Rush out to buy a superfast modem and you're likely to be disappointed. Cliff Joseph explains
After months of pre-publicity, the new generation of 56K modems is arriving in the shops. These new modems certainly sound tempting. They can download data from the Internet at a rate of 56,000 bits per second (56Kbps). That's twice the speed of the 28.8K modems that have been the standard for the last year or so, and you can probably pick one up for under pounds 150.

Admittedly, upload speeds - sending information back to the Internet or to another modem user - are slower. But most Internet users spend most of their time downloading Web pages, so upload speed is less important for Internet use. But before you rush out and buy a new modem, there are a few things you should think about. There are in fact two different types of 56K modem, and the speed you get from your modem will depend very much on the modem equipment that you're connecting to at the other end.

The biggest modem manufacturer in the world is US Robotics, which is currently advertising its X2 modems on television. The X2 technology was developed by US Robotics itself, but all the other modem companies are using a different technology called K56 Flex. The two different types of modem aren't completely incompatible, but they can only communicate with each other at the slower speed of 33.6Kbps. So if your Internet service provider uses K56 equipment, and you buy an X2 modem, you'll only be able to connect to your provider at 33.6Kbps. Mind you, right now, most service providers in the UK don't support either type of modem. They're still all trying to make up their minds.

CompuServe is the UK's largest service provider, but Martin Turner, the UK general manager, says: "We're not committing ourselves one way or the another." CompuServe is currently conducting trials with both types of modem, but isn't sure when it will offer 56K connections to its users.

Other ISPs, such as the London-based Direct Connection, are taking a similar stance. "We're not pushing 56K heavily to our customers, partly because of the uncertainty over standards," says Ben Knox, managing director of Direct Connection. The company is about to start testing some new K56 equipment, but "we're suggesting that people hang on for a few months until the situation becomes clear".

Both companies agree that US Robotics and its K56 rivals should get together and submit a new joint standard to the International Telecommunications Union, but ratifying any new standard will take several months, even if the two camps can manage to agree on one. So, even if you buy a 56K modem tomorrow, you'll find that most service providers aren't supporting them yet.

There's one other potential fly in the ointment for some users. The one thing that both types of modem have in common is that they need to be connected to a digital telephone line to run at top speed. There are still a few areas in this country that have older analogue lines, so if you're thinking of buying a 56K modem you should first find out whether you have a digital line in your home or office. Then check with your service provider to see which standard - if any - it intends to support.

Of course, by the time the X2 versus K56 debate is settled, the modem companies will probably have moved on to cable and ADSL modems - but that's another story.