| Several factors can contribute to near-end crosstalk. The
most common cause is crossed pairs. As mentioned earlier, you can detect these with the
wire map feature of a cable tester. Near-end crosstalk can also be caused by twisted pairs
that have become untwisted after being attached to cross-connect devices (e.g. patch
panels) that have patch cords that are untwisted, or by cables that have been pulled too
tightly around sharp corners, causing pairs to change position inside the cable jacket. If you measure near-end crosstalk, you should do a visual check of
the horizontal cabling, in order to rule out any of these possibilities. If you find
nothing, then split pairs have most likely caused the problem. A cable tester measures for
near-end crosstalk by measuring a series of frequencies up to 100 MHz. High numbers are
good; low numbers indicate problems on the network.
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