protective circuitry, to permit the simultaneous connection to all three devices.
Defendants also point to the specification and its drawings as limiting claim 34 to a system simultaneously attached to all three devices. Without dispute from R2, defendants argue that the cable component of the invention, the "cable means," is presented as a "means-plus-function" limitation. 35 U.S.C. section 112, paragraph 6 restricts a "means-plus-function" limitation to equivalents of the structures provided in the specification to carry out the function. See Valmont Industries, Inc. v. Reinke Mfg. Co., Inc., 983 F.2d 1039, 1043 (Fed. Cir. 1993). Defendants contend that these specifications only set forth a structure capable of simultaneous connection to all three devices.
Third, defendants argue that the prosecution history reveals that the inventor disavowed a system incapable of simultaneous connection in order to obtain the patent grant from the Patent Examiner. The inventor, Heath, originally submitted 117 claims and 28 figures in relation to the '998 patent. In response, the Examiner issued a requirement for restriction asserting that these claims were "specific to more than one species of the generic invention," and identified the species by reference to the drawings. Pursuant to 35 U.S.C. section 121, the Examiner directed Heath to elect a single species. Heath elected the species disclosed by figures 1 and 28, depicting the system simultaneously connected to all three devices, and 45 of the 117 claims that Heath asserted read on the species. Defendants argue that, through this election, Heath abandoned any claims covering systems incapable of connection to all three devices as depicted in figures 1 and 28.
R2 responds that the "single common interface" refers to the multifunctional electrodes, connector plugs and sets of cables that may be combined in various permutations to permit attachment to any of the three devices, but not necessarily to two or three devices at once. In support, R2 argues that defendants' interpretation would render claim 34 redundant of the '998 patent's other independent claim that expressly provides for the "simultaneous" connection to two or more devices. With respect to "cable means," R2 argues that the specification discloses an embodiment that includes a system that only selectively attaches to any of three devices. Finally, R2 contends that Heath abandoned only claims related to the electrodes alone, the cables alone, or to systems using only the electrodes and one or two types of devices irrespective or their ability to selectively connect to the other devices. Accordingly, R2 interprets the inventor's remarks to elect claims related to a species that contemplates both the selective connection of the multifunctional electrodes with the three devices as well as one including the connectors and circuitry necessary for simultaneous connection.
2. Interpretation of Claim 34
a. The Claims Themselves
In contrast to defendants' reading, the plain language of claim 34 does not indicate a cardiac system including cables and protective circuitry permitting simultaneous connection to all three cardiac care devices. Claim 34 describes an "interface" capable of connecting "a monitoring device, therapeutic device or a stimulating device" to the patient. This interface is comprised of a disposable electrode set, a connector plug, connector means and cables. Neither the monitoring device, therapeutic device nor stimulating device, themselves, are presented as elements of the invention. Rather, electrodes, connectors and cables constructed for connection to these devices comprise the invention. The "cable means" is defined as intended for "selectively connecting the monitoring device, therapeutic device or stimulating device" to the electrode sets. None of the limitations refer to simultaneous connection or use. Thus, the "selective" character indicates that the "cable means" refers to any of three cables that may be attached at any one time to employ the desired device.
In contrast, another independent claim of the '998 patent, claim 1, specifically describes a system using connectors and protective circuitry for "simultaneous" connection. Claim 1 and claim 34 read substantially similar in providing the fundamental limitations on invention. Instead of calling for a "cable means," however, claim 1 requires the use of an "interrelating means" that provides for "the simultaneous connection of said electrode elements to at least two said devices." Claim 1 also requires the additional element of a "protective means associated with said interrelating means for selectively permitting desired combinations of . . . [the three devices] . . . to be simultaneously connected to the patient solely through first and second said electrode elements." Thus, in contrast to claim 34, claim 1 explicitly refers to a system using cables and circuitry that permit the simultaneous connection of two or more devices.
Under the interpretive doctrine of "claim differentiation," an interpretation of a claim should be avoided if it would make that claim read identically to another claim in the same patent. Autogiro, 181 Ct. Cl. 55, 384 F.2d 391, 404; see Tandon Corp. v. U.S. Int'l Trade Comm'n, 831 F.2d 1017, 1023 (Fed. Cir. 1987); DMI, Inc. v. Deere & Co., 755 F.2d 1570, 1574 (Fed. Cir. 1985). Defendants respond that "claim differentiation" only restricts the reading of express limitations from a dependant claim into an independent claim, and is not applicable to the comparison of two independent claims in the same patent. As defendants note, the doctrine has greater argumentative force when an interpretation would render an independent claim identical to its own dependant claim. See Hormone Research Foundation, Inc. v. Genentech, Inc., 904 F.2d 1558, 1567 n. 15 (Fed. Cir. 1990) ("It is not unusual that separate claims may define the invention using different terminology, especially where . . . independent claims are involved"). Dependant claims are generally used to narrow an independent claim by describing the disclosed invention with greater detail, and so, stricter scope.
However, defendants cite no precedent limiting "claim differentiation" to this context. Cf. id. (interpreting independent claims as identical where specification and file history require that interpretation). More importantly, the Federal Circuit has applied the doctrine to interpret one independent claim in light of another independent claim. See Uniroyal, Inc. v. Rudkin-Wiley Corp., 837 F.2d 1044, 1055 (Fed Cir. 1988); Caterpillar Tractor Co. v. Berco, SPA, 714 F.2d 1110, 1116 (Fed. Cir. 1983). Defendants have not pointed to any distinction between claim 1 and claim 34 other than claim 1's limitations describing an "interrelating means" and "protective means" and claim 34's "cable means." Therefore, the redundant character of defendants' interpretation of "cable means" further supports R2's more natural interpretation of "cable means."
