Internet voice offers plenty of potential savings and productivity for small businesses. You can pay a fixed fee for monthly calling plans that include unlimited long distance coverage of North America and have the ability to program your phone to follow your movements without ever having to talk to a phone company representative ever again.

As an example, you have access to a wide range of business services that previously were only available to larger corporate users, including: call forwarding, multiple simultaneous rings (where an incoming call can be answered wherever it is more convenient), follow me (where incoming calls are routed to particular numbers at particular times of the day), and do-not-disturb. All are now part of most Internet voice service plans at no extra charge.

The downside is that your phone is more closely tied to your Internet service, which is less reliable than standard land-line phones. If your connection goes south, so does your phone service.

There are three basic different types of business Internet voice service. Most providers offer monthly plans that start at $50 per line including Verizon’s VoiceWing for Business, AT&T’s CallVantage, Packet8.com’s Virtual Office and various business phone plans from other high-speed Internet providers that are basically a two-line version of their consumer service. All of those offer minimal features and are designed for a single office location. They also make use of standard or analog telephones that you buy in any office supply store.

The next step up from these plans are ones from what is called a “hosted service” that is provided by VirtualPBX.com, M5Net.com, Bandwidth.com and numerous others. Basically, those providers rent you space on their systems and connect up your offices via high-speed Internet lines. They typically start at several hundred dollars a month but also include a high-speed Internet connection that you can use for other applications such as Web and email.

The most expensive level is buying your own Internet voice PBX, or phone switch. That can cost more than $1,000 for the switch, and more than $500 a month for the various plans, and is designed for larger offices. Both Linksys and D-Link offer less expensive switches but require configuration and help from a consultant.

Here are some questions to ask before you decide on which business plan is the right one for you.

1. How many incoming phone numbers do you need?
If you have inbound fax lines and analog answering machines that you can’t or won’t get rid of, you need to figure out a plan for either keeping these lines or substituting work-arounds to continue using these phones. The various Internet voice services also vary in their support for inbound analog lines, something that is also worth investigating.

This is also a good time to calculate how many new digital phones you’ll need to buy. Given that prices are rapidly dropping on phones, it doesn’t make much sense to buy any more than what you need at first.

Also, you will want to investigate whether you can keep your existing inbound office number(s) when you move to the new Internet voice system. Some of the providers can move your numbers in some locations, and some can’t. It is worth checking: There are many reasons why they can’t be transferred – some political, some technical – but if you need to keep your existing numbers you may have to continue to pay your local phone company for minimal service for these lines.

2. How many different offices will you want to tie together under a single plan?
If you are just buying service for a single location, start with the simplest plans and see if they will meet your calling needs. Things get complicated quickly as you involve having multiple, geographically distant offices that can be connected via one central office number. Do you want everyone in these offices to have their own extension, to give the impression that they are all working out of the same “office?” That is what providers such as VirtualPBX.com are geared toward.

3. What kind of high-speed Internet service do you presently have to your office?
The type of connection is critically important to your experience with Internet voice business service. Voice quality is directly related to things such as network latency and packet delays that can cause drop-outs and degrade the overall audio of your calls. You will need to hire someone who specializes in Internet voice applications or spend some time understanding these issues and testing your existing connection. If you hire an Internet voice consultant, he or she should be able to do that for you.

Before you attempt anything, a good place to start is with TestYourVOIP.com, a free service that can indicate whether your connection is fast enough to support voice applications. Ideally, you want to purchase what is called a T-1 line for an office that has more than five people.

4. Do you need to upgrade your office wiring and network?
If you are working out of a home office or a place where you can wire up your phones, then you are in better shape for Internet voice, because you will probably need to do some wiring. Internet phones require more recent and higher quality network wiring than your average computer. Again, your voice consultant should be able to make the appropriate recommendations, but realize that this could be part of the cost of the overall job, and it could get pricey if you have to replace switches, routers and other network gear.

A second issue is whether you want to deploy Power over Ethernet switches to power your new digital phones. Sure, you can plug the new phone into a standard AC wall socket, but that might not be convenient or as reliable as having them get their power from a central wiring closet that has battery backup in case of power failures. Here again, you may be looking at buying new switches to handle that.

5. Do you want to make or receive calls from your laptop?
One of the big advantages of Internet voice is being able to take a phone and connect it anywhere on the Internet and have it work as if it is sitting in your office. But to get to this point, you need equipment that can support remote users. In some cases, you will need a phone that has a built-in Virtual Private Network client (Snom.com sells such IP phones, for example) to connect to your corporate network, just like a remote PC user uses. You’ll also need a good quality USB headset to make the calls and have software that works with your Internet Service voice provider.