Abstract: An adaptive filter in an echo canceling circuit includes a clipping detector that affects the coefficients of the adaptive filter when clipping is detected. Clipping is defined as at least two successive maxima or minima in a predetermined period. The coefficients are either locked or the echo estimate is reduced to prevent overcorrection. In accordance with another aspect of the invention, lower order bits are ignored to avoid problems of bit resolution when comparing signals.

Abstract: An adaptive filter is programmed with an algorithm based on a normalized Least Mean Squares (nLMS) algorithm that adapts each sample time. The algorithm is modified to be more efficient in a variety of DSPs by computing multiple errors, one per sample, before updating coefficients. The update equation utilizes the multiple errors to achieve adaptation at a similar performance to known nLMS algorithms that adapt each sample time but without the instability that is observed in low echo-to-near-end-noise ratio (ENR) input conditions. Varying the relaxation step size prevents divergence. The DSP utilizes either one or more MAC units.

Abstract: An expressor for varying the amount of fluid in a variable-volume container connected to at least one conduit includes a housing defining an enclosed chamber which can accommodate the container. The housing has at least one opening through which a conduit can extend. A pressure regulating mechanism is coupled to the housing to vary the pressure of fluid in the chamber and thereby vary the volume of the container.