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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The OOL alarm indicating that the phase-locked loop (PLL) on the cross-connect board is out-of-loop.


Alarm Severity Alarm Type


Equipment alarm


When you view an alarm on the network management system, select the alarm. In the Alarm Details field display the related parameters of the alarm. The alarm parameters are in the following format: Alarm Parameters (hex): parameter1 parameter2...parameterN. For details about each parameter, refer to the following table.

Name Meaning

Parameter 1

Indicates the type of failed PLL.

  • 0x01: first 2M PLL
  • 0x02: second 2M PLL
  • 0x03: 38M analog PLL
  • 0x04: 77M PLL on the alarmed board
  • 0x05: 77M PLL on the board in the extended slot

Impact on the System

The phase-locked loop cannot lock the input signals and outputs poor clock signals. As a result, quality of services deteriorates or even services are interrupted.

Possible Causes

The possible cause of the OOL alarm is as follows:

The phase-locked loop is damaged.


  1. Check whether the active clock board reports the OOL alarm.

    If... Then...

    The active clock board reports the OOL alarm

    Perform switching from the active clock board to a standby clock board and check whether the alarm is cleared. If the alarm persists, go to the next step.

    A standby clock board reports the OOL alarm

    Go to the next step.

  2. Replace the board that reports the alarm. The alarm is cleared automatically.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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