This circuit is from a 1969 Electronics World. It generates 100 kHz sinusoidal signals determined by the crystal. Capacitors must be ceramic.
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...