Nortel Networks 1000 - Manual (Page 300)

300 NT5D33 and NT5D34 Lineside E1 Interface cards
A loss of signal condition is declared if a full frame (255 bits) of
consecutive zeros has been detected at the receive inputs. If this condition
occurs, the E1 link automatically attempts to resynchronize with the
far-end. If this condition lasts for more than two seconds, a level 2 alarm is
declared, and silence is sent on all receive timeslots. The alarm is cleared
if, after two seconds, neither a loss of signal, out-of-frame condition, or
blue alarm condition occurs.
If a repeating device loses signal, it immediately begins sending an
unframed signal of all ones to the far-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 is declared,
and silence is sent on all receive timeslots. The alarm is cleared if, after
two seconds, neither a loss of signal, out-of-frame condition, or blue alarm
condition occurs.
Alarm Disable
The Alarm Disable (A D) command disables the external alarm
contacts. When this command is typed, the MMI displays the message
Alarms Disabled and the MAINT LED lights. In this mode, no yellow
alarms are sent and the LEI does not enter line processing mode. Alarm
messages are sent on the MMI terminal and the LED continues 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 displays 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 clears all activity initiated by an alarm:
the external alarm hardware is deactivated (the contact normally open is
reopened), the LED goes out, an entry is made in the alarm log of the date
and time the alarm was cleared, and line processing ceases (for alarm
level 2 only). When this command is typed, MMI displays the message
Alarm acknowledged. If the alarm condition still exists, an alarm is
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 causes a screen similar to Figure 71 "Display Alarm (D A)
screen" (page 301) to appear.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.