| 摘要 |
A communications path not using a deterministic signal frame structure is generally not provided with a performance monitoring system or error detection system. A communications path may be provided with performance monitoring by using known Alarm Indication Signal (AIS) type monitoring on the path but scrambling traffic signals in a scrambler (4) to avoid them being mistaken for an AIS. At the receiving end (8) of the path (5), monitoring means (9) is used for monitoring the received signals for the presence of an AIS, followed by a descrambler (10) to unscramble said received signals before transmitting them to a receiving piece of CPE (12). An adverse state detector may also be provided, to avoid the scrambler (4) scrambling traffic signals so that they look like an AIS.
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