ADSL (Asymmetric Digital Subscriber Line, or DSL for short) is a high-speed Internet access service that utilizes existing copper telephones lines to send and receive data at speeds that far exceed conventional dial-up modems.
The fastest dial-up modems are rated at 57 kilobits per second (Kbps), and usually operate at about 53 Kbps under good conditions. By comparison, ADSL allows datastream speeds from 1.5 to 8 megabits per second (Mbps), depending on the grade of ADSL service purchased.
ADSL uses standard telephone lines to transmit upstream and downstream data on a digital frequency, which sets these datastreams apart from the analog signals telephones and fax machines use. Because the ADSL signal is operating on a different frequency, the telephone can be used normally, even when surfing the Web with ADSL service. The only requirement will probably be inexpensive DSL filters on each phone or fax line, to remove any "white noise" on the line that might be generated from ADSL service.
The "asymmetric" in ADSL refers to the fact that the downstream data rate, or the data coming to your computer from the Internet, is traveling faster than upstream data, or the data traveling from your computer to the Internet. Upstream data rates are slower because Web page requests are fairly miniscule data strings that do not require much bandwidth to handle efficiently.
Some businesses, however, may require matching upstream rates for uploading large files. SDSL, or Symmetric Digital Subscriber Line is an option. "Symmetric" indicates that both datastreams are operating at the same speed of 1.5 to 7 Mbps, depending on the grade purchased. SDSL service requires a dedicated telephone line because, unlike ADSL, telephone and fax services cannot share a line with SDSL service.
ADSL service requires an Internet service provider (ISP), and ADSL modem. The modem is often provided free of charge, and most ISPs that offer ADSL service require subscriber contracts of one year. ADSL is also more expensive than economical dial-up service, which can cost less than US$10 per month.
ADSL is an "always on" service, meaning that as long as your computer is powered on, it will automatically stay connected to the Internet unless you manually disconnect via software or hardware. ADSL is especially suited for gamers, CAD use, streaming multimedia and downloading large files. Family members can share ADSL accounts, with a basic monthly fee covering several mailboxes. Unlike dial-up service, which stipulates only one session be instigated at a time, multiple members can be using ADSL service simultaneously on various computers in the house without violating policy.
ADSL is not available to everyone. DSL providers, or even your local phone company, can tell you if service is available in your locale. Speeds will vary depending upon your physical distance from local hubs. Some customers with close proximity may be able to take advantage of newer varieties of ADSL, called ADSL2 and ADSL2+, which have even greater throughput rates, from 12 to 24 Mbps downstream and 1 to 3.5 Mbps upstream.
The fastest dial-up modems are rated at 57 kilobits per second (Kbps), and usually operate at about 53 Kbps under good conditions. By comparison, ADSL allows datastream speeds from 1.5 to 8 megabits per second (Mbps), depending on the grade of ADSL service purchased.
ADSL uses standard telephone lines to transmit upstream and downstream data on a digital frequency, which sets these datastreams apart from the analog signals telephones and fax machines use. Because the ADSL signal is operating on a different frequency, the telephone can be used normally, even when surfing the Web with ADSL service. The only requirement will probably be inexpensive DSL filters on each phone or fax line, to remove any "white noise" on the line that might be generated from ADSL service.
The "asymmetric" in ADSL refers to the fact that the downstream data rate, or the data coming to your computer from the Internet, is traveling faster than upstream data, or the data traveling from your computer to the Internet. Upstream data rates are slower because Web page requests are fairly miniscule data strings that do not require much bandwidth to handle efficiently.
Some businesses, however, may require matching upstream rates for uploading large files. SDSL, or Symmetric Digital Subscriber Line is an option. "Symmetric" indicates that both datastreams are operating at the same speed of 1.5 to 7 Mbps, depending on the grade purchased. SDSL service requires a dedicated telephone line because, unlike ADSL, telephone and fax services cannot share a line with SDSL service.
ADSL service requires an Internet service provider (ISP), and ADSL modem. The modem is often provided free of charge, and most ISPs that offer ADSL service require subscriber contracts of one year. ADSL is also more expensive than economical dial-up service, which can cost less than US$10 per month.
ADSL is an "always on" service, meaning that as long as your computer is powered on, it will automatically stay connected to the Internet unless you manually disconnect via software or hardware. ADSL is especially suited for gamers, CAD use, streaming multimedia and downloading large files. Family members can share ADSL accounts, with a basic monthly fee covering several mailboxes. Unlike dial-up service, which stipulates only one session be instigated at a time, multiple members can be using ADSL service simultaneously on various computers in the house without violating policy.
ADSL is not available to everyone. DSL providers, or even your local phone company, can tell you if service is available in your locale. Speeds will vary depending upon your physical distance from local hubs. Some customers with close proximity may be able to take advantage of newer varieties of ADSL, called ADSL2 and ADSL2+, which have even greater throughput rates, from 12 to 24 Mbps downstream and 1 to 3.5 Mbps upstream.
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