Expand your Ring Alarm system to secure each door & window in your home, & get alerts as soon as they open Make sure the doors & windows are shut The Alarm Contact Sensor connects to your Alarm Base Station & easily mounts to any door or window frame in your home. Choose to get audio or mobile notifications whenever your doors or windows open, so youll always be the first to know when somethings ajar. Requires the Ring Alarm Base Station Triggers your Alarm if someone tampers with Contact Sensors & system is armed in Away or Home Mode.