> >> Anyone that thinks gold contacts do not corrode or get dirty
> >> should talk to telephone engineers in geothermal regions. I
> >> know the telephone exchange in Rotorua, NZ, went to extraordinary
> >> lengths to keep the sulphurous air out of the exchange back in
> >> the days of using relays. The area around Rotorua is very
> >> similar to Yellowstone Park in the USA.
> >
> >Presumably if you need a telephone exchange it means that
> >people live there, in this sulphurous atmosphere?
>
> Err, yeah, like a city full - which is minimum 20,000 in NZ, plus the
> surrounding environs. Constant rotten eggs smell, but nice hot pools.
>
>
We used to have to make special telephone cordage (curly cord etc.)
for Rotorua - using lead-free PVC. The standard lead based stabilisers
used to  make the cords go black after a very short time.

I think "mercury wetted"is different from a tilt switch. In the former
a mercury coating on the contacts is used as the contact material.
Presumably it stays there by either surface tension or by forming some
sort of alloy (or amalgum?).


RP

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