We found this circuit in the May 1990 issue of Radio Electronics magazine. The circuit is powered by the relay used and uses both normally open and normally closed sensors.
This circuit was found in a 1960s General Electric unijunction transistor manual. The circuit can...
In the figure we have the way to use an LM331 as a stable voltage-adjusted oscillator. The...
We found this circuit in a 1982 documentation. The circuit drives a relay when the sensors are...