[Stooky Bill]

Techmoan on YouTube has got hold of an audio tape of BBC transmitter breakdown announcements and music from the 1960s:

www.youtube.com 

(not sure I entirely agree with the explanations by 'Ringway Manchester' - I'd have thought the first side would be played if the transmitter lost its link from the studio centre; and the second for relays if they lost reception from the main transmitter - but this isn't quite my area of expertise)

Yes, his explanations are a bit out. I'm pretty sure it's nothing to do with silence detection, the old big transmitter sites (they think this is from Sutton Coldfield) were manned and the engineers had things like slide scanners, record decks and in the case of SC, a telecine. 

Possibly that tape was a copy or a master and they'd have the announcements and music in more accessible forms to play on air.

His explanation of 'reduced power' is partially correct, standby transmitters and reserve aerials would mean reduced power levels. However the TV transmitters at the big sites were two seperate units combined into one output (well actually they'd be 4 transmitters - 2 video and 2 audio). The nominal power was achieved by having both working. If one was off, (either intentionally or not) then that was reduced power. 

You'll have seen this mentioned in the IBA Engineering Announcements programmes.... When they said there was going to be Reduced Power, that normally meant they were working on one of the transmitters for that channel. 

Nothing to do with relays, not that there were that many in the 405 line VHF days. They are just rebroadcasting what the main station is putting out, there wasn't a way to put out an apology on one