CIRCUIT FOR DETECTING OBJECT SIGNAL FROM INPUT SIGNAL.

摘要

An input analog signal having periodicity is converted to a 1-bit digital signal by an A/D convertor (42) and is then converted to a parallel signal by a serial-parallel convertor (43). Correlation between the parallel signal and a reference signal train is calculated by a correlation device (45). When this correlationship is obtained, it is held by a hold circuit (48) and a tone signal detection result is outputted. In this way, the tone signal is detected by a simple circuit construction having low power consumption.