| 摘要 |
PROBLEM TO BE SOLVED: To provide a telephone system in which a call to an outside line terminal can be continued even if a failure occurs in an extension SIP terminal during communication between the extension SIP terminal and the outside line terminal. SOLUTION: In the communication system, a SIP server for performing call control, a message server for supplying a voice message to the outside line terminal, and a plurality of extension SIP terminals are connected over a LAN. The SIP server instructs the message server to transfer the call during communication from a first extension SIP terminal when a failure occurs in the first extension SIP terminal communicating with the outside line terminal and puts the call into a hold state. At this time, the message server establishes a communication path for the call to the outside line terminal and supplies the voice message for a hold time to the outside line terminal. When a second extension SIP terminal issues a hold release notification, the SIP server orders the release of the communication path to the message server and establishes the communication path between an outside line device and the second extension SIP terminal. COPYRIGHT: (C)2011,JPO&INPIT
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