Chapter 7
Testing Twisted Pairs
Page 7-9
NEAR-END CROSSTALK (NEXT)
When a signal is transmitted onto one of the pairs, an
electromagnetic field is created around the wires that couples the
transmitted signal into adjacent pairs. This coupled signal is
referred to as Crosstalk. Crosstalk is similar to the problem that
occurs in a telephone when you hear another conversation on your
line.
If crosstalk is severe enough, the transmitted signal can interfere
with the received signal on another wire pair (see Figure 7-6).
X
T
X
R
X
R
X
T
crosstalk
Figure 7-6. Crosstalk Between Stations
Because crosstalk is measured at the same end of the cable as the
signal source, the term Near-End Crosstalk (NEXT) is used to
describe this measurement (refer to Figure 7-7).
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