  United States Court of Appeals
      for the Federal Circuit
                   __________________________

IN RE KATZ INTERACTIVE CALL PROCESSING
                     PATENT LITIGATION
 ---------------------------------------------------------------------------
RONALD A. KATZ TECHNOLOGY LICENSING LP,
                         Plaintiff-Appellant,
                                    v.
                AMERICAN AIRLINES, INC.,
                   Defendant-Appellee,
                                   and
  FEDEX CORPORATE SERVICES, INC., FEDEX
              CORPORATION,
 FEDEX CUSTOMER INFORMATION SERVICES,
                    INC.,
    AND FEDERAL EXPRESS CORPORATION,
             Defendants-Appellees,
                                   and
DHL EXPRESS (USA), INC., DHL HOLDINGS (USA),
                    INC.,
          AND SKY COURIER, INC.,
             Defendants-Appellees,
                                   and
     U.S. BANCORP AND U.S. BANK NATIONAL
                 ASSOCIATION,
               Defendants-Appellees,
                                   and
RONALD A KATZ TECH   v. AMERICAN AIR                   2

   TIME WARNER CABLE, INC., TIME WARNER
        ENTERTAINMENT COMPANY, L.P.,
    TIME WARNER NY CABLE LLC, AOL, LLC,
  COMPUSERVE INTERACTIVE SERVICES, INC.,
      NETSCAPE COMMUNICATIONS CORP.,
CHARTER COMMUNICATIONS ENTERTAINMENT
 I LLC, CHARTER COMMUNICATIONS HOLDING
 COMPANY LLC, CHARTER COMMUNICATIONS
              OPERATING LLC,
     AND CHARTER COMMUNICATIONS, INC.,
                 Defendants,
                            and
    CSC HOLDINGS, INC. (NOW KNOWN AS CSC
   HOLDINGS, LLC), CABLEVISION SYSTEMS
 CORPORATION, CABLEVISION SYSTEMS NEW
          YORK CITY CORPORATION,
     CABLEVISION OF BROOKHAVEN, INC.,
       CABLEVISION OF CONNECTICUT
  CORPORATION, CABLEVISION OF HUDSON
 COUNTY, INC., CABLEVISION OF LITCHFIELD,
   INC., CABLEVISION OF MONMOUTH, INC.,
      CABLEVISION OF NEW JERSEY, INC.,
       CABLEVISION OF OAKLAND LLC,
AND CABLEVISION OF ROCKLAND/RAMAPO LLC,
              Defendants-Appellees,
                            and
         TDS METROCOM LLC, TDS
   TELECOMMUNICATIONS CORPORATION,
AND UNITED STATES CELLULAR CORPORATION,
                Defendants.
              __________________________

    2009-1450, -1451, -1452, -1468, -1469, 2010-1017
             __________________________
3                     RONALD A KATZ TECH   v. AMERICAN AIR

   Appeals from the United States District Court for the
Central District of California in case nos. 2:07-ML-1816,
07-CV-2192, 07-CV-2196, 07-CV-2360, and 07-CV-2134,
Judge R. Gary Klausner.
              ___________________________

              Decided: February 18, 2011
              ___________________________

   FRANK V. PIETRANTONIO and JONATHAN G. GRAVES,
Cooley Goodward Kronish LLP, of Reston, Virginia,
argued for plaintiff-appellant. With them on the brief
were NATHAN K. CUMMINGS; STEPHEN C. NEAL and LORI
R.E. PLOEGER, of Palo Alto, California.

   MARK A. PERRY, Gibson, Dunn & Crutcher LLP, of
Washington, DC, argued for all defendants-appellees.
With him on the brief were JOSH A. KEVITT, of New York,
New York and David A. Segal, of Irvine, California; and
Adam T. Bernstein, CSC Holding, LLC, of Bethpage, New
York, for CSC Holding, et al.

   MIKE MCKOOL, JR., McKool Smith, P.C., of Dallas,
Texas, for defendant-appellee American Airlines, Inc.
With him on the brief were PETER J. AYERS and JOEL L.
THOLLANDER, of Austin, Texas.

    KARAN F. STOLL, Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP, of Washington, DC, for defen-
dants-appellees FedEx Corporation Services, Inc., et al.
With her on the brief were JASON W. MELVIN; and
JEFFREY A. BERKOWITZ and JAMES J. BOYLE, of Reston,
Virginia; and E. CHRIS CHERRY, FedEx Corporation, of
Memphis, Tennessee.
RONALD A KATZ TECH   v. AMERICAN AIR                        4

     CHRISTOPHER S. RUHLAND, Orrick, Herrington & Sut-
cliffe LLP, of Los Angeles, California, for defendant-
appellee DHL Express (USA), Inc. With him on the brief
were EDWIN V. WOODSOME, JR.; and MATTHEW H. POPPE,
of Menlo Park, California, and MARK J. SHEAN, of Irvine,
California.

    JONATHAN R. SPIVEY, Foley & Lardner LLP, of Chi-
cago, Illinois, for defendants-appellees U.S. Bancorp et al.
With him on the brief were GREGORY S. NORROD and
SCOTT R. KASPAR; and GEORGE E. QUILLIN, of Washington,
DC.
                 __________________________

  Before NEWMAN, LOURIE, and BRYSON, Circuit Judges.
BRYSON, Circuit Judge.
     In this multi-district litigation patent case, the plain-
tiff Ronald A. Katz Technology Licensing LP (“Katz”)
appeals from final judgments entered by the United
States District Court for the Central District of California
in a group of consolidated cases. The judgments held
numerous claims from Katz’s patent portfolio either
invalid or not infringed. We affirm in part, vacate in part,
and remand.
                              I
    Katz owns a number of patents on interactive call
processing systems and call conferencing systems. The 14
patents that Katz asserts in this appeal all relate to
interactive call processing systems. The patents fall into
four groups; the patents in each group share a common
specification.
    The first group of patents, referred to as the “Statisti-
cal Interface” group, covers a telephonic interface system
for acquiring data from a large group of callers and using
5                       RONALD A KATZ TECH   v. AMERICAN AIR

that data to identify some subset of the group. 1 See, e.g.,
’863 patent, col. 1, ll. 52-64. The claimed system can be
used in connection with a variety of telephone-based
operations, such as “an auction sale, a contest, a lottery, a
poll, a merchandising operation, a game, and so on.” ’863
patent, col. 2, ll. 18-19.
    The second group of patents, referred to as the “Con-
ditional Interface Plus” group, covers “a telephonic-
computer interface system” that can handle a large num-
ber of calls and direct them either to live-operator stations
or to computer-operated stations. 2 ’285 patent, col. 2, ll.
3-8. The claimed system is designed to avoid the “some-
times complex and burdensome” interfaces presented to
callers that can result in ineffective screening, misdirec-
tion of calls, and cumbersome delay. Id., col. 1, ll. 60-62.
    The third group of patents, referred to as the “Dual
Call Mode” group, covers a telephone call processing
system for receiving and processing calls relating to a
game or contest format, in which the system has means
for neutralizing the advantages in the game or contest



    1   That group of patents includes U.S. Patent No.
5,235,309 (“the ’309 patent”), U.S. Patent No. 5,561,707
(“the ’707 patent”), U.S. Patent No. 5,684,863 (“the ’863
patent”), U.S. Patent No. 5,815,551 (“the ’551 patent”),
U.S. Patent No. 5,898,762 (“the ’762 patent”), U.S. Patent
No. 6,035,021 (“the ’021 patent”), U.S. Patent No.
6,148,065 (“the ’065 patent”), U.S. Patent No. 6,292,547
(“the ’547 patent”), and U.S. Patent No. 6,678,360 (“the
’360 patent”). The ‘309, ‘762, and ‘021 patents are dis-
cussed in Katz’s brief, but no claims from those patents
have been selected against any of the appellees. Those
patents are therefore not at issue in this appeal. See infra
Part VIII.
    2   That group of patents includes U.S. Patent No.
5,351,285 (“the ’285 patent”) and U.S. Patent No.
5,917,893 (“the ’893 patent”).
RONALD A KATZ TECH   v. AMERICAN AIR                      6

that would otherwise be obtained by repeat callers. 3 ’120
patent, col. 2, ll. 62-66. The preferred embodiment de-
scribed in those patents uses different procedures for
qualifying the caller to participate in the game depending
on whether the caller has dialed an 800 number, a 900
number, or an area code number. Id., fig. 2.
    The last patent, U.S. Patent No. 6,335,965 (“the ’965
patent”), referred to as the “Voice-Data” patent, claims a
telephone-computer interface system that is designed to
receive and identify both digital signals and voice signals
from callers. ’965 patent, col. 2, ll. 20-23, 28-29
    In 1997, Katz asserted many of the same patents in
an action brought against AT&T Corporation in the
United States District Court for the Eastern District of
Pennsylvania. The parties settled that action. In 2001,
Verizon Communications Inc. filed a declaratory judg-
ment action against Katz in the United States District
Court for the Central District of California. The parties
settled that action after claim construction and summary
judgment rulings. Between 2005 and 2006, Katz filed 25
separate actions in federal district courts in the Eastern
District of Texas and the District of Delaware. The Judi-
cial Panel on Multidistrict Litigation transferred all the
cases to the Central District of California for coordinated
pretrial proceedings before Judge R. Gary Klausner, who
had presided over Verizon’s declaratory judgment suit.
Across all 25 actions, Katz asserted a total of 1,975 claims
from 31 patents against 165 defendants in 50 groups of
related corporate entities (“defendant groups”). Katz has
subsequently filed 28 additional actions that have also


