| 摘要 |
Network elements (NE1, NE2) of a synchronous digital telecommunications network are synchronized to the reference clock of a primary reference clock. To increase the fault tolerance of the network, two primary reference clocks (PRC1, PRC2) are used. In fault-free operation, the first reference clock signal is transmitted to the network elements and used for synchronization and the second reference clock signal is available as a standby reference clock signal. In case of an error, synchronization is switched to the second reference clock signal. The synchronization process according to the invention provides that, in order to differentiate the two reference clock signals, at least one of the two reference clock signals is marked by a predetermined bit sequence in the overhead of message signals (STM-N) generated by the reference clock signal or by applying a phase modulation to the reference clock signal. This ensures that the network is synchronized by a single reference clock source.
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