This circuit was obtained in an Electronics Now from the 90s. The circuit uses operational amplifiers from the time and the indicator is of the Sonalert type with internal oscillator.
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...