ELECTRONICS
62/A, Push pa Park, Mai ad (E)
Bombay 400 097
Tel: 693805

:w PRODUCTS • NEW PRODUCTS • NEVi

TAMAYA DIGITIZING
AREA LINE METER

Planix 5000 Area Line Meter
Works on a totally new
concept developed through
unconventional approach
leading to unsurpassed
performance standards.

The rotary encoder and
the state-of-art electronics
makes Planix 5000, easiest,
fastest area Line Meter. This
Meter allows you to measure
area and the length of the
line. The standard lines are
easily measured by simply
setting the trace point at each
intersection of the figure and
the rest is done by the built-
in computer with a resolution
of 0.05 mm; length of curve
line needs to be traced, for
measuring.

Planix 5000 is a TOTAL
STATION for the draftsman.
In addition to its own
microprocessor, PLANIX
5000 will interface with the
large computer or other
RS-232C compatible units.
PLANIX 5000 is a compact
cordless instrument operating
on NiCd Batteries and comes
in a carrying case.

For Further details please
contact:

TOSHNI-TEK
INTERNATIONAL
267 Kilpauk Garden Road
Madras 600 010

SPIKEBUSTER
MAGNUM ELECTRIC
COMPANY PVT. LTD. has
introduced a voltage spike
and noise suppression outlet
strip called SPIKEBUSTER.
It consists of an EMI/RFI
filter and a voltage spike
protection circuit built into

a power strip with three 5
Amp sockets and a control
switch. By plugging
SPIKEBUSTER into the
electricity mains and your
sensitive electronic equipment
into SPIKEBUSTER.
electrical noise and voltage
spikes are totally prevented
from reaching the equipment
and damaging it or causing it
to malfunction. Uses are for
colour TV sets, VCRs,
computers, computer
peripherals, medical
equipment, electronic
instruments, communication
systems and other device
containing sensitive integrated
circuits. The company
specialises in power protection
equipment and will soon be
coming out with a lowpriced
standby battery back-up
system aimed at the desktop
computer market.

For further information write

MAGNUM ELECTRIC
COMPANY PVT. LTD'

2 Ramavaram Road
Manapakkam
Madras 600 089

THICKNESS GAUGE
General Tools offer a coating
Thickness Gauge. For
measurement of a non-
magnetic coating on a
Magnetic metal.

Application Measurement
of following nonmagnetic
coatings on magnetic metals.

1) Plating— Gold, Copper,
Zinc Tin Chromium, Lead
etc.

2) Coating-Paint, Resinous
coating. Metallic Coating.

3) Lining— Resin, Rubber,
Paper or any other films of
non-magnetic material can

j be measured when placed on
steel base metal.

BARREL PUMP (HAND
OPERATED) FOR
CHEMICALS & OILS

A hand pump, in all plastic
construction, namely
Polypropylene (PP) and
Thermoplastic Polyester
(PBT), is introduced for the
first time in India. It is ideally
suitable for transfer of
chemicals and oils from
barrels, carbouys, jerry cans,
jars etc.

The pump in PP is used for
transfer of Acids like
Hydrochloric, Sulphuric
(Upto 80%) Nitric (Upto
70%), Phosphoric, Acetic,
Chromic, Spent Acids etc.

It is also used for Inorganic
Salt Solutions, Hypochlorite
and for Vegetable and Mineral
Oils and certain Organic
Amines.

The pump in PBT is used for
all types of Aldehydes,

Ketones, Glycols, Alcohols,
Petroleum products and Oils,
Acetone and Aniline and their
derivatives. Benzene, Toluene,
Xylene arid their compounds,
liquid perfumery products |
and pesticides, DDB, LAB, I

Hexane, Liquid Paraffin and
other Acetates, Plastcisers,
Chlorinated Solvents, Polyols,
Isocyanates etc.

In general these pumps are
ideally suitable for transfer of
liquid chemicals and oils from
barrels and carbouys. They
offer suction lift of 3 mts,
discharge heads of 15mts and
capacity of 30 Ipm.

They are extensively used at
industries like chemicals,
textile processing,
pharmaceuticals, pesticides
formulation, electronics, PCB
Mnfg., sugar mills, dye stuff
mnfg., etching plants,
degreasing plants, research
labs., offset presses,
installation where oils,
kerosene, diesel are used, and
all other places where
chemicals and oils are
handled.

*7

For further information
please contact:
CHEMINEERS
6 Jagnath Plot
Rajkot 360 001
Gujarat State, India.

:w PRODUCTS • NEW PRODUCTS • NEW

DATA SCANNER

Advani-Oerlikon have
developed a mini
microprocess-based data
scanner called UDS-30. This
30-point scanner is designed
for scanning of temperature,
voltage or any other
parameters of water and
steam boilers, windings of
HP motors and high voltage
transformers, distribution
points in silos containing
foodgrins, engine test and
reaction vessels in chemicals
and process industries.

