Patent ID: 6256291
Filing Date: 2001-07-03
Classification: B41J

Abstract:
A method of switching between redundant routes of a communication system provided with first and second terminal stations each having a first apparatus for sending working/protection main signals toward the opposing terminal station and receiving working/protection main signals from the opposing terminal station, and a second apparatus for selecting, and sending to the opposing terminal station, one of the working/protection main signals output from the first apparatus toward the opposing terminal station, and for branching a main signal, which has been sent from the opposing terminal station, and inputting the branched signals to the first apparatus as working/protection main signals, the second apparatuses of the first and second terminal stations being connected by an uplink transmission line and a downlink transmission line that are devoid of redundancy, the method comprising:adopting working/protection redundancy for the first and second apparatuses constituting each terminal station;in the first terminal station, multiplexing a working-route identification pattern onto a working main signal as additional data, multiplexing a protection route identification pattern onto a protection main signal as additional data, selecting one of the working/protection main signals and sending the selected signal to the second terminal station via the uplink transmission line;in the second terminal station, identifying the pattern that has been multiplexed onto the signal sent from the first terminal station and detecting line failure of the first terminal station by monitoring signal degradation or signal failure of the signal sent from the first terminal station;when line failure has been detected in the second terminal station, multiplexing additional data, which includes a line failure alarm and a failed route decided from the identification pattern, onto the main signal and sending the main signal to the first terminal station via the downlink transmission line; andin the first terminal station, performing line switching based upon the alarm and the failed route included in the additional data.