User's Manual

Chapter 18 Maintenance and Troubleshooting
Resolving problems
SmartClass TPS User’s Guide
May 2014 22035456, Rev 001 159
Resolution
Use a known good loop to determine capacitance, then run the opens again to determine the length
of the bridge tap or location of the fault. Verify with a tester that has TDR capability.
Measure multiple vacant pairs by attaching one lead to Ground (E) and using the other to the Tip
(A) of each vacant conductor. (Battery should be removed) Compare the distance for each for
consistency.
Opens/Capacitance: < 3% difference between Tip (A) and Ring (B) values indicate an acceptably
balanced loop. Anything greater indicates an unbalanced line or open fault, which inhibit digital
signals.
You can also compare the distance from the Opens measurement to a resistive distance measure-
ment, and determine the presence of a bridged tap by the difference in the distances.
Issue
The balance measurement is 50 dB.
Resolution
The pair quality is too low as it should mitigate 60 dB. The balance result should be >60 dB.
Anything less indicates electrical differences between Tip (A) and Ring (B) that can lead to noise
and other signal problems.
This would indicate some imbalance in the quality of each lead and reduced noise immunity.The
more each lead is electrically identical (capacitance, inductance, impedance), the better the pair will
resist induced noise. If they do not cancel induced noise equally, the difference is realized as
unwanted current, or metallic or mutual noise. If the imbalance of the leads is too great, the
customer would hear noise.
Issue
The POTS service test is fine but the DSL signal cannot be detected at the NID. The test set indi-
cates 2 load coils on a 15 kft loop.
Resolution
Load coils block high frequency signals such as DSL and they must be removed for digital circuits.
In a normal loading scheme, the first one will be 3 kft from the CO and the second will be 9 kft from
the CO. Use a tester that has TDR capability to verify the location of the loads. Loads are used to
improve POTS over long loops. On most loops 18 kft or longer, load coils are required to ensure
voice quality. Load coils must be evenly spaced starting at 3 kft from the CO and placed at 6 kft
intervals thereafter, with at least 2,000 feet between the last load coil and the customer premises.