This circuit is from NASA documentation from the 1980s. The circuit shows how to obtain a stable optical coupler system. The circuit can be used as a shield.
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...