LanTEK III 161809 Iss 2
User Manual Page62
6.8.1 Resistance Test Error
All four wire pairs of a transmission line within the network should have approximately the
same resistance. If the resistance value of a wire pair exceeds the limit, the test is
considered failed.
6.9 NEXT, ACR-F (ELFEXT) and Power Sum
In an Autotest, crosstalk at the near and far end of the cable is measured with NEXT (Near
End Cross Talk) and ACR-F (ELFEXT) tests. High crosstalk levels can result in frequent
recurrences, damage to data and other interferences that impair transmission rate.
Fig. 75 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).
1
2
3
6
4
5
7
8
2
1
6
3
5
4
8
7
Fig. 76 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
To Next Page
Loading...
