In article ,
"Bob Eager" writes:

Weren't those (railway anyway) an odd voltage anyway?

I think so...but I heard that the problem was that the people who stole
them didn't know that....so they stole them (once) anyway...

They used to be used to distinguish mercury vapour lamps
which needed external ballast from self-ballasted ones, in
streetlamps, to avoid unfortunate accidents.

--
Andrew Gabriel