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CHAPTER 8: Testing Twisted-Pair Cable
Although the SCAN-LAN VI uses TDR to measure length, Resistance can
also be used as a method to measure the length of a cable if you know the
rated resistance (ohms per foot or meter) of the cable. Resistance of a
cable is usually rated on a per-1000-feet or per-1-km basis.
The table below discusses some common resistance problems and
solutions.
Test Results
Possible Solutions
Resistance is
Compare measured value with expected value. Troubleshooting
out of
resistance should be done the same way as troubleshooting attenuation.
specification
See the section on Attenuation.
All termination points should be checked. Perform a Length test to
check for anomalies.
8.3 Testing Tips
8.3.1 S
ELECTING
P
ERFORMANCE
M
ODULE
(PM)
AND
C
ABLE
S
PECIFICATION
1. Select and install the appropriate Performance Module (PM) for
the type of cable under test.
2. Select the correct cable test standard you wish to test to.
If you select one of the EIA/TIA Category 3, 4, or 5 Basic Link test
standards, the accuracy (Level I or Level II) will be determined by the
Performance Module you use.
Level-II measurement accuracy can only be assured with the use of the
8-position modular plug PM. See
Appendix A, Test Standards,
for more
explanation of the EIA/TIA TSB-67 Link Performance Standard.
8.3.2 C
ONNECTING THE
S
EGMENT
U
NDER
T
EST
CAUTION
If you see or hear an OVERVOLTAGE WARNING when connecting to a
patch panel or wall plate, disconnect the unit immediately. You may
have connected to a telephone line carrying ringing voltages.
The SCAN-LAN VI is designed with special protection circuitry that
allows it to withstand ringing voltages with no damage. However, it is
best to avoid connecting the SCAN-LAN VI to live circuits.
Summary of Contents for SCAN-LAN VI
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