A Very Concise History of Test Cards

by

Frank Mitchell

Television started in the UK in 1936, and it was quickly recognised that a test pattern to assist dealers with the setting up of receivers was necessary. It was not until after the war, however, that the first test card was actually broadcast; indeed, prior to the war, only tuning signals had been used, the example below being in a 5:4 aspect ratio.

Various test cards had been in use for internal studio and engineering checks, and these were designated by a numbered sequence. The first transmitted trade test card, however, was given the identification "Test Card A" to distinguish it from the studio patterns which were "Test Card 1", "Test Card 2", and so on.

The most important features for a broadcast test card were thought to be a resolution test and a linearity test, so "Test Card "A" consisted mainly of frequency gratings and a circle. There was also a Test Card "B" which was basically the same design, but with an Ilford panchromatic test strip added across it to give a contrast test scale. So far as is known, no copy of Test Card "B" survives. Test cards "A" and "B" were only transmitted for a short time during the day, a demonstration film being shown each morning.

The early post-war years brought a considerable increase in the numbers of television receivers within the London area, and consequently a lot more work was provided for dealers to set them up. A new industry had been born! Many personnel in the armed forces had been trained in radar during the war, and they formed the backbone of the new industry, both as receiver engineers working for dealers, and as manufacturers.

It may seem strange to people nowadays that in the forties and fifties you couldn't just buy a television, take it home and switch it on. No, it had to be carefully aligned and set up!

This was long before the days of transistors and printed circuits. Televisions were largely hand wired and assembled, using only valves. Reliability was somewhat doubtful, and it was very rare for the set to work when first switched on! Even if it did work, there were adjustments for height, width, linearity, synchronisation, contrast and focus to be made. The set took several minutes to warm up, and during the warm up period the picture could vary quite a lot!

I remember my father bought a GEC television in 1952. This was a 12" table model from one of the larger and more experienced manufacturers. We had five sets before we got one that worked, and even that was returned for repair about once a week for some months, until a design modification improved reliability so much that it worked for years afterwards, with only periodic replacement of the line output valve. GEC, a pioneer of television, persisted in using its own 'Osram' valves and GEC tubes, manufactured by the M-O valve company. Other manufacturers used 'Mullard' and 'Mazda' valves.

Test Card "A" was no longer considered suitable for the setting up of receivers and a more comprehensive test card was required. This was met by the design of Test Card "C" in 1947, which in its various forms was to last until the end of black-and-white television.

The original version of Test Card "C" transmitted in January 1948 had an aspect ratio of 5:4, and the circle appeared smaller than in the more familiar version. In the 5:4 version, there were half-height boxes between the horizontal castellations and the top or bottom lines of the linearity grid. When the aspect ratio of the transmitted picture was changed to 4:3 around 1949 (?), Test Card "C" was also changed, and the top and bottom lines of the linearity grid were drawn much nearer the castellations. This made most of the test card appear larger. It is interesting that the size of the circle on the 5:4 Test Card "C" was similar to that on the much later 4:3 Test Card "D".

5:4 aspect ratio Test Card "C"

The logo is not authentic!

Test Card "C" was more a pattern than a formal specification, and there were a great many versions of it. It was produced in the form of a card, a slide (35mm transparency) and as a monoscope. It was also transmitted on film as part of the post-war demonstration film. This consisted of approximately 15 minutes of programme highlights alternating with 15 minutes of Test Card "C" and music, filling two hours each morning.

The monoscope was a cathode ray tube with an image internally etched on to its face. This was electronically scanned by the device, the resulting output produced being that of the image contained within it - a sort of early `electronic test card'. Monoscopes were used for many captions in the early fifties, perhaps the most famous and frequently used being `Normal Service Will Be Resumed As Soon As Possible' !!

All the versions of Test Card "C" differed in some way, particularly in the shade of grey used as the background. On some, this was the same as the light grey step on the contrast wedge, on others it was the same as the mid-grey step or even the dark-grey step. The BBC added centring arrows to its network version of Test Card "C" in July 1958.

When the ITA started, they brought out their own versions of Test Card "C", and it is to their credit that their new series of Test Card "C" slides introduced about 1959 were consistent for all transmitters.

In the early sixties it was recognised that a test card required to be designed and transmitted to a consistent standard, and with the ITA transmitting its version and the BBC transmitting at least three versions, this was not the case. A new test card was then designed, and the requirement for a 625 line card was also accommodated.

The new consistent test cards were Test Card "D" for 405 lines and Test Card "E" for 625 lines, both introduced in 1964. There is some doubt about the exact day "D" first appeared, but "E" was used on the day BBC2 started in the London area (20th April). These were identical except for the frequency gratings which were much finer for 625 lines in view of that system's ability to display finer detail. The frequency gratings were also graduated instead of being just black and white lines, resulting in a sinusoidal waveform instead of a square wave. When using test equipment, this was more suitable for the service engineer.

In the sixties, the test card was the only programme transmitted for most of the day (Oh, for these days again!), and was used to demonstrate and sell new sets. The new Test Card "E" did not look any better on 625 lines than its equivalent "D" on 405 lines, as the frequency gratings did not show up the superiority of the new sets. It was unceremoniously dumped after only a very very short period in service, and replaced by the BBC2 version of Test Card "C" again. This had altered frequency gratings but still square-wave as on the original "C". To the layman it looked more impressive!

The frequency gratings on Test Card "D" were also a problem and were altered on 1st December 1965 to improve the contrast. This was simultaneously introduced by the BBC and ITA, and the amended card is identified by dots in the centre of the boxes on each side of the "D".

Only when the colour Test Card "F" was introduced in 1967 did the 625 line service get a standard test card. "F" incorporated a colour picture as well as most of the best features of the earlier test cards.

When colour and 625 lines were introduced on BBC1 in November 1969, Test Card "F" was used, but local opt-outs would use "D" or "C". The ITA/IBA continued using Test Card "D" for each main trasmitter, until that transmitter went over to colour, when "F" was used.

As well as Test Card "F", the BBC from 1971, and initially the IBA as well, also used a modified Philips PM5544 test pattern, which was a commercial product used extensively by set manufacturers as well as many other broadcasting organisations. Before the days of computers this was a complex and expensive "black box" of electronic trickery!

The IBA, for some reason, decided not to continue the PM5544 and instead developed its own pattern called ETP1. This unloved design had no circle, the grid lines did not form a square pattern, and did not form an aesthetic picture. Despite this, it continued to be in use on Channel 4 from its start in 1982 until the advent of 24 hour programmes.

Meanwhile, in May 1984, the BBC's Test Card "F" was transferred to a memory chip and no longer transmitted from a transparency. When this change was made, a few very minor alterations were made to the pattern, principally the style of the "F", the size of the picture within the circle, and the top castellations.

With the advent of 24-hour television on BBC 1, it seemed likely that Test Card "F" would mark the end of the line.  But then, on 20th November 1999, Test Card "J" made its debut.  Clearly based on its predecessor, it included a green square in the "letter box" and flashing pairs of dots on the grey scale.

Test Card "W" is its widescreen equivalent:

Test Cards "J" and "W" are rarely seen. Closedowns are filled with Pages from Ceefax, except when special engineering tests are carried out, generally only once a year.

 

 Articles

Revised: 06/05/08


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