Court Opinion

ID: 4659133
Source: CourtListenerOpinion
Date Created: 2021-02-10 16:01:05.836268+00
Date Added: 2024-06-11T08:01:57.626434
License: Public Domain

Case: 20-1189     Document: 46    Page: 1   Filed: 02/10/2021

   United States Court of Appeals
       for the Federal Circuit
                   ______________________

      INFINITY COMPUTER PRODUCTS, INC.,
                Plaintiff-Appellant

                             v.

                OKI DATA AMERICAS, INC.,
                     Defendant-Appellee
                   ______________________

                         2020-1189
                   ______________________

     Appeal from the United States District Court for the
 District of Delaware in No. 1:18-cv-00463-LPS, Chief Judge
 Leonard P. Stark.
                   ______________________

                 Decided: February 10, 2021
                  ______________________

    ANDREW DINOVO, DiNovo Price LLP, Austin, TX, ar-
 gued for plaintiff-appellant. Also represented by NICOLE E.
 GLAUSER.

    MARC ROBERT LABGOLD, Marc R. Labgold, P.C., Reston,
 VA, argued for defendant-appellee. Also represented by
 PATRICK J. HOEFFNER; JEFFREY T. CASTELLANO, ANDREW E.
 RUSSELL, JOHN W. SHAW, Shaw Keller LLP, Wilmington,
 DE.
                 ______________________
Case: 20-1189       Document: 46   Page: 2       Filed: 02/10/2021

 2        INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.

     Before PROST, Chief Judge, CLEVENGER and TARANTO,
                       Circuit Judges.
 PROST, Chief Judge.
     Infinity Computer Products, Inc. (“Infinity”) appeals
 the U.S. District Court for the District of Delaware’s final
 judgment of invalidity. We agree with the district court
 that the patent claims asserted by Infinity against Oki
 Data Americas, Inc. (“Oki Data”) are indefinite. We there-
 fore affirm.
                          BACKGROUND
                               I
     Infinity sued Oki Data for infringing four related pa-
 tents: U.S. Patent Nos. 6,894,811 (“the ’811 patent”),
 7,489,423, 8,040,574, and 8,294,915. 1 The patents share a
 specification and involve using a fax machine as a printer
 or scanner for a personal computer. The indefiniteness is-
 sues in this case revolve around the connection between the
 fax machine and the computer, termed a “passive link.”
 The parties agree that claim 1 of the ’811 patent is repre-
 sentative. That claim states:
      1. A method of creating a scanning capability
      from a facsimile machine to a computer, with
      scanned image digital data signals transmitted
      through a bi-directional direct connection via a
      passive link between the facsimile machine and the
      computer, comprising the steps of:

      1 Infinity asserted claims 1–2, 4, 6–7, and 18–20 of
 the ’811 patent; claims 1–4 and 6 of U.S. Patent No.
 7,489,423; claims 1–2, 4–5, and 7–8 of U.S. Patent No.
 8,040,574; and claims 1, 6–9, and 14–15 of U.S. Patent No.
 8,294,915.
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 INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.     3

     by-passing or isolating the facsimile machine and
     the computer from the public network telephone
     line;
     coupling the facsimile machine to the computer;
     conditioning the computer to receive digital facsim-
     ile signals representing data on a scanned docu-
     ment; and
     conditioning the facsimile machine to transmit dig-
     ital signals representing data on a scanned docu-
     ment to the computer, said computer being
     equipped with unmodified standard protocol
     send/receive driver communications software ena-
     bling the reception of scanned image signals from
     the facsimile machine, said transmitted digital fac-
     simile signals being received directly into the com-
     puter through the bi-directional direct connection
     via the passive link, thereafter, said computer pro-
     cessing the received digital facsimile signals of the
     scanned document as needed.
 ’811 patent claim 1 (emphases added).
      The ’811 patent is a continuation-in-part of U.S. Patent
 App. No. 08/226,278 (“the ’278 application”), which itself
 ultimately issued as U.S. Patent No. 5,530,558. The “prin-
 cipal object” of the claimed invention is “to provide a circuit
 for interfacing a PC and a facsimile to enable the facsimile
 to be utilized as a scanner or a printer for a PC and to ac-
 complish all of the objectives of a scanner or a printer in a
 simple straightforward manner through the use of a circuit
 of highly simplified design and low cost.” ’811 patent col. 1
 ll. 39–45; see id. Fig. 1 (circuit diagram).
     Figures 2a–e of the ’811 patent depict this circuit rela-
 tive to a computer and a fax machine. They also depict
 “facsimile modem circuitry,” which “may be either internal
 or external” to the computer.         Id. at col. 6 ll. 3–5.
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 4    INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.

