Appendix — Cordis Corp. v. Cardiac Pacemakers, Inc.

Office-Supreme Court. U.S. |

e.46°8

82-1484 MAR 7 198)

ALEXANOTR 1. 3

No. -

In the

Supreme Court of the United States

Ocrosper Term, 1982

CORDIS CORPORATION,

PETITIONER,

v~.

CARDIAC PACEMAKERS, INC.,

RESPONDENT,

APPENDIX TO

PETITION FOR WRIT OF CERTIORARI TO

THE UNITED STATES COURT OF APPEALS

FOR THE EIGHTH CIRCUIT

Henry D. PAu, Jr.

Kenway & JENNEY

60 State Street

Boston, MA 02109

(617) 227-6300

Attorneys for Petitioner

Blanchard Press, Inc.. Boston, Mass. Law Printers

TABLE OF CONTENTS

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Opinion of the District Court ................0 0000. A-4

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A-l

United States Court of Appeals

7 For the Eighth Circuit P

No. 81-2048

CARDIAC PACEMAKERS, INC.,

APPELLEE,

v.

CORDIS CORPORATION,

APPELLANT.

ON APPEAL FROM THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF MINNESOTA

Before Ross, Circuit Judge,

STEPHENSON, Senior Circuit Judge,

and Van Pett,* Senior District Judge.

Submitted: March 25, 1982

Filed: October 12, 1982

Per CuriaM.

This is a patent case brought by Cardiac Pacemakers, Inc.

(C.P.1.) against Cordis Corporation (Cordis) in the United

States District Court for the District of Minnesota, Fourth

Division. After a trial, the Honorable Edward J. Devitt

entered what is termed a memo opinion and judgment finding

in favor of C.P.I. and against Cordis. Cordis has »ppealed to

this court. We affirm the trial court.

* Robert Van Pelt, Senior District Judge, District of Nebraska, sitting by

designation.

A-2

Involved is the patentability of devices known as cardiac

pacemakers, and particularly of implantable cardiac pace-

makers. Originally involved were patents known as the Keller

patent, U.S. Patent No. 3,557,796; the Terry patent, U.S.

Patent No. 3,805,769; and the Davies patent, U.S. Patent

No, 4,095,603.

The preliminary proceedings are described in Judge Devitt's

memorandum and nothing is gained by repeating here the

history of the parties’ prior litigation. While this case was

pending, the Keller and Davies patents were withdrawn. The

litigation proceeded only as to the Terry patent granted April

23, 1974. The date of the granted invention as determined by

the trial court was July 1, 1970.

Users and others reading the record would recognize this

case as involving in part a pacemaker made by C.P.1. known

as Medtronic and a pacemaker made by Cordis known as

Omnicor. Another major producer of pacemakers, Telec-

tronics, accepted a license from Cordis. This litigation ensued

when C.P.I. introduced its product to the public market

without obtaining such a license.

The issues on appeal are: (1) whether the district court erred

in holding that Herbert Lenzkes was a “prior inventor” of the

invention granted in the Terry patent, whereby his work an-

ticipated that invention; (2) whether the district court erred in

holding that Robert Wingrove, holder of Patent No. 3,833,005

was also a prior inventor of the invention patented by Terry,

whereby his work anticipated Terry’s invention. The claim is

also made that Wingrove never reduced his device to practice

as held by trial court; (3) whether the district court erred in

holding that the invention claimed in Terry was obvious to one

of ordinary skill in the art.

We have considered these assigned errors. We conclude that

little is to be gained from our discussing the details of the Terry

patent or the other patents cited by Judge Devitt in his opinion.

A-3

The facts are largely undisputed. We find Judge Devitt’s

conclusions from the facts are reasonable.

The applicable law is really not in dispute. We are satisfied

with Judge Devitt’s reading and application of what con-

stitutes obviousness. We feel he correctly read and applied the

cases relating to prior art.

It is sufficient to say that we have read the entire record and

believe that Judge Devitt has well analyzed the pacemakers

before him and the patents on which they were based,

together with the issues raised herein. If we started in to detail

the content of each patent, we would, to a great extent,

merely repeat his explanations and findings.

We conclude that his opinion is accurate, scholarly, and

does justice between the litigants. Such a result is the goal of

all litigation.

Upon the basis of the opinion of Judge Edward J. Devitt

filed in this case on September 1, 1981, we affirm.

A true copy.

Attest:

Crerk, U.S. Court or Appeas, Eicutx Circuit.

A-4

Unrrep States District Court

District OF MINNESOTA

Fourtu Diviston

Civ. No, 4-77-427

Carpiac PACEMAKERS, INC.

PLAINTIFF,

v0.

Corpis CorPoRATION,

DEFENDANT.

Haugen & Nikolai, Orrin Haugen, Minneapolis, Minnesota; Allegretti,

Newitt, Witcoff & McAndrews, Ltd., Charles G. Call and Brad Hulbert,

Chicago, Illinois; and Kevin T. O'Malley, St. Paul, Minnesota, attorneys for

plaintiff.

Kenway & Jenney, Henry D. Pahl and Gilbert H. Hennessey, Boston,

Massachusetts; and Williamson, Bains, Moore & Hansen, Malcolm L.

Moore, Minneapolis, Minnesota, attorneys for defendant.

MEMORANDUM & ORDER

This is a patent case involving the patentability of an im-

plantable electronic pacer to control irregular human heart

beats. Three hundred thousand such devices manufactured by

27 different companies are sold world-wide each year. Two of

the principal producers are arraigned in adversary positions

here.

The litigation between these parties commenced when Cor-

dis Corporation (Cordis), a Florida corporation, brought a

claim for patent infringement against Cardiac Pacemakers,

Inc. (CPI), a Minnesota corporation, in the District of

Massachusetts. CPI then commenced this declaratory judg-

ment action against Cordis, and the Massachusetts action was

dismissed for lack of venue.

In the first suit brought by Cordis, CPI was charged with

willfully infringing United States Patents Nos. 3,557,796 to

Keller, et al., and 3,805,769 to Terry et al.

A-5

CPI filed this action, seeking a declaration that the Terry

and Keller Patents are invalid, unenforceable, and not in-

fringed, by reason of prior invention and obviousness under 35

U.S.C. §§ 102 and 103. Cordis counterclaimed, seeking

damages for an injunctive relief against infringement of these

two patents, and United States Patent No. 4,095,603, which in

the interim, had been issued to Davies. CPI replied, asserting

the Davies Patent was invalid, unenforceable, and not in-

fringed.

Upon reissue proceedings instituted by Cordis in the U.S.

Patent and Trademark Office on the Keller Patent, the Patent

Examiner found that the invention defined by claims 1, 2, 6,

7, 9-11, 13 and 14 of the Keller Patent would have been obvi-

ous to a person of ordinary skill at the time the Keller invention

was made. This decision was upheld by the Patent Office

Board of Appeals and the Court of Customs and Patent Ap-

peals. In re Keller, et al., 642 F.2d 413 (C.C.P.A. 1981).

Cordis then amended its counterclaim by withdrawing the

Keller and Davies Patents. On the Terry Patent remains in this

suit.

The issues were tried to the court April 7, 1981 through

April 15, 1981. Briefs have been filed.

The basic issue to be decided is the patentability of the

Cordis device. It is the position of CPI that the invention

claimed by the Terry Patent was previously made by others

and that any difference between it and the prior art was ob-

vious to those having ordinary skill in the art. Because of our

disposition of this issue, there is no need to reach the infringe-

ment issue.

We deal here with a small electronic battery powered device

which is implanted under the skin near and connected to the

heart. Its operation is directed by pulse signals from without

the body by a second device called a “programmer” through

which pulse rate and other changes in implanted pacemaker

may be effected.

A-6

The claims of the patent in suit are capsulized in the abstract

on the face sheet of the January 22, 1973 amended application.

In the implantable cardiac pacer disclosed herein,

various operating parameters are determined or con-

trolled by the information held in a digital storage reister

such as a binary counter. The information so held may be

varied by means of pulse signals transmitted through the

body of a patient within whom the pacer is implanted.

Rate-sensing and count threshold control circuits are pro-

vided to prevent unintended changes in operating

parameters.

A summary and description of the invention is followed by

the listing of nine detailed claims.'

A more simplified statement of the inventions claimed by

Terry is that it is an implantable device with a counter which

can be changed a step at a time by magnetic impulses from

outside the body to adjust the operation of the implanted

device, and also containing a “safety” counter to prevent un-

wanted changes taking place from spurious signals.

A patent is presumed to be valid, and the burden of proving

invalidity rests on the person asserting it. 35 U.S.C. § 282. CPI

has carried this heavy burden, see E.1. DuPont de Nemours v.

Berkley & Co., Inc., 620 F.2d 1247 (8th Cir. 1980), and we

are convinced that the invention claimed by the Terry Patent

is invalid under 35 U.S.C. §§ 102(g) and 103.

' Claim 1, representative of the claims following it, provides:

An implantable cardiac pacer comprising: means for detecting pulse

signals having predetermined characteristics, which pulse signals can be

applied externally of a patient within whom said pacer is adapted to be im-

planted; a first counter interconnected with said detecting means for selec-

tively counting detected pulse signals; a second counter, controlled by said

first counter and also responsive to said pulse signal detecting means for

counting detected pulse signals occurring after the count held by said first

counter reaches a preselected threshold value; a cardiac stimulation pulse

generator having at least one changeable output parameter; and decoding

means interconnected with said counter for controlling said output

parameter in predetermined correspondence with the value of the count held

by said second counter.

A-7

The Terry Patent

As originally filed on May 10, 1971, the application for the

Terry Patent contained seventeen claims reflecting an implan-

table cardiac pacer which included a counter for counting ex-

ternally applied pulses, and means for controlling the

operating parameters of the pacer in response to the count held

in the counter. The application named Cordis employees

Reese S. Terry, Jr. and Gomer L. Davies as co-inventors of the

patented subject matter.

The genesis of the claims contained in the original applica-

tion was a memorandum authored by Gomer Davies on Sep-

tember 21, 1969 and sent to other Cordis personnel. The

memorandum begins, “For various reasons (meeting cov. peti-

tion, providing a more useful device for the patient, etc.) it is

desirable to provide an implantable pacer system (of the stand-

by type) in which the rate can be altered under external con-

trol.” Plaintiff's Exhibit 49 at 701. In discussing approaches to

a method for effecting pacer adjustments, Davies alluded to

the basic programming technique ultimately claimed in the

Terry patent application and incorporated in the Omnicor

pacer marketed by Cordis: “One system. ..comprises a reed

switch in the pacer that is repetitively actuated by an external

magnet to step an internal circuit electrically through a series

of states.” Plaintiff's Exhibit 49 at 703.

This basic programming technique is described in the Lopin

Patent 3,631,860, issued on an application filed October 27,

1969. That patent describes a programmable pacer that can be

externally adjusted through the operation of a monostable

magnetic reed switch as the pulsing element for changing the

state of a counter comprised of electronic circuits which con-

trol the rate of the pacer.

Cordis cited the Lopin Patent to the Patent Office and ob-

tained more narrow claims. The Terry patent application was

amended by cancelling nine of the seventeen claims. Cordis

stated in its amended application that the remaining claims

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defined an invention over Lopin. The remaining claims were

directed to « protection circuit in the pacer designed to pre-

vent alteration of the set operating parameters of the pacer by

spurious magnetic signals.

Timing of the Terry Invention

Cordis argues that the date of conception for the invention

claimed in the Terry Patent is September 20, 1969, the date of

the Davies memorandum and that the Lopin Patent is thus

unavailable as a prior art reference. We disagree.

The Davies memorandum did not describe or discuss means

for preventing inadvertent programming of interference. It

merely acknowledges “the rather sticky problem of external

excitation of such circuits.” Plaintiff's Exhibit 49 at 704. It

goes on to state “Pulsed RF signals come naturally to mind,

but the circuitry that could receive such signals could also re-

spond to high-level interference.” Id.

Cordis concedes that the claimed invention as a whole was

not conceived until July i, 1970, the date of a drawing by

Reese Terry of the device which included the safety counter.

The July 1, 1970 drawing was made in response to a request by

Cordis President Dr. Murphy to develop an externally pro-

grammable pacer. Within several weeks of that request, Reese

Terry made the July 1, 1970 drawing relating to external non-

invasive programming.

The concept of using an address code to prevent an acciden-

tal reed switch closure from affecting the program circuit was

originated by Terry. This code was designed to prevent

reprogramming unless a grouping of eight magnetic pulses

were received by the pacer. The concept of the address code is

claimed in the Terry Patent.

We hold that the earliest date of conception of invention

claimed in the Terry Patent is July 1, 1970. It was not until

that date that the entire conception was complete:

The conception of an invention consists in the complete

performance of the mental part of the inventive act. All

A-9

that remains to be accomplished in order to perfect the

act or instrument belongs to the department of construc-

tion, not invention. It is, therefore, the formation in the

mind of the inventor of a definite and permanent idea of

the complete and operative invention as it is thereafter to

be applied in practice that constitutes an available con-

ception within the meaning of the patent law.

Rex Chainbelt Inc. v. Borg-Warner Corporation, 477 F.2d

481, 491 (7th Cir. 1973) quoting, Mergenthaler v. Scudder,

D.C. Cir., 11 App. D.C. 264 (1897). Davies’ mere identifica-

tion of the problem presented by outside interference with

programming of the pacer, particularly in light of the fact that

the prevention of accidental reprogramming constitutes an

essential part of the invention, is fatal to Cordis’ position that

the Davies memorandum is the conception of the claimed in-

vention described in the Terry Patent. See id. at 491-92.

Accordingly, the Lopin Patent is available as a prior art

reference.

Validity of the Terry Patent

CPI presented extensive expert testimony concerning the

scope and content of the prior art, the level of ordinary skill in

the art as of July 1, 1970, and the differences between the prior

art and the Terry Patent claims. CPI’s expert, Leroy Prohov-

sky, is an electrical engineer with extensive experience in

microelectronics and circuit design techniques. We find that

Prohovsky, by virtue of his skill, training, and experience was

well qualified to testify on this subject. Cordis declined to call

an expert witness to rebut Prohovsky’s testimony (Trial

Transcript, 711-12). In so doing, we reject Cordis’ contention

that the scope of the prior art be limited to biomedical implan-

table stimulators. The scope of the pertinent art in this in-

stance includes the field of electrical engineering in general,

and more specifically, the use of both digital and analog cir-

cuitry. This finding is consistent with the principle that the

concept of the scope of the art must be afforded a wide

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latitude. See, e.g., Cathodic Protection Service v. American

Smelting and Refining Company, 594 F.2d 499 (5th Cir.

1979), see also, Skee-Trainer Inc. v. Garelick Mfg. Co., 361

F.2d 895 (8th Cir. 1966).

Lenzkes Patent

Prior to July 1, 1970, the Huntington Institute of Applied

Medical Research (“HIAMR”) of Pasadena, California, and

General Dynamics Corporation of Pomona, California, col-

laborated in the development of an implantable, digital, pro-

grammable biostimulator later called the “Telestimulator.”

HIAMR was founded by Drs. Robert Pudenz and C. Hunter

Sheldon for the purpose of engaging in neurologial research.

HIAMR pioneered the implantation of electronic devices for

nerve stimulation in the treatment of neurological disorders.

The inventor of the Telestimulator, H. H. Lenzkes of

General Dynamics Corporation, prepared a report dated

February 4, 1970, entitled “A Preliminary Concept for a

Versatile Implantable Bi-Directional Nerve Stimulator.” At

that point, the Telestimulator had been “breadboarded”, and

the feasibility of the system confirmed. On May 13, 1970

Lenzkes reported in writing that the Telestimulator had been

constructed by personnel of General Dynamics. That report

contained a detailed description of the design organization of

the Telestimulator. With the exception of some differences not

relevant here, the report of May 13, 1970 parallels the descrip-

tion of the Telestimulator found in the United States Patent

No. 3,727,616, issued to Lenzkes. This report also indicated

that the device had been breadboarded using COS/MOS

devices manufactured by RCA Company. According to

Lenzkes’ testimony, the breadboarded design functioned

satisfactorily. In a Progress Repor+ dated June 23, 1970,

Lenzkes indicated that the device had been built in the

laboratory and p:oof of the concept had been verified.

