We found this circuit in an American documentation from 1975. The list of transistors that can be used is attached to the diagram. Modern types can be experienced.
In this circuit the capacitor under test is charged at switch position A and then discharged...
This is a common circuit in the 1990s, when experimental FM transmitters were in vogue. The...
Using a piezoelectric sensor of the time, this circuit was found in the February 1994 issue of...