David B. Kimball
Engineering in Shreveport, LA

4713564, Dec 15, 1987

Dec 19, 1985

6/810958

David B. Kimball - Shreveport LA
Ruloff F. Kip - Westchester NY

American Telephone and Telegraph Company, AT&T Information Systems - Holmdel NJ
AT&T Bell Laboratories - Murray Hill NJ

H03K 1756, H03K 501

3075421

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. The multivibrator produces such clock signal only when it reverts to "off" state following the last of the impulses in each train thereof. The impedance means may be a simple resistor or, alternatively, a pulse generating circuit productive of a trigger for the multivibrator in response to either a positive-going or a negative-going fast change in voltage produced by such impulses.