Chapter 7
Testing Twisted Pairs
Page 7-31
IMPEDANCE
Impedance is an inherent characteristic of the cable, and is a
measure of resistance to AC current flow (high frequency signals)
by a long cable. High speed data transmission systems will not
perform well unless cabling having the correct impedance is
installed. Impedance is not the same as Resistance (see Resistance
below).
Do not mix cables with different impedances. Locations of any
significant impedance changes can be found by performing the
Length test on a segment. Refer to the previous section on Length
for more information on finding impedance changes or anomalies.
Test Results
Possible Solutions
Impedance is
out of
specification
Check specifications of cable. Compare
expected value with measured value. Make
sure you are using the correct cable test
standard.
Impedance is
failing, but the
cable is the
correct type
Check for split pairs. Correct wiring as
necessary.
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