    3  That group of patents includes U.S. Patent No.
5,974,120 (“the ’120 patent”) and U.S. Patent No.
6,434,223 (“the ’223 patent”).
7                      RONALD A KATZ TECH   v. AMERICAN AIR

been assigned to Judge Klausner. This appeal arises from
the initial 25 actions.
     Several groups of defendants asked the district court
to limit the number of asserted claims to be addressed in
the litigation. One group proposed that Katz initially
select 40 claims per action and then narrow the number of
selected claims to 20 per action after discovery. Katz
countered with a broader proposal to initially select 50
claims per defendant group and then narrow the number
of selected claims to 20 per defendant group after discov-
ery. Katz did not question the need to limit the number of
claims in order to make the case manageable.
    Choosing a middle ground between the two proposals,
the district court ordered Katz initially to select no more
than 40 claims per defendant group, and after discovery
to narrow the number of selected claims to 16 per defen-
dant group. The court further directed that the total
number of claims to be asserted against all defendants
could not exceed 64 (eight claims for each unique specifi-
cation including four specifications not at issue in this
appeal). However, the court added a proviso that the
limitations on the numbers of claims were not immutable.
The proviso permitted Katz to add new claims if they
“raise[d] issues of infringement/validity that [were] not
duplicative” of previously selected claims. Katz added
new claims to exceed a total of 64 across all the actions,
but the number of claims did not exceed 16 per defendant
group. 4

    4   Katz selected 16 claims to assert against appellees
U.S. Bancorp and U.S. Bank National Association (“U.S.
Bank”). From the Statistical Interface group, Katz se-
lected claims 43, 49, 96, 98, and 99 of the ’863 patent;
claims 21 and 33 of the ’551 patent; claims 13 and 86 of
the ’360 patent; and claim 13 of the ’065 patent. From the
Conditional Interface Plus group, Katz selected claims 19,
49, and 71 of the ’285 patent. From the Dual Call Mode
RONALD A KATZ TECH   v. AMERICAN AIR                      8


group, Katz chose claim 5 of the ’223 patent. And from
the Voice-Data patent, Katz selected claims 61 and 66.
    Katz selected 16 claims to assert against appellees
DHL Express (USA), Inc., and its associated parties
(“DHL”). From the Statistical Interface group, Katz
selected claims 19 and 33 of the ’551 patent; claims 14
and 36 of the ’360 patent; claim 98 of the ’863 patent; and
claim 13 of the ’065 patent. From the Conditional Inter-
face Plus group, Katz selected claim 61 of the ’285 patent
and claims 1 and 2 of the ’893 patent. From the Dual Call
Mode group, Katz chose claims 34, 57, and 63 of the ’120
patent. And from the Voice-Data patent, Katz selected
claims 31, 35, 61, and 66.
    Katz selected 11 claims to assert against appellee
American Airlines, Inc. From the Statistical Interface
group, Katz selected claims 43 and 98 of the ’863 patent;
claims 19 and 21 of the ’551 patent; claims 14 and 86 of
the ’360 patent; claim 85 of the ’707 patent; and claim 13
of the ’065 patent. From the Dual Call Mode group, Katz
chose claims 34 and 67 of the ’120 patent. And from the
Voice-Data patent, Katz selected claim 53.
    Katz selected 15 claims to assert against appellees
Cablevision Systems Corporation and its associated
parties. From the Statistical Interface group, Katz se-
lected claim 11 of the ’547 patent; claim 33 of the ’551
patent; claims 14 and 36 of the ’360 patent; claim 69 of
the ’707 patent; and claim 13 of the ’065 patent. From the
Conditional Interface Plus group, Katz selected claims 1
and 61 of the ’285 patent as well as claims 2 and 83 of the
’893 patent. From the Dual Call Mode group, Katz chose
claim 57 of the ’120 patent and claim 2 of U.S. Patent No.
6,512,415, which is not at issue on appeal. And from the
Voice-Data patent, Katz selected claims 31, 61, and 66.
    Katz selected 15 claims to assert against appellee
FedEx Corporation and its associated defendants. From
the Statistical Interface group, Katz selected claim 18 of
the ’547 patent; claim 19 of the ’551 patent; claims 18 and
86 of the ’360 patent; claim 85 of the ’707 patent; claim 43
of the ’863 patent; and claim 13 of the ’065 patent. From
the Conditional Interface Plus group, Katz selected claims
19 and 49 of the ’285 patent and claims 2 and 83 of the
’893 patent. From the Dual Call Mode group, Katz chose
9                      RONALD A KATZ TECH   v. AMERICAN AIR

    Instead of selecting additional claims and seeking to
show that those claims raised non-duplicative issues of
infringement or validity, Katz moved the court to sever
and stay the non-selected claims. Katz contended that
the court’s requirement that it select particular claims
violated its due process rights because the court’s order
could result in decisions having a preclusive effect on non-
selected claims regardless of whether those claims pre-
sented distinct issues of invalidity or infringement. The
court denied Katz’s motion. The court held that Katz’s
rights under the unselected claims were protected by the
proviso that Katz could add new claims if it could show
that the new claims raised non-duplicative issues of
validity or infringement.
     The defendants then jointly moved for summary
judgment on the issues of anticipation, obviousness,
written description, and indefiniteness. The defendants
also moved individually for summary judgment on case-
specific grounds. In response to those motions, the dis-
trict court held all the claims selected against the appel-
lees to be either invalid or not infringed by the appellees’
accused devices. The court then entered final judgments
in favor of the appellees. The related actions against
other defendants are still pending in the district court.
                             II
    Katz appeals the district court’s decision not to sever
and stay the unselected claims. Katz contends that by
entering final judgments in these cases without severing
and staying the unselected claims, the district court
divested Katz of its rights in the unselected claims with-
out due process. Katz argues that the court’s judgments
may have preclusive effects in any subsequent actions on


claims 34 and 67 of the ’120 patent. And from the Voice-
Data patent, Katz selected claims 31 and 53.
RONALD A KATZ TECH   v. AMERICAN AIR                     10

the unselected claims and that due process requires that
Katz be allowed to litigate the unselected claims either in
this case or in subsequent actions. 5 Katz also contends
the district court assumed its claims were duplicative, in
violation of the claim-differentiation doctrine and the
independent presumption of claim validity from 35 U.S.C.
§ 282.
                             A
    We reject Katz’s due process argument. Katz has not
shown that the claim selection procedure the district court
employed was inadequate to protect Katz’s rights with
respect to the unasserted claims. 6 To make out a due
process claim, Katz must demonstrate that the district
court’s claim selection procedure risked erroneously
depriving it of its rights and that the risk outweighed the
added costs associated with a substitute procedure. See
Mathews v. Eldridge, 424 U.S. 319, 335 (1976).
    Katz argues that it was improper for the district court
to impose any burden on it to make a showing that any of
the unselected claims raised issues of infringement or
invalidity that were not duplicative of the issues raised by
the selected claims. According to Katz, the court should
have required the appellees to bear the burden to show
that issues were duplicative; absent such a showing, Katz
contends, the unasserted claims should have been ex-
pressly excluded from the judgments entered in this case.

    5    Although we accept Katz’s assertion that the final
judgments could have preclusive effects in later actions
brought against the same or other parties, the precise
effect of the judgments in this case will necessarily have
to be decided in any such later actions that may be
brought.
    6    We assume without deciding that Katz has a
separate property right in each claim of each asserted
patent.
11                     RONALD A KATZ TECH   v. AMERICAN AIR

