crossing signals and gates

[gandy dancer#1]

HI; been looking at these here and other places. Would somebody explain to me how they function?? What activates them as train approaches ?? Infrared beam, photo cell, magnetic reed switch by track?? Curiosity has got this cat

[Doneldon]

gd#1-

All of the above and then some. It depends on what signals and other controls are installed on the layout. The most common, and affordable, crossing gates have a pressure plate under the track so the weight of the train lowers the gates. The animation is cool but the gates are down only while the train is on the crossing, not before or for a time after the train passes as is the case with the prototype.
                                                                                                                       -- D