In article MzWsf.11569$X86.8911@trnddc04,
James Sweet wrote:
This can't be done unless you have a neutral at the switch position.
When the switch is on there is no potential difference between the
terminals therefore no power source.

There's almost always a neutral in the switch box, occasionally I see an
arrangement with power coming into the light box and a separate switch
drop but it's fairly rare.

Right. In the UK the latter is the norm. Lighting circuits are radials and
the feed goes from one ceiling lamp to another, with the switch drop from
that lamp. Of course if you have floor outlets for table lamps etc you're
more likely to find a neutral at the switch.

Also it'd be possible to power the reminder with a battery in that
case, it wouldn't have to draw much power. If the lamp is incandescent
you could even use a rechargeable battery or memory backup capacitor to
power it and "steal" power to charge the battery when the switch is off.

Yup - although it might be tight to fit all that within the switch back
box. In the UK, some are so shallow there's just enough room for the cable.

--
Is the hardness of the butter proportional to the softness of the bread?*

Dave Plowman London SW
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