Patent ID: 7770847

Claim:
An add-on controller for feature control of a remote object in a model railroad layout having an AC transformer connectable to a track, the add-on controller comprising: a first input connectable to the AC transformer to receive an adjustable AC track power signal; a second input connectable to the AC transformer to receive a fixed AC accessory voltage signal; a pass device coupled to the second input for controllably phase modulating the AC accessory voltage signal to form an altered AC accessory voltage signal; a relay arranged for connection to a model railroad track, the relay coupled to the first input to receive the adjustable AC track power signal, and coupled to an output terminal of the pass device to receive the altered AC accessory voltage signal; and a microprocessor, the microprocessor having a first output arranged for controlling the pass device for controllably phase modulating the AC accessory voltage signal to encode digital command data, and the microprocessor having a second output for controlling the relay for switching between the AC track power signal and the altered AC accessory voltage signal.