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CHAPTER 8: Testing Twisted-Pair Cable
8.2.2 N
EAR
-E
ND
C
ROSSTALK
(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 8-6).
Figure 8-6. 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 8-7).
Figure 8-7. NEXT Measurement.
1
2
3
4
M
Crosstalk
Signal measurement
Signal generator
X
T
X
R
X
R
X
T
crosstalk
Summary of Contents for SCAN-LAN VI
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