The indoor sensor for the Sewi KNX system monitors the presence of persons and the brightness e.g., to switch light in an energy-optimized way. In addition, temperature, air humidity and CO₂ can be measured for ambient climate control. The sensor is mounted on the ceiling or wall and is available in different variants as single or combined unit. The models offer additional functions like calculation of mixed values, a room climate controller, an energy-saving summer compensation for cooling, logic gates and multifunctional modules for transformation and conversion of data.