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Publication numberUS3457463 A
Publication typeGrant
Publication dateJul 22, 1969
Filing dateJul 7, 1965
Priority dateJul 7, 1965
Publication numberUS 3457463 A, US 3457463A, US-A-3457463, US3457463 A, US3457463A
InventorsLewis Balamuth
Original AssigneeLewis Balamuth
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and apparatus for generating electric currents of small magnitude
US 3457463 A
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Description  (OCR text may contain errors)

-J l U "JCQ DH 1969 L. BALAMUTH 3,457,463

METHOD AND APPARATUS FOR GENERATING ELECTRIC CURRENTS OF SMALL MAGNITUDE Filed July 7, 1965 5 Sheets-Sheet l L uov M).

SWITCH PRE. M 1 AMPLIFIER i so souno OUTPUT SIG H2 HI V A.- no? I06 I00 I09 m m l H! "I 0000041 0 U f: aa iii a F! a -uew, P: n "i'ir' i! w 'Pl' E m u in i'i iii ili III ill ill iil Iiilil lllllliiliiiililillll Iiilli iliiiiiii no I08 I07 INVENTOR Ff .15 LEWIS BALAMUTH M BY 5% MM ATTORNEYS July 22, 1969 L BA MUTH 3,457,453

METHOD AND APPAR ATUS R GENERATING ELECTRIC CURRENTS OF SMALL MAGNI'IUDE Filed July 7, 1965 5 Sheets-Sheet S LEWIS BALA MUTH BY gw pg ATTORN YS July 22, 1969 L. BALAMUTH 3,457,463

METHOD AND APPARATUS FOR GENERATING ELECTRIC CURRENTS OF SMALL MAGNITUDE Filed July 7, 1965 5 Sheets-Sheet. 3

F1 q- J] m I04 I05 I07 I08 lOl M v IOU MM 1 1 1w 1 r" SIGNAL FREQUENCY INVENTOR LEWIS BALAMUTH FI 7d ATTO NEYS United States Patent Office METHOD AND APPARATUS FOR GENERATING ELECTRIC CURRENTS OF SMALL MAGNITUDE Lewis Balamuth, 29 Washington Square W., New York, N.Y. 10011 Continuation-impart of application Ser. No. 188,997, Apr. 2, 1962. This application July 7, 1965, Ser. No. 470,095

Int. Cl. H01h 47/20 US. Cl. 317-123 i 14 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for converting vibrations to electrical energy for relay operation. A reed tuned to a selected frequency of vibration has an element associated therewith which produces an electrical output signal in response to stress produced in the reed as the result of vibration thereof. Such element may be magnetostrictive, piezoelectric, or transistor means. A plurality of reeds mounted in contiguous relation may be provided each reed being tuned to a respective frequency over a selected range. One contemplated use in the energization'of a bank of lamps of different colors, each corresponding to a respective reed frequency, thus producing a color display uniquely corresponding to the different sounds in a musical composition. V

This invention is a continuation in part of my applicacation Ser. No. 188,997, now Patent Number 3,204,513, dated Sept. 7, 1965.

This invention relates to a method of and to apparatus for generating electric currents of small magnitude. It also relates to sonic switching and to sonic switching apparatus in which a switch is made responsive to a particular sound or tone occurring alone or admixed with others. It also relates to electromagnetic devices operating on similar principles to respond to a particular frequency which may occur in an alternating current of many frequencies. The invention also includes several novel instruments";'some of which are sonically operated and others of which are electromagnetically operated.

It is desirable tooperate an instrumentality, for instance a switch, when a sound, for instance a musical note, appears in a cacophony or resonant band of other sounds. It is also desirable to operate such an instrumentality when a particular note disappears from such a band. It is highly desirable that microphones and similar electrical instruments should be eliminated and replaced by instruments which respond directly and selectively to particular tones. It is an object of this invention to devise methods and means of achieving these desiderata.

It is an object of the invention to make devices which are energized by means of-an incoming vibration of one selected frequency in a narrow band of frequencies either sonic or electrical. By sonic we mean sounds of all wave lengths Whether or .not audible to the human ear. By the terms electrical vibration and electrical oscillation we include all types-of such oscillation regardless of whether they are commonly called alternating, oscillating, or interrupted as a means of distinguishing one from another. Another object is to prepare a-device having as many selected resonant frequencies as desired in the band of frequencies involved in the incoming signal.

