Summary

Chapter 8: Fundamental Networks 27Category RatingUTP comes in several categories that are based on two factors:■■The number of wires in the cableThe number of twists in those wiresCategory 3 is the wiring used for telephone systems and Ethernet LAN at 10 Mbps.Category 3 has four pairs of wires.Category 5 and Category 5e have four pairs of wires with a transmission rate of 100 Mbps.Category 5 and Category 5e are the most common network cables used. Category 5e hasmore twists per foot than Category 5 wiring. These extra twists further prevent interferencefrom outside sources and the other wires within the cable.Some Category 6 cables use a plastic divider to separate the pairs of wires, which preventsinterference. The pairs also have more twists than Category 5e cable.Coaxial CableCoaxial cable is a copper-cored cable surrounded by a heavy shielding, as shown in Figure8-17. Coaxial cable is used to connect the computers to the rest of the network. Coaxialcable uses BNC connectors, sometimes called “British Naval Connectors” or “BayonetNeill-Concelman” connectors, at the ends of the cables to make the connection. Severaltypes of coaxial cable exist:■ Thicknet (10BASE5) is coaxial cable that was used in networks and operated at 10Mbps, with a maximum length of 500 meters.■ Thinnet (10BASE2) is coaxial cable that was used in networks and operated at 10Mbps, with a maximum length of 185 meters.■■RG-59 is most commonly used for cable television in the U.S.RG-6 is higher-quality cable than RG-59, with more bandwidth and less susceptibilityto interference.Fiber-Optic CableAn optical fiber is a glass or plastic conductor that transmits information using light. Fiberopticcable, shown in Figure 8-18, has one or more optical fibers enclosed in a sheath orjacket. Because it is made of glass, fiber-optic cable is not affected by EMI or RFI. All signalsare converted to light pulses to enter the cable and are converted back into electricalsignals when they leave it. This means that fiber-optic cable can deliver signals that areclearer, that can go farther, and that have greater bandwidth than cable made of copper orother metals.