  United States Court of Appeals
      for the Federal Circuit
                ______________________

                  CENTRAK, INC.,
                  Plaintiff-Appellant

                           v.

         SONITOR TECHNOLOGIES, INC.,
                Defendant-Appellee
              ______________________

                      2017-2510
                ______________________

    Appeal from the United States District Court for the
District of Delaware in No. 1:14-cv-00183-RGA, Judge
Richard G. Andrews.
                ______________________

              Decided: February 14, 2019
               ______________________

    JEFFREY I. KAPLAN, Kaplan, Breyer, Schwarz, LLP,
Matawan, NJ, argued for plaintiff-appellant. Also repre-
sented by JOSEPH W. BAIN, Shutts & Bowen LLP, West
Palm Beach, FL.

    JACK B. BLUMENFELD, Morris, Nichols, Arsht & Tun-
nell LLP, Wilmington, DE, argued for defendant-appellee.
Also represented by JENNIFER YING.
                 ______________________

   Before REYNA, TARANTO, and CHEN, Circuit Judges.
2                CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




CHEN, Circuit Judge.
     CenTrak, Inc. sued Sonitor Technologies, Inc. for al-
leged infringement of U.S. Patent No. 8,604,909 (’909 pa-
tent), which claims systems for locating and identifying
portable devices using ultrasonic base stations. The dis-
trict court granted Sonitor’s motions for summary judg-
ment that claims 1, 7, 8, 16, 18, 21, 22, and 26 are invalid
for lack of written description and that claims 1, 7, 8, 16,
18, 21, and 22 are not infringed. Because the district court
erred in determining that there were no genuine disputes
of material fact on both issues, we reverse and remand for
further proceedings.
                         BACKGROUND
                     A. Asserted Patent
    The ’909 patent is entitled “Methods and Systems for
Synchronized Ultrasonic Real Time Location.” The ’909
patent relates to systems for real-time location (RTL),
which allow users to locate and identify portable devices in
a facility. ’909 patent col. 1 ll. 16–19, 23–24. Hospitals, for
example, might use RTL systems to track equipment and
patients. The asserted claims generally recite the follow-
ing components: (1) ultrasonic (US) base stations; (2) port-
able devices (i.e., tags); (3) a server; (4) radio frequency (RF)
base stations; and (5) a backbone network that connects the
server with the RF base stations. See, e.g., id. claim 1. The
ultrasonic base stations can be mounted in various fixed
locations in a facility, see id. col. 4 ll. 37–45, such as rooms
in a hospital, and the portable devices can be attached to
people or assets that move between rooms, see id. col. 4 ll.
60–65. Each portable device is configured to detect the ul-
trasonic location codes from the nearby ultrasonic base sta-
tions and “transmit an output signal including a portable
device ID representative of the portable device and the de-
tected ultrasonic location code.” Id., Abstract. While the
portable devices receive location codes from ultrasonic base
stations via ultrasound, they might transmit location and
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                3



device information via RF to an RF base station. Id. col. 2
ll. 59–62. The RF base station then transmits the location
and device ID information obtained from the portable de-
vices to the server. See id. col. 2 ll. 56–66.
    To save power, the ultrasonic base stations and porta-
ble devices do not transmit or receive location information
constantly; instead, they transmit and receive at predeter-
mined times. Id. col. 3 ll. 56–61. To ensure that the com-
ponents remain synchronized, the RF base station can
periodically transmit “timing synchronization information
(TSI) that may provide a unified time of origin to all nodes
in the system.” Id. col. 3 ll. 51–56.
   Claim 1 is illustrative:
   1. A system for determining a location and an iden-
   tity of a portable device, the system comprising:
       means for transmitting timing synchroni-
       zation information including a plurality of
       RF transceivers coupled to a backbone net-
       work and a time server generating the tim-
       ing synchronization information;
       wherein each of the plurality of RF trans-
       ceivers periodically transmits a request to
       the time server to receive the timing syn-
       chronization information;
       a plurality of stationary ultrasonic base
       stations, each ultrasonic base station con-
       figured to receive the timing synchroniza-
       tion information and to transmit a
       corresponding ultrasonic location code in a
       time period based on the received timing
       synchronization information, each ultra-
       sonic location code representative of a loca-
       tion of the respective ultrasonic base
       station; and
4                 CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




         a plurality of portable devices, each porta-
         ble device configured to 1) receive the tim-
         ing synchronization information, 2) detect
         the ultrasonic location codes from the ul-
         trasonic base stations and 3) transmit an
         output signal including a portable device
         ID representative of the portable device
         and the detected location code,
         wherein each portable device is synchro-
         nized to detect the ultrasonic location code
         in the time period based on the received
         timing synchronization information.
Id. col. 14 ll. 25–49.
    Notably, while all claims of the ’909 patent recite “ul-
trasonic” components, the vast majority of the specification
focuses on infrared (IR) or RF components. See, e.g., id. fig.
1 (depicting infrared base stations labeled “IR-BS”). The
’909 patent is a divisional of an application that became
U.S. Patent No. 8,139,945, which contains claims that are
similar to the ones in the ’909 patent but that recite IR
technology instead of ultrasonic technology for communica-
tions from the base stations to nearby portable devices.
Only two sentences of the ’909 patent’s specification dis-
cuss ultrasonic technology:
         Although IR base stations 106 are described, it
    is contemplated that the base stations 106 may also
    be configured to transmit a corresponding BS-ID by
    an ultrasonic signal, such that base stations 106
    may represent ultrasonic base stations. Accord-
    ingly, portable devices 108 may be configured to in-
    clude an ultrasonic receiver to receive the BS-ID
    from an ultrasonic base station.
Id. col. 5 ll. 5–11.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                 5



