A security system device that detects the sound frequency made by breaking glass. A glassbreak detector houses a highly sensitive microphone that can detect the exact frequency of broken glass. GDBs, along with motion detectors, are devices used for interior monitoring to provide another layer of protection beyond exterior monitoring. One GBD can usually protect every window in a room and should be mounted on the wall across from the windows it is meant to protect. GBDs are preferable over motion detectors when large animals live in the alarms premise, since they work while the security system is in stay mode without causing false alarms.