This modulator circuit for low intensity signals is from old documentation. The integrated circuit used is uncommon today. The circuit operates with signals up to 2MHz.
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...