AT&T alleges that Microsoft used its technology in its TrueSpeech software, which codes and decodes voice signals, and in NetMeeting, which is used for videoconferencing. These programs are included in Microsoft’s Windows ME, the current version of Windows for consumers, and on Windows NT’s information server. Some of NetMeeting’s capabilities will also be used in Windows Messenger, the instant messaging service that will tie in to Microsoft's next version of Windows, Windows XP.
The lawsuit claims AT&T warned Microsoft of the patent infringement in April 1999, and although AT&T allegedly offered to licence the patent to Microsoft, this offer was apparently rejected.
AT&T has asked for a judgement against Microsoft, as well as damages and legal fees.