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In October 1970 the first prototype of the Telestimulator

was delivered to HIAMR. HIAMR personnel implanted it in a

cat for testing purposes on or about November 23, 1970.

The Lenzkes Patent was filed subsequent to the Terry ap-

plication. The evidence shows, however, that the Telestimu-

lator was fully built and successfully tested prior to July 1,

1970. We find that these facts establish that the Telestimulator

was actually reduced to practice prior to July 1, 1970, thus en-

titling it to priority under 35 U.S.C. § 102(g).

While the Telestimulator was being developed HIAMR and

General Dynamics disclosed details of the project to outside

persons. On August 6, 1970, personnel from Medtronic, Inc.

visited General Dynamics and discussed the Telestimulator

with Dr. Pudenz and General Dynamics personnel.

At the Neurological Society Conference held March 5, 1971

in San Antonio, Texas. Dr. Pudenz and E. L. Watkins

delivered a detailed presentation regarding the Telestimu-

lator. This conference was attended by Dr. Tarjan, a Cordis

Vice President, who later informed Reese Terry, Gomer

Davies, Cordis President Dr. Murphy about the Telestimu-

lator work.

In September 1971 Dr. Murphy visited HIAMR and ob-

served an experiment utilizing a cat to demonstrate nerve

stimulation. He was also furnished with a detailed technical

report entitled “Continued Development of the Sheldon/-

Pudenz Biostimulator,” which explained the operation of the

telestimulator.

Based on the foregoing facts, we hold that the

Telestimulator work later described in the Lenzkes Patent was

not “abandoned, suppressed or concealed” within the meaning

of 35 U.S.C. § 102(g).

Plaintiff's expert Mr. Prohovsky testifed at length in present-

ing a comparison of the Telestimulator work and the claims set

forth in the Terry Patent. The Telestimulator system described

in the Lenzkes Patent, and in particular Figure 6 of that

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patent, incorporated an implantable stimulator including cir-

cuits 48 and 130 for receiving pulses of radio frequency (RF)

energy transmitted through the skin from an external

transmitter. The Lenzkes design utilizes a 21 bit shift register

(132) which corresponds to the Terry counter 31.

Data is entered into the shift register-type counter 132

which ultimately functions as a memory for storing the re-

ceived pulses. The Lenzkes design further includes a stimula-

tion decoder 136 which comprises a second counter having

three separate states. Decoder 136 corresponds to the Terry

Counter 43. Controlling the entry of data into the first counter

132 and the second counter 136 is a Mode Logic Circuit 134.

When power to the transmitter is turned on, a memory preset

signal is applied to the first counter 132 to set all of its stages to

a zero state. As the external transmitter feeds RF impulses into

the receiver circuits 48 and 130, the Mode Logic Circuit 134

initially causes the pulses to be fed into the 21-bit shift register

132. The leading bit in the string of serial data entering the

21-bit counter following “power-up” is forced to be a binary

“1” signal and this signal is called the “data completion pulse.”

Following the application of 21 clock signals which are

counted by the counter (shift register) 132, the “data com-

pletion pulse” exits from the shift register 132 and is applied to

the Mode Logic Circuit 134. This causes the Mode Logic Cir-

cuit to block further data entries into the counter 132 and the

subsequently received pulses are instead routed to the 3-state

counter 136. The contents of the counter 136, in turn, deter-

mine the pulse width and the polarity of the stimulating pulse

to be applied to the electrodes 52 and 54.

Prohovsky provided the court with comprehensive and

credible testimony comparing the Terry claims with the

Lenzkes design. His testimony fully supports the claim com-

parison chart, plaintiff's exhibit 60, which compels the conclu-

sion that the Telestimulator fully anticipated claims 2, 7 and 8

of the Terry Patent under 35 U.S.C. § 102(g).

A-13

Prohovsky also explained the differences between the Terry

claims and the Telestimulator. These differences include the

use of a RF transmission signal to convey pulse information

from the external transmitter in the Telestimulator, as

opposed to the use of magnetic field to activate a magnetic

reed switch in the Terry Patent. There is no switch debounce

circuit in the Telestimulator because, with the use of the RF

transmission system, it does not include any switch that re-

quires “debouncing.” The debounce circuit would have been

necessary in the Telestimulator only if it had employed a

magnetic reed switch. Another difference cited is that Counter

31 of the Terry Patent is reset when the reed switch is not

receiving pulses at a sufficiently high rate. Shift register 132 is

reset upon the application of power to the Telestimulator, Pro-

hovsky credibly and fully identified all differences between the

Telestimulator and the Terry Patent in compiling the claim

comparison chart. His testimony in this regard is relevant to

the consideration of the issue of obviousness under 35 U.S.C.

§ 103. That matter will be considered more fully below.

The Wingrove Work

Robert Wingrove, an employee of Medtronic, Inc. from

1958 through 1972, testified regarding his development of a

digital, programmable implantable cardiac pacer during

1970, This pacer included a protection circuit for preventing

accidental reprogramming of the pacer by spurious noises in

the external environment.

Wingrove began development of the pacer in 1970, working

with new integrated circuit devices called complementary

metal oxide semi-conductor (“CMOS”) circuits. These circuits

were well suited to use in implantable pacers because of their

switching characteristics and low power consumption.

Wingrove testified that the devce he developed, as reflected

in certain documents dated March 2, 1970 and March 13, 1970

was actually built and sent to a Dr. Chardack for implementa-

tion in a dog.

A-14

The first prototype of the Wingrove pacer is dated March

25, 1970. This device was actually built and tested. Another

prototype was built and tested on or about May 27, 1970.

Wingrove, like others, recognized the need for a safety cir-

cuit to prevent accidental reprogramming of the pacer. To this

end he developed a technique that utilized an ID pulse of a

certain width which had to be presented to the implanted unit

in order to open a gate to allow reprogramming.

A patent application for the Wingrove device was filed on

July 26, 1971. Patent 3,833,005 was issued and is substantially

identical to the “Third Prototype” drawings of May 27, 1970.

In the Wingrove design, the external transmitter sends a

predetermined number of RF pulses to the implanted unit.

Wingrove chose the parameters of the time frame within

which the pulses had to be received with the aim of preventing

noise frequencies encountered in nature from meeting the con-

ditions. Thus the RF pulses had to persist for longer than 11

milliseconds, but not more than 14 milliseconds. The lower

time threshold is established in resistor 22 and capacitor 26 in

decoder 20 as found in Figure 1 of the Wingrove patent. The

higher time threshold is determined by resistor 31 and

capacitor 27. If the proper RF pulses are received, NOR gate

29 is activated, allowing counter 40 to be reset. Counter 40

which corresponds to the Terry counter 43 determines the rate

at which stimulating pulses will be emitted implantable pulse

generator 100.

While decoder 20, which functions as the safety circuit, is

not a counter, it operates in much the same manner. In order

for the RF pulses to persist for the required length of time, it is

necessary that the implanted unit receive a predetermined

number of RF pulses. The use of RF pulses of a predetermined

width in order to enable counter 40 to be reset is substantially

equivalent to the use of digital counter 31 in the Terry Patent.

The difference between these are such that they would be

obvious to one with ordinary skill in the art.

A-15

Mr. Prohovsky compared the Terry claims with the prior

Wingrove work. He testified that Wingrove anticipates all

nine claims of the Terry patent. We conclude that the

Wingrove work does in fact anticipate the claims in the Terry

Patent.

Obviousness

Even had the Terry Patent claims not been anticipated

within the meaning of 35 U.S.C. § 102(g), we find that the dif-

ferences between the prior art and the subject matter of the

Terry Patent as a whole would have been clearly obvious to

one with ordinary skill in the art of electrical engineering.

In reaching this conclusion, we have considered the scope

and content of the prior art, including the Lozin Patent, the

Telestimulator, the prior Wingrove work, and the Chardack,

Bowers and Keller Patents. Prior reductions to practice under

35 U.S.C. § 102(g) are properly considered in making a deter-

mination of obviousness under 35 U.S.C. § 103. Sutter Prod-

ucts Co. v. Pettibone Mulliken Corp., 428 F.2d 639 (7th Cir.

1970).

The Lopin Patent, the Telestimulator, and the Wingrove

work are discussed above.

United States Patent No. 3,198,195, issued to Chardack,

was filed on October 18, 1962. It claims an invasive needlelike

device for changing the operating parameters of a pacer after

implantation.

United States Patent No. 3,311,111, issued to Bowers, filed

on August 11, 1964, and assigned to General Electric, discloses

a controllable electric body tissue stimulator incorporating

bistable switches, such as magnetic reed switches that may be

actuated by an auxiliary magnetic field applied externally to

the body. The reed switches are used to externally adjust the

operation of the device.

The Keller Patent discloses a digitally timed pacer using a

clock source and a frequency dividing chain to achieve timing.

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The need for a safety circuit when using externally pro-

grammable implantable devices is elementary. The work of

Lenzkes and Wingrove demonstrate the obviousness of the

solution to the problem of inadvertent reprogramming. The

differences in the prior art between the designs and means of

preventing such inadvertent reprogramming are insubstantial.

Because of the clear obviousness to the person of ordinary skill

of the differences between the subject matter claimed by the

Terry patent and the prior art, we need not consider secondary

factors such as long felt need, commercial success, and the

like. See Cathodic Protection Service v. American Smelting &

Refining Company, 594 F.2d at 513; Centsable Products, Inc.

v. Lemelson, 591 F.2d 400, 403-04 (7th Cir. 1979).

Based on all of the above findings with reference to the

Lopin Patent, the Telestimulator, the Wingrove work, and the

Chardack, Bowers, and Keller Patents, we conclude that the

differences between the Terry Patent and the prior art would

have been obvious to one with ordinary skill in the art.

Accordingly, we declare that Terry Patent 3,805,796 is in-

valid, and that said patent is not infringed by plaintiff because

of the making, selling, or using of any apparatus made, sold or

used by plaintiff. Plaintiff's claim for attorney's fees and costs

is DENIED.

Let judgment be entered accordingly.

Dated: August 31, 1981.

(s) Epwarp J. Devirr

Epwarp J. Devitt, Senior Judge

United States District Court

A-17

35 U.S.C. 102

“A person shall be entitled to a patent unless—

(a)

(b)

(c)

(d)

(e)

(t)

(g)

the invention was known or used by others in this

country, or patented or described in a printed

publication in this or a foreign country, before the

invention thereof by the applicant for patent, or

the invention was patented or described in a printed

publication in this or a foreign country or in public

use or on sale in this country, more than one year

prior to the date of the application for patent in the

United States, or

he has abandoned the invention, or

the invention was first patented or caused to be

patented by the applicant or his legal representatives

or assigns in a foreign country prior to the date of the

application for patent in this country on an applica-

tion filed more than twelve months before the filing

of the application in the United States, or

the invention was described in a patent granted on an

application for patent by another filed in the United

states before the invention thereof by the applicant

for patent, or

he did ot himself invent the subject matter sought to

be patented, or

before the applicant’s invention thereof the invention

was made in this country by another who had not

abandoned, suppressed, or concealed it. In determin-

ing priority of invention there shall be considered not

only the respective dates of conception and reduction

to practice of the invention, but also the reasonable

diligence of one who was first to conceive and last to

reduce the practice, from a time prior to conception

by the other.”

A-18

35 U.S.C. 103

Conditions for patentability; non-obviousness subject matter.

“A patent may not be obtained though the invention is

not identically disclosed or described as set forth in sec-

tion 102 of this title, if the differences between the subject

matter sought to be patented and the prior art are such

that the subject matter as a whole would have been obvi-

ous at the time the invention was made to a person having

ordinary skill in the art to which said subject matter per-

tains. Patentability shall not be negatived by the manner

in which the invention was made.”

A-19

United States Patent

Terry, Jr. et al.

(19)

(11) 3,805,796

(45) Apr. 23, 1974

(54) IMPLANTABLE CARDIAC PACER HAVING

ADJUSTABLE OPERATING PARAMETERS

Inventors: Reese S. Terry, Jr., Miami; Gomer

on Fort Lauderdale, both of

Assignee: Cordis Corporation, Miami, Fla.

Filed: Jan. 22, 1973

Appl. No.: 325,334

Related U.S. Application Data

Continuation of Ser. No. 141,694, May 10, 1971,

abandoned.

{75}

(73)

(22)

[21]

[63]

(52)

(51)

[58]

PUPP PPP)

AGin 1/36

128/419 C, 419 B, 419 E,

128/419 P, 419 R, 422, 423

References Cited

UNITED STATES PATENTS

1/1972 Lopin

[56]

3,631,860 128/419 P

POORER RE EERE HERE HERRERO EES

i ae

3.301001 BURST MON siiiciedciannscieiias . 128/419 P

Primary Examiner—William E. Kamm

Attorney, Agent, or Firm—Kenway, Jenney & Hildreth

[57] ABSTRACT

In the implantable cardiac pacer disclosed herein, var-

ious Operating parameters are determined or con-

trolled by the information held in a digital storage reg-

ister such as a binary counter. The information so held

may be varied by means of pulse signals transmitted

through the body of a patient within whom the pacer

is implanted. Rate-sensing and count threshold control

circuits are provided to prevent unintended changes in

Operating parameters.

9 Claims, 1 Drawing Figure

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TER / DECODER} RESET

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T "

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37 “) aire Se a

| BINARY COUNTER | RESET me

ee a oe eee

39 | | Reaiineliean

ILATERAL

Sy a witen . &

eeewewewe RI7 cs: 5

Ra

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+V O Melyeydanre—aaa

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’

3,805,796

A-20

PATENTED APR 23 1974

INVENTORS

S

et Yong

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HOLIMS

Zivtig avn ~s!

Narre 5, Terry , rent

Dowsr bk. Davros,

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A-21

3,805,796

1

IMPLANTABLE CARDIAC PACER HAVING

ADJUSTABLE OPERATING PARAMETERS

This is a continuation of application Ser. No. 141,694

filed May 10, 1971, now abondoned.

BACKGROUND OF THE INVENTION

This invention relates to fully implantable prosthetic

or therapeutic devices and more particularly to cardiac

pacers in which various operating parameters may be

adjusted or varied without surgically obtaining access

to the pacer itself.

Various means have been proposed for altering the

operating parameters of an implanted cardiac pacer

without requiring surgery as such. For example, it has

been proposed to utilize needle-like adjusting tools to

select resistance values and to use bistable magnetic

reed switches for performing various switching func-

tions. However, each of these prior art adjustment

means has heretofore typically been rather limited ir,

application. A serious drawback in most of these prior

art systems is that the range of adjustment or the num-

ber of adjustments which can be made is highly lim-

ited. Further, there may be a problem in retaining the

desired value after the adjustment procedure per se is

complete. In the case of bistable magnetic reed

switches, transient magnetic fields may cause the

switch to reverse state. The switch will then remain in

that state indefinitely and thereby cause an undesired

mode of operation. In the case of needle-like adjusting

tools, the danger of infection due to penetrating the pa-

tient's epidermis remains even though that danger is re-

duced by the needle-like character of the tool.

Among the several objects of the present invention

may be noted that provision of apparatus which permits

the adjustment or variation of several operating param-

eters of an implanted prosthetic device such as a car-

diac pacer without requiring surgical access to the de-

vice; the provision of such apparatus in which a param-

eter may be adjusted over a wide range and to any one

of a wide variety of preselected values within the range;

the provision of such apparatus in which predeter-

mined combinations of different operating parameters

may be selected simultaneously; the provision of such

a system which provides for the reliable storage of the

parameter-determining information; the provision of

such apparatus which is relatively immune to electrical

noise and transient magnetic fields; and the provision

of such apparatus which is highly reliable and which is

relatively simple and inexpensive. Other objects and

features will be in part apparent and in part pointed out

hereinafter.

SUMMARY OF THE INVENTION

Briefly, an implantable pacer constructed in accor-

dance with the present invention employs means for

detecting pulse signals having predetermined charac-

teristics which are applied externally of a patient within

whom the pacer is implanted. A counter is intercon-

nected with the detecting means and is advanced by the

detected pulse signals. A cardiac stimulation pulse gen-

erator is provided in which at least one output parame-

ter is adjustable. Decoding means are interconnected

between the counter and the pulse generator for setting

5

—

a

20

35

40

45

$5

2

means of pulse signals applied externally of the patient.

