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SCAN-LAN VI
The twisting of pairs of wires is essential to minimizing crosstalk effects
from pair to pair. The amount of twisting is a key difference between high-
performance Category 5 cable and lesser-rated cable, such as Category 3.
A common problem with installing Category 5 cable is maintaining the
wire twist when terminating the cable. The EIA/TIA 568-A specification
states the twists must be maintained to within 0.5 inch (1.27 cm) of the
termination for Category 5 and within 1 inch (2.5 cm) for Category 4. If
the twists are not maintained, NEXT will increase.
NEXT also varies with the frequency of the signal, but the relationship is
not linear. Therefore, because the NEXT of a cable is within a certain
specification at lower frequencies does not guarantee the NEXT will be
within the same specifications at a higher frequency. Figure 8-8 illustrates
an example of how NEXT varies with signal frequency.
Figure 8-8. Typical Relationship of NEXT and Frequency.
Freq.
NEXT
(dB)
Summary of Contents for SCAN-LAN VI
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