  United States Court of Appeals
      for the Federal Circuit
                ______________________

   IN RE PAPST LICENSING DIGITAL CAMERA
               PATENT LITIGATION
______________________________________________________

       PAPST LICENSING GMBH & CO. KG,
               Plaintiff-Appellant,

                           v.

  FUJIFILM CORPORATION, FUJIFILM NORTH
  AMERICA CORPORATION (formerly known as
    Fujifilm USA, Inc.), HEWLETT-PACKARD
COMPANY, JVC COMPANY OF AMERICA, NIKON
 CORPORATION, NIKON, INC., OLYMPUS CORP.,
OLYMPUS IMAGING AMERICA INC., PANASONIC
  CORPORATION (formerly known as Matsushita
    Electric Industrial Co., LTD.), PANASONIC
CORPORATION OF NORTH AMERICA , SAMSUNG
OPTO-ELECTRONICS AMERICA, INC., SAMSUNG
TECHWIN CO., AND VICTOR COMPANY OF JAPAN,
                       LTD.,
                Defendants-Appellees.
               ______________________

                      2014-1110
                ______________________

    Appeal from the United States District Court for the
District of Columbia in No. 1:07-mc-00493-RMC, Judge
Rosemary M. Collyer.
                ______________________
2                 PAPST LICENSING   v. FUJIFILM CORPORATION



                Decided: February 2, 2015
                 ______________________

   JOHN T. BATTAGLIA, Fisch Hoffman Sigler LLP, of
Washington, DC, argued for plaintiff-appellant. With him
on the brief were ALAN M. FISCH and ROY WILLIAM
SIGLER.

     RACHEL M. CAPOCCIA, Alston & Bird LLP, of Los An-
geles, California, argued for defendants-appellees. With
her on the brief for Panasonic Corporation, et al., was
THOMAS W. DAVISON. On the brief for Fujifilm Corpora-
tion, et al., were STEVEN J. ROUTH, STEN A. JENSEN, JOHN
R. INGE and T. VANN PEARCE, JR, Orrick, Herrington &
Sutcliffe LLP, of Washington, DC. On the brief for Nikon
Corporation, et al., were DAVID L. WITCOFF and MARC S.
BLACKMAN, Jones Day, of Chicago, Illinois. Of counsel was
MARRON ANN MAHONEY. On the brief for Olympus Corpo-
ration, et al., were RICHARD DE BODO and ANDREW V.
DEVKAR, Bingham McCutchen LLP, of Santa Monica,
California. Of counsel was SUSAN BAKER MANNING, Mor-
gan, Lewis & Bockius LLP, of Washington, DC. On the
brief for Samsung Techwin, Co., et al., was PATRICK J.
KELLEHER, Drinker Biddle & Reath LLP, of Chicago,
Illinois.

    CHARLENE M. MORROW, Fenwick & West LLP, of
Mountain View, California, argued for defendant-appellee
Hewlett-Packard Company. With her on the brief were
DAVID D. SCHUMANN and BRYAN A. KOHM, of San Francis-
co, CA.
               ______________________

    Before TARANTO, SCHALL, and CHEN, Circuit Judges.
TARANTO, Circuit Judge.
   Papst Licensing GmbH & Co. KG owns U.S. Patent
Nos. 6,470,399 and 6,895,449. The written descriptions
PAPST LICENSING   v. FUJIFILM CORPORATION                 3



are largely the same, the ’449 patent having issued on a
divisional application carved out of the application that
became the ’399 patent. The focus of both patents is an
interface device for transferring data between an in-
put/output data device and a host computer. The current
appeal involves whether certain digital-camera manufac-
turers infringe Papst’s patents. The district court, apply-
ing and elaborating on its constructions of various claim
terms, entered summary judgment of non-infringement,
concluding that none of the manufacturers’ accused
products at issue here come within any of the asserted
claims. Papst appeals five claim constructions. We agree
with Papst that the district court erred in the identified
respects. We therefore vacate the summary judgment of
non-infringement.
                        BACKGROUND
     The ’399 and ’449 patents, both entitled “Flexible In-
terface for Communication Between a Host and an Analog
I/O Device Connected to the Interface Regardless the
Type of the I/O Device,” disclose a device designed to
facilitate the transfer of data between a host computer
and another device on which data can be placed or from
which data can be acquired. ’399 patent, Title and Ab-
stract. 1 The written description states that, while inter-
face devices were known at the time of the invention, the
existing devices had limitations, including that they
tended to require disadvantageous sacrifices of data-
transfer speed or of flexibility as to what host computers
and data devices they would work with. ’399 patent, col.
1, line 15, to col. 2, line 13. Thus, “standard interfaces”—
those “which, with specific driver software, can be used


   1    Because the ’399 and ’449 patents have very simi-
lar written descriptions, we cite the ’399 patent, and refer
to a “written description” in the singular, except when
there are important differences between the two.
4                    PAPST LICENSING   v. FUJIFILM CORPORATION



