The control device of the thermostatic valve is a proportional temperature regulator, composed of bellows containing a specific thermostatic liquid. As the temperature increases, the liquid increases in volume and causes the bellows to expand. As the temperature decreases the opposite process occurs; the bellows contract due to the thrust of the counter spring.

The axial movements of the sensor element are transmitted to the valve actuator by means of the connecting stem, thereby adjusting the flow of medium in the heat emitter.