VoIP (Voice over Internet Protocol) is simply the biggest revolution in phone technology since cellular, and poised to eclipse it. By routing phone calls over broadband Internet connections, VoIP bypasses traditional phone service and delivers practically free long-distance calling around the world. If you aren't using VoIP yet, you should be. Or you may be using it, and just not know it. Almost all voice chat services, like Skype and GoogleTalk, use some form of VoIP.

Just a few short years ago, VoIP was the province of geeky types who talked to each other through proprietary software that had to be installed on computers at each end of the connection. Vonage, Skype and other consumer-oriented companies turned that picture on its head and brought VoIP to the masses through user-friendly, near plug-and-play hardware and software solutions. It's easy to make the switch from landlines, by just plugging a box in between your regular phone equipment and your broadband connection. The VoIP companies (Vonage, AT&T CallVantage, EarthLink, VoicePulse and many more) usually provide the box for free, and monthly unlimited call rates are cut-throat competitive.

Now, Wi-Fi is enabling VoIP to move out of the home and office, pitting it squarely against cellular service. Cellular providers have seen the writing on the wall, and are now starting to offer their own hybrid cell/Wi-Fi services that take advantage of the strengths of each. Wi-Fi-based VoIP calling is the most efficient solution in homes, offices and public hotspots where broadband provides reliable and inexpensive connections. Cellular works best in the field, where Wi-Fi may not be available. It's expected that all major carriers will offer hybrid service in the near future, T-Mobile is the first, with its Hotspot@Home offering. Read on for a complete guide to VoIP in all its forms.

Why VoIP?

VoIP may sound like an alien insectoid curse, but it's the hottest word in telecom. Long-distance companies, cable companies, and broadband Internet providers are all competing with VoIP specialists to offer cost-saving, feature-rich VoIP services that operate over your excess cable-modem or DSL bandwidth. VoIP not only offers big savings -- about 20 to 50 percent depending on the service and your calling needs -- but you get features usually found only on high-end phone systems, such as call routing and voicemail-to-email integration.

One of the key advantages is local long distance -- by using a virtual phone number with a different area code, you can maintain a phone number in D.C. even if you live in L.A., so you won't pay toll charges when calling D.C., nor will your D.C. friends pay extra when they call you. This can be a big money-saver for business travelers and telecommuters. And thanks to new portability laws, you can keep your existing phone number when switching to VoIP if you like.

Right now, most VoIP subscribers use in-home adapters for landline phones, but a slew of portable Voice-over-Wi-Fi (VoWi-Fi) handsets are now available, such as Skype WiFi phones from and Belkin and a hotspot-capable VoWi-Fi phone from Linksys. T-Mobile has a new handset and service program that lets you flip between cellular voice and VoIP calling anytime you come within range of a public hotspot.

From Walkie-Talkie to Pin-Drop Quality

For almost a decade, tightfisted tech types have been legally hacking the long-distance companies by using peer-to-peer software that enables IP-based voice calls via modem. The voice quality on these Internet phones was ludicrously bad, however, and you were lucky if you managed to make and keep your garbled connection. Now, thanks to dedicated hardware processing and increasing support for protocols like SIP (Session Initiation Protocol), VoIP can be as smooth as a session that uses the regular telephone network, greatly increasing its appeal. Most software-based VoIP providers, with the notable exception of Skype, use SIP equipment, so you can choose your own handset in many cases.

Connecting a VoIP converter box is easy if you already have a broadband connection and network router. You simply plug your phone into the converter box, and then the box into your router. Extension phones are supported over normal telephone wiring.

Local phone companies are almost as threatened by VoIP as long-distance carriers, and many now offer their own VoIP services to compete with the upstarts. Verizon has residential VoIP service, and SBC, BellSouth, and Qwest all have VoIP services aimed at business customers. They join dozens of other providers that already offer high-end VoIP services to corporate customers. Businesses are particularly interested in VoIP's affordability, flexibility and the ability to upgrade via software. They also like its potential for tight integration with email and Web-based services for applications such as call centers, videoconferencing, and click-to-talk Web pages. Many of these features are migrating to consumer customers. For example, most consumer videoconferencing equipment uses the same SIP protocol used by VoIP, and affordable videophone options are available from Packet8, Motorola (the Ojo), and others.

What about voice quality with VoIP? With one of the better services and a nice fat broadband pipe, you're not likely to tell the difference between VoIP and a landline, and you'll probably find it better than your cell phone. Two of the biggest early raps against VoIP -- the lack of white page listings and 411/911 access -- have all but disappeared for the major services (Skype is a notable exception). If these are important to you, be sure to check their cost and availability when selecting a plan.

One flaw, however, will always remain: VoIP only works if your broadband connection is working. If your power goes out, or your connection drops, so will your phone service. That's another good reason to look to the coming rollout of hybrid cell/VoIP services, so you have a fallback in emergencies.

On the flip side, one of VoIP's biggest savings comes from the relative lack of taxes and fees. That situation may not last forever, but the service should be relatively levy-free for the near future. Choose a good provider and you can expect quality service, cool features, and huge savings.