In Microsoft Corp. v. Multi-Tech Sys., Inc. (Fed. Cir. February 3, 2004), the Federal Circuit narrowed the claim coverage of a patent by remarks made during prosecution of a pending patent application even though the patent had already issued.

The issued patent and the patent application, owned by Multi-Tech, had identical specifications, shared the priority date of the same parent application, and were directed to simultaneous transmission of voice and data over a telephone line to a remote site.  Representative claim limitations at issue follow:

A method for communication of voice and data information, comprising the steps of:
…
transmitting the outgoing packet stream;
receiving multiplexed incoming data which contains incoming computer digital data packets multiplexed with the compressed incoming digital voice data packets;
…

First, the court determined that the language of the specification led to the “inescapable conclusion” that the claimed transmission and reception of packets between the local and remote sites must occur directly over a telephone line.  Under this construction, Multi-Tech’s claim language did not encompass Microsoft’s activity of data transmission over a packet-switched network such as the Internet.  In so characterizing the claims in view of the specification, the court relied on SciMed Life Sys., Inc. v. Advanced Cardiovascular Sys., Inc., 242 F.3d 1337 (Fed. Cir. 2001):

When the specification makes clear that the invention does not include a particular feature, that feature is deemed to be outside the reach of the claims of the patent, even though the language of the claims, read without reference to the specification, might be considered broad enough to encompass the feature in question.

Second, the court reviewed the prosecution history of the patent application.  In a first office action, the patent examiner had rejected all the claims as obvious.  Multi-Tech had filed a response to the first office action with remarks that:

• attempted to distinguish the invention from the prior art by arguing that the claimed voice packets proceeded directly from the communications system through the telephone line to a receiving communications system at the other end of the line; and
• described the specification as disclosing a communications system that operates over a standard telephone line and establishes a point-to-point connection between telephone equipment on each end of the line.

In a second office action, the patent examiner again had rejected the claims as obvious.  Responding, Multi-Tech had amended the claims to recite a modem and filed remarks that the voice packets were sent through a point-to-point modem connection between the local and remote sites.  The court understood Multi-Tech’s remarks to limit the claimed invention to communications over a telephone line, not encompassing Microsoft’s communications over a packet-switched network such as the Internet.

Multi-Tech’s remarks during prosecution of the patent application were relevant to an understanding of the identical specification of the issued patent.  Multi-Tech cited Georgia-Pacific Corp. v. United States Gypsum Co., 195 F.3d 1322 (Fed. Cir. 1999), but unsuccessfully argued that the statements made during prosecution of the patent application should not be applied to the issued patent because the patent examiner could not have relied on those statements in allowing the already-issued claims.  On the one hand, replied the court, the issued patent claims are not “bound by” statements made during prosecution of a later application.  On the other hand, and stated by the court to be not contrary to Georgia-Pacific, any statement of the patentee in the prosecution of a related application as to the scope of the invention is relevant to claim construction.  The relevance is enhanced when made in an official proceeding in which the patentee has every incentive to exercise care in characterizing the scope of its invention.

Based on the analysis of the claim language, the specification, and the prosecution history, the majority of the court concluded that the “transmitting” and “receiving” claim limitations required the direct transmission of data packets between the local and remote sites over a telephone line, and did not cover the use of a packet-switched network such as the Internet.  So, Microsoft was not liable to Multi-Tech for patent infringement.

Recommendations:

• Take care in coordinating prosecution among all patents and patent applications with common specifications and priority dates, since any and all prosecution remarks potentially can narrow claim coverage, even for issued claims.
• Take care in preparing the specification to disclose exemplary implementations without emphasizing extra details in characterizing the scope of the invention.

February 17, 2004

Text Copyright © 2004 Bob Brill et al.

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