This circuit emits a sound when a magnetic field, of a magnet, for example, approaches the sensor. Frequency depends on C2 and power can be made with voltages from 5 to 15 V. We find the circuit in a 1993 American publication.
This circuit emits a sound when a magnetic field, of a magnet, for example, approaches the sensor. Frequency depends on C2 and power can be made with voltages from 5 to 15 V. We find the circuit in a 1993 American publication.