19-05-2024, 10:09 PM
When the ITV transmitters came on air, it wasn't the ITV companies broadcasting anyway, as the test cards were generated at either the transmitter, or later, the ROC, the signal only switching to the ITV companies (or TV-am post-83) themselves later, so whatever the process to fire up the transmitters was, it would have been triggered by the ITA/IBA themselves at the transmitters and ROCs rather than from the ITV companies.
Unlike the BBC where it was triggered by a piece of equipment at TV Centre being unplugged and plugged back in.
Not sure about Channel 4... but I think in the early days at least, that also came on air with the locally generated ETP-1 before switching to Charlotte Street's a bit later (the lines above and below the IBA:CH4 being an indication of where it was coming from). I've seen later videos from 1991/92 where the transmitters open up to 4-tel, so clearly linked to Charlotte Street right from power up, though whether anything was actually done there to turn on the transmitters, or the transmitters were triggered to turn by a timer or similar, I can't say (and post-93 they were just left on all night anyway).
Unlike the BBC where it was triggered by a piece of equipment at TV Centre being unplugged and plugged back in.
Not sure about Channel 4... but I think in the early days at least, that also came on air with the locally generated ETP-1 before switching to Charlotte Street's a bit later (the lines above and below the IBA:CH4 being an indication of where it was coming from). I've seen later videos from 1991/92 where the transmitters open up to 4-tel, so clearly linked to Charlotte Street right from power up, though whether anything was actually done there to turn on the transmitters, or the transmitters were triggered to turn by a timer or similar, I can't say (and post-93 they were just left on all night anyway).