ent use of the spectrum. By using small data packets inside the home-where distribution could be interrupted by electrical devices being turned on and off-only a little bit of data might be lost rather than the whole signal. PLT suffers from distance limitations: It can reach about 2 miles (3 km) with a very low bandwidth or a few hundred yards offering several Mbps. However, unlike with DSL, most premises worldwide are within 300 yards (100 m) of an electricity substation. Vendors are working on extending the reach. There are significant differences between the electrical distribution systems around the world, and these differences affect the implementation of BPL. For example, in North America, relatively few homes are connected to each distribution Chapter 12 Broadband Access Alternatives transformer, while in Europe, hundreds of homes may be connected to each substa- tion. BPL signals do not propagate through distribution transformers, and addi- tional equipment is therefore required in the North American market. Because of differences in the way the electrical grids are designed, Europe and Asia will most likely see PLT before the United States does. In European systems, electricity is sent to the customer at between 220 and 240 volts, as compared to 110 volts in the United States. The high power throughput means a European substation can serve 100 to 300 homes, while in the United States, a substation can reach only about 8 to homes. Furthermore, U.S. interest in PLT is limited because of the proliferation of existing last-mile technologies such as DSL and cable modems, particularly in urban areas. Many people believe that DSL, cable modems, and fiber alternatives may ultimately outweigh the potential for PLT in Europe as well. Still, with more than 3 billion users worldwide, the penetration of the electric- ity networks is almost ubiquitous, bringing access to a global communications infrastructure within reach of the majority of people, without the need for heavy infrastructure costs. However, xDSL and ca