This circuit triggers an alarm in the event of a power failure. The circuit is from an 80's documentation, being powered by 9 V battery. The parts are common today.
Found in a 1967 Electronics World, this circuit can use any modern equivalent FET. Observe the...
Found in American documentation from the 90's, this circuit applies to other operational...
This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4...