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CHAPTER 6: Cable Test Descriptions
Power Sum NEXT is tested only during an Autotest. It is included in Autotest
for the enhanced Category 5 and Class D cable test standards (for example,
CAT5 Plus BasicLink, ISO Plus Class D).
The graph below shows the computed PS-NEXT for a typical Category 5 link,
compared to a composite curve representing the greatest (i.e. closest to the
TSB-67 NEXT limit) pair-to-pair NEXT values for the same link. As seen from this
example, the PS-NEXT values are always worse than the greatest pair-to-pair NEXT
values. In fact, PS-NEXT for four-pair cabling can be as much as 4.77 dB worse
than the greatest pair-to-pair NEXT measurement. A link that easily passes TSB-67
Category 5 pair-to-pair NEXT requirements might therefore fail if PS-NEXT is used
as the measure.
NEXT Limit Line.
Several manufacturers of enhanced-performance CAT 5 cables and connectors
specify PS-NEXT as a measure of product performance. Because PS-NEXT is a
more stringent NEXT characterization method, components that are specified
and tested to meet Power Sum are more likely to deliver optimum performance,
even beyond TIA568A defined CAT 5 requirements.
6.13.1 V
IEWING
P
OWER
S
UM
NEXT R
ESULTS
At the conclusion of Autotest, press VIEW (F3) to view the test results
and press the arrow keys to display the Power Sum NEXT results.
The Power Sum NEXT of each pair combination is compared to the selected
cable test standard and pass or fail is indicated.
Summary of Contents for SCAN-LAN VI
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