Slightly more flexible is the Free World Dialup (FWD) system. This allows users to choose from among software running on a computer, a preconfigured phone or ordinary handsets that are plugged into special analogue-to-digital adapters. Calls between members of the FWD system are free, but ringing an ordinary telephone incurs an extra charge.

This is also the basis of services like that provided by Vonage, which claims to be the “leading broadband telephony provider”, with 170,000 customers. Again, a phone adapter is used to hook up ordinary handsets to pre-existing broadband connections. There are a variety of rate plans available, including those that allow unlimited calls to any phone in the US or Canada.

Vonage is a small and relatively young company – it was founded in January 2001 – that serves principally the domestic user and small businesses. At the other end of the scale, there are networking giants like Cisco offering the entire gamut of enterprise IP telephony products.

The attractiveness of VoIP might seem to represent a huge threat to traditional telecoms companies. Surprisingly perhaps – or maybe as a result of painful lessons learnt through trying to ignore the Internet – major players like AT&T in the US and BT in the UK are already starting to offer VoIP for domestic users, called respectively CallVantage and Broadband Voice. In addition, AT&T has recently announced trials of a “global VoIP telework service”, aimed at multinational companies, while BT has unveiled a timetable for the transformation of its entire system into an IP-based network, culminating in the provision of not just universal VoIP but also what it calls “broadband dialtone” – Sun’s Webtone.

If there is any obstacle to the rapid uptake of VoIP, it seems to be regulatory. A major wrangle going on in the US between the federal and state lawmakers sees many of the latter keen to class VoIP as just another telephone service – with all that this implies for taxation – while the Federal Communications Commission (FCC) is taking a more enlightened, hands-off approach. Whatever the final outcome of this difference of opinion, you don’t have to be clairvoyant to see that VoIP is the future of telephony.

Glyn Moody welcomes your comments.