This is the receiver for the previous circuit we found in the December 1992 Radio Electronics magazine. The sensor is a photodiode that must have optical features such as lenses.
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...