"Micky" wrote in message
...
And I think there are also mechanical switches where the space inside
the switch is filled with non-conductiive oil/liquid of some sort.
There is still a spark, but it's under the liquid. The surrounding
air doesn't get in.

**I see that mercury switches are sometimes used in ombs.

The home mercury switches was a selling point. They did not make any noise
when switched.

I doubt there are any mercury switches to be sold any more. The mercury has
been declared a big hazzard a number of years ago and if you look at it you
will die.