    Katz supports its argument by pointing to collateral
estoppel cases in which a second defendant has borne the
burden of demonstrating that the asserted claims lacked
patentably significant additions to claims previously
found to be invalid when asserted against a first defen-
dant. See Bourns, Inc. v. United States, 537 F.2d 486, 493
n.6 (Ct. Cl. 1976); Medinol Ltd. v. Guidant Corp., 341 F.
Supp. 2d 301, 314 (S.D.N.Y. 2004). Because other defen-
dants in future suits would bear the burden of showing
that any newly asserted claims were barred by the district
court’s judgment as a matter of issue preclusion, Katz
argues by analogy that the appellees should have been
required to show that the issues presented by the claims
that Katz did not select in this case were identical to the
issues presented by the selected claims. Burden alloca-
tion, however, is a tool “intended progressively to sharpen
the inquiry into the elusive factual question[s]” in a case.
See Tex. Dep’t of Cmty. Affairs v. Burdine, 450 U.S. 248,
255 n.8 (1981). When the claimant is in the best position
to narrow the dispute, allocating the production burden to
the claimant will benefit the decision-making process and
therefore will not offend due process unless the burden
allocation unfairly prejudices the claimant’s opportunity
to present its claim.
    Katz has failed to demonstrate that the allocation of
burdens in the claim selection procedure adopted by the
district court unfairly prejudiced it by creating a signifi-
cant risk that Katz would be erroneously deprived of
property rights in unselected claims. The district court
noted that by providing examples of duplicative claims
and pointing out the common genealogy of Katz’s patents
and the terminal disclaimers in almost all of them, the
defendants had made “a convincing showing that many of
RONALD A KATZ TECH   v. AMERICAN AIR                    12

the claims are duplicative.” 7 Because neither side had
provided an analysis of all of the claims, the court recog-
nized the possibility that the limitations on the number of
claims to be asserted might be unduly restrictive. The
court therefore provided that more claims could be added
if Katz could show that the additional claims presented
unique issues. Under the circumstances of this case, we
conclude that the district court acted reasonably in con-
cluding that it would be more efficient to require Katz to
point out those unselected claims that raised separate
issues of infringement and invalidity rather than requir-
ing the defendants to prove that all of the unselected
claims were duplicative.
    Katz made no effort to identify any such claims. In-
stead, it complained that the number of claims the court
allowed was insufficient, and it moved to add new claims
exceeding the 64-claim limit across all actions. The
district court noted that Katz did not “attempt to prove
that the specific newly asserted claims raise[d] new
infringement/validity issues.”    Instead, the court ob-
served, Katz merely asserted “the generalized notion that
64 was too few [claims] for the number of accused services
at issue.” Because Katz did not file a motion to add
claims with the requisite showing of need, the court
concluded that Katz “cannot legitimately complain that it
did not have a meaningful opportunity to be heard on
those claims.” Even absent a showing of uniqueness, the
court allowed Katz to add new claims that were closely
   7    Although Katz objects that the court examined
only a small number of claims before making that finding,
the court also based its finding on the common genealogy
of Katz’s patents. Because Katz has thousands of claims
stemming from only eight unique specifications with a
common genealogy, we cannot conclude that district court
erred in finding that many of Katz’s claims are duplica-
tive based on the evidence before it and Katz’s refusal to
make a counter-showing.
13                      RONALD A KATZ TECH   v. AMERICAN AIR

related to claims it had already selected. 8 In the end,
Katz selected a total of almost 100 claims to be addressed
in the consolidated cases. Nonetheless, Katz moved to
sever and stay all of the unselected claims. The district
court rejected that motion, explaining:
     The motion fails to identify any claims that are
     substantially different from the claims it is cur-
     rently asserting. It does not identify any services
     or products that it could accuse of infringing non-
     selected claims, let alone, show that these services
     do not present the same issues for selected claims.
     Plaintiff’s motion merely states that an order lim-
     iting it to 16 claims per defendant group violates
     due process. However, due process is not merely a
     theoretical concern, the plaintiff must be able to
     show that it has lost some tangible right.
     We agree with the district court’s due process analy-
sis. Based on its initial determination that the asserted
patents contained many duplicative claims, it was both
efficient and fair to require Katz to identify those unas-
serted claims that, in Katz’s view, raised separate legal
issues from those raised by the asserted claims. In light
of Katz’s failure to make, or even attempt to make, any
such showing, it was reasonable for the district court to


     8  Per defendant group, the court gave Katz the
unlimited right to substitute any claim for a previously
selected claim that was dependent on the newly selected
claim. In addition, the court permitted Katz to make as
many as three substitutions of claims per defendant
group, choosing those claims from among the previously
selected 40 claims, from any claims from which the previ-
ously selected 40 claims depended, or from any claims
that depended from the previously selected 40 claims.
Finally, the court permitted Katz one substitution of any
claim with any claim already identified in Katz’s motion
to add new claims.
RONALD A KATZ TECH   v. AMERICAN AIR                     14

deny Katz’s motion to sever and stay the disposition of all
of the unselected claims.
     In approving the district court’s procedure, we do not
suggest that a district court’s claim selection decisions in
a complex case such as this one are unreviewable. Katz
could have sought to demonstrate that some of its unse-
lected claims presented unique issues as to liability or
damages. If, notwithstanding such a showing, the district
court had refused to permit Katz to add those specified
claims, that decision would be subject to review and
reversal. 9 As noted, however, the problem with Katz’s
position is that Katz made no effort to make such a show-
ing with respect to any of the unselected claims. Instead,
Katz chose to make the “all or nothing” argument that the
entire claim selection process was flawed from the start
and that it is impermissible to give the judgments effect
as to the unselected claims regardless of Katz’s failure to
make any showing as to the uniqueness of any of those
claims. That sort of global claim of impropriety is unper-
suasive. In complex cases, and particularly in multidis-
trict litigation cases, the district court “needs to have
broad discretion to administer the proceeding.” In re
Phenylpropanolamine (PPA) Prods. Liab. Litig., 460 F.3d
1217, 1232 (9th Cir. 2006). Given the district court’s need
to manage the cases before it and the “strong public
interest in the finality of judgments in patent litigation,”
Cardinal Chem. Co. v. Morton Int’l, Inc. 508 U.S. 83, 100
(1993), we cannot adopt Katz’s broad proposition. And,
not having made a record reflecting that the court erred

   9     It is also conceivable that a claim selection order
could come too early in the discovery process, denying the
plaintiff the opportunity to determine whether particular
claims might raise separate issues of infringement or
invalidity in light of the defendants’ accused products and
proposed defenses. Katz makes no such argument in this
appeal.
15                      RONALD A KATZ TECH   v. AMERICAN AIR

in its disposition of particular claims, Katz cannot point to
specific errors by the court in the administration of the
claim selection scheme that the court adopted.
                             B
     Turning to Katz’s other arguments, we hold that the
court did not violate the statutory presumption that each
claim is independently presumed valid, see 35 U.S.C.
§ 282, or the “rebuttable presumption that different
claims are of different scope,” Amgen Inc. v. Hoechst
Marion Roussel, Inc., 314 F.3d 1313, 1326 (Fed. Cir.
2003). While different claims are presumed to be of
different scope, that does not mean that they necessarily
present different questions of validity or infringement.
And the court only required Katz to demonstrate that new
claims presented unique questions of validity or infringe-
ment. The court explained that with respect to infringe-
ment, Katz “should be prepared to show that a non-
infringement defense raised by a specific defendant group
to a currently asserted claim does not apply in substan-
tially the same manner to a newly asserted claim.” With
respect to validity, the court ordered that Katz “should be
prepared to show that the defendants have raised serious
issues of validity on a currently asserted claim, but that
the same defense does not affect the newly asserted claim
in substantially the same way.” Although the court
required Katz to show that additional claims presented
unique questions for the case, the court did not place a
burden on Katz to demonstrate that its claims covered
distinct subject matter.
                             III
    The district court granted summary judgment of in-
definiteness as to a number of the asserted claims under
two different theories. With respect to certain claims that
were drafted in the means-plus-function format pre-
RONALD A KATZ TECH   v. AMERICAN AIR                      16

scribed by 35 U.S.C. § 112 ¶ 6, the court concluded that
the claims were invalid for indefiniteness because the
only corresponding structure disclosed in the specification
was a general purpose computer and the specification did
not disclose an algorithm by which the general purpose
computer performed the recited function. We affirm that
ruling in part, vacate it in part, and remand for further
proceedings. The district court also invalidated several
claims as indefinite for claiming both an apparatus and a
method of using that apparatus. We affirm that ruling.
                             A
    Katz appeals the district court’s ruling that claims di-
rected to a “means for processing” were indefinite because
the claims failed to satisfy the requirements of section
112, paragraph 6. In particular, the court held that the
claims failed to disclose structure corresponding to the
recited function in the form of a computer algorithm. On
that ground, the court invalidated a number of claims
from the Statistical Interface and Conditional Interface
Plus groups. The invalidated claims are claims 96, 98,
and 99 of the ’863 patent, which recite a “means for
processing at least certain of said answer data signals”;
claims 11 and 18 of the ’547 patent, which recite an
“analysis structure for receiving and processing said caller
data signals”; claim 19 of the ’551 patent, which recites an
“analysis structure connected to the record memory for
processing at least certain of the data relating to certain
individual callers subject to qualification by the qualifica-
tion structure”; claims 21 and 33 of the ’551 patent and
claim 13 of the ’065 patent, which recite a “processing
means . . . for receiving customer number data entered by
a caller and for storing the customer number data . . . and
based on a condition coupling an incoming call to the
operator terminal, the processing means visually display-
ing the customer number data”; and claim 61 of the ’285
17                     RONALD A KATZ TECH   v. AMERICAN AIR

