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5-12
SYNCHRONIZATION OF DIGITAL FACILITIES
TN768 or TN780 CIRCUIT PACK
STRATUM 4
ACCURACY
CLOCK
TONE
GENERATOR
MISCELLANEOUS
TONES
EXTERNAL
SYNC
SOURCE
PRIMARY
REFERENCE
MAIN
PHASE-
LOCKED
LOOP
MAIN SYSTEM
BUSS
EXTERNAL
SYNC
SOURCE
SECONDARY
REFERENCE
Figure 5-6. Tone-Clock Synchronizer (Nonduplicated, Generic 1)
System 75 and Generic 1 Synchronization Software Operation
System 75 and Generic 1 synchronization software differs slightly from System 85 and Generic 2
because of architectural differences; however, both switches provide the same overall functions.
Primarily, these functions include monitoring the synchronization references and keeping the primary
or other reference that has the best health online and thus providing high quality digital
communications via DS1 facilities.
A subpart of the maintenance software monitors the TN768 or TN780 circuit packs and
synchronization references. Depending on the state-of-health of the references, the maintenance
software provides automatic switching between the references. Switching from one reference to
another can be done by any of the following conditions:
●
On-line synchronization reference failure
●
Primary reference restoration
●
Administration reference changes, either from Initialization and Administration System (INADS)
or the local Manager-1 (M-1) terminal
●
Craft command from an M-1 terminal
The TN768 and TN780 circuit packs contain edge-mounted LEDs. These LEDs indicate the
following status sequences: