AT&T 7100 series, 7500 series, 2500 series, 7200 series, 7400 series manual CROSS-CONNECT B25A Cable

SYNCHRONIZATION OF DIGITAL FACILITIES B-15

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and secondary references also apply to these references.

For System 85 and Generic 2, all functions previously performed by SCS synchronization software are now provided external to the switch — by the external clock. Furthermore, the switch does not know which reference (1 or 2) is online nor can the switch change from one reference to the other. phil/figb-7

PUBLIC

NETWORK

	YELLOW
	CROSS-CONNECT
B25A CABLE	FIELD
Y-CABLE		REF. 1
			EXTERNAL
NCTE
			CLOCK
		REF. 2	(NOTE 4)
NCTE		CLOCK A
		CLOCK B
			ALARMS
	NOTE 2	NOTE 1
			SWITCH
			TN492C OR
		EXTERNAL ALARM
			INTERFACE
	ALARMS		TN2131
		EXTERNAL-
			CLOCK
	B25A CABLES	INTERFACE
C6F OR			DS1
GR-380
CABLES			DS1

NOTE 3

NOTES:

1.The external clock cabinet has one 50-pin connector. It is labeled EXT CLOCK OUTPUT. One B75A cable is required for connecting the cabinet to the cross-connect field.

2.Refer to the appropriate installation manual or wiring guide for details on how to configure the cross-connections.

3.The TN492C or external alarm interface and TN2131 apply only to System\⎪85 and Generic\02.

4.When the external clock is used, the SCS must not be administered. Those SCS software functions are done by the hardware and firmware within the external clock.

Figure B-7.Public-Network External Clock

The external clock is designed to provide stratum-3 reliability and exists in a duplex version. This version provides hot standby capability (the ability to pull out circuit packs with power on) to the alternate clock and may be used with a switch containing a single module or TMS control or a duplicate module or TMS control. Figure B-8,External Clock, shows a functional diagram of the external clock.