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.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...