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Internet Telephony Explained

Internet telephony is broken down into three main categories consisting of PC-to-PC telephony, PC to Phone, and Phone to Phone. We describe each type of Internet telephony application and how to use it.

PC-based telephony is a widely used option for communications. Internet telephony describes a category of hardware and software products that lets you use your Internet connection as the transmission medium for sending and receiving telephone calls. For users who have free or fixed-price Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. This is because the Internet connection service is already paid for.

Types of Internet telephony Applications

There are many Internet telephony applications available. Some, like Microsoft NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products.

Internet telephony is broken down into three main categories consisting of PC-to-PC telephony, PC to Phone, and Phone to Phone. In this Webopedia Quick reference article we'll describe each type of Internet telephony application and offer tips on how to use it.

PC-to-PC Calling

PC-to-PC telephony enables you to call another person who is online at the same time you are, using the same telephony client (or one that is compatible). To use your PC to talk to another person through his PC, you'll need compatible software, a microphone and speakers (or alternatively, a PC headset) and Internet access. PC-to-PC telephony is free — you should never be required to pay to make these calls, regardless of where the person you want to communicate with is located.

PC-to-PC telephony lacks the crisp clear quality that you typically get with regular phone lines, but of course the trade-off is that you won't pay to use it. This makes it a popular choice for family and friends who live outside of each other's local telephone calling access.

Today there are myriad software choices, many of them free, which offer basic PC-to-PC calling. It's important to remember that you will need compatible software with the person you are calling, so deciding on a free program before using PC telephony is a good idea. For those who use Instant Messaging programs such as Google Talk, AOL AIM, Yahoo! Messenger or MSN messenger, these communication platforms do have voice communication services built in. Skype, and SharpVoice are other free programs that you can use.

Many free PC-to-PC telephony programs also offer PC-to-Phone communications as well. Most PC-to-PC telephony software works like several of the popular Instant Messaging clients. Good PC-to-PC telephony software clients allow you to keep a contact list, and when that contact is online, you simply click to begin a voice conversation, similar to initiating a text instant message. Some clients will allow you to initiate a group or multiple-user PC-to-PC telephony session, while others include this feature only when you upgrade from the free version.

How Pc-to-PC Calling Works: The client software converts transmitted speech into data packets and routes it over the Internet. The receiving client turns the data packets back into voice signals that are heard through the speakers or headphones on the receiving end.

PC-to-Phone Calling

PC-to-phone telephony allows you to make calls from your computer to regular telephones. The technology is similar to PC-to-PC calling. While this is a service you pay for, it's usually cheaper than using your long distance telephone provider. To use PC-to-Phone services, you need to have the same equipment used for PC-to-PC calling;  a microphone and speakers (or alternatively, a PC headset), and Internet access.

How PC-to-Phone Works: The PC phone user's PC acts as the originating gateway, which converts the voice transmission into data packets onto the Internet. At the end gateway provided by the software distributor, the data packets are converted to voice signals and routed to the Public Switched Telephone Network (PSTN). The PSTN then routes the call to the receiver's telephone, as it would with regular telephone calls.

Phone-to-Phone Calling

A relatively new type of Internet telephony service, which is quickly gaining in popularity with consumers and business. Phone-to-phone telephony also allow telephone calls to be placed over the Internet, but it differs drastically from the other types of Internet telephony. Phone-to-phone telephony does not require users to have special software, or even a computer to use it. Phone-to-phone uses traditional telephones on both ends.

To make phone-to-phone telephony calls, you need to have an Internet Telephony Service Provider (ITSP). The ITSP will have gateways in different areas around the world. When you place a call, that call is routed over the Internet to a gateway located the closest to the receiving party. The gateway will then send the call over the PSTN to the receiving party's regular telephone.  Because much of the transmission for the call takes place over the Internet, Phone-to-phone telephony is cheaper than using a regular telephone service provider. Your ITSP will be the one who handles your subscription and billing

How Phone-to-Phone Calling Works: Users with Internet telephone connections place a call from their landline phone. The voice signals are digitized, compressed and converted to data packets. When the data packets arrive at the gateway, they are converted back into voice signals. Once converted, the voice signals are then transmitted through the local PSTN to the receiver.

Based in Nova Scotia, Vangie Beal is has been writing about technology for more than a decade. She is a frequent contributor to EcommerceGuide and managing editor at Webopedia. You can tweet her online @AuroraGG.

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