Xiaomi Door and Window Sensor 2

Is a compact, two-in-one smart sensor that detects both whether a window or door is open/closed and the ambient light level. It operates using Bluetooth Low Energy (BLE) and requires a Bluetooth gateway to function and connect with other smart devices.
Dual sensors: The device features both a magnetic induction sensor for open/closed detection and a light sensor for sensing ambient brightness. This allows for more advanced automation and smart scenes.
Smart automation: Through the Mi Home/Xiaomi Home app, you can create smart scenes to link the sensor with other Xiaomi products. For example, you can set it to automatically turn on a smart light when a door opens at night.
Notifications and event history: When connected to a Bluetooth gateway, you can receive instant alerts on your smartphone whenever a door or window is opened or closed unexpectedly. You can also view a history of all opening and closing events in the app.
Left open" alerts: The sensor can be configured to send an alert if a door or window has been left open for a specific period of time.
Wide application: Its small size and simple adhesive installation allow it to be used on many items besides doors and windows, such as drawers, pet gates, or refrigerators.
Simple installation: The sensor comes with adhesive stickers for a quick, tool-free setup. The two parts should be aligned with their indicator marks and placed on the fixed and movable surfaces of the door or window, with a gap of less than 18 mm when closed. 
Required gateway: While the sensor uses Bluetooth to communicate, it cannot send remote notifications or trigger smart scenes on its own. It must be paired with a device that has a built-in Bluetooth gateway, such as the Xiaomi Smart Home Hub 2.
Mobile app: The sensor is configured and managed through the Mi Home/Xiaomi Home app, available on Google Play and the Apple App Store.
Bluetooth connection: It uses the Bluetooth 5.1 BLE protocol.
Setup and usage tips-
Initial setup: Remove the insulating sheet from the battery before use. Download the Mi Home app, select the sensor from the device list, and follow the on-screen instructions.
Resetting the sensor: If needed, press and hold the reset button for 3 seconds until the indicator blinks to reset or confirm adding the device.
Troubleshooting: If you experience connectivity issues, ensure the sensor is close to a Bluetooth gateway and check for any firmware updates within the Mi Home app. 

Dimensions: 34.0 x 32.7 x 14.5 mm
Battery: CR2032 (included)
Operating temperature: -10°C to 50°C
Operating humidity: 0%“95% RH, non-condensing