This simple sensitive circuit was suggested in a July 1992 Radio Electronics issue. The relay is a double-contact changeover relay. Sensitivity adjustment is made at R2.
Found in an Elektor from the 90s, this circuit is based on components that are still common today....
This circuit was found in a Signetics documentation from the 1980s. Next to the figure are the...
This timer of 10, 25, 45 seconds and 5 minutes has its times selected by the keys. The circuit drives...