A system and method for carrying a downstream optical signal and an upstream optical signal on a fiber optic link is disclosed. The system and method includes a first transceiver unit that receives an input communication signal from at least one external communication device at an electrical input port, a transmitter that converts the input communication signal into an optical signal and transmits the optical signal as an downstream optical signal on a fiber optic link, a receiver at the second transceiver unit that receives the downstream optical signal and converts the downstream optical signal into an electrical communication signal, and a first circuit in the second transceiver unit that determines whether the second transceiver couples the electrical communication signal to a two wire intercom circuit or a four wire intercom circuit.