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Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telephone line. The user's computer or router uses an attached modem to encode and decode information into and from audio frequency signals, respectively. Despite the proliferation of high-speed Internet access (broadband), dial-up Internet access may be used where other forms are not available or the cost is too high, such as in some rural or remote areas. Dial-up Internet has been around since the 1980s via public providers such as NSFNET-linked universities and was first offered commercially in July 1992 by Sprint.〔http://h-net.msu.edu/cgi-bin/logbrowse.pl?trx=vx&list=edtech&month=9207&week=&msg=An61j4s0%2BR1UHNuEZOgGfw&user=&pw=〕 ==Availability== Dial-up connections to the Internet require no infrastructure other than the telephone network and the modems and servers needed to make and answer the calls. Where telephone access is widely available, dial-up remains useful and it is often the only choice available for rural or remote areas, where broadband installations are not prevalent due to low population density and high infrastructure cost. Dial-up access may also be an alternative for users on limited budgets, as it is offered free by some ISPs, though broadband is increasingly available at lower prices in many countries due to market competition. Dial-up requires time to establish a telephone connection (up to several seconds, depending on the location) and perform configuration for protocol synchronization before data transfers can take place. In locales with telephone connection charges, each connection incurs an incremental cost. If calls are time-metered, the duration of the connection incurs costs. Dial-up access is a transient connection, because either the user, ISP or phone company terminates the connection. Internet service providers will often set a limit on connection durations to allow sharing of resources, and will disconnect the user—requiring reconnection and the costs and delays associated with it. Technically inclined users often find a way to disable the auto-disconnect program such that they can remain connected for more days than one. A 2008 Pew Internet and American Life Project study states that only 10 percent of US adults still used dial-up Internet access. The study found that the most common reason for retaining dial-up access were high broadband prices. Users cited lack of infrastructure as a reason less often than stating that they would never upgrade to broadband. According to the United States Federal Communications Commission (FCC), 6% used dial-up in 2010. By 2013, that number had fallen to 3%. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dial-up Internet access」の詳細全文を読む スポンサード リンク
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