with a variety of host systems”—“generally require very
sophisticated drivers” to be downloaded onto the host
computer, but such drivers “are prone to malfunction
and . . . limit data transfer rates.” Id. at col. 1, lines 22–
28. On the other hand, with interface devices that “specif-
ically match the interface very closely to individual host
systems or computer systems,” “high data transfer rates
are possible,” but such interface devices “generally cannot
be used with other host systems or their use is very
ineffective.” Id. at col. 1, line 67, to col. 2, line 7. The fast,
host-tailored interface also “must be installed inside the
computer casing to achieve maximum data transfer
rates,” which is a problem for laptops and other space-
constrained host systems. Id. at col. 2, lines 8–13.
     The patents describe an interface device intended to
overcome those limitations. It is common ground between
the parties that, when a host computer detects that a new
device has been connected to it, a normal course of action
is this: the host asks the new device what type of device it
is; the connected device responds; the host determines
whether it already possesses drivers for (instructions for
communicating with) the identified type of device; and if
it does not, the host must obtain device-specific drivers
(from somewhere) before it can engage in the full intended
communication with the new device. In the patents at
issue, when the interface device of the invention is con-
nected to a host, it responds to the host’s request for
identification by stating that it is a type of device, such as
a hard drive, for which the host system already has a
working driver. By answering in that manner, the inter-
face device induces the host to treat it—and, indirectly,
data devices on the other side of the interface device, no
matter what type of devices they are—like the device that
is already familiar to the host. Thereafter, when the host
communicates with the interface device to request data
from or control the operation of the data device, the host
uses its native device driver, and the interface device
PAPST LICENSING    v. FUJIFILM CORPORATION                   5



translates the communications into a form understanda-
ble by the connected data device. See id. at col. 3, line 25,
to col. 5, line 32.
    The interface device of the invention thus does not re-
quire that a “specially designed driver” for the interface
device be loaded into a host computer—neither a “stand-
ard” one to be used for a variety of hosts nor one custom-
ized for a particular host. Id. at col. 5, line 15. Instead, it
uses a host’s own familiar driver, which (as for a hard
drive) often will have been designed (by the computer
system’s manufacturer) to work fast and reliably. The
result, says the written description, is to allow data
transfer at high speed without needing a new set of
instructions for every host—“to provide an interface
device for communication between a host device and a
data transmit/receive device whose use is host device-
independent and which delivers a high data transfer
rate.” Id. col. 3, lines 25–28.
    Claim 1 of the ’399 patent sets forth the specifics of
the claimed interface device:
    1. An interface device for communication be-
    tween a host device, which comprises drivers for
    input/output devices customary in a host device
    and a multi-purpose interface, and a data
    transmit/receive device, the data trans-
    mit/receive device being arranged for providing
    analog data, comprising:
    a processor;
    a memory;
    a first connecting device for interfacing the host
    device with the interface device via the multi-
    purpose interface of the host device; and
    a second connecting device for interfacing the
    interface device with the data transmit/receive
6                  PAPST LICENSING   v. FUJIFILM CORPORATION



    device, the second connecting device including a
    sampling circuit for sampling the analog data
    provided by the data transmit/receive device and
    an analog-to-digital converter for converting data
    sampled by the sampling circuit into digital data,
    wherein the interface device is configured by the
    processor and the memory to include a first com-
    mand interpreter and a second command inter-
    preter,
    wherein the first command interpreter is config-
    ured in such a way that the command interpreter,
    when receiving an inquiry from the host device as
    to a type of a device attached to the multi-purpose
    interface of the host device, sends a signal, re-
    gardless of the type of the data trans-
    mit/receive device attached to the second
    connecting device of the interface device, to the
    host device which signals to the host device that it
    is an input/output device customary in a host
    device, whereupon the host device communicates
    with the interface device by means of the driver
    for the input/output device customary in a host
    device, and
    wherein the second command interpreter is con-
    figured to interpret a data request command from
    the host device to the type of input/output device
    signaled by the first command interpreter as a da-
    ta transfer command for initiating a transfer of
    the digital data to the host device.
Id. col. 12, line 42, to col. 13, line 13 (emphases added to
highlight language of particular significance to the issues
on appeal). Claim 1 of the ’449 patent is similar, but it
does not require the data device to be an analog device,
and it requires the interface device to respond to the host
that it is a storage device. ’449 patent, col. 11, line 46, to
PAPST LICENSING   v. FUJIFILM CORPORATION                 7



col. 12, line 6. A few other differences between the claims
are discussed infra.
     Beginning in 2006, Papst sent letters to major digital-
camera manufacturers, accusing them of infringing its
patents and requesting that they enter into negotiations
to license its inventions. One of the manufacturers sued
Papst in the United States District Court for the District
of Columbia, seeking a declaratory judgment of non-
infringement. In 2008, Papst filed infringement suits
against the camera manufacturers in multiple district
courts across the country. A multi-district litigation panel
then consolidated all cases and transferred them to the
D.C. district court.
    In preparation for claim construction, the district
court received a “tutorial” from the parties’ experts, whom
the court asked to be “neutral” and who addressed the
background of the technology, how the claimed inventions
work, and other technical understandings, but not wheth-
er any particular term in the patent or the prior art has a
particular meaning in the relevant field. J.A. 1596–97;
see In re Papst Licensing GmbH & Co. KG Litig., No. 07-
mc-00493 (D.D.C. June 6, 2008) (order specifying scope of
tutorial). The court then heard extensive argument from
counsel, but it declined to admit expert testimony or to
rely on an expert declaration from Papst, stating that “the
intrinsic evidence—the claims, the specification, and the
prosecution history—provide the full record necessary for
claims construction.” J.A. 1597.
    The court issued its initial claim-construction order in
2009. It issued a modified claim-construction order after
additional briefing. The district court then ruled on eight
summary-judgment motions filed by the camera manufac-
turers, treating the manufacturers as two distinct
groups—one group consisting of Hewlett-Packard Co.
(“HP”), the other of all other accused manufacturers
(“Camera Manufacturers”). As detailed in our discussion
8                  PAPST LICENSING   v. FUJIFILM CORPORATION



