er cable is about 1MHz. Limited data rates-The longer a signal has to travel over twisted-pair, the lower the data rate. At 30 feet (100 m), twisted-pair can carry 100Mbps, but at 3.5 miles (5.5 km), the data rate drops to 2Mbps or less. Short distances required between repeaters-More components need to be maintained, and those components are places where trouble can arise, which leads to higher long-term operational costs. High error rate-Twisted-pair is highly susceptibility to signal interference such as EMI and RFI. Although twisted-pair has been deployed widely and adapted to some new appli- cations, better media are available to meet the demands of the broadband world. Coaxial Cable The second transmission medium to be introduced was coaxial cable (often called coax), which began being deployed in telephony networks around the mid-1920s. Figure 2.2 shows the components of coax. In the center of a coaxial cable is a cop- per wire that acts as the conductor, where the information travels. The copper wire in coax is thicker than that in twisted-pair, and it is also unaffected by surrounding wires that contribute to EMI, so it can provide a higher transmission rate than twisted-pair. The center conductor is surrounded by plastic insulation, which helps filter out extraneous interference. The insulation is covered by the return path, which is usually braided-copper shielding or aluminum foil-type covering. Outer jackets form a protective covering for coax; the number and type of outer jackets depend on the intended use of the cable (e.g., whether the cable is meant to be strung in the air or underground, whether rodent protection is required). Chapter 2 Traditional Transmission Media Return Path Copper Conductor (braided-copper shielding) Outer Jackets Plastic Insulation Figure 2.2 Coaxial cable Characteristics of Coaxial Cable Coax affords a great deal more frequency spectrum than does twisted-pair. Tradi- tional coaxial cable television networks generally support 370MHz. Newer deploy- ments, such as hybrid fib