Microsoft challenges 24 Avistar patents

LOS ANGELES, Feb 25 (Reuters) - Avistar Communications Corp. AVSR.O, 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. (Reporting by Gina Keating; Editing by Gary Hill)