WD-MT Skylink Wireless Window and Door Sensor for SkylinkNet Connected Home Security Alarm & Home Automation System and M-Series. Monitor your Door or Window open or closed status 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 HU-100 Internet Hub or M-1 Main Console/Indoor Siren) AAA Battery powered with Low Battery Detection. Compatible with SkylinkNet iOS Apple & Android App and M-Series. Lifetime Support: Toll Free 1-800-304-1187; Email: support@skylinkhome.com