| 摘要 |
PURPOSE:To offer various packet exchange services even to a system which is not in use by connecting both systems of terminals of dual systems to a packet network and providing logical channels respectively and sending data which indicates whether a communication is possible or not between both the systems of the terminals. CONSTITUTION:For example, when the system TA1 of a terminal 10 is put in use, the system TA1 sends data indicating that a communication is possible to both systems TA2 and TB2 of a terminal 20 covered by an exchange 20 through a local channel. Here, when the system TA2 of the terminal 20 is in use, the system TA2 sends an acknowledgment answer and the system TB2 sends a negative acknowledgment answer. The acknowledgment data of the system TA2 and the negative acknowledgment data of the system TB2 are received by the systems TA1 and TB1 of the terminal 10. Consequently, the system TA1 of the terminal 10 is enabled to have a communication with the system TA2 of the opposite terminal and terminal data are transmitted through the logical channel. At this time, a system which is not in use is connected to the packet network, so the system is offered the packet exchange services.
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