This simple clock can be used to generate signals up to 100 kHz, depending on the crystal. We found it in a 1967 documentation. Note the high supply voltage.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...