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The importance of a carefully drafted patent specification(07/15/10)
Telcordia Technologies, Inc. v. Cisco Systems, Inc. (Fed. Cir. July 6, 2010).
Telcordia Technologiesshows how the specification of a patent application can limit or even invalidate the claims that are issued in a patent. First, the Court of Appeals for the Federal Circuit construed the asserted claims of Telcordia Technologies’ U.S. patent 4,893,306 for “Method and Apparatus for Multiplexing Circuit and Packet Traffic” to require that only one packet of data be placed into an empty payload field of a frame even though the claims contain no such limitation, on the grounds that only one packet per frame is discussed in the specification of the patent, invoking a “clear intent to limit the claim scope.” Cisco Systems was not guilty of infringement because the specification so limited the asserted claims that they did not read on the Cisco Systems methods. The specification did not have to be written this way and Telcordia lost valuable patent rights as a result.
Second, the Federal Circuit decided that the asserted claims of Telcordia’s U.S. patent 4,835,763 for a “Survivable Ring Network” were not invalid for indefiniteness in reciting a “monitoring means.” This was a “means plus function” term in which the claim is limited to structure recited in the specification and structural equivalents thereof that perform the recited function. Two judges, including Chief Judge Randall Rader, found the corresponding structure in the specification to be the “controllers,” largely by a process of finding the only structures that could possibly perform the monitoring function. Judge Prost dissented on this issue because she believes that the specification must clearly link the structure of the controller with the claimed function, presumably by saying so explicitly. Had Judge Lourie agreed with her, these claims would have been invalidated. Telcordia came close to losing patent rights because the specification did not explicitly identify the structure that performed the claimed function. It is best that patent claims not be written using a “means plus function” format, for at least this reason, and currently fewer and fewer patents are issued with claims written this way.
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