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Test Card Memory Lane |
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Test Card Memory Lane |
This is a selection of Test Cards and similar images used by UK television channels from the 1970s onward. I've tried to include every single pattern I can remember being shown, though I've not created images for all the minor variations that existed.
A variation on TCG used by BBC Wales (that is, BBC1 in Wales) in the late 1970s / early 1980s. This was used in the early afternoon slot, when other BBC1 regions had programmes on and Wales didn't. Specifically, some Welsh-language programmes such as Pobol y Cwm were shown once on BBC Wales and once in other regions. For the latter, BBC Wales opted out rather than repeating the programme, a suggested reason being that these were lean times, and a repeat would have necessitated an extra royalty payment. Whatever the reason, it was somewhat bizarre having Welsh programmes on in other parts of the UK but not the part where the language is spoken!
The caption is superimposed, as with the 'BBC 1' TCF at the top of Part 1, though in this case it's much more obvious. Even though TCG was electronically generated, it was easier to superimpose than to re-engineer the caption, which was 'hard-wired' (actually in EPROM memory).
More minimalism from Granada. A simple grid like this was broadcast first thing in the morning (again with 400Hz tone) in the late 1970s. Closer to startup time, it would change to plain colourbars (I seem to remember the switch being at about 08.00).
Early-morning BBC, prior to the test card. Two kinds of greyscale; one stepped, one smooth. The latter is also known as a 'sawtooth' as that is the waveform required to transmit this pattern. You could have fun with the brightness control when this was on; it made the black area shrink and grow - and indeed this was very much the purpose of that pattern, to check the gain on vision mixers. Mind you, the nice, smooth, rectangular image you're seeing now doesn't really capture the way it looked on a real TV at the time - to me it was a white screen that had been scorched on the left-hand-side, particularly as the greys seemed to have a slight yellow/brown tinge on our set.
Two more to catch in the small hours when the Beeb thought no-one was watching. On the second pattern, the two dashes were sometimes at the bottom rather than the top, sometimes no dashes at all, sometimes a solid line instead of dashes. If you turned the colour down on either of these patterns, the blue areas faded to 50% grey - meaning that the blue band on the right-hand pattern would disappear completely. I've been informed that the blue band contains both colour sub-carriers but without phase alternation on the R-Y signal. The PAL system expects phase alternation between lines (indeed this is what 'PAL' stands for), so it translates the non-alternating signal into an alternating one. It then averages the R-Y signal to zero, leaving only the B-Y subcarrier visible on the screen.
I've learned that the solid line was an earlier version of the pattern. The dashes were a later modification to identify the source of the pattern. Various of the four possible dashes would be present or absent depending on which regional centre generated it: just the top two dashes = Manchester; just the lower two dashes = Cardiff, corresponding to the two regions I could pick up, NW England and Wales. All four dashes together represents Belfast (N Ireland), though you might guess it was London! The assignment is not arbitrary - for example the areas with one, two and three dashes together at the top are Birmingham, Manchester and Glasgow, indicating the northern chain of distribution.
Apparently the dashes could sometimes flicker on and off, due to overheating of the transistors that generated them. I have a vague memory of seeing something like this but I'm not sure.
BBC2 early-morning again. A 50Hz square-wave, which I believe may be the same thing as a 'day/night caption', though I just called it something like 'black and white screen' at the time. Apparently something like this occasionally turns up by accident on digital TV, but with the top half bright green. Note that the change from white to black occurs within the middle line of the picture. If you looked closely, you could see the start-point of the black half judder from side to side a bit. This is because the generator did not wait for a TV line to start before switching from white to black, and since one TV line is transmitted in 0.000064 seconds, tiny fluctuations in the duration of the white pulse became clearly visible.
A pulse-and-bar signal occasionally radiated by the BBC (at least I don't think ITV used it). This might possibly have included a blue pulse on occasion as well.
The thing about these simple, early-morning test patterns was that I never knew exactly what was going to come on each morning, and the change from one to another was always abrupt - no gap, and no fade-out or fade-in. Eventually BBC1 and 2 would settle down to their test cards, and Granada to their colourbars, but before that, there was always the potential for surprise. That said, there was apparently a standard "line-up" sequence including at least the greyscale, sawtooth and day/night patterns, which used to precede schools' programmes in the Pie Chart days (see next page), but which evidently continued at least into the late 1970s.
And of course the Radio or TV Times never told you any of this was even on (and after all, why should they?) so it was like a secret world of TV; it was like you were looking in on TV stations waking up, having a stretch and a yawn, possibly a shave and a spot of breakfast, before donning their suits to present stuff to you for the day.
This impression was aided by the occasional snatch of sound accidentally superimposed from the control room. For example, one morning Granada's colourbars and tone were accompanied by part of the episode of 'Joe 90' that was to be the day's first programme, then the tape being rewound very quickly. On another occasion two engineers could be heard over the tone accompanying the half-white pattern, discussing something to do with mixers (the only line I recall being "Is the mixer good enough to...?")
An occasional treat from Granada, and by the look of it, indicative of a network feed. This was never shown in the 'proper' test card hours as far as I recall; it just popped up in the middle of programmes sometimes. I never saw it with any other number than 3 on the caption.
This was sometimes transmitted before the early-morning Open University programmes in the mid-1980s. With tone, I think. Sometimes the 'OU' caption would be in the top-right corner, sometimes in both corners.
I'm a bit dubious about this one. All I can remember is seeing a test card with '625 LINES' on it, that was a bit like TCF but black and white. Mind you we had a black and white set in the early 1970s. This appears to be the only test card with such a caption, other than Test Card E, which was withdrawn before I was born. This is a variant of Test Card C.
None of these images are screen captures. Most of them were created using versions 2.3 and 3.1 of FML's Test Card Maker with some additional processing via MGI PhotoSuite. These pages are for information purposes only. Copyright on images, where it exists, rests with the original owners.
You can download the latest version of Test Card Maker for free here.
