In the figure we have a simple way to produce tone in a piezoelectric transducer. The frequency depends on the capacitors and the supply can be done with voltages from 1.5 to 6 V.
This circuit was found in an old documentation from 1968. The voltage gain is 70 and the...
This circuit was found in a 1980s documentation. The IC is the 7400 and should be powered with 5...
This practical idea from a 1992 documentation shows how to count the turns of a winder using a...