 Figures 2b–d, for example, depict a fax machine connected
 to a computer via an RJ-11 cable, with fax modem circuitry
 located internal to the computer.

 Id. Fig. 2b.
     Figures 2f–h do not show fax modem circuitry inter-
 posed between the fax machine and the computer. Nor do
 they depict it as internal to the computer. The arrange-
 ment of Figure 2f, for example, “is used with PC’s which do
 not have a fax modem installed.” Id. at col. 6 ll. 62–63.
 This figure depicts a fax machine connected to a computer
 via an RS-232 cable, with both the circuit of the invention
 and the fax modem circuitry residing in the fax machine.
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 INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.   5

 Id. Fig. 2f. Unlike Figures 2a–e, Figures 2f–h were not dis-
 closed in the parent ’278 application.
                              II
     The term “passive link” does not appear in the ’811 pa-
 tent specification. Nor does it appear in the parent ’278
 application. Rather, Infinity first introduced the term dur-
 ing prosecution of the ’811 patent to distinguish an antici-
 pating prior-art reference—U.S. Patent No. 5,452,106
 (“Perkins”). This reference, the patent examiner noted, dis-
 closes using a fax machine as a scanner or printer for a
 computer. J.A. 2129–30.
     Infinity’s initial attempts at distinguishing Perkins
 were unsuccessful. First, Infinity amended the claim to re-
 cite (among other things) data transfer “between the fac-
 simile machine and the computer” that occurs “without
 interruption.” J.A. 1227. Infinity also distinguished Per-
 kins at length in accompanying remarks, on the ground
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 6    INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.

 that Perkins includes an intervening component—“de-
 vice 3”—between the fax machine and the computer.
 J.A. 1233–36. As Infinity noted, one function of device 3
 was to serve as a fax modem. J.A. 1233.
     Infinity asserted that, “[u]nlike Perkins,” the claimed
 invention permits “the uninterrupted transfer of scanning
 or printing signals between the facsimile and the computer
 without the use of intervening circuitry, and does not in-
 tercept the signals for demodulation as Perkins does with
 device 3.” J.A. 1234. Later in the same response, Infinity
 reiterated that its invention “does not require a micropro-
 cessor or any circuitry or software to interrupt and intercept
 the signals which occur in transmissions between a fax ma-
 chine and a computer.” J.A. 1235.
     The examiner was not persuaded. Perkins’s device 3,
 the examiner countered, “may be provided on a card for lo-
 cation in the computer.” J.A. 3443. This internal-card em-
 bodiment, the examiner continued, represents an
 “uninterrupted” connection between the fax machine and
 the computer that defeats Infinity’s distinction. J.A. 3443.
     Infinity responded with further amendments and re-
 marks in several subsequent responses, including by re-
 peating the “intervening circuitry” distinction. Eventually,
 Infinity overcame Perkins by amending the claim to re-
 quire a “passive link” between the fax machine and the
 computer and by using this new term as a hook for its in-
 tervening-circuitry distinction:
     The Applicant creates a passive link between the
     facsimile machine and the computer in order to ac-
     commodate the signal transfer for printing or scan-
     ning. Therefore, the Applicant does not require any
     intervening apparatus as does Perkins. The appli-
     cant therefore believes[] Perkins did not anticipate
     the methods used by the Applicant.
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 INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.    7

