Fluke Series II user manual Reversed Pair, Crossed Pair, Split Pair, OneTouch Series, Users Manual

OneTouch Series II

Users Manual

Reversed Pair

A cable pair is reversed when two individual wires of a pair are reversed from end-to-end, as shown in Figure 4-3.

A reversed pair is not necessarily a catastrophic failure. Some 10BASE-T adapter cards and Hubs can sense the reversed polarity and continue to operate. It is always a good idea, however, to fix this problem when found.

1	2
2	1

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Figure 4-3. Reversed Pair

Crossed Pair

A pair is crossed when a wire pair is mapped to a different set of connector pins on the other end of the cable. Figure 4-4 shows an example of a crossed pair.

Sometimes pairs are crossed intentionally. A cable with a 1-2 to 3-6 cross is commonly known as a crossover cable, which is used for cascading Hubs together that do not have uplink ports.

Special crossed-pair patch cords are useful when working with non-standard cabling systems.

1	3
2	6
3	1
6	2

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Figure 4-4. Crossed Pair

Split Pair

A split pair is different from a crossed pair in that the pin- to-pin wiring is correct but the wire pairing is incorrect. That is, a “connector” pair is made up of two wires from a “cable” pair. Figure 4-5 shows an example of a split pair.

A split pair is much more susceptible to noise because the two wires in the “pair” are not twisted around each other. Split pairs can be especially difficult to find because the symptoms depend upon the particular wires involved, the cable length, and ambient noise.

4-6