This compact sensor immediately detects the opening or closing of windows and doors via an integrated infrared light barrier. Reliable window monitoring keeps your home safe, while at the same time valuable energy is saved when ventilating by automatically lowering the room temperature. In conjunction with Homematic IP radiator thermostats (sold separately), the room temperature is automatically lowered when ventilating. The lowering temperature can even be set individually. When the window is closed, the comfortable temperature is automatically restored.