Cable Tests
59
Crosstalk Crosstalk is detected when there is electromagnetic coupling
between pairs. Coupling could be inductive / capacitive if
there is a twisting defect in the pair or it can be resistive if
there is a problem with the dielectric medium between con-
ductors. Some wiring faults between the cable and the con-
nector may cause crosstalk too.
The crosstalk is indicated in the equipment as a collection of
numbers separated by ‘-’ for each MDI. For example if MDI-0
and MDI-3 are coupled, then the crosstalk result for MDI-0
and MDI-3 will be 0-3.
Distance (m.) The Distance (m.) result displays the distance to an open
circuit / short circuit fault in with an accuracy of ±1 m. If there
is no fault, no distance is displayed. The maximum range of
the distance test is 100 m.
To measure the cable length, just leave the far end
disconnected and run the test. xGenius will detect an open
circuit in all MDIs and the Distance (m.) results displays the
cable length.
Crossover Displays whether the local MDI-n is in straight (MDI) or
crossover (MDIX) status.
Note that Crossover is not really a cable result, it is the local
port MDI/MDIX status. This status may be random and
depends on the cable and the remote port. Therefore this
result may be modified if the cable is disconnected and
reconnected again.
Polarity Polarity could be positive or negative for each MDI-n. A
negative polarity indicates that the pair connects pins of
inverted polarity in the local and remote end. Positive polarity
means that local and remote pins have the same assigned
polarity.
Skew (ns.) Relative propagation delay, expressed in nanoseconds,
experienced by the pair associated to the MDI and compared
to the MDI that has minimum propagation delay. That means
that the Skew (ns.) is always zero for at least one MDI.
The skew result is not measured for 10 Mb/s and 100 Mb/s
interfaces.
Table 3.4: Cable test results
Result Description
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