公开(公告)号：US3585311A

公开(公告)日：1971-06-15

申请号：US3585311D

申请日：1969-09-02

Applicant: BELL TELEPHONE LABOR INC

Inventor： BERKLEY DAVID A ,  MITCHELL OLGA M M

IPC: H04B3/21 ,  H04M9/08

CPC classification number: H04M9/087 ,  H04B3/21

Abstract: The effect of circuit echo and long-time room reverberation in telephonic links are reduced by contiguous band filtering of the signal followed by center clipping of the filter outputs. Distortion products of the clippers are removed in a second filtering stage. A two-thirds octave filter passband width is advantageous.

公开(公告)号：US3622714A

公开(公告)日：1971-11-23

申请号：US3622714D

申请日：1969-09-02

Applicant: BELL TELEPHONE LABOR INC

Inventor： BERKLEY DAVID A ,  COURTNEY-PRATT JEOFRY S

IPC: H04B3/21 ,  H04M9/08 ,  H04Q1/453

CPC classification number: H04Q1/453 ,  H04B3/21 ,  H04M9/087

Abstract: This disclosure describes a system for assuring circuit stability in a telephonic link having substantial acoustic coupling at stations therein, as well as eliminating remote end echo in such circuits. The system uses complementary comb filter banks in which the passband center frequencies are selected to reduce the incidences of harmonic relations among the passband at any one of the filter banks. The system is adapted also to the reduction of electrical circuit echo.