  United States Court of Appeals
      for the Federal Circuit
                ______________________

                 STARHOME GMBH,
                  Plaintiff-Appellant,

                           v.

   AT&T MOBILITY LLC, ROAMWARE, INC., AND
            T-MOBILE USA, INC.,
             Defendants-Appellees.
            ______________________

                      2012-1694
                ______________________

    Appeal from the United States District Court for the
District of Delaware in No. 10-CV-0434, Chief Judge
Gregory M. Sleet.
                 ______________________

              Decided: February 24, 2014
               ______________________

    JOHN M. DIMATTEO, Willkie Farr & Gallagher, LLP,
of New York, New York, argued for plaintiff-appellant.
With him on the brief was ROBERT G. KOFSKY. Of counsel
was JESENIA M. RUIZ DE LA TORRE.

    MARK A. PERRY, Gibson Dunn & Crutcher, LLP, of
Washington, DC, argued for defendants-appellees. On the
brief were JOSH KREVITT, BENJAMIN HERSHKOWITZ, and R.
SCOTT ROE, of New York, New York; and FREDERICK
CHUNG, of Palo Alto, California.
                 ______________________
2                     STARHOME GMBH    v. AT&T MOBILITY LLC




    Before MOORE, SCHALL, and REYNA, Circuit Judges.
SCHALL, Circuit Judge.
    This is a patent infringement case. Starhome GmbH
(“Starhome”) sued AT&T Mobility LLC, Roamware, Inc.,
and T-Mobile USA, Inc. (“Defendants”), in the United
States District Court for the District of Delaware for
infringement of U.S. Patent No. 6,920,487 (the “’487
patent”). The ’487 patent is titled “System and Methods
for Global Access to Services for Mobile Telephone Sub-
scribers.” It relates generally to a way of improving the
functionality of phone services for users in a roaming
telephone network. To allow users in a roaming network
to make calls as if in their home network, the ’487 patent
discloses the use of an “intelligent gateway.”
    Following a Markman hearing, the district court con-
strued various terms of the ’487 patent. Among them was
the term “intelligent gateway,” which the court construed
to mean “a network element that transfers information to
and from a mobile network and another network external
to the mobile network.” Relying upon that construction,
Defendants moved for summary judgment of nonin-
fringement. Starhome did not contest the motion, but
instead stipulated to a judgment of noninfringement
based upon the court’s construction of “intelligent gate-
way.” Following the district court’s entry of the stipulated
judgment on September 12, 2012, Starhome GmbH v.
AT&T Mobility LLC, No. 1:10-cv-00434-GMS (D. Del.
Sept. 12, 2012), Starhome appealed. We affirm.
                       BACKGROUND
            I. STARHOME AND THE ’487 PATENT
    Starhome owns the ’487 patent. The problem the pa-
tent aims to solve arises when mobile phone users are in a
network other than their home network (e.g., roaming).
In a home network, a mobile phone user might dial a
STARHOME GMBH    v. AT&T MOBILITY LLC                       3



short code, such as “121,” to access voice mail. But while
roaming, the visiting network may not recognize the code,
resulting in an error message. As another example, a
user from Germany visiting the United States may want
to call home to Germany, but if the user does not enter
the correct international direct-dialing prefix and country
code, the call will not connect.
    The ’487 patent’s solution to this problem is the “intel-
ligent gateway.” Figure 1 of the ’487 patent, shown below,
demonstrates a system (10) providing roaming services
and employing the intelligent gateway.




    As shown in Figure 1, the intelligent gateway (V-I/G
32) has a database (DB 31) that contains information
about multiple home networks, including short-code
translation tables, subscriber profile data, and roaming
patterns. ’487 patent col. 2 ll. 33–41. The information in
the database may be updated via a global packet-switch
network (22). Id. col. 2 ll. 33–36, col. 4 ll. 33–36. Figure 2
of the ’487 patent, shown below, demonstrates a call flow
4                       STARHOME GMBH     v. AT&T MOBILITY LLC



of a short-coded call or erroneous full-number call in
accordance with the system of Figure 1. Id. col. 1 ll. 43–
44, col. 3 ll. 24–27. The specification explains that, “[i]n
order to simplify the picture, the mobility probe and its
Interfaces are not shown.” Id. col. 3 ll. 27–29.