infra, the court’s rulings on summary judgment clarified
what it understood some of its claim constructions to
mean. With respect to the accused products now at issue,
the combined effect of the court’s summary-judgment
rulings was a determination of non-infringement by the
Camera Manufacturers and HP. The court ultimately
entered a final judgment of non-infringement under
Federal Rule of Civil Procedure 54(b) for both HP and the
Camera Manufacturers, In re Papst Licensing GmbH &
Co. KG Litig., 987 F. Supp. 2d 58, 62 (D.D.C. 2013),
having severed certain other claims, In re Papst Licensing
GmbH & Co. KG Litig., 967 F. Supp. 2d 63, 65 n.2, 71
(D.D.C. 2013).
    Papst appeals, arguing that the court’s summary-
judgment orders should be reversed because they rely on
incorrect constructions of five different terms from
the ’399 and ’449 patents. We have jurisdiction under 28
U.S.C. § 1295(a)(1).
                        DISCUSSION
    We review the grant of summary judgment of non-
infringement de novo, applying the same standard used
by the district court. See Bender v. Dudas, 490 F.3d 1361,
1366 (Fed. Cir. 2007). The infringement inquiry, which
asks if an accused device contains every claim limitation
or its equivalent, Warner-Jenkinson Co. v. Hilton Davis
Chem. Co., 520 U.S. 17, 29 (1997), depends on the proper
construction of the claims. See Cybor Corp. v. FAS Techs.,
Inc., 138 F.3d 1448, 1454 (Fed. Cir. 1998) (en banc). In
this case, we review the district court’s claim construc-
tions de novo, because intrinsic evidence fully determines
the proper constructions. See Teva Pharm. U.S.A. Inc. v.
Sandoz, Inc., 135 S. Ct. 831, 840–42 (2015). As we have
noted, the district court relied only on the intrinsic record,
not on any testimony about skilled artisans’ understand-
ings of claim terms in the relevant field, and neither party
challenges that approach.
PAPST LICENSING   v. FUJIFILM CORPORATION                  9



    Two clarifications simplify our analysis so that it is
enough for us to address the correctness of the district
court’s constructions. First, the parties have not present-
ed developed arguments other than arguments about the
choice, on each issue, between the district court’s con-
struction and the alternative construction by Papst that
the district court rejected. Specifically, for none of the
issues have the parties identified a third possibility and
both elaborated an argument for such a possibility and
explained the importance to the case of considering it.
Second, it is undisputed that if we reject all five of the
challenged constructions, the summary-judgment orders
must be vacated. 2
    We reject the five constructions at issue. We do so fol-
lowing our familiar approach to claim construction. “We
generally give words of a claim their ordinary meaning in
the context of the claim and the whole patent document;
the specification particularly, but also the prosecution
history, informs the determination of claim meaning in
context, including by resolving ambiguities; and even if
the meaning is plain on the face of the claim language,
the patentee can, by acting with sufficient clarity, dis-
claim such a plain meaning or prescribe a special defini-
tion.” World Class Tech. Corp. v. Ormco Corp., 769 F.3d
1120, 1123 (Fed. Cir. 2014); see Phillips v. AWH Corp.,
415 F.3d 1303, 1312–17 (Fed. Cir. 2005) (en banc); Thorn-
er v. Sony Computer Entm’t Am. LLC, 669 F.3d 1362,
1365 (Fed. Cir. 2012). We apply, in particular, the princi-
ple that “[t]he construction that stays true to the claim
language and most naturally aligns with the patent’s
description of the invention will be, in the end, the correct
construction.” Renishaw PLC v. Marposs Societa’ per



    2   If some aspects of the summary-judgment orders
are unaffected by our claim-construction rulings, they
may, to that extent, be reinstated on remand.
10                PAPST LICENSING   v. FUJIFILM CORPORATION



Azioni, 158 F.3d 1243, 1250 (Fed. Cir. 1998), adopted by
Phillips, 415 F.3d at 1316.
    On remand, this case will proceed in light of our
claim-construction reversals. For that reason, it is worth
reiterating that a district court may (and sometimes
must) revisit, alter, or supplement its claim constructions
(subject to controlling appellate mandates) to the extent
necessary to ensure that final constructions serve their
purpose of genuinely clarifying the scope of claims for the
finder of fact. See O2 Micro Int’l Ltd. v. Beyond Innova-
tion Tech. Co., 521 F.3d 1351, 1359 (Fed. Cir. 2008);
Pfizer, Inc. v. Teva Pharm., USA, Inc., 429 F.3d 1364,
1377 (Fed. Cir. 2005). That determination is to be made
as the case moves forward.
                            A
    Papst first challenges the district court’s “memory
card” summary judgment as relying on an improper
construction of the term “interface device” found in the
preamble of claims in both patents. The district court
construed the term as limiting the claims’ coverage to
“stand-alone device[s].” In re Papst Licensing GmbH &
Co. KG Litig., 670 F. Supp. 2d 16, 31–35 (D.D.C. 2009)
(“Claim Constr. Op.”). In particular, the court held that
“the data transmit/receive device must be a separate
device from the” claimed “interface device.” Id. at 33.
Subsequently, in granting summary judgment, the court
explained that what it meant by this requirement is that
the interface device may not be “a permanent part of
either the data transmit/receive device or the host de-
vice/computer,” by which it meant that it may not be
located permanently inside the housing of either of those
two devices. In re Papst Licensing GmbH & Co. KG Litig.,
932 F. Supp. 2d 14, 18, 21–22 (D.D.C. 2013).
PAPST LICENSING   v. FUJIFILM CORPORATION                11



