These companies provide services that enable low-cost telephone calls over the Web. This service, commonly referred to as Web telephony (IP telephony) enables customers to make regular phone calls or send faxes to anywhere in the world.
Here’s how this type of call works: The call originates from a telephone and is routed to a Web Telephony gateway, which connects the telephone network to the Web. The call then travels across the Web to its destination, where it is routed to another Web Telephony gateway that connects the Web back to the telephone network. Then the call is directed to the telephone at the destination.
IP telephony rates are generally much lower than calls placed over regular long distance telephone networks. A one minute call to the US and Western Europe for example costs around $0.80, a one minute call to Moscow costs $0.11, A call to Baltic countries is $0.70 per minute. Since your call is goes over the Web, call quality can vary greatly and is subject to traffic and connection quality.
No special equipment is needed to use IP telephony. You just need to have a regular touch-tone phone and to purchase a special pre-paid calling card from an IP telephony provider. The cost of each call is deducted from your card. Calling cards are valid for unlimited periods of time and are different prices.