 J.A. 2196 (emphases added). In support, Infinity empha-
 sized that Perkins requires an intervening modem:
    Perkins’[s] device 3 or card design requires a mo-
    dem to be integrated into it in order to transfer sig-
    nals for scanning or printing as part of his
    computer and facsimile transceiver interface. In
    contrast, the Applicant can transfer digital signals
    between the facsimile transceiver and the com-
    puter without the need for a modem at the com-
    puter interface.
 J.A. 2197. In doing so, Infinity relied on its more recent
 Figures 2f–h, which do not depict a fax modem between the
 fax machine and the computer. J.A. 2198 (“[A] modem is
 not required at the computer in Figures 2F, 2G, and 2H.”).
      Infinity also reprised its argument that Perkins’s de-
 vice 3 is intervening circuitry between the fax machine and
 the computer—even when placed internally. This is so, In-
 finity contended, because device 3 intercepts data before it
 reaches the I/O bus of the computer:
    In [Perkins’s] internal configuration, facsimile
    transmission data never enters the computer I/O
    Bus until after it is processed by the device 3 card
    circuits into digital data, thereafter, the flow of
    data transfers to the I/O Bus and is processed by
    the computer circuitry.
    It is therefore evident that Perkins’[s] device 3 in-
    tercepts the flow of data before it is transmitted to
    the computer circuits, in order to convert the ana-
    log signal into a digital signal format acceptable to
    the computer. Hence, even though circuitry of de-
    vice 3 is placed in a card within the box containing
    the computer it should be regarded as a peripheral
    device to the computer which processes data before
    it is transmitted to the I/O bus of the computer.
 J.A. 2201 (emphasis added).
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 8    INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.

     Unlike Perkins’s internal-card embodiment, Infinity
 argued, the claimed “passive link” conveys data directly to
 the I/O bus of the computer without intervening circuitry:
     Contrary to the above, when the Applicant trans-
     fers digital data from the facsimile transceiver
     through a passive link for scanning to the com-
     puter, the non-intercepted data enters through the
     RS 232 type connector port of the computer and
     passes directly to the I/O Bus and is processed by
     the receiving circuits (i.e., UART, CPU) of the com-
     puter, providing a true non intercepted digital sig-
     nal between the facsimile transceiver and the
     computer.
     In effect, the Applicant’s method does not use in-
     termediary peripheral circuitry for signal intercep-
     tion, resulting in demodulation or modulation
     which is required by Perkins with his card or de-
     vice 3.
 J.A. 2201 (emphases added). This time, Infinity’s argu-
 ment was successful, and the ’811 patent issued after fur-
 ther prosecution.
                              III
      The ’811 patent was later the subject of three ex parte
 reexaminations. In one of these, Infinity sought to ante-
 date a reference, U.S. Patent No. 5,900,947 (“Kenmochi”),
 by arguing that claim 1 of the ’811 patent is entitled to the
 priority date of the ’278 application. Specifically, as Infin-
 ity recounted in summarizing an examiner interview, In-
 finity asserted that “the RJ-11 telephone cable shown in
 Figs. 2b, 2c and 2d of the [’278 application] is the ‘direct’
 and ‘passive link.’” J.A. 2500. Infinity made this argument
 even though each of Figures 2b–d depicts internal fax mo-
 dem circuitry like Perkins’s internal-card embodiment.
      Likewise, in its written response to the Kenmochi re-
 jection, Infinity argued that “the RJ 11 telephone cable and
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 INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.    9

