Asymmetric Digital Subscriber Line (ADSL) is a form of data communication technology that utilizes fast data transmission of digital bandwidth over copper telephone lines.
An advantage of ADSL is that a single telephone connection can be used for both ADSL Internet service and voice calls at the same time. The computer connects to the web through an ADSL modem, which in turn connects to the telephone line by a splitter. The splitter or microfilter allows a single telephone connection to be used for the purpose of both ADSL service and voice calls at the same time. The voice calls would use the analog data transmission whilst the ADSL service would utilize the digital service line (DSL).
ADSL is a variant form of DSL. Digital Subscriber Line (DSL) technology brings high bandwidth information at data rates of up to 6.1 megabits. Other variations of the DSL technology besides ADSL include High bit-rate Digital Subscriber Line {HDSL} and Rate-Adaptive DSL (RADSL).
The ‘A’ in ADSL stands for asymmetrical. This means that the volume of data flow is greater in one direction than the other. With ADSL, the higher bandwidth is focused on the download speeds and upload speeds are reduced. The lower upload speed is due to users generally requiring a greater proportion of their web usage as downloads.
The design of ADSL enables the user to take advantage of the one-way nature of most multimedia communication. Large amounts of information flow toward the user and in contrast, only a small amount of interactive control information returns.
Precursors to ADSL were ISDN and dial-up. ISDN received up to 128Kbps and dial-up only 56Kbps. With either of these technologies, the ability of your computer to receive information is limited. The telephone company receives the digital data and it is then put into analog form for the telephone line. The modem connected to the computer on receipt of this analog data then transformed it into digital format again. A bandwidth bottleneck was a common problem with both ISDN and dial-up Internet.