Usually, this would be in the form of a GSM data card, or via a multifunction PC Card that provides GSM connectivity among its other features. You'll also need a cable to physically attach this card to the mobile phone. Not all cards are compatible with all phones, and a different cable is required for each type of phone the card supports, so keep this in mind when shopping for GSM or multi-function PC Cards.

Once such a card is installed and attached to a mobile phone, to all intents and purposes you can treat it as a conventional faxmodem connected to a standard telephone line to make data calls, Dial-Up Network connections and even to send and receive faxes. The only real disadvatage of making connections using a mobile phone in this way is that currently the maximum data transfer speed you can achieve is 9,600bit/s--in other words, three and a half times slower than a conventional V.34, 33,600bit/s analogue modem.

A newer, neater alternative is to buy a phone in a card. These can be obtained from a few leading phone vendors, and effectively put a phone into a PC Card format. With just an aerial poking out the side of the notebook, all you need do is insert the phone SIM into the card, whereupon your GSM carrier account is transferred to the card, and you can use it much like a standard modem.