This flip-flop controlled by an LDR-type photocell was found in Radio Electroinics magazine from June 1959. Note that it can be powered from the mains and directly controls a sensitive relay.
The existence of field effect transistors at the input of the integrated circuit (operational...
This circuit using current components was found in an old documentation. It is a sequential circuit...
In the figure we have a signal detector using a tunnel diode. The circuit is from a Radio...