Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1997-02-10
1998-06-16
Zele, Krista
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379389, 379390, 379420, H04M 900
Patent
active
057683646
ABSTRACT:
In a speakerphone, which operates under software control, transmit and receive signal levels are sampled and compared against one another, with hysteresis, to enable one of two speakerphone modes of operation--either a transmit mode or a receive mode. A single peak detector is multiplexed to sense the transmit and receive signal levels. Fixed attenuators are switched into either the receive signal path or into the transmit signal path, depending upon the current speakerphone operation mode. Signal compression is used to provide for improved mode determination over a wide dynamic range. The level detection and/or attenuation may be performed in software. The speakerphone functions are readily implemented using standard line interfaces and control circuitry. Automatic gain control in the receive mode ensures a constant level of signals at the speakerphone loudspeaker, regardless of telephone line conditions.
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Karnowski Mark J.
Sacca Frank
Tsang Catherine
Casio PhoneMate, Inc.
Saint-Surin Jacques M.
Zele Krista
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