Nortel Networks 311

246 NT5D11 and NT5D14 Lineside T1 Interface cards

•Frame slip errors

•Out of frame condition

•Loss of signal condition

•Blue alarm (AIS) condition

Descriptions of the excessive bit error rate and frame slip errors conditions

can be found in "Conﬁguring parameters" (page 235). Bit errors may

activate either a level1 or level 2 alarm. The remaining conditions, when

detected, always cause the system to activate a level 2 alarm.

An out of frame condition is declared if two out of four frame bits are in error.

If this condition occurs, the hardware immediately attempts to reframe.

During the reframe time, the T1 link is declared out of frame and silence is

sent on all receive timeslots.

A loss of signal condition is declared if a full frame (192 bits) of consecutive

zeros has been detected at the receive inputs. If this condition occurs, the

T1 link automatically attempts to resynchronize with the distant end. If this

condition lasts for more than two seconds, a level2 alar m 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, nor blue alarm

condition occurs.

If a repeating device loses signal, it immediately begins sending an

unframed all 1’s signal to the far-end toindicate an alar m 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, nor 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 turns on. In this mode, no yellow alarms are

sent and the Lineside T1 card doesnot enter line processing mode. Alarm

messages are still sent to the MMI terminal and the LED light continues

to indicate alarm conditions.

Alarm Enable

The Alarm Enable (A E) command set does the opposite of the Alarm

Disable command set. It enables the external alarm contacts. When this

command set is typed in, the MMI displays the message "Alarms Enabled."

In this mode, yellow alarms can be sent and the Lineside T1 card can enter

line processing mode.

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 01.04 Standard

Release 5.0 23 May 2008