Nortel Communication Server 1000S Installation And Configuration Manual page 203

Clock Controller description and installation
Figure 63
Example 4, Alternate Clocking from the same CO
Small System or
Central Office
Small System
LD 60
TRCK PCK
Slave
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.
In this case, a digital connection to the Central Office can 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= <cr>). In this example, this is
illustrated by the node which supports loops X and Z.
ISDN Primary Rate Interface
Master Clock
Master clock source:
Non-tracking (Free-run)
LD 60
TRCK FRUN
LD 73:
PREF <cr>
SREF <cr>
loop Y
loop Z
Page 203 of 394
loop X
Small System
LD 60
TRCK PCK
LD 73:
PREF loop X
SREF <cr>
Clocking off Master:
Tracking on Primary
loop X and leave the
Secondary Reference
blank.
553-AAA0068
Installation and Configuration
Slave