The body of a valve has an orifice that internally connects a high-pressure passage through which a refrigerant flows in and a low-pressure passage through which the refrigerant flows out. The recalibration is performed on detection of a recalibration trigger event, such as expiry of a recalibration time interval. The steering angle sensor for detecting a steering angle is disposed on one end of the steering shaft, or more specifically, on a lower end portion of an output shaft, or a leading end portion of an output shaft. From the spectrum of the constant intermediate frequencies, in each case the best-suited signal components are selected, separated as constant frequencies from interference portions and evaluated with regard to the relevant information parameters. The circuit comprises a first overvoltage protection device coupled between the fourth node and a fifth node, the fourth and fifth nodes being operatively connected to the first and second nodes, respectively, and a second overvoltage protection device coupled between the third node and the fifth node.