What Makes DSL Work by: Kara Glover

2016.02.24 21:47珹&帥




Feel free to reprint this article in newsletters and on 

websites, with resource box included. If you use this 

article, please send a brief message to let me know where 

it appeared: kara3334@yahoo.com 


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 

waves. 


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 

the rest! 


�2008 by Kara Glover 




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