The opening of the sensor in this circuit of the 70's causes an integrated buzzer of the Sonalert type to fire. The circuit can be used with power buzzers powered by 6 or 12 V, depending on the power supply.

The opening of the sensor in this circuit of the 70's causes an integrated buzzer of the Sonalert type to fire. The circuit can be used with power buzzers powered by 6 or 12 V, depending on the power supply.