Found in a 1968 Novel Electronics Circuit, this circuit compares two light intensities using common LDRs as sensors. Transistors can be modern PNP equivalents.
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...