This circuit can generate signals in the VHF range and can be used as the basis for small transmitters. The frequency depends on the coil, which can have 2 to 8 turns for the range of 50 to 200 MHz.
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...