BRIEF DESCRIPTION OF THE DRAWING

The single drawing is a schematic block diagram of

an implantable cardiac pacer having operating parame-

ters which are adjustable in accordance with the pres-

ent invention.

DESCRIPTION OF THE PREFERRED

EMBODIMENT

Referring now to the drawing, an essentially conven-

ty nal cardiac stimulation pulse-generating circuit is in-

dicated generally at 11. Appropriate supply potentials

are provided as indicated. An NPN transistor Ql and

a PNP transistor Q2 are interconnected in a so-called

complementary-symmetry type of relaxation oscillator.

The voltage at the base terminal of PNP transistor Q2

is controlled by a voltage divider comprising resistors

R12 and R14, this voltage being filtered by a capacitor

C4 with the filter source impedance being determined

by a resistor R11.

The collector of transistor Q2 is connected to the

base of transistor QI through a capacitor C5 and a re-

sistor R17 connected in series therewith. As will be un-

derstood by those skilled in the art, this connection

provides regenerative feedback during the pulse output

portion of the oscillator's cycle of operation. The oscil-

lator output signal, taken from the collector of transis-

tor Q2, is applied, through a pair of resistors R15 and

R16, to the base terminal of an NPN output transistor

Q3. This transistor is normally biased off by means of

a resistor R13. The collector terminal of output transis-

tor Q3 is provided with a load resistor R10 and is cou-

pled, through a capacitor C3, to the pacer output ter-

minal 13. As is understood, the output terminal 13 will

be coupled to a patient's cardiac tissue through an ap-

propriate lead system, as is conventional. The lead sys-

tem also establishes a common ground potential. The

output circuit is protected by a zener diode Z1 in con-

ventional manner.

As is understood, the repetition rate of the comple-

mentary symmetry oscillator depends upon the bias

current provided to the base terminal of transistor Q1.

This current serves to re-charge the capacitor 5 be-

tween output pulses. This bias current is provided from

the positive supply voltage through a series of timing

resistors R4-R8 which are graded in value according to

a predetermined sequence. Selected ones of the resis-

tors R4-R8 inay be shunted by the operation of a quad-

bilateral switch 15. As will be understood by those

skilled in the use of integrated circuits in digital appli-

cations, the quadbilateral switch 15 will typically com-

prise a plurality of active semiconductor elements

formed in a single semiconducting wafer or chip. How-

ever, for the purpose of facilitating the description of

the present invention, the switching function per-

formed by this circuitry is conveniently represented in

the drawing by four conventional switch symbols. Each

such switch is under the control of a respective input

signal, as indicated. As will be understood, 16 values of

total series resistance may be obtained by closing the

65 individual switches in various combinations. Corre-

spondingly, 16 different pulse repetition rates will be

available from the oscillator comprising transistors Q1

cordingly, the output parameter may be adjusted by and Q2.

A-22

3,805,796

3

The junction between resistors R15 and R16 can se-

lectively be shunted to ground through a resistor R9

and a semiconductor switch or gate 17. Again, this

function is indicated by a conventional switch symbol

although semiconductor switching elements are pre-

ferred in actual practice. The operation of the switch

is under the control of a respective input signal, as indi-

cated. When the gate or switch 17 is closed, a portion

of the drive or output current from the oscillator tran-

sistors Ol and Q2 is shunted away from the base circuit

of the output transistor Q3 through resistor R9. The

stimulation pulse output current is correspondingly re-

duced. Thus, the gate 17 provides a means for selecting

between two output current levels. In other words,

means are provided for adjusting the value of a second

operating parameter of the stimulation pulse generat-

ing circuitry. Since the number of available states dou-

ble with each further stage added to the binary counter,

it can be seen that the number of combinations of sev-

eral different parameters may easily be expanded. For

example, selected count bits may be used to control

whether the pacer operates in a synchronous or non-

synchronous mode or in a standby or continuous mode.

in accordance with the present invention, the pulse

repetition rate and the output current of this stimula-

tion pulse generator 11 may be adjusted or controlled

while the pacer is implanted, without surgically enter-

ing the patient's body. In the embodiment illustrated,

pulse signals for transmitting the information used in

determining these output parameters is transmitted

into the patient's body by means of a magnetic field

which is sensed by a magnetic reed switch 21. Reed

switch 21 is interconnected with the positive supply so

as to provide a source of input pulses to one of the

input terminals of a NOR gate 23. This input terminal

is normally biased negatively through a resistor R1. The

output signal from NOR gate 23 is coupled, through a

capacitor C1, to both input terminals of a second NOR

gate 25, which thus functions as an inverter. These

input terminals are normally biased in the positive

sense through a resistor R2. The output signal from

NOR gate 25 is, in turn, applied back to the other input

terminal of the first NOR gate 23.

As will be understood by those skilled in the art, this

interconnection of the NOR gates 23 and 25 provides

the mode of operation of a one-shot multivibrator. The

time constant or period of the multivibrator is deter-

mined by the relative values of capacitor C1 and resis-

tor R2 and is selected so as to provide, for each trigger-

ing pulse, a square-wave output pulse of longer dura-

tion than any contact bounce which might be expected

from the magnetic reed switch 21. This operation thus

provides a pulse shaping so that the resultant electrical

pulse signals are suitable for use with digital circuitry

in conventional manner.

While magnetic pulse signals are presently preferred

as a method of communicating information to the im-

planted device, other types of signals, appropriately se-

lected to avoid interference from ambient interference,

may also be used. For example, bursts of acoustic en-

ergy at preselected frequency can be transmitted

through tissue and detected. Likewise, bursts of elec-

15

20

25

35

40

45

50

$$

4

they can penetrate a shield around the implanted de-

vice which would protect the circuitry from high fre-

quency transients which might affect the logic cir-

cuitry.

The pulse signals obtained from the multivibrator are

applied, through a diode D1, to a timing capacitor C2

which is shunted by a resistor R3, The voltage on ca-

pacitor C2 is, in turn, applied to an inverting gate 27.

Gate 27 functions essentially as a voltage threshold de-

vice, the output signal from gate 27 being positive or a

digital “one,” except when the voltage on cz pacitor C2

is above a predetermined voltage level or threshold

which is the level of actuation of the gate. Together

with the capacitor C2 and resistor R3, gate 27 thus op-

erates as a rate detector. When pulses from the one-

shot multivibrator are applied through diode D1 to ca-

pacitor C2 so as to re-charge that capacitor faster than

it is discharged by the resistor R3, the output signal

from gate 27 will remain negative so as to constitute a

logic “zero.”

The output signal from gate 27 is applied as a reset

signal to a decade counter 31. Decade counter 31 is as-

sumed to be of the integrated digital circuit type having

an integral decoder so that separate output signals cor-

responding respectively to each of the ten successive

states of the counter are available without external ma-

trixing. In the embodiment illustrated, only the “6" and

“7” output signals are utilized.

The shaped input pulses obtained from the one-shot

multivibrator are applied to the input terminal of

counter 31, through a NOR gate 35. The “7” output

signal from the decade counter 31 is applied as a sec-

ond input to NOR gate 35 so as to selectively control

the application of these input pulses. As will be under-

stood, this connection will allow the counter to count

up to its seventh state. At this point, the 7" output sig-

nal becomes a digital ‘‘one."’ Accordingly, the output

signal from gate 35 will be held at a digital “zero” and

further counting is prevented.

The “7” signal from the decade counter 31 is also ap-

plied, through an inverting gate 37, to a NOR gate 39.

NOR gate 39 is connected so as to control the applica-

tion of the input pulses, obtained from the one-shot

multivibrator, to a binary counter 43. Since the “7” sig-

nal from the decade counter 31 is inverted prior to its

application to the NOR gate 39, it will be seen that the

binary counter 43 is inhibited from counting until the

decade counter 31 reaches its seventh state. The "6"

output signal from the decade counter 31 is applied as

the reset signal to the binary counter 43.

Thus, when the decade counter 31 passes through its

sixth state, the binary counter 43 will be reset. Then,

when the decimal counter 31 reaches its seventh state,

it will stop counting and the binary counter 43 will

begin to count upwards from its reset or “zero™ state

in response to any pulse input signals applied thereto by

the multivibrator circuit.

ss pelinad ab top. tee. damage gta 9 oy

signal being provided each stage. The output

nals from the first four stages, i.c., the “1,” “2,” by

and “8” signals, are applied to control the quad-

bilateral switch 15. Thus, the value of the repetition

resistance will be a function of the

rate-controlling

tromagnetic energy at relatively low r.f. frequencies ,. count held by the first four stages of binary counter 43.

can be detected and used to advance the counters or © The “16” output signal from binary counter 43, i.e., the

registers of the present invention. Relatively low rf.

frequencies, ¢.g., 15-150 kHz, have the advantage that

signal from the fifth stage, controls the gate 17 which.

as noted previously, affects the output current level of

A-23

3,805,796

5

the stimulation pulse-generating circuit 11. The

counter 43 has 32 possible states, 16 in which the “16”

signal is a logic one" and 16 in which that signal is a

logic “zero.” Accordingly, it will be seen that any of the

16 different pulse repetition rates can be provided at

either of the two output current levels. In other words,

there are 32 output parameter combinations which can

be applied to the stimulation pulse generator 11 and

the selection of which of these 32 exists at any one time

is under the control of the count accumulated in the bi-

nary counter 43.

Summary of Operation

Briefly then, the operation of the embodiment illus-

trated is as follows. The output parameters of the stim-

ulation pulse generator 11 are determined in corre-

spondence with the count held in the binary counter

43. The existing parameter values persist until the

counter 43 is set to some different value. Pulse signals

for changing the count held in counter 43 are intro-

duced by applying. through the patient's body, bursts

or trains of magnetic pulses which will actuate the mag-

netic reed switch 21. Each operation of the reed switch

triggers the one-shot multivibrator comprising gates 23

and 25 so that a squarewave pulse, suitable for use with

digital circuitry, is generated. If successive pulses fol-

low at a rate which is within the time constant deter-

mined by capacitor C2 and resistor R3, the gate 27 re-

sets the counter 31 and this counter begins to count the

shaped input pulses. After the counter 31 receives six

of the succeeding pulses, the binary counter 43 is reset.

When the decade counter reaches its seventh state, it

is stopped from further counting and subsequent

shaped input pulses are applied to the binary counter

43 so that this counter is then advanced from its initial

or all “zero"’ state. The total length of the pulse train

is selected so that the new count introduced into the bi-

nary counter 43 corresponds to that state of the

counter which will produce the desired output parame-

ters, i.e., through the quadbilateral switch 15 and the

gate 17. For example, if it is desired to set the stimula-

tion pulse generator output parameters to values corre-

sponding to the seventh state of the binary counter 43,

the applied pulse train should produce fifteen actua-

tions of the magnetic reed switch 21. The first actua-

tion causes the gate 27 to release the reset signal from

the counter 31, the next seven counts advance the de-

cade counter 31 and the last seven counts advance the

binary counter 43 to the desired state. Since magnetic

reed switches can operate at frequencies of several

hundred Hz and the digital counting circuitry will oper-

ate much faster, a complete resetting cycle can be ac-

complished in less than a typical heartbeat period. If

even faster parameter resetting is sought, semi-

conductor magnetic or electric sensing devices may be

used.

In addition to providing timed resetting of the output

control counter 43, the count threshold established by

the decade counter 31 also provides the additional de-

sirable function of establishing a count threshold which

must be exceeded before any change in output parame-

ter will be effected. Thus, a short burst of electrical

noise pulses which might find their way into the cir-

cuitry at the proper repetition rate to actuate the rate-

sensitive circuitry, still would not typically advance the

counter 31 sufficiently far to erase the output parame-

ter information previously stored in the binary counter

20

25

30

35

45

$5

6

43. Accordingly, a very high degree of noise immunity

is provided.

Apparatus in accordance with the embodiment illus

trated was constructed using components having the

values and/or manufacturer's part designation as given

in the following table and this apparatus operated in the

manner described.

TABLE

Ohms

RI 100,000

R2 1,000,000

R3 1,000,000

R4 176,000

RS 232,000

R6 $64,000

R7? 1,024,000

RS 1,863,000

RO 10,000

R10 27.000

Ril 5,000

R12 2,200,006

R13 22,000

R14 3,300,000

RIS 10,000

R16 10,000

R17 1,000

Microfarads

cl 0.0047

c2 0.047

c3 47

c4 0.1

cs 0.22

NOR Gates RCA CD 4001

23, 25, 35 and 39

Bocade Counter RCA CD 4017

Binary Counter RCA CD 4004

Quad Bilateral Switch RCA CD 4016

Gates 27, 37 and 17 RCA CD 4007

With regard to the inverting gates 27 and 37, it may

be noted that these gates, in the RCA integrated circuit

designated, are in fact pairs of separable field-effect

transistors on the same chip and a remaining one of the

transistors on the same integrated circuit chip is em-

ployed as the switching gate 17. While this particular

embodiment was made up using commercially avail-

able integrated circuit devices, it should be understood

that essentially the same circuitry can be formed as a

single special purpose integrated circuit using so-called

large scale integrated circuit (LSI) techniques, as can

other embodiments falling within the scope of the ap-

pended claims. The particular integrated circuits desig-

nated are of the complementary MOSFET ( metal oxide

semiconductor, field-effect transistor) type. An advan-

tage of this type of circuitry in implantable stimulation

devices is that the logic gates employed draw very little

current except in actual switching and thus average

current drain is very low.

While the parameter-controlling apparatus of the

present invention has been illustrated in conjunction

with stimulation pulse generating circuitry using analog

timing and output current control, it should be under-

stood that, the functional parameters of other types of

stimulation pulse-generating circuitry may also be con-

trolled in accordance with the count held in a digital

storage register such as the binary counter 43. For ex-

ample, apparatus of the present invention might also be

used in conjunction with a digitally timed implantable

cardiac pacer, ¢.g., of the type disclosed in U.S. Pat.

gs No. 3,557,796 Keller et al. Similarly, the operating pa-

rameters of other types of tissue stimulators, e.g., blad-

der, phrenic nerve, or carotid sinus, may also be con-

trolled in accordance with the present invention.

7

In view of the foregoing, it may be seen that several

objects of the present invention are achieved and other

advantageous results have been attained.

As various changes could be made in the above con-

structions without departing from the scope of the in-

vention, it should be understood that all matter con-

tained in the above description or shown in the accom-

panying drawings shall be interpreted as illustrative and

not in a limiting sense.

What is claimed is:

1. An implantable cardiac pacer comprising:

means for detecting pulse signals having predeter-

mined characteristics, which pulse signals can be

applied externally of a patient within whom said

pacer is adapted to be implanted;

a first counter interconnected with said detecting

means for selectively counting detected pulse sig-

nals;

a second counter, controlled by said first counter and

also responsive to said pulse signal detecting means

for counting detected pulse signals occurring after

the count held by said first counter reaches a prese-

lected threshold value;

a cardiac stimulation pulse generator having at least

one changeable output parameter; and

decoding means interconnected with said second

counter for controlling said output parameter in

predetermined correspondence with the value of

the count held by said second counter.

2. In a fully implantable therapeutic device providing

an electrically controlled physiological function, appa-

ratus for adjusting the operating parameters of the de-

vice while implanted, said apparatus comprising:

means for detecting pulse signals having predeter-

mined characteristics, which pulse signals can be

applied externally of a patient within whom said

device is adapted to be implanted;

a first counter interconnected with said detecting

means for selectively counting detected pulse sig-

nals;

a second counter, controlled by said first counter and

also responsive to said pulse signal detecting means

for counting detected pulse signals occurring after

the count held by said first counter reaches a prese-

lected threshold value;

decoding means interconnecting with said second

counter for controlling operating parameters of

said device in accordance with the count held by

said second counter; and

means for resetting said first counter if no pulse sig-

nals are received for a predetermined period.

3. In a fully implantable device for automatically pro-

viding an electrically controlled physiological function,

apparatus for adjusting the operating parameters of the

device while the device is implanted, said apparatus

comprising:

a magnetically operable switch for detecting mag-

netic pulse signals, which pulse signals can be ap-

plied externally of a patient within whom said de-

vice is adapted to be implanted;

a first counter interconnected with said switch for se-

lectively counting operations of said switch;

means for resetting said first counter if no pulse sig-

nals are received for a preselected period;

a second counter, controlled by said first counter and

selectively responsive to

switch;

A-24

3,805,796

b)

10

15

20

25

30

35

40

45

$0

$5

8

means controlled by said first counter for resetting

said second counter when the count held by said

first counter reaches a preselected threshold level

and for subsequently enabling said second counter

to count switch operations; and

decoding means interconnected with said second

counter for controlling the operating parameters of

said device in accordance with the count held by

said second counter.

