Brass buttons on AF locos

[ben10ben]

I was discussing this with my local shop owner not too long ago in response to a piece he had picked up somewhere. I had always wondered this as well.

Anyway, it seems that the brass buttons serve to activate these

track trips. They attach to the track in some way that we couldn't figure out. When the engine rolls over the trip, the buttons press the copper tab that would be in the middle of the rail, and activate whatever accesory they're attached to(in this case most likely a switch).

[Sturgeon-Phish]

On some of my older post war American Flyer steam locos, there are two small brass spring loaded buttons in the center of the chassis between the drivers and I don't know what they are for. Are they a carryover from the the three rail units?
Thanks
Jim