PURPOSE: To reduce extermely power consumption at a regulated power supplying circuit, by operating the regulated power supplying circuit or increasing its capacity, only when necessary.

CONSTITUTION: In case of a stationary state that transmission and reception of information are not executed, an output in an output end A of a circuit block 4 is in a high level, an output of the second regulated power supplying circuit 5 is in a low level, and a transistor Q6 is turned off, therefore, a current flowing to Q2 is decided by a resistance R4, and a comparatively small value is offered. On the other hand, the second regulated power supplying circuit 5 operates, a necessary output appears in its output end, and when transmission and reception of information are executed, the transistor Q6 is turned on by an output of the second regulated power supplying circuit 5, and a current flowing to the emitter of the transistor Q2 increases remarkably at this time only.