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5-26
SYNCHRONIZATION OF DIGITAL FACILITIES
RULE 7:
The number of nodes receiving synchronization reference from any given node should be minimized.
EXAMPLE FOR RULE 7
Figure 5-19, Excessive Synchronization from One Node, shows an excess of synchronization from one
node. If transmission facility linking nodes A-B fails, then nodes B, D, E, and F will lose their
synchronization. However, if this same facility fails in figure 5-20, Minimized Synchronization from
One Node, only nodes B, D, and E will lose synchronization. Node F remains synchronized to the
network.
With few exceptions, it is not possible to engineer a synchronization network that will satisfy all seven
rules. In general, rules 1 through 3 apply in all cases. For rules 4 through 7, use those rules that
apply to your specific network and try to minimize outages based on the cases presented in the
examples for each of these rules.
DIGITAL TRANSMISSION FACILITY
PRIMARY FREQUENCY REFERENCE
SECONDARY (BACKUP) FREQUENCY REFERENCE
Figure 5-19. Excessive Synchronization from One Node