patent, which recites a “means for processing coupled to
said forwarding means for processing caller information
data entered by an operator.” The court invalidated those
claims pursuant to the analysis set forth in WMS Gam-
ing, Inc. v. International Game Technology, 184 F.3d 1339
(Fed. Cir. 1999), and Aristocrat Technologies Australia Pty
Ltd v. International Game Technology, 521 F.3d 1328
(Fed. Cir. 2008), because the specifications of each of the
patents at issue disclosed only general purpose processors
and did not disclose the algorithms that those processors
used to perform the recited functions.
    In WMS Gaming, this court addressed a means-plus-
function limitation in which the recited function was
implemented by a general purpose computer. The patent
claimed slot machines having a “means for assigning a
plurality of numbers representing” the angular positions
of each slot reel. 184 F.3d at 1346. The parties agreed
that a computer controlled the means-plus-function
limitation, and the district court construed the limitation
to cover “any table, formula, or algorithm” that might be
used to perform the function of assigning numbers repre-
senting the angular positions of the reel. This court
rejected that interpretation and construed the limitation
to cover only the algorithm disclosed in the specification.
The court did so because it construed the corresponding
structure not to be a general purpose computer, but
rather to be a special purpose computer programmed to
perform the disclosed algorithm. Id. at 1348-49, citing In
re Alappat, 33 F.3d 1526, 1545 (Fed. Cir. 1994) (en banc).
    The subsequent case of Harris Corp. v. Ericsson Inc.,
417 F.3d 1241 (Fed. Cir. 2005), involved a signal process-
ing patent claiming a “time domain processing means” for
simulating the dispersive effect of media through which
signals travel. Id. at 1245-46. The district court in that
case held that the structure corresponding to that func-
tion was a “symbol processor.” Id. at 1249. This court
RONALD A KATZ TECH   v. AMERICAN AIR                      18

reversed. The court noted that a “computer-implemented
means-plus-function term is limited to the corresponding
structure disclosed in the specification and equivalents
thereof, and the corresponding structure is the algo-
rithm.” Id. at 1253. The court then held that the struc-
ture corresponding to the “time domain processing means”
could not be merely a “symbol processor,” because the
“symbol processor” did not incorporate any disclosed
algorithm. Id. at 1254.
     In the Aristocrat case, decided several years later, the
court applied WMS Gaming and Harris to a patent that
failed to disclose the algorithm that the recited computer
used to perform a computer-implemented function. The
patent at issue in Aristocrat covered a slot machine with a
“control means” to control displayed images, to define a
set of predetermined arrangements for a given game
depending on the player’s selections, and to pay a prize
when a predetermined arrangement of symbols was
displayed. Aristocrat, 512 F.3d at 1330-31. The only
disclosed structure was a standard microprocessor-based
gaming machine with “appropriate programming.” Id.
This court affirmed the district court’s ruling that the
claims were indefinite due to the lack of structure corre-
sponding to the recited functions. The court noted that
the algorithm by which the functions are performed must
be disclosed so as “to avoid pure functional claiming.” Id.
at 1333.
                              1
    Several of Katz’s claims are clearly indefinite under
the principles of WMS Gaming, Aristocrat, and Harris.
Claims 21 and 33 of the ’551 patent and claim 13 of the
’065 patent contain a means-plus-function limitation that
recites a “processing means . . . for receiving customer
number data entered by a caller and for storing the cus-
tomer number data . . . and based on a condition coupling
19                     RONALD A KATZ TECH   v. AMERICAN AIR

an incoming call to the operator terminal, the processing
means visually displaying the customer number data.”
The ’551 and ’065 patents, however, do not disclose an
algorithm that corresponds to the “based on a condition
coupling an incoming call to the operator terminal” func-
tion.
     Computers can be programmed to conditionally couple
calls in many ways. Without any disclosure as to the way
Katz’s invention conditionally couples calls, the public is
left to guess whether the claims cover only coupling based
on particular system conditions, such as the availability of
an operator, or are broad enough to cover any coupling in
conjunction with an if-then statement in source code.
Katz’s claims therefore fail to fulfill the “public notice
function” of 35 U.S.C. § 112 ¶ 2 by “particularly pointing
out and distinctly claiming” the invention. See Praxair,
Inc. v. ATMI, Inc., 543 F.3d 1306, 1319 (Fed. Cir. 2008).
And by claiming a processor programmed to perform a
specialized function without disclosing the internal struc-
ture of that processor in the form of an algorithm, Katz’s
claims exhibit the “overbreadth inherent in open-ended
functional claims,” Halliburton Energy Servs. v. M-I LLC,
514 F.3d 1244, 1256 n.7 (Fed. Cir. 2008), in violation of
the limits Congress placed on means-plus-function claims
in section 112, paragraph 6. 10 Because of the absence of
the requisite structure, we affirm the district court’s
indefiniteness ruling as to claims 21 and 33 of the ’551
patent and claim 13 of the ’065 patent.
     10 In an effort to point to structure corresponding to
the function recited in those claims, Katz points to com-
munication lines connecting the processor to an “interface
terminal.” Those lines constitute the structure by which
the processor sends calls to the operator terminal, but
merely referring to those communication lines does not
describe the algorithm by which a processor tests a condi-
tion and couples an incoming call to a terminal depending
on the outcome of that test.
RONALD A KATZ TECH   v. AMERICAN AIR                       20

                              2
    We reach a different conclusion with respect to the
district court’s analysis of claims 96, 98, and 99 of the ’863
patent, claims 11 and 18 of the ’547 patent, claim 19 of
the ’551 patent, and claim 61 of the ’285 patent. As to
those claims, we conclude that the district court inter-
preted the principles of WMS Gaming, Aristocrat, and
Harris too broadly, so we vacate the court’s indefiniteness
ruling and remand to the district court for claim construc-
tion and application of the correct rule.
    The court interpreted those cases to require that “the
specification . . . disclose an algorithm for [any] recited
function” that is performed solely or predominantly by a
general purpose computer. The appellees characterize
that rule as applying to any function that is “linked” to a
general purpose computer. But that interpretation of our
prior cases is too broad. Those cases involved specific
functions that would need to be implemented by pro-
gramming a general purpose computer to convert it into a
special purpose computer capable of performing those
specified functions. See, e.g., Aristocrat, 521 F.3d at 1333-
34; Harris, 417 F.3d at 1253; WMS Gaming, 184 F.3d at
1349. By contrast, in the seven claims identified above,
Katz has not claimed a specific function performed by a
special purpose computer, but has simply recited the
claimed functions of “processing,” “receiving,” and “stor-
ing.” Absent a possible narrower construction of the
terms “processing,” “receiving,” and “storing,” discussed
below, those functions can be achieved by any general
purpose computer without special programming. 11 As

    11  In substance, claiming “means for processing,”
“receiving,” and “storing” may simply claim a general
purpose computer, although in means-plus-function
terms. While broadly claiming in that manner makes it
easier to satisfy the statutory requirement of “particularly
21                     RONALD A KATZ TECH   v. AMERICAN AIR

such, it was not necessary to disclose more structure than
the general purpose processor that performs those func-
tions. Those seven claims do not run afoul of the rule
against purely functional claiming, because the functions
of “processing,” “receiving,” and “storing” are coextensive
with the structure disclosed, i.e., a general purpose proc-
essor.
    The appellees contend that the district court’s broad
rule of indefiniteness is supported by language from Net
MoneyIN, Inc. v. VeriSign, Inc., 545 F.3d 1359 (Fed. Cir.
2008). In that case, this court stated that “a means-plus-
function claim element for which the only disclosed struc-
ture is a general purpose computer is invalid if the speci-
fication fails to disclose an algorithm for performing the
claimed function.” Id. at 1367, citing WMS Gaming, 184
F.3d at 1337-38. When viewed in context, it is clear that
the quoted language applied only to computer-
implemented means-plus-function claims in which the
computer would be specially programmed to perform the
recited function. As authority, the court cited WMS
Gaming, which was limited to a computer implementing a
specific function. And the claim at issue in Net MoneyIN
recited a particular function not disclosed simply by a
reference to a general purpose computer. That claim
involved a credit card authorization system with a “means
for generating an authorization indicia in response to
queries containing a customer account number and
amount.” Net MoneyIN, 545 F.3d at 1365. The only
recited structure for performing that function was a “bank
computer.” The patentee contended that the recited
structure was sufficient because a person of ordinary skill
in the art would understand that a bank computer com-

pointing out and distinctly claiming the subject matter” of
the claims, 35 U.S.C. § 112 ¶ 2, it increases the vulner-
ability of the claims to possible invalidity on other
grounds.
RONALD A KATZ TECH   v. AMERICAN AIR                         22

pares account data and transaction amount data to de-
termine if credit is available. This court rejected that
argument on the ground that the specification did not
disclose an algorithm to perform the specified function,
even though a person of ordinary skill in the art might
have been able to devise one. Net MoneyIN, therefore,
does not support a broader principle of indefiniteness
than was applied in this court’s previous cases.
    At oral argument, the parties disagreed about what
the claims meant by “processing.” Katz contended that
“processing” meant nothing more specific than “process-
ing.” The appellees contended that “processing” was
limited to the specific functions disclosed in the specifica-
tions. The district court’s construction of “means for
processing” in related patents as “processing calls in an
interface format” does not resolve that dispute. Because
the parties have not briefed the construction of the term
“processing” as used in the seven claims referred to above,
we leave it to the district court to construe that term,
along with the terms “receiving” and “storing.” Based on
its construction, the district court can then determine
whether the functions recited in those seven contested
claims can be performed by a general purpose processor
or, instead, constitute specific computer-implemented
functions as to which corresponding algorithms must be
disclosed.
                               3
    As an alternative argument for vacating the court’s
indefiniteness ruling, Katz contends that the correspond-
ing structure for the means-plus-function terms is not
limited to the general purpose microprocessor 92, but also
includes the interface 20, disclosed in the common specifi-
cation of the Statistical Interface patents. Katz is correct
that the interface 20 may perform analysis on data, see
’863 patent, col. 4, ll. 52-53, but that is beside the point. If
23                     RONALD A KATZ TECH   v. AMERICAN AIR