Another object is to employ the peak oscillatory strain in a tuned reed to generate transducing effect in a magnetostrictive current generator, a piezoelectric current generator, or a transistor to produce an output signal when the tuned reed oscillates in harmony with a vibratory input source.

The objects of the invention are accomplished, generally speaking, by a method of generating electric currents of small magnitude which comprises mountinga generator of the class of magnetostrictive, piezoelectric, and

transistors at a point of major stress of a tuned reed,

placing the reed in an environment capable of transmitting oscillations to which the reed responds, and deliver- 'ing the current generated when the reed vibrates in response to such oscillations to operative instrumentalities. As to apparatus the invention is accomplished, generally.

speaking, by apparatusfor generating electric currents I i The invention can be applied to apparatus whichuses sound waves as the exciting cause and to apparatus which uses electromagnetic waves The forms of the invention in which sound waves are employed will be described first.

The above and further objects and novel features of the j I present invention will morefully appear from the'following detailed description when the same is read in connection with the accompanying drawings. It is tow be expressly understood, however, that the drawings are for the" purpose of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawings, wherein like reference characters re fer to" like parts throughout the several views,

FIG. 1 is a diagram ofan apparatus employing a novel resonant generator through a preamplifier to operate a switch to turn off a constantly burning light;

FIG. 2 is a vertical section throughanovelresonantv generator of electric current? I FIG. 3 is a vertical section through another form of resonant current generator; 1

FIGS. 4 and 5 are details showing the construction of in vertical secnovel tuned reed generators,-.F-IG. 4 being tionand FIG. 5 in vertical elevation;

FIG. 6 illustrates a means of mounting the tuned reed; FIGS. 7a and 7b collectively show in vertical elevation the respective end portions of a generator pile "adapted to the operation of numerous apparatusby'ditferent frequencies; FIG. 7a illustrates the left end of the apparatus seen from the south and FIG. 7b illustrates the right end of the same apparatus seen from the north;

FIGS. 8a and 8b are details of .the metallic'coating shown in FIG. 7; v

FIG. 9 is a vertical elevation of a to an input electrical signal;

FIG. 10 is a plan view of an instrument adapted to select individual frequencies from an input signal of mixed frequencies; FIGS. 11 and 12 are alternative details" in vertical section through the apparatus of FIG. 10; and

FIG. 13 is a vertical, diagrammatical elevation of a transistor-type switch.

FIGS. 2 and 6 are transferred from the identified parent application.

The resonant generator of FIG. 2 includes a dielectric base 20 from which an embedded post 21 rises to support a permanent magnet 22. A magnetostric'tive laminate 23 is mounted on the base with its tines 24, 25 in close proximity to the poles of the magnet. The tines of the laminate are composed of metal which will carry magnetic flux, for instance nickel. The'fork is fixed to the base by I 3,457,463 1 Patented July 22,1969, I

generator responsive tiny feet 24 which elevate the body of the fork above the base. A coil 26 encircles one tine of the fork, one lead of the coil being connected to ground 27 and the other lead 28 being connected to a preamplifier as indicated in FIG. 1. A condenser 29 separates the two leads.

When this instrument is placed in an environment containing sounds it will vibrate harmonically when it receives sounds which are at its pitch. The vibration of the ends of the tines in the flux flowing from the magnet will generate a current in the coil 26 which will be delivered through lead 28 to the preamplifier of FIG. 1 or to some other operative instrumentality.

In FIG. 1 resonant generator of FIG. 2 is indicated by numeral and the preamplifier is shown to be connected by a lead 11 to a coil 12, the circuit being completed by grounds 13, 14. A light 15 is shown as continuously burning by an input from a 110 V. AC. source through a switch 16. When the coil 12 is activated it attracts the arm of the switch, overcomes the pull of the spring 17, which biases the arm to closed position, and turns off the light.

A plurality of these units, differently tuned, may be used to show in lights the appearance of different sonic frequencies. For instance, one U-shaped magnetostrictive laminate may be tuned to 440 vibrations per second by careful reduction of its ends. The post 21 does not touch the fork and may be made of porcelain or plastic. The magnet may have its ends coated with a thin film of insulation, for instance plastic foam. The ends of the magnet may be spaced from the ends of the fork by a narrow gap, for instance .001 inch. The coil 26 encircles the base of one of the tines and is connected to a condenser, forming an electronic band pass filter at a frequency which is the fundamental frequency of the tuning fork. In this form of the invention microphones are needless as a multiplicity of tuning forks, each tuned to its own frequency, and connected to its own coil and condenser, respond directly to sonic frequencies corresponding to their own specific frequencies and turn on and off each its own light.

