PURPOSE: To save power for a communication terminal equipment by operating a network controller with station feeding without receiving commercial power supply at the incoming standby state and connecting the commercial power supply operating an input and output device after the incoming call is confirmed.

CONSTITUTION: A station power supply supplied from an exchange via an ISDN communication network is limited for one subscriber each and in the station feeding, the voltage is decreased to the operating voltage of each circuit of a network controller 10 with a DC-DC converter 3 from the primary side of a line transformer 11 and required current is supplied. A signal detection confirming circuit 1 of the network controller 10 outputs input/output device start information when an incoming call comes in the standby state and the signal is confirmed to be a signal to the input output device. Upon the receipt of the information, the relay drive circuit 2 drives a relay applying the connection/disconnection of the commercial power supply line in a relay box 12 to make the input/output device 20 into the operating state and the prescribed voltage current enough to operate the network controller 10 is supplied and the station feeding power is not consumed. Thus, the power of the communication terminal equipment is saved.