PURPOSE: To precisely prevent a trouble outputting "on" and "off" signals simultaneously and also to prevent the generation of unrequired operation at the time of turning on a power supply, by taking out outputs of both one-shot circuits for "on" and "off" regarding the inverted outputs of opposed one-shot circuits respectively as the gate signals.

CONSTITUTION: When a power supply is turned on, Q outputs of both the one- shot circuits 1, 2 are the "H" level in the initial state. Therefore, required "on" and "off" signals are obtained regarding the Q outputs of respective opposed one-shot circuits 2, 1 as the gate signals through AND gates 3, 4. When one of "on" and "off" signals is in operating, the Q output of the operating one- shot circuit 1 or 2 is "L" without fail, so that the output operation of the other "on" or "off" signal can be inhibited and malfunction outputting the "on" and "off" signals simultaneously can be prevented.