Nortel Meridian 1 Option 11C Manual page 71

DTI Maintenance Page 71 of 126
Clock synchronization can be either tracking, on the primary or secondary
reference clock, or free run (non-tracking). In LD 73 (prompts PREF and
SREF), the 2.0 Mb DTI which supports the active clock controller is defined
as the primary clock reference. Another 2.0 Mb DTI may be defined as the
secondary clock reference. The clock controller synchronizes from the
primary or secondary's incoming pulse stream. The clock controller in turn
supplies clocking to all the other 2.0 Mb DTI cards.
2.0 Mb DTI hardware detects frame slips in tracking and free run modes. For
tracking mode, running the midnight routines prints the number of overflows
and clears the counter. For free run mode, running the midnight routines
prints the number of slips and clears the counters.
Frame Alignment Problem (FAP) A Frame Alignment Problem is counted
when a bit error occurs within the framing pattern.
Group 2
Loss of Frame Alignment Signal (LFAS) A Loss of Frame Alignment
condition can be defined as: frame alignment is lost on three consecutive
frame alignment errors. This condition may occur as a result of the far end of
the E1 span going completely out of service.(due to a power interruption, for
example) or any other reason resulting in losing the incoming pulse stream.
The B3 alarm is sent to the far end after the persistence time expires.
Loss of frame alignment thresholds 2.0 Mb DTI hardware detects out of
frame conditions. Running the midnight routines prints the number of
occurrences when frame alignment was lost and clears the counters.
Alarm Indication Signal (AIS) AIS is defined as receiving all ones without
framing. The detection algorithm for AIS is two or less zeros per two frames.
This allows detection of AIS in the presence of a 10E-3 error rate, without
mistaking framed all 1s for AIS.
When the AIS is detected, the prompt maintenance alarm indication
associated with LFAS and excessive bit error rates should be inhibited. B3
alarm is sent to the far end after persistence time expires
Alarm Indication Signal 64 Kilobit (AIS64) There are also specific AIS
requirements for CNET (France). The first requirement relates to the
transmission of AIS in TS16. In that case, all 1 should be transmitted in the
event abcd signaling cannot be supported.
Option 11C 2.0 Mb DTI/PRI