众所周知，用手机拨打国际电话的费用极其昂贵，通常只被可报销的商务人士使用。不过，最近一家刚刚成立2年的i2Telecom公司计划在本月推出一款类似调制解调器的设备，该设备能够通过连接在互联网上的路由器将国际电话转换成本地电话。

　　无独有偶，最近另一家名为Skype的技术公司也发布了一个免费软件，安装该软件的掌上电脑可以转变成通过互联网打电话的手机。

　　Mobile phone users have in recent years enjoyed plummeting rates for local and long-distance calling thanks to new technology and fierce competition among cellular companies. Now several entrepreneurs want to use Internet technology to reduce to pennies the cost of using cellphones to call overseas.

　　Dialing internationally on cellphones is typically so expensive that the service is used mostly by businesspeople on expense accounts. But a two-year-old company called i2Telecom, based in Boca Raton, Fla., plans to release a modemlike device this month that effectively turns an international call into a local one by routing it over the Internet.

　　Another company, Skype Technologies, recently introduced free software that lets people turn hand-held computers into mobile phones by sending calls over the Internet.

　　Both ventures take to a new level the market-disrupting potential of the technology called voice over Internet protocol. And both will be on center stage at VON Canada 2004, a conference on Internet telephony opening in Toronto tomorrow that will bring together telecommunications heavyweights like Nortel and Bell Canada, as well as dozens of entrepreneurs and media companies.

　　Using the Internet to route calls could significantly reduce costs, in part, because data and voice traffic will use a single network, advocates say. The shift presents a threat to traditional telephone companies, which have invested heavily in their networks.

　　Now upstart companies like i2Telecom hope to shake up the cellphone industry in much the same way that Internet calling is challenging long-distance carriers.

　　"It puts the cellphone providers under attack for the first time," said Rick Scherle, vice president for marketing at i2Telecom. "The land-line guys have been wrestling this technology," he said. "We're telling the cellphone guys that you have to grapple with it now, too."

　　I2Telecom's product, the InternetTalker MG-3, is about the size of a hand-held electronic organizer and will cost less than $100. Once connected to a phone and a broadband Internet connection, the router can be programmed to recognize three phone numbers, including those of cellular handsets.

　　When cellphone users call the phone where the InternetTalker is installed, they receive a second dial tone and access to an Internet calling network from which they can dial any phone number in the world. Instead of paying, say, $1.75 a minute to call London directly by cellphone, people using the InternetTalker would pay for only the local call to their home and just 3 cents a minute, the price of an Internet call on i2Telecom's network. Users can call other i2Telecom subscribers free.

　　Curiously, cellphone calls routed through the Internet to other cellphones have cleaner signals than cellphone calls sent directly to other cellphones, Mr. Scherle said. Engineers at i2Telecom, who discovered this accidentally, say they believe that by redigitizing the signal, extraneous noise is eliminated.

　　The new service, however, will not eliminate roaming charges when cellphone users are outside their coverage area. Nor is it likely to offer much savings on long-distance calls if a user has a cellphone plan with unlimited long-distance calling. But the InternetTalker could erode the amount of business cellular carriers have in connecting international calls. It could also hurt overseas phone companies that rely on fees from American carriers to connect international calls.

　　"There's a huge impact on the international carriers because a lot of carriers subsidize their capital spending with high fees from international voice traffic," said Daniel Briere, the chief executive of TeleChoice, a consulting firm in Mansfield Center, Conn.

　　Many long-distance carriers have tried to prevent Internet calls from coming into their country, Mr. Briere said, but that requires checking every data packet traveling over their networks, an impractical task.

　　Wireless carriers in the United States say Internet-based cellular calls will not affect their business because the vast majority of the calls they connect are within North America. They also say the quality of calls traveling over their networks is superior to that of calls routed over the Internet.

　　"We're a business that trades on quality," said Edward Salas, vice president for network planning at Verizon Wireless. He added that while the Internet technology "has been there for some time, I'm not sure we're ready for prime time to make it a mainstream way of moving traffic." Mr. Salas said the wide-scale use of that technology is about 10 years away.

　　Skype, a company founded by the creators of Kazaa, the digital music sharing software, also hopes to create software that can route Internet calls from mobile phones. But for now, the company is focused on distributing software that lets people place Internet-based calls through wireless connections to hand-held computers that use the Microsoft PocketPC operating system. Once the software is installed, users attach a headphone to the hand-held computer to make calls.

　　To use the Skype technology, both the caller and the recipient need the software. But the company plans to make it possible for callers to reach people outside the Skype network. Niklas Zennstrom, Skype's chief executive, said Internet technology eliminates any price difference between calls traveling one mile or thousands of miles. "The concept of national borders," Mr. Zennstrom said, "is disappearing because on the Internet there are no borders."