AT&T DS1/DMi/ISDN-PRI manual 12ADMINISTRATION Options and Requirements System

7-12ADMINISTRATION OPTIONS AND REQUIREMENTS — SYSTEM 85

	slip count of 44 or less and if the secondary and 50% of those DS1s that are enabled
	for slip enable have reached their maximum slip count of 88, then a switch back to
	the primary is made.
Field 11	V1-V4
	Offers the options external loop not available (0) or external loop available (1).
	The external loop available option should only be selected when demand diagnostic
	maintenance is done and then only after a DS1 has been busied out. If DS1 is a
	primary or secondary reference, the reference should be switched off line. This
	option is used with procedure 620, test 2, to extend the range of the test to include
	the network channel-terminating equipment (NCTE) and the connecting facility.
	The external loop available option should only be used for the duration of the test.
Field 12	V1-V4
	Specifies whether (1) or not (0) the associated T1-span is used as an incoming
	synchronization source to the switch.
	The network synchronization diagram should show those transmission facilities that
	are used for synchronization. Each switch permits a maximum of two interfaces
	(one primary and one secondary) to be translated (1) in field 12. However, there is
	no requirement to have both.
Field 13	V1-V4

Selects whether a DS1 facility (translated in field 12) is to be used as the primary or secondary synchronization source to the switch. Field encodes and their descriptions are:

0The facility is not used as a synchronization source

1The facility is the primary synchronization source

2The facility is the secondary synchronization source

NOTE: The primary must be administered before the secondary. The secondary must be removed before the primary.

Only slots translated (1) and (2) must be configured with synchronization cables. These cables connect the backplane of the translated ANN11_/ANN35 to the backplane of the TN463. The cables are identified as group 334 for intercabinet and group 361 for intracabinet applications.

CAUTION: A loop-timing problem can be created if the synchronization sources are not administered correctly. The loop-timing problem exists as the result of an error where both switch endpoints (for the same T1-span) are administered as the primary. This causes the clock frequency to vary widely and result in bringing down the switch. Loop-timing problems can be avoided by following a correctly engineered network synchronization diagram.