We found this circuit in the 1983 Radio Electronics Special projects magazine. The components are common, and the circuit drives a relay. The power supply must be isolated.
This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made...
This circuit was found in a 1967 Electronics World. We can design it with a BF245 for the FET and a...
Using a CA3030, this circuit was found in the May 1988 Radio Electronics magazine. The power...