Door Sensors & Window Sensors are additional modules suitable for installing into both commercial and residential security alarm systems. Their simple functionality typically features two contacts, one mounted on the frame of the door or window with the second mounted to the door or windows itself. When the door or window is closed, the contacts are aligned closing their signal loop. When a door or window is opened while the alarm system is active, the signal loop is broken thus triggering the alarm system.

This type of sensor can be installed in alarm systems as well as in monitoring systems such as within the retail industry, to signal when customers enter and leave a shop. A similar use for these sensors can be found in systems where knowing all doors and windows within a system are closed.