The power pak that comes in the starter set. I'm new at this and don't know anything, the locomotive runs fine but no sounds, but when the loco is disconnected from the tender I have idle sounds, but no activated sounds from the app or universal. The manual gives instructions how to make the horn work (press the button) but nothing happens.
Perhaps I am doing something wrong? I'd rather not send it back to Lionel, but I paid a bunch of money for it, so will if I have to.