Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1992-09-11
1994-11-15
Dwyer, James L.
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379389, 379409, H04M 908, H04M 120
Patent
active
053655834
ABSTRACT:
A method is disclosed for maintaining loop stability between a transmit and a receive path of a speaker phone which is capable of operating in either a full-duplex or a half-duplex mode. Loop stability is maintained and normal operation is achieved by controlling transmit and receive path attenuators. The method first determines whether feedforward or feedback signal levels should be used. Based on this determination, the signal and noise parameters along various points in the transmit and receive path are evaluated. Based on the parameter values, the transmit and receive attenuators are adjusted to maintain loop stability and to operate the speaker phone in the proper state. Additionally, when the speaker phone adjusts the transmit attenuator for greater signal attenuation in order to maintain loop stability the noise fill-in component of the speaker phone will generate additional background noise to maintain a constant background noise level, as perceived by the far-end user.
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Gaut Eric K.
Hinman Brian L.
Huang Shan-Shan
Dwyer James L.
Ferrell John S.
Polycom, Inc.
Weaver Scott L.
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