Yah, Grundy's got it right, at least in regards to what they're used for, dunno about the exact hardware specifications. Harrison says that starting guns that emit sound and light are used more now in swimming, though.
And I could swear I've heard air horns being used for starting races before, though Harrison swears I'm nuts.

Well, fine sneak posts and edits in there on me and make me look dumb, not that I need any help with that!

Peace & Luv, Liz