PURPOSE: To reduce power consumption at a steady-state when no telephone set is in use by providing a switching contact between a main power supply and a load of a telephone set incorporating an electronic controller and turning on/off a power in response to the operating state.

CONSTITUTION: A switch circuit 18 is provided between the main power supply 17 and the load 22 of a telephone set incorporating an electronic controller. When an incoming signal is issued from a subscriber line by a digital transmission/reception circuit 1, a signal is sent to the circuit 18 via an I/O port 10 and the power supply 17 is turned on. When a handset is hooked off and a hook switch is turned off, a signal is sent to the circuit 18 to turn on the power supply 17. Even when the handset hooks on but a channel is formed, the power supply 17 is turned on. In other cases, that is, in the steady-state, the power supply 17 is turned off by the circuit 18 to reduce the power consumption.