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Page 290 of 894 NT5D33 and NT5D34 Lineside E1 Interface cards
553-3001-211 Standard 2.00 September 2004
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 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 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 will cause a screen similar to Figure 50 on page 291 to appear.