How do they work? A bit technical for a beginner! Imagine an ordinary light switch. It can be either on or off. That's digital. Say we have 8 of these switches in a row (we call that 8-bit). There would be 256 possible combinations of those switches.
Now imagine a "dimmer" light switch. It can be on, or off, or any number of positions in between. That's analogue. We could perhaps divide the range up into 256 individual brightness steps.
In the modem, a chip converts the digital number into its corresponding analogue step. Of course there are more combinations in a computer; Windows is 32-bit, nearly 4.3 billion combinations or steps!
Obviously the whole modem story is more complicated than that, but that's the basic idea.

What's an AT command?

Years ago the Hayes company devised a set of commands to control their modems. Most of these started with AT (for ATttention), so became known as the Hayes AT command set. Since then other manufacturers have developed their commands around the basic Hayes set. The range of commands has increased, so that the correct list of commands fromthe manufacturer is now needed for each modem.

How is is used?
The AT commands can be issued to the modem in a number of ways. The most direct way is through a terminal program such as Windows95/98's Hyperterminal, but this is perhaps beyond beginner territory.
In Windows95/95, a set of commands are issued to the modem by Windows. An information file (inf) is used to tell Windows which commands the modem understands. This is why it is important to have the correct inf file to install the modem.
Extra Settings can also be sent to the modem - Windows9x has these in the modem properties (see The Inf File). Here we don't need to include the initial AT as Windows sends that. Also the case is unimportant, so I usually use lower case letters as they are less easily mistaken, eg i or 1, o or 0.

What's all this V90, X2, V34 stuff?

Modems all have different protocols to connect to each other. You can think of them as different languages. Over the years new protocols have been devised to overcome the difficulties of faster connection speeds. The common ones now have all but superseded everything that went before. They are:
V34, which is used for speeds up to 33600bps. Note that this is still the maximum upstream (ie you to the ISP) speed possible with a conventional modem.
X2, the protocol devised by USR for speeds up to 56000bps. Despite its strengths, very few other companies followed this route.
K56flex, originally called K56plus by Rockwell, really got off the ground when they collaborated with Lucent to create flex. Many other manufacturers followed this protocol, mainly due to their reliance on chips from Rockwell and Lucent.
V90, the supposed Esperanto or universal language of modems. It is a commonly agreed standard, although in practice it doesn't always work out that way! However this is the current preferred way forward for modems.
Obviously different types of modem won't always talk to each other. V34 is the common protocol that they all share, so if the higher speeds don't tally, they are limited to 33600bps.

What does my modem connect to at my ISP?

Another modem! But quite a different modem to yours, especially if you have a 56k type. Actually they are basically the same, but there are rows and rows of them - they're known as racks of modems. Why are the 56k ones different? Well remember that digital stuff at the start? It isn't changed to analogue here. That's why it's faster.

Why do I get better connections to some ISPs?

Well, like your modem, there are a number of different modem rack manufacturers. USR, Lucent (Livingstone), Ascend and Cisco are the major players. They each have slightly different versions of the program that translates the modem "languages". So sometimes they work better with a particular modem.

I have a 56k modem. Why can't I get 56k?

Nobody can. Well at least not practically, 56k is the maximum in theory. It depends on the quality of your phone system. When you actually connect things together, you get slight resistances at the joins. Every time another join is introduced it makes things a bit worse. The longer the line from you to the ISP, the worse things will get.
But it's not as bad as it seems! Shortly after your phone line leaves your house, it changes from copper wire to optic fibre. There's a converter here, as optic fibre carries light beams, not electricity. But optic fibre is much better when it comes to losses and "noise", so it can travel for hundreds of miles this way without losing quality - my favourite ISP is 130 miles from my house and I can still connect at 52000bps!
So you see it's that copper bit from your modem to the telephone company box in the street that causes most of the trouble. The newer the phone system the better, which is why cable companies often have an advantage here.

What's a chipset?

We talk about this a lot in the modem world. Remember I said that the modems have silicon chips to convert the signal? Usually there are two or three of these. Most of them are made by just a few companies, Rockwell, Texas Instruments, Lucent, PCtel. And a few others. Each chip manufacturer now seems to make two or three sets of chips according to the purpose. The AT commands are different for each chipset. And that's why we worry about which set of chips is used.

What's all this about software modems?

Traditionally modems have had chips to do all the jobs they need to do. They can work on their own. All external modems are still made this way.
But now that computer processors (eg Pentium) are getting faster, it has been possible to make cheaper modems by leaving off some of the chips and getting the computer's processor to do that job. Software is needed to tell the processor what to do, which is why they are called software modems. They are sometimes referred to as Winmodems, because the software is written for Windows. They don't work in other operating systems, although they could if the software was written for them.
Many people dislike software modems. But if you only want to use Windows, they provide a cheap and effective alternative. My software modem works very well, but I have an external modem as well, just in case!

Version 1 of beginner's corner. I hope this has explained the basics for you. If there is anything else basic you think I should include, tell me! (Please remember to change o to 0)..
© 24/3/99 Chris Bolus