                              1
     As a threshold matter, the Camera Manufacturers ar-
gue that we should not reach this issue because the
district court’s summary-judgment rulings do not depend
on the construction of “interface device.” They invoke
principles stated in SanDisk Corp. v. Kingston Technology
Co., 695 F.3d 1348, 1354 (Fed. Cir. 2012) (“[W]here, as
here, a party’s claim construction arguments do not affect
the final judgment entered by the court, they are not
reviewable.”), and Mangosoft, Inc. v. Oracle Corp., 525
F.3d 1327, 1330 (Fed. Cir. 2008) (“we review judgments,
not opinions”). We conclude, however, that the premise
for invoking the cited principles is missing here.
     The district court’s summary-judgment order regard-
ing memory-card devices shows that its final judgment
did turn on the construction of “interface device.” The
primary reason the court gave for rejecting Papst’s in-
fringement contentions was that “[t]he Court made clear
in its claims construction opinion that the interface device
is separate and distinct from the data transmit/receive
device.” Papst, 932 F. Supp. 2d at 21. The court cited
repeatedly to the portion of its claim-construction opinion
addressing “interface device.” E.g., id. at 18 (citing Claim
Constr. Op. at 32–35); id. at 21 (citing Claim Constr. Op.
at 34–35); id. at 23 (citing Claim Constr. Op. at 31–35).
And in its opening paragraphs, the court summarized the
Camera Manufacturers’ position on summary judgment
as relying on that same construction. Id. at 16 (“Because
the invented ‘interface device’ is a stand-alone device that
is separate and apart from any data transmit/receive
device, the Camera Manufacturers contend that a
memory card cannot be both part of the interface device
and a data transmit/receive device . . . .”). In these cir-
cumstances, we will consider whether the district court’s
construction is correct.
12                  PAPST LICENSING   v. FUJIFILM CORPORATION



                              2
    We hold that the term “interface device” is not limited
to a “stand-alone device” in the district court’s sense
relied on for summary judgment: a device that is physical-
ly separate and apart from, and not permanently attached
to, a data device (or a host computer). Representative
claim 1 of the ’449 patent begins, “[a]n interface device . . .
comprising the following features,” and then recites the
necessary components of the claimed interface device. See
supra pp. 5–6. Neither the claim language nor the rest of
the intrinsic record supports the district court’s exclusion
of a device that performs the required interface functions
and is installed permanently inside the housing of a
particular data device.
     The district court did not suggest that the term “in-
terface device” by itself implied its construction. Rather,
it heavily relied for its construction on the specific claim
requirement that (to paraphrase) a part of the interface,
upon receiving an identification query from the host
computer, send a signal identifying itself as a host-
familiar device “regardless of the type of the data trans-
mit/receive device attached to the second connecting
device of the interface device.” ’449 Patent, col. 11, lines
63–65. The court concluded that the “regardless” phras-
ing in the claim “strongly indicates that various kinds of
data transmit/receive devices could be attached” to the
interface device. Claim Constr. Op. at 32–33.
    But the court’s construction does not follow from its
understanding of the “regardless” phrase. Nothing about
that phrase forbids any single instance of the claimed
interface device to be permanently attached to a particu-
lar data device. It readily allows permanent attachment
of each copy of the interface device to a particular data
device, prescribing only that the same host-responsive
identification signal be sent regardless of what type of
data device the interface device is attached to. That is,
PAPST LICENSING   v. FUJIFILM CORPORATION                13



there can be multiple copies of the same interface device,
with each permanently attached to one of a variety of
different data devices. The claim language, in short, does
not limit “interface device” to a device not permanently
attached to (readily detachable from) a data device.
    The written description does not do so either. Criti-
cally, the district court’s construction, like the Camera
Manufacturers’ arguments supporting it, fundamentally
mistakes what the description makes clear is the stated
advance over the prior art. As explained supra, the
described advance over the prior art was the elimination
of the need for special drivers to be placed on the host
computer by instead having the host computer use a
single, already-present, fast, reliable driver to communi-
cate with the interface and, through it, with the data
device, which need not be of a particular type. Nothing
about that advance suggests exclusion of a permanent
attachment of such an interface to the data device—a
construction that is “unmoored from, rather than aligned
with” what is described as the invention’s advance. World
Class Tech., 769 F.3d at 1124.
    No passage in the written description says otherwise.
The Camera Manufacturers cite passages that describe
the invention as “sufficiently flexible to permit attach-
ment of very different electrical or electronic systems to a
host device.” ’399 patent, col. 1, lines 56–59; id., col. 7,
lines 45–49 (touting the “present invention” as allowing
“an interface between a host device and almost any data
transmit/receive device”). But that language does not
speak to the connection between the interface and data
devices. Rather, it addresses the connection between the
host computer and data devices, a connection facilitated
by the interface device. Even as to that, the passage may
be read merely to assert the capability of one-to-one host-
to-data-device connections, with the data device chosen
from a wide variety of possible data devices. But even if it
is read to assert a capability of one-to-many host-to-data-
14                 PAPST LICENSING   v. FUJIFILM CORPORATION



device connections, it says nothing to assert that a given
copy of the interface device must be attachable to differ-
ent data devices either simultaneously or seriatim.
    The Camera Manufacturers also point to the written
description’s statement that “[i]n the interface device
according to the present invention an enormous ad-
vantage is to be gained . . . in separating the actual hard-
ware required to attach the interface device to the data
transmit/receive device from the communication
unit,” ’399 patent, col. 8, lines 23–28 (figure numbers
removed)—which they say means that permitting multi-
ple data devices to attach to a single interface device is an
integral part of the invention. But that passage does not
support the district court’s limiting construction, and not
only because it is part of the description of several pre-
ferred embodiments, rather than a clear declaration of
what constitutes an essential part of the invention.
     The full passage makes clear that the “hardware sep-
aration” is not between the interface and data device, but
within the interface device itself—between the second
connecting device, on one hand, and “the digital signal
processor, the memory means[,] and the first connecting
device,” on the other. Id., col. 8, lines 28–29 (figure num-
bers removed). When the passage states that this separa-
tion “allows a plurality of dissimilar device types to be
operated in parallel in identical manner,” it immediately
adds: “Accordingly, many interface devices can be connect-
ed to a host device which then sees many different ‘virtu-
al’ hard disks.” Id. col. 8, lines 30–33 (emphasis added).
The suggestion is that distinct interface devices are used
for distinct data devices, each interface device incorporat-
ing a “second connecting device” that works for its partic-
ular data device. This suggestion works against, rather
than supports, the Camera Manufacturers’ view of multi-
ple data devices attached to a single (separate) interface
device, whether at once or in sequence, for it readily
accommodates a one-to-one permanent attachment of an
PAPST LICENSING   v. FUJIFILM CORPORATION                15



