Found in an old publication, this is a transmitter with a spark coil. The high frequency oscillations of the high voltage spark generate the signal thrown at the antenna.
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...