4. A device as set forth in claim 3 including a one-

shot multivibrator which is triggered by the operation

of said switch and which generates square-wave output

pulses of predetermined duration, said counters being

responsive to the multivibrator output pulse to count

operations of said switch.

5. A device as set forth in claim 3 wherein said first

and second counters comprise complementary MOS-

FET integrated logic circuits.

6. An implantable cardiac pacer comprising:

a magnetically operable switch for detecting mag-

netic pulse signals, which pulse signals can be ap-

plied externally of a patient within whom said

pacer is adapted to be implanted;

a first counter interconnected with said switch for se-

lectively counting operations of said switch;

means for resetting said first counter if no pulse sig-

nals are received for a preselected period;

a second counter, controlled by said first counter and

selectively responsive to the operation of said

switch;

means controlled by said first counter for resetting

said second counter when the count held by said

first counter reaches a preselected threshold level

and for subsequently enabling said second counter

to count switch operations;

a cardiac stimulation pulse generator having at least

one adjustable output parameter; and

means interconnected with said second counter for

setting said output parameter to a value corre-

sponding to the count held by said second counter.

7. In a fully implantable device for providing an elec-

trically controlled physiological function, apparatus for

adjusting the operating parameters of the device while

the device is implanted, said apparatus comprising:

means for detecting pulse signals having predeter-

mined characteristics, which pulse signals can be

applied externally of a patient within whom said

device is adapted to be impianted;

means responsive to a first predetermined grouping

of detected pulse signals for providing a control sig-

nal.

a parameter control register having a multiplicity of

States;

means for controlling the operating parameters of

said device in accordance with the existing state of

said control register; and

means responsive to said control signal for changing

the state of said register in accordance with prede-

termined of detected pulse signals fol-

lowing said first grouping of pulse signals, thereby

to vary the operating parameters of said device.

8. In a fully implantable device for automatically pro-

viding electrical stimulation of tissue, apparatus for ad-

the operation of said _—justing the operating parameters of the device while the

device is implanted, said apparatus comprising:

A-25

3,805,796

9 10

means for detecting pulse signals having predeter- said control counter; and

mined characteristics, which pulse signals can be means enabled by said control signal fo. au — zing

roi gemecte Hee & or elle nga whom said the state of said control counter in response to de-

vice is adapt mpranted, tected pulse signals following said first sequence of

means including a counter responsive to a first prede- 5 pulse signals, thereby to vary the operating param-

termined sequence of detected pulse signals for euere of enld devies.

providing a control signal; 9. Apparatus as set forth in claim 8 wherein said con-

parameter control counter having a multiplicity of

: sequential states; K aiid trol counter is responsive to said control signal and is

means for controlling the operating parameters of jo reset thereby to a preselected state.

said device in accordance with the existing state of oe ee

20

25

w

35

40

45

55

65

United States Patent 119

A-26

Lenzkes

uu 3,727,616

(43) Apr. 17, 1973

(54)

ELECTRONIC SYSTEM FOR THE

STIMULATION OF BIOLOGICAL

SYSTEMS

3,662,758 3/1972 Glover

128/419 E

Primary Examiner—William E. Kamm

Attorney —Edward B. Johnson

. (75) Inventor: Herbert H. Lenzkes, Pomona, Calif.

[73] Assignee: General Dynamics Corporation, Po- (S7] ABSTRACT ;

mona, Calif. A receiver totally implanted within a living body is in-

{22} Filed: June 15, 1971 ductively coupled by two associated receiving coils to

a physically unattached external transmitter which

[21] Appl. No.: 153,316 ' transmits two signals of different frequencies to the

receiver via two associated transmitting coils. One of

4 the signals from the transmitter provides the im-

on oy iv, re a planted receiver with precise control or stimulating

{58} Field of Search 128/419 C, 419 E, signals which are demodulated and processed in a

128/419 P 4I9R “$20. 421 422 423. ZA: signal processor network in the receiver and then used

: elas ia tg eee 340/184 by the body for stimulation of a nerve, for example,

. while the other signal provides the receiver with a

continuous wave power signal which is rectified in the

{56} References Cited receiver to provide a source of electrical operating

UNITED STATES PATENTS power for the receiver circuitry without need for an

implanted battery.

3,236,240 8 2/1966 Bradley 128/419 E

3,195,540 7/1965 Waller 128/419 P 9 Claims, 13 Drawing Figures

3,646,940 3/1972 Timm et ai...... 128/419 E

(argent, RECEWER

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3,727,616

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ELECTRONIC SYSTEM FOR THE STIMULATION verted to a digital format part of which is transmitted to

OF BIOLOGICAL SYSTEMS the receiver as a 2)-bit Amplitude Data Word. This in-

BACKGROUND OF THE INVENTION

This invention is directed to means for providing a

precisely controlled bipolar current pulse of given

polarity, magnitude and duration to a living body for

controlling pain, permitting movement of paralyzed ex-

tremities, controlling spasticity, stimulating paralyzed

urinary bladders and preventing atrophy, in clinical ap-

plications and foe functional and behavioral changes in

neurophysiological applications, for example. The

system of the invention utilizes a pulse position modu-

lation technique for electrically stimulating biological

systems such as nerves, for example, in 4 manner which

presently does not exist. The resviiing stimulation out-

put is a constant current biphasic or monophasic signal.

_ Because of the digital nature of the inventive system,

accurate and reliable current stimulating levels are

achieved with fast rise and fail times. Safety features

have been included in the system to prevent extraneous

stimulation due to interfering signals. When the im-

planted receiver is not activated by the external trans-

mitter, any extraneous signals are shunted by a low im-

' pedance path in the receiver.

The inventive system is essentially digital in nature,

whereas known systems in the prior art employ analog

techniques. In addition, the prior art systems employ

pulse width modulation in which the resulting pulsed

radio frequency signal is detected and filtered-to obtain

a stimulation waveform. This prior art method, while

simple in nature, has many limitations. For example, it

cannot provide a precisely controlled amplitude

because of its dependency on the coupling coefficient

between a primary tuned circuit and a secondary tuned

circuit, it cannot provide a biphasic stimulation

waveform nor can it generate a direct current stimula-

tion. In addition, its unipolar pulses are not rectangular

‘because an exponential discharge circuit is normally

employed. Stimulators of the prior art are designed for

specific applications and lack the parameter versatility

and safety that can be achieved with the inventive

system.

SUMMARY OF THE INVENTION

The system of the present invention includes a trans-

mitter that is inductively coupled by two transmitting

coils to a receiver located totally within a living body.

The system of the present invention is sometimes called

a “Biostimulator™ and at other times a“ Telestimulator’

*. The transmitter, which is located outside the body,

transmits two signals of different frequencies to the

receiver via the two transmitting coils. The dual

frequency link of the system provides the implanted

receiver with control signals or operating information

and also a signal from which the receiver can extract its

electrical operating power. The receiver basically com-

prises two receiving coils, a signal processor and a

power supply. The output of the receiver is coupled to

two electrodes via very small electrical wires which

may be attached to a nerve, for example, to stimulate

the nerve or to block it. The desired stimulating pulse

characteristics such as amplitudes, width, interpulse,

periods, etc., are initially entered into the control panel

of the transmitter via suitable switches such as rotary

thumbwheel switches, for example. These data are con-

20

23

30

35

45

50

65

formation is received, decoded and stored by the signal

processor portion of the receiver to provide the proper

amplitude reference to stimulate the nerve. The

remaining portion of the data which has been previ-

ously entered into the transmitter is sent to the receiver

as a series of Stimulation Words. Each of the Stimula-

tion Words comprises three 5S-microsecond radio

frequency (r-f) pulses at substantially 27.12 MHz. The

time spacing between the pulses determines the time

duration of the various parts of the stimulating

waveform. Each word operates in real-time to al-

ternately stimulate the nerve with a positive amplitude,

a negative amplitude and a zero amplitude. The trans-

mitter also provides a substantially 100 KHz continu-

ous wave power signal which is inductively coupled

into the power supply coil in the receiver and rectified

to provide electrical power for the receiver circuitry.

The power signal is always present whenever the sytem

is in use.

Therefore, it is an object of this invention to provide |

an electronic system for the stimulation of biological

systems in a living body in the form of an implantable

receiver capable of providing proper stimulation whea

used in conjunction with an external transmitter.

Another object of this invention is to provide an elec-

tronic system for the stimulation of biological systems

in a living body in which no internal batteries are util-

ized nor any direct wire connections into the body are

made.

It is a further object of this invention to provide a

stimulator system for a living body wherein a dual

frequency external transmitter provides’ inductively

coupled control and power signals to a compatible

receiver located within the living body.

Other objects and features of the invention, as well as

the many. advantages thereof, will be readily apparent

to those skilled in the art from a consideration of the

following written description and accompanying

drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified functional block diagram illus-

trating the overall system involved in the present inven-

tion.

FIG. 2 is a dimensioned view of an encapsulated em-

bodiment of the implantable receiver of the system.

FIG. 3 is a diagrammatic showing of the receiver of

FIG. 2 implanted in an arm and an embodiment of an

associated transmitter.

FIG. 4 is a functional block diagram of the trans-

mitter shown in FIG. 3.

FIGS. Sa-Sh show electrical waveforms available

from the transmitter as stimulation words and the

resulting stimulating currents.

FIG. 6 is a functional block diagram of the recei

shown in FIG. 2.

DESCRIPTION OF THE PREFERRED

EMBODIMENT

Referring now to the drawings, and more particularly

to FIG. 1, there is shown a simplified functional block

diagram of the overall system which includes a trans-

mitter 10, which may be of the laboratory type, for ex-

.

A-33

3,727,616

3

ample, externally located with respect to the outer sur-

face of a skin portion 12 of a living body (not shown).

Stimulating and operational information data for

operation of the transmitter 10 are listed in FIG. 1. A

100 KHz analog channel network 14 in transmitter 10

provides a substantially 100 KHz continuous wave

power signal té a capacitor 16 and a coil or inductor 18

which comprise a substantially 100 KHz series resonant

circuit 20. The coil 18 acts as a transmitting antenna. A

27.12 MHz analog channel network 22 in transmitter

10 provides pulsed radio frequency data at substan-

tially 27.12 MHz to aycapacitor 24 and a coil or induc-

tor 26 which comprise a substantially 27.12 MHz paral-

lel resonant circuit 28. The coil 26 acts as a trans-

mitting antenna. Coupled to the 100 KHz analog chan-

nel network 14 and to the 27.12 MHz analog channel

network 22 by connecting leads A, B and C is a trans-

mitter logic network 29 which processes the stimulat-

ing and operational information data listed in FIG. 1.

In practice, the capacitor 16 in the resonant circuit

20 (being relatively large in size) is physically located

with the other components of the 100 KHz analog

channel network 14, whereas the inductor 18 of the

resonant circuit 28 together with the inductor 26 and

capacitor 24 of the resonant circuit 28 are encased ina

suitable protective housing and as a unit, the combina-

tion is sometimes cailed “the transmitter probe”. Each

of the circuits encased in the “probe" is preferably con-

nected to its respective channel by a coaxial cable (not

shown).

As a point of interest, the simple resonant circuit 28

could be changed, if desired, to a preloaded, tapped

resonant circuit wherein a resistor is connected in

parallel with the inductor 26 and two series capacitors

are. connected in parallel with the resistor/inductor

combination. The center conductor of the appropriate

coaxial cable would be connected between the two se-

ries capacitors.

The particular frequencies chosen for the preferred

embodiment are by way of exampie only, and it is well

understood by those skilled in the art that other

frequency combinations as authorized by FCC regula-

tions may be substituted.

Positioned completely underneath the skin portion

12 is an implantable receiver 30 which includes a coil

or inductor 32 connected in parallel with a capacitor

34 which comprise a 100 KHz parallel resonant circuit

_ 36. The inductor 32 acts as a receiving antenna to

receive the inductively coupled 100 KHz power signal

from the inductor 18 of the resonant circuit 20. The

received power signal is rectified and regulated in a

power supply circuit 38 to provide electrical power of

the proper potential for the implanted electronics via

conductors 40, 42 and the reference ground 41. A coil

or inductor 44 is connected in parallel with a capacitor

46 and comprise a 27.12 MHz parallel resonant circuit

48. The coil 44 acts as a receiving antenna to receive

the inductively coupled 27.12 MHz control or operat-

ing information signal from the coil 26 of the resonant

circuit 28. The received control signal is processed in a

signal processor network 50 the output of which is con-

nected via male interconnect conductors 52, 54 and

very small wires to a nerve 56, for example. in describ-

ing the preferred embodiment of the present invention,

nerve stimulation has been chosen as one example only

25

30

35

45

$0

4

of the many uses thereof, and it will be readily un-

derstood by those skilled in the art that the present in-

vention can be used in many clinical and neu-

rophysiological applications.

Utilization of microelectronic fabrication techniques

during the past few years has resulted in an electronic

packaging science wherein many complex electronic

circuits can be condensed into smail packages. As an il-

lustration of the science of microminiaturization, FIG.

2 shows the dimensions of an actual size example of the

receiver 30 of the present invention contained in a 0.25

inch thick circular package of 1.25 inch diameter. This

small size allows utilization of the receiver 30 in most

parts of the human body. In the example of FIG. 2, the

implantable receiver 30 is contained in a hermetically

sealed all-ceramic package which is encapsulated with

medical-grade silicone rubber 58, for example, to

reduce the possibility of body contamination and rejec-

tion. The majority of the electronic circuitry is con-

tained on two circular ceramic substrates (not shown).

This circuitry generally consists of thick film resistors,

chip capacitors, and various semiconductor chips and

interconnections. The power supply coil 32 of the

receiver 30 is concentrically wound on the outer edge

area of a ceramic circular coil form (not shown) which

also serves as a housing for the two circular substrates.

The signal coil 44 is printed on the outside portion of

one of the circular substrates which also acts as acover .

for one end of the unit. The male interconnectors 52,

54 are imbedded in the power supply coil form to pro-

vide mechanical integrity. The all-ceramic package is

extremely rugged and will survive in very adverse en-

vironments. The implantable receive 30 is surgically

placed within a desired body area as shown in FIG. 3

and is preferably affixed to the nearest bone structure.

In FIG. 3, the receiver 30 is affixed to the humerus 60

of an arm 62 by using synthetic materials similar to

those used for bone repair, for example, and the

receiver Output interconnectors 52, 54 are connected

to a nerve 64 via very small electrical wires (not

shown). In practice, the free ends of two electrical con-

ductors (not showa) having female connectors on the

other ends are attached to the nerve to be stimulated.

The female connectors are then slipped over the male

interconnectors 52 and 54. Also shown in FIG. 3 is an

example of the transmitter 10 with its output cabling

66, preferably two coaxial cables, and the encased

transmitter “probe™ in a housing 68. The transmitter

coils 18, 26 in the “probe” housing 68 are wound ©

similarly to receiving coils 32, 44 on a circular coil

form of on individual coil forms and are protectively

encased or encapsulated in a strong plastic material, for

example. Stimulation of the nerve 64 is achieved by

placing the trancmuter coils 18, 26 contained in the

housing 68 approximately, for example, one-half inch

near, or actually on, the skin portion closest to the im-

planted receiver 30 so the receiver coils 32, 44 can

easily receive the transmitted signals and then activate

the transmitter. The operating instructions listed in

FIG. 1 are entered into the transmitter 10 prior to

stimulation via suitable switches as shown in FIG. 3 in

which actual values are depicted to illustrate an exem-

plary operational setup. Also shown in the FIG. 3 ex-

ample of a transmitter are the switches listed in FIG. 1.

