The DSC PG9303 Wireless PowerG Door and Window Contact monitors doors and windows for activity. This device offers the excellent range and reliability of a PowerG Sensor, and end users will appreciate the discreet, thin profile. It is very easy for DIY users to install and maintain. As a surface-mounted door and window contact, the PG9303 follows a rather simple operation. The device consists of a sensor and a magnet. The sensor is placed on the door or window frame, and the magnet is placed on the actual door or window. For best results the magnet should be in direct contact with the sensor when the door or window is closed. A spacing gap of larger than half an inch may prevent proper operation.