Echo canceller and center clipper control arrangement

摘要

This arrangement is intended to control the operation of the coefficients adjusting circuit (12) of an echo canceller and of the operation of a center clipper (15) inserted in the send path (7) of a four-wire circuit at the output of the subtractor (13) of the echo canceller for suppressing there, when it is set to its active state, the signals whose amplitude is lower than or equal to a clipping threshold. The control arrangement operates on the basis of the signal in the receive path (2) of the four-wire circuit, the level NREC of this signal and the levels NAV and NAP of the signals before and after the subtractor (13). It comprises a controller (21) for comparing the level NAV to two fixed thresholds NAV0, NAV1 and for comparing the ratio NAP/NAV to a threshold a which is capable of varying as a function of NAV, the center clipper being only set to its active state when the level NAV is comprised between NAV0 and NAV1 and the ratio NAP/NAV is below a threshold a, the clipping threshold varying in accordance with an increasing function of the level NAV.