# Appendix — Cordis Corp. v. Cardiac Pacemakers, Inc. > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/brief%3Amicro_IA40385010_0585%3A2 ## Record - **Collection:** Supreme Court brief - **Document type:** Appendix - **Published:** January 1, 1983 - **Citation:** 461 U.S. 906 ## Text 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 Opinion of the Court of Appeals.............6000005 A-1 Opinion of the District Court ................0 0000. A-4 RE PCa o ov ke) Cdeeenervseacewbesbabeh een A-17 EL MUG Ue cp vb oes tyre Ved ee keoekee hs Se A-18 NES C0 i nos Fe veba i cavineasseeaeenusan A-19 EN UNS s'n9'0'y 0'ok'v vw hs d yite ea bale hele Ske om oe A-26 NOIR s.5 vb-s'ou'5.0o Koop tease tdeen tee Leeae A-41 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 A-8 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 A-10 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. A-1l 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 A-12 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. A-16 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 Grsenetemen os cz] [Rs (-) oF) (-) 35 oe TER / DECODER} RESET fe ae T " t (+) 37 “) aire Se a | BINARY COUNTER | RESET me ee a oe eee 39 | | Reaiineliean ILATERAL Sy a witen . & eeewewewe RI7 cs: 5 Ra | R9 +V O Melyeydanre—aaa ra) rd re ‘R? ‘Re oN 4 -) ’ 3,805,796 A-20 PATENTED APR 23 1974 INVENTORS S et Yong erevee bad HOLIMS Zivtig avn ~s! Narre 5, Terry , rent Dowsr bk. Davros, VE OF OF 3 6¢ 5 eee ae 13838 | YBLNNOD AYVNIS —< 1 Cop Te 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 . A, | 00 KHe by 1]! fvep | | | at |e 3! I Soop | | | ‘ “am, “ay I] = Le fase Sol | | “P| channel ents 2G 26 | Drecettorl | Martone o | bar Be | | | 2 ar =I | Tm a + Ane rain —) | o—Mesahvre Suse Duraten | Sia ewe = SS a terpuise Duralow t— Positive Amol toda a m a Nagative Amph tde a Duce Mode selector Savtch Me , time Moda Selector $ Entered via Kblary | maar: Switch Con, aff) | im AC Power Suntech (on, Uff) a A-27 PATENTED APR 1 71973 _ 3,727,616 SHEET 1 OF 5 Fir Af. Oy) ExrERNAL TRANSMITTER rf INTERNAL PPECEIVER g Bean. a 4 32 oy a A. | 100 KHz yp —/ “ye lower | | yee oe ee Tees Sineiy_| | 4 cul : Transmitter re i Ss) “ ! ga | l r = 40— ~ onic : 4“ 3 aa | ee 4 | yfy y | | 29 c ahi Mie 2 ‘ ! 44 Digital | _ na | Lo} channel | 24S | |: g¥ 146 | Drocessor | Network i 2 | T Jrrork | a2 i p v 50 | . &O \\:. BY. a | ce ‘Te ‘att +—Asitive lee Duan, ~~) (KX Fee —Neoative Pulse Duration Skin Nerve =—S6 —nrerpulse Duration __ ae me—Lositive Amplitoda ee ae a — Negative Ample tude - | : t—Lrogram Time Duration na x P |. emis Mode Selector Sertch = T\e. he dies | | ; GDC, -0C, Bipolar) y se ed hie gga Tit ode Selector Suritcty 1a. frolary é' | Pe O° (eanbncoes ayers, Program) and Selector Switches | | Stimulate Switch” Core, off) ae | Seer AG Power Switch (on, Off) | ol INVENTOR, Herserr Hi. MEnzKes, & Buarde B. Jobnse : PATENTEDAR 7197 . 3,727,616 SHEET 2 OF § Kis? B Hewserr .. LENZKES, LIL Kire & ‘SONZNIST FL Avseerey BUNBAAT ee a eo - - "AC Power Switch (. on/ore J Program Time Ovratio 7 8 mm row Sthinviata Switeh (onforr) : | 1 | 400 Km q at 00 kHz a 100 We Tima Mode Single Cycle Program Kis bower | | |QscsMator ak " [Amplifier £0, 26 Llecton Z c Cnamevsrene lice _—_—e— ore ese oe eee ee and th Stritch Conhinvove on ee eee eee ees ee ee ere ee ae oe Bimotata Digital Tene - “peavency Me ¢ Vvider . Positive Amptifude y | P| Lata | | Diha tae? ite : «| Negative Amptitude fog ame F| Decoder Timing Pulses as atl 6 22 sy sari [700 Kile ee Positive Pulse Ovration ae eee : a: Negati ve Poise Duration Mull; ley, ae “a Covnter Jnterpulse Duration c "| none ii oesen + + 4fhe Pulse Modep? Bipolar. | ‘0SV 1By -ISY Schacter 4 +L | t Switch |-oc ‘ ' [r EERE A EO CE aera nn aa J | Bwer § NE LHS piei2 i wav O3LN31Vd 919 ‘22L'€ 63-V A-30 PATENTED APR 1 71973 -. 3,727,616 SHEET & OF § ce Se se SA at QTIOMHz l lL iy ‘ Ff ; LY G5Ra) Basic Stimulation Word from Me 3 = ieulgkeaeaiaibid = | nMtd ; Mi GHA) LZipolar Stimulating Corrent to Nerve . a ” . | MA HSC) Caipolar fosibve Stimolahng Corrent fo pred | o tA IG ey: G) Unepotar Nagahve Stimulating Gorrent +o Nerve om com aa oh > = mv ¢ We Ale) +00 Stimula hon Word from a | a . tA MG IG) #00 Stimulaton Corrent to Nerve ON ON~= Pulse Pulse A2 SF We 4G) ~DO Stimvlahon Ward from Teansmitten oO Xf. G50) -—DC Stimulation Correa? to Nerve HWerserr 0. LENZKES, 6 Lbuk b Qobnem Positwe Amplitude Word gg Lhe | tive /tive raat Ho Me Bg erthet ‘0 “26 10L / e 4 Tal | by uh eg sevectee me Grpther wis rine . } ’ 132 Is SAB 3 Give Ge Shift (des) ae Negariva p> Amp fier Psi ‘ Aime! WE Violimes)| Ie" pa ape ard DA onter | Se NOF, e (Memo Y) exe Wan Negative Amplitude nord | | Memory Preset Signal — } ode) pala) Vou" l one" —>| stunt | . Bi rai’ TAcmplebon Pulse Ganal Sonal SD oer _ ClWCK rg stmulatioa | Stimy- a ie ey - a au bit Signa ° by lation upc” Sanat ~ y Clock iy Decoder) , 2 . 3 Pek Oe : Safely n ES CLS 1 LaNOe ANON OO A yt 1&2 " 100 ki, wa) TV Preset AN ny 100 kHz —— Full Regulator Circuit tined | God | wave 42 "hog told PO ea , ) hy Corewit «100 kHz\ KoctfenMun Regulator Shunt) nN o e161 2 Ludv O31N31¥d Te-V S 30S 133KS 919'L2L'e | A-32 3,727,616 1 2 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 operab [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/brief%3Amicro_IA40385010_0585%3A2. Public record. Not legal advice.