Pro Series Panel. Most door and window sensors work through the use of a magnet, which is already equipped with the sensor. The magnet is placed on the moving portion of the door or window, and the sensor is placed on the door or window frame. Opening the door or window will cause the magnet to become separated from the sensor, which will release its internal reed switch. The sensor will then know to send an alert to the alarm panel and provide awareness, safety, and protection to your home.