Nortel Modular ICS 6.0 Installer's Manual page 478

478 / Hardware
The installer should ensure that clock source loops are
either not powered down or are among the last to be
powered down.
If BRI cards are used only for S-loops, a Service Card is
required only if the DTI is T1. However, a Services Card is
recommended when a T1 is not used, since the card improves
clock accuracy and performance.
If BRI cards are used off-core, they still require a connection
to the network, which requires the SC, and an on-core digital
clock source.
For more information on network synchronization, consult
the appropriate private digital network synchronization
standards.
The following illustrations show some typical network
configuration and the appropriate clock source settings for
your DTIs.
Norstar connected directly to the service provider in a T1 network
Norstar ICS
Modular ICS 6.0 Installer Guide
Primary - DTI 1 obtains the timing from the service provider
Secondary - DT12 acts as a standby to obtain the timing
from the service provider
T1 or PRI
service provider
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