We found this circuit in a Philips documentation from 1965. The circuit uses a common LDR sensor and the transistors are general purpose types. TR2 can be a BD135.
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...