In FIG. 3 a thin glass reed 30, tuned to a selected pitch is mounted at its foot in a ferrite support 31 which has a thin central section 31a located at the zone of maximum stress developed by the reed when it vibrates in response to an exciting tone. A magnet 32 has its poles in close proximity to the enlarged top and foot of the ferrite base in which the reed 30 is mounted. A dielectric support 33 supports a coil 34 at the zone of maximum mechanical stress. When the reed vibrates in response to sonic vibrations of its own pitch, a current is generated in the coil, passing through the conductor 28 as an output signal, the other side of the coil being connected to ground through lead 27.

In this type of apparatus very thin glass, such as microscope cover glass, may be used for the reed, pitch being determined by length, width and thickness. This provides low impedance to match the air wave. When the reed is to be tuned to very precise pitch it is sometimes useful to apply a small spot of mirror silver to the glass, the size of the spot when being reduced until the chosen frequency is attained. The reed is attached at its base to a thin magnetostrictive strip of metal, indicated in FIG. 3 by the ferrite base. If desired the head and foot of the element 31 can be made separate from the element 31a, which may be a separate magnetostrictive piece. This is sometimes desirable when great flexibility of the magnetostrictive element is desired. A magnetic biasing flux is provided in the magnetostrictive strip in either case, so that an alternating magnetic flux occurs in synchronism with the mechanical vibrational frequencies of the reed. The alternating magnetic flux arises whenever a mechanical alternating stress is induced in the magnetostrictive strip. The pickup coil 34 which surrounds the strip has induced in it a current of the same frequency as the vibration of the reed and the voltage of the current becomes the signal which activates the operative instrument. The reed, the magnetostrictive strip which supports it, the magnet, and the coil constitute a total magnetostrictive pickup system which is responsive to sonic vibrations of its own pitch.

The magnetostrictive strip is placed near the nodal point of vibration so that the stress will be a maximum for a given vibration of the reed.

When the magnetostrictive element 31a is separated from 31 it may be composed of a ferrite ceramic wafer. For some uses this construction is preferred because it imparts some increase in el'ficiency.

Different methods and means of mounting the ceramic wafer are shown in FIGS. 4 and 5. In FIG. 4 the supporting block 40 is provided with a slot 41 in which the ceramic wafer 42 is cemented. The ceramic wafer bears silver coatings 43, 44 on its opposite sides, one of these being connected to ground and the other to some operative instrumentality. Fixed to the upper end of the ceramic wafer at 45, for instance by cement, is the tuned reed 46. The wafer 42 may be of ceramic, piezoelectric material. When some vibratory force in the environment of the reed compels the reed to vibrate, the resonant frequency component of this force will cause the piezoelectric wafer to vibrate with bending vibration. It is placed in the region of highest alternating stress and a maximum electrical voltage is generated across the faces of the wafer at the resonant frequency of the reed.

It is apparent that this device is a very sensitive switch wherein a circuit will be operated selectively by one narrow band not a whole range of frequencies.

In FIG. 5 is an important case wherein the active transducing element serves as its own amplifier and is made of semiconductor, piezo-resistive and transistor-like material such as silicon or germanium. In this structure the base 50 mounts a tuned reed 51 to which a transistor 52, properly encapsulated, has been cemented at a region of high alternating stress. Leads 53, 54, 55 are the usual transistor leads such as are used in transistor amplifier elements. In this case the transistor operates somewhat as a solid state, semiconductor strain gage with the regular transistor amplifier circuit. The alternating, amplifier stresses induced in the transistor material will appear in amplified form in the transistor plate circuit and the amplified current may be used to operate a relay switch. The extremely minute sizes in which transistors may be made makes them particularly effective, as the dampening effect is low, and the dampening effect of the added compliance on the induced stress is largely eliminated, providing great sensitivity.

FIG. 6 shows a form of the invention in which the resonant reed 61 is mounted in a slot 62 in a base 60 operating by bending and flexing and yielding a low speed of wave motion, much less than the speed of sound in air, but providing a specific impedance matching air waves with etficiency.

