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Judy E9 l46° J- Gf BIL-:ARD 'E1-AL 2,404,026 METHODOF AND SYSTEM FOR TRÀNSLATING SIGNALS Filed. March’ 29, 1944 >OZMD,NÉ @mi INVEN TORS. JOSEPH G~ BEARD. ROBERT W HARRALSON. ATTORNEY Patented July 16, 1946 2,404,025 UNITED STATES PATENT OFFICE 2,404,026 METHOD oF AND SYSTEM Foa TaANsLA'riNG SIGNALs Joseph G. Beard, Haddoniield, and Robert W. Harralson, Masonville, N. J., assignors to Radio Corporation of America, a corporation of Dela Application March 29, 1944, Serial No. 528,611 12 Claims. (C1. 179-1004) l 2 Our present invention relates to signal trans termined extent from the crystal-controlled fre lating methods and systems, and more particu quency of the oscillator. larly to a novel method of, and system for, trans Still' another object of our invention is to pro lating a physical displacement of a mobile ele vide, in a phonograph record reproduction sys ment into a corresponding voltage through the Ul tem, an oscillator which is crystal-controlled as agency of high frequency oscillatory energy. to frequency, the oscillator output being fed to Prior systems and methods have been proposed a pair of independent tuned circuits oli-resonance for translating a physical displacement of a mo bile element, such as that of a phonograph record to approximately the same frequency relative to the oscillator frequency, and the tuned circuits stylus, into a corresponding voltage by utilizing io having electrically associated with them respec high frequency oscillations. In such systems la tive rectiiiers provided with a common output characteristic of the oscillations, either ampli resistor adapted to provide a resultant diiferen tude or frequency, is varied in response to the tial voltage corresponding to physical displace aforesaid displacement, and a detector circuit , _ ments of a mobile electrode common »to both tuned is used to derive from the varied oscillations the desired corresponding voltage. One of the op l5" circuits. ' ' l " Y Still other objects of our invention are to im erating disadvantages of such prior systems> has been that the high frequency oscillations have' undergone amplitude and/or frequency varia-` tions at their source, or otherwise without refer ence to the displacement of the .mobile element, and such inadvertent and undesired variations prove generally the simplicity and eiiiciency of phonograph record reproduction systems, and more especially to provide a sound record repro " duction system which is not only reliable and efficient in‘operation, but is free of undesired high frequency componentsV in the detected output have been detected, thereby adversely affecting voltage. ` the resultant detected voltage. For example; mi Still other features will bestrbe understood by crophonics, or ballistics, in the oscillator` tube of §55@ reference to the following description, taken in such prior systems have tended to affect the `de connection with the drawing,` iniwhich we have tected resultant voltage. » » ‘ ‘ indicated diagrammatically a circuit organiza It is one of the main objects of our present in tion whereby our invention may be carried into vention to provide a method of, and system for, _effect - balancingr out amplitude and/or f-requency f changes the existence of which in the high fre quency oscillatory energy is independent of such displacement of a mobile element into a resultant iden-tical rectiñer circuits whereby undesired vari Y r Fig. 2 shows the ideal resonance curve of each rectifier input circuit, and a graphical analysis `Í~ of the operation of the system. Referring now to the system shown in Fig. l, the tube I is the oscillator tube and may be of » 'sof `oscillator tube. ations in the oscillations are balanced out in the , Another important object of oui1 invention is to provide a novel method of,” and system for,v ‘ any» well known type, as for example a triode. Our invention is not limited to any specific type and then applying the oscillations to substantially i derived from the rectiñer circuits as a resultan-t ' embodying the invention, voltage by producing high frequency oscillations, dilferential voltage. v In the drawing: Fig. 1 shows the circuit diagram of a syste energy being subjected to variation in response to a physical displacement of a mobile element.~ Another important object of our invention is to provide a method of translating the-physical common output of the rectifiers, while adesired variation produced by displacement of the mobile element in a characteristic of the oscillations is 5 The electron emitter or cath ode 2 is grounded, while> the plate or anode 4 is connected to the -l-B terminal of the direct cur rent energizing source (not shown) over a series path consisting >of coil 5, coupling link or coil s 4x5-’tand coupling link or coil 1. Coils 6 and 7 may each have a single turny but proper coupling to their respective secondaries (described below) is the prime consideration. Each of inductances or reproducing sound records, wherein vhigh 4fre coils- 5,_ 6` and 1. is preferably electrostatically. quency oscillations arexappliedrto substantially ¿g5-shielded _from the other to eliminate capacity cou similar rectifier circuits employed insound re pling therebetween. The dotted rectangles 5', 6' and 'l' represent shielding devices of any suit to provide output voltages lof opposite polarity- able form. The condenser 8 shunts the plate and having separate input circuits normally tuned 5 f _end ` of coil 5 to ground, Whereas condenser 9 by production, lthe rectifier circuits being