AT&T DS1/DMi/ISDN-PRI manual Primary Secondary Reference Indicators, Blue YEL Good LOS Misf, Red

5-10SYNCHRONIZATION OF DIGITAL FACILITIES

●Loss of signal (LOS) at the (SCS) circuit for more than 200 ms. A switch is made to the high- accuracy clock (HAC) on the SCS by the SCS. A further analysis is then made to determine if the LOS is network related or switch related. A switch to a healthy reference is done if appropriate.

●Blue alarm means that the switch cannot be used as a reference.

●Out-of-lock (OOL) condition means that the HAC is unable to lock onto the incoming clock from the current DS1 reference. A switch to a healthy reference is done if one is available. Otherwise, a switch to the HAC is performed.

●Red alarm means that two out of four (or worse) framing patterns were received.

●Slip rate of selected DS1 facilities (with respect to the primary reference) exceeds a given threshold

●Misframes at the primary reference exceed a given threshold

●Reception of a yellow alarm (or a blue alarm for R2V4, 1.1 and later)

●Health of SCS circuit pack

●Insane condition of the board processor on a DS1 circuit

Table 5-1, SCS References Switches, summarizes these conditions:

TABLE 5-1.SCS References Switches

Primary				Secondary Reference Indicators
Reference
			BLUE		YEL	GOOD	LOS	MISF	BO
Indicators	RED
RED	H A C		H A C		SEC	SEC	H A C	SEC	HAC
BLUE	HAC		H A C		SEC	SEC	H A C	SEC	HAC
YEL	PRI		PRI		PRI	SEC	P R I	PRI	PRI
GOOD	P R I		P R I		P R I	PRI	P R I	PRI	PRI
LOS	HAC		H A C		SEC	SEC	H A C	SEC	HAC
MISF	PRI		PRI		SEC	SEC	PRI	PRI	PRI
BO	H A C		HAC		SEC	SEC	HAC	SEC	HAC
		BLUE		Blue alarm
		R E D		Red alarm
		Y E L		Yellow alarm
		L O S Loss of signal
		H A C System 85's internal high-accuracy clock
		B O Maintenance busied out
		M I S F		Misframe
		GOOD		No alarms

The SCS circuit pack's health is examined when the system clock's health is evaluated. Error conditions of varying severity can exist on the SCS. If the fault is minor and the SCS can still lock on the current DS1 reference, a low-priority request for a soft switch to the offline side is made after an unsuccessful attempt to clear up the error condition on the SCS. If the SCS cannot lock onto the current DS1 reference clock, a high-priority request for a soft switch is made. The offline SCS is also