General Information about ADSL

The rapid technological changes in telecommunications and the technology development of ADSL (Asynchronous Digital Subscriber Line) made it possible to take advantage of the copper wire network. The copper wires are capable of handling a much greater bandwidth, or range of frequencies, than that demanded for voice. DSL exploits this bandwidth to carry information on the wire without disturbing the line's ability to carry conversations (POTS or ISDN). This extra information can be services like voice, data (including internet traffic) and video with high quality and fidelity.

Figure 1

If you have ADSL installed, you were almost certainly given small filters to attach to the outlets that don't provide the signal to your ADSL modem. These filters are low-pass filters - simple filters that block all signals above a certain frequency. Since all voice conversations take place below 4 KHz (Figure 1), the low-pass (LP) filters are built to block everything above 4 KHz, preventing the data signals from interfering with standard telephone calls.

Asymmetric DSL (ADSL) line divides up the available frequencies in a line on the assumption that most Internet users look at, or download, much more information than they send, or upload. ADSL technology can provide maximum downstream (internet to customer) speeds of up to 8 Mbp/s, and upstream speeds of up to 640 Kbp/s.