| 摘要 |
PROBLEM TO BE SOLVED: To provide a private branch exchange, a gateway apparatus, an IP phone system, and a speech quality control method thereof capable of enhancing an echo suppression amount by the gateway apparatus and obtaining an expected speech level without changing a prediction signal expected by an echo canceller. SOLUTION: A gain control section 13 of a key telephone set connected to the gateway apparatus 2 including the echo canceller 25 to configure the IP phone system searches gain information denoting a gain to be attached corresponding to each line accommodated by a master unit 1 from a public line interface section 14. The searched gain information is outputted to the gateway apparatus 2 via an ISDN interface section 16. A gain control section 23 receives this gain information. The echo canceller 25 adds the received gain information to the signal received from a LAN line to calculate a pseudo echo and adaptively controls a prediction function so that a difference signal between an output signal of the echo path and the pseudo echo is minimized. COPYRIGHT: (C)2006,JPO&NCIPI
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