Since we don't have a garden railroad category here, I will impose upon the main forum:
I picked up a Lionel large-scale GP-20 UP diesel this weekend at our Cal Stewart weekend extravaganza, but I didn't get the extra controller box that activates the horn and bell. What is the technology behind this box? In looking at the instructions to install a choke/inductor between the power source and the track, my first guess is that the box (which houses a 9V battery) might transmit some kind of tones down the track to be received and sensed by the locomotive's sound activation circuit.
