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Circuit Pack Descriptions
Issue 3 June 2001
7-15
Synchronization 7
Synchronization Functions 7
The DDM-2000 OC-3 Multiplexer supports three synchronization modes:
1. DS1 timing input from stratum 3 or better office clock for CO applications
2. Free-running in CO applications when external timing inputs are not
available
3. Line (formerly loop) timing for remote timing functions.
In addition, the BBF2B/BBF4 TGS/TG3 circuit pack provides a DS1 timing output
that is used for network synchronization and allows line (formerly loop) timing and
DS1 Output timing to be derived from either the main or function unit C OLIU.
The timing circuit packs distribute clock and frame signals, derived from the
selected reference source, to the transmission circuit packs. The BBF4 circuit
pack provides stratum 3 accuracy while the BBF2B provides stratum 4 accuracy.
BBF2B/BBF4 TGS/TG3 Circuit Pack Description 7
Purpose of Circuit 7
The synchronous timing generator (TG) circuit pack provides timing for the shelf.
Other functions include a derived DS1 output for use as a reference signal by a
building integrated timing supply (BITS) or a DS1 MULT capability for
synchronizing other shelves in the bay. The derived DS1 is traceable to timing
from either the main or function unit C OLIUs.
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