 use thereof in communicating data between the fax ma-
 chine 30 and the PC computer 40 meets the . . . definition
 of ‘passive link.’” J.A. 2377–78. “For example, with respect
 to Figures 2b–2d” of the ’278 application, Infinity argued,
 “the RJ 11 telephone cable connects the fax machine 30 to
 the PC computer 40 such that there is no intervening ap-
 paratus or signal interception by a processing element or
 any active component, along the path of an unbroken direct
 connection between the PC and the facsimile machine.”
 J.A. 2378 (internal quotation marks omitted). Along the
 way, Infinity acknowledged that “[t]he term ‘passive link’
 was first introduced in an amendment . . . to distinguish
 the invention of the [’811 patent] from Perkins.” J.A. 2377.
     Infinity also submitted an expert declaration during
 the reexamination. Without addressing the prior distinc-
 tion of Perkins, Infinity’s expert witness likewise opined
 that Figures 2b–d of the ’278 application disclose a “passive
 link.” J.A. 1980. He added that “the use of a modulation
 procedure within the PC and facsimile machine as shown
 in the figures does not insert an intervening apparatus or
 processing element along the path, e.g. on the cable be-
 tween the PC’s RJ-11 and the fax’s RJ-11.” J.A. 1980.
      The examiner accepted Infinity’s argument without ex-
 pressly addressing Infinity’s prior distinction of Perkins,
 J.A. 2525–29, despite recognizing in an interview summary
 that “the ‘passive link’ limitation” was a basis on which In-
 finity overcame “rejections based on Perkins” during pros-
 ecution. J.A. 1992. After further proceedings, including an
 appeal to the Patent Trial and Appeal Board (“Board”), a
 reexamination certificate ultimately issued noting the pa-
 tentability of the claims.
                              IV
      In this case, Oki Data argued before the district court
 that the terms “passive link” and “computer” are indefinite
 because Infinity took conflicting positions on the endpoint
 of the “passive link” during prosecution. In particular, Oki
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 10       INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.

 Data argued that Infinity took one position to overcome
 Perkins and a different position to antedate Kenmochi—
 creating uncertainty as to where the “passive link” ends
 and where the “computer” begins. At the Markman hear-
 ing, Infinity acknowledged that one of ordinary skill would
 need to be reasonably certain where the passive link ends
 and the computer begins in order for the claims to be defi-
 nite. Infinity Comput. Prods., Inc. v. Oki Data Ams., Inc.,
 No. 18-463, 2019 WL 2422597, at *4 (D. Del. June 10,
 2019), reconsideration denied, 2019 WL 5213250 (D. Del.
 Oct. 16, 2019). 2
      The district court agreed with Oki Data that “passive
 link” and “computer” are indefinite. First, the court ex-
 plained that Infinity had taken materially inconsistent po-
 sitions regarding the extent of the claimed “passive link”—
 specifically, whether it ends at the I/O bus inside the com-
 puter (as argued to distinguish Perkins) or merely at the
 computer’s port (as argued to antedate Kenmochi). Id.
 at *4–6. Therefore, the court concluded, the endpoint of
 “passive link” is not reasonably certain and the term is in-
 definite. Id.
     Second, the court reasoned that because there is not
 reasonable certainty about where the “passive link” ends,
 there also cannot be reasonable certainty about where the
 “computer” begins. Id. at *6. “Specifically, where the pas-
 sive link ends at a computer port, the computer begins at
 the port, and where the passive link ends at the I/O bus,
 the computer begins at the I/O bus.” Id. The court denied
 Infinity’s motion for reconsideration and entered a final
 judgment of invalidity. Infinity, 2019 WL 5213250, at *1–

      2  Markman Tr. 61:19–22, J.A. 3855 (The Court: “In
 order for these claims to be definite, does one of skill in the
 art have to be reasonably certain where the passive link
 ends and the computer begins?” Mr. DiNovo: “Yes.”).
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 INFINITY COMPUTER PRODUCTS     v. OKI DATA AMERICAS, INC.     11

 2; J.A. 22. This appeal followed. We have jurisdiction un-
 der 28 U.S.C. § 1295(a)(1).
                          DISCUSSION
                                I
      “The Patent Act requires that a patent specification
 ‘conclude with one or more claims particularly pointing out
 and distinctly claiming the subject matter which the appli-
 cant regards as [the] invention.’” Nautilus, Inc. v. Biosig
 Instruments, Inc., 572 U.S. 898, 901 (2014) (alteration in
 original) (quoting 35 U.S.C. § 112, ¶ 2 (2006)). “[A] patent
 is invalid for indefiniteness if its claims, read in light of the
 specification delineating the patent, and the prosecution
 history, fail to inform, with reasonable certainty, those
 skilled in the art about the scope of the invention.” Id. This
 standard strikes the “delicate balance” of accounting for
 both “the inherent limitations of language” and the need to
 “afford clear notice of what is claimed, thereby apprising
 the public of what is still open to them.” Id. at 909 (cleaned
 up). It also serves as a “meaningful . . . check” against “fos-
 ter[ing] [an] innovation-discouraging ‘zone of uncertainty.’”
 Id. at 910–11 (quoting United Carbon Co. v. Binney &
 Smith Co., 317 U.S. 228, 236 (1942)).
     Indefiniteness is ultimately a question of law that we
 review de novo. Teva Pharms. USA, Inc. v. Sandoz, Inc.,
 789 F.3d 1335, 1341 (Fed. Cir. 2015). “[W]e look to the pa-
 tent record—the claims, specification, and prosecution his-
 tory—to ascertain if they convey to one of skill in the art
 with reasonable certainty the scope of the invention
 claimed.” Id. “The prosecution history ‘consists of the com-
 plete record of the proceedings before the PTO,’” including
 reexamination proceedings. InTouch Techs., Inc. v. VGO
 Commc’ns, Inc., 751 F.3d 1327, 1341 (Fed. Cir. 2014) (quot-
 ing Phillips v. AWH Corp., 415 F.3d 1303, 1317 (Fed. Cir.
 2005) (en banc)); see also Krippelz v. Ford Motor Co.,
 667 F.3d 1261, 1266 (Fed. Cir. 2012) (“A patentee’s state-
 ments during reexamination can be considered during
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 12   INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.

 claim construction.”). And “[a] statement made during
 prosecution of related patents may be properly considered
 in construing a term common to those patents.” Teva,
 789 F.3d at 1343.
      Indefiniteness may result from inconsistent prosecu-
 tion history statements where the claim language and
 specification on their own leave an uncertainty that, if un-
 resolved, would produce indefiniteness. In Teva, for exam-
 ple, we concluded that the term “molecular weight” was
 indefinite. The parties had agreed that the term could re-
 fer to any of three different measures that are calculated in
 different ways and that typically yield materially different
 results. Id. at 1341. Neither the claim language nor the
 specification indicated which measure the claims covered.
 Id. The prosecution history did not answer the question.
 To the contrary, in the prosecution histories of two contin-
 uation applications with nearly identical specifications, the
 patentee defined the term in two different ways—in each
 case to successfully overcome a rejection. Id. at 1343–45.
 On that record, we concluded that the term was indefinite.
 Id. at 1345. The record here is similar. As with the term
 “molecular weight” in Teva, the claim language and speci-
 fication do not provide reasonable certainty about a crucial
 aspect of “passive link,” namely, where it ends. And far
 from resolving the uncertainty during prosecution, Infinity
 took conflicting positions during prosecution regarding the
 scope of “passive link.”
     At first, Infinity argued that a “passive link” does not
 allow for intervening circuitry, like a fax modem, between
 the fax machine and the I/O bus of the computer. At the
 time, Infinity asserted that even circuitry “within the box
 containing the computer,” like Perkins’s device 3, “should
 be regarded as a peripheral device to the computer which
 processes data before it is transmitted to the I/O bus of the
 computer.” J.A. 2201. Unlike Perkins, Infinity argued,
 data transmitted “through a passive link . . . passes di-
 rectly to the I/O Bus and is processed by the receiving
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 INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.    13

