Abstract: The opening and closure of the contacts of a push-button actuated switch duces across impedance means a voltage which is stably high and low when such contacts are maintained closed and open, respectively. Bouncing of the contacts after their initial closures and openings produces superposition on the stable levels of such voltage of trains of impulses caused by such bouncing. A bistable semiconductor flip-flop is coupled to the impedance means to sense such voltage and to assume a "high" state and a "low" state only when the stable level of such voltage is, respectively, high and low and, further, the flip-flop receives a clock signal. A retriggerable semiconductor monostable multivibrator is coupled to such impedance means to be triggered by such impulses from its stable "off" state to its unstable "on" state which is repetitively renewed by repetitive retriggering of the multivibrator.