Abstract: According to the principles of the invention, there is provided a system that identifies spurious noise values in an input signal and replaces them with substitute values representative of the spurious-noise-free signal. The system is activated when the signal deviation exceeds a predetermined threshold, otherwise passing the signal unchanged. The substituted representative values are determined based on historical signal data, preferably a moving average with a fixed window. There is further provided a maximum glitch width which prevents inadvertent suppression of a true step in the input signal, and a relaxation time which prevents consecutive filter activations from unduly masking the input signal.