PURPOSE: To prevent an output from becoming indefinite, even if a signal is inputted simultaneously to a set input terminal and a reset input terminal of a flip-flop by simplifying the circuit configuration.

CONSTITUTION: In input parts of an S terminal and an R terminal of an SR type flip-flop, D-type flip-flops 4 and 4 for detecting a rise edge of an input pulse and outputting an impulse-like pulse are constituted. In such a way, since set and reset of the flip-flop 5 are operated by an edge trigger, even if a state that the S terminal and the R terminal become an 'H' input simultaneously exists, it does not occur that an output becomes indefinite.