| 摘要 |
PROBLEM TO BE SOLVED: To realize automatic changeover of a line with only a line control mechanism, without the need for a line changeover device for changeover into a backup line on the occurrence of faults in the line and to use the backup line so as to inform a 3rd party about the occurrence of the fault in the line. SOLUTION: Line control mechanisms 1, 2 is provided with two line interface circuits 12, 13, a line changeover control section 11 that selects the interface circuit 12 or 13, a line control section 10 that controls data transmission/ reception and a communication protocol, a common control section 9 that controls the line control section 10 as a whole, the line changeover control section 11 and the line control devices 1, 2 and a ringing monitor section 14 that monitors an incoming call from a backup line 6 and informs the common control section about the arrival of an incoming call. When a fault in a main line 5 is detected, the line control mechanisms 1, 2 inform a 3rd party 8 about the occurrence of the line faults by using the backup line 6 and changes over the communication line from the main line 5 to the backup line 6.
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