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About ADSL Broadband

DSL is the next generation of internet access technology. A house or business with DSL has a data socket, that looks like a phone socket. DSL is a direct connection to the internet, always on.

To connect, a "DSL modem" is needed; DSL modems are starting to be available on the open market, but they are normally supplied by the DSL provider you choose, since DSL standards are varied, and the modem must be compatible with the equipment favored by the provider. (When talking to your provider, you may ask if they allow you to source your own equipment, for example, second-hand).

DSL modems are of three basic types: external, internal or USB. For external modems, on the back is a socket, usually marked LAN. A cable (ethernet cable) connects this to your computer, which needs an ethernet card, (known as a Network Interface Card, or NIC), such cards are available from dozens of vendors at prices as low as $20, and for this purpose, they all work the same way and are all compatible.
Many current computers, such as the iMac, come with a NIC, and socket, built-in, simplifying things still further. Unlike advanced graphics boards or other specialized hardware, even the oldest computer can accept a NIC card, as long as it has a spare slot. For internal DSL modems, or USB modems, the equipment is plugged in, and some driver software must be loaded into your computer before it can be used.



Basic features of a Broadband ADSL Router

The Broadband ADSL Router provides data access for multiple users who wish to combine broadband access with a telephone service. The user must have direct copper line connection from his premise to the local exchange where the DSL is available. The premise must be within 5 km from the exchange.

  • WAN interface: High Speed Asymmetrical (ADSL) Data Transmission on Single Twisted Pair Copper Wire
  • LAN interface: One 10Base-T Ethernet port for Computer or LAN connections
  • Bandwidth: Auto-negotiation rate adaptation up to 8Mbps downstream and 1Mbps upstream (varies with different ISPs)


Minimum PC requirements:

  • Pentium 100 or equivalent processor
  • Windows 95 (Windows 98 is preferred) or Windows XP, Windows NT and above (depends on the type of modem)
  • 32 MB RAM
  • 2.1GB hard disk capacity (20MB of free hard disk space)
  • LAN connection card (NIC)
  • CD ROM Drive (for loading Home/SOHO Modem Software)


Basic components:

  • Telephone line - direct line
  • PC with network card
  • ADSL Modems (usually provided by ISP)
  • Splitters (usually provided by ISP)
  • Microfilters (usually provided by ISP)
  • Hubs, Routers, Server (for Networking purpose)


ATM Asynchronous Transfer Mode
A high speed network protocol composed of 53 byte cells having 48 byte payloads. Especially good for real time voice and video. DSL lines normally use ATM as the underlying data-transport protocol beneath tcp/ip.

DSLAM Digital Subscriber Line Access Multiplexer
The device placed in the CO that accepts all the DSL lines.

PSTN Public Switched Telephone Network

CO Central Office
A circuit switch that terminates all the access lines in a particular area; a physical building where the local switching equipment is found. xDSL lines running from a subscriber's home connect at their local central office.


Connecting the wires:

  • Telephone Socket to POTS Splitter - RJ11
  • POTS Splitter to Telephone set - RJ11
  • POTS Splitter to ADSL Router- RJ11
  • ADSL Router to Hub/Customer PC - RJ45


This next diagram is of a basic ADSL (a common form of residential DSL) in a home. The splitter depicted here is a small box that strips off the phone signal from the line from the Telco, and leaves the data (indicated by the red shaded lines), to be routed to the data equipment, on RJ11 (phone) inside wires.


A DSL setup, with a filter instead of a splitter, allows the data and telco voice signal to flow through the house phone wires, but filters it from the telephone or fax machines.


Connecting remote offices with broadband:



Norman, 2003

Last Update: 17 October 2002