connected to a common frequency which’diiïers to a prede 55" passes the lower end of inductance 1 to ground 2,404,026 3 for radio frequency currents. The condenser 8 is given a magnitude to tune the plate circuit of the oscillator tube to the normal or operating 4 ample, the push-pull condenser construction shown by A. Badmaieñ in his application Serial No. 490,614, filed June l2, 1943, granted March 13, 1945, as U. S. Patent No. 2,371,373, may be frequency of the oscillator. That is, condenser 8 tunes the series combination of coils 5, 6 and ‘I 5 utilized as our condensers 21-23 with a common mobile electrode. It is to?be clearly understood, to the frequency of piezo-electric crystal I I. The control grid 3 of oscillator tube I is con nected to the high potential electrode Iii of crystal II. The low potential electrode I3 is connected to ground. The grid resistor Iâ is connected in addition, that in place of using a record stylus . 30 to displace common electrode 29, there may be employed, as for example in a microphone, any other device which will respond to a force to be indicated by displacing the electrode 29. from grid 3 to ground, and provides a means for biasing the grid 3 negatively by virtue of grid In general, the mobile element 29 may be em bodied in any transducer. current flow through the resistor. As already The oscillatory energy introduced into tuned indicated, crystal II is tuned to the aforesaid operating frequency to which the plate circuit 15 rectiñer input circuits Il-E'I and 2-§~-2â by the separate coupling elements 6 and ‘i is varied in resonates. The crystal II may be provided with amplitude in response to the variations in ca separate metal electrodes or metallic »coatings pacity of condensers 2ï and 26. Normally the functioning as electrodes. This is a familiar and oscillator frequency is of such a value that it falls well known form of crystal oscillator circuit, and produces relatively constant amplitude waves of 20 at a point approximately 70% of the peak reso the fixed frequency of crystal II. By way of nant vo-ltage of tuned circuits ilk-21 and 22E-23. Hence, if the oscillator frequency is 18 mc., the example, it may be assumed that the constants normal resonant frequency of the rectifier input of the oscillator circuits are chosen to provide a circuits may readily be calculated from the rela frequency of 18 megacycles (rnc). Of course, the invention is in no way restricted to any particular 25 tion shown in Fig. 2. Here the solid line single peak resonance curve a'. is ideally assumed to be requency, nor to any particular type of oscillator that of each of input circuits i'i--Z‘I and 23-28. circuit. ' ~ The fixed-frequency oscillations are introduced It is obvious that if the mobile electrode 29 is instantaneously moved towards the stator of con into a pair of rectifier circuits. The rectiflers may be of any well known form and are shown, 80 denser 21 the capacity of the latter will increase, by way of specific example, as ofthe diode type. while the capacity of condenser 23 will concur rently decrease. This means that the frequency Diodes I5 and I6 are connected in the manner shown. Diode I 5 is provided with a resonant of circuits I'I--Z'I will. be decreased. while that input circuit including coil Il magnetically cou of circuit 23-28 will be correspondingly in pled to coupling link 6. The latter is included 85 creased. The opposing frequency shifts or devia with coil I'I within the shielding means 6’. The tions of the two input circuits will, of course. correspond to the stylus motion through the diode anode I 8 is connected to the high alternat ing potential end of coil ITI, while the opposite record groove. The sound record is not shown end of the latter is grounded. The cathode I9 since those skilled in the art of sound reproduc~ of diode I5 is connected back to ground through ing are well acquainted with the technique of reproducing sound from records. series-connected resistors 2i! and ZI. The cath Opposite detuning of the respective rectifier ode end of resistor 20 is bypassed to ground for radio frequency currents by condenser 22. input circuits relative to the normal or peak The diode I5 has its cathode 22’ connected to resonant frequency of curve o of Fig. 2 causes the the high alternating potential end of coil 23. The 45 oscillator voltage injected or induced in them to vary oppositely in amplitude andl consequently grounded end of coil 23 is connected in common to the grounded end of coil I 1. Coils 'I and 23 develops a variable voltage across the common are magnetically coupled, as in the case of coils load resistor 2I. The variable voltage is repre G and I7, and are housed Within the shielding 50 sentative of the original sounds which were trans means 'I'. The anode 24 of diode I6 is connected lated into groove variations on the record. to the junction of resistors 2G and 2l through a The functioning of the system will now be resistor 25. Condenser 2% bypasses the anode more fully explained, special reference being made end of resistor 25 to ground for radio frequency to the curves of Fig. 2. In the latter “frequency” currents. The coils I'I and 23 are each tuned to as the abscissa is plotted against “amplitude” es the same normal frequency by shunt condensers 55 the ordinate` The solid line curveV a is the nor 2l' and 28 respectively. The condensers 21 and mal resonance curve of each rectifier input cir 28 have a common electrode which is connected cuit, as explained previously. The point F0 on to the grounded junction of coils I'I and 23. The curve a shows the degree of initial mistuning or common electrode 29 is preferably a mobile arma off-resonance of the oscillator frequency relative ture located normally in spaced relation between 60 to the normal frequency of the rectifier input the respective stator electrodes of condensers 2'I circuits. The arrangementy including the degrees and 28. The pivoted end of the armature 29 is of coupling of coils 6 and 'I to their respective grounded, and the free end of the armature is, secondaries, is such that with armature 29 in its as shown, provided with a stylus or needle 30. 