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`‘United States Patent 11
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`fii]
`3,942,535
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`[45] Mar. 9, 1976
`Schulman
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`{75]
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`Inventor:
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`Primary Examiner—William E. Kamm
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`Attorney, Agent, or Firm—Walter C. Ramm, Charles
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`H. Thomas, Jr.; Peter J. Sgarbossa
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`[54] RECHARGEABLE TISSUE STIMULATING
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`SYSTEM
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`Joseph H. Schulman, Los Angeles,
`Calif.
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`[73] Assignee: G. D. Searle & Co., Skokie, Ill.
`ABSTRACT
`(57)
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`[22] Filed:
`July 26, 1974
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`A rechargeable tissue stimulating system with a telem-
`[21] Appl. No.: 491,974
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`étry controlled power source. A. constant current
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`Related U.S. Application Data
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`power-source acting through an induction coil exter-
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`[63] Continuation of Ser. No. 401,406, Sept. 27, 1973,
`nally located with respect to a living patient is used to
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`induce current flow in a charging circuit located be-
`abandoned.
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`neath the skin of the patient. The charging circuit, in
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`turn, recharges a battery which powers an electronic
`(521 DS.Chvvinnnnnitninnmeinennn 128/419PS
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`generator used for applying electrical pulses to stimu-
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`[58] Field of Search........ 128/2.05 S, 2.06 E, 2.1 A,
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`late living tissue in order to maintain. bodily functions
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`128/418,.419 C, 419 EP, 419 PG, 419 PS,
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`in the patient. A telemetry circuit connected to the
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`419 R, 420, 421, 422, 423, 419 PT; 307/91;
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`charging circuit provides a. magnetic output signal
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`320/31, 32, 37, 39; 328/84; 336/84
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`controlling externally. located means associated with
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`the power source. Such external means in-response to
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`this signal modulate the strength of the charging mag-
`References Cited
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`netic field, as well as provide visual or audio indica-
`UNITED STATES PATENTS
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`tion of proper charging as well as the proper position-
`7/1965 Waller. 128/419 PG
`3,195,540
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`
`. 128/2.06 E
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`ing of the external power source with respect to the
`
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`3,409,007 11/1968|Fuller... :
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`3,426,748 2/1969.Bowers. .. 128/419 PS
`implanted charging circuit, completion of the proper
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`3,454,012 7/1969.Raddi....... . 128/419 PG
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`charging interval’ to restore the amount of current
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`10/1971
`‘Ragsdale... cesses 128/2.06 A
`3,612,041
`used, and improper charging.
`
`
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`FOREIGN PATENTS OR APPLICATIONS
`5/1966
`Fance...scceccerenterees crane 28/419 PS
`87,174
`
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`OTHER PUBLICATIONS
`Evalenko et al., “Medical. Instrumentation,” Mar-
`
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`Apr., 1967, pp. 13-16.
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`[56]
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`~
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`11 Claims, 12 Drawing Figures
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`CHARGING
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`CIRCUIT
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`10
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`TIMING
`MEANS
`él
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`a
`TRANSDUCER
`“14
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`TELEMETRY
`CIRCUITe
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`GOOGLE AND SAMSUNGEXHIBIT 1006
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`GOOGLE AND SAMSUNG EXHIBIT 1006
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`U.S. Patent March 9, 1976
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`Sheet 1 of 9
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`3,942,535
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`6‘9ls
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`3,942,535
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`FIG.2
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`U.S. Patent March 9, 1976
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`U.S. Patent March 9, 1976
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` Sheet30f9
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`3,942,535
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`STIMULATOR
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`TISSUE
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`FROMFIG.2
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`FIG.3
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`U.S. Patent March 9, 1976 Vep'OlaOL
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`U.S. Patent
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`Sheet 5of9 3,942,535
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`U.S. Patent
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`Sheet 60f9
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`3,942,535
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`U.S. Patent March 9, 1976
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`3,942,535
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`U.S. Patent March 9, 1976
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`5
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`3,942,535
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`2
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`It is a further object of the present invention,utilizing
`‘RECHARGEABLE TISSUE STIMULATING -
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`preferred embodiments thereof, to provide and auto-
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`matically maintain a record of charging and discharg-
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`ing of the tissue stimulating system. In this way a physi- .
