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Le 15 Jan 97 @ 4:05, George Irvine =E9criv=EEt sur "Re: aluminum lights":
> Bill, using the housing of a light to conduct in water is out of
> the question
It's a totally unrelated field, but it may give a good reason to do
so.
It used to be the tradition for subways to use the steel rails the
train is running on to carry the return (negative) power current
supplied by the notorious Wthird rail". This is analogous to using
the light case to carry current.
However, it was found that this induced stray currents that corroded
metal installation near the subway lines, or worse, affected signal
circuits.
Subways use "low" (600-800 volts) DC voltages, so this means high
currents. By contrast, high-speed mainline trains use high
(11,000-50,000) AC voltages, with much lower amps and less trouble in
that respect.
So, nowadays, many modern subway systems have negative rails
insulated to avoid those destructive stray currents.
--------------- Pour la Republique Francaise du Quebec -------------------
In the French version of "2001: A Space Odyssey",
the last word uttered by HAL is "GOD"...
~~~~~~ last dive: The almost fully frozen canal Soulanges, 5mfw ~~~~~~~~
Marc Dufour - [\] ACUC6 31874 - TDI CD-0197 - http://www.accent.net/emdx-=
---------
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