| 摘要 |
PROBLEM TO BE SOLVED: To provide an IP telephone set which can maintain a call when trouble occurs in a DATA network during the call using DATA network. SOLUTION: When trouble occurs in the DATA network 9 during a call with a terminal on the DATA network 9, in the state that power is supplied from the DATA network 9 or a commercial power supply 8 to the IP telephone set 5, the call is once cut off, and the IP telephone set 5 is connected again with a PSTN network 2 and begins a call. When the DATA network is restored afterward, the IP telephone set 5 maintains the call with the PSTN network 2. COPYRIGHT: (C)2004,JPO
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