The good news about using a VoIP Internet telephone service is that it is rich in features and less expensive than the traditional circuit-switched telephone service already in your home.

But VoIP is not the same as your traditional home phone and, if you expect it to be, you'll get a surprise. Plus, to get it to feed your entire household like your current phone service, it won't be a self-install.

Selecting your VoIP vendor is one of the easy parts because the risk is so low. Most of the service providers have inexpensive -- almost free -- trial offers. I've been running with Verizon VoiceWing and Vonage side-by-side on different lines.

Setup

To use VoIP, in addition to the VoIP service, you'll need a standard telephone, a broadband Internet connection (cable or DSL) and a phone adapter box to connect the two together.

Hooking them together is a snap for a single phone. Generally, after you have signed up for your VoIP service, either by phone or by Internet, turn off your cable or DSL modem, depending on what you have, and then connect the phone adapter box to your Internet network -- either directly through your modem or your router if you are using one -- using standard network wire (the directions will be very clear about this).

Plug your phone into the phone jack in your phone adapter and turn everything on. In two to five minutes, you'll be able to get dial-tone from your new VoIP number.

Now you can use your VoIP phone just like a traditional phone. You also can use the advanced services, either by pressing buttons on your phone or by logging in to a Web interface. I like the Web interfaces because you can see a log of your calls and play any voice-mail message that you want -- even out of order -- using standard play, stop, rewind and fast-forward buttons.

Which service do I choose?

At a minimum, expect your new phone service to provide a suite of services that includes online call logs, caller-ID, call waiting, voice mail, call forwarding and the ability to be notified by e-mail when you receive a voice mail.

Also expect to be able to log into the Internet to check your messages, although each service has customized the way its Web interface works so they look and feel very different. Beyond the basic services, you get different types of services from each vendor.

Verizon's caller ID works like the caller ID on your cell phone. Instead of looking up the name and number from a central database, it looks at your own address book, so the name reflects how you have it entered. For callers who aren't in your address book, it allows you to match the number with a listing in Verizon's white or yellow pages.

AT&T CallVantage includes a "Locate Me" service that rings your other telephone numbers in an order of your choosing so it can find you elsewhere if you don't pick up your CallVantage line. Several providers include a simultaneous ring service, so you can pick up your call remotely if you're not near your VoIP phone.

Comcast also offers its own brand of telephone service over its cable connection, but its VoIP offering is not yet offered in all markets -- and Pittsburgh is on the list of cities to which it is coming.

Not quite traditional telephone

While VoIP gives you additional features not found in Alexander Graham Bell's telephone system, you also may miss some traditional items.

Currently, VoIP providers are striving to provide full-service 9-1-1 emergency service, but most of them are not there yet. The FCC has already mandated that they need to have it this year, and the phone companies are busy working with them to fulfill the FCC requirement. Until then, you'll need to register your street address every time you move your phone or the 9-1-1 records won't be correct.

You also shouldn't expect your VoIP service to be available at the near-100 percent rate that comes with traditional phone service. If your power goes out, so will your phone adapter. If your broadband connection goes out, so does your phone.

Most VoIP services will automatically send your calls to a different phone if your VoIP goes out, helping you make sure that you get the calls you need. Lingo goes a step further by including an extra outlet in your phone adapter that lets you also connect it to a standard phone line. This could come in handy when your VoIP line is your second line.

The quality of VoIP is quite good. Most people won't be able to tell the difference on most phone calls. But if you have a discerning ear, you'll hear the difference -- and occasional calls won't sound as good no matter how bad your ear is.

The installation conundrum

If you want to use your phone in a single room, you can easily install it yourself as long as your network cable is long enough to reach from your broadband connection/router to your phone adapter. You can even take your phone on the road with you, as long as you take the adapter and have broadband access at the second location.

However, mirroring your current phone system with multiple phones throughout the house is a bit more complex. It requires you to remove the incoming line from your old telephone company, then hooking the phone adapter into that same point.

Even the techies don't want to take the trouble to do that. Instead, they call for an installer. As an alternative, the VoIP service providers suggest purchasing a wireless phone that has multiple handsets.

Expect the unexpected

Even as VoIP is starting to seem more like traditional phone service, it's still new technology. So expect some strange things to happen.

On my Vonage line, I constantly hear a stutter dial tone when I pick up, as if I have a voice mail waiting -- even when there is no voice mail in my inbox.

My Verizon VoiceWing account manager often tells me that it can't show me my voice mail because I have cookies disabled, when in fact, that is not the case.

I'd expect these and other issues to get resolved as the technology gets more refined. In the meantime, VoIP offers an interesting alternative to traditional phone service -- especially when you plan to use it as a second line.

Cheap, Cheaper or Cheapest

You might get so carried away by the savings and ease of switching that you churn your accounts, moving from service to service to take advantage of free start-up months and lower rates.

New Jersey consultant Momentum Technology Partners' Mike Centrella cautions that users shouldn't change services just to get an extra $3 to $5 in savings. They should look at the features specific to their needs -- and go with the service that offers the closest match. The savings is a bonus.

I'd add that the nuisance factor of changing services is another good reason to pick one and stay put, especially if you want to keep the same number. While you can take it with you, it's not always easy or quick. In the meantime, all the services should get better, no matter which direction the prices head.