This circuit was found in the September 1971 Radio Electronics magazine. The buzzer can be replaced by a relay according to the supply voltage. R1 adjusts the sensitivity.
We found this circuit in the April 1975 Radio Electronics magazine. The circuit has a latch and...
We found this sophisticated home alarm in a 1994 documentation. The circuit supports sensors of...
This circuit was found in the 1991 Electronics Experimenter's Handbook. It activates a relay when...