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`cian avoids havingto rely on the memory ofhis patient
`This is a continuation, of application Ser. No.
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`to determine the extent to whicha chargeexists in the
`401,406, filed Sept. 27, 1973 and now abandoned.
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`rechargeable voltage source in the pacer.
`This invention relates to a rechargeable tissue stimu-
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`._ A further object is to employ a system facilitating the
`lating system for providing a charge to a voltage source
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`proper positioning of the external charging head con-
`implantedinaliving being, and for regulating recharg-
`net 0
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`taining the power source induction coils with respect to
`ing of the voltage source through the use of a telemetry
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`circuit.
`the implanted charging circuit. This insures that proper
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`positioning of the charging head is initially achieved,
`Tissue stimulating systems currently find a principal
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`since a positive signal
`is generated persuant to this
`application in maintaining heart rhythm in a living
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`invention to notify the patient once proper positioning
`patient through an implanted electrical pulse generat-
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`has been achieved.In addition, utilizing the special vest
`ing source. While such devices are used almost exclu-
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`of this invention, proper positioning, once achieved,is
`sively as cardiac pacers, they may also find other appli-
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`automatically maintained for the duration of the charg-
`cations, including the actuation of prosthetic devices,
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`and correction for respiratory and circulatory disfunc-
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`ing interval.
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`tions.
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`It is a further object, utilizing the improved circuitry
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`of this invention, to provide electrical shunt regulation
`When utilized for the purpose of maintaining an ac-
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`in the charging circuit in order to prevent the voltage
`ceptable heartbeat in a patient, a catheter is passed
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`and current applied'to the rechargeable voltage source
`through a vein and wedged into the heart muscle at the
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`from becoming too great. The circuitry of this inven-
`bottom of the right ventricle. The catheter leads to a
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`tion also prevents the rechargeable voltage source from
`pulse generator operated by a d.c. voltage source and
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`being drained of powerif a short were to occur in the
`located externally of the rib cage beneath the surface of
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`charging circuit.
`the skin of the patient. To avoid the physical dangers
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`In a broadaspect. this invention is a rechargeable
`and psychological distaste for frequent periodic opera-
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`tissue stimulating system comprising: an implantable
`tions to replace the voltage source, it has been found
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`electrical
`tissue stimulator including a rechargeable
`highly desirable to utilize a cardiac pacer employing a
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`d.c. voltage source for powering an electronic genera-
`rechargeable voltage source. A very suitable voltage
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`tor used for applying electrical pulses to stimulate liv-
`source has been found to be a single cell nickel-cad-
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`ing tissue in order to maintain bodily functions of a
`mium battery capable of producing a nominal
`.1.25
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`living subject into whichit is implanted; an implantable
`volts with a capacity of 200 milliamp hours. Such a
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`charging circuit positioned beneath the skin of a living
`voltage source will have a useful life of approximately.
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`subject and including an induction coil with rectified
`10 years. Other conventional voltage sources for pace-
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`makers have a much shorter useful life averaging ap-
`output leads connected to said tissue stimulator; an
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`external electrical charging power source including an
`proximately 22 months.