interface device to a data device. And the parallel opera-
tion of dissimilar device types is possible because the
invention causes the host computer to use its native
software to transfer data at high speed and because the
invention creates a uniform interface from the host’s
perspective for controlling the data device. See, e.g., ’399
patent, col. 7, lines 45–49.
    Finally, nothing in the prosecution history supports
the district court’s narrow construction. The Camera
Manufacturers point to an amendment that changed the
claim language from “the type of a device attached” to “a
type of device attached” in what became claim 1 of the
’399 patent. J.A. 391. But there was no accompanying
explanation of the change, which, on its face, does nothing
more than the “regardless” language of claim 1 does, and
that language, as we have explained, does not forbid
permanent attachment. The Camera Manufacturers also
note that the applicant stated that “it is clear that the
data transmit/receive device to be connected to the second
connecting device of the subject interface provides analog
data.” J.A. 389 (emphasis added). Nothing in that state-
ment precludes the connection from being permanent once
made.
                              B
    Papst also appeals the district court’s construction of
the phrase “second connecting device,” which appears in
both patents. 3 The district court construed the term as “a
physical plug or socket for permitting a user readily to


   3    The ’399 and ’449 patent claims use slightly dif-
ferent language, but neither party suggests that the
difference affects the proper construction of “second
connecting device.” Nor does either party argue that the
claim language is means-plus-function language under
what is now codified as 35 U.S.C. § 112(f).
16                 PAPST LICENSING   v. FUJIFILM CORPORATION



attach and detach the interface device with a plurality of
dissimilar data transmit/receive devices.” Claim Constr.
Op. at 43. The parties’ arguments over the proper con-
struction of “second connecting device” largely mirror the
arguments over whether the interface device must be
readily detachable from the data device. See Camera
Manufacturers’ Br. 68 (“As explained above, the claim
language requires the interface device to be connectable
to many different types of [data devices].”); HP’s Br. 3
(“Core to the invention is the ability to attach the inter-
face device to different or multiple data transmit/receive
devices.”). The district court likewise tied its construction
of “second connecting device” to its understanding that
the interface device must be a stand-alone one readily
attachable to and detachable from multiple data devices.
See Claim Constr. Op. at 42, 44.
    We conclude that the district court’s construction of
“second connecting device” is incorrect largely for reasons
we have given for rejecting the “interface device” con-
struction. The district court did not conclude, and the
Camera Manufacturers and HP have not meaningfully
argued, that the ordinary meaning of “second connecting
device” (or “connecting device”) requires a physical plug,
socket, or other structure that permits a user to readily
attach and detach something else. The principal basis for
the district court’s inclusion of those requirements was
the basis we have already rejected—the view that other
claim language and the written description require the
interface device (of which the second connecting device is
a part, according to the claims) to be stand-alone. For
“second connecting device,” the district court added that a
preferred embodiment from the written description in-
cludes pin connectors and other socket-like structures.
See Claim Constr. Op. at 42–44. But we see nothing to
take that embodiment outside the reach of the usual rule
that claims are generally not limited to features found in
what the written description presents as mere embodi-
PAPST LICENSING   v. FUJIFILM CORPORATION                 17



ments, where the claim language is plainly broader.
Phillips, 415 F.3d at 1323.
                              C
    The district court’s construction of the phrase “data
transmit/receive device” is challenged here as well. The
district court construed the phrase to mean “a device that
is capable of either (a) transmitting data to or (b) trans-
mitting data to and receiving data from the host device
when connected to the host device by the interface device.”
Claim Constr. Op. at 39 (emphasis added). The parties’
dispute focuses on the “when connected” portion of the
court’s construction, which the district court understood
to require that the data device be capable of transmitting
data while connected to the host, that is, able to begin
transmitting after the interface device is connected to the
host device. In re Papst Licensing GmbH & Co. KG Litig.,
967 F. Supp. 2d 1, 6–7 (D.D.C. 2013). We reject that
portion of the court’s construction.
                              1
    The Camera Manufacturers initially argue that Papst
may not challenge the district court’s construction be-
cause “the district court adopted word-for-word the con-
struction of [data transmit/receive device] that Papst
proposed.” Camera Manufacturers’ Br. 47. That is an
unreasonable characterization of what occurred in the
district court. The Camera Manufacturers, not Papst,
proposed the bulk of the court’s construction, including
the “when connected” language. Claim Constr. Op. at 37.
Papst proposed a construction without the “when connect-
ed” language, opposing inclusion of that language. Claim
Constr. Op. at 37 (noting “Papst objects to any construc-
tion” but argues in the alternative “that the term may be
construed ‘for context’ as ‘a device that receives input and
provides data to the interface device’ ” (citation omitted)).
When the district court adopted the Camera Manufactur-
ers’ “when connected” language, Papst noticed that the
18                 PAPST LICENSING   v. FUJIFILM CORPORATION



