Electronic surface-mounted air conditioning controller for heating/cooling control in 2- and 4-pipe systems for hotel, residential and commercial premises. Designed to control continuous valve actuators, both normally closed and normally open. The switch can be used to select between the operating modes Off/Comfort/ECO. The dew point monitoring option makes it particularly suitable for cooling ceiling control. To compensate for the inertia of controlled systems with cooling ceilings, the device has a temperature sensor input for connecting an external radiation sensor (optional). The factory-set “zero point” of approx. 21 °C can be adjusted by ±5 K in the device. The setpoint temperature can be adjusted by ±3 K around the set zero point using the adjustment knob. The external sensor can also be designed as a room sensor (optional) as an official variant, where the controller should be inaccessible to unauthorized persons. An internal potentiometer can be used to select the use of the internal or external sensor or the use of both sensors with an adjustable weighting. Contact inputs for ECO function and OFF (frost protection).