This circuit was found in an American documentation from the 90's. It switches a continuous voltage obtaining an AC voltage at the output of approximately 1 kHz.
This circuit using components that are still common in our market was found in a 1987...
The varactor or varicap diode tunes the signal for listening to SSB signals on a common receiver. The...
This circuit that also serves to control LEDs and other loads is from a 1960 publication. The...