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Example 4
Alternate Clocking from the same CO
Slave
Option 11 or
Central Office
Option 11
LD 60
TRCK PCK
LD 73:
PREF loop Y
SREF loop Z
Clocking off Master:
Tracking on Primary
loop Y and loop Z
used as a secondary
clock source.
Chapter 4 — Network Clocking Page 849 of 1536
Master Clock
Master clock source:
Non-tracking (Free-run)
LD 60
TRCK FRUN
LD 73:
PREF
SREF
loop Y loop X
loop Z
Option 11
LD 60
TRCK PCK
LD 73:
PREF loop X
SREF
Slave
Clocking off Master:
Tracking on Primary
loop X and leave the
Secondary Reference
blank.
553-7564.EPS
In this case, a digital connection to the Central Office may exist (i.e. Loops X
and Y). When a second Digital loop from the CO or Master M-1 becomes
available, it can be used as a Secondary Clock Source in case the Primary
Source fails.
To avoid timing loops, in example 4-4 the most reliable slave system should
not have a Secondary Clock Source (SREF= ). In this example, this is
illustrated by the node which supports loops X and Z.
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