Electronic circuit for eliminating chatter

An electronic circuit for insuring the application of a contact signal comprising in combination contact means for producing a contact signal representative of a change of state;

• a first periodic pulse signal having a leading edge;
• asynchronous logic means for receiving as a first input said contact signal and as a second input said first periodic pulse signal, and in response to a coincidence in the changed state of said contact signal and said first periodic pulse signal producing at least one write-in pulse;
• a second periodic pulse signal having a leading edge and being synchronized with respect to said first periodic pulse signal so that said leading edge of said first periodic signal defining said coincidence detection precedes a leading edge of said second pulse signal;
• and synchronous logic means for receiving as a first input said write-in pulses produced by said asynchronous logic means and as a second input said second periodic pulse signal, and in response to each said write-in pulse and leading edge of said second periodic pulse signal, producing an output signal representative of the changed state of said contact signal, and including a third periodic pulse signal, input timing means disposed intermediate said switching means and said asynchronous logic means for periodically applying said contact signal as said first input to said asynchronous logic means, said third periodic pulse signal being synchronized with respect to said first and second periodic pulse signals so that the portion of said third periodic pulse signal applying said contact signal to said asynchronous logic means is coincident with a portion of said first periodic pulse signal during which a write-in pulse may be produced, and output logic means adapted to receive as a first input said write-in pulses and as a second input the output signal produced by the synchronous logic means, and in response thereto to produce an output signal having a pulse width defined by the leading edge of said write-in pulse and leading edge of said second periodic pulse signal.