PURPOSE: To reduce the assembly volume by switching a write/read memory to be in an active state when the power supply is normal, controlling a low resistance switch with a switching signal and connecting a buffer battery to an output terminal of a buffer adjusted through a 2nd switch and a series adjusting device.

CONSTITUTION: A write/read memory 8 is switched into an active state when the power supply is normal, and connected to a regulated power output terminal 12 and a low resistance switch 34 and a low resistance switch 34 is controlled by a switching signal. Furthermore, a buffer battery 20 is connected to a regulated buffer output terminal 16 via a 2nd switch 46 and a series regulator 48. Thus, the component cost is reduced and the assembly volume is reduced.