In the musical-optical instrument the object is to turn the lights on the screen on and off synchronously with the various sounds being received. Each switch element is to operate when the microphone receives a sound having a mid-band frequency corresponding to a note of the 88-note piano scale. A good type will employ the fundamental resonant bending vibration frequency of a reed fixed at one end and free at the other. The reed will be of a magnetostrictive material such as nickel, Monel, or steel. The reed 61 is mounted in a base 60 and it will have a radius of gyration I being the length of the reed in cm. The application of this formula, the reed being nickel and 2 being .025 cm. produces the following table, Fni being in cycles per second,

Fni

l in em.

1st octave 2nd octave..

8th octave For lower frequencies the length of the reeds can be shortened by using appropriate thickness. For example, one half the length of the table with a width of .005 instead of the .010 on which the table was computed, produces lengths of 10.36, 7.34 and 5.18 for the first three octaves respectively.

The reeds will respond to all frequencies of sound but they will vibrate selectively with a bending vibration at the frequencies F and also at the overtones of their own fiexural vibrations.

FIGS. 7a, 7b, 8a and 8b illustrate an instrument for generating currents by sound waves for the activation of a plurality of instruments. A base 70 is provided with a slot which receives the back 72 of a comb 71, gripping it tightly as in FIG. 6. The comb may be cemented in place if desired. Spaced teeth 73 project upwardly from the comb, being integral with it and similar in length and construction to part 42 of FIG. 4. Reeds f f tuned to different pitches are cemented to the teeth of the comb. One side of the comb is completely silvered as shown in FIGS. 7b and 8b, and a single lead 74 connects the silver to ground. The opposite side of the comb has separate silvering 75 for each tooth, the silvered areas being separated by blank spaces 76. Each area 75 is connected by a lead 77, 77' etc. to an operative instrumentality such as a relay or a preamplifier.

One useful and compact form of a comb involves thin, wafer like ceramic of the type used in piezoelectric constructions. The reeds may be of glass, metal or other vibratory material. The base is nonconductive, for instance Bakelite or other plastic. Thereeds are of high-Q elastic material and their dimensions are such that each reed responds to a selected frequency. For example, the reeds can be tuned to the tones of a musical instrument so that one reed will respond harmonically when a vibration of 440 per seconds is received. The finished instrument is a multi-resonant generator of electric signals which will selectively pick out frequency bands from a sound wave and convert them into electrical output signals. The active principle as described is piezoelectric.

In FIG. 9 base 90 supports an A.C. electromagnet 91 including a coil 92 and core 93 on posts 94. An input A.C. current, containing many frequencies, flows through the coil. Mounted on the base is a composite reed of microscope glass 95 attached to a piezoelectric wafer 96 silvered on opposite sides, one silvered face being connected to ground and the other to output. The silvered patches 97, 98 are insulated from each other and are connected to different operative instrumentalities. A ceramic wafer of piezo type is satisafctory for such use when silvered on its opposite sides. A small metallic piece 99 is attached to the upper end of the reed 95 opposite the core 93. Perrite or other magnetically responsive metal is satisfactory. The period of the reed will be the composite of the metal, the glass and the ceramic. It will be recognized that the silvered faces of the piezo wafer are located at a region of high stress of the composite reed.

When the current flows, an alternating magnetic field is created in the ferrite core which supplies an A.C. force v to the magnetic base on the reed and the resonant frequency component of this force will cause the reed to vibrate with bending vibration. When the wafer is placed in the region of highest alternating stress a maximum electrical voltage will be generated across the faces of the wafer at the resonant frequency of stimulation of the reed. The metallic base on the reed is preferably a permanent magnet.

FIGS. 10, l1 and 12 depict an instrument in which the foregoing principles are utilized. A magnetic core 100 made, for instance, of laminated transformer core steel, is provided with longitudinal channels 101, 102 which lie between a central ridge 103 which has a narrow but flat crest 104, and somewhat lower walls 105, 106. What are, in effect, double reeds 107, of different lengths, are balanced on the crest and attached thereto by a spot of cement or otherwise. These reeds may be of glass, metal such as aluminum, or other flexible material. To the lower faces of the reeds smaller ferrite magnets 108 are attached so as to lie over the sides or walls 105, 106, from which they are separated by small gaps of the order of a few thousandths of an inch in most cases. Within the channels 101, 102 is located a coil 109 which receives an input signal through lines 110. Hypersil or ferrite are high-Q elastic materials which may be used instead of glass, aluminum, and beryllium-copper for the reeds. Each reed is tuned for a different bending frequency of vibration. The small magnets 108 may be soldered, cemented or welded to the reeds. An alternating force will be produced by the alternating magnetic flux in the core which is, in turn, produced by the alternating current in the exciting coil. The coil may, itself, be attached to a microphone M. At the point of attachment of the reeds to the crest there is a region of peak alternating stress whenever the reed vibrates. In the form of the invention shown in FIG. 11 a barium zirconate or other piezoelectric disc 110 is bonded to the reed above the crest 104. This disc has an upper silvered surface 111 which is attached to a reed 112 which carries the output signal which is generated by the flexing of the reed in response to corresponding components in the A.C. system.

