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.
Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the...
This circuit was found in the November 1992 issue of Radio Electronics magazine. The circuit has...
This circuit was found in an American documentation from 1977. The circuit can be implemented with modern...