COMMUNICATION LINE SWITCHING METHOD, COMMUNICATION APPARATUS, STATION-SIDE COMMUNICATION APPARATUS, COMMUNICATION SYSTEM, AND CONTROL DEVICE

摘要

In a communication system in which a station-side line terminal apparatus 1 and a user-side line terminal apparatus 10 perform communication via a plurality of redundant physical lines, the user-side line terminal apparatus 10 monitors an out-of-synchronization error and line abnormality of the physical lines and, when line abnormality is detected (P 4 ), shifts from a registered state to a holdover state for deferring discarding of setting information such as link information. The user-side line terminal apparatus 10 suppresses detection of the out-of-synchronization error during a deferred period to prevent a communication link from being disconnected by the out-of-synchronization error and prevent initial setting from being required. The station-side line terminal apparatus 1 switches a line during the deferred period (P 7 ) and, after transmitting a synchronization signal (P 8 ) to synchronize with the user-side line terminal apparatus, resumes normal communication.