United States Court of Appeals 

for the Federal Circuit ______________________ 

BIOSIG INSTRUMENTS, INC.,

Plaintiff-Appellant, 

v.

NAUTILUS, INC.,

Defendant-Appellee.

______________________ 

2012-1289 

______________________ 

Appeal from the United States District Court for the 

Southern District of New York in No. 10-CV-7722, Judge 

Alvin K. Hellerstein. 

______________________ 

Decided: April 26, 2013 

______________________ 

MICHAEL J. BONELLA, Kessler Topaz Meltzer & Check 

LLP, of Radnor, Pennsylvania, argued for plaintiffappellant. With him on the brief was PAUL B. MILCETIC. 

Of counsel were TODD KUPSTAS and JENNA PELLECCHIA. 

JAMES E. GERINGER, Klarquist Sparkman, LLP, of 

Portland, Oregon, argued for defendant-appellee. With 

him on the brief were JOHN D. VANDENBERG and PHILIP 

WARRICK. 

______________________ 
2 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

Before NEWMAN, SCHALL, and WALLACH, Circuit Judges. 

Opinion for the court filed by Circuit Judge WALLACH. 

Concurring opinion filed by Circuit Judge SCHALL. 

WALLACH, Circuit Judge. 

 Biosig Instruments, Inc. (“Biosig”) is the assignee of 

U.S. Patent No. 5,337,753 (“the ’753 patent”), which is 

directed to a heart rate monitor associated with an exercise apparatus and/or exercise procedures. Biosig brought 

a patent infringement action against Nautilus, Inc. 

(“Nautilus”) in district court alleging that Nautilus infringed claims 1 and 11 of the ’753 patent. After claim 

construction, Nautilus filed a motion for summary judgment seeking, in relevant portion, to have the ’753 patent 

held invalid for indefiniteness. The district court granted 

Nautilus’s motion, and Biosig appealed. Because the 

claims at issue are not invalid for indefiniteness, the 

district court’s decision is reversed and remanded for 

further proceedings. 

BACKGROUND

I. 

 The ’753 patent is directed to a heart rate monitor 

that purports to improve upon the prior art by effectively 

eliminating noise signals during the process of detecting a 

user’s heart rate. ’753 patent col. 1 ll. 5–10. According to 

the patent, prior art monitors did not eliminate signals 

given off by skeletal muscles (“electromyogram” or “EMG” 

signals), which are brought about when users move their 

arms or squeeze the monitor with their fingers. Id. col. 1 

ll. 19–22. Because EMG signals are of the same frequency range as electrical signals generated by the heart 

(“electrocardiograph” or “ECG” signals), EMG signals can 

mask ECG signals rendering heart rate determination 

while exercising difficult. Id. col. 1 ll. 22–25. 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 3 

 The ’753 patent discloses an apparatus preferably 

mounted on exercise equipment that measures heart 

rates by, inter alia, processing ECG signals from which 

EMG signals are substantially removed. Id. col. 1. ll. 36–

41. The claimed heart rate monitor consists of an elongate hollow cylindrical member that houses electronic 

circuitry as illustrated below: 

’753 patent fig. 1. A user’s left and right hands—100 and 

200—each contact one of the “live” electrodes—9 and 13—

and one of the “common” electrodes—11 and 15—on either 

end of the cylindrical member 3. Id. col. 2 ll. 50–64, col. 3 

ll. 26–31. The electronic circuitry includes a difference 

amplifier 23, which is connected to the live electrodes 9 

and 13. Id. col. 3 ll. 7–10. The common electrodes 11 and 

15 are connected to each other and to a point of common 

potential, for example, a common ground. Id. col. 3 ll. 5–7. 

An illustration of the circuitry is shown below: 
4 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

’753 patent fig. 2. Inputs 25 and 27 are of opposite polarity. Id. col. 3 ll. 10–13. As the EMG signals and other 

noise signals are of substantially equal amplitude and 

phase, they cancel each other out in the difference amplifier to provide a substantially zero output of EMG and 

other noise signals. Id. col. 3 ll. 33–43. In contrast, ECG 

signals, being of opposite phase, will be added and therefore further amplified in the difference amplifier so that 

the output of the difference amplifier is substantially due 

to the ECG signals only. Id. col. 3 ll. 44–50. 

Claim 1 is representative and recites, in relevant part: 

1. A heart rate monitor for use by a user in association with exercise apparatus and/or exercise 

procedures, comprising: 

an elongate member; 

electronic circuitry including a difference amplifier having a first input terminal of a first polarity 

and a second input terminal of a second polarity 

opposite to said first polarity; 

said elongate member comprising a first half and 

a second half; 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 5 

a first live electrode and a first common electrode 

mounted on said first half in spaced relationship

with each other; 

a second live electrode and a second common electrode mounted on said second half in spaced relationship with each other; 

said first and second common electrodes being 

connected to each other and to a point of common 

potential . . . . 

’753 patent col. 5 ll. 17–36 (emphases added). In addition 

to the capability of substantially removing EMG signals, 

claim 1 recites a monitor, a means for measuring time 

intervals between heart pulses, and a means for calculating the heart rate of a user using the measured time 

intervals. See id. col. 5 l. 37–col. 6 l. 15. 

 Asserted–dependent claim 11 further specifies that 

the claimed “elongate member” is “mounted on an exercise apparatus.” Id. col. 7 ll. 17–20. Figures 7 and 8 are 

illustrative of a heart rate monitor mounted on a bicycle 

and a stair-climbing exercise machine: 
6 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

Id. figs. 7–8. 

