This high sensitivity circuit was found in the July 1992 Radio Electronics magazine. The circuit drives a buzzer, but a relay can be used to activate an external load.
This circuit from Delta Products was published in the May 1974 Radio Electronics magazine. The...
This circuit that uses only transistors that are still common was found in a 1995 documentation. The TIP41...
This new Texas Instruments component consists of an inductive proximity detector that can be used...