Bob Eager wrote:

On Sat, 17 Dec 2005 19:32:34 UTC, Sawney Beane
wrote:

When he asked if my tape was steel, I caught on. I had read
somewhere about the signal voltage in rails. That made it worse
because now I couldn't honestly claim ignorance. If anything could
have made the situation more embarrassing, it was to realize I had
started explaining about my invisible friends, Click and Clack, who
had told me to do it.

Do that round here and you'll get more than embarrassed - more like
several hundred volts!

I've read that even where rails carry traction voltage, they can
still carry signal voltage. It has something to do with impedance,
but I haven't read how it works.