Autotest
Autotest Results for Twisted Pair Cable
3
3-13
NEXT Test
The NEXT test measures the crosstalk between cable pairs at the near end of the
cable. This crosstalk value is expressed as the difference in amplitude (in dB)
between the test signal and the crosstalk signal. NEXT is measured from both ends
of the cable over a frequency range defined by the selected test standard.
The first NEXT screen displays the cable pairs tested, the worst-case NEXT
margin, and the test result for each set of pairs.
To see detailed results for the cable pairs, use D U to highlight the pairs; then
press @ View Result. Table 3-4 describes the items on the NEXT results
screen.
Table 3-3. Items on the NEXT Results Screen
Item Description
Pairs
The cable pairs relevant to the results.
Result
The overall result for the NEXT test. A PASS result indicates that the NEXT
between the cable pairs was higher than the specified NEXT for the selected
test standard. A FAIL result indicates that the NEXT was lower than
specifications.
NEXT
The worst margin and worst NEXT. The worst margin is the NEXT value that is
closest to falling below specifications, or the value that exceeds specifications
by the greatest amount. The worst NEXT is the lowest NEXT value measured.
Frequency
The frequencies where the worst margin and worst NEXT values occurred.
Limit
The lowest NEXT values acceptable for the frequencies above.
Margin
The differences between the NEXT values and the limits. A positive number
means that the measured NEXT value is higher than the limit (PASS). A
negative number means that the NEXT is lower than the limit (FAIL).
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