II. 

The dispute between the parties has been ongoing for 

years, stemming from the late 1990s when Biosig was in 

discussions with Nautilus’s predecessor Stairmaster 

Company regarding Biosig’s patented technology. Despite 

these discussions, Stairmaster Company, and later Nautilus, began selling exercise equipment that Biosig alleges 

infringes its patented technology. These accused products 

consist of heart rate monitors mounted on exercise 

equipment. 

Biosig sued Nautilus for infringing the ’753 patent in 

August 2004 (“2004 Action”). During the pendency of that 

litigation, Nautilus twice sought ex parte reexamination of 

the ’753 patent from the United States Patent and 

Trademark Office (“PTO”). The first reexamination 

request was based primarily on U.S. Patent No. 4,444,200 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 7 

(“Fujisaki”).1 The PTO granted Nautilus’s request, and in 

April 2009, the PTO issued an office action rejecting, inter 

alia, claim 1 as anticipated by Fujisaki and claim 11 as 

obvious over Fujisaki in view of other prior art references. 

After Biosig filed its response to this PTO office action, 

Nautilus requested a second reexamination of the ’753 

patent, again, citing Fujisaki as the primary reference. 

The PTO granted Nautilus’s second request for reexamination, and the two reexamination proceedings were 

consolidated in December 2009. The PTO ultimately 

concluded these reexamination proceedings in June 2010 

and confirmed the patentability of the ’753 patent without 

amendment. During the pendency of this reexamination 

proceeding, the parties voluntarily dismissed without 

prejudice the claims and counterclaims of the 2004 Action. 

Upon conclusion of the reexamination proceeding, Biosig re-instituted a patent infringement action against 

Nautilus on October 8, 2010. On August 11, 2011, the 

district court conducted a Markman hearing, and on 

September 29, 2011, issued its order construing certain 

 

1 Fujisaki relates to a system for measuring heart 

pulse rate, and more particularly, to “a heart pulse rate 

measuring system having a pair of grip sensors adapted 

to be gripped with both hands for sensing heart pulse 

signals.” Fujisaki, col. 1 ll. 5–9. “Each of the grip sensors 

is composed of two conductive cylindrical electrodes 

arranged in an axially aligned relationship and electrically insulated from each other.” Id. col 1 ll. 45–48. “The 

electric circuit includes a differential amplifier having 

inputs from the grip sensors for amplifying the difference 

between the heart pulse signals . . . .” Id. col. 1 ll. 48–51. 
8 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

disputed claim terms.2 On November 10, 2011, Nautilus 

moved under Federal Rule of Civil Procedure 56 seeking 

summary judgment on two issues: infringement and 

invalidity for indefiniteness. 

On February 22, 2012, the district court held a hearing on Nautilus’s motion for summary judgment. As to 

the issue of infringement, the district court denied Nautilus’s motion as premature because the parties had yet to 

undertake significant discovery. Summ. J. Hr’g Tr. 5:23–

6:2, Biosig Instruments, Inc. v. Nautilus, Inc., No. 10–CV–

7722 (S.D.N.Y. Feb. 22, 2012), ECF No. 58 (“Summ. J. 

 2 Even though the district court issued a claim construction order, which included a construction of the 

disputed term, “spaced relationship,” the record reflects 

the district court nonetheless determined that “space 

relationship” was ambiguous, and therefore, found Biosig’s contentions pertaining to this term unpersuasive. 

J.A. 1391:15–21 (August 11, 2011 Markman Hearing) 

(“And we are going on to say, the spaced relationship 

arises from trial and error placements of the two electrodes on the cylindrical bar. Once placed they’re in a 

space relationship. That spaced relationship must be 

greater than the width of each electrode. What I’ve done 

will confuse the jury and it may set up Mr. Milcetic for a 

ruling of invalidity. Fair warning.”) (emphasis added); 

J.A. 2819:16–2820:1 (February 22, 2012 Summary Judgment Hearing) (“THE COURT: So he said a space[d] 

relationship can be anything. It could be this or it could 

be something else. MR. GERINGER: And, your Honor, at 

the time, it was Mr. Bonella’s colleague, I believe, Mr. 

Milcetic, but your Honor warned them that you didn’t 

want them to fall into a trap. THE COURT: Right. MR. 

GERINGER: That construing it in a way that embraces 

ambiguity could lead to invalidity through vagueness. 

THE COURT: And now you’re trying to take advantage of 

that right now.”) (emphases added). 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 9 

Hr’g Tr.”). On invalidity, the district court granted Nautilus’s motion, holding that the ’753 patent’s “spaced relationship” term as recited in claim 1 was indefinite as a 

matter of law. Summ. J. Hr’g Tr. 51:21–52:1. 

After the parties completed summary judgment briefing but before the hearing, Nautilus filed a third request 

for reexamination of the ’753 patent on January 25, 2012, 

and again, Nautilus cited Fujisaki as a primary prior art 

reference. This time, on February 17, 2012, the PTO 

denied Nautilus’s request, finding that there were no 

substantial new questions of patentability raised by the 

request. Biosig was notified of the PTO’s denial of Nautilus’s third reexamination request after the district court’s 

summary judgment hearing and decision. In light of this 

new fact, Biosig moved for reconsideration of the district 

court’s decision granting Nautilus’s motion for summary 

judgment of invalidity, which the district court denied on 

June 12, 2012. Biosig timely appeals. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1). 