                   B. Accused Products
    The accused Sonitor Sense system includes three
pieces of hardware sold by Sonitor: RF “gateways,” ultra-
sonic location transmitters, and portable locator tags. See
J.A. 642. Sonitor also provides software for installation on
a customer’s server hardware. J.A. 491 at 25:8–11. When
these components are integrated with a customer’s existing
network and server hardware, CenTrak argues that the re-
sulting system infringes the ’909 patent.
     The parties dispute whether Sonitor personnel or third
parties (who might or might not be hired by Sonitor) phys-
ically install the Sonitor hardware in client hospitals.
Sonitor’s vice president testified that after the hardware is
installed, Sonitor personnel go on site and “configure” the
system. See J.A. 2130 at 27:8–13. CenTrak argues that
the configuration entails bringing location transmitters
online as part of a facility’s existing network. Appellant
Br. 12–13 (citing J.A. 476 at 42:2–14). According to Soni-
tor’s vice president, Sonitor personnel also perform “data
entry” in the server to map the locations of various ultra-
sonic transmitters to their physical locations in a building.
Appellant Br. 14; J.A. 2745 at 29:5–23.
                   C. Procedural History
    CenTrak accuses Sonitor of infringing claims 1, 7, 8, 16,
18, 21, 22, and 26 of the ’909 patent. CenTrak, Inc. v. Soni-
tor Techs., Inc., No. CV 14-183-RGA, 2017 WL 3730617, at
*1 (D. Del. Aug. 30, 2017). Sonitor does not sell all of the
hardware necessary to practice the asserted claims, so
while CenTrak asserted various theories of infringement
before the district court, on appeal, CenTrak has only pur-
sued a theory under 35 U.S.C. § 271(a) that Sonitor
“makes” infringing systems when it installs and configures
the Sonitor Sense system. See Appellant Br. 1, 23. Cen-
Trak asserts only direct infringement. J.A. 2823 at 47:3–
5.
6               CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




    Sonitor filed motions for summary judgment of non-in-
fringement, J.A. 89, and invalidity for lack of written de-
scription and enablement, J.A. 3831. 1
    Sonitor’s main non-infringement argument was that
Sonitor does not make, use, or sell certain elements recited
in the claims, including the required backbone network,
Wi-Fi access points, or server hardware. J.A. 95. CenTrak
responded that the party assembling components into the
claimed assembly “makes” the patented invention, even
when someone else supplies most of the components.
J.A. 129. The district court ordered supplemental briefing
so that CenTrak could identify evidence in support of its
“final assembler” theory. See J.A. 2826–27 at 61:21–62:9.
    Regarding written description, Sonitor argued that the
two sentences in the specification dedicated to ultrasound,
quoted above, did not show that the inventors had posses-
sion of an ultrasound-based RTL system. See J.A. 3839–
49.
    The district court granted summary judgment of non-
infringement. It held that a defendant must be the actor
who assembles the entire claimed system to be liable for
direct infringement, and CenTrak had not submitted proof
that Sonitor personnel had made an infringing assembly.
CenTrak, 2017 WL 3730617, at *6. The district court also
ruled that CenTrak’s infringement theory based on Sonitor
allegedly undertaking the final act that completes assem-
bly by “assigning location codes” was “entirely new.” Id. at
*5 n.3. The district court ruled that even if it were to con-
sider this theory, “[s]imply entering the data into a server
does not constitute making the physical system claimed in
the ’909 patent.” Id.



    1   Sonitor moved for summary judgment of non-in-
fringement on all asserted claims except claim 26. It di-
rected its invalidity motion to all asserted claims.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                   7



