First, the sensor detects the vibrations of the glass and listens for the right frequency for breaking glass. It sends trigger signal to the main brain of the car alarm when the glass is broken or hit by a hammer.
3 .Acoustic detectors work by hearing the noise of breaking glass. You may be thinking does the sensor pick up other sounds as well? The answer is no, acoustic sensors only are tuned to pick up the sound of breaking glass. The main advantage of these sensors is the ability to protect your car by using only one detector a trigger signal to any connected any car alarm system. with negative trigger Wiring
RED : +12V or alarm's positive armed output
Black: connect to ground
Blue : connect to instant trigger Aux-input of alarm