| 摘要 |
PURPOSE:To simplify constitution and to facilitate IC-implementation by constituting a circuit which mixes cosine wave signals by using circuits which have high input impedance and low input impedance and a circuit which mixes their outputs. CONSTITUTION:A reference frequency signal from a reference oscillation circuit 11 is frequency-divided by a high group frequency dividing circuit 13 and a low group frequency dividing circuit 14 into two kinds of rated frequency, and a high group cosine wave generating circuit 16 and a low group cosine wave generating circuit 17 generate cosine wave signals. Those cosine wave signals are mixed by an output synthesizing circuit 18 to generate a DTMF (dual tone multiple frequency) signal, which is sent out to a telephone circuit. The output synthesizing circuit 18 consists of the 1st and the 2nd circuits which receive input signals and have the high input impedance and low output impedance and the 3rd circuit which mixes the outputs of those 1st and the 2nd circuits. |
