The Probert Encyclopaedia of Science & Technology

ADSL

ADSL (Asymmetic Digital Subscriber Line) is a form of DSL communications in which a digital voice telephone line that uses the existing twisted pair copper telephone network, is split into two frequency channels. Voice calls are transmitted at frequencies up to 20 kHz and data communications along the same cables but at frequencies between 25.875 kHz and 1.104 MHz. ADSL is able to achieve data receive transfer speeds of up to 6 megabits per second up to 12000 feet, or 1.5 megabits per second up to 18000 feet, with data transmission at around 256 kilobits per second. Most domestic ADSL lines are shared between subscribers, and this gives rise to 'contention', whereby the shared line can only provide so much data at a time, and if multiple users are all transferring data at the same time then the speed of transfer noticed by them all is significantly slower than when only one user is accessing the ADSL line, with a 50:1 ratio if all 50 users are simultaneously accessing the service then each will realise a transfer speed of 1/50th the potential.
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