Nortel Networks Circuit Card User Manual

 NT5D33 and NT5D34 Lineside E1 Interface cards

The MMI monitors the E1 link according to parameters established through 
the Set Alarm command for the following conditions:

•

Excessive bit error rate

•

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 
are found in “Configuring parameters” on page 290. Bit errors activate either 
a level 1 or level 2 alarm. The remaining conditions, when detected, always 
cause the system to activate a level 2 alarm.

An out-of-frame condition will be declared if 3 consecutive frame bits are in 
error. If this condition occurs, the hardware immediately attempts to reframe. 
During the reframe time, the E1 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 (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