Abstract: To reduce disturbance and interference signals, and particularly recurring disturbance signals due to vibration or out-of-round conditions of rotating elements coupled to a speed transducer, a low-pass filter (11) is connected to the speed transducer and, in addition, a high-pass filter (12) which, however, is disconnected upon sensing that the speed of the wheel or of the vehicle is below a predetermined limit, or that the anti brake-lock system unit (13) has responded. Thus, disturbance signals, and particularly periodic disturbance signal which might cause oscillatory conditions to arise in the filter and transducer circuitry, are effectively suppressed.