| 摘要 |
PROBLEM TO BE SOLVED: To improve the quality of call performed between an intercom slave set and an external call terminal at a forwarding destination. SOLUTION: First and second echo cancelers 9 and 10 are provided between a voice switch 20 and first and second 2-4 wire conversion sections 5 and 6, respectively. Therefore, although echo components on a signal path are also amplified in first and second call volume adjusting amplifier sections 24 and 25 having automatic gain control, an offensive echo or howling can be suppressed because the echo cancelers 9 and 10 cancel echo components of first and second feedback routes respectively to disconnect a closed loop, unnecessary echo components are not amplified in the sections 24 and 25, and the quality of call between the intercom slave set B and the external call terminal C. COPYRIGHT: (C)2004,JPO&NCIPI
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