This circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit is based on a 741 that activates a buzzer with oscillator. R5 adjusts the sensitivity.
This is a conventional alarm that uses NO and NC type sensors for doors and windows. The circuit is...
This circuit shows how to control a TTL logic gate with a phototransistor. The phototransistor supports an...
The circuit is suggested by Motorola in its 1990 Linear Databook but operating from the same...