adopted construction, in a respect distinct from the “when
connected” dispute, rested on a misunderstanding of a
patent figure, and it filed a motion identifying the alleged
error and asking the court to modify the adopted con-
struction in the one respect needed to correct it. Papst
limited its motion to that point, leaving the other, al-
ready-contested aspects of the claim construction un-
touched. The district court agreed with Papst and fixed
the construction as urged. Claim Constr. Op. at 39.
     The Camera Manufacturers argue that Papst, having
unsuccessfully opposed a construction with the “when
connected” language, lost its ability to challenge the
adoption of the “when connected” language by not re-
raising the issue when seeking a modification based on a
newly identified issue. See Oral Argument at 33:44–34:10
(arguing that Papst forfeited its challenge because it
requested a modification without “reserv[ing] the ability
to go back later to ask for [its] old construction”). This
contention is wholly without merit. In the district court,
Papst opposed the construction it now opposes, and it was
not required to state its opposition twice. Papst could not
have given the district court the impression that it sud-
denly supported the construction when, in seeking a
modification, it limited its request to a manifest error
resting on a plain misapprehension of the record, rather
than rehashing the broader arguments on claim construc-
tion that the court had fully considered. Papst’s limited
approach in seeking a modification was, indeed, com-
mendably consistent with the general anti-repetition
principle governing requests for reconsideration. See Isse
v. Am. Univ., 544 F. Supp. 2d 25, 29–30 (D.D.C. 2008)
(“ ‘[W]here litigants have once battled for the court’s
decision, they should neither be required, nor without
good reason permitted, to battle for it again.’ ” (citation
omitted)).
PAPST LICENSING   v. FUJIFILM CORPORATION                19



                              2
    We conclude that the data transmit/receive device re-
cited in the preamble to the claims of the ’399 and ’449
patents need not be capable of communicating “when
connected to the host device by the interface device.” (The
parties do not dispute that this language, though appear-
ing in the preamble, is a claim limitation. We proceed on
the assumption that it is.) Nothing about the ordinary
meaning of “data transmit/receive device” suggests any
temporal constraint on the transferring of data. As the
words imply, a data transmit/receive device is a device
that may transmit or receive data; those words offer no
information about when data is transferred.
     To the extent that some claim language does suggest
a temporal constraint, the focus is always on communica-
tions between the interface device and the host computer,
not between the data device and the host computer. For
example, the interface device must send a signal to the
host device “when receiving an inquiry from the host
device as to a type of a device attached.” ’399 patent, col.
12, line 65, to col. 13, line 3. After the interface device
signals to the host device, the interface device must be
able to receive communications from the host device. Id.
col. 13, lines 5–8 (“whereupon the host device communi-
cates with the interface device”). But the claims of both
patents are silent as to when the interface device must
communicate with the data device. If anything, claim 1 of
the ’399 patent tends to suggest that data can already
have been transferred to the interface device from the
data device before it is requested by the host computer:
claim 1 says that the interface device must “interpret a
data request command from the host device . . . as a data
transfer command for initiating a transfer of the digital
data to the host device.” Id. col. 13, lines 10–13 (emphasis
added). Because claim 1 is limited to interface devices
that receive analog data from a data device and then
convert it to digital data, the quoted language seems to
20                PAPST LICENSING   v. FUJIFILM CORPORATION



contemplate that the initiated transfer is of pre-converted
digital data stored on the interface device. Regardless,
the claim language nowhere requires the interface device
to be capable of receiving data that moves from the data
device after connecting to the host.
    The Camera Manufacturers offer no persuasive ar-
gument for why the claim language or any other part of
the specification or prosecution history requires that a
data device be able to communicate with the host “when
connected to the host device by the interface device.” At
most they assert, without significant elaboration, that the
“specification nowhere discloses indefinite storage by the
interface device of data from a [data device].” Camera
Manufacturers’ Br. 51. This assertion does not suggest a
disclaimer of any sort; it merely asserts an absence of
something in the written description. But that absence
must be judged in light of what is plainly present in the
written description—a disclosure of memory that is part
of the interface device. ’399 patent, col. 5, line 52, and
Figure 1. And we have been given no reason at all to
infer, from the absence of more express statements re-
garding use of the disclosed memory in the interface
device for temporary storage of data from the data device,
that the claim should be read to include a textually un-
supported “when connected” requirement regarding
transfer of data to or from the data device.
     The district court, when construing the data-device
claim language, focused almost exclusively on whether
the data device must be capable of both sending and
receiving data. It did not lay out good reasons for adopt-
ing the “when connected” requirement as part of its
construction. Claim Constr. Op. at 37–39; In re Papst
Licensing GmbH & Co. KG Litig., 624 F. Supp. 2d 54, 75–
77 (D.D.C. 2009). Finding no basis for that requirement,
we conclude that the court erred by including that phrase
in its construction.
PAPST LICENSING   v. FUJIFILM CORPORATION                  21



                              D
     The next issue we discuss is the district court’s con-
struction of the phrase “virtual files” in the ’399 patent
and the phrase “simulating a virtual file system” in
the ’449 patent. 4 The district court construed “virtual
files” as “files that appear to be but are not physically
stored; rather, they are constructed or derived from
existing data when their contents are requested by an
application program so that they appear to exist as files
from the point of view of the host device.” Claim Constr.
Op. at 60. The court construed “simulating a virtual file
system” almost identically as “appearing to be a system of
files, including a directory structure, that is not physically
stored; rather, it is constructed or derived from existing
data when its contents are requested by an application
program so that it appears to exist as a system of files
from the point of view of the host device.” Id. at 61. The
district court understood its construction to limit the
“virtual files” of the “virtual file system” to files “not
physically stored on the interface device,” whose content
is data “originating from the data transmit/receive de-
vice.” In re Papst Licensing GmbH & Co. KG Litig., 967
F. Supp. 2d 48, 56 (D.D.C. 2013). We reverse.
    The core of the parties’ disagreement is whether the
“existing data” from which the virtual files are “construct-


