ADSL Explained
ADSL is a new and emerging technology that was developed by Bellcore Labs of Morristown, New Jersey. ADSL stands for Asymmetric Digital Subscriber Line. Think of it as a super-duper souped up ISDN with some key technological differences. ADSL is moving toward becoming the next big technology in high-bandwidth connectivity. Originally, ADSL was developed for interactive TV that began in 1987. It has the potential to bring as much as 7MB of data across the copper telephone wires that are already installed in most homes, and it is available today.

In general, ADSL is a high-speed transmission technology. It is asymmetric in the sense that capacity is higher when coming at the end user, than it is leaving. However, the outgoing (the slower direction) is still considerably faster than an analogue modem connection. In fact, it's considerably faster than ISDN. It works by dividing the bandwidth of copper telephone lines into different frequency ranges, known as carriers. This enables several different simultaneous signals on the same wire. With ADSL, the separate carriers each carry different parts of the same data transmission simultaneously in a process known as Frequency Division Multiplexing (FDM), which means more available bandwidth and higher speeds for the end user. In this way, ADSL can accommodate simultaneous high-speed data transmission, video transmission, and fax transmission, all without interrupting the regular telephone service on the same line. There is a frequency range reserved for Plain Old Telephone Services (POTS) so that you can still make a phone call during a high-speed data transmission, and in fact, you can still make a phone call in the event of an electrical power outage.

Advantages
There are multiple advantages to using ADSL. For one, ADSL will transcend the speeds of current data transmissions. Presently, ADSL is capable of delivering downstream speeds of up-to 2MB burst and upstream speeds of 256K burst. However, rates have the capability of increasing these speeds. In years to come, you can expect downstream speeds of up-to 32MB and upstream speeds as high as 2MB.

No Dial-up Connection, ADSL builds high bandwidth into your existing phone line, and once you install your ADSL modem it's always on. This eliminates the need to dial-up in order to establish a connection to the Internet or to your corporate LAN.

Maximum Utilisation, of Resources Regular telephone services use about 1% of the actual capacity of the telephone lines. ADSL picks up the slack, using the remaining 99% for high-speed data transfer. This is accomplished by setting different frequency channels for different functions, so that voice communication still happens at the lower end of the frequency spectrum, while the rest of the wire is used to carry higher frequency data transmissions.

Multitasking, because of the different frequency channels used on the same wire, ADSL enables the simultaneous use of voice and data. You can make or receive phone calls, send or receive faxes, at the same time that you are surfing the Net or accessing data on a corporate LAN and all on the same phone line.