The system is field proven,
versatile and compact. It is
mounted in a standard RA 19
rack. It can accept
multi-variable inputs such as
Thermocouples, RTDs and
Analogues. The system has
built-in 24 columns, an
alphanumeric 2 colous printer
with re-rolling facility which
gives out print out of scanned
data and programmed
parameters. The keyboard
functions such as low level
set point, control level set
points, dwell time, high level
set point, channel number,
hysterisis, etc. are
programmable individually
for each channel. Display
annunciation is provided for
each channel. There are
totally 90 LEDs. Each channel
has a seperate indication for
alarm, senor break and
control status. The system
also has the facility to scan
alarm conditions on a priority
basis. Output relay contacts
are provided for each channel.
One relay is provided for
common alarm and one for
senor break indication.
EEPROM memory is used
and hence no battery back up
is required for the programme.
A real time calendar is also
provided which gives date,
month, year, day of the week
and time. Nickel cadmium
battery is provided for the
back-up of the calendar. The
system uses a floating point
arithmetics for linearisation

and other mechanical
calculations.

Solid-state semiconductor
switches are used for
multiplexing, thus
contributing to reliability and
compactness. STD cards are
used for flexibility of
operation and ease of
maintenance, thus ensuring
minimal downtime. The
plug-in PCB and the STD
mother board have minimised
wiring in the instrument. The
unit has a hinged transparent
unbreakable cover on the
front space to avoid any
accidental changes in the
keyboard function.

For further information,

quote ref: PUB/2, contact:

ADVANI-OERLIKON

LIMITED

Post Box No. 1546

Bombay 400 001

SPECTRUM ANALYSER
ROFIN-SINAR LASER UK
LTD, announce the
introduction of the high
speed RSO 6240 Spectral
Processor to operate with the
current line of Optical
Spectrum Analyser
equipment. The new
instrument includes a more
powerful processor, together
with many system
improvements such as dual
double-density double-sided
3'A" disc drives, an improved
monitor, and digitising
electronics.

The entire system has been
repackaged with an integral
keyboard instead of the
earlier seperate keyboard. In
addition various accessories
and software packages have
been added to provide a very

powerful package to measure
transmission, absorption,
reflection and colour, in
addition spectroradiometric
and software package. The
system captures a complete
spectrum in 5 msec and stores
it in 80 msec in the processor.
The wavelength range is
200-5000 nm which can be
covered at one time using the
"merge" software facility.

For further information,

TOSHNI-TEK
INTERNATIONAL
267 Kilpauk Garden Road
Madras 600 010.

THERMOCOUPLE
VACUUM METER
The IBP Thermocouple
Vacuum Meter is a simple,
single head measuring device.
SPECIFICATIONS
Gauge Head: Chromium
plated brass with octal socket.
Vacuum Connections:
Through standard 6 mm
screwed union.

Measuring Range: 1-1000
Microns.

Calibration: Calibrated for
dry air using a Mcleod gauge.
Power Supply: 230 Volts, 50
Hertz, ± 10%.

Dimensions: Small, compact
construction with simple
panel installation in Standard
half module (H 135 mm x W
210 mm xD 145mm)
Standard accessories supplied:
Gauge head with cable of
length 3 Metres.

Applications: Used in
Industrial Systems,
Refrigeration Industry, Flask,
Lamps, Capacitors and
Condenser Industries etc.

For further information
please contact:

IBP CO. LIMITED
A Govt, of India Enterprise
Engineering Division
Sewri (East)

Bombay 400 015.

"ROCKER TOGGLE"
SWITCH

I EC has just introduced a
range of "Rocker Toggle"
switches with Black, Red,
Blue, White, Yellow or Green
colour knobs.

These Rocker Toggle switches
are available in 6A, 10A, 15A,
250V AC or 28V DC in single
and double pole with on-off,
changeover with or without
centre off and momentary
contact, to serve as Push
Button. Special circuits are
possible e.g. 1,2,3 or 1, 1+2,
2+3, etc., avoiding the need
of 2 or 3 switches.

Switches are supplied with
screw terminals or push-in
terminals (6|,3mm).

For further information
please contact:

INDIAN ENGINEERING
COMPANY

Post Box 16551, Worli N aka
Bombay 400 018.

IV WEST - 228

£harn|7mn El \ ee\rnmiis V\A. LM

S-17, M.I.O.C. Bhosari, Pune 411 026. India. (0212) 82682, 83791 Cable : CHAMPION
Telex: 0146-343 CHMP IN. 0145-333 MCCI IN. 0145-505 MCCI IN.