TELEPHONE LINE CIRCUIT HAVING TIME-SHARED DTMF RECEIVERS

摘要

A TELEPHONE LINE CIRCUIT HAVING TIME-SHARED DTMF RECEIVERS The invention provides a circuit and method for the time-sharing of a DTMF tone receiver. A DTMF receiver has its input terminal connected to a common output terminal of a pair of transmission gates, each gate having an input terminal connected to a respective source of DTMF signals. A control circuit provides switching signals to the transmission gates to cause their input terminals to be connected alternately to the input terminal of the receiver at a predetermined rate until the receiver detects a tone signal on at least one of the input terminals of the gates. The control circuit includes means responsive to the initial tone detection for inhibiting the further generation of switching signals until the tone detection by the receiver has been completed.