Microsoft challenges 24 Avistar patents

LOS ANGELES (Reuters) - Avistar Communications Corp (AVSR.O: Quote, Profile, Research, Stock Buzz), a video conference equipment maker, said on Monday it has been notified that Microsoft Corp (MSFT.O: Quote, Profile, Research, Stock Buzz) has challenged 24 of Avistar's 29 U.S. patents.

Microsoft's request that the U.S. patent office reexamine the patents follows six months of negotiations between the two companies over the patent issues, Avistar said in a statement.

Avistar said the patent reexamination, if granted, could take six months to two years to complete. The company said it was confident it will "overcome" the reexamination request.

"We are frankly quite surprised by Microsoft's action given our lengthy discussions with them," Avistar Chief Executive Simon Moss said in a statement.

"Avistar is going through a significant organizational, technological, financial and cultural transformation. This seems to have been taken by Microsoft as a sign of weakness," Moss said.

Paul Carmichael, representing Avistar as its primary licensing advisor, said he expects the USPTO will agree that the challenge is without merit.

"Avistar's patent portfolio has been challenged previously in two significant litigations without effect," Carmichael said.

Microsoft could not immediately be reached for comment.

(Reporting by Gina Keating, additional reporting by Bill Berkrot in New York; Editing by Gary Hill and Braden Reddall)