Found in a Philips' 1968 documentation, this circuit is slightly different from the previous one. The components are also from the era, and modern equivalents can be used.
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...