A History of DSL
A History of DSL by Jack Kennedy
DSL, or ‘digital subscriber line’, is a handy set of technologies that allows you to browse the internet at incredible speed. This technology appeared in homes around the world during the 1990s. But where it came from, and how it works is a mystery to many.
Genesis
Engineers in the 1980s were looking for a way to get bits of information from one computer to another via previously installed telephone lines. Joseph Lechleider, an analyst at Bellcore, and John Cioffi, who founded the Amati engineering firm, came up with the mathematical analysis and circuits that made DSL a reality.
Because this new technology gave customers the option of using their pre-existing phone line for internet service instead of having to pay for a second phone line, telephone companies initially weren’t happy with DSL. Prior to broadband, modems were required to dial up to a service provider. Customers typically had two separate lines; one for the phone and one for the modem.
However, as more media-rich content became available on the internet, phone companies jumped on the technology train. Eventually the telephone companies realized that DSL saved them money since it didn’t require digging new trenches for additional phone wiring. Now, many companies, like AT&T, market their own brand of DSL service.
How DSL Works
Telephone lines consist of a pair of copper wires running from a main trunk, owned by the phone company, to a consumer’s house. Copper is great for being able to carry a wide range of frequencies. This range is referred to as “bandwidth.”
The telephone companies like limiting the bandwidth because it allows them to bundle many wires together at a central location without having any distortion caused by overlapping frequencies. The frequency range of the human voice is from 300 to 3,400 Hz.
Leaving a lot of unused bandwidth - more than a million HZ - on the copper wire, is why engineers started looking at using it for DSL in the first place.
The digital signals being carried by the copper wire are split into upstream and downstream channels by DSL. Market studies show that internet users download more content than they upload, or send. Therefore, DSL makes the downstream channel three to four times faster than the upstream channel.
Jack Kennedy monitors and reveiews the Broadband DSL industry. To read more, please visit The DSL Center.
Article Source: Article King Pro
Tags: high speed internet access. broadband, cable modem, broad band, wireless, DSL. T1
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