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239 H4R Ir
to that anomaly. This number will also reflect the highest anomaly count seen, as it is possible to have more than
one bad splice per circuit. This screen will report the worst (most frequently detected) anomaly.
In this example, a detection has occurred approximately 650 feet from an H4TU-C module on Loop 2 of the
HDSL4 circuit.
Figure 2. Splice Results Screen
Fast Retrain Feature
Fast Retrain is an ADTRAN proprietary feature whose intent is to minimize downtime when an intermittent non
power-related impairment (bad splice, noise burst, etc.) affects the HDSL loop and cannot be bridged.
HDSL2 and HDSL4 transceivers normally train in approximately 25 to 30 seconds. For an initial circuit turn-up,
this is not a big issue. However, once service has been established on the circuit, any large down-time will interrupt
communications on the circuit. A loss of synchronization on the F1DSL loop can cause excessive down times due
not only to the 30-second HDSL retrain time, hut also further delays due to the higher level protocols in the
network going through re-synchronization. On the older generation 1TDSL2 and F1DSL4 units, a 1-second loss of
HDSL frame synchronization would cause the data pumps to retrain. This retrain would take approximately 25
seconds during which AIS would be sent to the terminating equipment. The reception of AIS by the terminating
equipment then might trigger higher level protocol re-synchronizations.
In an effort to minimize this down time, the Fast Retrain feature has been implemented. If an impairment (bad
splice, for example) causes the F1DSL data pump to lose frame synchronization for 500 msec or longer, instead of
retraining, a fast retrain will be attempted. This abbreviated train can achieve data mode in 5 to 7 seconds. A
(UAS) in the PM data for each LOS alarm recorded.
NOTE
Fast-Retrain capable units must be installed on both ends of the HDSL4 circuit for
for any reason, then th/traditional (25-30 second) retrain will be initiated.
P
61223445L1-5D
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