We found this circuit in a 1967’s Electronics World. The circuit can be made with modern equivalent transistors. The selection is made by the tuned coil.
This circuit detects light variations using two LDRs as sensors. Operational amplifiers and...
The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406...
This circuit was found in Mullard's 1960s transistor manual. The circuit uses germanium...