This circuit with germanium transistors was found in a publication by Gernsback from 1960. The circuit is low power, a few tens of milliwatts.
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...