On YouTube I did a serach for NYC railroad films. One of those films (1950's New York Central Railroad - The Big Train) described the ongoing research done by the New York Central back in the
50's:
My guess is that it will be a glass tube containing tritium, which is an alpha source, with a phosphor on the inside. These were used in telephone dials in the UK in the 1960's.
I mean a beta source, of course. That's what comes of typing with the new puppy sitting in my lap....
Not Radium?
If it were Radium, it would last a lot longer than 7 years. Tritium has a half-life of 12.3 years. A wild-ass guess would be a reduction of intensity of about 30 percent at 7 years. I'd say that would be the replacement point for railroad service.
do an internet search for "Traser watch" - I have one, 1/2 life about a decade - and very handy
I had a TI LCD watch with Tritium in the liquid. Didn't use a battery to light it up!
Battery was to darken the segments only.
It worked great - alpha particles - the half life got the watch - dimmer and dimmer. Finally the LCD would work but only in the sun. And then it was tricky!
Mart> newshound wrote:
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