A-34

3,727,616

5

Two major problems must he considered in the

design and fabrication of devices to be implanted in a

living body. These two major problems involve the

selection of enclosure and connector materials. The

body fluids present a rather formidable challenge to the

enclosure or cover for an implantable device because

of their corrosive action. Materials that provide long-

term protection to the device's electronics and that are

compatible with the body chemistry are: ceramic, glass,

synthetic resinous materials and some metals such as

surgical-grade stainiess steel and platinum, for exam-

ple. The qualities that make an all-ceramic package a

highly desirable choice for implantable devices include:

mechanical strength, electrical isolation, resistance to

body fluids, adequate thermal! conductivity, compati-

bility with hybrid technology and low cost. All connec-

tors must be small and reliable and must also be com-

patible with the body fluids. The conductors used for

the nerve stimulator described herein are made of 29

stainless steel but could also be made of platinum, gold,

silver and tantalum or allovs of these metals, for exam-

ple. Encapsulating materials should be electrically insu-

lating, inert, non-toxic, non-irritating and sterilizable.

In addition to the silicone rubber 58, other examples of 25

encapsulant materials are: silastic resins, vinyl chloride,

acrylic polymers, polystyrene, tetrafluorocthylene

polymers and the like.

Referring now to FIG. 4, there is shown a functional

block diagram of the transmitter 10. The stimulating

word(s) and operational information data shown in

FIG. 1 are again included in FIG. 4. The analog portion

of the transmitter consists of two channels, one at 100

KHz and the other at 27.12 MHz, which are func-

tionally identical. The 27.12 MHz analog channel net-

work 22 comprises an oscillator 70 connected through

a series switch 72 to a power amplifier 74. The 100

KHz analog channel network 14 comprises an oscilla-

tor 76 connected through a series switch 78 to a power

amplifier 80. The connecting leads A, 8 and C to the

transmitter logic network 29 are shown. Lead A is con-

nected to the output of the 100 KHz oscillator 76, load

B is connected to an input of the 100 KHz series switch

78 and lead C connects to an input of the 27.12 series

switch 72. Each of the power amplifiers 74, 80 is

preferably connected to its respective resonant circuit

28, 28 via a coaxial cable as discussed hereinabove. In

each channel, the series switch gates the signal from the

45

appropriate oscillator to the amplifier as a function of $0

the controlling logic. The 100 KHz oscillator 76 is also

used to develop all of the timing functions required by

the digital portion of the receiver 30 to be described

hereinafter.

Connected to the 100 KHz series switch 78 is an out-

put of a program logic circuit 84 in the transmitter logic

network 29 to which is coupled a full decoder network

88. A time duration counter circuit 86 is connected to

the counter full decoder network 38. Another output of

the program logic circuit 84 is connected to a data re-

gister 90, a data decoder 92 and a mode logic circuit

94, The output of the data register 90 is connected to

the data decoder 92 which is coupled to a summing net-

work or junction 96 as is a 5-microsecond stimulation

trigger output of the mode logic circuit 94. The mode

logic circuit 94 is additionally coupled to a multiplexer

63

6

vides a presetting signal. The output of the stimulating

counter 112 is connected to a counter full decoder cir-

cuit 114 whose output ts fed back to the mode logic cir-

cuit 94. A digital frequency divider 116 is connected to

the output of the 100 KHz oscillator to feed clock

signals of 0.1 Hz and 10 KHz, for example, as required

to selected circuits such as the time duration counter

86 and to the stimulating counter 112, respectively. A

power supply 118, operating from a 60 Hz power

source, provides all of the operating voltages for the

transmitter.

Prior to activating the transmitter, the operating in-

structions listed in FIGS. 1 and 4 are entered into the

transmitter via suitable switches such as the rotary

thumbwheel and selector switches shown in FIG. 3.

The transmitter converts this information into a digital

sequence of words that are transmitted to the im-

planted receiver 30 at the appropmiate time. The trans-

mitter 10 is activated by the A-C Power Switch which

supplies the +5 volts and =15 volts to the appropriate

electronics via the power suppiy 118. No signals are

transmitted from the transmitter at this time When the

Stimulate Switch is activated, the 100 KHz series

switch 78 is immediately closed which causes the 100

KHz power signal to be inductively coupled to the reso-

nant circuit 36 in the receiver. No 27.12 MHz signal is

transmitted yet because the preset memory pulse of the

receiver has just been activated by the power supply 38

and it must be allowed to decay to insure proper recep-

tion. Approximately ane millisecond after activation of

the Stimulate Switch, the program logic circuit 84 ena-

bles the data register 90 and the data decoder 92 which

operate together to read the Data Completion Pulse (1

bit), the Positive Amplitude (10 bits) and the Negative

Amplitude (10 bits) that have deen previously entered

into the éransmitter: connect these data into binary bits

where a low state or “0" is $ microseconds in width and

a high state or “1° in $0 microseconds in width; and en-

code this information onto a 27.12 MHz c-f signal by

turning on the 27.12 MHz series switch 72 as required.

This 21-bit pulse width modulated Amplitude Data

Word is then serially transmitted to the receiver 30

only once.

The program logic circuit 84 permanently inhibits

the data register 90 and the data decoder 92 after the

21-bit Amplitude Data Word has been transmitted and

it also enables the mode logic circuit 94. The mode

logic circuit 94 momentarily presets the stimulating

counter 112 via the multiplexer 98 to a count value

specified by the Positive Pulse Duration. The 10 KHz

clock signal from the digital frequency divider 116 now

Causes the stimulating counter 112 to increase its count

until it is full. This state is sensed by the counter full

decoder 114 which causes the mode logic circuit 94 to

momentarily preset the stimulating counter 112 via the

multiplexer 98 to a count value specified by the Nega-

tive Pulse Duration. The foregoing sequence is auto-

matically repeated, with the Interpulse Duration, the

Positive Pulse Duration and the Negative Pulse Dura-

tion, etc., being used to preset the stimulating counter

112. Each time the stimulating counter 112 is reset by

the mode iogic circuit 94, a S-microsecond pulse is

generated by, the mode logic circuit 94 which gates the

27.12 MHz series switch 72 through the summing junc-

tion 96 to generate another bit of the 3-bit Stimulating

Pen eS enerine commer S02 eh eee ae Word.

A-35

3,727,616

7

The Pulse Mode Selector Switch allows the user to

determine which one of the five stimulating signals

shown in FIGS. 56, c,d. f and A should be used to stimu-

late the nerve. From the basic Stimulation Word, the

user can select either a bipolar pulse, unipolar positive

pulse, or unipolar negative pulse stimulation via the

Pulse Mode Selector Switch, depending upon the nega-

tive and positive amplitudes that have been entered

into the transmitter via the data register 90. The “+DC"*

* mode modifies the operation of the mode logic circuit

94 by inhibiting its recycling operation after the initial

presetting of the stimulating counter 112; thus only the

“ON+"'D bit of the stimulation word is transmitted as

shown in FIG. Se. The “—DC"™ mode modifies the mode

logic circuit 94 in a similac manner except that only the

“ON+"'b pulse (at zero microamperes positive am-

plitude) and the “ON—" pulse are transmitted before

the mode logic circuit 94 recycling operation is in-

hibited.

- The Time Mode Selector Switch for the Program

Logic Circuit 84 determines the time duration that the

nerve will be stimulated. The Single Cycle mode selec-

tion will allow the transmitter to transmit only one

Stimulation Word. Selection of the Program mode will

allow stimulation to occur only for the Program Time

Duration which has previously been entered into the

transmitter through the time duration counter 86. The

method of operation is functionally identical to that of

the stimulating counter 112 and its associated counter

full decoder 114, with the 0.1 Hz clock signal used in

lieu ofthe 10 KHz clock signal. The Continuous mode

selection via the Time Mode Selector Switch will allow

stimulation to continue uninterrupted until the Stimu-

late Switch is deactivated. : ;

Stimulation of the nerve will cease whenever the

Stimulate Switch is deactivated and the Stimulation

Word is completed. This function is performed auto-

matically when the Time Mode Selector Switch is in

either the Single Cycie mode or the Continuous mode.

Deactivation of the Stimulate Switch will shut off the

100 KHz power signal as soon as the Stimulation Word

has been completed.

Several different types of transmitters may be used

with the implantable receiver 30. Selection will depend

upon the particular need. The laboratory transmitter

shown in FIG. 4 and described hereinabove would be

used by professional personnel in hospitals, clinics and

doctors’ offices to collect experimental and diagnostic

data and to determine the fixed program parameters to

be prescribed for the patient's personal pre-pro-

‘grammed transmitter. The pre-programmed trans-

mitter is available in at least two other configurations:

the bedside transmitter and the portabie transmitter.

Both versions are functionally identical to the laborato- .

fy transmitter except that the operating instructions

such as stimulating levels, polarities, time durations,

etc., discussed hereinabove. will be pre-programmed.

The bedside transmitter will ordinarily use conven-

tional 115V a-c power for its operation whereas the

portable unit will be battery operated.

' The receiver 30 provides a basic bipolar constant

current waveform to the nerve from which four other

stimulating modes can be externally selected. Utilizing

the circuitry described herein, the time duration of any

polarity pulse can be varied in real-time from 20

microseconds to 10 seconds in 10 microsecond inter-

5

20

25

30

35

45

50

vals. The positive and negative amplitudes of these cur-

rent pulses can be externally selected from 0 microam-

peres to 4 milliamperes in 10 microamperes intervals,

A pulse repetition of 0.03 Hz to 16.7 KHz can be ob-

tained, for example. The shape of the current pulses

will generally always be rectangular, having a 0 to 90

percent rise and fall ume of less than 3 microseconds.

As previously expressed hereinabove, five types of

stimulating signals may be applied to a nerve, for exam-

ple. Referring again to FIGS. Sa-5Sh, the basic bipolar

waveform available from the receiver 30 is shown at 5b.

This corresponds to the basic stimulation word shown

at Sa. By setting either the negative or positive polarity

to 0 microampere, a positive unipolar current pulse Se

or a negative unipolar current pulse Sd can be ob-

tained. A programmable steadystate current level of

either polarity can also be generated from either

unipolar current pulse by extending the time duration

of the current pulse as shown at Sf and Sh. The stimula-

tion currents shown at Sf and Sh correspond to the DC

stimulation words shown at Se and 5g, respectively.

The receiver 30 can be divided into two major sec-

tions: the power supply circuit 38 and the signal proces-

sor network 50. The function of the power supply cir-

cuit 38 is to generate the required electrical power for

the implanted electronics and to provide two control

signals to the signal processor network 50. The 100

KHz tuned center-tapped coil 32 is used as the secon-

dary of the power double-tuned coupling circuit 20, 36

to develop the 100 KHz power signal. This signal is

rectified, filtered, and regulated to provide stable

operating voltages for the electronics. The Memory

Preset and Safety Release control signals are generated

from the supply voltages to preset the memory circuit

and release the safety shunt circuit, respectively. These

latter circuits will be more fully explained’ hereinafter.

The function of the signal processor network 50 is to

receive, demodulate, and process all operational in-

structions that are sent from the transmitter 10 and to

generate with the aid of the power supply the proper

stimulating amplitude, polarity and time duration

signal. The 27.12 MHz tuned coil 44 is used as a secon-

dary of the signal doubletuned coupling circuit 28, 48

to develop the instructions that were sent from the

transmitter. The first 21 bits of instructions is the Am-

plitude Data Word which is demodulated and stored in

the receiver memory circuit. All remaining bits are

considered as stimulation instructions and are demodu-

lated and decoded as such. These stimulation instruc-

tions select either the Negative Amplitude Word or the

Positive Amplitude Word or neither word from the

receiver memory circuit. The selected amplitude word,

if selected, is converted to an analog signal which con-

trols the inverting constant current amplifier. This am-

plifier then forces the proper constant current signal

through the nerve and will be more fully discussed

hereinafter.

Referring now to FIG. 6, the receiver 30 is shown as

comprising the power supply circuit 38 which includes

the 100 KHz tuned circuit 36 connected to a full-wave

rectifier 120 which provides positive and negative un-

regulated voltages to respective voltage regulators 122,

124. The negative unregulated voltage from the fuil-

wave rectifier 120 is aiso connected to a safety shunt

control circuit 126. In addition to supplying the posi-

*

A-36 ,

3,727,616

9

tive operating voltage to the signal processor network

$0, the output of the positive voltage regulator 122 is

connected to a preset circuit 128. The output of the

negative voltage regulator 124 supplies the negative

operating voltage to the signal processor network 50.

In the signal processor network 50 the 27.12 MHz

tuned circuit 48 is connected to an r-f demodulator 130

whose output is interconnected with a 21-bit shift re-

gister (memory) 132 to couple in the overall Data

Signal, and to a mode logic circuit 134 and a stimula-

tion decoder 136 to provide the necessary clock pulses.

The mode logic circuit 134 has one output connected

to provide a Shift Register Clock to the 21-bit shift re-

gister 132 and another output connected to provide a

Stimulation Inhibit Signal to the stimulation decoder

136. Also coupled to the shift register 132 is a Memory

Preset Signal from the output of the preset circuit 128

in the power supply 38. The shift register 132 has an

- Output connected to provide a Data Completion Pulse

to the mode logic circuit 134. A 10-line output (for the

10 bits) is connected to proviae the Positive Amplitude

Word to a positive word multiplexer 138, and another

10-line output (for the other 10 bits) is connected to

provide the Negative Amplitude Word to a negative

word multiplexer 140. An output of the stimulation

decoder 136 is connected to the negative word mul-

tiplexer 140 and provides the “ON—” Signal. A second

similar output from the stimulation decoder 136 pro-

vides the “ON+" Signai to the multiplexer 138. A third

output from the stimulation decoder 136 provides an

“OFF™ Signal and it is coupled to an interpulse shunt

circuit 142 the output of which is connected to receiver

output conductors 52, 54. A 10-line output of the. posi-

tive word multiplexer 138 is connected to a positive

digital-to-analog converter 144 whose output in turn is

coupled to an inverting X4 current amplifier 146. A 10-

line output of the negative word multiplexer 140 is con-

nected to a negative digital-to-analog converter 148.

- The outputs of both converters 146, 148 are coupled to

an inverting constant current amplifier 150 whose out-

put is connected to receiver output conductors 52, 54.

Also connected to receiver output conductors 52, $4 is

a safety shunt circuit 152 which receives a safety

release signal as appropriate from the safety shunt con-

. trol circuit 126 in the power supply 38.

In operation, the digital instructions from the trans-

mitter 10 are received by the 27.12 MHz tuned circuit

48 and fed to the r-f demodulator 130 which comprises

a voltage doubler diode dctector and a low pass filter.

The pulsed r-f data signal from the transmitter 10 com-

prises the 21-bit Amplitude Data Word and a series of

Stimulation Words. Each Stimulation Word comprises

three 5-microseconds r-f pulses. The r-f demodulator

130 converts the pulsed 27.12 MHz r-f signal to a

rectified positive video signal which serves as the

Clock. The Clock Signal is used in three separate appli-

+ cations: it passes through the low pass filter which

serves as a pulse width discriminator to derive the Data

Signal for the 21-bit shift register 132, it is used in the

mode logic circuit 134 to generate the Shift Register

Clock for the sbift register 132, and it serves as a trigger

signal to the stimulation decoder 136. Demodulation of

the 3-bit Stimulation Word produces three Clock

Signals and no Data Signals because each of the 3-bits

is only 5 microseconds wide.

20

25

30

35

45

$0

$5

10

The 21-bit register 132, comprising a series grouping

of 21 flip-flop circuits, functions as a memory. It stores

a Data Completion Pulse, a Positive Amplitude Word

and a Negative Amplitude Word. The memory is ini-

tially cleared by the Memory Preset Signal which is

generated by the preset circuit 128 in the power supply

38. the 21-bit Amplitude Data Word is transmitted only

after the Memory Preset Signal has been utilized. The

Amplitude Data Word enters into the shift register 132

on the positive slope of the Shift Register Clock. The

Shift Register Clock is an inverted version of the Clock

signal which is gated depending upon whether the

receiver system is in the “receive data” mode or “-

stimulation’ mode. The 1-bit Data Completion Pulse

enters into the shift register 132 first. It is followed by a

10-bit word which represents the negative stimulating

current amplitude and another 10-bit word which

represents the positive stimulating current amplitude

word. These 21 bits of information are called the Am-

plitude Data Word, as mentioned previously

hereinabove. When the Data Completion Pulse has

been shifted into the end position of the shift register

132, the Shift Register Clock is inhibited by the mode

logic circuit 134 which converts the shift register into a

static memory.