This interpretation of claim 34 does not render the terms "single common," modifying the "instrument-to-body interface," superfluous. As a general matter, the fact that "single common instrument-to-body interface" appears in the preamble of claim 34 does not necessarily indicate that it imposes a structural limitation on the claim. See Gerber Garment Technology, Inc. v. Lectra Systems, Inc., 916 F.2d 683, 688 (Fed Cir. 1990) (description in preamble constitutes limitation only if necessary to precisely define and give meaning to the invention set forth in the formal limitations). Regardless, the "single common interface" refers to the fact that the same disposable electrode set, connector plug and set of cables are used regardless of the device selected. The fact that the specific cable connected at any one time is different does not contradict the description of a "single common" interface between the patient and the device chosen. The other elements of the actual entity used, the disposable electrode set, remain the same. Only the final element of the cable used at any one time is altered.
b. Mean-Plus-Function Analysis
Defendants argue that 35 U.S.C. section 112, paragraph 6, restricts claim 34 to devices capable of simultaneous connection. Instead of reciting a particular structure, a "means-plus-function" limitation describes an element of a product claim as "a means or step for performing a specified function." 35 U.S.C. § 112 P 6. In contrast to the usual interpretive rule against reading limitations from the specification into the patent claims, see Constant, 848 F.2d 1560, 1571, a "means-plus-function" limitation is restricted to the description, and equivalents thereof, of structures set forth in the specification intended to carry out the function described in the limitation. Valmont, 983 F.2d 1039, 1043-44. The parties do not dispute that the "cable means" constitutes a "means-plus-function" limitation. Claim 34 never describes the structure of its "cable means" other than to note its connection to the connector means and the cardiac care devices. If the specification only presents the structure of a "cable means" that is capable of simultaneous connection, then this limitation must be read into claim 34 regardless of the tenant of the "claim differentiation." Laitram Corp. v. Rexnord, Inc., 939 F.2d 1533, 1538 (Fed. Cir. 1991).
Defendants point to the specification's description of "the preferred approach disclosed" with the utilizing of a cable "electrically joined to the desired instrument or instruments," where "these cables may then be relatively permanent, with only the electrode sets being replaced for each usage." In the subsequent more detailed section on the preferred embodiment, the specification describes cable structures for each of the three devices, as well as connectors and circuits to be attached with each cable that protect the devices from damage when employing another simultaneously connected device. In addition, the drawings in figures 1 and 28 depict a system using a "cable means" with protective circuitry that simultaneously hooks the electrodes to a monitor, a defibrillator and an electrosurgical device. As these drawings in the specification illustrate a configuration of the cables and connectors permitting simultaneous connection, defendants argue that the "cable means" must be limited to equivalents of such a configuration.
As defendants argue, the specification presents a preferred embodiment where all three devices are simultaneously attached to the electrode set. In setting forth the system in structural detail, the specification further describes connectors and circuitry attached to each of the cables for various permutations of simultaneous connection to the devices. But a "means-plus-function" limitation is not limited to the equivalents of a single preferred structure. Rather, it is limited to the equivalents of any structures described therein necessary for carrying out the function. See United States v. Telectronics, Inc., 857 F.2d 778, 782 (Fed. Cir. 1988) (defining means-plus-function limitation as including structural alternative presented in specification).
In addition, a "means-plus-function" limitation incorporates only the disclosed structure necessary to perform the specified function. See General Elec. Co. v. U.S., 215 Ct. Cl. 636, 572 F.2d 745, 776 (Ct. Cl. 1978) (refusing to incorporate elements into limitation from the specification not necessary for performing function); see also Lockheed Aircraft Corp. v. U.S., 213 Ct. Cl. 395, 553 F.2d 69, 81 (Ct. Cl. 1977) ("a 'means-plus-function' claim covers the structure necessary to perform the specified function"). The function which defines the limitation is determined by the terms of the claim, not the specification. See DMI, 755 F.2d 1570, 1573. As explained above, claim 34 does not indicate that the "cable means" is for the function of simultaneous connection of the devices, but rather that it is for the function of "selectively connecting the monitoring device, the therapeutic device or the stimulating device" to the connector means and electrode sets.
In the preferred embodiment, the specification details the structure of a cable for each device, and the necessary connector means so that the cable may attach to a standardized connector plug. Although the specification further describes connectors and protective circuitry to connect the devices together and the disposable electrode set, these additional structures are only required for the preferred embodiment. Accordingly, the preferred embodiment presents an "interrelating arrangement" depicted in figures 1 and 28 that includes the attachment of the protective circuitry and connector means for the simultaneous connection of all of three cables and devices.
But the specification never limits the "cables means" to either figure 1 or 28. Cf. Hormone Research Foundation, 904 F.2d at 1563 (specification and prosecution history explicitly limited claimed invention to single accompanying figure). Instead, the specification provides that in addition to the preferred embodiment the invention includes sub-systems using many of the same elements:
Each of these instruments be connected to the patient's body through the electrode elements by itself or in combination with one or more of the other instruments by means of an appropriate interrelating arrangement.
After presenting the preferred embodiment, the specification explains that the invention includes the separate connection of each of the devices to the electrode elements:
In addition to the provision of a multiplicity of functions through a single pair of electrode elements, this invention also provides for the separate connection of each of the instruments to that pair of electrode elements. . . Therefore this invention not only relates to the unique system, but it also relates to a number of novel and unobvious sub-systems and components of that physiological electrode system.