DISCUSSION

I. 

This court reviews the district court’s grant or denial 

of motions for summary judgment under the law of the 

regional circuit. MicroStrategy Inc. v. Bus. Objects, S.A., 

429 F.3d 1344, 1349 (Fed. Cir. 2005). The Second Circuit 

reviews de novo a district court’s grant of a motion for 

summary judgment. Kuebel v. Black & Decker Inc., 643 

F.3d 352, 358 (2d Cir. 2011). Summary judgment motions 

may be granted only where “there is no genuine dispute 

as to any material fact and the movant is entitled to 

judgment as a matter of law.” Fed. R. Civ. P. 56(a). In 

making this determination, a court must “draw all reasonable inferences in favor of the nonmoving party, and it 

may not make credibility determinations or weigh the 

evidence.” Reeves v. Sanderson Plumbing Prods., Inc., 530 

U.S. 133, 150 (2000). 
10 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

II. 

The sole issue presented to this court is whether the 

district court erred in holding that the asserted claims of 

the ’753 patent is invalid for indefiniteness as a matter of 

law. In particular, the district court held that “spaced 

relationship” as recited in claim 1 and referring to the 

spacing between the common and live electrodes was not 

distinctly and particularly claimed in the patent in violation of 35 U.S.C. § 112, ¶ 2.3 

Indefiniteness is a legal issue this court reviews without deference. Star Scientific, Inc. v. R.J. Reynolds Tobacco Co., 655 F.3d 1364, 1373 (Fed. Cir. 2011) (“Star 

Scientific II”). Section 112, ¶ 2, requires that the specification of a patent “conclude with one or more claims 

particularly pointing out and distinctly claiming the 

subject matter which the applicant regards as his invention.” “Because claims delineate the patentee’s right to 

exclude, the patent statute requires that the scope of the 

claims be sufficiently definite to inform the public of the 

bounds of the protected invention, i.e., what subject 

matter is covered by the exclusive rights of the patent.” 

Halliburton Energy Servs., Inc. v. M-I LLC, 514 F.3d 

1244, 1249 (Fed. Cir. 2008). 

A claim is indefinite only when it is “not amenable to 

construction” or “insolubly ambiguous.” Datamize, LLC v. 

Plumtree Software, Inc., 417 F.3d 1342, 1347 (Fed. Cir. 

2005) (internal quotations and citations omitted). “In and 

of itself, a reduction of the meaning of a claim term into 

words is not dispositive of whether the term is definite . . . 

 3 Paragraph 2 of 35 U.S.C. § 112 was replaced with 

newly designated § 112(b) when § 4(c) of the Leahy–Smith 

America Invents Act (“AIA”), Pub. L. No. 112–29, took 

effect on September 16, 2012. Nevertheless, the pre-AIA 

version of § 112 applies because the ’753 patent issued 

prior to that date. 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 11 

. And if reasonable efforts at claim construction result in 

a definition that does not provide sufficient particularity 

and clarity to inform skilled artisans of the bounds of the 

claim, the claim is insolubly ambiguous and invalid for 

indefiniteness.” Star Scientific, Inc. v. R.J. Reynolds 

Tobacco Co., 537 F.3d 1357, 1371 (Fed. Cir. 2008) (“Star 

Scientific I”) (citations omitted). “Thus, a construed claim 

can be indefinite if the construction remains insolubly 

ambiguous . . . .” Star Scientific II, 655 F.3d at 1373; see 

also Exxon Research & Eng’g Co. v. United States, 265 

F.3d 1371, 1377–79 (Fed. Cir. 2001) (accepting the district 

court’s claim construction and separately undertaking an 

analysis of the claims at issue to determine indefiniteness); Union Pac. Res. Co. v. Chesapeake Energy Corp., 

236 F.3d 684, 689–90, 692 (Fed. Cir. 2001) (same); Minn. 

Min. and Mfg. Co. v. Johnson & Johnson Orthopaedics, 

Inc., 976 F.2d 1559, 1567 (Fed. Cir. 1992) (same). 

General principles of claim construction apply when 

determining indefiniteness. Enzo Biochem, Inc. v. Applera 

Corp., 599 F.3d 1325, 1332–33 (Fed. Cir. 2010). We 

therefore primarily consider the intrinsic evidence consisting of the claim language, the specification, and the 

prosecution history. Id. In addition, similar to claim 

construction, courts may consider certain extrinsic evidence in resolving disputes regarding indefiniteness. 

Exxon Research & Eng’g Co., 265 F.3d at 1376 (citing 

Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1454 (Fed. 

Cir. 1998) (en banc)); see also Verve, LLC v. Crane Cams, 

Inc., 311 F.3d 1116, 1119-20 (Fed. Cir. 2002) (recognizing 

that guidance as to measurement of a term of degree can 

come from the intrinsic record or from the knowledge of a 

person of ordinary skill in the art); Bancorp Servs., L.L.C. 

v. Hartford Life Ins. Co., 359 F.3d 1367, 1375–76 (Fed. 

Cir. 2004) (finding evidence not publicly available at the 

time of the invention may nonetheless be probative to 

show that the term was in use and had a discernible 

meaning to at least some persons practicing in the field). 
12 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

In doing so, the court is not weighing evidence or making 

factual findings, but rather, looking to extrinsic evidence 

as part of the normal course of engaging in construction of 

the patent. Exxon, 265 F.3d at 1376 (citing Cybor, 138 

F.3d at 1454). 

