The invention relates to a building visible intercommunication system, wherein the central manager, the door manager, the floor distributor and the indoor machine all have modulate interface circuits; the controllers are connected by three-core wires; said wire comprises two-corn bus L_BUS and one-core video wire; the modulate interface circuit processes DTMF code on the communication data sent between units, to modulate the code signal and voice signal to the power source, to be superposed on the system core bus L_BUS, and demodulate the received information from the system core bus L_BUS to drive relative unit. The invention can reduce three wires than present one, with simple operation. |