The mode logic circuit 134 which comprises two

NOR gates determines if an inverted version of the

Clock is to go to the shift register 132 as the Shift Re-

gister Clock or if it can be processed by the stimulation

decoder 136. The absence of the Data Completion

Pulse indicates that the memory is not full. This forces

the Stimulation Inhibit Signal to be active which in-

hibits the stimulation decoder 136 while generating and

applying the Shift Register Clock to the memory. The

presence of the Data Completion Pulse mdicates that

the memory is full which causes the Shift Register

Clock and the Stimulation Inhibit Signal to be deac-

tivated. This essentially converts the shift register 132

to a static memory and allows the stimulation decoder

136 to be activated.

The stimulation decoder 136 is a “divide-by-three™

counter with each state of the counter indicating the

state of the Stimulation Word. These three states are

used to generate the time duration and polarity of the

Stimulating output current to the nerve. The resulting

three output signals (“ON+", “ON—", and “OFF™) are

mutually exclusive in that only one can be activated by

any one time. The presence of the Stimulation Inhibit

Signal disables the counter and forces the “OFF™ to its

activation state. The stimulation decoder 136 is ac-

tivated only after the 21-bit shift register 132 is full.

Only then is it permitted to count the number of Clock

pulses to determine the state of the 3-bit Stimulation

Word. The absence of the Stimulation Inhibit Signal

then enables the stimulation decoder 136 which ac-

tivates the “ON+" upon receiving the first clock pulse,

the “ON—" upon receiving the second Clock pulse, and

60 the “OFF” upon receiving the third Clock pulse. This

process is then repeated as often as required. These

* Outputs alternately select, via the positive word mul-

65

tiplexer 138 and the negative word multiplexer 140, the

Positive Amplitude Word, the Negative Amplitude

Word, or neither of the amplitude words. The latter

condition occurs during the interpulse period and

results in no stimulation of the nerve. Each of the mul-

A387

3,727,616

tiplexers 138, 140 comprise a grouping of ten AND-OR

gates. The polarity and amplitude of the nerve stimula-

tion signal is achicved by digitally selecting either the

stored Positive Amplitude Word or the stored Negative

Amplitude Word. In each case: the amplitude is

represented by a 10-bit word. Two 10-bit multiplex

switches, then, are used to select either of the two

words or neither of them. In no case are both words

selected simultaneously.

Conversion of the selected 10-bit digitally coded

Amplitude Word and conversion of the “OFF Word”

to an analog signal is performed by the digital-to-analog

converters 144, 148. Each of the converters 144, 148

comprise a grouping of ten resistors each serially con-

nected to the output of a selected AND-OR gate in its

appropriate multiplexer circuit 138, 140. Each am-

plitude bit from the multiplexers is weighted by using a

different value for each of the series resistors. The

resulting currents which flow through the ten resistors

in each converter 144, 148 are summed together to

generate a current which is directly proportional to the

digital code. No current results from a digital-to-analog

converter which is fed from an “OFF™ multiplexer.

Summation of the positive amplitude is performed in

the inverting X4 current amplifier 146 while the nega-

tive amplitude is summed in the inverting constant cur-

rent amplifier 150, each of which comprise an opera-

tional amplifier circuit. In either case, the summing of

the digital-to-analog decoding currents is performed by

an operational amplifier which allows the summation to

occur at zero volts. In this manner, ihe wetghting cur-

rent per decoding bit can be accurately established.

The weighting currents for the Positive Amplitude

Word are four times less than that of the Negative Am-

plitude Word so that less electrical power is consumed

by the positive digital-to-analog converter 144.

The inverting X4 current amplifier 146 performs

three functions: it sums together the weighting currents

of the positive stimulation current: it inverts the polari-

ty of the resulting current so that it will have a positive

polarity at the output of the inverting constant current

amplifier 150; and it amplifies the current level by a

factor of four to be compatible with the Negative Am-

plitude Word.

The function of the inverting constant current ampli-

fier 150 is threefold: it provides a constant current

source with which the nerve will be stimulated; it sums

together the weighting currents of the negative stimula-

_ tion current; and it sums in the positive stimulating cur-

rent from the inverting X4 current amplifier 146. The

latter two functions are pertormed at zero voits to ob-

tain the proper levels. These functions are performed in

the inverting constant current amplificr 150 by a unity

gain operational amplifier with the nerve being used as

the feedback impedance.

The output current from the inverting constant cur-

rent amplifier is effectively shunted out at various times

by placing two low impedance shunt circuits in parallel

across the nerve. The safety shunt circuit 152 com-

prises a field-effect transistor having a nominal 60

ohms impedance, for example, which is across the

nerve at all times except when the power supply 38 is.

activated. The state of the safety shunt circuit 152 is *

controlled by the safety shunt control circuit 126 which

comprises a low pass resistor-capacitor filter in which a

A

45

12

diode is in parallel with a | megohm resistor to

generate the Safety Release Signal. This signal is a

modified version of the unregulated negative supply

voltage from the full wave rectifier 120 and ditfers from

it only in that un unsymmetrical time delay has been in-

troduced. The time delay occurs only when the nega-

tive voltage is being increased. The absence of the

negative supply, which may be due to the lack of the.

100 KHz continuous wave power signal or due to a cir-

cuit malfunction, will result in having the 60-ohm

safety shunt circuit 152 across the nerve. Only when

the negative supply is present will the low impedance

shunt of the safety shunt circuit 182 be removed. The

other shunt is the interpulse shunt circuit 142 compris-

ing another field-effect transistor having a nominal 75

ohms impedance, for example, which 1s also across the

nerve at all times except when the “ON+" and “ON—"

states of the Stimulation Word are activated. At these

times, the interpulse shunt circuit 142 receives the

“OFF™ Signal from the stimulation decoder 136. When

the system is not activated, the two separate shunt cir-

cuits are across the nerve to insure that no extraneous

signal pick-up by the system will introduce unwanted

currents to the nerve. Failure to have both power

supply voltages present will automatically place one of

the shunts across the nerve. This provides a most

desirable safety feature.

The 100 KHz continuous wave power signal received

by the 100 KHz tuned circuit 36 is converted into posi-

tive and negative d-c voltages. These voltages are fil-

tered and regulated in their respective voliage regula-

tors 122 and 124 to provide stable supply voltages for

the receiver circuits. The function of the preset circuit

128 is to generate the Memory Preset Signal which is a

short duration positive pulse that presets the shift re-

gister 132 to zero. The Memory Preset Signal is

generated from the regulated positive supply of the

positive voltage regulator 122 when the power supply

38 is first activated. The preset circuit 128, in its sim-

plest form, comprises a high pass filter that dif-

ferentiates the regulated positive voltage received from

the positive regulator 122. In another slightly more

complex form, the preset circuit 128 may be a voltage-

sensing circuit comprising a serially connected input

field-effect transistor, zener diode and resistor-to-

ground combination connected in parallel across a seri-

ally connected resistor and grounded-emitter NPN

transistor combination. A capacitor is connected

across the zener diode-resistor series subcombination

from the negative terminal of the zener diode to the

ground side of the resistor. The base of the NPN

transistor is connected to the positive terminal of the

zener diode, and the collector, connected to the field-

effect transistor through the series resistor in the NPN

circuit, provides the Memory Preset Signal output. The

field-effect transistor acts like a constant current diode

in this circuit. Besides presetting the memory of the

shift register 132 to zero, this alternative preset circuit

clears the memory and réturns the operation back to

the “enter data mode™ from the stimulation mode, if

the positive voltage supply drops below a preset value.

Such a situation can arise, for example, by moving the

5 ansmitter probe too far away from the implanted

5 receiver during operation of the system.

Se ee

A-38

3,727,616

13

TIMING SEQUENCE

Operation of the system requires four operational

time modes. First the 100 KHz power is turned on so

that the power supply 38 can generate the required

voltages for the implanted electronics. Second, the

desired pulse amplitudes are transmitted via the Am-

plitude Data Word to the signal processor $0 in digital

form where they are decoded and stored. This phase

requires approximately 4.200 microseconds. Third,

stimulation of the nerve may now begin in real-time.

This phase of the operation will last as long as nerve

stimulation is required. Fourth, stiniulation is ter-

minated by inhibiting the stimulating word immediately

after the “OFF™ bit is transmitted and then turning off 15

the 100 KHz power.

The sequence of events which occurs in each of the

four time modes is listed below:

Mode 1, Turn-On

a. 100 KHz transmitter signal is activated.

b. Implantable power supply 38 is activated.

¢. Memory cells are preset to “O™ via the Memory

Preset Signal from the power supply 38.

d. Safety Shunt 152 is activated to remove its 60 ohm

shunt impedance from across the output §2, 54.

e. Signal processor 50 is in “enter data™ status with

the stimulation decoder 136 inhibited.

Mode 2, Transmit Data:

a. 21-bit Amplitude Data Word is serially trans-

mitted.

b. Amplitude word is decoded and stored.

c. Memory 132 is inhibited as the stimulation

decoder 136 is activated.

d, Signal processor 50 is in “stimulation” mode.

Mode 3, Stimulate

a. The first bit of the three-bit Stimulating Word will

remove the interpulse shunt 142 and will cause the

programmed positive current to flow through the

nerve.

b. The second bit of the Stimulating Word will shu-

toff the positive current and will cause the pro-

grammed negative current to flow through the

nerve.

¢. The third pulse of the Stimulating Word will shut-

off the negative current and activate the interpulse

shunt 142 across the nerve.

d. Further stimulation of the nerve can be obtained

"Dy repeating the above steps (a through ¢).

Mode 4, Turn-Off

a. The Stimulation Word is inhibited immediately

after the “OFF™ tit is transmitted. ( The interpulse

shunt 142 is deactivated to place a low impedance

across the output $2 and $4).

b. The 100 KHz power signal is shut-off.

¢. The safety shunt 152 is deactivated to place a low

impedance across the output $2 and $4.

TRANSMISSION AND STORAGE OF THE

AMPLITUDE DATA WORD:

The desired stimulating amplitudes are transmitted

as a coded 20-bit binary word along with the |-bit Data

Complation Pulse. Because of the ease of implemenung

35

40

45

$0

14

the transmitted logic network 29, a binary coded

decimal format (BCD) is used instead of a coded bi-

nary format.

The signal processor 50 receives $ this word, demodu-

lates it and stores the coded amplitude bits in its

memory. When the Data Completion Pulse has gone

through all of the flip-flops in the shift register 132 and

is finally entered in the last flip-flop, the shift register

132 is locked by inhibiting its clock and now is em-

ployed as a static memory.

During this data transmission mode no stimulation of

the nerve is performed. In fact, the interpulse shunt 142

is deactivated and places a nominal 75 ohm impedance

across the nerve to prevent voltage buildup on the

nerve and to shunt any demodulated signals that might

stimulate the nerve.

The presence of the Data Completion Pulse in the

last flip-flop signifies that the Amplitude Data. Word

has been entered into the shift register 132 and that

stimulation of the nerve can now be performed in real-

time as commanded by the transmitter 10.

TRANSMISSION AND UTILIZATION OF THE

STIMULATION WORD(S):

Stimulating instructions from the transmitter will

normally be encoded into a repetitive 3-bit pulse posi-

tioned modulated Sumulation Word(s). Each Stimula-

tion Word consists of three 5-microsecond r-f pulses

which are decoded to derive the time period of each

portion of the basic bipolar waveform. The time dura-

tion of the Negative Pulse Duration, Positive Pulse Du-

ration, and Interpulse Duration is determined by the

transmitter from the data entered into it via the

thumbwheel switches. The two abbreviated Stimulation

Words as described hereinabove are utilized for the +

and — DC Modes.

The stimulation decoder 136 provides thr-+ outputs

which control the state of the current sulse to the

nerve. These three controls are mutually exclusive in

that only one can be on at any one time. The “ON+"

signal enables only the positive digital-to-analog con-

verter 144 which causes the specified positive stimulat-.

ing current to flow through the nerve. The “ON—"

signal enabies only the negative digital-to-analog con-

verter 148 which causes the specified negative stimu-

lating current to flow through the nerve. The “OFF™

signal deactivates the interpulse shunt which places the

nominal 75 ohm shunt impedance across the nerve to

avoid voltage build-up and to reduce the de leakage

level.

I claim:

1. An electronic system for the stimulation of a

biological system in a living body, said system compris-

ing:

a. transmitter means adapted to be operably as-

sociated externally of said living body for generat-

ing transmitted pulses of radio frequency energy at

a first frequency and for additionally generating

« transmitted signals of continuous wave energy at a

second [requency, said pulses of radio frequency

energy including digital stimulation signals for

stimulating said biological system, said continuous

wave energy including power signals for providing

operating voltages in said system;

A-39

3,727,616

15

b. said transmitter means including transmitter logic

network means for receiving and processing stimu-

lation and power signal information;

¢. said transmitter means additionally including first

and second analog channel network means

operably connected to said transmitter logic net-

work means and responsive thereto, said first

analog channel network means generating said

pulses of radio frequency energy at said first

frequency containing said digital stimulation

signals, said second analog channel network means

generating said continuous wave’energy at said

second frequency containing said power signals;

d. said transmitter means further including first and

second resonant circuit means operably connected

to said first and secondeanalog channel network

means, respectively, and responsive thereto, said

first resonant Circuit means resonant at substan-

tially said first frequency for transmitting said pul-

ses of radio frequency energy containing said

digital stimulation signals, and said second reso-

nant means resonant at substantially said second

frequency for transmitting said continuous wave

energy containing said power signals;

€. receiver means adapted to be operably positioned

within said living body for receiving said pulses of

radio frequency energy containing said digital

stimulation signals at said first frequency and for

additionally receiving said continuous wave energy

containing said power signals at said second

frequency as transmitted from said_transmitter

means,

said receiver means including third and fourth

. resonant circuit means responsive to said second

and first resonant circuit means, respectively, said

_ third resonant circuit means resonant at substan-

tially said second frequency for receiving said

transmitted continuous wave energy containing

said power signals, and said fourth resonant circuit

means resonant at substantially said first frequency

for receiving said transmitted pulses of radio

frequency energy containing said digital stimula-

tion signals:

g. said receiver means additionally including power

supply circuit means operably connected to said

third resonant circuit means and responsive to said

continuous wave energy containing said power

signals received by said third resonant circuit

means for providing said operating voltages: for

said receiver means, and

h. said receiver means further including signal

processor network means operably connected to

said power supply circuit means and to said fourth

resonant circuit means, said signal processor net-.

work means responsive to said operating voltages

from said power supply circuit means and addi-

tionally responsive to said pulses of radio frequen-

cy energy containing said digital stimulation

signals at said first frequency for providing stimu-

lating signals to said biological system.

2. The electronic system defined in claim 1, wherein

said first, setond, third and fourth resonant circuit

means cach comprise in cumbination a cupucitor and

an associated inductur, said inducturs of said first and

fourth resonant circuit means each being an antenna

—

el

20

25

30

33

45

35

16

Operable substantially at said first frequency and said

inductors of suid second and third resonant circuit

means each being an antenna operable substantially at

said second frequency.

3. The electronic system detined in claim 1, wherein

said first analog channel network means comprises

oscillator means for generating said radio frequency

energy at said first frequency, switch means coupled to

said oscillator means responsive to said transmitter

logic network means for combining said radio frequen-

cy energy at said first frequency with said digital stimu-

lation signals, and amplifier means connected to said

switch means for amplifying signals received through

said switch means.

4. The electronic system defined in claim 1, wherein

said second analog channel network means comprises

oscillator means for gencrating said continuous wave

energy at said second frequency, switch means coupled

to said oscillator means responsive to said transmitter

logic network means for combining said continuous

wave energy at said second frequency with said power

signals, and amplifier means connected to said switch

means for amplifying signals received through said

switch means.

S. The electronic system defined in claim 1, wherein

said signal processor network means includes:

a. a radio frequency demodulator operably con-

nected to said fourth resonant circuit means and

responsive thereto;

b. shift register means operably connected to said

radio frequency demodulator for receiving a data

signal from said radio frequency demodulator and

for providing a positive amplitude word, a negative

amplitude word and a data completion pulse, said

shift register means also operably connected to

said power supply circuit means for receiving a

memory reset signal therefrom.

