Telecommunications Radioelectriques Et Telephoniques T.r.t.

Christian Dagorn

Jean Lassaux

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 N.sub.REC of this signal and the levels N.sub.AV and N.sub.AP of the signals before and after the subtractor (13). It comprises a controller (21) for comparing the level N.sub.AV to two fixed thresholds N.sub.AV0, N.sub.AV1 and for comparing the ratio N.sub.AP /N.sub.AV to a threshold a which is capable of varying as a function of N.sub.AV, the center clipper being only set to its active state when the level N.sub.AV is comprised between N.sub.AV0 and N.sub.AV1 and the ratio N.sub.AP /N.sub.AV is below a threshold a, the clipping threshold varying in accordance with an increasing function of the level N.sub.AV.

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Perros Guirec, France

Christian Dagorn