Nortel Networks 553-3001-211 manual Alarm Disable, Alarm Enable

NT5D11 and NT5D14 Lineside T1 Interface cards Page 225 of 894

Descriptions of the excessive bit error rate and frame slip errors conditions can be found in “Configuring parameters” on page 220. Bit errors may activate either a level 1 or level 2 alarm. The remaining conditions, when detected, will always cause the system to activate a level 2 alarm.

An out of frame condition will be declared if two out of four frame bits are in error. If this condition occurs, the hardware will immediately attempt to reframe. During the reframe time, the T1 link will be declared out of frame, and silence will be 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 will automatically attempt to resynchronize with the distant end. If this condition lasts 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.

If a repeating device loses signal, it immediately begins sending an unframed all 1’s signal 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 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, the MMI will display the message “Alarms Disabled” and the MAINT LED will light. In this mode, no yellow alarms are sent and the lineside T1 card will not enter line processing mode. Alarm messages will still be sent to the MMI terminal and the LED light will continue 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 will display the message “Alarms Enabled.” In this

Circuit Card Description and Installation