A friend asked me to have a look at a Superswitch 2304 timer which stopped working when the bulb which it was switching blew, and replacing the bulb didn't fix it.
The answer, of course, was that when the bulb blew, so did an internal
3A fuse in the timer.But, having had a look at the thing, I don't understand how it works. It replaces a conventional wall switch and only has 2 connections - live and switched live. Yet the thing itself needs power to operate the display/logic/relay, etc. - and it doesn't have a neutral connection. My first thought was that maybe it gets a connection from an earthed backbox - but the holding screws go through insulated sleeves, and don't connect to the circuit board.
My next thought was that it could get a neutral connection through the bulb (it apparently only works with tungsten bulbs). But surely, that would only work when the light was off. Once it had switched the light on, the live and switched live would be at the same voltage and wouldn't be able to power it to do any further timing/displaying/switching.
Clearly, I must be missing something! Anybody know what?