Cable Choices

Twisted Pair 10BaseT or 100BaseT

I prefer Twisted Pair cabling for most small, indoor networks. I will use the terms 10BaseT, Twisted Pair and TP interchangably as they all refer to the same thing in the context with which I'm using them. It is very easy to work with, and makes adding or removing nodes pretty quick and painless. There are a few questions that seem to be asked a lot by people using Twisted Pair cabling for the first time. I try to answer these below:

What is Twisted Pair cabling?

TP cabling is a cable made up of four pairs of insulated copper wires. Unshielded TP( UTP ) is the most commonly used in smaller networks, and is rated as Category Three ( CAT3 ) or Category Five ( CAT5 ). The difference between the ratings is the number of twists per inch. Higher is better. CAT5 is probably the most commonly seen. RJ45 connectors are fitted on each end of the cable. They resemble a normal telephone plug ( RJ11 ) with the exception of eight pins rather than four.

Can I use regular phone line instead of UTP?

In a word, NO. While it is true that Ethernet only uses two pairs of wires, it is not advisable to use regular telephone cabling. It is possible that it may work but remember, UTP is specifically designed to be used with networks. It is manufactured with set tolerances for impedance, twists per inch, etc. You are better off to do it right the first time. Having to re-cable after lost data and intermittent problems have taken more of your time than you care to admit is not a good thing.

Do I need a hub?

It depends. If you plan to have more than two computers in your network then, yes, you will need a hub. If you are on a 100BaseT network you will need a hub capable of 100Mbps. If you are only going to be using two machines then, no, you don't need a hub. But, you will need a crossover cable.

What is a crossover cable?

I should first explain the wiring of a staight-through cable. (The wiring for a straight through and a crossover cable are the same for 10BaseT or 100BaseT. There is less forgiveness and less room for error if you are making cables for 100BaseT.). If you were holding an RJ45 connector in your hand with the flat side up and the plastic tang down, pin one would be the farthest pin to the left. The pins are then numbered sequentially with pin eight being the farthest to the right. Only four of the eight wires are used by a 10BaseT network. Pins 1 and 2 are used and pins 3 and 6 are used. The wiring should be done in pairs, Pins 1 and 2 should be from one twisted pair and Pins 3 and 6 should be from one twisted pair. The pairs should remain twisted as close as possible to the connectors. A straight through cable is illustrated in the following table.

Straight-Through Cable

Point A	Function	Wire Color	Point B
Pin 1	TD+	White/Orange	Pin 1
Pin 2	TD-	Orange	Pin 2
Pin 3	RD+	White/Green	Pin 3
Pin 4	Not Used	Blue	Pin 4
Pin 5	Not Used	White/Blue	Pin 5
Pin 6	RD-	Green	Pin 6
Pin 7	Not Used	White/Brown	Pin 7
Pin 8	Not Used	Brown	Pin 8

To make a crossover cable ( also refered to as a reverse cable or null-modem cable ), pins 1 and 3 and pins 2 and 6 should be switched on one end as shown in the following table:

Crossover Cable

Point A	Function	Wire Color	Point B	Function
Pin 1	TD+	White/Orange	Pin 3	RD+
Pin 2	TD-	Orange	Pin 6	RD-
Pin 3	RD+	White/Green	Pin 1	TD+
Pin 4	Not Used	Blue	Pin 4	Not Used
Pin 5	Not Used	White/Blue	Pin 5	Not Used
Pin 6	RD-	Green	Pin 2	TD-
Pin 7	Not Used	White/Brown	Pin 7	Not Used
Pin 8	Not Used	Brown	Pin 8	Not Used

What is the maximum cable length using TP?

The maximum segment distance, without using a repeater, for Twisted Pair is 100 meters.