TELECOM Digest OnLine - Sorted: Re: 208/240V, was: 25 Hz Power

Re: 208/240V, was: 25 Hz Power

Garrett Wollman (
Tue, 14 Mar 2006 06:34:49 UTC

In article <>, PAT wrote:

> [TELECOM Digest Editor's Note: Precisely! But a 25-watt bulb at
> 240 volts in a 120 volt fixture still presents a reasonably decent
> glow to point people in the direction they should walk to reach a
> fire escape, for example, which is I think how he was doing it. PAT]

If that were the goal, then it would make more sense to use a nuclear
exit sign. The signs are illuminated by small capsules of tritium gas
(a radioisotope of hydrogen manufactured in nuclear reactors) which
are coated on the inside with a phosphor. The tritium decays by
ejecting beta particles, which bang into the phosphor, causing it to
glow. The signs have a service life of about ten years. (The
half-life of the tritium that powers them is about twelve.)

Garrett A. Wollman | As the Constitution endures, persons in every | generation can invoke its principles in their own
Opinions not those | search for greater freedom.
of MIT or CSAIL. | - A. Kennedy, Lawrence v. Texas, 539 U.S. 558 (2003)

[TELECOM Digest Editor's Note: But was that type of exit sign (using
tritium gas) generally avaialable in the middle 1970's, which is when
I recall seeing the building janitor using his technique and
discussing it? There are also exit signs illuminated with tiny
little flourescent tubes are there not? I think those are sort of new,
within the last 15-20 years. PAT]

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