This circuit was found in a Popular Electronics from the 90s. Its purpose is to disable the output of an FM or VHF receiver between stations, preventing the reproduction of hiss.
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...