It's a wireless smart thermostat with Open Window Detect function. It means open window mode is enabled in the parameter setting, the system will automatically stop heating when thermostat detects a sudden drop of room temperature (2°C in 15 minutes as default). This is normally caused when a window or door is opened without turning off the heating device.  Item No.: WT-15 Programmability: 7days programmable Mode: Heating and cooling mode (Default heating mode)  Backlight: White Material:  ABS+PC Packing : Netural White Box, OEM acceptable Other function: Child lock, Open window detection, Frost protection, Temp. calibration  Optional: Opentherm protocol, WiFi optional, Zigbee optional Cetificate: CE, ROHS, UKCA, REACH, RED