    4    The district court did not rely on the construction
of “virtual files” in the ’399 patent in any of its summary-
judgment motions. The term appears only in dependent
claims 7–10 of that patent, which the district court never
addressed because it found that the accused devices lack
elements of the independent claims. Nevertheless, be-
cause the construction of “virtual files” is bound up with
the construction of “simulating a virtual file system” in
the ’449 patent, and because the construction may be
important on remand, we address both phrases now.
22                  PAPST LICENSING   v. FUJIFILM CORPORATION



ed or derived” may already exist on the interface device
when the host requests the virtual file. Although framed
in different ways by the parties, the disagreement is
similar to the dispute over the “when connected” language
of the district court’s construction of “data trans-
mit/receive device.” The Camera Manufacturers argue
that “virtual files” cannot contain data already existing
physically on the claimed interface device; rather, the
data in such files must be present only on the data device,
not the interface device, when requested by the host
device. Papst argues that the phrases “virtual files” and
“simulating a virtual file system” allow the virtual files to
be derived from data already physically stored on the
interface device when the host requests the relevant
virtual file.
     We agree with Papst. Nothing in the claims or writ-
ten description limits a “virtual file” to one whose content
is stored off the interface device, though it includes such
files. “Virtual” conveys some kind of as if action, one
thing emulating another; the term was prominently used
that way in the computer field at the time of the inven-
tions here. See CardSoft v. Verifone, Inc., 769 F.3d 1114,
1117–18 (Fed. Cir. 2014) (discussing Java Virtual Ma-
chine in patent dating to 1998). What is crucial is how
the patent identifies the emulation. In the present con-
text, the emulation does not turn on whether data in a
“virtual file” is physically located in the interface device or
a data device when the host seeks it.
    As we have explained, what the patent describes as
the advance over prior art is the use of a host-native
driver for obtaining access to data even when the data is
not actually on a device of the type for which that driver
was designed—in the featured example, not actually on a
hard drive. Nothing in the written description suggests
that this depends on what non-host physical memory
units hold the data as long as the interface device mimics
the data-organizational tools expected by the host-native
PAPST LICENSING   v. FUJIFILM CORPORATION                 23



driver, such as directory structures for a hard-disk drive,
to enable the host to gain access to it. To impose the
district court’s requirement tied to physical location is to
introduce a meaning of “virtual” that is foreign to what is
described as the invention’s advance. An interface device
file is “virtual” in the only way relevant to the invention
when it organizes data in a manner that allows the host
to use its native driver to gain access to the data even if
the data is not actually on a device for which the native
driver was designed—regardless of where else that data
may be.
    The written description uniformly speaks of the “vir-
tual” files in such data-organization terms, regardless of
physical location in the memory of the interface device or
on the data device. For example, the interface device may
“simulate[] a hard disk with a root directory whose entries
are ‘virtual’ files,” though no hard disk is in fact pre-
sent. ’399 patent, col. 6, lines 1–3. Similarly, in one
embodiment the host device, during its boot sequence
(system startup), sends a request to which the interface
device responds with “a virtual boot sequence,” causing
the host to “assume[] that the interface device according
to a preferred embodiment of the present invention is a
hard disk drive.” Id. lines 26–35 (figure numbers re-
moved). Thereafter, the interface device supplies the host
with data-organization responses consistent with a hard
disk, including “the directory structure of the virtual hard
disk.” Id. lines 40–44. The written description elsewhere
states that, “due to the simulation of a virtual mass
storage device, the data is managed and made available
in such a way that it can be transferred directly to other
storage media, e.g.[,] to an actual hard disk of the host
device.” Id. col. 8, lines 50–55; see also id. col. 12, lines
26–29 (“[B]y simulating a virtual mass storage device, the
interface device is automatically supported by all known
host systems without any additional sophisticated driver
software.” (figure numbers removed)). While all of these
24                   PAPST LICENSING   v. FUJIFILM CORPORATION



examples discuss the organizational structure that the
interface device conveys to the host device, not one men-
tions where data physically resides.
     The point is reinforced by “[o]ther claims of the pa-
tent[s] in question.” Phillips, 415 F.3d at 1314. Claim 1
of the ’449 patent requires a “virtual file system including
a directory structure.” ’449 patent, col. 12, lines 5–6.
Claim 2 explains the types of files that may appear in the
directory structure: “the directory structure has a configu-
ration file . . . or an executable or a batch file . . . or a data
file . . . or a help file.” Id. col. 12, lines 8–13. Enumerat-
ing those types of files as part of the virtual file system
suggests that virtual files may include data physically
stored on the interface device, particularly if the interface
device is stand-alone, which it may be. For example, the
“help file” is “for giving help on handling the interface
device.” Id. col. 12, lines 12–13. A logical place to store
such a file, as indicated by the written description, is on
the interface device. See id. col. 11, line 37 (referring to
“[h]elp files included on the interface device”). So too with
a “configuration file” for “setting and controlling the
functions of the interface device.” Id. col. 12, lines 8–9.
And the written description makes clear that the data for
those files may be stored directly on the interface device.
See, e.g., id. col. 6, lines 50–54 (explaining that storing
files, like the configuration file, “in the memory means of
the interface device” allows “any enhancements or even
completely new functions of the interface device [to] be
quickly implemented” (figure numbers removed)); id. lines
61–67 (“[I]nstallation [on the host device] of certain
routines which can be frequently used . . . is rendered
unnecessary as the EXE files are already installed on the
interface device and appear in the virtual root directo-
ry . . . .” (emphasis added; figure numbers removed)).
Those passages appear at column 7 of the ’399 patent as
well, and a similar analysis applies to claims 7–10 of
the ’399 patent. See ’399 patent, col. 13, lines 33–51.
PAPST LICENSING   v. FUJIFILM CORPORATION                 25