 circuits . . . of the computer.” J.A. 2201. On its own, this
 position would lead one of ordinary skill to believe a passive
 link does not end at the computer’s port but rather reaches
 to the I/O bus of the computer—especially “[g]iven the role
 of the statement in gaining allowance of the claims,” Teva,
 789 F.3d at 1344.
     Later, Infinity reversed course. During reexamination,
 Infinity contended that the passive link was coextensive
 with the RJ-11 cable in the embodiments of Figures 2b–d—
 embodiments which do include intervening circuitry (such
 as fax modems) between the fax machine and the com-
 puter’s I/O bus—indeed, within the “box containing the
 computer” like Perkins’s device 3. On its own, this argu-
 ment would lead one of ordinary skill to believe a “passive
 link” ends at the computer’s port.
     The public-notice function of a patent and its prosecu-
 tion history requires that we hold patentees to what they
 declare during prosecution. Teva, 789 F.3d at 1344. But
 holding Infinity to both positions results in a flat contradic-
 tion, providing no notice to the public of “what is still open
 to them.” Nautilus, 572 U.S. at 909. Here, one of ordinary
 skill cannot determine with any reasonable certainty, for
 instance, whether or not the claims cover arrangements
 like the internal-card embodiment of Perkins and the in-
 ternal-modem embodiments of Figures 2b–d. On the rec-
 ord before us, therefore, we agree with the district court
 that the intrinsic evidence leaves an ordinarily skilled ar-
 tisan without reasonable certainty as to where the passive
 link ends and where the computer begins.
                               II
     Infinity’s contrary arguments are unavailing. Before
 the district court and on appeal, Infinity advanced its reex-
 amination interpretation—i.e., that the passive link ends
 (and the computer begins) at the computer’s port. But as
 the district court recognized, such an interpretation contra-
 dicts Infinity’s distinction of Perkins—in which Infinity
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 14       INFINITY COMPUTER PRODUCTS   v. OKI DATA AMERICAS, INC.

 called Perkins’s device 3 an intervening apparatus even
 though it was internal to the computer. Infinity, 2019 WL
 5213250, at *1 (“Thus, if the ‘passive link’ ends at a com-
 puter port and not at the computer’s I/O bus, as Infinity
 now suggests, Perkins would include a ‘passive link,’ ren-
 dering the patentee’s distinction from Perkins nugatory.”).
      Infinity argues that the court misinterpreted its state-
 ments distinguishing Perkins. According to Infinity, the
 passive link is the physical cable spanning the fax machine
 and the computer and Infinity’s prosecution statements
 should be interpreted to mean that the data flowing
 through the passive link, rather than the passive link it-
 self, proceeds uninterrupted to the I/O bus. But “we hold
 patentees to the actual arguments made, not the argu-
 ments that could have been made” during prosecution.
 Tech. Props. Ltd. LLC v. Huawei Techs. Co., 849 F.3d 1349,
 1359 (Fed. Cir. 2017). And the Supreme Court has warned
 us against “viewing matters post hoc” to “ascribe some
 meaning to a patent’s claims.” Nautilus, 572 U.S. at 911–
 12. Here, Infinity stated that the passive link is the reason
 why its invention requires no intervening apparatus.
 J.A. 2196 (“The Applicant creates a passive link . . . .
 Therefore, the Applicant does not require any intervening
 apparatus as does Perkins.”). To distinguish Perkins’s in-
 ternal-card embodiment, the passive link could not be
 merely a cable that ends at the computer’s port.
     Infinity has also at various points relied on an express
 definition of “passive link” that it presented to the Patent
 Office. Infinity first offered this definition in response to a
 rejection that came after Perkins was withdrawn, and later
 again through its expert witness during reexamination and
 before the Board. 3 The definition provides:

      3  Infinity’s appeal to the Board concerned whether
 the ’278 application supports claims reciting digital-signal
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 INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.     15

     [A] “passive link” is one where the initiation of data
     flow is activated from a set-up procedure within the
     PC and/or the facsimile machine, and said data is
     transferred, with no intervening apparatus or sig-
     nal interception by a processing element or any ac-
     tive component, along the path of an unbroken
     direct connection between the PC and the facsimile
     machine, for purposes of providing both scanning
     or printing data.
 J.A. 1784. This is no help. According to this definition, a
 passive link is “one” characterized by the properties de-
 scribed. The definition, therefore, does not resolve the
 point in question: the extent of the “link.”
     Additionally, Infinity emphasizes that it submitted
 “unrebutted expert testimony” to the district court. Yet the
 testimony Infinity submitted merely states that “passive
 link” needs no construction and, in the alternative, that it
 should be construed according to the unhelpful definition
 above. J.A. 2975–76. And, as Oki Data notes, that testi-
 mony repeats the very same statements made during reex-
 amination that gave rise to the inconsistency in the first
 place. Infinity’s contradictory positions are plain from the
 patent record. The district court therefore saw no need for
 extrinsic evidence, and neither do we. See Teva, 789 F.3d
 at 1342 (“The internal coherence and context assessment
 of the patent, and whether it conveys claim meaning with
 reasonable certainty, are questions of law.”).

