Telephonic communications – Supervisory or control line signaling – Using line or loop condition detection
Patent
1997-09-30
1999-08-03
Eisenzopf, Reinhard J.
Telephonic communications
Supervisory or control line signaling
Using line or loop condition detection
379390, 379388, H04M 100
Patent
active
059334932
ABSTRACT:
Known is a telecommunications system comprising a near end and a far end subscriber unit communicating with each other via a transmission channel, at least the near end subscriber being arranged for handsfree communication. In the known system, the near end subscriber unit comprises a duplex controller controlling the near end subscriber unit to three stable modes, a transmit mode, a receive mode, and an idle mode. The known subsciber unit operates in half-duplex mode and has speech and noise detectors for the transmit and receive paths, and a speech level comparator controlling the mode switching. At mode switching, suitable gain adaptation is done in the transmit and receive path so as to prevent howling in handsfree mode. The known duplex controller does not operate satisfactorily if the near end speaker is at a relatively large distance from the microphone. A telecommunications system is provided that satisfactorily operates when the near end speaker is a relatively large distance from the microphone. Time constants of the system are influenced when the far end speaker stops talking and the near end speaker takes over such that no speech loss occurs at the far end.
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Philips Application handbook 1995, "Wirebound Telecom", Nov. 1994, pp. II-263 to II-300.
Speech/transmission circuits, Application of the speech-transmission circuit 1064, Nov. 1994, pp. II-69 to II-74 and II-123.
Beijer Paul A.C.
Rijnberg Adriaan J.
Appiah Charles N.
Eisenzopf Reinhard J.
U.S. Philips Corporation
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