 Reach VDSL2 (discussed in Chapter 12, "Broadband Access Alternatives"), which is based on twisted copper pair but can support up to 100Mbps, but over a maximum loop length of only 330 feet (100 m). New developments continue to allow more efficient use of twisted-pair and enable the higher data rates that are needed for Internet access and Web surfing, but each of these new solutions specifies a shorter distance over which the twisted-pair is used, and more sophisticated modulation and error control techniques are used as well. Another characteristic of twisted-pair is that it requires short distances between repeaters. Again, this means that more components need to be maintained and there are more points where trouble can arise, which leads to higher costs in terms of long-term operation. Twisted-pair is also highly susceptible to interference and distortion, including electromagnetic interference (EMI), radio frequency interference (RFI), and the effects of moisture and corrosion. Therefore, the age and health of twisted-pair cable are important factors. The greatest use of twisted-pair in the future is likely to be in enterprise premises, for desktop wiring. Eventually, enterprise premises will migrate to fiber and forms of wireless, but in the near future, they will continue to use twisted-pair internally. Categories of Twisted-Pair There are two types of twisted-pair: UTP and STP. In STP, a metallic shield around the wire pairs minimizes the impact of outside interference. Most implementations today use UTP. Chapter 2 Traditional Transmission Media Twisted-pair is divided into categories that specify the maximum data rate pos- sible. In general, the cable category term refers to ANSI/TIA/EIA 568-A: Commer- cial Building Telecommunications Cabling Standards. The purpose of EIA/TIA 568-A was to create a multiproduct, multivendor standard for connectivity. Other standards bodies-including the ISO/IEC, NEMA, and ICEA-are also working on specifying Category 6 and above cable. The following are the cable types spe