The Ring Alarm Contact Sensor V2 expands your Ring Alarm and adds an extra layer of security to your home. You can attach Alarm Contact Sensors to any door or window in your house or apartment, and when armed, you'll get instant alerts on your phone and tablet whenever they open. Easily installs in minutes without any tools or professional installation required. Simply place your Contact Sensor on any door or window frame and connect it to your Ring Alarm Base Station. Requires the Ring Alarm Base Station.