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239 H4R Installation and Maintenance Practice
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.
Circuit ID:HTSVALHDSL4
* Note: Chronic Circuit Results are only valid after all other circuit
* qualification tests have been performed and failed to show a trouble !! *
Splice Detector Version 1 Result Definitions:
---------------------------------------------
NTF
- No Trouble Found yet.
LOS
- Unit not in sync.
Number - Distance from Reference point (in ft.) of suspect splice.
Reference
Point
---------
H4TUC
H4TUR
H4RU1 NET
H4RU1 CST
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 HDSL loop can cause excessive down times due
not only to the 30-second HDSL retrain time, but also further delays due to the higher level protocols in the
network going through re-synchronization. On the older generation HDSL2 and HDSL4 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 HDSL 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
successful fast retrain should be evident by watching the Span Status screen and by reduced unavailable seconds
(UAS) in the PM data for each LOS alarm recorded.
Fast-Retrain capable units must be installed on both ends of the HDSL4 circuit for
this feature to function properly. Also, if there is a failure of a fast retrain attempt,
for any reason, then the traditional (25-30 second) retrain will be initiated.
61223445L1-5D
Press ESC to return to previous menu
Splice Detection Results
Loop 1
Loop 2
----------
----------
NTF
650
NTF
NTF
NTF
NTF
NTF
NTF
Figure 2. Splice Results Screen
Version
Number
-------
01
01
01
01
NOTE
06/17/04 07:32:04
*
Result Shown
for date
MM/DD/YY
--------
06/17/04
(B)Back
Description
3
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