SONOFF DW2 Wi-Fi Wireless Door and Window Sensor Products are shipped according to the color or size of the main image on the product page. DW2 Wi-Fi is divided into two parts, the transmitter is mounted on the door and window, and the magnetic switch is mounted on the frame. It can help protect your doors and windows and let you know if your home is safe no matter where you are. When a door or window is opened, the sensor triggers an alert to your smartphone, alerting you to an intruder. Features: Maintain linkage with SONOFF smart devices, create various smart scenes, and turn lights on/off with actions. Notify you when doors and windows are opened, and you can check the open/close status and history of doors and windows on the APP. No gateway required, BT low power pairing. Allows sharing sensors with family members to monitor and control your home. Real-time battery level display and low-battery alerts ensure you know exactly how long the sensor can run and when the battery needs to be replaced. Installs easily in door frames and window sills with a simple peel and stick installation. NOTE: *SONOFF DW2 does not come with batteries. *The sensor can work up to 3 months if the door/window is opened or closed 3 times a day. *1. This device only works with 2.4GHz WiFi. 2. If the router works on dual-band (2.4GHz & 5GHz), please upgrade the eWelink APP to V4.0.0 or higher. 3. Entering the wrong WiFi password will cause pairing failure. 4. The device should be close to the smartphone when pairing to ensure good transmission signal conditions. Specifications: Brand: SONOFF Model: DW2 Material: PC Battery Type: 2 AAA Batteries, 1.5V Working Voltage: DC 3V (2 * 1.