It is a simple 2-piece design. One piece goes on the door or window itself and one piece goes on the frame. When one moves, it trips the alarm.
The home base unit supports multiple detection zones. The window & door sensor is ideal for a perimeter zone. If you are home, then you only arm the perimeter. That way, the alarm would trip if a window or door opens, but you are still free to move about your home.
The sensor is powered by one 9-volt battery.
This window/door sensor is 100% wireless. This means that there are no wires to run and installation is trouble-free.
You may use an unlimited number of any combination of add-ons. However, the base unit (SSC-ALM1) is REQUIRED for any of the add-ons to function.