. mode logic circuit means operably connected to

said radio frequency demodulator and to said shift

register means for receiving a clock signal from

said radio frequency demodulator and for receiv-

ing said data completion pulse from said shift re-

gister means, said mode logic circuit means

providing a shift register clock also said shift re-

gister means and for providing a stimulation inhibit

signal;

. stimulation decoder means operably connected to

said radio frequency demodulator and to said

mode logic circuit means for receiving a triggering

clock signal from said radio frequency demodula-

tor and for receiving said stimulation inhibit signal

from said mode logic circuit means, said stimula-

tion decoder means s providing mutually exclusive

output signals including “ON+", “ON—" and

“OFF™ signals;

¢. positive word multiplexer means operably con-

nected to said shift register means and to said

stimulation decoder means for receiving and

selecting said positive amplitude word from said

« shift register means and for receiving said “ON+"

signal from said stimulation decoder means; °

f. negative word multiplexer means operably con-

nected ‘to said shift register means and to said

stimulation decoder means for receiving and

selecting said negative amplitude word from said

A-40

3,727,616

17 18

shift register means and for receiving said “ON—"

signal from said stuumulation decoder means;

B- Negative digital-to-analog converter means

operably connected to said negutive word mul-

e. safety shunt control circuit means operably con-

nected to said negative voltage regulator means

responsive thereto for providing a safety

release signal for said receiver means.

8. A transmitter for generating transmitted pulses of

radio frequency energy at a first frequency containing

digital stimulation signals for the stimulation of a

biological system in a living body and for additionally

generating transmitted signals of continuous wave

19 energy at a second frequency containing power signals,

said transmitter comprising:

tiplexer means and responsive thereto for convert- $

ing said negative amplitude word to an analog

signal, ‘

h. positive digital-to-analog converter means

operably connected to said positive word mul-

tiplexer means and responsive thereto for convert-

ing said positive amplitude word to an analog

signal; :

i. inverting X4 current amplifier means operably

connected to said positive digital-to-analog con-

verter means and responsive thereto for providing

an output signal amplified by substantially a factor

of four to be compatible with said negative am-

plitude word;

j. inverting constant current amplifier means

operably connected to said inverting X4 current

amplifier means and to said negative digital-to-

analog converter means and responsive thereto for

providing said stimulating signals to said biological

system; and

k. shunt circuit means operably connected to said

stimulation decoder means and to said power

supply circuit means for receiving said “OFF™

signal from said stimulation decoder means and for

receiving a safety release signal from said power

supply circuit means to provide protcction against

undesired stimulating signals.

6. The electronic system defined in claim 5, wherein

said shunt circuit means comprises interpulse shunt cir-

cuit means operably connected to suid stimulation

decoder means for receiving said “OFF™ signal: and

safety shunt circuit means operably connected to said

power supply circuit means for receiving said safety

release signal, said interpulse shunt circuit means and

said safety shunt circuit means operably coupled in

parallel across said biological system.

+ 7. The electronic system defined in claim 1, wherein

said power supply circuit means comprises:

a. full-wave rectifier means operably connected to

said third resonant circuit means and responsive

thereto for converting said continuous wave ener-

gy received from said third resonant circuit means

into positive and negative d-c voltages;

b. positive voltage regulator means operably con-

nected to said full-wave rectifier means for receiv-

ing said positive d-c voltages from said full-wave

rectifier means and for providing regulated posi-

tive operating voltages for said receiver means;

¢. preset circuit means operably connected to said

positive voltage regulator means and responsive

thereto for providing a memory preset signal com-

4$

$0

a. logic network for receiving and processing stimu-

lation and power signal information;

b. first and second analog channel network means

operably connected to said logic network means

and responsive thereto, said first analog channel

network means generating said pulses of radio

frequency energy at said first frequency containing

said digital stimulation signals, said second analog

channel network means generating said continu-

ous wave energy at said second frequency contain-

ing said power signals. said first analog channel

network means including:

1. first osciilator means for generating said radio

frequency energy at said first frequency,

2. first switch means coupled to said first oscillator

means responsive to said logic network means

for combining said radio frequency energy at

said first frequency with said digital stimulation

signals, and

3. first amplifier means connected to said first

switch means foe amplifying signals: received

through said first switch means,

said second analog channel network means includ-

ing:

1. second oscillator means for generating said con-

tinuous wave energy at said second frequency,

2. second switch means coupled to ‘said ‘second

oscillator means responsive to said logic net-

work means for combining said continuous wave

energy at said second frequency with said power

signals, and

3. second amplifier means connected to said

second switch means for amplifying signals

received through said second switch means; and

c. first and second resonant circuit means operably

connected to said first and second analog channel

network means, respectively, and responsive

thereto, said first resonant means resonant at sub-

stantially said first frequency for transmitting said

pulses of radio frequency energy containing said

digital stimulation signals, and said second reso-

nant circuit means resonant at substantially said

second frequency for transmitting said continuous

wave energy containing said power signals.

9. The transmitter defined in claim 8, wherein said

first and second resonant circuit means each comprise |

in combination a capucitor and an associated inductor,

said inductor of said first resonant circuit means being

60 3f antenna Operable substantially at said first frequen-

cy and said inductor of said second resonant circuit

means being an antenna operable substantially at said

second frequency.

prising a short duration postive pulse for said

receiver means,

_d. negative voltage regulator means operably con-

nected to said full-wave rectificr means for receiv-

ing said negative d-c voltages from suid full-wave

rectifier means and for providing regulated nega-

tive operating voltages for suid receiver means,

and

r

"Inited States Patent 19)

Wingrove

A-41

111) 3,833,005

145) Sept. 3, 1974

[54] COMPARE.) COUNT DIGITALLY

CONTROLLED PACEMAKER

{75] Inventor: Robert C. Wingrove, Circle Pines,

Minn.

(73] Assignec: Medtronic, Inc., Minneapolis, Minn.

July 26, 1971

{21} Appl. No.: 166,219

(39) Bett. CBanrccorcesccccscceccscesccsecsossesesesccsecese AGin 1/36

{58} Field of Search......... 128/419 C, 419 E, 419 P,

128/419 R, 421, 422; 307/220, 231, 340/146.2

Primary Examiner—William E. Kamm

Attorney, Agent, or Firm—Lew Schwartz; Wayne A.

Sivertson

[57] ABSTRACT

A cardiac pacer having adjustable rate and/or pulse

width controls controlled by digital means including a

first counter for receiving information and sioring the

data, a second counter connected to clock means, and

logic means for comparing the outputs of the first and

second counters to determine pulse rate and width.

The preferred embodiments of the digitally controlled

pacer include means connected to the first counter for

receiving coded set signals and rejecting noise and

other interference signals. The preferred embodiment

of a transmitter for sending coded signals to the pacer

is also shown, the transmitter being digitally operable

to provide coded bursts of RF pulses to the pacer re-

ceiver.

25 Claims, 4 Drawing Figures

at

(56) References Cited

UNITED STATES PATENTS

3,557,796 1/1971) = Keller, Jr. et al... 128/419 P

3.629,710 §2/1971 Durland ........0. 307/220 X

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COMPARED COUNT DIGITALLY CONTROLLED filter 10 comprising a coil 11 across which is connected

PACEMAKER a capacitor 12, A diode 13 and a capacitor 14 are con-

BACKGROUND OF THE INVENTION

Cardiac pacers and other implantable stimulation de-

vices aie well known by those reasonably skilled in the

art. A search is coniinually under way to produce an

improved device which has a simple programing capa-

bility for rate and amplitude control, for example, 10

which hes an input error protection to prevent noise

signals from causing dangerous situations, which is

safe, and which has as low as possible power consump-

tion. The apparatus of this invention provides these and

other advantages over the prior art by utilizing a digital 15

approach to what has for the most part been Cone in

analog circuitry in the prior art, and by providing cir-

cuits which can be reduced to integrated circuitry to

thus provide a minimum power drain. Such advantages

of a digital approach are known in the prior art, as for 20

example U.S. Pat. No. 3,557,796.

SUMMARY OF THE INVENTION

Briefly described, the pacer apparut “this inven:

tion includes a memory in the form

counter, and a second digital counter connected to

continually count a digital clock. A first network of a

logic circuitry interconnects the first and second count-

ers for purposes of compating outputs. When the out-

put of the second digital counter is the sume as that of

2 portion of the memory to which it is being compared,

an output signal is provided from the logic circuitry.

This output signal triggers a pacemaker output pulse

which travels to electrodes adapted tw be connected to

the heart. The data for the memory is provided, in the *5

preferred embodiment, through an RF receiver-filter

which is connected to the memory through a decoder

network. The decoder network or circuitry is provided

to prevent the passage of extraneous 60 cycle noise sig-

nals and to prevent the passuge of almost all conceiv-

able noise signals. The pacer apparatus of this inven-

tion also includes further circuit means connected to

the first counter and to the pacer output pulse circuitry

w first digital 23 °°

nected in series across capicitor 12. A resistor 15 is

connected across cupacitor 14, A transistor 16 has its

base connected to one side of resistor 15 and its emitter

connected to the other side of resistor 15. The emitter

of transistor 16 is also connected to ground, while the

collector of transistor 16 is connected through a resis-

tor 17 to a positive power input terminal 18.

There is also shown a decoder 20 which is used to

greatly decrease the likclihood of extrancous noise sig-

nals affecting the pacer. Decoder 20 includes an in-

verter 21 which has an input connected to the collector

of transistor 16, The output of inverter 21 is connected

through a resistor 22 to the input of another inverter

23. A resistor 24 and a diode 25 are connected in series

across resistor 22. The input of inverter 23 is also con-

nected through a capacitor 26 to ground. The output

of inverter 23 is connected through a capacitor 27 to

an input 28 of a two-input positive nor logic gate 29.

Input 28 of gate 29 is also connected through a resistor

31 to power input terminal 18. The other input 32 of

gate 29 is connected by a lead 33 to the output of in-

Mr Phe ostputef onte ID istonnyciedtc: = can:

pacitor 34 to an input 35 of another two-input positive

nor logic gate 36. Input 35 is also connected to a resis-

tor 37 to power input terminal 18. The other input 38

of gate 36 is connected by a lead 39 to the collector of

3 transistor 16,

In FIG, 1 there is als» shown a set counter 40 for re-

ceiving the decaded external signal. The output of gate

3% is connected to the count input terminal of counter

40, which is connected as a digital counter having a

plurality of outputs including outputs 42, 43, 44, 45,

46, 47, and 48. A resect terminal of counter 40 is con-

nected through a line 41 to the output of gate 29.

There is also shown a comnurison logic circuit 50,

comprising four two-input exclusive or gates 51, $4, $7

40 and 61 us well as four-input positive nor logic gute 64

and un inverter 69. An input 52 of gate 51 is connected

to counter output terminal 45, An input 55 of gate 54

is connected to counter output terminal 44, An input

for determining pulse width according to the informa- __ 58 of gate 57 is connected to counter output terminal

tion stored in the memory.

The coded RF input pulses are provided, in the pre-

ferred embodiment, by a transmitter which includes yet

another digital counter, the outputs of which ure select-

able to provide the desired duta to the memory in the

pacer apparatus. The selected data is transmitted in *

coded form automatically by the transmitter.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schemutic diagram of the digital pace-

maker appuratus of this invention;

FIGS. 2a, b, and ¢ comprise graphs of the coded pulse

input to the apparatus of FIG. 1 for providing data to

the memory;

FIG. 3 is a schematic di of the transmitter ap-

paratus of this invention provides data to the ap-

paratus of FIG. 1; and

FIG. 4 is another embodiment of the pacer apparatus

of this invention.

DESCRIPTION OF THE PREFERRED

EMBODIMENTS

Referring now to FIG. 1 there is shown a receiver-

45 43. An input 62 of gate 61 is connected to counter out-

put terminal 42, The output of gute 51 is connected to

an input 65 of gate 64, The output of $4 is connected

to an input 66 of gate 64, The output of gate $7 is con-

nected to un input 67 of gate 64, The output of gate 61

is connected to an input 68 of gate 64. The output of

gate 64 is connected to ihe input of inverter 69.

There is utso shown a clock counter 70 which has a

plurality of count output terminals including terminals

72, 73, 74, 75 and 76. Terminul 72 is connected to an

5 input 63 of gate 61. Terminal 73 is connected to an

input $9 of gate $7, Terminal 74 is connected to an

input 56 of gate 54. Terminal 75 is connected to an

input 53 of gate 51.

There is also shown in FIG. 1 a clock 80 comprisi

a pair of inverters 81 and 82. The output of inverter 8

is connected to the input of inverter of 81 by a pair of

serially connected resistors 83 and 84, and is connected

sirectly to the input of inverter 82, The output of in-

65 Vetter 82 is connected to the input of 82 through the

serially combination of u capac:tor 85 and resistor 83,

and is directly connected to a count input terminal of

clock counter 70,

A-47

3,833,005

3

There is also shown a one-shot multivibrator 90. Mul-

tivibrator 90 includes a two-input positive nor logic

gate 91 having a first input 92 which ‘is connected

through a capacitor 93 to the output of inverter 69, and

which is connected through a resistor 94 to a positive

power input terminal 95, Output terminal 76 of counter

70 is connected to the input of an inverter 77 which has

an output connected to another input 96 on gute 91.

The output of 91 is connected through a diode 97 to

the input of an inverter 101. The input of inverter 101

is connected to ground through a parallel combination

of a capacitor 98 and a resistor 99, The output of in-

verter 101 is connected through 2 capacitor 111 toa

reset input terminal on counter 70, The reset counter

terminal of counter 70 is also connected to ground

through a resistor 112.

There is also shown a pacer output pulse circuit 100.

Circuit 100 includes an inverter 102 which has its input

connected to the output of inverter 101 and its output

connected through a resistor 103 to the buse of a tran-

sistor 104, The collector of transistor 104 is connected

through a resistor 105 to a power input terminal 106,

and is connected through a capacitor 107 to an clec-

trode terminal 108, The emitter of transistor 104 is

‘Connected to ground! and to an elecratle terminal 109.

Electrode terminals 108 and 109 are adapted to be

connected to electrodes which are in turn adapted to

be connected to the heart.

In FIG. 1 there is also shown output pulse width ad-

justment circuitry 120, Circuitry 120 includes a junc-

tion 121 connected through a serial combination of a

diode 122 and a resistor 123 to terminal 46 of counter

40. Junction 121 is also connected through a scrial

combination of u diode 124 and a resistor 125 to

counter output terminal 47, and through a serial com-

bination of a diode 126 and resistor 127 to counter out-

t terminal 48, Junction i21 is also connected to the

put of inverter 101,

In FIG. 2 there are shown three graphs, «a, b and ¢ rel-

ative to the input signal to the pacer of FIG. 1. In

graphs a and b it can be seen that the pulses for setting

counter 40, pulses B, are preceded by a longer pulse A

which is of a coded pulse width. Pulses A and B as re-

ceived at receiver 10 comprise a burst of radio fre-

quency pulses transmitted from a transmitter such as

that shown in FIG. 3.

The burst of pulses comprising pulse A of graph a is

received across coil 11 and capacitor 12, and the radio

frequency components are filtered out by diode 13 and

cupacitor 14 such that pulse A of graph b is seen across

resistor 15 to turn on transistor 16, ‘The output of tran-

sistor 16 is felt at the input of inverter 21 and on input

38 of gate 36. Gate 36 has un output which is normally

ZERO which will not change at this instant in time inas-

much as input 35 of positive nor gate 36 is held at a

ONE due to the charge on cupacitor 34, However, the

input signal oulse A felt ut the input to inverter 21 will

cause its ZERO output to change to a ONE.

The input of inverter 23 will not, however, ever, instan-

change to 2 ONE, becuuse of the charge time

of 26 through resistor 22. Therefore, the out-

put of inverter 23 will remain a ONE until a minimum

time has passed for the charging of cupacitor eho he

4

22 and capacitor 26 will not affect the pacer operation.

After the minimum time has elapsed capacitor 26 will

have charged sufficiently to cause the output of in-

verter 23 to go to ZERO. The switch of the output of

inverter 23 from ONE to ZERO will cause capacitor 27

to commence charging through resistor 31. During the

time of charge of capaciior 27, input 28 of gate 29 will

temporarily be at the ZWEO level for a predetermined

time. This predetermined period sets the maximum

time for the coded signal A to affect the pacer. The out-

put of inverter 2! is also felt on input 32 of gate 29 and

as long as that output is a ONE, there will be no signal

at the output of gate 29. However, if the output of in-

verter 21 changes back to a ZERO (input signal A

ceases) during the predetermined time of the charge of

capacitor 27, then the output of gate 29 will change to

a ONE. Thus, if an extraneous noise signal occurs

which is longer than the minimum time determined by

Capacitor 26 it may not be longer than the maximum

time determined by capacitor 27 or it will still not af-

fect the pacer. Input pulse A, as shown in graphs a and

b is sclected to end between the maximum and mini-

mum times.

