| 摘要 |
PROBLEM TO BE SOLVED: To avoid a line from becoming impossible to use though a single trunk is broken by providing plural trunks on the same line and providing a communication line and an information line for controlling a seat interval to be capable of parallel operation. SOLUTION: Active data are exchanged with each other between the different seats of the trunk 1, operation becomes cooperative. Then, in spite of generating the fault of a communication line or an information line 9 of seat interval control, the trunk 1 itself is provided with a detecting function in the state of the line to make it possible to operate singly. Namely, when a link is formed at the time point of calling at a common power line, a calling seat executes the calling operation of a normal common power line, the other seat displays presently using of the line and the trunk 1 releases the line 10 to avoid influence by a signal. Calling operation is finished with answering of an opposite side and though the other seats still display presently using of the line, the inhibition of line acquirement is released to make line acquirement possible. Power feeding when the trunk 1 line-acquired, is assignment of individual trunks 1.
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