JDS Uniphase SC-ADSL-A, Руководство пользователя

Страница: 71 / 90

Chapter 7 Interpreting Test Results
Copper results
SmartClass ADSL/Copper Tester User’s Guide 57
Opens/Capacitance: < 3% difference between tip and ring values indicate an
acceptably balanced loop. Anything greater indicates an unbalanced line or
open fault, which inhibit digital signals.
Table 26 describes the opens/capacitance result.
DC current
You measure DC current to verify if enough current is present to operate equip-
ment including the phone or caller ID boxes.
DC current on tip to ring should be
≥
23 mA at the NID. Anything less will not
allow for differences in temperature and phone equipment will not operate
during extremes.
Table 27 describes the DC current result.
Longitudinal balance
You measure longitudinal balance to:
– measure the quality of the pair: a measurement of the degree to which the
tip lead is electrically the same as the ring lead.
The more each lead is electrically identical (capacitance, inductance, imped-
ance), the better the pair will resist induced noise.
The balance result should be >60 dB. Anything less indicates electrical differ-
ences between tip and ring that can lead to noise and other signal problems.
Table 28 describes the DC current result.
Load coil
You check for load coils to ensure there are no load coils present on a digital
line (such as ADSL or ISDN). Load coil detection and elimination is essential
in the installation of an xDSL circuit
Table 26 Opens/Capacitance result specifications
Range (feet)
Resolution
(feet)
Range (meters)
Resolution
(meters) Range
(capacitance) Accuracy (applies to
capacitance only)
0 to 2,999 1 foot 0 to 999 0.1 meter 0 to 44.9 nF 2.5% ± 45 pF
3000 to 66000 1 foot 1,000 to 20,000 0.1 meter 45 nF to 1.04 µF 2.5%
Table 27 DC current result specifications
Range Resolution Accuracy
0 to 110 ma 1ma 2% ± 1ma
Table 28 Balance result specifications
Range Resolution Accuracy
35 to70 dB 1 dB 2 dB