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`induction coil for positioning external to a living sub-
`With a rechargeable voltage source and with a reduc-
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`ject and proximate to the induction coil of the implant-
`tion in the physical size of cardiac pacers, it has be-
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`able charging circuit; a telemetry circuit connected to
`comevery difficult to accurately locate the charging
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`said implantable charging circuit for detecting the mag-
`circuit for the pacer andto insure that recharging actu-
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`nitude of a charging current received by said d.c. volt-
`ally does occur when the power source for recharging
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`age source and providing a magnetic output signal to
`the battery is in operation. It is particularly significant
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`said external powersource indicative of the magnitude
`in this regard that recharging is a brief but frequent task
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`of the charging current received by said d.c. voltage
`whichis desirably performed by the patient at his con-
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`source; and, a transducer forming a part of said exter-
`venience. Since charging usually does not occur in the
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`nal power source for converting said magnetic output
`presence of a physician, the physician is unableto posi-
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`signal to an electrical control signal, and wherein said
`tively determine that proper periodic charging has oc-
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`external charging powersource additionally includes a
`curred due to physiological changesin the patient, such
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`voltage control actuated by said controlsignal to adjust
`as increased pulse rate. Indeed, even if recharging were
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`the strength of the magnetic field applied tosaid im-
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`plantable charging circuit.
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`cian would not be able to ascertain with any degree of
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`In a morespecific application, this invention may be
`certainty whether or not the rechargeable battery actu-
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`considered as a rechargeable cardiac pacing system for
`ally received the appropriate charge.
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`maintaining a source of stimulating pulses to the heart
`Accordingly, it is an object of the present invention
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`of a patient comprising in combination: an implantable
`to substitute a telemetered signal indicative of proper
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`cardiac stimulator for positioning beneath the skin of a
`charging of the implanted voltage source for the sub-
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`patient equipped with a rechargeable d.c. voltage
`jective observations of either the patient or his physi-
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`source, a pluse generating circuit, and catheter means
`cian. In this manner, insufficient recharging or a total
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`equipped with electrodes for applying stimulating
`failure to rechargeis detected by the chargingcircuitry
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`pulses to the heart of the patient; an implantable charg-
`itself, and a signal is returned to the recharging power
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`-ing circuit for positioning beneath the skin of a patient
`sourceto indicate the charging status of the tissue stim-
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`and including an induction coil with rectified output
`ulating system. This signal governs the operation of the
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`leads connected to said d.c. voltage source; an external
`recharging unit by extending the charging interval to
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`electrical charging power source including an induc-
`compensate for periods during which. improper charg-
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`tion coil for external positioning with respect to the
`ing occurs, and by indicating the termination .of the
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`patient proximate to the induction coil of the implant-
`charging interval as well as the failure of the unit to
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`able charging circuit; a telemetry circuit connected to
`properly recharge.
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`signal is generated by the power source 13 for recharg-
`said implantable chargingcircuit for detecting the mag-
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`ing the battery 15 ofthe tissue stimulating system. This
`nitude of a charging current received by said d.c. volt-
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`frequency is preferred because it is a low frequency
`age source, and providing a magnetic output signal
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`thatis also above audio; however, any frequency which
`indicative thereof, and timing means responsive to said
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`will permit energy passage through tissue without ex-
`magnetic outputsignal including a register for storing a
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`cessive loss may be used. The entire waveform of the
`signal indicative of time elapsed during which the mag-
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`current induced in the induction coil 17 is rectified by
`netic outputsignal indicates that the charging currentis
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`the diodes CR1 and CR2 to producea d.c. output. This
`at least as great as a predetermined minimum operating
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`produces a positive voltage at the cathodesof the di-
`level. In a more precise application, the magnetic out-
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`odes CRI and CR2 relative to the center tap of the
`put signal can be used to indicate the time elapsed
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`induction coil 17. Charging current passes through the
`during which the charging current is maintained within
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`current sampling resistor R9 and through the diode
`preset upper and lowerlimits.
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`CRStothetissue stimulator. The return currentpath is
`This invention may be described with greater particu-
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`through the electrical lead 52 back to the center tap of
`larity by reference to the accompanying drawings in
`the induction coil 17.
`which:
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`The telemetry circuit 12 is comprised in part of the
`FIG. 1 is a block diagram of the tissue. stimulating
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`transistors Q2 and Q3, which together form a free-run-
`system,
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`ning multivibrator coupled through capacitors C3 and
`FIG. 2 is a schematic electrical diagram of the charg-
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`C4, Bias current for transistors Q2 and Q3 comes from
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`ing and telemetry circuit of FIG. 1,
`the collectors of transistors Q4 and QS. The current to
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`FIG. 3 is an electrical schematic diagram ofa tissue
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`the bases of transistors Q2 and Q3 and capacitors C3
`stimulator according to FIG. I,
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`and C4 controls the frequency of the multivibrator.
