A firm that holds patents for technology used in Internet voice calling is suing search giant Google for US$5 billion over its Google Talk instant-messaging client.

Rates Technology (RTI), a small, New York company that holds patents to telecommunications technologies but does not sell products, filed suit in October against Google, claiming the company is using two technologies RTI has patented but has not licensed.

The case was filed in the US District Court for the Eastern District of New York in October, but surfaced first in published reports this week.

Google uses the two technologies, which are for minimising the cost of long-distance telephone calls, in the VoIP service of its Google Talk VOIP client.

"Google's wrongful acts have damaged and will continue to damage RTI irreparably, and RTI has no adequate remedy at law for those wrongs and injuries," the company said in court papers.

Google has been notified of its patent infringement and given a chance to remedy the situation by licensing technology from RTI, "but has refused to do so," the company said in its court filing.

RTI is demanding a trial by jury to settle the suit, according to court papers.

Rich Tehrani, VoIP industry watcher and president of Technology Marketing, has written about RTI in several entries his VoIP blog.

In an e-mail interview Friday, Tehrani said that RTI founder and President Jerry Weinberger invented least-cost routing technology that allows a phone system to find the cheapest carrier prior to placing a phone call. This technology is part of what enables VoIP calls to work. Other companies, such as Cisco Systems and Lucent Technologies, have already paid RTI to use its patented technology, he said.

Google spokesman Steve Langdon said the company believes the lawsuit is "without merit" and plans to fight it.

RTI could not be reached for comment Friday.