    Regarding invalidity, the district court ruled that while
the specification “contemplated” ultrasound, “[m]ere con-
templation . . . is not sufficient to meet the written descrip-
tion requirement.” Id. at *8. The district court reasoned
that “electromagnetic radiation and sound waves are not
simply two species of the same genus; rather these are two
completely different types of phenomena” and that “one
could not simply drop [an ultrasonic] transmitter into the
system as disclosed in the specification and have a func-
tioning [ultrasonic] system.” Id. Accordingly, it granted
summary judgment that CenTrak’s claims did not satisfy
the written description requirement. Id. at *9. The district
court did not rule on the issue of enablement, id. at *7 n.4,
and denied other pending motions as moot. Id. at *9.
    Sonitor appeals. We have jurisdiction under 28 U.S.C.
§ 1295(a)(1).
                         DISCUSSION
    A district court’s grant of summary judgment is re-
viewed under the law of the regional circuit. Profectus
Tech. LLC v. Huawei Techs. Co., 823 F.3d 1375, 1379 (Fed.
Cir. 2016). “The Third Circuit reviews grants and denials
of motions for summary judgment de novo, applying the
same standard of review as the district court.” Mo-
bileMedia Ideas LLC v. Apple Inc., 780 F.3d 1159, 1164
(Fed. Cir. 2015) (citing Gonzalez v. Sec’y of Dep’t of Home-
land Sec., 678 F.3d 254, 257 (3d Cir. 2012)). When review-
ing a grant of summary judgment, we view the facts in the
light most favorable to the nonmoving party and draw all
inferences in that party’s favor. Gonzalez, 678 F.3d at 257.
                   A. Written Description
     We have held that “the test for sufficiency” of a patent’s
written description “is whether the disclosure of the appli-
cation relied upon reasonably conveys to those skilled in
the art that the inventor had possession of the claimed sub-
ject matter as of the filing date.” Ariad Pharm., Inc. v. Eli
8                CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




Lilly & Co., 598 F.3d 1336, 1351 (Fed. Cir. 2010) (en banc).
“[T]he test requires an objective inquiry into the four cor-
ners of the specification from the perspective of a person of
ordinary skill in the art. Based on that inquiry, the speci-
fication must describe an invention understandable to that
skilled artisan and show that the inventor actually in-
vented the invention claimed.” Id. A “mere wish or plan”
for obtaining the claimed invention does not satisfy the
written description requirement. Regents of the Univ. of
Cal. v. Eli Lilly & Co., 119 F.3d 1559, 1566 (Fed. Cir. 1997).
The issue of whether a claimed invention satisfies the writ-
ten description requirement is a question of fact. Ariad,
598 F.3d at 1351.
    The district court determined that the ’909 patent
lacked adequate written description support for an RTL
system that relied on ultrasound-based communication
from the base stations to the portable devices. The district
court found that IR and ultrasound are “fundamentally dif-
ferent” technologies, in part because IR radiation travels at
approximately 300 million meters per second, while ultra-
sonic sound waves propagate at approximately 340 meters
per second in air. CenTrak, 2017 WL 3730617, at *8. Be-
cause “[t]iming is critical to the technology disclosed in the
’909 patent,” the district court found, these speed differ-
ences “would necessarily require a significantly different
solution if implemented using IR than if [ultrasound] were
used.” Id. at *9. The district court also cited inventor tes-
timony that interference from reflection and echoes is dif-
ferent in IR and ultrasonic systems. Id. (citing J.A. 442).
The district court reasoned that because the ’909 patent’s
written description does not discuss how to address propa-
gation delays or interference in ultrasonic systems, the pa-
tent does not show that the inventors had possession of the
claimed invention as of the filing date. Id.
    CenTrak argues that the district court’s written de-
scription ruling erred by effectively requiring the specifica-
tion to disclose basic, routine implementation details for
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                   9



how a portable device can receive location and timing syn-
chronization information from a neighboring base station
using an ultrasound signal. In CenTrak’s view, a skilled
artisan reading the ’909 patent’s specification, with an un-
derstanding of the basics of IR and ultrasonic signals,
would understand that the inventors had possession of
RTL systems that could use either IR or ultrasound, and
not merely an unformed wish or plan for an ultrasonic al-
ternative. CenTrak further contends that the district
court’s invalidity analysis falls more in line with an enable-
ment theory, which CenTrak believes its claims also sat-
isfy. 2
     As CenTrak correctly points out, a patented invention
must satisfy separate written description and enablement
requirements. Ariad, 598 F.3d at 1351. The governing
statute states, in relevant part: “The specification shall
contain a written description of the invention, and of the
manner and process of making and using it, in such full,
clear, concise, and exact terms as to enable any person
skilled in the art . . . to make and use the same . . . .” 35
U.S.C. § 112, ¶ 1 (2006). 3 One purpose of this statutory
provision is to require an inventor to provide sufficient de-
tail in a patent’s specification to enable a person of ordinary
skill in the art to make and use the invention. But a sepa-
rate purpose of this text “is to ‘ensure that the scope of the
right to exclude, as set forth in the claims, does not over-
reach the scope of the inventor’s contribution to the field of