When a “word of degree” is used, the court must determine whether the patent provides “some standard for 

measuring that degree.” Seattle Box Co., Inc. v. Indus. 

Crating & Packing, Inc., 731 F.2d 818, 826 (Fed. Cir. 

1984). Similarly, when a claim limitation is defined in 

“purely functional terms,” a determination of whether the 

limitation is sufficiently definite is “highly dependent on 

context (e.g., the disclosure in the specification and the 

knowledge of a person of ordinary skill in the relevant art 

. . . ).” Halliburton, 514 F.3d at 1255. 

III. 

The disputed term “spaced relationship” does not suffer from indefiniteness. Because the term was amenable 

to construction, indefiniteness here would require a 

showing that a person of ordinary skill would find “spaced 

relationship” to be insolubly ambiguous—that it fails to 

provide sufficient clarity delineating the bounds of the 

claim to one skilled in the art. In this case, a skilled 

artisan would find such boundaries provided in the intrinsic evidence. 

The district court construed “spaced relationship” to 

mean that “there is a defined relationship between the 

live electrode and the common electrode on one side of the 

cylindrical bar and the same or a different defined relationship between the live electrode and the common 

electrode on the other side of the cylindrical bar.” Summ. 

J. Hr’g Tr. 10:16–22. Notwithstanding that this disputed 

term was amenable to construction, the district court 

determined that the term was indefinite. Specifically, the 

district court stated that “a spaced relationship did not 

tell me or anyone what precisely the space should be . . . . 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 13 

Not even any parameters as to what the space should be . 

. . . Nor whether the spaced relationship on the left side 

should be the same as the spaced relationship on the right 

side.” Summ. J. Hr’g Tr. 23:3–11. 

Turning to the intrinsic evidence, the district court is 

correct that the specification of the ’753 patent does not 

specifically define “spaced relationship” with actual 

parameters, e.g., that the space between the live and 

common electrodes is one inch. Nevertheless, the ’753 

patent’s claim language, specification, and the figures 

illustrating the “spaced relationship” between the live and 

common electrodes are telling and provide sufficient 

clarity to skilled artisans as to the bounds of this disputed 

term. For example, on the one hand, the distance between the live electrode and the common electrode cannot 

be greater than the width of a user’s hands because claim 

1 requires the live and common electrodes to independently detect electrical signals at two distinct points of a hand. 

On the other hand, it is not feasible that the distance 

between the live and common electrodes be infinitesimally 

small, effectively merging the live and common electrodes 

into a single electrode with one detection point. See ’753 

patent col. 3 ll. 26–31 (describing how each hand is placed 

over the live and common electrodes so that they are “in 

physical and electrical contact with both electrodes.”). 

Thus, the ’753 patent discloses certain inherent parameters of the claimed apparatus, which to a skilled artisan 

may be sufficient to understand the metes and bounds of 

“spaced relationship.” 

The functionality of the claimed heart rate monitor as 

recited in claim 1, described in the specification, and 

which provided the basis for overcoming the PTO’s office 

action rejections during the reexamination, sheds further 

light on the meaning of “spaced relationship.” Specifically, claim 1 provides, in part: 
14 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

whereby, a first electromyogram signal will be detected between said first live electrode and said 

first common electrode, and a second electromyogram signal, of substantially equal magnitude and 

phase to said first electromyogram signal will be 

detected between said second live electrode and 

said second common electrode; so that, when said 

first electromyogram signal is applied to said first 

terminal and said second electromyogram signal 

is applied to said second terminal, the first and 

second electromyogram signals will be subtracted 

from each other to produce a substantially zero 

electromyogram signal at the output of said difference amplifier . . . . 

’753 patent col. 5 ll. 48–61. This “whereby” clause describes the function of substantially removing EMG 

signals that necessarily follows from the previously recited structure consisting of the elongate member, the live 

electrode, and the common electrode. Id. col. 5 ll. 42–47. 

Importantly, the EMG signal is detected between the live 

and common electrodes, which are in “spaced relationship” with each other. Even more significantly, the PTO 

examiner found this function to be “crucial” as a reason 

for overcoming the cited prior art and confirming the 

patentability of the asserted claims upon reexamination. 

J.A. 139–46. Thus, the recitation of this function in claim 

1 is highly relevant in ascertaining the proper bounds of 

the “spaced relationship” between the live and common 

electrodes. See Hoffer v. Microsoft Corp., 405 F.3d 1326, 

1329 (Fed. Cir. 2005) (per curiam) (“[W]hen the ‘whereby’ 

clause states a condition that is material to patentability, 

it cannot be ignored in order to change the substance of 

the invention.”). 

The specification also describes, in part, the electrodes’ “spaced relationship” in terms of their corresponding function of detecting distinct electrical signals, 

whereby EMG signals are substantially removed in the 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 15 

difference amplifier so that the output of the difference 

amplifier substantially consists only of the ECG signal. 

See, e.g., ’753 patent col. 1 ll. 53–58, col. 2 ll. 12–19. 

According to Biosig, when configuring the claimed heart 

rate monitor, skilled artisans can determine the “spaced 

relationship” between live and common electrodes by 

calculating the point in which EMG signals are substantially removed. 

During reexamination, Biosig presented evidence in 

support of this position in a declaration by the inventor, 

Mr. Gregory Lekhtman, which was submitted in response 

to a PTO office action. See 01 Communique Lab., Inc. v. 

