AT&T 7400 series, 7500 series manual Figure B-6.Tone-Clock Synchronizer Nonduplicated, Generic

B-12SYNCHRONIZATION OF DIGITAL FACILITIES

____________________________________________________________________________________________________________________________

_

EXTERNAL SYNC SOURCE

STRATUM 4 ACCURACY CLOCK

PRIMARY REFERENCE

TN768 or TN780 CIRCUIT PACK

TONE

GENERATOR

MAIN

PHASE-

LOCKED

LOOP

MISCELLANEOUS TONES

MAIN SYSTEM BUSS

EXTERNAL SYNC SOURCE

SECONDARY

REFERENCE

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

__________________

1. For Generic 1, R1V5.0, only the TN780 can be used in an external stratum 3 clock configuration.