`FIG. 4 is an electrical schematic diagram of the
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`The collector current of Q4 and QSis controlled by the
`charge head and powersource circuits of FIG. 1,
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`voltage drop across the series combination of the emit-
`FIG. 4A is an electrical schematic diagram of a por-
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`ter resistors R4 and RS and the emitterbase junction of
`tion of the transducerof FIG.1,
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`transistors Q4 and Q5. The voltage across the emitter
`FIG. 4B is an electrical schematic diagram of the
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`resistors R4 and R5 is almost equal to the voltage
`remaining portion of the transducer of FIG. 1,
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`across the current sampling resistor R9 because the
`FIG. 5 is an electrical diagram illustrating various
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`baseemitter voltage dropsof transisotrs Q4 and Q5 are
`additional features of the tissue stimulating system of
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`each close to the base emitter voltage drop oftransistor
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`FIG. 1,
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`Q6. A small amount of current is permitted to flow
`FIG.6 is a front perspective view of a portable power
`source and transducer.
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`through transistor Q6 by its collector resistor R7 in
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`order to permit a base-emitter voltage drop in transis-
`FIG.7 is a rear perspective view of the power source
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`tor Q6 that will vary with temperature in the same way
`and transducerof FIG.6,
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`as do the base emitter voltage drops in transistors Q4
`FIG.8 illustrates the character of the special vest of
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`this invention.
`and Q5. Thusas the voltage across current sampling
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`resistor R9 increases, a proportional voltage increase
`FIG. 9 illustrates the variation of the magnetic charg-
`will occur across resistors R4 and RS.Since the collec-
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`ing field with respect to time.
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`tor current through transistors Q4 and Q5is deter-
`FIG. 10illustrates the structural configuration of the
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`mined by the voltage across R4 and R5, the current
`implanted portions of the tissue stimulating system of
`FIG. 1.
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`through resistor R9 controls the frequency of the multi-
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`vibrator in an almost linear fashion. The current flow
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`Referring now to FIG. 1, there is illustrated a re-
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`from the collector of transistor Q2 is used to turn on
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`chargeable tissue stimulating system comprising a
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`and off the transistor Q1 at the frequency of the multi-
`chargingcircuit 10 including a telemetry circuit 12 and
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`vibrator. Every time Q1 is turned on,alternate sides of
`a tissue stimulator 11 including a catheter 16, all de-
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`induction coil 18 are shorted for the separate halves of
`signed for implantation into the body ofaliving patient.
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`each cycle of the 21 kilohertz charging signal whenit is
`The system further includes a power source 13 with a
`transducer 14 in the form of a detector circuit for re-
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`present. Thus, when QI is turned on, the 21 kilohertz
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`field is loaded down by the equivalent of a shorted coil
`charging and for verifying the charging condition of the
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`equal to one side of inductor 18. The 21 kilohertz field
`implanted portions of the tissue stimulating system.
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`from the power source 13 is thereby alternately loaded
`The powersource 13 employs a poweroscillator circuit
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`and unloadedat a rate determined by the free-running
`104 to generate a 21 kilohertz electric field which pow-
`multivibrator. Connection of the transistor QI to the
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`ers the charge head 42. Part ofthis field is detected on
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`induction coil 18 is completed through the diodes CR3
`the charging head 42 andsentto the detectorcircuit, or
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`and CR4,with the transistor Q1 acting as a switch to
`transducer 14. The output of transducer 14 is used to
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`alternately vary the load of the chargingfield.
`control the poweroscillator output energy andis used
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`Magnetic field strength between the induction coils
`to drive the timing means 61, which includes a timing
`and indicatorcircuit.
