|Works on 12 volts AC (the ZW etc). Double pole, double throw. You can controle almost anything on a train layout. Controle Trains stoping and starting, Crossing gates, Block signals, Gateman, almost any items that changes color or turns on anf off, the relay can controle. The relay is activated by a train throught a simple insulated track, or a button, or a switch. 1 3/4,1 1/8, 3/4 INCH.