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DSL Technology
DSL, Digital Subscriber Line technology is a new way to utilize your existing copper
telephone lines (like the ones in your house or business) and deliver very high speed
connections. It works like your existing, slow dial-up modem but without the slow dial-up
part.
With DSL you are always connected directly to the Internet (or Corporate Intranet) with
your own secure, dedicated line.
This is accomplished by multiplexing your telephone line into 3 separate bandwidths or
frequencies. Currently your voice is carried over the lower frequencies (30hz to 4khz)
leaving the higher frequencies or bandwidth unused. DSL technology has enabled us to
utilize the higher frequencies for two way data transmission at very high speeds. This way
we can use the 300khz to 700khz band for upstream transmission and 1000khz and above for
wide frequency, very high speed downstream service. And since we are using the bandwidth
your current phone doesn't, you can talk on your phone and surf the net at the same time
With DSL you don't need to add an additional phone line!
Also by separating your voice and data into discrete channels, we can transfer the data
portion over new, optimized packet or cell switched connections. This is far superior and
faster than using existing, congested "legacy" phone networks built 50 years ago
for voice transmission (or telegraph) only.
Your DSL service works by sending (via your new digital modem, also called a router) your
requests to the local telephone facility or Central Office. At that point you are placed
on our Fiber Optic Network (Frame Relay and ATM) and directed to our facility.
We in turn, verify your access and pipe you into the Internet via our multiple and
redundant OC24's and DS3's (very large pipes). Your web pages or Corporate documents are
returned to you in the reverse order. Using a National Fiber Optic Network allows us to
offer this service anywhere in North America that has DSL activation in the local Central
Office. 
DSL Types
ADSL (Asymmetrical Digital Subscriber Line)
ADSL was originally designed by
telephone companies to provide video-on-demand to compete with the cable industry. Turns
out this asymmetrical approach is also perfect for surfing the web. ADSL is faster in the
return (download) than send (upstream) direction. As a typical use on the net is to send a
small request and receive a large file or download, this approach is excellent. Upstream
speeds are usually 128kbps to 1.088Mbps while downstream speeds race up to 8.192Mps (over
5 times as fast as a T1 circuit).
HDSL (High bit rate Digital Subscriber Line)
HDSL was developed as a faster cousin
to ISDN (64-128kbps) technology. This enabled telephone companies to offer T1 (1.544Mbps)
speeds over regular copper phone wire without the use of repeaters. HDSL is the oldest and
most heavily deployed version of DSL. If you currently have a T1 circuit on two pairs of
copper wires, you are probably already using DSL!
RADSL (Rate Adaptive Asymmetrical Digital Subscriber Line)
RADSL is basically a rate adaptive
version of ADSL. Rate adaptive technology allows a service provider to adjust the
bandwidth for a particular application or compensate for line length or quality. This
adjustment can be pre configured or self adjusting. A larger percentage of users near a
Central Office can be served by RADSL's ability to lower data rates to extend the reach of
the service. Like ADSL, it also operates on standard phone lines.
SDSL (Symmetrical Digital Subscriber Line)
SDSL is the symmetrical cousin in the
DSL family. It was designed for applications requiring high bandwidth in both directions.
Typical current speeds are 144kbps to 1.1Mbps in both directions. This is well suited
toward large file transfers toward and away from users or for Web Site Hosting services.
VDSL (Very high bit Digital Subscriber Line)
VDSL is a shorter distance, higher
speed derivative of the DSL family. It was intended for "the last mile", the
costliest link from any service to any final destination. As this last segment is usually
dedicated to a single customer, VDSL can be combined with fiber to offer cost effective,
short distance runs at speeds of up to 52Mbps.
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