a function’s corresponding structure is a type of computer
or processor, indefiniteness analysis does not turn on the
name of the structure that does the processing. See, e.g.,
Net MoneyIN, 545 F.3d at 1366-67 (rejecting the argu-
ment that persons of skill in the art would understand
how a “bank computer” would be programmed); Harris,
417 F.3d at 1254 (rejecting the construction of “symbol
processor” as corresponding structure because it did not
incorporate the disclosed algorithm). The key inquiry is
whether one of ordinary skill in the art would understand
the patent to disclose structure that sufficiently corre-
sponds to the claimed function, which in the case of a
specific function implemented on a general purpose com-
puter requires an algorithm. See Aristocrat, 521 F.3d at
1337, citing Med. Instrumentation & Diagnostics Corp. v.
Elekta AB, 344 F.3d 1205, 1212 (Fed. Cir. 2003). As to
claims 21 and 33 of the ’551 patent and claim 13 of the
’065 patent, which recite the “based on a condition cou-
pling an incoming call to the operator terminal” limita-
tion, Katz has not provided sufficient evidence that a
person of ordinary skill would understand that interface
20 discloses a particular algorithm for conditionally
coupling calls. 12 The patent discloses that interface 20
has “switching mechanisms,” but that is an insufficient

     12 Because the display terminals are the correspond-
ing structure for the function of “visually displaying the
customer number data,” one of the recited functions in the
“processing means” limitation of these claims, Katz ar-
gues that the specification need not set forth an algorithm
for performing the other functions recited in the limita-
tion. Katz contends that by disclosing the display termi-
nals the Statistical Interface specification has disclosed
“more than” a general purpose computer and thereby has
avoided “pure functional claiming.” Aristocrat, 521 F.3d
at 1333. Although the display terminals are special
purpose machines, Katz has provided no evidence that
they include structure capable of conditionally coupling
calls.
RONALD A KATZ TECH   v. AMERICAN AIR                       24

description of an algorithm for conditionally coupling
calls. As to the other claims, it may be necessary for the
district court to address whether a person of ordinary skill
in the art would understand interface 20 to sufficiently
disclose structure that performs pertinent functions,
depending on the outcome of the court’s construction of
the “processing,” “receiving,” and “storing” functions
recited in those claims.
                              B
    The district court held that Statistical Interface
claims 1, 2, and 83 of the ’893 patent are indefinite under
IPXL Holdings, L.L.C. v. Amazon.com, Inc., 430 F.3d
1377, 1384 (Fed. Cir. 2005), because they claim both an
apparatus and a method of use. In IPXL, this court
addressed a claim that covered a system with “an input
means” and required a user to use the input means. This
court held that the claim was indefinite because it was
unclear “whether infringement . . . occurs when one
creates a system that allows the user [to use the input
means], or whether infringement occurs when the user
actually uses the input means.” Id.
    Claims 1, 2, and 83 of the ’893 patent cover a system
with an “interface means for providing automated voice
messages . . . to certain of said individual callers, wherein
said certain of said individual callers digitally enter data.”
The district court found “no meaningful distinction”
between those claims and the claim at issue in IPXL.
    Katz seeks to distinguish IPXL on the ground that the
term “wherein” does not signify a method step but instead
defines a functional capability. We disagree and uphold
the district court’s ruling. Like the language used in the
claim at issue in IPXL (“wherein . . . the user uses”), the
language used in Katz’s claims (“wherein . . . callers
digitally enter data” and “wherein . . . callers provide . . .
data”) is directed to user actions, not system capabilities.
25                     RONALD A KATZ TECH   v. AMERICAN AIR

    In the alternative, Katz contends that this court nar-
rowed IPXL in the subsequent decision in Microprocessor
Enhancement Corp. v. Texas Instruments Inc., 520 F.3d
1367, 1374-75 (Fed. Cir. 2008). That case dealt with a
method claim that recited structural elements. The claim
took the form of a “method of executing instructions in a
pipelined processor comprising: [structural limitations of
the pipelined processor]; the method further comprising:
[method steps implemented in the pipelined processor].”
Id. at 1374. The court in Microprocessor distinguished
IPXL because the method claim in Microprocessor did not
create any confusion as to when the claim was directly
infringed; direct infringement occurred upon practicing
the claimed method in a processor with the required
structural limitations. Simply making or selling a proces-
sor having that structure would not have infringed.
Katz’s claims, however, create confusion as to when direct
infringement occurs because they are directed both to
systems and to actions performed by “individual callers.”
Katz’s claims therefore fall squarely within the rationale
of IPXL and are indefinite.
                            IV
    The district court invalidated several claims from the
Statistical Interface patents and the Dual Call Mode
patents for failing to satisfy the written description re-
quirement of 35 U.S.C. § 112 ¶ 1.
    Written description is a factual inquiry.         Ariad
Pharm., Inc. v. Eli Lilly & Co., 598 F.3d 1336, 1351 (Fed.
Cir. 2010) (en banc). “[T]he test requires an objective
inquiry into the four corners of the specification from the
perspective of a person of ordinary skill in the art. Based
on that inquiry, the specification must describe an inven-
tion understandable to that skilled artisan and show that
the inventor actually invented the invention claimed.” Id.
The purpose of the written description requirement “is to
RONALD A KATZ TECH   v. AMERICAN AIR                      26

ensure that the scope of the right to exclude, as set forth
in the claims, does not overreach the scope of the inven-
tor's contribution to the field of art as described in the
patent specification." Reiffin v. Microsoft Corp., 214 F.3d
1342, 1345 (Fed. Cir. 2000).
                             A
    From the Statistical Interface group of patents, the
district court invalidated method claims 13, 14, 36, and 86
of the ’360 patent for claiming the step of “visually dis-
playing customer number data” without describing that
step in the specification. 13 Those claims also require the
step of “receiving customer number data entered by a
caller.” Thus, the district court concluded that the specifi-
cation had to describe the visual display of customer
number data entered by a caller. The district court read
the specification as lacking such a description and held
the claims invalid for that reason.
     Katz contends that the district court erred by consid-
ering the second step, “receiving customer number data
entered by a caller,” when the defendants identified the
first step as the only disputed limitation. Katz claims
that by doing so, the court deprived it of the opportunity
to advance claim construction arguments, demonstrate
specification support, or proffer expert testimony. We
disagree. That the defendants did not challenge certain
limitations does not make those limitations irrelevant for
understanding the scope of the claims. See ACTV, Inc. v.
Walt Disney Co., 346 F.3d 1082, 1088 (Fed. Cir. 2003)
(“[T]he context of the surrounding words of the claim also

    13  The district court also held claim 13 of the ’065
patent and claims 21 and 33 of the ’551 patent invalid for
a lack of written description. Those patents are similar to
the ’360 patent, but we have affirmed the district court’s
indefiniteness ruling for those claims, so we do not discuss
them further here.
27                      RONALD A KATZ TECH   v. AMERICAN AIR

must be considered in determining the ordinary and
customary meaning of those terms.”). The district court
did not hold that the specification fails to describe the
step of “receiving customer number data entered by a
caller.” Instead, the court held that the specification fails
to describe the step of “visually displaying customer
number data” because the only descriptions of visual
display in the specification involve information that was
not entered by customers. In doing so, the district court
construed the claims, but that was entirely permissible,
as claim construction is inherent in any written descrip-
tion analysis.
     We reject Katz’s contention that the district court’s
claim constructions denied it the opportunity to demon-
strate specification support or proffer expert testimony. It
should have been clear to Katz that the construction of
the claims was important to the written description
analysis. Moreover, the defendants specifically identified
very similar language from claim 75 of the same patent
(the ’360 patent) as failing to satisfy the written descrip-
tion requirement. The similarity of that language, “iden-
tification data entered by the callers,” put Katz on notice
of the deficiency in the specification, i.e., the lack of
disclosure of the visual display of data entered by callers.
Thus, Katz had ample incentive and opportunity to dem-
onstrate specification support and offer expert testimony
on that issue.
     Despite that opportunity, Katz has not shown specifi-
cation support for the visual display of caller-entered
customer number data. Katz points to three statements
in the specification as providing that support, but each
fails to show that the inventor was in possession of the
claimed invention as of the filing date. First, Katz con-
tends that the discussion of the interface terminal dis-
closes the display of customer-entered data.         That
discussion, however, references only the display of opera-
RONALD A KATZ TECH   v. AMERICAN AIR                     28

