MangalMan's Perspective.

Nepal telecom is deploying ADSL2+ shortly. Dial up is bad. It is expensive. It is slow. Surfing the net in dial up is getting increasingly difficult as the amount of data to be downloaded while doing so is increasing. Try watching a youtube video off a dial up connection and you will the get the idea. ADSL is Asymmetric Digital Subscribers Line over the loop. That means we can get this type of connection over our normal telephone line. Our telephone line has a pair of copper wire underneath the plastic cover. Our telephone line is also known as POTS as in Plain old telephone service. This POTS uses 0 to 3400 hertz of frequency range to exchange voice over the wire. However copper wire has lots of frequency left unused in it. In ADSL this unused frequency is deployed to carry the data. With an ADSL modem in place one can use the telephone as well as internet at the same time.

I have taken this picture from Nepal telecom's website

Asymmetry means the downstream data rate in this type of connection is far greater that the upstream data rate that means one can download stuffs from internet in much faster pace than one can upload say pictures or videos. All the DSL systems have had this problem of being distance dependent though. As the distance between telecom switching station and customer grows the quality of connection degrades. The difference between cable and ADSL is that cable does not have that problem. However with ADSL you can get dedicated connection directly from the switching station and the quality of connection is always maintained by the DSLAM device at telecom office end and the Customer premises device (ATU-R). Internet Service providers offering cable internet most of the times divide the whole connection amongst several users assuming that no single user uses all the bandwidth allocated. So 128 Kbit/sec internet connections are not actually as they say it is. ADSL2+ is latest ADSL technology increasing the capability. With it on, the distance covered by the System as well as the speed increases nearly three folds.

For ADSL2+ to work in our home one needs a ADSL2+ modem a splitter to split the voice and the data frequency from the copper wire and ADSL internet account from Nepal Telecom in Nepal's context or what ever your Telecom/Internet service provider is. ADSL2+ modem is not actually a modem because it does not modulates/demodulates as the dial up modem does.Signal are digital all the way in ADSL or any other DSL variant systems. Rather it does the handshaking with DSLAM device in switching station and later on works to maintain the quality of service through out the connection session.

NTC's adsl faq link