Based on 555 chip to form the timekeeping audio circuit

As shown, a multi-vibrator controlled by a timing signal is constructed with 555. The 4 pin of 555 is the forced reset terminal. When the voltage of this pin is lower than 0.4V, the circuit returns to the non-trigger state. By using the foot to be controlled by the external timing signal, it usually has a low potential. When the signal level higher than 1V comes, the circuit flips and sends a 400 Hz audio time signal. The 4 feet of the 555 can be connected to the timing output of the electronic clock through a 10KΩ resistor, or to the displacement point of the anti-theft and other sensing devices. When a sudden change occurs, the speaker will emit a rushing sound. The oscillation frequency can be changed by changing the parameters of R1, R2, and C1.