Suggested by a 90s EDN, this circuit supports almost any LED as a source and a phototransistor as a detector. The circuit operates with a PLL 567 at a frequency of around 40 kHz.
This circuit can be used to activate the lamp when it gets dark. We found the circuit in old...
This simple circuit applies to any sensitive SCR. We found it in 1982 Maplin documentation. ...
This circuit is from an old documentation but still current for assembly. Just use BC548 instead...