TONE SIGNAL DETECTION CIRCUIT

摘要

PURPOSE:To detect a tone signal by low power consumption in accordance with a simple circuitry, regarding a tone signal detection circuit for detecting the tone signal constituted by the repeating of 2N times high level value and the subsequent 2N times low level value. CONSTITUTION:This circuit is provided with a counter circuit 1 counting a clock signal and an exclusive OR circuit 3 calculating the exclusive OR of 2N bit output of this counter circuit 1 and a binarized tone signal. By applying a constitution that the enable state of the counter circuit 1 is controlled and the setting of the initialization value of a count value is controlled in accordance with the output value of this exclusive OR, the detection result of a tone signal is outputted by the output mode of 2N<+1> bit output of the counter circuit 1.