PURPOSE: To switch a transmitting and a receiving function without touching any equipment by providing a human body detecting circuit and a sound volume detecting circuit on the front surface of a transmitting and receiving speaker.

CONSTITUTION: A transmission/reception switching circuit 2 perform switching to the side of a transmitting circuit 3 when both of the human body detecting circuit 6 which consists of an infrared sensor, etc., and the sound volume detecting circuit 7 which operates when a predetermined set value is exceeded operate. Once this switching is performed, the circuit 2 is changed over to the side of a receiving circuit 4 when a human body leaves the circuit. Conse quently, this interphone is used without touching any equipment with a wet hand when used in a bathroom.