Opinion ID: 785085
Heading Depth: 2
Heading Rank: 4

Heading: The Speaker Phone Limitations

Text: 55 Multi-Tech next argues that the district court erred in its interpretation of the terms hands-free speaker phone, full-duplex speaker phone, and full-duplex hands-free speaker phone in claims 1, 2, 5, 7, and 13 of the '627 patent. Multi-Tech maintains that the court erred in limiting the speaker phone limitations to traditional speaker phones because the claim language discloses a speaker phone that is simply a microphone and a speaker, regardless of its physical housing. Multi-Tech further argues that the court improperly construed the full-duplex speaker phone limitations to require echo cancellation, an optional feature disclosed in the specification. 56 Microsoft responds that, according to its ordinary meaning, the term speaker phone must include structure beyond just a microphone and a speaker in order to be a telephone. Microsoft also argues that the term full-duplex speaker phone must include echo cancellation because the specification states that the use of a microphone and a speaker necessitates the use of an acoustical echo cancellation algorithm to prevent feedback from destroying the voice signals. 57 We agree with Multi-Tech that the district court construed the speaker phone limitations too narrowly. Neither the claims nor the specification describes any physical housing that must comprise the hands-free speaker phone. Claim 1 of the '627 patent simply recites a hands-free speaker phone with a microphone and a speaker. '627 patent, col. 46, ll. 37-39. Dependent claims 2 and 5 further require that the hands-free speaker phone include, respectively, a deskset microphone and a deskset speaker, id. at col. 46, ll. 55-57, or a headset microphone and a headset speaker, id. at col. 46, l. 66 to col. 47, l. 1. Claim 7 recites a full-duplex speaker phone, id. at col. 47, l. 7, and claim 13 recites a full-duplex hands-free speaker phone, id. at col. 48, ll. 22-23. Moreover, the specification repeatedly refers to three alternative telephone interfaces: a handset, a headset, and a hands-free microphone and speaker. E.g., '289 patent, col. 8, ll. 20-21 & fig. 3. It consistently describes the hands-free interface as simply a microphone and a speaker. To require more structure would impermissibly exclude a preferred embodiment from the claim limitation. Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1583 (Fed.Cir.1996) (stating that it is rarely, if ever, correct to interpret a claim to exclude a preferred embodiment). We therefore conclude that the term speaker phone requires no physical structure beyond a microphone and a speaker. 58 We agree with Microsoft, however, that the district court properly construed the speaker phone limitations to require the use of echo cancellation. Although the language of the independent claims does not expressly refer to echo cancellation, the specification provides that the use of the speaker and microphone necessitates the use of an acoustical echo cancellation algorithm to prevent feedback from destroying the voice signals and that a line echo cancellation algorithm is needed no matter which telephone interface ... is used. '289 patent, col. 31, l. 67 to col. 32, l. 4 (emphases added). Those statements clearly mandate the use of acoustical and line echo cancellation. We therefore conclude that the speaker phone limitations require the use of echo cancellation. 59