PURPOSE: To enable output when a power supply is turned on to be stable by tentatively reducing + side input voltage of a reference voltage input of a comparator as compared with - side voltage of a battery voltage input of a guarantee circuit.

CONSTITUTION: A guarantee circuit 20 is provided in this circuit. A battery voltage Vcc which is fed to a terminal 30 is divided by resistors R1 and R2 and is fed to - side terminal 10a of a comparator 10 and at the same time charge current flows to a capacitor C tentatively, thus enabling a transistor Tr to be turned on. Thus, + side terminal 10b of the comparator 10 is ground through a collector and an emitter of the transistor Tr, thus enabling voltage at the terminal 10b to be at a lower grounding potential then voltage at the terminal 10a and L to be output to an output terminal 40. Thus, even if the voltage Vcc which is applied to the terminal 30 is at the middle point of operation level of hysteresis characteristics of a circuit, output of the comparator 10 is always set to L when the power supply is turned on, a device can be operated, and a battery can be used without any waste.