Digital Subscriber Line (DSL) is a technology that
brings high bandwidth information to homes and small businesses over the
existing 2 wire copper telephone lines. Since DSL works on the existing
telephone infrastructure, DSL systems are considered a key means of
opening the bottleneck in the of the existing telephone network, as
telephone companies seek cost-effective ways of providing much higher
speed to their customers. DSL is a technology that assumes digital data
does not require change into analog form and back. This gives it two
main advantages. Digital data is transmitted to your computer directly
as digital data, and this allows the phone company to use a much wider
bandwidth for transmitting it to you, thereby giving the user a huge
boost in bandwidth compared to analog modems. Not only that, but DSL
uses the existing phone line and in most cases does not require an
additional phone line. The digital signal can be separated or filtered,
so that some of the bandwidth can be used to transmit an analog signal
so that normal telephone calls can be made while a computer is connected
to the internet. This gives "always-on" Internet access and does not
tie up the phone line. No more busy signals, no more dropped
connections, and no more waiting for someone in the household to get off
the phone.
Because analog transmission only
uses a small portion of the available amount of information that could
be transmitted over copper wires, the maximum amount of data that you
can receive using ordinary modems is about 56 Kbps (thousands of bits
per second). With ISDN you can receive up to 128 Kbps. This shows that
the ability of your computer to receive information is constrained by
the fact that the telephone company filters information that arrives as
digital data, puts it into analog form for your telephone line, and
requires your modem to change it back into digital. In other words, the
analog transmission between your home or business and the phone company
is a bandwidth bottleneck. DSL however offers users a choice of speeds
ranging from 144 Kbps to 1.5Mbps. This is 2.5 times to 25 times faster
than a standard 56 Kbps dial-up modem. This digital service can be used
to deliver bandwidth intensive applications like streaming audio/video,
online games, application programs, telephone calling, video
conferencing and other high-bandwidth services.
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