The Accton HWS6515-DW Door/Window Sensor consists of a magnet that attaches to a door or window and a 2.4 GHz IEEE 802.15.4 standard wireless. When the magnet is moved away from the transmitter, a signal is sent to the control touchscreen that sets off a security alarm or activates a chime or convenience lighting if the security system is unarmed.  This highly reliable wireless Door Window Sensor is very easy to install and operate in a wide range of residential environments. Besides,  the HWS6515-DW continually tests its batteries and notifies the control panel when they need to be changed.