The Qolsys IQ glassbreak QS-1410-840 is specially designed to protect windows. Triggered by the pitch and frequency of breaking glass, they are effective within 25' of the windows. Make sure to mount the sensor at least 3.3 feet from desired protected window, and in line of sight (avoiding corners and doors blocking the sensor). They are typically mounted on the opposite wall or above windows on the ceiling.The IQ glass adds an extra level of perimeter defense to your door and window sensors. Featuring pattern-recognition technology for superior detection and false alarm immunity, protects all glass types up to 1/4". The QS-1410-840 easily mounts to walls/ceilings and operates when system is place in "Stay" or "Away" mode. The IQ glass is not guaranteed to "hear" through walls or thick curtains.