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B-12 SYNCHRONIZATION OF DIGITAL FACILITIES
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TN768 or TN780 CIRCUIT PACK
TONE
GENERATOR
MISCELLANEOUS
TONES
MAIN SYSTEM
BUSS
EXTERNAL
SYNC
SOURCE
EXTERNAL
SYNC
SOURCE
MAIN
PHASE-
LOCKED
LOOP
SECONDARY
REFERENCE
PRIMARY
REFERENCE
STRATUM 4
ACCURACY
CLOCK
Figure B-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.
1
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 or secondary 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
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1. For Generic 1, R1V5.0, only the TN780 can be used in an external stratum 3 clock configuration.