Full duplex telephone set using echo cancellation and side...

Details Full duplex telephone set using echo cancellation and side... Full duplex telephone set using echo cancellation and side...

2006-02-21

2006-02-21

Tran, Sinh (Department: 2646)

Telephonic communications

Echo cancellation or suppression

C379S391000

Reexamination Certificate

active

07003096

ABSTRACT:
A full duplex telephone set for hearing impaired users includes a digital signal processor incorporating a pair of adaptive transversal filters to cancel line and acoustic echo feedback from the tip and ring signals of the set, and to condition and control the amount of a replacement side tone fed back to the receiver. This enables at least 50 dB of gain to be applied to the modified received signal without initiating unstable operation, or howl, in the set, and ensures that the received and side tone signals are heard by the user with equal comfort and clarity. The digital signal processor also enables additional enhancements to be made to the modified received signal that are beneficial to hearing impaired users, such as dynamic range compression, “soft” limiting, and low level emphasis within selectable frequency bands.

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