Digital echo suppressor noise insertion

Details Digital echo suppressor noise insertion Digital echo suppressor noise insertion

1975-04-24

1976-11-09

Claffy, Kathleen H.

H04B 320

Patent

active

039912876

ABSTRACT:
During echo suppression in a system utilizing a full echo suppressor, noise is typically inserted in the receive line of the near-end party to assure him that the line has not "gone dead". The need for a separate noise source for this purpose is eliminated in a digital system by using the existing coded incoming signals on the line. Thus, during echo suppression the bits of the coded incoming signal are altered to provide a random noise signal of normal background amplitude which is then inserted on the receive line. In an illustrative companded sign magnitude code embodiment, the sign bit is replaced by the least significant bit, the least and next-to-least significant bits are interchanged and the remaining bits are zeroed, thereby producing an unintelligible background noise signal of appropriate amplitude.

REFERENCES:
patent: 3471657 (1969-10-01), Holman et al.
patent: 3673355 (1972-06-01), La Marche et al.
patent: 3699273 (1972-10-01), Montgomery
patent: 3823275 (1974-07-01), La Marche et al.

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