Nortel NT1R20 Description page 206

Page 182 of 290
553-3001-105 Standard 5.00 June 1999
NT5D33 and NTRB34 Line-side E1 Interface Cards
If a repeating device loses signal, it will immediately begin sending an
unframed signal of all ones to the distant end to indicate an alarm condition.
This condition is called a blue alarm, or an alarm indication signal (AIS). If
an AIS is detected for more than two seconds, a level 2 alarm will be declared,
and silence will be sent on all receive timeslots. The alarm will be cleared if,
after two seconds, neither a loss of signal, out-of-frame condition, nor blue
alarm condition occurs.
Alarm Disable
The Alarm Disable (A D) command disables the external alarm
contacts. When this command is typed in, the MMI will display the message
Alarms Disabled and the MAINT LED will light. In this mode, no
yellow alarms are sent and the LEI will not enter line processing mode. Alarm
messages will still be to be sent on the MMI terminal and the LED will
continue to indicate alarm conditions.
Alarm Enable
The Alarm Enable (A E) command does the reverse of the Alarm
Disable (A D) command. It enables the external alarm contacts. When
this command is typed in, the MMI will display the message Alarms
Enabled. In this mode, yellow alarms can be sent and the LEI can enter line
processing mode.
Clear Alarm
The Clear Alarm (C A) command will clear all activity initiated by
an alarm: the external alarm hardware will be deactivated (the contact
normally open will be reopened), the LED will go out, an entry will be made
in the alarm log of the date and time the alarm was cleared, and line
processing will cease (for alarm level 2 only). When this command is typed
in, MMI will display the message Alarm acknowledged. If the alarm
condition still exists, an alarm will be declared again.
Display Alarms
A detailed report of the most recent 100 alarms with time and date stamps can
be displayed by entering the Display Alarms (D A) command into
the MMI, which will cause a screen similar to Figure 44 to appear.