Abstract: A communication system includes a transmission channel, a relay having first and second states, an operating power port, a first signal input port, a second signal input port and a signal output port. A power supply supplies power to the relay to place the relay alternately in the first and second states. The system further comprises first and second sources of program material to be selectively and alternately transmitted in the channel. The first and second sources of program material are characterized by at least one program material frequency. The first signal input port of the relay is coupled to the first source of program material. The signal output port of the relay is coupled to the transmission channel. A first inductance is provided for coupling the power supply to the operating power port. The relay includes a second inductance coupled across the power port for controlling the relay's state.