Glassbreak sensors, usually mounted on ceilings or walls, work by "listening" for the sound of breaking glass in a window. "Shock" glassbreak detectors are mounted on the window and "feel" the shock of breaking glass. This kind of advanced wireless technology can provide shatter and shock protection for your windows, for often intruders are "sensed" and an alarm sounded while they are still outdoors. This is often enough to send a burglar running!