4 wires, I did put power to the terminals, and the two outside ones powered the trucks. That was a couple of days ago, I believe they were the Brown and Green ones, if I remember correctly. I will be running RailPro battery power, I could have just looked into my other LGB Diesels which are all running RailPro and battery power, but I would have to remove the body shells to see inside. Thanks, I will wait for your answer, trainman