Operation Manual

Chapter 6
Structured cabling testing
62
Illustration 6.9. NEXT, ACR-F (ELFEXT) and Power Sum
The NEXT test determines interfering effects (crosstalk) of a transmitting wire pair on the
adjacent wire pair in the same cable. NEXT is measured on Display handset (DH) and Remote
handset (RH).
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2
3
6
4
5
7
8
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1
3
6
4
5
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8
Effect of
Adjacent Pair
 FEXT test and NEXT measurement are similar; the only difference is that in FEXT test the
transmissions emanate from Remote handset (RH) and that crosstalk is determined at
Display handset (DH).
 NEXT measurements are performed on each cable end and for all wire pair combinations
(pair 1-2 to 3-6 etc.). Thus, a total of 12 measurements is performed.
 ACR-F (ELFEXT) measurements take place with the Display handset (DH) and the Remote
handset (RH) on both cable ends and for all possible wire pair combinations (1-2 to 3-6,
3-6 to 1-2, 1-2 etc.). This results in a total of 12 measurements.
6.10. Power Sum NEXT, Power Sum ACR-F (ELFEXT)
Power Sum-Tests determine the crosstalk effects of three transmitting wire pairs on the
fourth wire pair in the same cable.