    2    As noted above, the district court declined to reach
the parties’ enablement arguments on summary judgment.
    3    Because the application resulting in the ’909 pa-
tent was filed before September 16, 2012, the effective date
of the amendments to 35 U.S.C. § 112 enacted in the
Leahy–Smith America Invents Act (AIA), Pub. L. No. 112–
29, § 4(c), (e), 125 Stat. 284, 296, 297 (2011) we refer to the
pre-AIA version of § 112.
10               CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




art as described in the patent specification.’” Univ. of Roch-
ester v. G.D. Searle & Co., 358 F.3d 916, 920 (Fed. Cir.
2004) (quoting Reiffin v. Microsoft Corp., 214 F.3d 1342,
1345 (Fed. Cir. 2000)). Thus, we have explained, “written
description is about whether the skilled reader of the pa-
tent disclosure can recognize that what was claimed corre-
sponds to what was described; it is not about whether the
patentee has proven to the skilled reader that the inven-
tion works, or how to make it work, which is an enablement
issue.” Alcon Research Ltd. v. Barr Labs., Inc., 745 F.3d
1180, 1191 (Fed. Cir. 2014).
     In this case, genuine issues of material fact remain as
to whether disclosure of the implementation details that
the district court identified is necessary to satisfy the writ-
ten description requirement. The considerations relied on
by the district court and Sonitor do not compel summary
judgment for lack of written description. As an initial mat-
ter, the district court leaned heavily on the fact that the
specification devoted relatively less attention to the ultra-
sonic embodiment compared to the infrared embodiment.
But in ScriptPro LLC v. Innovation Associates, Inc., 833
F.3d 1336, 1341 (Fed. Cir. 2016), we explained that “a spec-
ification’s focus on one particular embodiment or purpose
cannot limit the described invention where that specifica-
tion expressly contemplates other embodiments or pur-
poses.”
     Here, as in ScriptPro, the fact that the bulk of the spec-
ification discusses a system with infrared components does
not necessarily mean that the inventors did not also con-
structively reduce to practice a system with ultrasonic com-
ponents. Sonitor attempts to distinguish ScriptPro on the
basis that the specification at issue disclosed multiple prob-
lems and multiple, exemplary solutions, but “the written
description requirement does not demand either examples
or an actual reduction to practice; a constructive reduction
to practice” may be sufficient if it “identifies the claimed
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                11



invention” and does so “in a definite way.” Ariad, 598 F.3d
at 1352.
     Sonitor’s citation to cases finding inadequate written
description to support summary judgment here is unper-
suasive. The ’909 patent’s disclosure of an ultrasonic em-
bodiment, albeit brief, distinguishes the instant case from
Rivera v. International Trade Commission, 857 F.3d 1315,
1322 (Fed. Cir. 2017), in which we affirmed an invalidity
finding because the specification at issue did not make any
mention of the later-claimed container with an integrated
filter and thus did not provide written description for such
a container.
    The ’909 patent’s express disclosure also distinguishes
this case from Lockwood v. American Airlines, Inc., 107
F.3d 1565 (Fed. Cir. 1997), on which Sonitor relies. In
Lockwood, we affirmed a summary judgment ruling that a
patent was not entitled to an earlier priority date because
its parent applications did not make any reference to an
“individual merchandising apparatus that contained video
disk players or other equivalent storage means,” which was
a claimed limitation. Id. at 1572. We found that testimony
by Lockwood’s expert arguing that such a feature “would
have been apparent to one skilled in the art” was insuffi-
cient to “raise a genuine issue of material fact” because it
was undisputed that one of the intervening applications
did not disclose the claimed feature. Id. Here, in contrast,
the specification at least mentions base stations and receiv-
ers that use ultrasound, which makes this case distinguish-
able from Lockwood. 4



    4   Sonitor also argues that the patentee’s original dis-
closure fails to describe other claimed features such as the
“ultrasonic detector” recited in claim 7 or “concurrently”
transmitting ultrasonic location codes as required by claim
8. Appellee Br. 54. Because the district court did not base
12               CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




    Sonitor argues that although the ’909 patent’s specifi-
cation mentions ultrasonic communication between base
stations and portable devices, the disclosure is insufficient,
because, according to Ariad, “generic claim language ap-
pearing in ipsis verbis in the original specification does not
satisfy the written description requirement if it fails to sup-
port the scope of the genus claimed.” 598 F.3d at 1350.
While it is true that a specification’s passing reference to
generic claim language, without more, may not adequately
support claims to a broad genus, we do not believe that
CenTrak’s claims to an ultrasonic RTL embodiment are
akin to claiming a vast genus based on a limited disclosure
of a species. The district court’s analysis ignores the fact
that at least some components recited in the claims, such
as the “RF transceivers” and “backbone network” recited in
claim 1, do not depend on IR or ultrasound. The question
here is the level of detail the ’909 patent’s specification
must contain, beyond disclosing that ultrasonic signals can
be used, to adequately convey to a skilled artisan that the
inventors possessed an ultrasonic embodiment. As we ex-
plained in Ariad, “the level of detail required to satisfy the
written description requirement varies depending on the
nature and scope of the claims and on the complexity and
predictability of the relevant technology.” Id. at 1351.
     In this case, the parties disputed the complexity and
predictability of ultrasonic RTL systems, and the district
court erred at the summary judgment stage by not suffi-
ciently crediting testimony from CenTrak’s expert that the
differences between IR and ultrasound, when used to
transmit small amounts of data over short distances, are
incidental to carrying out the claimed invention. Cen-
Trak’s expert opined that “[a] 2 byte location code would
allow identification of up to 65,000 different locations” and



its decision on these limitations, we do not address them in
the first instance on appeal.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                  13



