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Appendix C: Examples of UTP Cable Faults
Opens in cable pairs generate errors in both in skew tests and in
wire map tests. The following example shows a 200-foot cable
with a break in the middle on Pair 78. The following is the fi rst
screen to show a problem.
Figure C-5. Bad cable: Open.
NOTE: There are two problems shown. The skew (difference
in delay between pairs) is much greater than 50 ns.
Another problem is that the cable length is only shown as
98 feet. Press details and continue the tests. All will
become clear when cable map is displayed. Here is a
sample cable map.
Figure C-6. Bad cable: Wire map of open pair.
The sample map clearly shows the problem. There is an open at
98 feet on Pair 78. The skew was so large because the timing
pulses travel about 200 feet on Pairs 12, 36, and 45, but only
travel 98 feet on Pair 78. As always, retest cable after repairs are
made.
