This circuit that generates signals between 1.5 and 2 kHz was found in a documentation from the 90's. The capacitor C1 can be changed to obtain other frequencies.
In the figure we have the way to implement a 5 to 45 V zener diode with 50 mA of maximum current...
We found this circuit in a Radio Shack documentation from 1977. The circuit serves for a link of...
This circuit was found in the 1977 National Semiconductor FET Databook. The FET can be the BF245...