AT&T DS1/DMi/ISDN-PRI manual Tone-Clock Synchronizer Nonduplicated, Generic

5-12SYNCHRONIZATION OF DIGITAL FACILITIES

EXTERNAL SYNC SOURCE

STRATUM 4 ACCURACY CLOCK

PRIMARY REFERENCE

TN768 or TN780 CIRCUIT PACK

TONE	MISCELLANEOUS
GENERATOR	TONES

MAIN
PHASE-	MAIN SYSTEM
LOCKED
	BUSS
LOOP

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: