This circuit was obtained from a Radio Electronics from the 90's. The circuit limits the strength of an audio signal preventing saturation. Equivalent operational amplifiers can be tried.
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...