DSL (digital subscriber line) is a common form of high speed internet that allows you to enjoy internet access through the infrastructure of the local telephone company. It allows high speed data to be transported over existing copper telephone lines.
There are two types of DSL technology: carrierless aplitude/phase (CAP) and Discrete multitone (DMT system). CAP works by taking a copper wire and splitting them into 3 bands to lessen interference. The first band (0 to 4 khz) is used for voice (telephone conversations). The second band (25 to 160 khz) is used to send requests (like typing in a web address and hitting Enter) while the third band (240 khz to 1.5 mhz) is for downloading information (such as the loading of a web page or saving a picture file to your computer). It is simpler than DMT and this system is not affected by interferences or poor quality wires.
The DMT system works by splitting the frequency range to 247 channels of 4khz each and allocating a range for lower channels as bidirectional for downstream and upstream. In this way, it allows your connection to operate like most modems which are on all of the time. Advantages to this type of system include automatic switching to another channel if the current one is experiencing interference. So, basically if you are using DMT system, low pass filters may be needed in telephone sockets where you wanted to make phone calls. It's because phone calls takes place below 4 khz frequency and filters will block anything above to avoid data signal interference with the phone.
DSL Internet is a very affordable option if you want a high speed connection. Check out our internet providers guide to compare DSL providers plans and pricing.