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date of copyright: September 2005
What Makes DSL Work
by Kara Glover
I need to explain a few things first here, so bear with me.
A sine wave is a basic type of wave. Sound can be divided into sine
Sound waves, or sine waves, are measured by the number of cycles they
make in one second.
The number of sine wave cycles sound waves make in one second is
measured in hertz. The symbol for hertz is Hz.
The sine waves created by human voices average 0 to 4,000 Hz. That
means the sound of your voice produces from 0 to 4,000 sine waves made
of sound in a single second. That 0 to 4,000 is considered your
voice’s range or frequency.
OK. Now that we’ve gotten that out of the way:
Telephone wiring is made of copper. That wiring is capable of
transporting much higher frequencies, or more hertz, than just the
frequencies your voice can produce. To put it another way, there’s a
lot more room on the wiring that’s not being used. So the phone
companies divide up the wiring to use it for other things as well,
namely internet usage.
This may seem like common knowledge. But if you think about it, you
download from the internet more than you upload. You’re downloading
this article right now! But how often are you uploading? Maybe you
send lots of emails, which aren’t very wieldy, or a big attachment
once in awhile. That’s nothing compared to the website and programs
you probably download. So the phone company makes lots room on the
copper wire for frequencies dedicated to downloading from the
internet, and less for uploading. The phone companies uses higher
frequencies on the wiring for both this internet uploading and
downloading.. And by the way, the frequencies are higher than those
used for both voice and faxes. This is how you’re able to surf the web
and talk on the computer at the same time!
Have you ever wondered why you need to install filters on all your
phones and fax machines when you install DSL? Well, the filters are to
keep out those higher frequencies reserved for your internet data out
of your phone and fax lines, and keep the frequencies you need to talk
and fax with in.
You can thank your DSL modem for helping the process. Transmission to
and from the internet is all data transmission. The modem is the tool
that sends the data coming to and from your computer over the phone
line to your phone company, while voice or fax signals may be coming
at the same time. At the phone company a contraption called a
multiplexer divides up the voice or fax from the data. Next it sends
the data part to your internet service provider, which takes care of
©2005 by Kara Glover
About the author:
Kara Glover is a Computer Tutor and Troubleshooter. You
can find her articles and tutorials on topics such as
Microsoft Word®, Excel®, and PowerPoint® at her website: