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SCAN-LAN VI
1. Press SPEC (F3) to view the test standard specification value.
2. Press SHIELD (F2) to view the resistance of the cable shield.
3. Press START (F1) to restart the resistance test.
6.13 Power Sum NEXT
NEXT (Near End Crosstalk) is a measure of noise coupled from one pair
to another pair in a four-pair cable.
Power Sum NEXT is a sum of the pair-to-pair NEXT coupled from all
adjacent pairs. Power Sum is specified by TIA 568A as the recommended
method for characterizing NEXT of multipair backbone cable. PS-NEXT
can be computed from the individual pair-to-pair NEXT statements.
As shown above, Power Sum NEXT is a sum of the pair-to-pair NEXT
measurements and is always greater than any pair-to-pair NEXT.
The Power Sum NEXT test uses the same test limit as pair-to-pair NEXT.
Since Power Sum NEXT is always greater than pair-to-pair NEXT, the Power
Sum NEXT test holds the cable up to a higher standard.
Emerging high-speed networks (for example, 622-Mbps ATM, Gigabit
Ethernet) are using several pairs for transmitting data. Power Sum NEXT is
an important measure of the crosstalk noise coupled from these transmitters
to the receive pair.
M
Signal measurement
Signal generators
7
8
4
5
3
6
1
2
Crosstalk
Summary of Contents for SCAN-LAN VI
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