that “transmitting 2 bytes of ultrasonic data, regardless of
the transmission speed, would certainly pose no obstacle
and require no special instructions for a POSITA [person
of ordinary skill in the art] using a standard ultrasonic
transmitter at the time of the invention.” J.A. 882. He also
opined that “[t]iming synchronization can be derived from
. . . almost any amount of information ranging from a sin-
gle start bit up to several bytes of date/time or timing offset
data” and that “receiving several bytes of data from an ul-
trasonic signal would pose no obstacle . . . using a standard
[u]ltrasonic receiver.” J.A. 883. In the context of the ’909
patent, the expert characterized IR and ultrasonic technol-
ogies as “interchangeable.” J.A. 901. Indeed, CenTrak
points out that many features of the claimed system, such
as the backbone network, time server, and RF transmitters
do not depend on whether the base stations in each room
communicate with portable tags using IR or ultrasound.
On the other hand, Sonitor’s expert opined that the speed
of ultrasonic signals “is roughly a million times slower than
light,” J.A. 1414, and that “ultrasound would take hun-
dreds of times longer than infrared to transmit the same
amount of data,” J.A. 1416. Moreover, Sonitor argues that
“[t]he specification is entirely silent about the structure of
ultrasonic base stations or receivers.” Appellee Br. 50. But
the testimony from CenTrak’s expert cited above suggests
that those details were not particularly complex or unpre-
dictable, and Sonitor does not explain why a person of or-
dinary skill in the art would need to see such details in the
specification to find that the named inventors actually in-
vented the claimed system. This, at the very least, pre-
sents a material factual issue still in dispute.
    Putting aside the testimony of CenTrak’s expert, Soni-
tor argues that the named inventors actually admitted that
the ’909 patent’s specification does not disclose certain ul-
trasonic limitations. For example, one of the inventors, Dr.
Amir, testified as follows:
14                CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




     Q. But there’s no ultrasonic portable device that is
     actually described in the ’909 patent; right?
     A. This is correct, yeah.
     Q. And there’s no ultrasonic base station that is ac-
     tually described in the ’909 patent; correct?
     A. Yes. It’s not explicitly, correct.
J.A. 447 at 166:24–167:5. In another exchange, however,
Dr. Amir suggested that it would be simple for a person of
ordinary skill to adjust for the differences between IR and
ultrasound:
     Q. And nothing in the ’909 patent teaches a person
     specifically how to create or develop an RTLS sys-
     tem using ultrasonic signals; correct?
     THE WITNESS: I disagree with you because I
     think it’s almost like -- I can think about some ex-
     ample, but I can’t think of it right now. The teach-
     ing -- once you have the teaching of the concept, the
     reduction to practice is immediate. I don’t explain
     how to really even do the IR to this extent.[5] The
     only thing that’s missing is understanding the rel-
     ative ratios and understanding how ultrasound
     propagates to make it work. You have to under-
     stand how to drive an ultrasonic transmitter, how
     to receive an ultrasonic signal, and how to process
     them. But this is known art to people who are
     knowing ultrasound.
     Q. But none of that knowledge of ultrasound is in
     your ’909 patent; correct?



     5   Sonitor disputes Dr. Amir’s suggestion that the
level of detail in ’909 patent regarding IR and ultrasound
is similar. See Appellee Br. 31; ’909 patent col. 13 l. 20–
col. 14 l. 16.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                 15



    A. Correct.
J.A. 447 at 167:6–168:1 (objection omitted).
     Although Sonitor seems to treat this testimony as con-
clusive proof that the inventors did not “possess” an ultra-
sonic RTL system, we do not read this testimony as an
admission, as a matter of law, that the specification does
not adequately describe an ultrasonic embodiment. In con-
text, a reasonable fact finder could interpret Dr. Amir’s tes-
timony not as a legal conclusion regarding written
description, but as an acknowledgement that the specifica-
tion did not literally detail the inner workings of ultrasonic
devices or identify particular examples of such devices be-
cause such details were known to skilled artisans and not
part of the inventors’ inventive contribution. As explained
above, however, it is not clear to us that a person of ordi-
nary skill in the art would require disclosure of such details
to find that the named inventors actually invented an ul-
trasonic embodiment.
    Based on the evidence of record, there is a material dis-
pute of fact as to whether the named inventors actually
possessed an ultrasonic RTL system at the time they filed
their patent application or whether they were “leaving it to
the . . . industry to complete an unfinished invention.” No-
vozymes A/S v. DuPont Nutrition Biosciences APS, 723
F.3d 1336, 1350 (Fed. Cir. 2013) (quoting Ariad, 598 F.3d
at 1353). Thus, the district court erred in granting sum-
mary judgment.
                       B. Enablement
     Sonitor argues that if we reverse the district court on
written description, we should nevertheless rule that the
asserted claims are invalid for lack of enablement. The dis-
trict court concluded that it need not consider enablement
because of its written description ruling. CenTrak, 2017
WL 3730617, at *7 n.4. Although an “appellee may, with-
out taking a cross-appeal, urge in support of a decree any
16              CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




