| 摘要 |
An electronic private branch exchange includes a first fault detection portion, a first alternate control portion, a second fault detection portion, and a second alternate control portion. The first fault detection portion detects occurrence of a fault on a private line for connection to a remote electronic private branch exchange (EPBX). The first alternate control portion selects one of a plurality of integrated services digital network (ISDN) lines registered in advance after the first fault detection portion detects occurrence of the fault, thereby forming a first alternate communication path for alternate connection to the remote EPBX. The second fault detection portion detects occurrence of a fault on a first alternate line formed by the first alternate control portion. The second alternate control portion selects one of the ISDN lines registered in advance except for an ISDN line on which occurrence of a fault has been detected after the second fault detection portion detects occurrence of the fault, thereby forming a second alternate communication path for alternate connection to the remote EPBX.
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