Nortel Modular ICS 6.0 Installer's Manual page 53

reference network connection, or the loop fails, the next
available, functional, network connection is used for clock
synchronization.
The clock synchronization process generates alarm codes and
event messages. See the Alarm codes on page 506 and Event
messages on page 514 for more information.
When you configure the network connections to the Modular
ICS, you should take into account the system preferences for
selecting loops for synchronization:
• lower numbered loops have preference over higher
numbered loops
• the loop preference order is: 201, 202, 203, 204, 225, 226,
227, 228
• the system skips U-LT, S, and analog loops when selecting
a network connection for synchronization
Systems with only U-LT and S loops act as timing masters for
the attached terminal equipment (TE), and are not
synchronized to the network. ISDN TE without access to a
network connection (BRI lines) has limited or no
functionality.
If your system has both a BRI and a DTI card configured as
PRI installed, it is recommended that you use PRI as the
primary clock source, see DTI card configured as a PRI card
on page 47.
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Modular ICS 6.0 Installer Guide