05 normal position the same amplitude of induced The stylus 30 is ofY any desired form, and is oscillatory voltage will be developed in the re adapted to ride along the grooves of` a record in spective rectifier input circuits. Under these con` known manner. In this way the mechanical ditions, the rectiñers will develop across resistor variations of the record are translated into cor 2I equal rectified voltages, the voltages developed responding physical displacements of the com mon electrode 29. The condensers 21 and 28 are 70 by each of the rectiñers across resistor 2| being proportional to the amplitude of the high fre accordingly varied in corresponding fashion, but in push-pull or opposing relation. Any desired to quency the fact oscillatory that resistor energy in2|itshas input its circuit. ungrounded ` or well known form of push-pull condenser may be employed for condensers 21 and 28. For ex end connected to unlike electrodes of said diodes, it follows that the ungrounded end of the resistor 2,404, 026 5 6 2I will Abe at zero potential due to cancellation provide a system of record reproduction wherein of the opposing rectiñed voltages. Hence, in the identical changes in oscillatory high frequency median or normal position of mo-bile electrode 29 energy are applied to identical rectifier circuits. and derive therefrom the rectiñcation products in opposition. Accordingly, such changes in oscil latory energy, whether of amplitude or of fre the succeeding audio frequency amplifier (not shown) derives no voltage from the ungrounded end of resistor 2l. Condenser 3| is an audio fre quency coupling condenser. Resistors 20 and 25 act as loading elements to determine the “Q” of the respective rectifier input circuits. quency, balance out. However, the pickup device. or more generally the common tum‘ng adjustment They device, causes opposite changes in the two identi cal rectifier circuits thereby providing a resultant further prevent a short circuit on each coil I1, 23 by the other and its respective diodes. Let it now be assumed that mobile electrode 29 is shifted towards the stator of `condenser 21. At that instant the frequency of circuit I1-21 is decreased since condenser 21 has its capacity in» creased, while the frequency of circuit '23»-28 is increased since condenser 28 has its capacity de creased. The dash line curve b in Fig. 2 repre sents the instantaneous shift in the resonance curve of circuit I1-21 due to the decrease in resonant frequency of circuit I1-21. The dot differential component of rectified voltage. From a generic viewpoint the input network of the rectifiers comprises a pair of reactances of like reactive sign (coils I 1 and 23 being of like reactive sign), and each ,of the .pair of reactances is tuned by a respective reactance of opposite reactive sign (condensers 21. 29 and 29, 28 are of opposite re active’sign relative to their respective coils I1 and 23). 20 Although our invention lends itself readily to use of a crystal-controlled oscillator, and we pre and dash line curve c represents the instantane ous shift in the resonance curve of circuit 23~---28 fer to employ such an oscillator, the crystal Il due to the increase in resonant frequency of the latter circuit. The oscillator frequency Fo (asN sumed to be 18 mc.) has not changed during the shift in the position of electrode 29. the aforesaid balancing action as to changes in oscillator frequency can be relied upon to alford satisfactory operation, even in the absence of Hence, points d andre Aindicate the respective adapted for use with laterally-cut records or “hill can, if desired, be dispensed with, inasmuch as crystal control. lFurther, the invention is readily locations on shifted curves b and c of the oscil and dale” records. i lator frequency Fo. VThere will now be induced a 30 While we have indicated and described a sys tem for carrying our invention into effect, it will be apparent to one skilled in the art thatour in vention is by n0 means limited to the particular organization shown and described, but that many greater amplitude of oscillatory voltage in circuit I1-21 than in circuit 2x3-28, as is readily >olo served from Fig. 2 because point d exceeds point e in amplitude. Hence, the ungrounded end of resistor 2l will be at a positive potential relative to ground, and the potential will be of a magni tude `depending upon the algebraic s_um of the rectified voltages. In ,other words, the rectified voltages are differentially combined to produce a modifications may be made without departing from the scope of our invention. What we claim is: l. A method which includes the steps of gen erating high frequency oscillations of a predeter resultant voltage proportional to the difference between the amplitudes of oscillatory voltages induced in the rectifier input circuits. By operat ing normally at the steepest point lon the slope tively small frequency value from said oscillation of the resonance curve frequency, separately rectifying voltages induced