| 摘要 |
PROBLEM TO BE SOLVED: To enhance communication connection performance of an ISDN terminal adaptor by providing a means that makes a temporary substitute reply to supplement delay in transmission reception of a message in the case that the delay in the transmission reception of the message through a control channel is detected. SOLUTION: The system is provided with a means that makes a temporary substitute reply to supplement delay in transmission reception of a message in the case that the delay in the transmission reception of the message through a control channel is detected. The ISDN terminal adaptor 1 in this system transmits a call setup message to a transfer destination 4 belonging to other private network 5. The ISDN terminal adaptor 10 that receives a call setup reception message with respect to the setup message starts a delay detection timer (8 sec) 9 for detecting delay in message transmission reception. When the delay detection timer 9 expires after that, the means transmits a call message for a temporary substitute reply so as to avoid a call from being interrupted with a transfer source 3 in the case that the message other than an elapsed display message is not received.
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