| 摘要 |
PROBLEM TO BE SOLVED: To obtain an ISDN communication system that allows automatic switching between UUI communication and B channel communication. SOLUTION: When a center 3 side, using a B channel communication system calls on a terminal side, first, communication is performed by a D channel. That is, the center 3 transmits a meter reading request to a line IF 4 (step 201). The line IF 4 sets communication system information representing the B-channel communication system to the caller sub address or the receiver sub address of a SETUP message 21 and transmits the SETUP message to an I-NCU 9 via an ISDN public line (step 202). The I-NCU 9 receives communication system information 37 of the received message 21, recognizes it as the B channel communication system and receives it (step 203). Subsequently, the I-NCU 9 performs communication by using the D channel and the B channel as the B-channel communication system set to the received information 37 (step 204 to step 218).
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