The Skylink WD-MT Wireless Window & Door Sensor simply mounts to any window or door 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 window / door sensor can also monitor internal doors that require protection like cabinets and safes. The Window & Door sensor is operated by a single AAA Alkaline Battery (Sold Separately). Compatible with SkylinkNet Connected Home Security Alarm & Home Automation Systems and M-Series.