matter appearing in the record,” United States v. Am. Ry.
Express Co., 265 U.S. 425, 435 (1924), in this case we de-
cline to reach the question of enablement for the first time
on appeal, see TypeRight Keyboard Corp. v. Microsoft
Corp., 374 F.3d 1151, 1160 (Fed. Cir. 2004) (reversing sum-
mary judgment of obviousness and declining to reach issue
of non-infringement that district court had not addressed).
                      C. Infringement
     CenTrak argues that the district court applied an in-
correct legal standard to the infringement question and
that Sonitor makes a system covered by the claims when it
completes the installation of the Sonitor Sense system in a
hospital. 6 Sonitor responds that we should reject Cen-
Trak’s “final assembly” theory as untimely, that the dis-
trict court applied the correct legal standard, and that
CenTrak failed to present sufficient evidence to prove in-
fringement. We address each of these issues in turn.
                       1. Timeliness
    Sonitor argues that we should not consider CenTrak’s
“final assembly” theory—the main infringement theory
that CenTrak presents on appeal—because CenTrak did
not timely present it to the district court. As explained be-
low, we find Sonitor’s argument unpersuasive.
    On appeal, CenTrak presents a range of arguments for
how Sonitor infringes the claimed system. First, CenTrak
argues that the conduct of Sonitor’s customers in installing
the claimed backbone network, RF transceivers (wireless
access points), and other hardware is attributable to Soni-
tor. Second, CenTrak argues that Sonitor personnel



     6  CenTrak also asserted an infringement theory be-
fore the district court based on “using” the claimed system,
but CenTrak’s appellate briefs only pursue a theory based
on Sonitor “making” an infringing system.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                 17



configure ultrasonic location transmitters to work with
customers’ networks. Third, CenTrak argues that Sonitor
personnel enter into the Sonitor server a system of location
codes and corresponding physical locations at which each
ultrasonic location transmitter was installed.
     Sonitor concedes that CenTrak presented its first argu-
ment regarding installation-as-infringement in its opposi-
tion brief to Sonitor’s summary judgment motion, see
Appellee Br. 38; J.A. 130, but Sonitor argues that CenTrak
did not present its second or third arguments regarding
configuration and entering location codes during summary
judgment briefing. We disagree with Sonitor and find that
CenTrak’s arguments were adequately preserved. Cen-
Trak’s district court opposition brief argues that the instal-
lation process for an accused system involves, among other
things, “installing the software to make the Sonitor server”
and “integrating the entire system into the customer’s net-
work.” J.A. 127–28. This argument, while briefly pre-
sented, is substantially the same as CenTrak’s
“configuration” argument on appeal. See Appellant Br. 26
(citing testimony that Sonitor’s vice president “assists the
Sonitor support team if they are doing an installation and
have trouble getting the installed devices to come on line
on the [customers] network.” (emphasis and internal quo-
tation marks omitted)). CenTrak also argued, with cita-
tions to deposition testimony, that Sonitor “personnel also
enter the location data on the virtual server . . . where the
Sonitor software was installed during installation.” Cen-
Trak, 2017 WL 3730617, at *5 (quoting J.A. 128); J.A. 2745
at 29:2–23. CenTrak further argued that “the party assem-
bling components into the claimed operable assembly is the
direct infringer making the patented invention, even when
most or all of those components are supplied by other par-
ties.” J.A. 129 (citing Cross Med. Prods., Inc. v. Medtronic
Sofamor Danek, Inc., 424 F.3d 1293, 1311 (Fed. Cir. 2005)).
In context, CenTrak’s opposition brief was arguing that
Sonitor performed the final setup to create a completed,
18              CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




infringing system. Thus, we disagree with Sonitor’s con-
tention that CenTrak’s configuration and location code ar-
guments did not appear in CenTrak’s summary judgment
briefs. 7
     We are also unpersuaded by Sonitor’s argument that
CenTrak failed to present its infringement theories based
on “making” during discovery. CenTrak’s First Amended
Complaint accuses Sonitor of infringing by “making, using,
marketing, testing, selling, installing, supporting or im-
porting . . . the Sonitor Sense™ RTLS.” J.A. 56 ¶ 30.
While mere allegations in an unverified complaint gener-
ally cannot defeat summary judgment, CenTrak’s expert
also supported CenTrak’s position, opining that
“SONITOR either provides or configures every component
of the SONITOR Sense system” and that all ultrasonic lo-
cation transmitters “are provided and configured by
SONITOR.” J.A. 797. He further opined that “each of the
components of the SONITOR Sense portion of the backbone
is configured by SONITOR.” J.A. 798. We are troubled by
CenTrak’s incomplete response to Sonitor’s interrogatory
seeking CenTrak’s infringement contentions, which does
not specify “the supplier, vendor, or other entity that pro-
vides such product, service, software, function, or [accused]
instrumentality,” as Sonitor requested. J.A. 1742–43; see
J.A. 2133–81. However, it does not appear that Sonitor
moved to compel a more complete response or argued that
the district court should disregard portions of CenTrak’s
summary judgment opposition brief that went beyond the
scope of its interrogatory response. Under these circum-
stances, we cannot say that CenTrak failed to preserve its
infringement arguments for appeal.