tor-entered data. See ’360 patent, col. 11, ll. 11-16. Next,
Katz points to the command terminal in an auction em-
bodiment, which displays the “number of bidders” and
“fresh bidders.” Id., col. 15, ll. 23-32. Even if Katz’s
expert were correct that the fresh bidders are identified
by customer numbers, the specification would still not
provide the required support, because it contains no
indication that those customer numbers were entered by
the customer. Finally, Katz points to a broad statement
that “[i]n any of the various formats, the status of the
analysis can be televised by selecting a camera focused on
the interface terminal IT.” Id., col. 19, ll. 51-53. The
district court called that sentence the “Bootstrapping
Sentence” because Katz contended that it disclosed the
display of everything “[i]n any of the various formats.”
The previous descriptions of the interface terminal, how-
ever, were limited to operator-entered data. And Katz’s
expert did not state that the sentence in question dis-
closed the display of caller-entered data. Because Katz
failed to point to a genuine factual dispute over whether
the specification disclosed the display of caller-entered
customer numbers, the district court properly entered
summary judgment on that issue.
                             B
    From the Dual Call Mode group, the district court in-
validated claim 34 of the ’120 patent for claiming a sys-
tem in which “called number identification signals (DNIS)
. . . identif[y] said operating process format” without
describing such a system in the specification. Katz con-
tends that the specification describes such a system by
disclosing that DNIS signals correspond to different “call
modes,” such as 800 number or 900 number, and that
different call modes are used to identify different “call
processing flows.” The appellees contend that different
call processing flows are not different “formats,” as that
29                      RONALD A KATZ TECH   v. AMERICAN AIR

term was construed by the district court.         The court
construed the term “format” as follows:
     Format refers to a call processing flow imple-
     mented by at least one computer program that
     sets forth the content and sequence of steps to
     gather information from and convey information
     to callers through pre-recorded prompts and mes-
     sages. Selection of, or branching to, a module or
     subroutine within a computer program does not
     constitute selection of a separate format. Selec-
     tion of (or branching to), a second computer pro-
     gram by a first computer program, that together
     implement a call process flow application also
     does not constitute selection of a separate format.
We agree with Katz that the different call modes disclosed
by the specification identify different formats. For exam-
ple, the specification describes asking different questions
to and gathering different information from callers who
dial an 800 number, as opposed to those who dial a 900
number. Compare ’120 patent, col. 7, ll. 1-8, with id., col.
7, ll. 27-39. The different questions, however, are rele-
vant only to qualifying the 800 caller for participation in
the game or contest. Katz did not point to anything in the
specification that describes presenting 800 callers with a
different version of the game or contest. It is unclear
whether the claim requires such a description, because
the district court has not construed “operating process
format,” which may have a narrower definition than
“format.” See id. col. 3, ll. 10-11, 39-43. The parties have
not briefed us on this construction, and we decline to
construe it sua sponte. We therefore vacate the district
court’s judgment of invalidity as to claim 34 of the ’120
patent and remand for construction of the term “operating
process format.”
RONALD A KATZ TECH   v. AMERICAN AIR                    30

                             V
    Katz next appeals the district court’s rulings on obvi-
ousness. The court held that several of the Voice-Data
claims from the ’965 patent would have been obvious in
view of a prior art patent to Szlam and a prior art refer-
ence known as “Yoshizawa.” The court also invalidated
several of the Dual Call Mode claims from the ’120 patent
in view of two prior art references known as “Student
Registration” and “Moosemiller.”      Finally, the court
invalidated one other claim from the ‘120 patent in view
of Szlam and Student Registration. We affirm all of those
rulings.
                             A
    In appealing the obviousness ruling as to claims 31,
35, 53, 61, and 66 of the ’965 patent, Katz admits that
Szlam and Yoshizawa disclose all the elements of the
claims. Katz argues, however, that the trial court erred
in concluding that it would have been obvious to combine
those references.
    Szlam describes a customer-service system using a
voice response unit (“VRU”) to receive ordering informa-
tion from callers and to transfer callers to agents. Katz
agrees that Szlam discloses all of the claim limitations
except the limitation in claims 31, 35, and 53 that re-
quires acknowledgement numbers to be provided to
individual callers and the limitation in claims 61 and 66
that requires the system to confirm stored information
with a caller. Katz does not dispute that those limitations
are disclosed in Yoshizawa, which describes a telephone
betting system using a VRU that allows a caller to place
bets and that gives the caller a registration number that
can be used to cancel the bet. Yoshizawa reads back
stored information to the caller before the caller can
cancel a bet. Katz argues that it would not have been
31                     RONALD A KATZ TECH   v. AMERICAN AIR

obvious to combine the two references because the regis-
tration numbers in Yoshizawa are used to cancel a bet
under “tight time constraints,” which are not present in a
customer-service system such as Szlam. We disagree.
Yoshizawa explicitly states that its invention can be
applied to “order entry” systems, which are not described
as operating under “tight time constraints.” Moreover,
the use of a registration number to cancel an order works
in the same way as canceling a bet, even in the absence of
time pressures.
    We also disagree with Katz’s contention that a person
of ordinary skill in the art would not be motivated to
combine Yoshizawa with Szlam because Yoshizawa
distinguishes operator-assisted systems such as Szlam. A
reference can distinguish prior art in order to show the
novelty of an invention without teaching away from
combining the prior art with the invention disclosed in the
reference. See Ricoh Co., Ltd. v. Quanta Computer Inc.,
550 F.3d 1325, 1332 (Fed. Cir. 2008) (“A reference may be
said to teach away when a person of ordinary skill, upon
reading the reference, would be discouraged from follow-
ing the path set out in the reference, or would be led in a
direction divergent from the path that was taken by the
applicant.”) (internal quotation omitted).
    Katz also contends that the prior art references teach
away from claim 31, which requires both caller-entered
customer numbers and ANI (“Automatic Number Identifi-
cation,” i.e., signals indicating the caller’s number in a
manner similar to caller identification) to obtain account
information. According to Katz, Szlam teaches away from
using both techniques because it discloses only the use of
ANI or caller-entered customer numbers. Katz contends
that Yoshizawa teaches away from using ANI because its
system allows users to place bets “on a street corner,”
whereas ANI could not effectively operate in that setting
because people could bypass the system by calling from
RONALD A KATZ TECH   v. AMERICAN AIR                     32

different telephones. While those are distinctions be-
tween the prior art and the invention, they do not lead to
the conclusion that the prior art teaches away from the
invention. Neither of the references would lead an inven-
tor down an errant path or discourage using the combina-
tion of ANI and caller-entered numbers to obtain account
information. We agree with the district court that there
is no dispute of material fact as to whether the identified
claims of the ’965 patent would have been obvious in view
of Szlam and Yoshizawa.
    Katz next appeals the district court’s decision that
claims 35, 53, 61, and 66 of the ’965 patent were not
entitled to priority over Szlam. Once an accused infringer
establishes obviousness by clear and convincing evidence,
the burden shifts to the patentee to prove priority over the
invalidating prior art. See PowerOasis, Inc. v. T-Mobile
USA, Inc., 522 F.3d 1299, 1305 (Fed. Cir. 2008). To be
entitled to the priority date of an earlier application, the
patentee must show that “the application necessarily
discloses that particular device.” Hyatt v. Boone, 146 F.3d
1348, 1354 (Fed. Cir. 1998) (internal quotation omitted).
Therefore, in order for the claims to have priority over
Szlam, the parent application needed to disclose the
invention of those claims: receiving caller-entered signals,
looking up data corresponding to that caller in a file, and
displaying the located data. To support its argument that
the earlier application provided such disclosure, Katz
points to the same portions of the Statistical Interface
specification that it did in appealing the written descrip-
tion rulings—the interface terminal, the command termi-
nal, and the “Bootstrapping Sentence.”          Katz fails,
however, to explain how those specification statements
disclose the display of data corresponding to caller-
entered signals. Because Katz has not met its burden to
establish priority over Szlam, we affirm the district
33                       RONALD A KATZ TECH   v. AMERICAN AIR

court’s ruling that claims 35, 53, 61, and 66 of the ’965
patent are invalid for obviousness.
                              B
    The district court held that claims 57 and 63 of the
‘120 patent would have been obvious in view of the Stu-
dent Registration and Moosemiller references, and that
claim 67 of the ’120 patent would have been obvious in
view of the Szlam and Student Registration references.
Moosemiller discloses a voice response system that uses a
host computer to provide callers with voice prompts
allowing callers to log in to the system with touchtone
signals. The Moosemiller system can identify the number
that the caller has dialed and use that information to
classify incoming calls and greet each caller with an
appropriate prompt.
    Katz argues that there is a genuine factual issue as to
whether Student Registration discloses the “cue suppres-
sion” limitation of “utilizing, for qualified callers, the
identification signals relating to the callers, to avoid
prompting certain callers with a certain previously pro-
vided cue or cues.” The court construed that limitation to
require using “identification signals . . . to prevent” callers
from receiving previously provided prompts. In the
Student Registration system, students use their identifi-
cation numbers to register for courses, and the system
provides different messages depending on a student’s
registration status. For example, the system will use
Dialog #23 if the student wishes to be placed on a course
registration waiting list. If the student is already on the
waiting list, the system will not play Dialog #23 but will
instead play Dialog #27, which tells the student that he or
she is already registered or is on the waiting list for the
course. Katz argues that the asserted claims of the ’120
patent require a system that tracks the cues a user has
received, and that Student Registration discloses a sys-
RONALD A KATZ TECH   v. AMERICAN AIR                    34

