Key words:
        10BaseT - Unshielded Twisted Pair (UTP) - RJ45
        110 Blocks - Category 5 - Level 5 - EIA 568B
        Straight Through - Reversed - Cross-over 

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 PROPER way 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. The process 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 this tutorial 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 make drop 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 are colored 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 Industry Association/Telecommunications Industry Association's Standard 568B.

The following table demonstrates the proper color scheme.

Wire pair #1:	White/Blue Blue
Wire pair #2:	White/Orange Orange
Wire pair #3:	White/Green Green
Wire pair #4:	White/Brown Brown

Connectors

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 attached to 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.

	REMEMBER To hold the RJ45 connector with the 'clip' on the bottom. To have to the 'opening' (where you insert the cable) facing you.
CAT5 Standard Patch Cord		CAT5 Cross-over Cable

Straight-Through vs. Cross-Over

In general, the patch cords that you use with your Ethernet connections are "straight-through", which means that pin 1 of the plug on one end is connected to pin 1 of the plug on the other end. In this particular case it is not then important to wire them as above. Pin 1 is Pin 1 etc etc. However for the sake of uniformity it may be best to wire your cables with the same colour sequence. Cross-Over cables are  "crossed" end to end  data cables aren't. If you have a network hub that has an uplink port on it then you do not need to make (or purchase a cross-over cable). Just switch the port on the hub to the 'uplink' mode. If your hub does not have an 'uplink' port on it then the only way to cascade another hub or attach a cable modem is to use a cross-over cable. It helps for future reference to mark or attach a tag to the cross-over cable so that you do not attempt to use it as a 'normal' patch lead at some time in the future.

REMEMBER To hold the RJ45 connector with the 'clip' on the bottom. To have to the 'opening' (where you insert the cable) facing you.