     In Figure 2, the visited mobile network (VPLMN 30)
has a switching center (V-MSC 34) supporting a roaming
cell phone (39). If the roaming subscriber (39) dials a
phone number that the switching center (34) cannot place
(e.g., a voice mail short code like “121”) (step 1), the call is
routed to the intelligent gateway (V-I/G 32) (step 2). The
intelligent gateway, which has knowledge of the home-
network dialing format and short codes, translates the
sequence into one the switch (34) will recognize and sends
the corrected dialing sequence back to the switch (step 3).
The call is then routed by the switch to the international
telephone network (step 4), and the network sends the
call to its intended destination (step 5). Id. col. 3 l. 30 –
col. 4 l. 5.
STARHOME GMBH   v. AT&T MOBILITY LLC                       5



    Starhome sells its intelligent gateway solution as the
IntelliGate™ and has installed it in over 130 mobile
networks throughout the world.
       II. DEFENDANTS AND THE ACCUSED PRODUCT
    Defendant Roamware sells a network platform that
runs Smart Call Assistant and Short Code applications.
Those applications allow mobile-network operators to
translate numbers dialed by roaming cell-phone users
visiting their networks. Defendants AT&T and T-Mobile
use the Roamware platforms in their networks. Notably,
the Roamware platform does not connect to an external
packet-switch network or other external network.
          III. THE DISTRICT COURT PROCEEDINGS
    Starhome filed its complaint against Defendants on
May 25, 2010, asserting infringement of the ’487 patent
and U.S. Patent No. 7,231,431 (the “’431 patent”), which
is a continuation of the ’487 patent. The parties disputed
multiple terms in the patents, one being the term “intelli-
gent gateway.” Starhome proposed that the term meant
“a network element that uses knowledge implemented in
databases or the like and application logic to perform its
operations.” Defendants argued that the term meant “a
network element that transfers information to and from a
mobile network and another network external to the
mobile network.”
    After briefing and a Markman hearing, the district
court issued its claim construction order. In that order,
the court found that the word “gateway” had a well-
known technical meaning in the telecommunications
industry when the application for the asserted patents
was filed. In support of its finding, the court relied on the
Institute of Electrical and Electronics Engineers (“IEEE”)
dictionary, which describes a “gateway” as a device that
connects two or more networks. Concluding that the
6                     STARHOME GMBH   v. AT&T MOBILITY LLC



inventors did not clearly redefine the term, the court
accepted Defendants’ proposed construction.
     Based on the claim construction order, the parties
filed letter briefs requesting permission to move for sum-
mary judgment. Finding that Defendants set forth a
compelling argument for non-infringement based on the
construction of “intelligent gateway,” the court granted
Defendants’ request. Rather than formally brief the
issue, Starhome stipulated to the entry of judgment of
noninfringement.
    Starhome timely appealed as to the ’487 patent.
Starhome no longer asserts the ’431 patent. We have
jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).
                       DISCUSSION
                 I. STANDARD OF REVIEW
    Where, as here, a plaintiff concedes noninfringement
by stipulation, we need only address the district court’s
construction of the pertinent claims. Altiris, Inc. v. Sy-
mantec Corp., 318 F.3d 1363, 1368 (Fed. Cir. 2003).
Claim construction is a question of law that we review de
novo. Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448,
1451 (Fed. Cir. 1998) (en banc).
              II. THE PARTIES’ CONTENTIONS
    Starhome asserts independent claims 10 and 40 of the
’487 patent. Claim 10 recites the following:
      10. A system comprising:
      an intelligent gateway associated with a first
    mobile telephone network,
       said first mobile telephone network having
    connections to other mobile telephone networks,
       said intelligent gateway adapted to translate a
    dialing sequence when dialed by a roaming cellu-
STARHOME GMBH   v. AT&T MOBILITY LLC                       7



    lar telephony device roaming in said first mobile
    network into a destination number,
       said roaming cellular telephony device having
    a home network which is other than said first mo-
    bile network;
      and a routing center in said first mobile tele-
    phone network,
       said routing center adapted to route said dial-
    ing sequence within said first mobile telephone
    network to said intelligent gateway for said trans-
    lating.
Claim 40 recites the following:
        40. An intelligent gateway associated with a
    first cellular telephony network,
       adapted to provide assistance to a cellular te-
    lephony device roaming in said first cellular te-
    lephony network to complete calls when a
    destination number dialed by said roaming cellu-
    lar telephony device is erroneous,
       said roaming cellular telephony device being
    registered as a home device in a second cellular
    telephony network being distinct from said first
    cellular telephony network, and
       said intelligent gateway being adapted to ob-
    tain information for said call completion using
    knowledge of said second cellular telephony net-
    work.
    On appeal, Starhome asserts the same construction of
“intelligent gateway” that it urged in the district court (“a
network element that uses knowledge implemented in
databases or the like and application logic to perform its
operations”). In support of that construction, Starhome
argues that the specification does not require the gateway
8                     STARHOME GMBH   v. AT&T MOBILITY LLC



