| 摘要 |
PROBLEM TO BE SOLVED: To improve the reliability of the entire system by realizing a redundant configuration of an efficient line concentration function with respect to the subscriber system transmitter with line concentration function. SOLUTION: A mode changeover means 14a of a remote section 10 selects an operating mode, and an occurrence of a fault in a remote section line concentration connection means 13a, no line concentration processing is conducted but a bypass means 19 directly connects a call from a subscriber terminal 90 to a trunk side transmission line 71. On the occurrence of the fault in the remote section line concentration connection means 13a, since the remote section 10 does not conduct line concentration processing, a central section line concentration connection means 58a of a central section 50 applies the line concentration processing to the call from the remote section 10.
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