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`of the power source and charging circuit is illustrated
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`with respect to time in FIG. 9. The interval ¢ during
`The charging circuit is illustrated in FIG. 2 and in-
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`which loading of the charging field is increased (and
`cludes two induction coils 17 and 18. The output leads
`51 and 52 from the induction coil 17 are rectified and
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`field strength thereby reduced) varies with the fre-
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`are connected to the tissue stimulator of FIG. 3. The
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`quency of operation of the telemetry circuit. As has
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`previously been explained, the telemetry frequencyis
`induction coils 17 and 18 are broad band frequency
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`controlled by the transistors Q2 and Q3, which are in
`coils, not tuned coils. This is advantageousin that the
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`system does not haveto becritically tuned and may be
`turn controlled by the current through the current
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`sampling resistor R9. As the charging field energy in-
`rechargedata different frequencyif that is found desir-
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`creases, the initial current through resistor R9 is the
`able (e.g. to avoid a specific interference with external
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`charging currentto the battery 15 ofthe tissue stimula-
`nearby electrical equipment). A 21 kilohertz charging
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`65
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`Page 12 of 19
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`Page 12 of 19
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`‘tors R4 or R3 and induction coil 18 will not affect the
`tor, since the shunt current regulator is notinitially
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`turned on. The shunt current regulator is comprised of
`recharging of the battery 15.
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`The manner of operation of the magnetic output
`the current shunting transistor Q7 and the shuntresis-
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`signal from the telemetry circuit 12 to the transducer
`tor R8, which biases the base of transistor Q7.. The
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`shunt current regulator maintains a constant current
`14 may be explained as follows. The magnetic flux
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`existing between the induction coils of the external
`through the ‘resistor R8, which is connected in series
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`electrical charging power source 13 and those of the
`with the rectified output leads 51 and 52. The zener
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`diode VR1, prevents the rectified output voltage on the
`implantable charging circuit 10 varies in intensity in a
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`leads $1 and 52 from becomingtoo great if battery 15
`regular manneras illustrated in FIG. 9. The extent to
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`should open. This prevents dangerously high stimula-
`which the magnetic field generated by the power
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`tion rates from developing in case of an open in that
`source 13. is loaded determines the maximum ampli-
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`tude of the magneticfield. Thatis, the greater the load-
`part of the tissue stimulator which is in ‘series with
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`battery 15 and thereby obviates the possibility of dam- —
`ing by the charging circuit (and telemetry circuit) the
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`age to the tissue being stimulated from excessive rates.
`smaller will be the amplitude of the magnetic field. The
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`frequency of the rapid loading and unloading that oc-
`As the current through resistor R8 increases in the
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`curs will be in direct proportion to the current being
`operation of the shunt current regulator, the voltage
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`differential at the base emitter junction of transistor Q7
`drawn throughthe resistor R9. Since all current up to a
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`maximum level will. flow through the rectified output
`will also increase, which will cause transistor Q7 to
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`conduct to a greater extent and thus to divert some of
`leads 51 and 52 to charge the battery 15, any current
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`less than this maximum passing throughresistor R9 is
`the current which is passing through the resistor. When
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`indicative of inadequate chargingof the battery 15.It is
`Q7 starts to conduct,
`it tends to keep the current
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`the telemetry circuit 12 (previously described) which
`through resistor R8 relatively constant. If transistor Q7
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`senses this condition and signals the condition back to
`is maintained at a constant temperature, resistor R8
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`the induction coil 21 by modulating the frequency of
`can be selected for regulation at a predetermined cur-
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`the amplitude peak fluctuation of the charging field.
`rent. For example, if one wanted to maintain a charging
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`Thatis, with inadequate charging,the period ¢ of ampli-
`current of 40 milliamperes into the battery. 15, and the
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`tude peak variation in FIG. 9 will be inordinately long.