to be connected to an external network. Rather, Star-
home contends, the specification explains that the intelli-
gent gateway has a local database of information it
accesses to perform its functions. Some embodiments
employ a single intelligent gateway associated with a
single mobile network, Starhome argues, while others
disclose multiple intelligent gateways associated with an
external packet-switch network. The critical part of the
specification, Starhome continues, is Figure 2, which
shows the intelligent gateway connected solely to the
internal network. Construing “intelligent gateway” to
require the transfer of information to and from an exter-
nal network, Starhome concludes, expressly excludes the
embodiment of Figure 2.
    Further, Starhome argues, claim differentiation sup-
ports its proposed construction. According to Starhome,
claims 10 and 40 do not expressly or impliedly require the
intelligent gateway to transfer information to and from an
external network. By contrast, unasserted claims 1 and
47 recite a connection to an external packet-switch net-
work. This substantive difference between the claims,
Starhome concludes, demonstrates that a connection to an
external network is not a required feature of an intelli-
gent gateway.
    Defendants argue that the patentee used the specific
term “gateway” rather than a generic network element,
and that the common usage of that term should control.
Defendants thus argue that the district court correctly
construed “intelligent gateway” as “a network element
that transfers information to and from a mobile network
and another network external to the mobile network.” In
support of that construction, Defendants point to three
dictionaries showing that “gateway” refers to a point of
interconnection between networks at which information
transfer occurs.
STARHOME GMBH   v. AT&T MOBILITY LLC                      9



     Further, Defendants argue, the specification describes
the “present invention” as intelligent gateways connecting
different networks. Likewise, Defendants continue, the
’487 patent incorporates by reference a Patent Coopera-
tion Treaty (“PCT”) application, which describes the
“present invention” as a system that “transfer[s] certain
signals over a packet-switch network through service
nodes connected to the telephone networks.” Joint Ap-
pendix (“J.A.”) 4803. The service nodes are intelligent
gateways, Defendants contend, and are associated with a
first mobile network directly connected to an external
network.
    Moreover, Defendants argue, every embodiment in
the ’487 patent requires the intelligent gateway to direct-
ly connect different networks. In the first embodiment
(Figures 1 and 2), the visited mobile network may be
coupled to a global packet-switch network via a visited
intelligent gateway. In the second embodiment (Figures
3–5), in addition to the visited intelligent gateway, a
home network is coupled to a global packet-switch net-
work via a home intelligent gateway. Notably, Defend-
ants argue, the specification describes no system where
the intelligent gateway is not connecting two different
networks.
    Regarding Starhome’s argument that Figure 2 is a
separate embodiment, Defendants respond that the figure
merely illustrates a call flow occurring within the larger
system of Figure 1. The figure omits components not
essential to explaining the call flow, Defendants continue,
and is not a separate embodiment.
    Turning to Starhome’s argument based upon claim
differentiation, Defendants respond that the doctrine does
not apply because each dependent claim in the ’487 patent
adds a feature not otherwise required by the independent
claims. Specifically, Defendants argue, the district court’s
construction requires access to a generic external net-
10                    STARHOME GMBH    v. AT&T MOBILITY LLC



work, but the dependent claims recite access to a specific
type of network.
    In further support of their position, Defendants point
to statements that Starhome made in a related foreign
application. To overcome prior art during prosecution of a
European application that claims priority to the same
provisional application as the ’487 patent, Starhome
argued that “a gateway provides access to an external
environment beyond the immediate network,” and is
defined “in terms of an access means from one network to
another.” Those statements, Defendants urge, should
preclude Starhome from now advocating a broader con-
struction.
    In response, Starhome argues that its statements in
connection with the PCT application are consistent with
its proposed construction. The prior art at issue in the
European application did not involve roaming, Starhome
continues, so when the prosecuting attorney said the
gateway accessed an external network, he was referring
to another telephone network. Accessing a separate
telephone network, Starhome concludes, is exactly what
the intelligent gateway accomplishes.
                       III. ANALYSIS
    “The words of a claim are generally given their ordi-
nary and customary meaning as understood by a person
of ordinary skill in the art when read in the context of the
specification and prosecution history.” Thorner v. Sony
Computer Entm’t Am. LLC, 669 F.3d 1362, 1365 (Fed. Cir.
2012) (citing Phillips v. AWH Corp., 415 F.3d 1303, 1313
(Fed. Cir. 2005) (en banc)). “There are only two excep-
tions to this general rule: 1) when a patentee sets out a
definition and acts as his own lexicographer, or 2) when
the patentee disavows the full scope of a claim term either
in the specification or during prosecution.” Id. (citing
Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1580
(Fed. Cir. 1996)).
STARHOME GMBH   v. AT&T MOBILITY LLC                     11