—As-stated aborc,-witen Pulsc-A ‘cnds-the-ontpet of-

x

35

a

gate 29 will change from ZERO to ONE. This is felt

through line 41 to reset counter 40, and wiil cause the

discharge of capacitor 34 thus putting a temporary

ZERO pulse on input 35 of gate 36. Input 35 will re-

main ZERO during the recharge time of cupacitor 34

after input pulse A ends. This second predetermined

period of time is selected to be just sufficient to open

gate 36 for a period of time sufficient to put in the max-

imum number of count pulses to digital counter 40. As

can be seen from graphs a, b and ¢, a piurality of count

signals are transmitted, the number being determined

by setting the transmitter, which are felt through re-

ceiver 10 on input 38 of gate 36 through line 39. As the

input pulses change from ZERO to ONE state, the out-

put of gate 36 will also change from state to state caus-

. ing a counting of the pulses in counter 40, When the re-

45

”)

65

charge of ceracitor 34 has been accomplished, gute 36

will be shut off and the counting will end. The counted

pulses will appear on count output terminals 42-45,

which are connected, respectively, to one input on

cach of gates $1, $4, 57 and 61.

Clock 80 is continually sending a series of pulses to

counter 70, and the count is appearing on terminals

72-75 which are also connected to gates 51, 54, 57 and

61. The output of gate 64 is normally a ZERO. How-

ever, when all four output terminals 42-45 of counter

40 match the respective output terminals 72-75 of

counter 70 then each of the outputs of gates 51, $4, 57

and 61 will go to ZERO, thus causing all four inputs’

65-68 of gute 64 to go to ZERO and causing the output

of gate 64 to go to a ONE. This ONE is felt at the input

of inverter 69 causing it to change to an output of

ZERO, which output will be felt at the input to multivi-

brator 90,

As inverter 69 its to ZERO, the

changing pulse will be differentiated by capacitor 93

and resistor 94 to cause the to present a

btectesencbaniy <9 pr goalie elt:

be held at a ONE by the output

as output terminal 76 of counter 70 is a ZERO. By se-

A-48

3,833,005

lecting terminal 76 to represent the next count after the

highest represented by termiauls n-75 (for example, if

terminal 75 represents the “8" count then terminal 76

is seiected to represent “16” count of the digital

counter 70) a minimum rate for the pacer output pulse

can be established. It is therefore apparent that the first

time that a pulse charge appears at the output of in-

verter 69, the leading edge of which is felt at input 92

of gate 91, there will be no change at the output at gate

91. However, the second time that terminals 72-75 of 10

counter 70 match terminals 42-45 of counter 40 termi-

nal 76 will have been switched to a ONE and input 96

at gate 91 will be cisabled. Therefore, the second out-

put of inverter 69 will cuuse at its leading edge, the out-

* put of gate 91 to change to a ONE. This change will be

felt through diode 97 to commence the charge of ca-

pacitor 98 causing inverter 101 to have an output

switch from the ONE to the ZERO state, representing

the output of multivibrator 90. The time which the out-

put of multivibrato: 90 remains on and determined by

the parallel combination of capacitor 98 and resistor

99, thus giving a predetermined output pulse width to

the pacer output pulse. The output of multivibrator 90

is felt at inverter 102 to cause its output to go to a ONE.

— Fre-caases the-tesn-on of transistor 2404 and thus

causes an output pulse to be applied to electrode termi-

nals 108 and 109 which will be felt ut the heart.

The output of multivibrator 90 is also felt through the

combination of capacitor 111 and resistor 112 on the

reset terminal of counter 70, such that the trailing edge

of the output of inverter 101 causes a reset of counter

70. This reset will clear all of output terminals 72-76,

thus disubling gate 91 and commencing the count cy-

cle.

Thereafter, clock 80 will again cause counter 70 to

receive pulses which will eventually again cuuse termi-

nal 76 to be in the ONE state at the sume time that out-

put terminals 72-75 match the respective of output ter-

minals 42-45§ of counter 40, The number of pulses nec-

essary to reach this state thus determined the rate at

which pacer output pulses are provided to the heart.

The count in sct counter 40 will remain the same unless

the operator uses the transmitter to set another count

in counter 40, thus changing the rate. As hus been

pointed out above, only extraneous noise signuls which

coincidentally fall between the minimum and maxi-

mum times determined by the decoder 20 cun enuble

the input to counter 40, and even should such a pulse

occur the count will change only if this noise signal is

followed by pulses which are completed during the *

time period determined by the charge time of capacitor

34. As most extraneous noise signals are of the 60 cycle

per second variety, times have beer selected which will

prevent any reasonable possibility of such noise signals ‘

from changing the count in set counter 40 and thus af-

fect the pacer rate. For example, pulse A has been se-

lected to be 13 milliseconds to fall between a maximum

and minimum gute time of 11 to 15 milliseconds as de-

termined by capacitors 26 und 27 respectively. There-

after, leccaront eo ie dant idl eat yee od er

B are completed within > ster Aa milliseconds,

the pulses being approximately 100 microsecond: wide

with a repetition rate of approximately 250 microsec-

onds.

Referring again to FIG. 1 a variation of the apparatus

of this invention can be seen with regard to output

Pulse width adjustment apparatus 120. As has been ex-

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plained above, the output pulse width is determined by

the pulse time of multivibrator 90. The pulse time of

one-shot multivibrator 90 is in tum determined by the

parallel combination of capacitor 98 and resistor 99.

Resistors 123, 125 and 127 have been provided so that

the operutor cf the transmitter may select the output

pulse width he desires by changing the count in counter

40. Wehn any of output terminals 46, 47 or 48 are in

the ZERO state then the respective of resistors 123,

12§ and 127 will be in parallel with resistor 99. Thus,

the operator may sclect an input count which, in addi-

tion to determining the rate by setting the states of ter-

minals 42-45, will in addition set the stat2s of terminals

46-48 to vary the resistance in multivibrator 90 to vary

the output pulse width of the entire pacer. Diodes 122,

124 and 126 are provided to prevent a current flow into

capacitor 98 when the respective of terminals 46, 47

and 48 are in the ONE state.

Referring now to FIG. 3, there is shown a transmitter

which may be used to provide coded input information

to the digitally controlled pacer of FIG. 1. In FIG. 3

there is shown a one-shot multivibrator 200. Multivi-

brator 200 includes a positive power input terminal 201

and a ground bus 202. A switch 203 has a first terminal

204 onder secomxtemmimah Sess Power tenia 268 ts ~

connected through a serial combination of a resistor

206 and a resistor 207 to terminal 204, Terminal 205

is connected to bus 202. A capacitor 208 is connected

between terminals 204 and 205. Another capacitor 209

is connected from terminal 204 to the input of an in-

verter 211. The input of inverter 211 is also connected

to a junction between resistors 206 and 207. The out-

put of resistor 211 is connected through a diode 212 to

another inverter 213. A parzilel combination of a ca-

pucitor 214 and a resistor 215 is connected between

the inpu’ of inverter 213 and bus 202.

In FIG. 3 there is also shown oscillator control cir-

cuitry 220. Circuitry 220 includes an inverter 221

which has an input connected to the output of inverter

213 and an output connected to an input 222 of a two-

input positive NOR logic gate 223. The output of gute

223 is connected to the input of another inverter 224.

Yet another inverter 225 has un output connected to an

input 226 of gate 223. Inverter 225 has its input con-

nected to a positive power input terminal 227 through

a resistor 228. The input of inverter 225 is also con-

nected to one side of a capacitor 259.

There is also shown an osciliator 230 which has an

input connected to the output of inverter 224 and an

output connected to atrnsmitting coil 231. Coil 231

is adapted to transmit signals that will be received by

coil 11 of receiver filte: 10 described in the discussion

of FIG. 1 above.

FIG. 3 also discloses u locking gute 240 which in-

cludes a two-input positive NOR logic gate 241. Gate

24° has an input 242 connected through a capacitor

243 to the output of inverter 213, and connected to a

resistor 244 to bus 202. Another two-input positive

NOR logic gute 246 has un input 247 connected to the

Cutput of gate 241. The output of gate 246 is connected

to an input 245 on gate 241.

There is also shown a gated clock 250. Cock 250 has

a two-input positive NOR logic gate 251 which has an

output connected to the input of an inverter 252. The

output of inverter 252 is connected to the other plate

of capacitor 229 and by a serial combination of a ca-

pacitor 253 ar.d a resistor 254 to an input 255 of gate

A-49

3,833,005

7

251. A resistor 256 is connected from a junction be-

tween capacitor 253 and resistor 254 to the input of in-

verter 252. Another input 257 of gute 251 is connected

to a positive power input terminal 258 through a capac-

itor 259. Input 257 is also connected ‘hrough a resistor

261 to the output of gate 241. A diode 2£2 is con-

nected across resistor 261.

FIG. 3 also shows an output pulse counter 270.

Courter 270 has a reset input terminal connected to

the output of invester 223, and a count input terminal

connected to the output of invertor 225. Counter 270

also has a plurality of output terminals 271, 272, 273,

274, 275, 276 and 277.

Also shown in FIG. 3 is a pacer rate control circuitry

280. Circuitry 280 includes a multi-positional switch

281 and a plurality of diodes such as 282 connected in

a predetermined sequence to output terminals 274,

275, 276, 277 on counter 270.

Also shown is a pacer output pulse control circuitry

290 which includes a multi-positional switch 291 and

a plurality of diodes such as 292 connected in a prede-

termined configuration to output terminals 271, 272,

273 on counter 270.

The wiper arms of switches 281 and 291 are con-

nected to g bus 301. Bus. Lbs a first end connected

through a resistor 302 to a positive power input termi-

nal 303. A secord end of bus 301 is connected to the

anode of the diode 304, The cuthode of diode 304 is

connected to ground through a resistor 30S and to un

input 248 on gate 246,

The operation of the transmitter of FIG. 3 is com-

menced by the closure of switch 203 which may be ac-

complished cither manually or automatically. This

causes the input of inverter 211 ot go to a ZERO. The

input of inverter 211 had been at a ONE duc to the ef-

fect of the RC network comorising resistors 206 and

207 and capacitors 208 and 209, being connected be-

tween bus 202 and positive input terminal 201. This

change from ONE to ZERO of the input of inverter 211

will cause its output to change from a ZERO to a ONE.

This will be felt through diode 212 across the parallel

RC network comprising capacitor 214 and resistor 215,

and on the input of inverter 213. The output of invercer

213 will therefore change from a ONE to a ZERO and

remain a ZERO for a time determined by the RC time

constant of capacitor 214 and resistor 215. This time

is chosen to be the pulse width A snown in FIG. 2a and

b, which in the specific configuration mentioned above

would be 13 milliseconds to fall between the gated on

time of 11 to 15 milliseconds provided in decoder 20

described in the above discussion of FIG. 1.

When the output of inverter 213 goes to ZERO this

change will be felt on the input of inverter 221 of oscil-

lator control circuitry 220. This will cause an output

change from ZERO to ONE at inverter 221 thus caus- ~

ing a positive signal to appear at input 222 of gate 223.

The output ONE at inverter 221 is also felt at the reset

terminal of counter 270 to reset all of its output termi-

nals to ZERO. The positive input will cause positive

NOR logic gate 223 to have an output c from

8

scribed above. Thus, the output of inverter 213 will re-

turn to ONE, the output of inverter 221 will return to

ZERO, which change will be felt on the input of gate

223 causing it to return to ONE state, thus causing the

$ output of inverter 224 to return to the ZERO state to

shut off oscillator 230. It will thus be apparent that tine

burst of pulses on coil 231 will be present for a period

of time determined by multivibrator 200, to produce

the coded burst of pulses shown at A in FIG. 2 a.

10 = The trailing edge of the output pulse from multivibra-

tor 200, that is the return of the output of inverter 213

to the ONE state, wiil be felt across a differentiator

comprising capacttor 243 and resistor 244 thus causing

a positive signal to appear ut input 242 of gate 240.

1S This positive inpct «ill cause positive NOR logic gate

241 to change its output froin a ONE to a ZERO. This

change is felt at input 247 of gute 246 causing its output

to change from a ZERO to a ONE. This positive output

of gate 246 is comnected to input 245 of gate 241 and

29 locks on gate 241 so that its output remains a ZERO.

The effect of input 248, which is normally a ZERO, on

locking gate 241, will be described below.

When the output of gate 241 changes to ZERO, this

will be felt through resistor 261 to gate on clock 250 by

25 changing the input 257 of gate 2512 The gated clock

250 then operutes ut a predetermined frequency, pro-

viding a square wave output in a manner well known to

those of reasonulse skill in the art.

The output of clock 250 is felt through the RC net-

®” work of capacitor 229 and resistor 228 on the input to

inverter 225, The negative going edges of the square

wave output will cause the output of inverter 225 to

change from its normal ZERO to a ONE. However, the

period of time that this change remains is deterinined

35 by the RC time constant of capacitor 229 and resistor

228, und thus the pulse width as shown in B of FIG. 2

a and b is determined. In the specific example given

above, this pulse width is chosen to be 100 microsec-

onds. This change in output of inverter 225 from a

4 ZERO toa ONE & felt at innut 226 of gate 223, and at

the count input terminal of counter 270 wicre it is

counted. The result of the positive input at 226 of gute

223 is uw change from ONE to ZERO at the output of

gute 223 thus cuusing a change from ZERO to ONE at

” the output of inverter 224, The positive signal out of

inverter 224 will turn on oscillator 230 to provide a

burst of pulses at coil 231. This burst of pulses v-ili be

on for a period of time determined as described above

by capacitor 229 2nd resistor 228. Thus, short bursts of

pulses are transmitted by coil 231 as shown at B in FIG.

oe The pulse repetition rate is determined by clock

As has been described in the discussion of FIG. 1, set

counter 40 receives u predetermined number of pulses

as shown in FIGS. 2u - ¢, and having counted these

pulses, then provides outputs at terminals 42 - 48, from

which the pacer rate and pulse width are determined.

The transmitter of FIG. 3 allows the ng of

the pulses into set counter 40 of FIG. 1 through the use

of switches 281 and 291, which in conjunction with di-

ONE to ZERO. This change will be felt at the input of odes 282 and 292 and counter 70 determine, respec-

inverter 224 causing its output to go from ZERO to

ONE. The positive going signal at the output of inverter

tively, pacer pulse rate and paccr output pulse width.

As noted above, counter 270 is reset to an all ZERO

224 will turn on oscillator 230 thus causing a burst of |. State at the time the transmitter sends the code pulse A.

to appear on coil 231. The oscillator 230 will re- ~ Whereafter, when pulses B are being sent, the pulsing

main on until the output signal of one-shot multivibr--

tor 200 returns to its original state, in the manner de-

of inverter 225 is received and counted by 270,

The wiper arm of, for example, switch 281 will be con-

A-50

3,833,005

9

nected through selected one or more of dixjes 282 to

the selected ones of counter output terminals 274-277.

Following the reset of counter 270, all of outputs

274-277 would be in the ZERO state. Thus, current

flow will be felt from power input terminal 303 through $

resistor 302, through the selec:ive of diodes 282, to the”

ZERO state at the respective of terminals 274 - 277.

Thus, the anode of diode 304 will be in the ZERO state

and a ZERO will be felt at input 248 of gate 246, thus

keeping the output of gate 246 at a ONE and locking 10

in the ZERO output of gate 241 as described above.

The operation of switch 291, to determine pacer out-

put pulse width operates in the same manner, such that

selective of diodes 292 will connect bus 301 to a ZERO

until such time as the selective of counter outputs 271 15

- and an input 459 connected to output 476 of counter

- 273 have all reached a ONE state.

When the output pulses from the transmitter have

reached a perdetermined count as determined by

counter 270 so that, in the switch selection shown in

FIG. 3, for example, all of counter terminals 274 - 277 20

are in the ONE state, then the positive signal will be felt

on the anode of diode 304 causing a ONE signal to ap-

pear on input 248 of gute 246. This in turn will cause

the output of 246 to go to ZERO, which in turn will be

felt at input 24

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