tem that tracks only the student’s registration status.
The asserted claims, however, simply require using
identification signals to avoid repeating cues; they do not
dictate how that must be accomplished. Because the
Student Registration system uses student numbers to
access the caller’s registration status and avoid giving
repeat cues, Student Registration clearly discloses the
“cue suppression” limitation.
     Katz next argues that it would not have been obvious
to combine Student Registration and Szlam to create the
invention of claim 67 of the ’120 patent, which bases cue
suppression on ANI data. Katz contends that students’
mobility and their tendency to share telephone numbers
would cause “unpredictable and disastrous results” in a
cue suppression system based solely on ANI data. The
problem with Katz’s argument is that claim 67 reads on
any method to suppress cues by identifying callers based
in part on ANI data. And Student Registration discloses
multi-faceted identification techniques such as using a
personal identification number or a birth date in addition
to a registration number. Claim 67 is therefore an obvi-
ous combination of Student Registration’s cue suppression
with the ANI-based identification process of Szlam. See
KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 417 (2007)
(“[I]f a technique has been used to improve one device,
and a person of ordinary skill in the art would recognize
that it would improve similar devices in the same way,
using the technique is obvious unless its actual applica-
tion is beyond his or her skill.”).
                             VI
    Katz next appeals three of the district court’s claim
constructions pertaining to several of the asserted claims.
However, none of those claim construction issues gives
rise to reversible error.
35                      RONALD A KATZ TECH   v. AMERICAN AIR

                             A
     Claim 31 of the ’965 patent (the Voice-Data patent)
recites a method claim for controlling communications in
a communications facility, including the step of “generat-
ing computer acknowledgement numbers to identify the
transaction for the system and individual callers and
providing said computer acknowledgement numbers to
the individual callers.” The district court construed the
term “acknowledgement number” as “a number used by a
caller to verify or acknowledge a transaction to the sys-
tem.” That construction does not specify how the caller
uses the number to acknowledge a transaction to the
system. One reasonable reading of the court’s construc-
tion is that the caller enters the number to the system.
Another is that the caller listens to the number and then
confirms that it is correct. A third possible reading is that
the caller simply listens to the number and does not need
to provide any confirmation to the system, i.e., the trans-
action is “to the system,” but the acknowledgement is not.
In a subsequent opinion, the district court held “there is
nothing within the specification or the term itself that
requires an acknowledgment number to be provided to the
system.” The appellees, however, contend that the dis-
trict court’s construction requires the caller to repeat the
acknowledgment number to the system.
     Katz argues that a construction that requires the
caller to enter a confirmation number into the system
would erroneously limit the proper scope of the claims by
importing limitations from a single embodiment. We
agree. While the health poll embodiment of the ’762
patent requires the user to enter the acknowledgement
number into the system as a security measure, ’762
patent, col. 8, ll. 43-49, another embodiment does not
require the user to enter the acknowledgement number,
id., col. 11, ll. 49-58. And an embodiment from the ’965
RONALD A KATZ TECH   v. AMERICAN AIR                      36

patent explicitly states that the caller may enter the
acknowledgement number but is not required to do so.
’965 patent, col. 12, ll. 57-59. 14 Because there is a strong
presumption against a claim construction that excludes a
disclosed embodiment, Chimie v. PPG Indus., Inc., 402
F.3d 1371, 1377 (Fed. Cir. 2005), we reject the appellees’
interpretation of the term “acknowledgement number” as
a number that the caller must repeat to the system.
Instead, we hold that the correct construction of “ac-
knowledgement number” is “a number that can be used by
a caller to identify a transaction.” This construction does
not affect any of the district court’s summary judgment
rulings, however, because we have affirmed the district
court’s ruling that claim 31 is invalid for obviousness, and
the construction of the term “acknowledgement number”
does not affect that ruling.
                             B
    Based on an argument Katz made during reexamina-
tion to avoid prior art, the district court construed the
term “personal identification data” to have a meaning
distinct from passwords and PIN numbers. From the
Statistical Interface group, claim 43 of the ’863 patent and
claim 18 of the ’547 patent cover the use of “personal
identification data.” In response to the examiner’s rejec-
tion on reexamination based on Yoshizawa’s use of a


    14  The parties agree that the term “acknowledge-
ment number” has the same meaning in the ’762 patent
as in the ’965 patent. Our holding, however, is limited to
the meaning of the term “acknowledgement number” in
the ’965 patent because no claims of the ’762 patent have
been selected against any of the appellees. If defendants
other than the appellees wish to argue for a different
construction for the ’762 patent, they would be free to do
so unless they had agreed that the terms should have a
consistent meaning across both patents.
37                      RONALD A KATZ TECH   v. AMERICAN AIR

password as the “personal identification data,” Katz
explained:
     Although the Examiner alleges that the password
     entered by a subscriber satisfies the “one other
     distinct identification data element,” the Patentee
     respectfully submits that the claim requires that
     “one other distinct identification data element” to
     be “personal identification data” of the caller. A
     password that is composed (and frequently
     changed) serves as an access code or PIN, rather
     than personal identification data. . . . [S]everal
     examples of personal identification data [include]
     a caller’s name, address, telephone number, ini-
     tials, age, etc.
     On appeal, Katz argues that the distinction it prof-
fered in reexamination did not have the effect of disclaim-
ing all passwords or PINs, particularly those that are not
arbitrarily composed and are not frequently changed. We
reject that argument. Katz’s disclaimer distinguished
“personal identification data” from all composed pass-
words, not just arbitrarily composed passwords. For
example, Katz disclaimed the use of passwords that can
be composed and changed, including passwords that are
initially set to telephone numbers or other personal
identification data. Katz contends that would-be infring-
ers could circumvent the patent simply by labeling “per-
sonal identification data” as a “password.” For example,
Katz envisions a circumventing system that assigns a
user’s social security number to the user as a “password.”
However, such a concern is not present in this case and
could be addressed by determining whether the purported
password can be composed and changed. If the system
allowed the user to change his password from his social
security number to another phrase of his choosing, that
system would lie outside the scope of Katz’s claims in
light of the prosecution history. We therefore find no
RONALD A KATZ TECH   v. AMERICAN AIR                      38

error in the district court’s claim construction of “personal
identification data.”
                             C
    For several patents in the Statistical Interface group,
the district court construed the term “customer number”
to mean a number assigned to a customer by a vendor or
recognized by the vendor for the purpose of identifying the
customer. The court further construed that term to be
distinct from a credit card number. The court’s construc-
tion applied to the use of that term in claim 18 of the ’360
patent and claim 43 of the ’863 patent. Katz appeals the
district court’s construction of “customer number,” noting
that the specification contains embodiments in which a
“credit card number” is used to identify people. However,
Katz is unable to point to any place in the specification
where the term “credit card number” is linked to the term
“customer number.” The only references to both terms
indicate that they are used for different purposes. A
figure in the specification shows “customer number” and
“credit card number” as two distinct fields. See ’863
patent, fig. 5. Additionally, claim 32 of the ’762 patent
treats the two elements as distinct. It recites a means to
provide signals “indicative of an individual caller’s cus-
tomer number and credit card number” and a structure
“to verify said individual caller’s customer number and
credit card number to determine said individual caller’s
credit.” Because we ordinarily interpret claims consis-
tently across patents having the same specification, NTP,
Inc. v. Research in Motion, Ltd., 418 F.3d 1282, 1293 (Fed.
Cir. 2005), we agree with the district court’s construction
of the term “customer number.”
                            VII
   Finally, Katz appeals from the district court’s sum-
mary judgment determinations that U.S. Bank, American
39                     RONALD A KATZ TECH   v. AMERICAN AIR

Airlines, and DHL did not infringe the remaining claims
selected against them. Claim 63 of the ’120 patent was
asserted only against DHL and is the only remaining
claim against DHL. Because we have sustained the
district court’s order invalidating that claim, we do not
address the infringement issue as to that claim.
                            A
    Katz appeals from the district court’s summary judg-
ment that U.S. Bank’s accused systems do not infringe
Statistical Interface claims 43 and 49 of the ’863 patent
and Conditional Interface Plus claims 19, 49, and 71 of
the ’285 patent. Those claims require that the interface
structure or method include means or a step for receiving
“dialed number identification service” (“DNIS”) data
signals, which the court construed to mean data or signals
“that identify the number called” by the party calling the
data processing system.
    Although the parties do not disagree with the court’s
construction of the term DNIS, they disagree about the
meaning of the court’s construction. Specifically, Katz
argues that the DNIS limitation, as construed by the
court, is satisfied as long as the accused system assigns a
distinct value to each called number, which can be used to
identify the called number and route incoming calls
accordingly. U.S. Bank seems to argue that the court’s
construction of the DNIS limitation requires that the
accused system actually store the ten-digit telephone
number dialed by the caller, rather than a value that
“identifies” that number in some other fashion. In the
summary judgment opinion, it appears that the district
court may have adopted that narrower interpretation, as
it remarked that U.S. Bank’s system did not store the
called number itself, but only a shorter number that
represented the called number.
RONALD A KATZ TECH   v. AMERICAN AIR                    40