    We have made clear that dictionaries and treatises
can often be useful in claim construction, particularly
insofar as they help the court “‘to better understand the
underlying technology’ and the way in which one of skill
in the art might use the claim terms.” Phillips, 415 F.3d
at 1318 (quoting Vitronics Corp., 90 F.3d at 1584 n.6).
Moreover, judges are free to rely on dictionaries at any
time during the process of construing claims “so long as
the dictionary definition does not contradict any definition
found in or ascertained by a reading of the patent docu-
ments.” Id. at 1322–23 (quoting Vitronics Corp., 90 F.3d
at 1584 n.6).
    Both asserted claims recite an “intelligent gateway.”
The term “gateway” had a well-understood meaning in
the art at the time the patentees filed the application that
led to the ’487 patent. As evidenced by technical diction-
aries, one of ordinary skill in the art would have under-
stood a “gateway” to be a connection between different
networks. See Andrew S. Tanenbaum, Computer Net-
works 16 (3d ed. 1996) (describing a gateway as a means
to connect networks and provide necessary translation);
Harry Newton, Newton’s Telecom Dictionary 362–63 (15th
ed. 1999) (“A gateway is what it sounds like. It’s an
entrance and exit into a communications network.”); The
IEEE Standard Dictionary of Electrical and Electronic
Terms 449 (6th ed. 1996) (defining a “gateway” as a device
that connects two systems or networks).
    Considering “gateway” in the context of the claims
and specification of the ’487 patent, one of ordinary skill
would have understood that the inventors did not depart
from the ordinary meaning of “gateway” with their use of
the term “intelligent gateway.” The gateway is intelligent
because it includes a database of information and is
adapted to do things such as translate dialing sequences,
deliver short messages, provide assistance, and obtain
information for call completion. ’487 patent col. 2 ll. 33–
38, claims 10, 35, and 40. But, consistent with its ordi-
12                    STARHOME GMBH    v. AT&T MOBILITY LLC



nary meaning, the specification also explains that it
connects different networks. For example, when describ-
ing the services performed by the invention, the specifica-
tion explains that “[t]he system providing these services is
based upon a configuration comprising a global packet
switch network connecting mobile networks via intelligent
gateways.” Id. col. 2 ll. 19–21. Further, in describing the
invention, the specification discloses two main embodi-
ments. The first—shown in Figure 1—contains a visited
mobile network coupled to a packet-switch network via a
single intelligent gateway. The second—shown in Figures
3, 4, and 5—contains two mobile networks coupled to a
packet-switch network via two intelligent gateways.
After reading the claims and specification, one of ordinary
skill in the art would therefore have understood that
“intelligent gateway” carries its ordinary meaning as a
device that connects different networks.
    Starhome relies on Figure 2 to support its proposed
construction, arguing that the figure shows an intelligent
gateway operating within a single network, thus consti-
tuting a preferred embodiment excluded by the district
court’s construction. If true, Starhome’s argument would
carry force because a construction that excludes a pre-
ferred embodiment “is rarely, if ever, correct and would
require highly persuasive evidentiary support.” Vitronics
Corp., 90 F.3d at 1583. However, although Starhome
correctly points out that Figure 2 does not show a connec-
tion to a packet-switch network, we disagree that it
constitutes a separate embodiment. The specification
explains that Figure 2 is a simplified drawing of a call
flow in accordance with the system of Figure 1. ’487
patent col. 1 ll. 43–44, col. 3 ll. 23–29. The packet-switch
network of Figure 1 is not needed to explain the call flow,
and one of ordinary skill in the art would understand that
the drawing omits it for that reason. At best, Figure 2
inserts ambiguity as to whether the patentees intended to
depart from the ordinary meaning of “intelligent gate-
STARHOME GMBH   v. AT&T MOBILITY LLC                      13



