SONOFF DW2 Wi-Fi Wireless Door and Window Sensor with Phone Notification Home Security Motion Sensor Burglar Alarm System with App SONOFF DW2 Wi-Fi comes in two pieces, the transmitter fits onto the door or window and the magnetic switch attaches to the frame. It can help secure your door or window to let you know whether your home is safe wherever you are. The sensor will trigger an alarm to your smartphone to remind you of an intruder when the door or window is opened. Features: Keep linkage with smart devices to create various smart scene, turn on/off your light with an action. Notify you when the door/window is opened, and you can check the opening/closing status and history record of door/window on APP. No gateway required, BT low energy pairing. Allow sharing the sensor with your family to monitor and control of your home.  Real-time battery level display and low-battery reminder ensure you get clear know how long the sensor can run and when you need to replace batteries.  With simple peel and stick installation, it is easy to fit in door frames and window sills.   Note:  *DW2 doesn't come with batteries into package. *The sensor can work for up to 3 months if the door/window is opened or closed three times a day. *1. The device only works with 2.4GHz WiFi. 2. If the router is working in dual-band (2.4GHz & 5GHz), please upgrade the eWeLink app to V4.0.0 or higher. 3. The pairing will fail if a wrong WiFi password is input. 4. The device shall get close to the smart phone for a good transmission signal condition while pairing. Specifications: Model: DW2 Material: PC Battery Type: 2pcs AAA battery, 1.5V Working Voltage: DC 3V (2 * 1.5V battery) Quiescent Current: ≤ 40μA Emission Current: ≤15mA Wi-Fi: IEEE 802.11 b 2.4GHz Operating Systems: Android 4.1 or later, iOS 9.0 or later Installation Gap: <5mm Working Temerature: -10℃~40℃ Item Size: 7*3.1*1.9cm / 2.75*1.22*0.74in; 4.2*1.6*1.4cm / 1.65*0.62*0.55in Item Weight: 29g / 1.02oz Package Size: 7*4.8*2cm / 2.75*1.88*0.78in Package Weight: 37g / 1.3oz Packing List: 1 * Door Sensor 1 * Adhesive Tape 1 * User Manual