In the form of the invention shown in FIG. 12 the reed is composed of a central portion 113 which is attached as aforesaid to the crest 104 and is silvered at 114 on its upper surface, the silver being attached by a lead 115 to some operative instrumentality. The wings of wafer 113 are attached by cementing or otherwise to glass reeds 107' to which the magnets 108 are aflixed as aforesaid. The magnets will, of course, be equally spaced from the crest and of equal weight, except in instances when it might be desirable to make the piezoelectric wafer responsive to two different signals, one transmitted by the right hand wing of the reed and the other, different, being transmitted by the left hand end of the reed.

By selecting and weighing the reeds there is formed a whole series of resonant structures on one core actuated by a single coil. This is a very versatile, multiplepreselected-circuit actuator. The signals from the reeds go to suitable switching circuits or actuating mechanisms.

In FIG. 13 is illustrated a sonic switch in which a transistor of npn type is used to generate the signal. A semi-conductor wafer 121, for instance germanium or silicon is mounted on a base and is united to a vibratory reed which is appropriately tuned. Three contacts 122, 123, 127 are made to the wafer, these transistor junctions being diffused into the semi-conductor or epitaxially grown on it by known processes. The contact 123 is the collector contact, 122 is the emitter contact, and 127 the base contact. A battery 126 is connected at one pole to 122, and at the other through a resistance R to the base contact, and through a matching impedance transformer 124 to the collector contact. The output is delivered through the terminals 128 of the transformer.

The transistor element may be protectively coated with a thin insulating film or lacquer without substantially affecting its function. In this circuit the resistance R and the DC. voltage E determine respectively the base current and the DC. load line of the transistor, thereby establishing that current-voltage combination which is suit ed to the purpose at hand. Different transistors will have different extreme values for the circuit constants. The primary impedance of the transformer 124 is selected to match the output impedance of the transistor in the desired range of the operation. The output impedance of the transformer is selected to match the load under which the reed switch will operate. The base current is a constant established by R and E. An alternating collector current is produced by the voltage induced by the AC. stress generated by the vibrations of the reed and wafer. An AC. voltage is induced by the alternating stresses in the semiconductor of the transistor and it is this which is delivered by the transformer.

In these devices the energizing is initially the operation of a transducer, the energy of the incoming vibration causing the device to vibrate mechanically in its own frequency only when activated by a corresponding frequency. The invention maximizes the peak vibratory strain which results from the mechanical vibration and utilizes the Villari effect by generating an alternating magnetic flux Whenever there is a mechanical alternating stress induced in the magnetostrictive strip. It is novel to employ the peak oscillatory strain of a vibrating reed as the chief inducing effect to operate desired circuits from a vibratory input source.

In these novel devices the transducer employed may be piezoelectric, magnetostrictive, piezo-resistive or transistor.

As many apparently Widely different embodiments of the present invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments.

What is claimed is:

1. A method of transforming sound energy into electrical energy for relay operation comprising, mounting a generator of the class of magnetostrictive, piezoelectric, and transistors at a point of major stress of a reed tuned to a selected sound frequency, subjecting the reed to a multiplicity of sound frequencies including said selected frequency, and utilizing the current gene-rated by vibration of the reed in response to said selected frequency, to energize a relay.

2. Apparatus for transforming sound energy into electrical energy for relay operation, comprising, a reed tuned to a selected sound frequency, means mounting said reed for vibration in response to sound including said selected frequency, a current generator of the class consisting of magnetostrictive, piezoelectric, and transistor connected with the reed contiguous to an area of high stress therein engendered by vibration of the reed in response to sound waves of said selected frequency, and relay means electrically connected with said generator and energized by the current generated by vibration of said reed.

3. A resonant switching apparatus comprising, an electric switch, a preamplifier electrically connected to said switch to open and close the same, a reed tuned to vibrate only in response to a limited band of sound frequencies incident thereon, and a magnetostrictive device mechanically connected to said reed at a high stress zone and electrically connected to said preamplifier whereby the response of the reed to sound frequencies in said limited band is electrically transformed to electrical energy to actuate said switch.

4. The switching apparatus of claim 3, said magnetostrictive device including fixed magnet means adjacent to the distal end of said reed, and AC. induction means of high permeability and loW retentivity, inductively associated with said reed and electrically connected with said preamplifier.

5. A resonant generator comprising a reed tuned to vibrate only in response to a selected narrow band of a multiplicity of sound frequencies incident thereon, a dielectric wafer connected with a high stress zone including one end of said reed and mounting the same for vibration, and stressed by and in response to vibration of said reed, magnet means associated with said wafer, induction coil means supported in inductive relation with said magnet means and wafer, and output signal connections leading from said induction coil means.

6. A resonant generator comprising a support, a resonant reed means carried by the support, a transistor electrically connected with a high stress zone of said reed means, and output signal means electrically connected to said transistor.

7. A resonant generator comprising a core including spaced upstanding elements and an upstanding support between said elements, a tuned reed mounted on said support and having its ends projecting over a respective one of said elements and spaced thereabove, first and second magnets each affixed to a respective end of said reed over a corresponding one of said elements, a coil inductively associated with said support, and piezoelectric means mounted upon said reed at a high stress zone thereof adjacent its place of mounting on said support.

8. The generator of claim 7, and a plurality of other reeds mounted on said support in side-by-side relation, each said reed being tuned to a frequency different from the others, and piezoelectric means mounted upon a high stress zone of each said reed, as aforesaid.

9. The generator of claim 7, said last named means comprising a piezoelectric wafer bonded to said reed between the ends thereof and responsive to essentially maximum stress engendered by vibration thereof.

10. Resonant switching apparatus comprising a base, there being a slot in and extending along said base, a comb of piezoelectric material afiixed in said slot, said comb being continuously metallized on one side and having each time thereof individually and separately metallized on the other side thereof, a plurality of reeds each tuned to a respective one of frequencies each different from the others, each said reed being attached to a respective one of the tines of said comb, a plurality of electrically operated relay means, and a circuit connection between each said relay means and a respective one of the individually metallized areas of said tines.

11. Apparatus for generating an electric current for relay operation in response to an alternating current of predetermined frequency comprising, a tuned reed vibrating in response to said frequency, a stress responsive element of the class consisting of magnetostrictive, and transistor means connected at a point of high stress to the reed, electric relay means, and circuit connections between said element and said relay means.

12. The method of generating an electric current comprising, employing the peak vibratory strain of a vibrating reed vibrating in response to harmonic induction, applying said vibratory strain to the sensitive element of a transducer, and utilizing the output signal of the transducer to energize a relay.

13. A sonic switch comprising, a semiconductor reed assembly vibrating in response to sound wave energy incident thereon, said assembly including collector, emitter, and plate contacts, a source of DC. voltage, a transformer, and connections electrically connecting said collector, emitter, plate, source, and the primary of said transformer.

14. In an apparatus for the conversion of sound wave energy into electrical energy for relay operation, a reed tuned to vibrate in response to sound wave energy of a pre-selected frequency incident thereon, first means mechanically connected with said reed at a high stress zone thereof generating an output voltage signal by and in response to stress induced in said reed by sound vibration of said frequency, a relay, and circuit connections be- 9 1O tween said first means and said relay, for energizing said 2,898,477 8/1959 Hoesterey 3108.3 X relay by and in response to an output signal from said 3,304,479 2/1967 Kleesatt et a1 310-26 X first means.

References Cited LEE T. HIX, Prlmary Exammer UNITED STATES PATENTS 5 US. Cl. X.R. 1,806,871 5/1931 Bower 3108.5 X 84464; 179-110; 307308; 317-143, 144, 147,

2,875,353 2/1959 Cavalieri et a1 3108.2 148.5; BIO-8.2, 8.3, 26

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Classifications
U.S. Classification361/184, 381/190, 310/323.1, 310/339, 310/26, 310/322, 310/330, 84/464.00R
International ClassificationH04R1/22, G01H3/08, H02N2/18, H04R23/00, G01H11/00, H01H51/32
Cooperative ClassificationH04R23/00, G01H11/00, G10G3/04, H04R1/22, G01H3/08
European ClassificationG10G3/04, H04R1/22, G01H11/00, G01H3/08, H04R23/00