way.” But such ambiguity does not rise to the level of the
clear intent our case law requires. See, e.g., Teleflex, Inc.
v. Ficosa N. Am. Corp., 299 F.3d 1313, 1325 (Fed. Cir.
2002) (“In the absence of an express intent to impart a
novel meaning to claim terms, an inventor’s claim terms
take on their ordinary meaning. We indulge a ‘heavy
presumption’ that a claim term carries its ordinary and
customary meaning.” (internal citations omitted)). Ac-
cordingly, we find nothing in the specification that indi-
cates a clear intent to depart from the ordinary meaning
of “intelligent gateway.”
    Starhome further argues that the doctrine of claim
differentiation supports its proposed construction. As
Starhome’s argument goes, unasserted claims 1 and 47
require the intelligent gateway to connect to an external
packet-switch network, whereas asserted claims 10 and
40 do not. The district court’s construction, Starhome
continues, ignores this distinction and improperly imports
the limitation of an external packet-switch network into
every claim. We disagree.
    The doctrine of claim differentiation is “based on the
common sense notion that different words or phrases used
in separate claims are presumed to indicate that the
claims have different meanings and scope.” Karlin Tech.
Inc. v. Surgical Dynamics, Inc., 177 F.3d 968, 971–72
(Fed. Cir. 1999). The doctrine is not a hard and fast rule,
but instead “a rule of thumb that does not trump the clear
import of the specification.” Edwards Lifesciences LLC v.
Cook Inc., 582 F.3d 1322, 1332 (Fed. Cir. 2009); see also
Netcraft Corp. v. eBay, Inc., 549 F.3d 1394, 1400 n.1 (Fed.
Cir. 2008) (“While claim differentiation may be helpful in
some cases, it is just one of many tools used by courts in
the analysis of claim terms.”). The doctrine does not
control the outcome here. The district court’s construction
of “intelligent gateway” requires that it transfer infor-
mation to and from a “network external to the mobile
network.” Claims 1 and 47, however, claim a specific type
14                    STARHOME GMBH   v. AT&T MOBILITY LLC



of external network; namely, a packet-switch network.
The claims differ in scope, therefore, and the district
court’s construction neither imports limitations from one
claim to another nor renders any claims redundant.
    To bolster their case, Defendants point to the prosecu-
tion history of a related European application. We have
previously held that statements made before foreign
patent offices are sometimes relevant to interpreting the
claims. See Gillette Co. v. Energizer Holdings, Inc., 405
F.3d 1367, 1374 (Fed. Cir. 2005) (relying on party admis-
sions before the European Patent Office to construe the
claims). But we have also cautioned against indiscrimi-
nate reliance on foreign file histories. See AIA Eng’g Ltd.
v. Magotteaux Int’l S/A, 657 F.3d 1264, 1279 (Fed. Cir.
2011) (“[T]he varying legal and procedural requirements
for obtaining patent protection in foreign countries might
render consideration of certain types of representations
inappropriate for consideration in a claim construction
analysis of a United States counterpart.” (internal quota-
tion marks omitted)). In this case, Starhome argued in a
related foreign application that “a gateway provides
access to an external environment beyond the immediate
network,” and that “the term ‘intelligent gateway’ is
defined in this way, that is in terms of an access means
from one network to another.” J.A. 181. Although we
view Starhome’s statements with the requisite caution,
they do provide yet another indication that the patentees
did not intend to depart from the ordinary meaning of
“intelligent gateway.”
    As noted, the district court accepted Defendants’ pro-
posed claim construction and construed “intelligent gate-
way” to mean “a network element that transfers
information to and from a mobile network and another
network external to the mobile network.” Because, as
discussed above, that construction is not inconsistent with
the ordinary meaning of “gateway,” we will not disturb it.
We have considered Starhome’s proposed construction of
STARHOME GMBH   v. AT&T MOBILITY LLC                     15



“intelligent gateway,” but because it does not reflect the
ordinary meaning of “gateway,” we conclude that it is not
correct.
    Turning to infringement, the parties stipulated that
“the accused systems do not directly transfer information
to and from a network external to the mobile network.”
J.A. 7. In addition, the parties agree that the accused
systems are not connected to an external packet-switch
network or other external network. Appellant’s Br. 16;
Appellee’s Br. 57. Because the term “intelligent gateway”
requires connection to an external packet-switch network
or other external network, there can be no infringement.
See Dynacore Holdings Corp. v. U.S. Philips Corp., 363
F.3d 1263, 1273 (Fed. Cir. 2004) (“To prove infringement,
the patentee must show that the accused device meets
each claim limitation, either literally or under the doc-
trine of equivalents.”). Accordingly, we affirm the district
court’s judgment of noninfringement.
                       CONCLUSION
     As set forth above, we see no error in the district
court’s construction of “intelligent gateway.” We therefore
affirm the judgment of noninfringement.
                       AFFIRMED
                          COSTS
   Each party shall bear its own costs.