     7  Additionally, the district court was mistaken when
it characterized CenTrak’s location code argument as “an
entirely new theory of infringement.” CenTrak, 2017 WL
3730617, at *5 n.3.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                19



            2. Infringement by Final Assembly
    “Infringement is a question of fact.” Medgraph, Inc. v.
Medtronic, Inc., 843 F.3d 942, 949 (Fed. Cir. 2016). Direct
infringement can be found when a defendant makes a prod-
uct containing “each and every limitation set forth in a
claim.” Cross Med., 424 F.3d at 1310.
     The district court found that CenTrak did not present
sufficient evidence to raise a triable issue of fact as to
whether Sonitor makes infringing systems. It is undis-
puted that Sonitor does not provide certain claimed ele-
ments in the accused systems, such as a backbone network,
Wi-Fi access points, or server hardware. Moreover, the dis-
trict court analyzed the evidence CenTrak offered and con-
cluded that no reasonable jury could find that Sonitor
“made” the claimed invention by performing installations.
See CenTrak, 2017 WL 3730617, at *4–6.
    The district court and Sonitor relied on Centillion Data
Systems, LLC v. Qwest Communications International,
Inc., 631 F.3d 1279 (Fed. Cir. 2011) for the proposition that
to “make” a system, a single entity must assemble the en-
tire system itself. CenTrak, 2017 WL 3730617, at *6. In
Centillion, we held that Qwest, which provided software to
customers, did not “make” a patented phone billing system
requiring a “back-end” system maintained by a service pro-
vider and a “front-end” system maintained by an end user.
631 F.3d at 1288. We explained that “to ‘make’ the system
under § 271(a), Qwest would need to combine all of the
claim elements” but that “[t]he customer, not Qwest, com-
pletes the system by providing the ‘personal computer data
processing means’ and installing the client software.” Id.
Sonitor argues that like Qwest, it does not directly infringe
because it makes only part of a claimed system.
    Sonitor and the district court misunderstand Cen-
Trak’s argument. CenTrak’s infringement theory is com-
paring Sonitor not to the software maker Qwest, but to
Qwest’s customers, who completed the claimed system by
20              CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




installing Qwest’s software onto their own hardware.
Qwest’s customers were not named defendants in Centil-
lion, 8 and thus, according to CenTrak, Centillion does not
rule out CenTrak’s infringement theory. In this case, Cen-
Trak argues that the final, missing elements are the con-
figuration that allows the location transmitters to work
with the network and the location codes that are entered
into the Sonitor server. According to CenTrak, admissible
evidence that Sonitor is the “final assembler” raises a tria-
ble issue of fact on infringement even though Sonitor does
not “make” each of the claimed components of the accused
systems.
    CenTrak primarily relies on two cases in support of its
argument that Sonitor infringes when it performs an act
that completes an infringing assembly. In Cross Medical,
we analyzed claims to surgical implants that would in-
fringe when brought in contact with a patient’s bone. We
held that Medtronic, the manufacturer of the accused de-
vice, did not infringe because it “does not itself make an
apparatus with the ‘interface’ portion in contact with
bone.” 424 F.3d at 1311. Instead, we explained, “if anyone
makes the claimed apparatus, it is the surgeons” who in-
stalled the devices. Id.
    Sonitor argues that, like Medtronic, it does not make
the entire system alleged to infringe. But Sonitor’s argu-
ment misses the mark again because CenTrak is arguing
that Sonitor stands in the shoes of the surgeons, who acted
as potentially infringing final assemblers in Cross Medical,
and not in the position of the medical device maker.




     8  We also held in Centillion that Qwest was not vi-
cariously liable for its customers’ conduct. 631 F.3d at
1288. CenTrak’s “final assembly” theory focuses solely on
Sonitor’s actions, not those of its customers or others.
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                 21



    CenTrak also cites Lifetime Industries, Inc. v. Trim-
Lok, Inc., 869 F.3d 1372 (Fed. Cir. 2017), in which we ana-
lyzed claims to a two-part seal used on a recreational vehi-
cle with a slide-out room. The defendant made only the
seal, not the RV, but we held that an allegation that the
defendant installed the seal on an RV was sufficient to
state a claim for direct infringement:
    Although Lifetime did not allege that Trim-Lok
    made the RV onto which it installed the seal, Life-
    time did allege that Trim-Lok installed the seal
    onto the RV; that is, Lifetime alleged that Trim-
    Lok made an infringing seal-RV combination. Be-
    cause Lifetime alleged that an agent of Trim-Lok
    installed the seal onto the RV, and that the result-
    ing seal-RV combination infringed the ’590 patent,
    it alleged that Trim-Lok directly infringed in a
    manner consistent with our precedents holding
    that assembling the components of an invention is
    an infringing act of making the invention.
Id. at 1378 (citation omitted).

