PC Hardware A Beginner’s Guide

Twisted Pair Wire

Unshielded twisted pair (UTP) or 10BaseT cabling, shown in Figure 20-4, is the cable type

most commonly used on LANs. Of the three most popular cabling media choices, UTP

provides the most installation flexibility and ease of maintenance.

The Electronics Industries Association and the Telecommunications Industries

Association (EIA/TIA) defines UTP cable in five categories, or “cats” as they are commonly

referred to (as inCat 3orCat 5). The cables defined in Categories 1 and 2 are not used in

networking, but here is a description of the three that are.

 Category 3 A 4-pair (8-wire) cable that supports bandwidth up to 10

Mbps—the minimum standard for 10BaseT networks

 Category 4 A 4-pair cable commonly used in 16 Mbps token ring networks

 Category 5 A 4-pair cable with bandwidth up to 100 Mbps used for

100BaseT networks

The RJ-45 connector used with twisted pair cable is very much like the one used on

your telephone. Figure 20-5 shows an RJ-45 connector.

The other type of twisted pair is shielded twisted pair (STP) cable. It is easy to tell

shielded cable from unshielded cable: STP has each wire pair wrapped with a grounded

copper or foil wrapper (see Figure 20-6) that helps to shield it from interference. The

shielding makes STP more expensive than UTP, but it does support higher transmission

speeds and carry signals over longer distances.

Fiber Optic Cable

Fiber optic cable carries data in the form of modulated pulses of light. To simulate how

data travels through a fiber optic cable, you would need to turn a flashlight on and off

about two million times in one second. The core of fiber optic cable consists of two (or

(^518) PC Hardware: A Beginner’s Guide
Figure 20-4. Unshielded twisted pair wire (UTP)