LANTEK User Manual - Ideal Industries

Chapter 3
Structured Cable Field Calibration and Testing
NEXT, ELFEXT, and Power Sum Tests
The NEXT (Near End Crosstalk) and ELFEXT (Equal Level Far-End Crosstalk) tests
measure crosstalk at the near and far ends of the cable in one Autotest. High levels of
crosstalk can cause excessive retransmissions, data corruption, and other problems
that slow the network system.
NEXT, FEXT, and ELFEXT
Figure 3-13: NEXT and ELFEXT Test Screens
The NEXT test measures cross-talk from a transmitting pair to an adjacent pair in the
same cable sheath. NEXT is measured at the DH and RH.
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Effect of
Adjacent Pair
‣ The FEXT test is similar to the NEXT test except that the traffic is generated at
the RH and crosstalk is measured at the DH.
‣ NEXT measurements are made at each end of the cable for all pair combinations
(pair 1-2 vs. 3-6, etc.), yielding a total of twelve measurements.
‣ ELFEXT measurements are made with the DH and RH for all possible pair
combinations (1-2 vs. 3-6, 3-6 vs. 1-2, 1-2 etc.) at both ends yielding a total of
twenty-four measurements.
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