1. Real-time door status monitoring 2. Unlock record tracking 3. Automatic lock support (AVAILABLE When lock has autlock function only) Power supply:CR2032 battery(not included) Working voltage:3V Standby current:Less than 5uA Detective distance:Less than 22mm Compatible deavices:All ttlock smart devices which support add door sensor in the setting option. Note:that door sensor cannot be used itself independently. It's used with compatible for TTLOCK DEVICES. Colour:White Material:ABS Size:41x27x11.5mm;41x 10 x11.5 mm Package Contents: 4 x Sensor 4 x Receiver Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.