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.
We found this circuit in a Popular Electronics from the 80s. The circuit is based on the LM3909, a low...
In the figure we have the basic configuration of an operational amplifier for AC signals using the...
This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is...