03-11-2022, 09:38 AM
(02-11-2022, 07:27 PM)Bennyboy84 Wrote: youtu.be
Does anyone know what the strange pattern at the end of this closedown clip is? (Skip to 5:19)
Edit: Just noticed that the Testcard seems to not want to stay on screen before that pattern appears.
As James2001 notes the signal contains (luminance) pulse and bar signals, but it also contains two other signals - a 50% luminance pedestal with a burst of 100% chrominance sitting on it and also a 100% amplitude luminance pulse filled with chrominance which was an unusual signal to see in itself, it enabled an engineer to assess chrominance to luminance gain and delay differences. These parameters were important in analogue days, the last two particularly over long signal paths. I suppose that’s why the BBC may have transmitted it after closedown - to assist engineers to assess long signal paths from television centre to wherever.