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Statements in Specification and Prosecution History Limit the Invention and Claim Scope

February 03, 2004

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Last Month at the Federal Circuit - March 2004

Judges: Lourie (author), Bryson, and Rader (dissenting)

In Microsoft Corp. v. Multi-Tech Systems, Inc., No. 03-1139 (Fed. Cir. Feb. 3, 2004), the Federal Circuit affirmed several claimconstruction rulings and a final judgment of noninfringement on three patents owned by Multi-Tech Systems, Inc. (“Multi-Tech”).

This opinion reviewed rulings on three patents directed to personal computer-based systems and methods for simultaneously transmitting voice and/or computer data to a remote site over a telephone line. The opinion focuses on the construction of the terms “sending,” “transmitting,” and “receiving” data packets, and whether these limitations are restricted to communications over a telephone line or whether they may encompass communications over a packet-switched network such as the Internet.

The Federal Circuit reviewed the intrinsic evidence and concluded that the claims must be limited to the telephone-line operation, not just because that was described as a preferred embodiment, but because it was broadly described throughout the specification, including the summary of the invention section, as the whole invention. The Court construed these limitations to require that the claimed data packets traveled directly from a local site to a remote site (and vice versa) over a telephone line and not a packet-switched network, concluding that it could not construe the claims to cover subject matter broader than that which the patentee itself regarded as comprising its inventions and represented to the PTO.

The Federal Circuit also found support for its ruling in the prosecution history, pointing to statements in a summary of the invention in the prosecution history that again specified the use of a telephone line. The Court applied its construction to the patent corresponding to the prosecution history containing these remarks, two subsequent but related patents, and even a prior issued but related patent. The Court noted that it must take the patentee at its word and will not construe the scope of the patent claims more broadly than the patentee itself clearly envisioned.

The Federal Circuit also construed several other claim limitations and confirmed the final judgments of noninfringement.

Judge Rader dissented, concluding that the majority was improperly limiting the claims when no clear disavowal of subject matter existed in the specification or prosecution history.