| 摘要 |
PROBLEM TO BE SOLVED: To enable a present telephone call state of an IP telephone terminal to be specified even if the IP telephone terminal has no function of generating instructing information indicating instructions or the like of a telephone call start to be transmitted. SOLUTION: When an SIP message which radio IP telephone terminals 1a, 1b and a call control server 3 use for establishing communication is detected, a type of the message is determined, and telephone call states of the radio IP telephone terminals 1a and 1b are specified from the type of the message. Thus, even if the radio IP telephone terminals 1a and 1b have no function of generating the instructing information indicating instructions or the like of a telephone call start to be transmitted, present telephone call states of the radio IP telephone terminals 1a and 1b can be specified. COPYRIGHT: (C)2007,JPO&INPIT
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