Networks : Connecting to a WAN

Connecting computers together at different locations on a WAN is more difficult than connecting computers on a LAN. This is because it is not possible to join two computers which may be thousands of miles away from each other by a simple cable.

Therefore connections to a WAN are usually made over a public network such as the Public Switched Telephone Network (PSTN). The cables that connect the computers are owned by a telephone company. Other companies pay the telephone company money to use its cables to build their WANs.

Telephone companies provide many different alternative methods that can be used to connect computers at different locations together. The three most common systems are :

Method	Description	Speed
Modem and Telephone Line	A modem converts digital computer data into analogue form so that it can be sent across a standard telephone line to another computer.	Slow
Terminal Adaptor and ISDN Channel	A terminal adaptor sends data in digital form down a special type of connection called an ISDN channel.	Faster
Broadband	An ADSL or Cable Modem sends data in digital form down a telephone line or cable TV connection.	Very Fast

GCSE ICT Companion 04 - (C) P Meakin 2004