The Skylink WD-MT Wireless Door & Window Sensor for SkylinkNet Home Security System and M-Series can be mounted to any door or window frame with double-sided tape to track / monitor the status of open or closed. When the status changes, an instant push notification is sent to your smartphone or mobile device to inform you of the status change. The door / window sensor can also monitor internal doors that require protection like cabinets and safes. The Door & Window sensor is operated by a single AAA Alkaline Battery (Sold Separately). Get an Instant Alert of a Door or Window Opening on Your Property Wireless range up to 600 feet in open area (Sensor range to Hub) AAA Battery powered with Low Battery Detection Compatible with SkylinkNet and M-Series System. DOES NOT WORK BY ITSELF a Skylinknet kit (SK-150, SK-200, SK250 -sold separately) or an Indoor Siren (M-1 -sold separately) is require to work Skylink WD-MT - Door and Window Security Sensor for SkylinkNet - Alarms