AT&T 2500 series Primary Secondary Reference Indicators ⎜ Reference, RED YEL Good LOS Misf, Blue

B-10SYNCHRONIZATION OF DIGITAL FACILITIES

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∙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 B-1,SCS References Switches, summarizes these conditions:

Table B-1.SCS References Switches

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⎜

Primary

⎜⎜

Secondary Reference Indicators

⎜

⎜

⎜⎜

⎜

⎜ Reference

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⎜

⎜⎜

⎜

⎜⎜

RED

⎜

⎜

YEL

⎜

GOOD

⎜

LOS

⎜

MISF

⎜

BO

⎜

⎜ Indicators

⎜⎜

⎜ BLUE

⎜

⎜

⎜

⎜

⎜

⎜

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⎜

⎜

⎜⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

RED

⎜⎜

HAC

⎜

HAC

⎜

SEC

⎜

SEC

⎜

HAC

⎜

SEC

⎜

HAC

⎜

_

⎜⎜

⎜

⎜

BLUE

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜⎜ HAC

⎜

HAC

⎜

SEC

⎜

SEC

⎜ HAC

⎜

SEC

⎜

HAC ⎜

⎜

YEL

⎜⎜

PRI

⎜

PRI

⎜

PRI

⎜

SEC

⎜

PRI

⎜

PRI

⎜

PRI

⎜

_

⎜

GOOD

⎜⎜

PRI

⎜

PRI

⎜

PRI

⎜

PRI

⎜

PRI

⎜

PRI

⎜

PRI

⎜

⎜

⎜⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

LOS

⎜⎜ HAC

⎜

HAC

⎜

SEC

⎜

SEC

⎜ HAC

⎜

SEC

⎜

HAC ⎜

⎜

MISF

⎜⎜

PRI

⎜

PRI

⎜

SEC

⎜

SEC

⎜

PRI

⎜

PRI

⎜

PRI

⎜

_

⎜⎜

⎜

⎜

BO

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜⎜ HAC

⎜

HAC

⎜

SEC

⎜

SEC

⎜ HAC

⎜

SEC

⎜

HAC ⎜

BLUE

Blue alarm

RED

Red alarm

YEL

Yellow alarm

LOS

Loss of signal

HAC System 85’s internal high-accuracy clock

BO

Maintenance busied out

MISF

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 monitored to make sure that a switch is not attempted to an unhealthy SCS. If the SCS is not duplicated and the HAC is healthy, serious failures cause a switch to the HAC to ensure switch reliability. When the SCS can once more lock onto a DS1 reference, a switch to that reference is performed.

Synchronization occurs at several priority levels; records are kept for perusal at the demand test level with procedure 625. In addition, several yellow LEDs on the SCS can be observed to get a current picture of how the system is configured from a reference clock point of view.

∙The LED in position #4 refers to the primary DS1 reference. The LED is OFF if a synchronization signal is present and the SCS is capable of locking. The #4 LED is ON if an error condition exists and the synchronization cable is present.