Abstract: The invention concerns, according to the first teaching, a sound damper for ultrasonic waves in a gas flow, with at least one damping element (3) that can be inserted into a line for the gas flow. In accordance with the invention, the sound damper for ultrasonic waves is characterized by the fact that at least one scattering unit (5, 6, 7) having a number of small reflective surfaces is located in the damping element (3).

Abstract: Method and apparatus for converting an analog input voltage signal (preferably in the form of a low-frequency rectangular voltage) to a digital output signal proportional to the input voltage. The input voltage is integrated to the integrator voltage over a certain integration time. After the expiration of the integration time, the integrator voltage is de-integrated to zero over a de-integration time by a reference voltage and the input voltage is found from the ratio of de-integration time to integration time, multiplied by the reference voltage. During the integration time, modulation pulses, preferably derived from the reference voltage, are superimposed on the input voltage and thus the integrator voltage is influenced, so that a given integrator voltage is obtained regardless of the input voltage.