LogMeIn, Inc., 687 F.3d 1292, 1298 (Fed. Cir. 2012) 

(considering statements made during reexamination as 

intrinsic evidence for purposes of claim construction). His 

declaration was based largely on tests he performed to 

show the effects of electrode configuration on EMG signals measured in the palms of the users’ hands. In particular, he represented that the strength of an EMG 

signal measurement is proportional to the space between 

the active and ground electrode and the size of the electrodes. J.A. 194–95. He further declared that it was 

common knowledge for skilled artisans in 1992 that EMG 

potentials on each hand would be different, and that the 

’753 patent requires a configuration of the detectors that 

produce equal EMG signals from the left and right hands. 

J.A. 200. This equalization or balancing, according to Mr. 

Lekhtman, is achieved by detecting EMG signals on the 

left and right palms, which are delivered to a differential 

amplifier in the EMG measuring device. Available design 

variables are then adjusted until the differential output is 

minimized, i.e., close to zero, and the ECG to EMG ratio is 

determined to be sufficient for an accurate heart rate 

determination. J.A. 200–01. Mr. Lekhtman explained 

that some of these design variables in producing a balanced detection of EMG signals include spacing, size, 

shape and materials of the electrodes. Moreover, Mr. 
16 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

Lekhtman represented that a common analog oscilloscope 

available in 1992 would have been used by those skilled in 

the art to measure the signals and to determine the best 

ECG/EMG ratio. J.A. 210–11. 

For comparison, Mr. Lekhtman tested the circuitry as 

recited in the ’753 patent and the circuitry as recited in 

Fujisaki, the prior art cited during reexamination. Mr. 

Lekhtman’s test results indicated that an ECG/EMG ratio 

“in the range of about 3–10 would be manifested at the 

output of the differential amplifier” of the ’753 patent as 

having substantially zero influence from the EMG signal. 

J.A. 213; 343. Conversely, an ECG/EMG ratio of about 1 

or less, as generated by the circuitry claimed in the Fujisaki patent, was found to be masking the ECG signal and 

thus requiring further filtering after the differential 

amplifier. J.A. 213. 

Mr. Lekhtman also described Dr. Henrietta Galiana’s 

test results of a laboratory mock-up of the claimed apparatus—results prepared in the course of the 2004 Action 

at the district court against Nautilus. J.A. 204–05; 1029–

56. Her test results and corresponding report supported 

Mr. Lekhtman’s statements and demonstrated that two 

detected EMG signals on opposite hands can indeed have 

substantially the same amplitude and phase, and that a 

difference amplifier will then reduce those EMG signals to 

substantially zero. J.A. 205; 1048–54. 

Finally, extrinsic evidence underscores the intrinsic 

evidence. In particular, Biosig submitted a declaration of 

yet another expert, Dr. George Yanulis, in support of its 

opposition to Nautilus’s summary judgment motion in the 

underlying district court litigation, which confirmed Mr. 

Lekhtman’s and Dr. Galiana’s test results and reports. 

J.A. 1670. 

In summary, the claims provide inherent parameters 

sufficient for a skilled artisan to understand the bounds of 

“spaced relationship.” In addition, a skilled artisan could 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 17 

apply a test and determine the “spaced relationship” as 

pertaining to the function of substantially removing EMG 

signals. Indeed, the test would have included a standard 

oscilloscope connected to both the inputs and outputs of 

the differential amplifier to view the signal wave forms 

and to measure signal characteristics. With this test, 

configurations could have been determined by analyzing 

the differential amplifier input and output signals for 

detecting EMG and ECG signals and observing the substantial removal of EMG signals from ECG signals while 

simulating an exercise. These parameters constitute the 

metes and bounds of “spaced relationship” as articulated 

in the ’753 patent. Nothing more rigorous is required 

under § 112, ¶ 2. 

The district court nonetheless held Biosig had not articulated with specificity the dimensions or other parameters characterizing the space between the electrodes: “It 

should be half inch, one inch, two inches, three inches. 

What is the space[d] relationship?” Summ. J. Hr’g Tr. 

35:7–8. The district court likewise stated that the ’753 

patent failed to disclose the “composition of the handle” 

and whether the electrodes were “between the two middle 

fingers, the outer first and fourth finger, the thumb 

underneath and the fingers on top? Where is the spaced 

relationship?” Summ. J. Hr’g Tr. 38:16–24. The district 

court also questioned whether having “small” hands as 

opposed to “large” hands would affect the “spaced relationship” between the live and common electrodes. Summ. 

J. Hr’g Tr. 40:2–6. Moreover, the district court found 

nothing in evidence that provided how a skilled artisan 

would have determined the appropriate parameters 

yielding the necessary “spaced relationship” as recited by 

the ’753 patent: “[W]hat [the expert] says is that through 

trial and error, which he doesn’t describe, one can find a 

spaced relationship. That may be. But there’s no description.” Summ. J. Hr’g Tr. 39:6–8. These inquiries however 
18 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

miss the mark in this instance because they do not support an indefiniteness analysis. 

To begin, we have not insisted that claims be plain on 

their face in order to avoid a determination of invalidity 

for indefiniteness. Exxon, 265 F.3d at 1375. “If the meaning of the claim is discernible, even though the task may 

be formidable and the conclusion may be one over which 

reasonable persons will disagree, we have held the claim 

sufficiently clear to avoid invalidity on indefiniteness 

grounds.” Id. In addition, “[p]rovided that the claims are 

enabled, and no undue experimentation is required, the 

fact that some experimentation may be necessary to 

determine the scope of the claims does not render the 

claims indefinite.” Id. at 1379. When relevant values can 

be obtained, § 112 ¶ 2 is satisfied. Marley Mouldings Ltd. 

v. Mikron Indus., Inc., 417 F.3d 1356, 1360–61 (Fed. Cir. 

