On this side of the pond, we call "flares", fusees.Oh, that isn't what I was envisioning. Thanks. I was, now incorrectly, thinking that it was something we would call a flare.By way of further explanation for our guest, small explosive charge is exactly what they are. Put them on the rail, and if a train runs over it, it goes off. Makes a big bang and tells the engineer "Hey, something's probably wrong here!".
http://en.wikipedia.org/wiki/Detonator_(railway)
To me, a detonator would be something that would blow up the rail, severing it into pieces.
http://en.wikipedia.org/wiki/C-4_(explosive)
jb