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.
This circuit monitors extra-low frequency (ELF) fields. We found it in an American documentation from the...
We can use any type of resistive transducer with central resistance in the range of 10 k ohms to 1...
This circuit controls two lamps so that when one increases in brightness the other decreases. The...