The device combines the functions of a KNX bus coupling unit, single-room temperature controller with setpoint presetting, temperature and humidity sensor and CO2 sensor in one bus device. The room temperature controller, humidity and CO2-Sensor functions are each independent function sections of the device with their own parameter blocks in the ETS. The functions can be configured in the ETS. In addition, the device has two binary inputs that can be disabled during operation, and by means of which actuators can be controlled via KNX telegrams, e.g., for controlling fans or window drives. Through the combination of all functions it is possible to monitor the indoor air quality and to control measures for preserving the air quality via the bus.