If the Internet can be your bookshelf, your radio and your TV, why can't it be your phone as well?

It's been able to be that for years, actually. But until recently, sending and receiving phone calls online were pastimes best left to techies who could reel off their computers' numeric Internet Protocol addresses from memory -- you couldn't simply plug a regular phone into the Internet.

Now you can. Naturally, it comes at a price, but the fees charged by most "voice over Internet Protocol" ("VoIP" for short) services fall far below those of land-line phone service.

And unlike land-line phone service, you can find real choice in the VoIP market. Companies act as though they actually need to win over their customers, competing to offer the best bundle of services for the lowest price.

VoIP works by breaking down a conversation into a stream of digital packets that can be shipped across any broadband Internet connection. Business took to the technology first, but consumer-priced versions soon followed. I recently tried out three of them: AT&T's CallVantage, 8x8 Inc.'s Packet8 and Vonage's self-titled service.

These contenders share a few things in common: You get your choice of area code; free domestic calling; and call waiting, caller ID and voice mail at no extra charge. You also need a DSL or cable Internet connection (Vonage and Packet8 say satellite access might work, while AT&T says it's "not supported").

Each VoIP service supplies a book-sized box called a telephone adapter with Ethernet ports (to connect to the Internet as well as your computer or home network) and one or more phone jacks. This Internet dial tone only works out of those phone jacks -- plug in a cordless phone if you want to talk in other rooms.

This box must be positioned correctly in your networking setup for it to work, but there's no standard way for doing that. Vonage's adapter can be plugged into either a broadband modem or a router, AT&T's will only function when connected to a modem, and Packet8's adapter must plug into a router.

Getting this placement straight was a little like trying to set up a home theater from individual components -- I spent far too much time rearranging look-alike cables and wishing they didn't all come in shades of gray.

Each adapter came programmed with a phone number and networking settings appropriate to many cable-modem and home- or office-network setups. This means that you can move your "home" number to any other locale with a fast Internet connection, just by plugging in the adapter there.

My own digital-subscriber-line installation, like most DSL services, required me to adjust those settings on the AT&T and Vonage boxes by hooking up each adapter to a computer and typing in a numeric Web address to bring up its configuration menu.

Once connected, all three services let you use an Internet phone almost exactly like the regular kind -- pick up the phone, listen for a dial tone, dial, talk. Their differences come down to price, quality and features.

Vonage, of Edison, N.J., the best-known VoIP service, offers three residential plans: $14.99 a month for 500 minutes of talk time; $24.99 for unlimited local calling and 500 minutes of long distance across the United States and Canada; and $29.99 for unlimited local and long-distance calling. (Beware of Vonage's definition of "local," which counts a call from Maryland to the District or Virginia as long distance.)

The Vonage service worked perfectly -- as long as I didn't use my computer to surf the Internet. If I did, even just to look up the weather forecast, sound quality quickly crumbled, and a "bandwidth saver" option (which squishes voice data from 90 kbps to 50 kbps) didn't help. The experience took me back to the years when I had one phone line for both voice and computer use: "Can you get off the Internet? I need to make a call."

Vonage's adapter is supposed to reserve enough bandwidth for voice calls, even at the cost of slowing down Web surfing, but in this case it did not. Louis Holder, Vonage's vice president for product development, suggested the adapter was defective, something he said happened a "very low number" of times.

Vonage's free calling features match or exceed what you might get on a fancy office or cell phone. Caller ID listings include callers' names. Call forwarding and transfer are free. And you can even have new voice mail messages sent to you in e-mail. Better yet, you can order a "virtual phone number" that rings through to your primary Vonage line for $4.99 a month -- so distant friends and family can avoid paying long-distance charges when they call you.

Vonage recently introduced seven-digit dialing to numbers in the same area code, but I couldn't make much use of it, as the adapter loaned for this test carried a 212 area code number. (I did enjoy making people think I'd just moved to Manhattan.)

AT&T's CallVantage service began offering Maryland, Virginia and District area codes a few weeks ago. Just one price plan is available, $34.99 a month for unlimited local and long distance throughout the United States. That alone is likely to drive away some customers -- not everybody wants to spend or talk that much.

CallVantage was tougher to set up than Vonage. Activating the oversized adapter took longer, in part due to the grotesquely complicated setup screens its manufacturer, D-Link, inflicts on users who are expected to know that "Configure WAN IP Address" means "set up your Internet connection." I couldn't use my WiFi network until I rebooted the router after connecting it to the adapter.

But AT&T's call quality far surpassed that of Vonage. The adapter kept voice traffic flowing -- even if it sometimes slowed my downloads more than seemed necessary -- with only a few garbled words.

AT&T also outdid Vonage with its calling features, including such thoughtful free extras as a "Locate Me" option that will forward a call to other designated numbers until you pick up. A "Do Not Disturb" setting greets callers with a message that you don't want to be bothered unless it's an emergency (in which case they can press 2).

These features were also easier to set up -- to record a voice mail greeting, click a link on the CallVantage site and the service instantly rings your phone, allowing you to speak your greeting.

AT&T's biggest advantage, however, is its name. Would a company called AT&T wreck your phone service?

Packet8 finished in third place, even though it offered the best call quality overall and its $19.95 plan includes unlimited local and long-distance calls, Canada included.

The design of its adapter, with only one Ethernet port, makes it unusable on many home networks. It's clunkier -- if you forget to dial a "1" before every number, calls ring infinitely instead of at least bouncing you to an error message. Its calling features are far more limited: number-only Caller ID and no voice mail notification, let alone delivery, via e-mail. Fax and modem use, possible on the other services, isn't here. 911 calling costs $3 a month extra instead of being included in the base price.

These services aren't for everyone. If you make very few phone calls in the first place, you'll save money by getting a low-end land-line plan. If you make a lot of calls, you may still come out ahead by picking the right calling-card plan -- the VoIP services often had great international rates, as low as 2 or 3 cents a minute to Europe or Japan, but I found cheaper rates to other countries, such as India.

You should also consider whether, instead of spending $20 or $30 a month on VoIP, you would be better off using all or part of that cash to upgrade your cell phone's calling plan.

But for anybody looking to add a second or third phone line, or who routinely spends hours a month on long-distance calls, VoIP looks like the way to go. It's here, it works (well enough) and it will save you real money. And I expect it will get better in a hurry. You'll soon see cable or DSL modems with built-in VoIP circuitry, eliminating the confusing setup -- followed by VoIP phones that include their own WiFi receivers, so you can make calls using any available WiFi signal.

It's been a long time since local phone service was remotely interesting, but that's about to change.

Living with technology, or trying to? E-mail Rob Pegoraro at rob@twp.com.