In article ,
wrote:
On 13 Mar,
Frank Erskine wrote:

Automatic light switches with an ORP12, a red spot transistor and a
relay.

And what about before semiconductors? Replace the red spot with a triode.
Neon for the timer.

An electro-mechanical switch would make more sense in valve days.

--
*Remember: First you pillage, then you burn.

Dave Plowman London SW
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