     The written description does refer to one type of vir-
tual file as a “real-time input” file, where the host com-
puter can request a portion of the data from the real-time
input file “whereupon data commences to be received via
the second connecting device and data commences to be
sent to the host device via the first connecting device.” Id.
col. 7, lines 17–22. The written description’s discussion of
real-time input files shows that a virtual file may be
constructed from data residing on the data device. But
nothing in the written description limits virtual files to
that arrangement. Files whose content resides on the
interface device are just as virtual in the relevant respect:
they are accessible by the host’s use of the same driver it
would use if they were present on the actual device for
which the host driver was created even when they are not.
                              E
     Finally, Papst appeals the district court’s construction
of the term “input/output device customary in a host
device” in the ’399 patent and the term “storage device
customary in a host device” in the ’449 patent. The dis-
trict court construed the ’399 term to be a “data in-
put/output device that was normally present within the
chassis of most commercially available computers at the
time of the invention.” Claim Constr. Op. at 55. The
court’s construction for the ’449 patent is identical, except
that the words “data input/output” are replaced with the
word “storage.” Id.
    When a host computer asks the claimed interface de-
vice what type of device it is, the interface device must
respond that it is an “input/output device customary in a
host device” so that the host will communicate with the
interface device using the host’s native software for that
type of device. The parties disagree over whether the
claims require that the device the interface device says it
is be a type of device “normally present within the chas-
sis” of a computer. We hold that the claims are not so
26                 PAPST LICENSING   v. FUJIFILM CORPORATION



limited. The written description makes clear that it is
enough for the device to be one that was normally part of
commercially available computer systems at the time of
the invention.
     Claim 1 of the ’399 patent uses the phrase “in-
put/output device[s] customary in a host device” three
times, first in the preamble when it explains that the host
device comprises “drivers for input/output devices cus-
tomary in a host device,” then twice when it defines how
the interface device and the host computer communi-
cate—the interface device “signals to the host device that
it is an input/output device customary in a host device,”
thereby prompting the host to “communicat[e] with the
interface device by means of the driver for the in-
put/output device customary in a host device.” This
language does not carry a plain, precise meaning of physi-
cal location inside the chassis. The phrase “customary in
a host device” is not especially precise, and it seems to
emphasize what is customary, not whether the unit is
inside or outside the device. It contrasts with, for exam-
ple, “customarily found in” or simply “input/output device
in a host device”—which have a greater suggestion of
location, though themselves perhaps not definitively so.
     For these reasons, we turn to the written description,
which clearly evinces the intended meaning—and meets
even the standard for overriding a seemingly plain mean-
ing of the claim language. The written description shows
that the “in” from “customary in” does not imply physical
location inside a computer chassis. Most starkly, the
patent explains that “[d]rivers for input/output devices
customary in a host device . . . are, for example, drivers for
hard disks, for graphics devices[,] or for printer devic-
es.” ’399 patent, col. 4, lines 27–30 (emphases added). By
its structure—“drivers for X are, for example, drivers for
1, 2, and 3,” thus equating X with 1, 2, and 3—the sen-
tence clearly means that, notably, a printer device is an
example of an “input/output device customary in a host
PAPST LICENSING   v. FUJIFILM CORPORATION                    27



device.” No one contends that a printer device was physi-
cally located inside the chassis of a computer at the time
of the invention.
     In addition, a preferred embodiment of the invention
includes “a 25-pin D-shell connector to permit attachment
to a printer interface of a host device[,] for example.” Id.
col. 9, lines 43–48 (figure numbers removed); see also id.,
Figure 2 (illustrating the D-shell printer connector). The
clear implication is that the preferred embodiment allows
the interface device to connect to the printer interface of
the host computer because the interface device can inform
the host computer that it is a printer and that the host
should communicate with it using its built-in printer
drivers. We do not generally construe the claims of a
patent to exclude a preferred embodiment. Adams Res-
piratory Therapeutics, Inc. v. Perrigo Co., 616 F.3d 1283,
1290 (Fed. Cir. 2010) (“A claim construction that excludes
the preferred embodiment ‘is rarely, if ever, correct and
would require highly persuasive evidentiary support.’ ”
(citation omitted)).
     Further undermining the construction of “customary
in a host device” as “normally found in the chassis of most
commercially available computers” is the fact that the
written description does not equate “host device” with
“computer.” To the contrary, the description uses the
words “host device,” “host systems,” “computer,” and
“computer systems” more or less interchangeably. See,
e.g., ’399 patent, col. 1, lines 20–21 (“host devices or
computer systems are attached by means of an interface
to a device”); id., lines 49–50 (describing an “electronic
measuring device . . . attached to a computer system”); id.
col. 2, lines 1–7 (referring to “host systems” and “comput-
er systems”); id. col. 4, line 60, to col. 5, line 32 (alternat-
ing between “host device,” “host systems,” “computer
system,” and “computer”); id. col. 8, lines 1–22 (similar).
Even if we were to conclude that the phrase “customary
in” conveys a physical location, therefore, the district
28                 PAPST LICENSING   v. FUJIFILM CORPORATION



court was wrong to conclude that the physical location
must be inside a computer chassis. See Pickholtz v.
Rainbow Techs., Inc., 284 F.3d 1365, 1373–74 (Fed. Cir.
2002) (construing “located in the computer” to mean
“located in the CPU, main memory, the CPU or main
memory circuit boards, or qualifying peripherals” based
on the written description’s repeated use of “computer”
and “computer system” interchangeably).
                       CONCLUSION
    For the foregoing reasons, we vacate the district
court’s entry of final judgment and remand for further
proceedings consistent with this opinion.
     Costs are awarded to Papst.
             VACATED AND REMANDED
