Páginas: 5 (1096 palabras) Publicado: 6 de junio de 2011
Cable Cruzado
Key words:
10BaseT - Unshielded Twisted Pair (UTP) - RJ45
110 Blocks - Category 5 - Level 5 - EIA 568B
Straight Through - Reversed - Cross-over
MDI, MDI-X Hub Ports

Wiring Tutorial for 10BaseT Unshielded Twisted Pair (UTP)

One of the most common and most puzzling problems a network engineer/technician may face is what is the PROPERway to make up a 10BaseT cable. Usually, to confound the learning process, someone introduces the need for a reversed or cross-over cable at the same time. What these are and how to make them is the subject of this on-line tutorial.
Selection of Cabling Category
Since the overwhelming bulk of network cabling done today uses Unshielded Twisted Pair (UTP) wiring that is what we will discuss. Theprocess begins with the selection of the proper wiring level or category. Today it is basically inexcusable to use or install anything at less than Level V or Category 5.
While technically Category 5 and Level V are not the same, they are identical in practice. Both support upto 100 megabit per second data transmission, and their physical cable assembly requirements are the same. Throughout thistutorial we will refer to them both as CAT5.
When you order CAT5 unshielded twisted pair (UTP) cable you will receive a cable containing 4 twisted pairs of wires, a total of 8 wires. The strands that constitute each wire will either be a single strand or multiple strands, usually referred to as solid or flex. Typically the solid is used to run through walls and ceilings and the flex is used to makedrop cables (the cable from the wall plate to the desktop computer) and patch cables (the cable from the patch panel to the hub). Whether the exterior portion of the cable that contains the 4 twisted pairs, the jacket, is Plenum grade or Non-plenum grade is very important, it refers to the Fire Codes, but is outside the scope of this tutorial.
Ordering Pairs
The pairs of wires in UTP cable arecolored so that you can identify the same wire at each end. Furthermore, they are usually color coded by pair so that the pairs can also be identified from end to end. Typical CAT5 UTP cables contain 4 pairs made up of a solid color and the same solid color striped onto a white background. The most common color scheme is the one that corresponds to the Electronic IndustryAssociation/Telecommunications Industry Association's Standard 568B.
The following table demonstrates the proper color scheme.
|Wire pair #1: |White/Blue |[pic] |
| |Blue | |
|Wire pair #2: |White/Orange ||
| |Orange | |
|Wire pair #3: |White/Green | |
| |Green | |
|Wire pair #4:|White/Brown | |
| |Brown | |

The cable connectors and jacks that are most commonly used with CAT5 UTP cables are RJ45. The RJ simply means Registered Jack and the 45 designation specifies the pin numbering scheme. The connector is attachedto the cable and the jack is the device that the connector plugs into, whether it is in the wall, the network interface card in the computer, or the hub.
Now that we are ready to insert the cable into the RJ45 plug the wire number and color sequence becomes more complicated.
The IEEE Specification for Ethernet 10BaseT requires that two twisted pairs be used and that one pair is connected to...
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