asynchronous DSL

networking technology

Also known as: ADSL, asymmetric digital subscriber line

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Last updated

July 19, 2026

Quick Summary

Asynchronous DSL (ADSL) is a networking technology that provides broadband internet connections over traditional telephone lines. The term "asynchronous" signifies that ADSL allocates more bandwidth to downstream traffic (data coming to the user from the internet) than to upstream traffic (data going from the user to the internet).1

ADSL uses a DSL terminal adapter, or modem, to connect a computer or local network to the DSL line. Each user has a dedicated telephone line, but the technology's effectiveness is limited by distance; users must be within a few miles of a telephone switching office. While ADSL was once a common method for internet access, its subscription numbers have declined due to competition from faster cable and fiber-optic services.1

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computer
Communication devices
Asymmetric digital subscriber line (ADSL) modems can be used for transmitting digital signals over a local dedicated telephone line, provided there is a telephone office nearby—in theory, within 5,500 meters (18,000 feet) but in practice about a third of that distance. ADSL is asymmetric because…
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Asymmetric digital subscriber line (ADSL) modems can be used for transmitting digital signals over a local dedicated telephone line, provided there is a telephone office nearby—in theory, within 5,500 meters (18,000 feet) but in practice about a third of that distance. ADSL is asymmetric because…
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DSL
…including the most common type: asynchronous DSL (ADSL). Asynchronous refers to the way that more bandwidth is given to downstream traffic, which comes to the user from the Internet, than to upstream traffic, which goes from the user to the Internet. Traffic on DSL is transmitted over normal telephone lines…
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…including the most common type: asynchronous DSL (ADSL). Asynchronous refers to the way that more bandwidth is given to downstream traffic, which comes to the user from the Internet, than to upstream traffic, which goes from the user to the Internet. Traffic on DSL is transmitted over normal telephone lines…
Read More