On Mon, Jul 26, 1999 at 12:25:49PM -0700, Mark Willis wrote:

> On the second point, obviously you could put a series resistor in line
> with the bulbs, swap bulbs to give you 6V bulbs, and monitor the top of

If you use a very small series resistor and an op-amp you wouldn't need
to change bulbs, but there is another way I have seen used that
minimizes the voltage drop - use a reed switch inside a coil. You
then sense the applied voltage, and if the reed switch doesn't close
when the volts are applied, bingo!

You'd have to experiment with coils for different size lamps.

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