2005) (“Although the district court was concerned that the 

claims encompass a range of volumes and thereby also of 

weights, § 112 ¶2 is satisfied when the relevant values 

can be ‘calculated or measured.’”) (citation omitted). By 

embracing this standard, “we accord respect to the statutory presumption of patent validity, and we protect the 

inventive contribution of patentees, even when the drafting of their patents has been less than ideal.” Exxon, 265 

F.3d at 1375 (internal citations omitted); see Morton Int’l, 

Inc. v. Cardinal Chem. Co., 5 F.3d 1464, 1470, 1472 (Fed. 

Cir. 1993) (citing 35 U.S.C. § 282). Therefore, objections 

relating to the mere fact that there may be some need for 

experimentation to determine the scope of the claims 

carry little weight. 

Likewise, the district court’s objections to the claims 

as written do not support imprecision of the claims. 

Rather, the objections are based on the premise that the 

’753 patent does not include disclosure sufficiently commensurate with the scope of the claims. These objections, 

if relevant, provide grounds for invalidity under § 112, ¶ 1 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 19 

and not § 112, ¶ 2.4 As this court has explained: 

A patent claim to a fishing pole would not be invalid on indefiniteness grounds if it contained a limitation requiring that the pole be “at least three 

feet long,” even though a 50 foot long fishing pole 

would not be very practical. By the same token, 

there is nothing indefinite about the claim language at issue in this case simply because it covers some embodiments that may be inoperable. 

Exxon, 265 F.3d at 1382; Personalized Media 

Commc’ns, LLC v. Int’l Trade Comm’n, 161 F.3d 696, 706 

(Fed. Cir. 1998) (rejecting expert testimony stating generally that a “digital detector” was not adequately disclosed 

in the patent and could not be built by those of ordinary 

skill as relevant only to the sufficiency of the written 

description to enable the practice of the invention of the 

claims); Miles Labs., Inc., v. Shandon, Inc., 997 F.2d 870, 

875, (Fed. Cir. 1993) (same). Breadth is not indefiniteness. SmithKline Beecham Corp. v. Apotex Corp., 403 F.3d 

1331, 1340–41 (Fed. Cir. 2005). Hence, inquiries as to the 

size of the users’ hands, placement of fingers, and the 

“composition of the handle” may be relevant, if at all, to 

issues that relate to enablement under § 112, ¶ 1, not 

indefiniteness under § 112, ¶ 2, because they are directed 

to the operability of varying embodiments of the claimed 

heart rate monitor, not to the precision of the claims at 

 4 35 U.S.C. § 112, ¶ 1 generally relates to the sufficiency of the written descriptions of patents, including 

enablement, and states in relevant part: “The specification shall contain a written description of the invention, 

and of the manner and process of making and using it, in 

such full, clear, concise, and exact terms as to enable any 

person skilled in the art to which it pertains . . . to make 

and use the same . . . .” 
20 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

issue. Accordingly, these objections do not address the 

inherent parameters set forth in the intrinsic evidence. 

Still, Nautilus seeks support in Halliburton. In Halliburton, the invention at issue was a “fragile gel” that 

was used in drilling. 514 F.3d at 1246–47. This court 

found that the patent-at-issue did not disclose how the 

claimed “fragile gel” performed differently than the disclosed prior art, such as “how much more quickly the gels 

broke when stress was imposed, or how much more quickly the gels reformed when stress was removed.” Halliburton, 514 F.3d at 1253. Halliburton’s failure to distinguish 

the fragileness of the drilling fluids of the invention from 

the close prior art, according to this court, was fatal 

because it did not limit on what was invented beyond the 

prior art. Id. For example, the court noted that the fluids 

of the invention may provide less resistance to shearing 

(i.e., break more quickly) than the prior art fluids, but the 

degree of improved speed, the court said, remained ambiguous. Id. Thus, this court held that it was unclear 

whether a skilled artisan would have interpreted this 

claim as having an upper bound of fragility. Id. 

Halliburton is distinguishable. Here, the claimed 

apparatus has inherent parameters where the “spaced 

relationship” cannot be larger than the width of a user’s 

hand. Additionally, it has been shown that skilled artisans can readily ascertain the bounds of the “spaced 

relationship” through tests using standard equipment. 

Thus, the “upper bound” that was lacking in Halliburton

is found here. As a result, Halliburton fails to support 

Nautilus. 

Rather, this case is analogous to Star Scientific II. 

There, the disputed term was “controlled environment” as 

applied to the practice of tobacco curing and “whether a 

person of ordinary skill would know how to establish a 

controlled environment to perform the claimed method.” 

Star Scientific II, 655 F.3d at 1373-74. This court held 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 21 

that the fact that the patents-at-issue did not give exact 

numbers measuring humidity, temperature, and airflow 

in a conventional curing barn was not dispositive. Id. at 

1374. On the contrary, this court found there was evidence showing that “a person of skill in the art of tobacco 

curing would possess adequate understanding to manipulate these variables to create a controlled environment.” 

Id. Further, because conventional curing varied depending on the conditions for each cure, specific numerical 

values were found not necessary for one skilled in the art 

to implement conventional curing. Id. Hence, “controlled 

environment” was held not insolubly ambiguous. 

