PURPOSE: To increase the number of subscriber circuits to be mounted by switching the feeding mode into the constant current feeding mode of a low current value so as to prevent the temperature raise in an enclosure.

CONSTITUTION: A constant resistor control circuit 210 and a constant current source 211 are selected by switching elements 212, 213 by an output of an n/m deciding circuit. The output current of a current sum circuit 214 controls an operational amplifier controlling the base current of a transistor of power supplying circuits 215, 216 suppling talking current to subscriber lines A, B. By such a constitution, the talking current supply circuit 21 supplies both the operating modes of the constant voltage constant resistor power supplying mode and the constant current supplying mode. Thus, the circuit can also cope with the increased number of subscriber circuits.