TIMECAST SIGNAL DETECTION CIRCUIT

摘要

PURPOSE:To enable accurate time correction, by obtaining a right timecast when a forecast signal is detected by a set frequency while a regular time signal is detected. CONSTITUTION:A timer 16 is triggered by a timer trigger signal Sg as outputted at a timecast output terminal 11 of a time piece body 10 to output an operation command signal Si. Switching circuits 17 and 18 are turned ON separately on the signal Si and a source power +B is supplied to an acoustic signal detection circuit 20 and a time tone signal detection circuit 30. An environment sound Sa caught with a microphone 21 is amplified 22 with the circuit 20 and inputted into the circuit 30 through an acoustic signal line 23. Forecast signals are detected 24 from among signals transmitted through the line 23 and the frequency of detecting the forecast signals is counted 26 to output a signal 'H' when the counts are two or three. A regular time tone is detected 25 from among the signals from the line 23 and the signal 'H' is outputted. An AND circuit 28 outputs a reset signal Sr when outputs of the counter 26 and the circuit 25 are both 'H' and the signal is inputted into a second reset terminal 13 of the body 10 to correct time.