Operational status controller for echo canceling

Details Operational status controller for echo canceling Operational status controller for echo canceling

1989-10-26

1991-07-02

Ng, Jin F.

Telephonic communications

Echo cancellation or suppression

379410, 370 321, H04M 100

Patent

active

050292048

ABSTRACT:
An apparatus for controlling the operational status of echo canceling in an echo canceler is disclosed. A digital signal processor (DSP) module (52) is configured to provide two bandlimited filters (66, 68). A CAT filter (66) detects the exclusive presence of a continuity assurance. Test (CAT) tone, and a disable filter (68) detects the exclusive presence of an echo canceling disable tone. Outputs from the DSP module (52) couple to a controller module (64), and a control output from the controller module (64) couples to an echo canceler module (54). The control output causes the echo canceler module (54) either to provide echo canceling or to bypass echo canceling. Upon detection of the CAT tone (106), the control module (64) enables echo canceling (88). After the CAT tone disappears (90), the control module (64) monitors the disable filter (68) to determine whether the disable tone is being transmitted (94). If the disable tone is detected, the control module (64) disables echo canceling (100). After the disable tone disappears (102), the control module (64) monitors the CAT filter (66) to determine whether the CAT tone is being transmitted (106).

REFERENCES:
patent: 3700810 (1972-10-01), Richeson, Jr. et al.
patent: 3783194 (1974-01-01), Vilips et al.
patent: 3927265 (1975-12-01), Roedel et al.
patent: 3987398 (1976-10-01), Fung
patent: 4560842 (1985-12-01), Homer
Digital Echo Canceler EC7600-M2 Description and Operation Instruction Manual, Granger Associates, GRAC 098-2671, Revision A, May 1986.

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