The eufy Security Entry Sensor is designed to monitor doors and windows, instantly detecting when they are opened or closed. It sends real-time alerts to your phone and can trigger a siren through the HomeBase for added protection. With a compact, easy-to-install design, it’s ideal for indoor use and runs on a battery that lasts up to 2 years. Requires a eufy Security HomeBase and supports optional 24/7 monitoring for enhanced home security. 2-year Battery Life: One battery provides 800 days of monitoring. For Doors And Windows: Compact and versatile design fits onto any door or window frame. Requires eufy Security HomeBase. 100-decibel Siren: Enable or disable siren protection, which triggers a 100-decibel siren on HomeBase, and sends an alert to your smartphone when forced entry is detected. Optional 24/7 Protection Service: New optional 24/7 professional monitoring service is now available for 24/7 emergency police, fire and medical response when your alarm system is triggered. What’s Included: Entry Sensor, CR123A Battery, Magnet, 3 x Mounting Screws, Owner’s Manual.