36 man_digiflex_com_en_02_5.doc
3.8.6 Mode NEXT
Mode NEXT (Near End cross (X) Talk) is for measuring the cross-talk
coupling k1 between two pairs of conductors. Unwanted crosstalk coupling
occurs in particular when wires have been crossed.
The
Digiflex Com is able to pinpoint the fault precisely, so the fault can
subsequently be eliminated to the point. For instance, the device can
determine the beginning and the end of a ”split pairs” section in a longer
trunk line which is composed of a number of sections.
The point of crosstalk coupling is located as in any normal reflection test.
This mode is different, however, in that the pair which shall carry the
transmitter pulse is connected to L2 and the pair tested for crosstalk to L1.
Press key Line and use the rotary encoder to enable mode NEXT.
Fig. 11
The direction of the pulse at the beginning of the ”Split Pairs” section may
be positive or negative depending on the direction in which the wires have
been connected to the device. At the end of the ”Split-Pairs” section the
reflection is always inverted as compared with its beginning.
„Split-Pairs“section Section of line
pair 2
pair 1
L2 L1
Transmission reception
Digiflex Com
Reversed wires crosstalk
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