| 摘要 |
A clock regeneration apparatus which regenerates and distributes a timing signal in a synchronous data transmission network. The network is organized by a plurality of transmission units being linked in a ring topology, and at least two transmission units have external clock sources for synchronization purposes. The clock regeneration apparatus, disposed in each transmission unit, has a clock source list that contains entries for at least two line clock sources provided from neighboring transmission units. A clock selection controller selects a reference clock source with which the transmission unit is to be synchronized. A clock quality transmitter supplies one of the two neighboring transmission units that is not selected as the reference clock source by the clock source selection controller, with a message requesting not to use a corresponding line clock source for synchronization. This message transmission occurs only when the transmission unit is configured as a slave unit, and when the clock quality messages received from the neighboring transmission units exhibit equal clock quality levels continually for a predetermined period.
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