Like Star Scientific II, the record shows that the variables here, including the spacing, size, shape, and material affecting the “spaced relationship” between the 

electrodes, can be determined by those skilled in the art. 

Thus, “spaced relationship” cannot be said to be insolubly 

ambiguous. 

IV. 

Contrary to the district court’s decision and to Nautilus’s contention on appeal, this court’s jurisprudence does 

not proscribe drafting or defining claims in relation to 

their functions. Moore U.S.A., Inc. v. Standard Register 

Co., 229 F.3d 1091, 1111 (Fed. Cir. 2000) (“We note that 

there is nothing wrong with defining the dimensions of a 

device in terms of the environment in which it is to be 

used.”); see also Vizio, Inc. v. Int’l Trade Comm’n, 605 

F.3d 1330, 1340 (Fed. Cir. 2010) (“[T]he ‘for decoding’ 

language . . . is properly construed as a limitation, and 

not merely statement of purpose or intended use for the 

invention, because ‘decoding’ is the essence or a fundamental characteristic of the claimed invention.”). That is, 

“claims are not necessarily indefinite for using functional 

language.” Microprocessor Enhancement Corp. v. Texas 

Instruments Inc., 520 F.3d 1367, 1375 (Fed. Cir. 2008). 

Indeed, functional language in a means-plus-function 
22 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

format is explicitly authorized by statute. 35 U.S.C. § 112, 

¶6. Functional language may also be used to limit the 

claims without having the means-plus-function format. 

Microprocessor Enhancement Corp., 520 F.3d at 1375. 

Yet, the district court found the evidence consisting of 

test results and their corresponding references to “substantial removal of EMG signals” conclusory because, 

according to the court, Biosig failed to show how it conducted its tests that allegedly illustrate a “spaced relationship” between the electrodes and the substantial 

removal of EMG signals. In particular, the district court 

found fault with the experts’ references to the function of 

the claim term only, and it ultimately held that “this is all 

a description of the desired result and not a description of 

any invention . . . and, therefore, violates the requirement 

of specificity in Section 112.” Summ. J. Hr’g Tr. 42:25–

43:4. 

Courts often refer to the context in which the patented invention is claimed to ascertain its scope. Medrad, 

Inc. v. MRI Devices Corp., 401 F.3d 1313, 1319 (Fed. Cir. 

2005) (“It is therefore entirely proper to consider the 

functions of an invention in seeking to determine the 

meaning of particular claim language.”). Hence, to determine the proper meaning of “spaced relationship,” we 

must refer to “spaced relationship” in the context of the 

intrinsic evidence, including the claim language, specification, and prosecution history. The district court viewed 

“spaced relationship” in a vacuum by choosing to turn a 

blind eye to the functional aspects of claim 1, e.g., how 

“spaced relationship” contributes to the removal of noise 

signals, such as EMG signals, and the overall capabilities 

of the claimed heart rate monitor. However, without 

context, it would be impossible to ascertain “what the 

inventors actually invented and intended to envelop with 

the claim,” Renishaw PLC v. Marposs Societa’ per Azioni, 

158 F.3d 1243, 1250 (Fed. Cir. 1998), and to examine the 

patent from the perspective of a person skilled in the art, 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS, INC. 23 

e.g., Tegal Corp. v. Tokyo Electron Am., Inc., 257 F.3d 

1331, 1342 (Fed. Cir. 2001). Thus, to the extent the 

district court failed to consider Biosig’s evidence based on 

its reasoning that the evidence spoke only to the “function 

of the claim,” this was error. 

Nautilus makes a related contention that the claims 

at issue are invalid as they impermissibly claim both an 

apparatus and a method of use. Specifically, Nautilus 

contends that claim 1 recites a heart rate monitor and a 

required step that a user holds the monitor. According to 

Nautilus, it is unclear whether the alleged infringement 

occurs when one makes a heart rate monitor having the 

recited structural elements, or whether infringement 

allegedly occurs when the user actually holds the handle 

and contacts the electrodes. This contention is unpersuasive. 

The ’753 patent recites apparatus claims with functional limitations that describe the capability of substantially removing EMG signals. See, e.g., ’753 patent col. 5 l. 

16–col. 6 l. 15. Indeed, claim 1 of the ’753 patent is clearly 

limited to a heart rate monitor possessing the recited 

structure that is capable of substantially removing EMG 

signals. It is not indefinite. Accordingly, this case fails to 

invoke our decision in IPXL Holdings, LLC v. Amazon.com, Inc., 430 F.3d 1377 (Fed. Cir. 2005) (holding 

claims at issue as indefinite because they simultaneously 

claimed an apparatus and method steps). 

CONCLUSION

The only issue on this appeal is the summary judgment of indefiniteness. Other aspects of the defense of 

patent invalidity, although raised in the district court, are 

not before us, and may be considered on remand. We 

reverse the district court’s invalidity determination and 

remand for further proceedings. 

REVERSED AND REMANDED 
United States Court of Appeals 

for the Federal Circuit ______________________ 

BIOSIG INSTRUMENTS, INC.,

Plaintiff-Appellant,

v.

NAUTILUS, INC.,

Defendant-Appellee.

______________________ 

2012-1289

______________________ 

Appeal from the United States District Court for the 

Southern District of New York in No. 10-CV-7722, Judge 

Alvin K. Hellerstein.

______________________ 

SCHALL, Circuit Judge, concurring. 

