Sound card, headset and you can talk to the world

Before you can participate in all the fun, you will need to make sure you have a "sound card" - if you can play music over your computer, you have one.

If you can't, have a look at How Stuff Works for their excellent overview of the sound card before you invest in one or try a DIY fix with www.howstuffworks.com.

Most newer computers come equipped with speakers that are adequate for online telephony, but the built-in microphones that come with many are not really up to the task. Headsets and standalone microphones that will do a better job are inexpensive and available in most general goods retail stores.

On most PCs, the connecting ports for speakers, microphones and headsets are clearly marked on the back, and the ports tend to use a universal plug - those ports, by the way, plug into the sound card.

And if you want to participate by sending video images, you will need a "web cam".

The cheapest of these is about $100 right now, but read a few product reviews before you take this plunge: quality varies dramatically.

How Stuff Works also has an excellent overview of how web cams work - and how to set one up.

With only a few exceptions, you will also need to download software to make internet calls.

Usually, these are not large downloads - a few megabytes - but they do tend to use a lot of your computer's resources.

How it works - PC to PC:

Some PC-to-PC software supports direct communication if both parties know their IP addresses - the equivalent of a phone number for your computer.

Unfortunately, IP addresses are assigned "dynamically" for most types of internet accounts, meaning each time you log on to the internet, your computer's "phone number" changes.

You and your friend can find your current IP addresses by looking under the "details" tab of your internet connection icon, if you're running a newer computer, and exchanging those by e-mail or instant messaging.

Mostly, though, callers connect up in a third space, a hosted environment that can be either transparent or filled with chat rooms and ads.

How it works - PC to phone:

Your digitised voice signal leaves your computer and travels on the internet via VoIP.

It is then "bridged" into the traditional system as a local call so it can be heard on a regular phone - rather like what happens between a mobile phone and a land line, except you can't call the computer from your home phone.