We found this circuit in a French documentation from the 80's. The components used are still common and the circuit can generate signals from 10 Hz to 100 kHz.
PIC16F15386 Family with CIPs Uses MPLAB® Code Configurator for Quick Development The PIC16F15386...
This circuit was found in the magazine of radio amateurs 73 in a 90's edition. The components are...
This configuration was found in a 1988 documentation. It is a touch lift drive system. The circuit...