 transmission. J.A. 3281. In passing, the Board described
 Figures 2b–d of the ’811 patent as depicting a passive
 link—i.e., “the RJ-11 telephone cable”—based on the defi-
 nition that Infinity’s expert witness proffered. J.A. 3284.
 The Board’s only mention of Perkins related to Infinity’s
 prosecution argument that Perkins disclosed an analog-
 only configuration. J.A. 3287.
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 16   INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.

      We also reject Infinity’s argument that the district
 court should not have held the claims indefinite based on a
 “single statement.” E.g., Appellant’s Br. 50–53. As an ini-
 tial matter, we disagree that the court did so. As discussed
 above, Infinity repeatedly made the distinction that was
 eventually successful in overcoming Perkins. Moreover, as
 Oki Data points out, a single contradictory statement was
 sufficient in Teva. Indeed, we noted there that we hold pa-
 tentees even to erroneous prosecution statements. Teva,
 789 F.3d at 1344.
      Further, it is immaterial that Infinity also distin-
 guished Perkins on another ground—i.e., that Perkins dis-
 closes an analog-only arrangement. See, e.g., Andersen
 Corp. v. Fiber Composites, LLC, 474 F.3d 1361, 1374
 (Fed. Cir. 2007) (“An applicant’s invocation of multiple
 grounds for distinguishing a prior art reference does not
 immunize each of them from being used to construe the
 claim language.”). Infinity admits that it made both dis-
 tinctions during prosecution. Reply Br. 20. And, for what
 it’s worth, Infinity commented in an interview during reex-
 amination that “the examiner did not find the analog ver-
 sus digital signal argument persuasive.” Reply Br. 20; J.A.
 1992.
     We also disagree that the presence of the term “com-
 puter interface” in the claim at the time of the Perkins dis-
 tinction somehow harmonizes Infinity’s inconsistent
 statements. As the district court explained, the claim at
 the time also recited “a passive link . . . from the facsimile
 machine to the computer.” Infinity, 2019 WL 5213250,
 at *2 (alteration in original). And Infinity “did not make
 any mention of, let alone place any material significance
 on, the phrase ‘computer interface’ in its distinction of the
 claimed invention’s ‘passive link’ from the connection in
 Perkins.” Id.
     Last, Infinity argues that “computer” is a familiar term
 with a well-understood ordinary meaning. We recognize
Case: 20-1189    Document: 46       Page: 17   Filed: 02/10/2021

 INFINITY COMPUTER PRODUCTS    v. OKI DATA AMERICAS, INC.   17

 that, in a vacuum, it might seem odd to hold “computer”
 indefinite. We also recognize that the specification identi-
 fies examples of commercial computers, such as an “Apple
 Macintosh” and an “IBM PC.” ’811 patent col. 4 ll. 64–66.
 Yet the indefiniteness here does not reside in the term
 “passive link” or “computer” on its own but rather in the
 relationship between the two in the context of these
 claims. 4 And any resulting strangeness stems from Infin-
 ity’s own statements. See, e.g., J.A. 2201 (“[E]ven though
 circuitry of device 3 is placed in a card within the box con-
 taining the computer[,] it should be regarded as a periph-
 eral device to the computer.”). As already noted, Infinity
 agrees that one of ordinary skill would need to be reasona-
 bly certain where the passive link ends and where the com-
 puter begins. There is no reasonable certainty as to that
 boundary. We therefore agree with the district court that
 both terms are indefinite.
                              III
     We have considered Infinity’s remaining arguments
 and find them unpersuasive. The district court correctly
 concluded that the asserted claims are invalid for indefi-
 niteness. We affirm.
                         AFFIRMED

     4   See Markman Tr. 49:19–25, J.A. 3843 (Mr.
 Labgold: “[W]e all know what a computer is. That is not
 what the issue is. It’s the way that it is being used and how
 it has been differentiated with regard to the passive link.”).