    The district court’s brief discussion of the DNIS issue
leaves it unclear whether the court’s construction of the
DNIS limitation requires that the accused system use the
full ten-digit called telephone number or merely some
other representation that uniquely identifies the called
number. Because the parties have addressed this issue
only fleetingly in their briefs, we vacate the court’s sum-
mary judgment order as to these claims and remand for
the district court to resolve this issue of claim construc-
tion.
    U.S. Bank argued in the alternative that, even under
the broader interpretation of the court’s claim construc-
tion advocated by Katz, the accused U.S. Bank systems do
not infringe because they lack signals that uniquely
identify the called number. The accused systems use only
five digits, which are sometimes referred to as vector
directory numbers (“VDNs”). U.S. Bank’s expert, Dr. Paul
S. Min, stated that one VDN can correspond to many
called numbers in the accused system and thus does not
uniquely identify the number called. If Dr. Min’s state-
ment had been undisputed, summary judgment of nonin-
fringement would have been proper. Katz, however,
pointed to a genuine factual dispute over whether the five
digit codes can identify the called number in the accused
systems. Katz’s expert, Dr. David Lucantoni, noted that
U.S. Bank uses the terms VDN and DNIS interchangea-
bly to refer to five digit codes. U.S. Bank contends that
Dr. Lucantoni’s conclusion was wholly unsupported, but
some of the documentation supporting U.S. Bank’s sum-
mary judgment motion labels five-digit codes as DNIS,
not VDN. Other U.S. Bank documents specifically direct
the creation of a one-to-one relationship between the
assigned DNIS values and the numbers dialed by callers.
Because the evidence suggests U.S. Bank’s systems use
five-digit codes to uniquely identify called numbers, we
conclude that summary judgment in U.S. Bank’s favor on
41                      RONALD A KATZ TECH   v. AMERICAN AIR

the DNIS issue was improper under the broader construc-
tion of the term DNIS.
    Katz also appeals from the district court’s summary
judgment that U.S. Bank’s accused system does not
infringe claim 5 of the ’223 patent. Katz first appeals the
district court’s implicit claim construction that “means for
selectively receiving calls” requires that some of the calls
not be received by the system. Katz contends that the
court’s construction would not cover one of the disclosed
embodiments, in which different audio response units
(“ARUs”) receive different categories of calls, i.e., calls to
800 numbers, calls to 900 numbers, and calls to area code
numbers. We disagree. The system as a whole has to
selectively receive calls because the “means for selectively
receiving calls” consists of “means for receiving calls in a
plurality of call modes” including the 800, 900, and area
code modes. Katz’s contention that each ARU is the
“means for selectively receiving calls” fails because claim
5 makes clear that the “means for selectively receiving
calls” consists of multiple ARUs. Additionally, the em-
bodiment Katz points to does not receive all calls, because
calls in the 800 and area code calling modes will be
aborted under certain conditions. See ’223 patent, fig. 2.
    We reject Katz’s argument that the accused system
does not receive all calls. Both parties agree that the
accused system consists of a public branch exchange
(“PBX”), which connects calls to an interactive voice
response unit (“IVR”). Katz’s expert, Dr. Lucantoni,
stated that in the accused system some calls are never
received by the IVR portion of the system, but he did not
dispute that all of the calls are received by the PBX
portion of the system. Dr. Lucantoni’s contention that the
IVR “selects” not to receive certain calls was based on his
description of several “examples” of instances in which the
IVR does not receive calls. The examples cited by Dr.
Lucantoni, however, do not support his characterization of
RONALD A KATZ TECH   v. AMERICAN AIR                       42

the accused system. He pointed to a failure to connect
due to a theoretical corrupted data packet. He also gave
the theoretical example of holding a call in a queue until
an IVR is available and, after an extended delay, cancel-
ing the call if an IVR is still not available. In both of
those examples, the system was designed to connect all
calls to an IVR but was vulnerable to failure due to un-
foreseen circumstances. A reasonable jury could not
conclude from those examples that that the accused
system selects not to receive calls in the same way the
’223 patent provides that calls will be aborted in order to
“limit repeat-call advantages” to callers who seek to place
multiple calls to the system. See ’223 patent, fig. 2, col. 3,
ll. 21-25. Accordingly, we affirm the summary judgment
of noninfringement as to claim 5 of the ’223 patent.
                              B
    American Airlines moved for summary judgment of
noninfringement, contending that its accused system
lacked a “record structure” that stored both “called data
signals” developed by caller-operated touchtone tele-
phones and “caller data” entered into the system by live
operators. For those reasons, American Airlines argued,
its accused system did not satisfy the “record structure”
limitation of claim 43 of the ’863 patent. In response to
that motion, Katz changed its infringement theory after
the close of discovery to assert that SABRE, a third-party
system used by American Airlines, was the infringing
record structure. Katz had previously contended that the
“record structure” was a combination of two structures—
SABRE and a system referred to as Periphonics IVR.
Although the district court stated that it was “troubled”
by the last-minute switch in Katz’s theory, the court
viewed the issue of the belated assertion of Katz’s in-
fringement theory as moot because it concluded that
American Airlines did not infringe even under Katz’s new
43                      RONALD A KATZ TECH   v. AMERICAN AIR

theory. We hold that summary judgment on Katz’s new
theory was inappropriate. We therefore vacate the dis-
trict court’s summary judgment order and remand to the
district court the portion of the case involving the asser-
tion of claim 43 of the ’863 patent against American
Airlines. On remand, the district court may revisit the
question whether Katz timely asserted its present in-
fringement theory under that claim.
     Katz’s new theory is that SABRE is a “record struc-
ture” that “receive[s] said caller data signals from said
interface structure for accessing a file and storing certain
of said data developed by said remote terminals,” as
required by claim 43. See ’863 patent, col. 25, ll. 21-25
(independent claim 27, from which claim 43 depends).
American Airlines contends that Katz’s theory has two
deficiencies. First, American Airlines argues that receiv-
ing and storing caller-entered data is insufficient because
the record structure must “receive said caller data sig-
nals” and store “data developed by said remote termi-
nals.” Id. For that reason, it argues, claim 43 requires
that the system receive and store touchtone signals
generated when users actuate the buttons on a remote
terminal (e.g., a telephone), rather than receiving and
storing bits representing the signals. Putting aside the
physical challenges associated with storing “signals,” the
difficulty with American Airlines’ construction is that the
“record structure” receives the signals from the “interface
structure.” And the “interface structure” does not provide
touchtone signals to the record structure, but instead
provides “caller data signals representative of data . . .
developed by said remote terminals.” Id., col. 25, ll. 14-16.
Thus, receiving and storing information representative of
the caller-entered data is sufficient to infringe.
    Second, American Airlines contends that Katz fails to
point to any evidence that SABRE receives and stores
information representative of caller-entered data. We
RONALD A KATZ TECH   v. AMERICAN AIR                       44

disagree. There is at least a genuine issue of material
fact as to whether SABRE stores information representa-
tive of caller-entered data. Katz submitted an expert’s
infringement report stating that the SABRE collects
information from the caller and stores the information in
the SABRE database including passenger and flight
information. That evidence is supported by an American
Airlines document entitled “Dialog Specification: Non
Revenue Travel Application.” That document describes a
telephone-interface system that collects caller-entered
data including passenger and flight information. In
describing eligibility checks for various flight bookings,
the document states that “SABRE will also check for
[various eligibility criteria] when trying to build the
[passenger record], and will return a specific error code.”
This implies that SABRE receives and stores caller-
entered data. Because there is a genuine issue of mate-
rial fact as to whether American Airlines’ system receives
and stores information representative of caller-entered
data, we vacate the district court’s summary judgment of
noninfringement against American Airlines on claim 43 of
the ’863 patent and remand for further proceedings on
that issue, subject to the district court’s revisiting, at its
discretion, the timeliness of Katz’s assertion of its current
infringement theory.
                            VIII
    Katz appeals many of the district court’s rulings on
claims that were not selected against any of the appellees.
Because those claims are not at issue in this appeal, we
do not address Katz’s arguments with respect to the
district court’s rulings on those claims. Those rulings are
the following: the court’s indefiniteness rulings as to
claim 11 of the ’021 patent, claim 19 of the ’547 patent,
claim 116 of the ’707 patent, claim 34 of the ’551 patent,
claim 4 of the ’893 patent, and claims 41 and 42 of the
45                      RONALD A KATZ TECH   v. AMERICAN AIR

’309 patent; the court’s written description rulings as to
claim 34 of the ’551 patent, claim 32 of the ’120 patent,
claims 18, 106, 110, 114, and 119 of the ’360 patent, and
claims 1, 7, 51, 58, and 86 of the ’223 patent; the court’s
obviousness ruling as to claim 43 of the ’965 patent; and
the court’s claim construction ruling as to claim 32 of the
’762 patent. While we do not directly address any of those
issues, any further proceedings relating to those issues
may, of course, be affected by our analysis of related
issues in this opinion.
     Each party shall bear its own costs for these appeals.
     AFFIRMED IN PART, VACATED IN PART, and
                  REMANDED
