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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The DDN_AIS is an alarm indication signal at the DDN port. If a board has detected that the signals at the DDN port are all "1"s, the DDN_AIS alarm is reported.


Alarm Severity Alarm Type


Communication alarm



Impact on the System

When the DDN_AIS alarm occurs, the accessed signals at the DDN port are useless.

Possible Causes

The possible causes of the DDN_AIS alarm are as follows:

  • The AIS alarm is inserted in the services in the upstream DDN equipment connected to the electrical interface on the DDN board.
  • The receive unit of the board at the local station is faulty.


  1. View the DDN_AIS alarm on the U2000 to confirm the relevant board.
  2. Check whether the accessed E1 signals of the board are reported normally. After making sure that the accessed E1 service signals are correct, check whether the DDN_AIS alarm is cleared.
  3. If the alarm persists, replace the board.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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