    Sonitor responds that Lifetime involved a motion to dis-
miss rather than summary judgment and that CenTrak
has provided insufficient proof of infringement. But Soni-
tor does not challenge the core holding of Lifetime that as
long as a defendant adds the final limitations to complete
a claimed combination, the defendant infringes. Under
Lifetime and Cross Medical, a final assembler can be liable
for making an infringing combination—assuming the evi-
dence supports such a finding—even if it does not make
each individual component element.
           3. CenTrak’s Infringement Evidence
    With the above framework in mind, we find that Cen-
Trak’s cited evidence raises a triable issue of fact regarding
infringement.
22              CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




     On the question of whether Sonitor or its agents phys-
ically install components of the accused systems, a Sonitor
employee testified that Sonitor employees “aren’t the main
installers typically.” J.A. 2775 at 77:16–22 (emphasis
added). But the witness noted that Sonitor’s vice president
of technical and customer support “oversees the installa-
tion.” J.A. 2770 at 25:4–9, 18–24. Sonitor’s VP testified
that “resellers or a subcontractor” perform the installation.
Appellee Br. 43 (quoting J.A. 2130 at 27:22–23). The dis-
trict court noted testimony that Sonitor has “integration
agreement[s]” with third parties. CenTrak, 2017 WL
3730617, at *5 (citing J.A. 2772–73 at 62:24–63:8). The
district court found this evidence insufficient to create a
material issue of fact, but we disagree. Part of CenTrak’s
infringement theory is that Sonitor “integrat[es] the entire
system into the customer’s network.” J.A. 128. An “inte-
gration agreement” could constitute circumstantial evi-
dence that Sonitor hired a contractor to build at least part
of an infringing system.
      But even if a third party who does not work for Sonitor
installed all claimed hardware, CenTrak argues that Soni-
tor would still infringe by configuring the Sonitor ultra-
sonic location transmitters to integrate with the customer’s
network and by entering location codes into the Sonitor
server software to associate location transmitters with lo-
cations in the facility. CenTrak notes that claim 1 contains
a limitation requiring the base stations to be “configured to
. . . transmit a corresponding ultrasonic location code . . .
each ultrasonic location code representative of a location of
the respective ultrasonic base station.” According to Cen-
Trak, the accused system is not an operable assembly until
it is configured.
    CenTrak cites testimony from Sonitor’s VP that Soni-
tor employees “go on site and configure our system.”
J.A. 2130 at 27:8–11. The VP further testified that before
a system “goes live,” Sonitor employees will take drawings
prepared by an “installation company . . . illustrating what
CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.                  23



devices were put into which locations” and that Sonitor will
then “take that data and create a system with it, that sys-
tem is then put into the server on site.” Appellant Br. 27
(quoting J.A. 2745 at 29:5–23). He further testified that
Sonitor personnel “are the ones who do the data entry for
that system and then they go out and tune the system to
ensure it functions normally.” Id. Based on this testimony,
a reasonable jury could find that before an accused Sonitor
system goes online, Sonitor personnel complete at least a
portion of the final system configuration and software
setup necessary to make the system work—in other words,
that Sonitor makes a combination of hardware and soft-
ware that is “configured” to infringe.
     CenTrak argues that based on Sonitor’s failure to dis-
pute CenTrak’s configuration and data entry evidence, the
district court should have granted summary judgment of
infringement in favor of CenTrak. This argument does not
address the fact that the district court declined to analyze
all of Sonitor’s non-infringement defenses in light of its rul-
ing regarding “making.” CenTrak, 2017 WL 3730617, at *4
n.2. Moreover, the record before us does not conclusively
show who installs each claimed element or who, if anyone,
completes an infringing combination. Thus, we decline
CenTrak’s request for an order that the district court grant
partial summary judgment of infringement. Moreover, we
need not decide whether CenTrak’s request for summary
judgment, which CenTrak made in its opposition brief to
Sonitor’s motion for summary judgment and not in a sepa-
rate filing, was procedurally proper. CenTrak’s motion to
consider additional authority (ECF No. 72) is denied as
moot.
    Based on the record before us, the district court erred
in ruling that there were no genuine issues of material fact
and that Sonitor was entitled to summary judgment on the
24               CENTRAK, INC. v. SONITOR TECHNOLOGIES, INC.




issue of “making.” 9 We therefore reverse and remand for
further proceedings.
             REVERSED AND REMANDED
                           COSTS
     Costs to Appellant.




     9   CenTrak argues that on remand, it should be al-
lowed to take additional discovery to address an argument
it claims Sonitor made for the first time after summary
judgment briefing was complete, namely, that Sonitor per-
sonnel do not install any accused hardware. We do not
agree that this argument was untimely. The record shows
that Sonitor served an interrogatory response during dis-
covery stating: “Sonitor has not infringed any of the As-
serted Claims because certain claimed limitations such as
the ‘backbone network’ are not provided by Sonitor.”
J.A. 1266. To the extent that CenTrak wanted additional
detail into which specific elements Sonitor contended were
provided by others, CenTrak has not explained why the dis-
trict court’s discovery schedule was insufficient to seek
such information. Accordingly, we ultimately leave the de-
cision of whether to reopen discovery to the discretion of
the district court, but we decline to order the district court
to reopen discovery on remand.
