Currently DSL service is offered by

• A. Cable companies
• B. Wireless providers
• C. Internet service providers
• D. Telephone companies

Answer: (D)

DSL uses existing copper telephone lines to bring high-speed data to homes, and the local telephone company owns and maintains that copper local loop from the central office to the customer. The network concept behind DSL involves a DSL modem at the customer site and a DSLAM at the central office, which multiplexes data over the same line used for voice. Because this technology relies on the telephone company’s infrastructure, it has traditionally been offered by telephone companies.

Cable companies provide internet over coaxial cable using a different technology (DOCSIS), and wireless providers deliver service via radio signals. An Internet service provider is a general term for a company that offers internet access, but DSL specifically is tied to the telephone network.