The ZN416E integrated circuit is uncommon today. It consists of a complete radio, like the one found in a 90s Popular Electronics. The power is from a single battery.
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...