`base-emitter voltage drop required to initiate conduc-
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`tance in transistor Q7 is 0.4 volts, one would select a
`As the induction coils of the power source are moved
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`resistance value for resistor R8 such that 40 milliam-
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`closer to a proper charging relationship with respect to
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`the induction coil of the implanted chargingcircuit, the
`peres would produce a 0.4 voltage differential between
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`the base-emitter leads of transistor Q7. If the current
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`period ¢ in FIG. 9 will decrease. That is, the frequency
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`of magnetic field strength peak amplitude will increase
`began to increase beyond 40 milliamperes, transistor
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`when this frequency increases sufficiently to indicate
`Q7 would conduct to an increasingly greater extent.
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`that the maximum charging current across resistor R9
`Such an increasing load would alter the telemetry sig-.
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`has been reached. Theelectrical control signal gener-
`nal created by the transistor Q1. As long as the current
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`ated in transducer 14 by the magnetic output signal
`through resistor R9 remains at 40 milliamperes or
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`from the telemetry circuit 12 will produce changes in
`above, charging of the battery 15 is considered to be
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`the regulation of the power source 13. These changes
`proper. The diode CR5 prevents any type of short from
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`developing between leads 51 and 52 in the region be-
`include altering the condition of the charging status
`40
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`tween inductors 17 and 18 and diode CRS.
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`indicating light emitting diodes 26 and 27,altering the
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`As a further safety feature, the implantable charging
`activation condition of the buzzer 28, generating a
`circuit of FIG. 2 utilizes a zener diode VRI set at a
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`signal on circuit 59 to alter the output of the current
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`predetermined maximum operating voltage and con-
`control means 60 and turning on the timing means 61
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`nected across the rectified output leads 51 and 52. This
`to actuate register 31 to indicate that proper charging
`45
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`‘ maximum operating voltage would typically not exceed
`of the tissue stimulating system is occurring.
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`five volts, and more desirably would not exceed 3.6
`The telemetry circuit and transducer depicted in the
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`drawings operate by loading down an existing electro-
`volts. This feature provides a positive protection
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`against high voltage ever existing across the leads 51
`magnetic field with a telemetry circuit, and governing
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`and 52, and so provides another measure of safety
`operation of the power source 13 in accordance with
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`against an inordinately large stimulus rate from occur-
`the effect that the telemetry circuit 12 has on the elec-
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`tromagnetic field induced by the power source 13. It
`Ying at catheter 16, and thereby prevents the occur-
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`should be realized, however, that there are other forms
`rence of such dangersas triggering ventricularfibrilla-
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`of magnetic output signal generation and other forms
`tion when the heart is the tissue stimulated, an occur-
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`rence which usually results in the death ofthe patient.
`of transducers appropriate for the different types of
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`As previously explained, the diode CRS5 in series with
`magnetic output signals. For example, (1) an electro-
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`oné of the rectified output leads 51 or 52 from the
`magnetic signal could be transmitted back to a trans-
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`chargingcircuit prevents the cell 15 from being drained
`ducer at a frequency different from the charging fre-
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`due to a short in the charging circuit, such as. might
`quency, (2) the power source could be turned off and
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`on, and a short signal indicative of the previous charg-
`occurin the transistors Q6 or Q7 or the capacitor C1.
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`A separate telemetry induction coil 18 is utilized in
`ing. current through resistor R9 could be returned to a
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`transducer during the off period, or (3) a pietzoelectric
`addition to the induction coil 17 of the electrical charg-
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`ing power source for safety reasons, although both of
`‘crystal could be used in the telemetry circuit to gener-
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`ate an acoustic output signal indicating the degree of
`the coils 17 and 18 may be considered:as part of the
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`induction coil of the implantable charging circuit. The
`charge.
`65
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`‘In addition, different parameters can be used as sig-
`separate coils 17 and 18 are used to prevent any trou-
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`nificant variables in the magnetic output signal. A sig-
`ble that.develops in the telemetry portion of the circuit
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`from inhibiting proper charging of the cell 15. Thatis,
`nal frequency modulation linearly related to parame-
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`any short or open circuits that occur betweenthe resis-
`ters such as charging current might be employed. Two
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`60
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`Page 13 of 19
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`Page 13 of 19
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