I join the court’s reversal of the judgment on appeal 

and its remand of the case for further proceedings. I 

write separately, however, because, while I agree with the 

court that the district court erred in holding claims 1 and 

11 of the ’753 patent invalid by reason of indefiniteness, I 

would rest that ruling on a more limited analysis. I 

therefore respectfully concur.

In Part II of the Discussion section of its opinion, the 

court correctly sets forth our law on indefiniteness. In 

short, a claim is indefinite (1) when it is not amenable to 

construction or (2) when, even if it can be construed, “the 

construction remains insolubly ambiguous, meaning it 

fails to provide sufficient clarity [delineating the metes] 
2 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

and bounds of the claim to one of skill in the art,” Star 

Scientific, Inc. v. R.J. Reynolds Tobacco Co., 655 F.3d 

1364, 1373 (Fed. Cir. 2011). See Datamize, LLC v. 

Plumtree Software, Inc., 417 F.3d 1342, 1347 (Fed. Cir. 

2005) (“Only claims ‘not amenable to construction’ or 

‘insolubly ambiguous’ are indefinite.”); see also Star 

Scientific, Inc. v. R.J. Reynolds Tobacco Co., 537 F.3d 

1357, 1371 (Fed. Cir. 2008) (“In and of itself, a reduction 

of the meaning of a claim term into words is not dispositive of whether the term is definite . . . . And if reasonable efforts at claim construction result in a definition that 

does not provide sufficient particularity and clarity to 

inform skilled artisans of the bounds of the claim, the 

claim is insolubly ambiguous and invalid for indefiniteness.”) (internal citations omitted). As the court concludes, neither of these two grounds for indefiniteness 

exists in this case. 

First, the “spaced relationship” limitation plainly was 

amenable to construction. The district court construed 

the two recitations of “in spaced relationship with each 

other” in claim 1 to mean that “there is a defined relationship between the live electrode and the common electrode 

on one side of the cylindrical bar and the same or a different defined relationship between the live electrode and 

the common electrode on the other side of the cylindrical 

bar.” See Biosig Instruments, Inc. v. Nautilus, Inc., No. 

10-cv-7722, slip op. at 3 (S.D.N.Y. Sept. 29, 2011) (Dkt. 

32, “Summary Order Memorializing Court’s Patent Claim 

Term Constructions After a Markman Hearing”). Neither 

Biosig nor Nautilus disputes that the district court did, in 

fact, construe the “spaced relationship” limitation. 

Second, the court’s construction provided sufficient 

clarity to one of skill in the art as to the metes and bounds 

of the “spaced relationship” limitation. Put most simply, 

the district court construed that limitation to require 

“defined relationships,” between the live electrode and the 
 BIOSIG INSTRUMENTS , INC. v. NAUTILUS , INC. 3

common electrode on each side of the cylindrical bar.1 

What that construction means is that, on each side of the 

cylindrical bar, there is a fixed spatial relationship between the live electrode and the common electrode. And 

the court correctly states that the intrinsic evidence 

relating to the ’753 patent “discloses certain inherent 

parameters of the claimed apparatus, which to a skilled 

artisan may be sufficient to understand the metes and 

bounds of ‘spaced relationship’.” See Majority Op. at 13. 

In my view, along with the court’s subsequent rejection of 

Nautilus’s reliance on Halliburton Energy Services, Inc. v. 

M-I LLC, 514 F.3d 1244 (Fed. Cir. 2008); and IPXL Holdings, L.L.C. v. Amazon.com, Inc., 430 F. 3d 1377 (Fed. Cir. 

2005), that is all that is needed to put this case to rest.

My concern with the balance of the court’s analysis is 

that it presumes a functional linkage between the “spaced 

relationship” limitation and the removal of EMG signals. 

In other words, the analysis proceeds as if the “spaced 

relationship” limitation itself—rather than other limitations of claim 1—included a functional requirement to 

remove EMG signals. See Majority Op. at 16–17 (“[A] 

skilled artisan could apply a test and determine the 

‘spaced relationship’ as pertaining to the function of 

substantially removing EMG signals.”); id. at 13 (“The 

functionality of the claimed heart rate monitor as recited 

in claim 1, described in the specification, and which 

provided the basis for overcoming the PTO’s office action 

rejections during reexamination, sheds further light on 

the meaning of ‘spaced relationship.’”). Indeed, the parties to this appeal and the district court seem to presume 

the same. The language of the “spaced relationship” 

1 Although this construction may be seen as broad, 

as the court notes, “[b]readth is not indefiniteness.” See 

Majority Op. at 19 (citing SmithKline Beecham Corp. v. 

Apotex Corp., 403 F.3d 1331, 1340–41 (Fed. Cir. 2005)).

 
4 BIOSIG INSTRUMENTS, INC. v. NAUTILUS, INC. 

limitation, however, does not contain a functional requirement:

a first live electrode and a first common electrode 

mounted on said first half in spaced relationship 

with each other;

a second live electrode and a second common electrode mounted on said second half in spaced relationship with each other

’753 patent col. 5 ll. 28–33. In addition, as seen above, the 

district court’s construction of the “spaced relationship” 

limitation does not include any functional language 

related to the removal of EMG signals, and Nautilus has 

not conditionally cross-appealed that construction. 

In my view, we should not address a functional limitation included neither in the “spaced relationship” limitation itself nor in the district court’s construction of that 

limitation. By allowing the functional limitation of EMG 

removal from elsewhere in claim 1 to color our analysis of 

the definiteness of the “spaced relationship” limitation, it 

seems to me we address an issue that is not currently 

before us.