the resultant rectified mined frequency,> introducing said oscillations into a pair of resonant circuits tuned to a com mon frequency differing by a predetermined rela voltage will. be of maximum values for varying 45 in each of said tuned circuits, combining in po larity opposition the rectified voltage resulting in frequency deviations of the rectifier input circuits. The 70% olî-resonance point Fo is such a steep each of said rectification steps, and concurrently varying in opposite senses the frequency of each point, and is also a point of the curve where greatest linearity exists. of said tuned circuits in response to displacements , Where the displacement of mobile electrode 29 60 of a mobile element. is relatively slow. in response to miscellaneous 2. In combination, a pair of rectifiers having physical changes, the resultant rectified voltage a common output resistor, a separate tuned input across resisto-r 2| may be utilized in any desired circuit connected to each rectifier, means for tuning said separate input circuits to a common manner. For example, the ,voltage may be visually indicated in a measuring device, or it may 55 predetermined high frequency, said means in cluding a common mobile element whereby the be employed to operate a correction or work cir frequencies of said input circuits may be con cuit as in control circuits. , currently varied in opposite senses, and means Any undesired frequency modulation effects or for applying in substantially identical manner to amplitude modulation effects, arising otherwise said input circuits high frequency oscillations of than by movementv of armature 29, which may a frequency substantially different from the develop in the oscillatory energy induced in the common predetermined frequency of said input rectifier input circuits I1-21 and 23-28 will circuits. balance out across resistor 2 I. The balancing out 3. In combination, apair of rectiñers having of such undesired amplitude variations or fre quency variations takes place by virtue of the fact 65 a common output resistor, a separate tuned input circuit connected to each rectifier, means for tun that output resistor 2I is in push-pull relationtc ingsaid separate input circuits to a common pre rectiñers l5 and I6. It will Vbe obvious that any change in amplitude and/or frequency of the determined high frequency, said means including a common adjustable element whereby the fre oscillatory energy applied to coils I1 and 23, not due to movement of armature 29, will have the 70 quencies of said input circuits may be concur rently varied in opposite senses, means for apply same effect at the two rectiñers. Hence, the rectification products of these effects will cancel ing in substantially identical manner to said input out across resistor 2|. Our system is, therefore, circuits high frequency oscillations of a frequency non-sensitive to microphonics, or ballistics, in the substantially different from the common prede oscillator tube I. From a generic viewpoint we 75 termined frequency of said input circuits, and 2,404,026 7 means for accurately maintaining said high fre quency oscillations at said different frequency.y 4. In combination, a pair of rectifiers having a common output resistor, a separate tuned input circuit connected to ’each rectifier, means for tuning said separate input circuits to a common 9. In combinatioma pair of rectiñers having a common output resistor, a separate tunedinput circuit connected to each rectifier, a separate condenser for tuning each input circuit to a com mon predetermined high frequency, said con densers including a common mobile electrode whereby the frequencies of said input circuits predetermined high frequency, said means in may be concurrently varied in opposite senses, cluding' a common mobile element whereby the a crystal-controlled oscillator for applying in sub frequencies of said input circuits may be concur rently varied in opposite senses, means for apply ll) stantially identical manner to said input circuits high frequency oscillations of a frequency sub ing in substantially identical manner to said input stantially different from said commen frequency circuits high frequency oscillations of a frequency of said input circuits, and a record stylus opera substantially different from said common fre tively associated with the mobile electrode to quency of said input circuits, and said mobile produce physical displacements of the latter in element including a phonograph record stylus response to groove variations of a sound record. adapted to vary said mobile element in response 10„In combination with a crystal-controlled to groove modulations of a sound record. . high frequency oscillator including a pair of 5. In combination with a crystal-controlled series-arranged output elements, pair of recti high frequency oscillator including a pair of sepa rately shielded output elements, a Pair of recti 20 ñers each having its respective resonant input circuit, each of said input circuits being reactively fiers each having its respective resonant input circuit, each of said input circuits being reac tively coupled to a respective one of said output elements, said input circuits including a pair of resonating condensers of the type. provided with a common mobile electrode, and a common output resistor connected in the space current paths of said rectiiiers, said rectiñers being arranged in polarity opposition. 1 6. A method which includes the steps of gen erating high frequency oscillations of a predeter mined. frequency, inducing in response to said oscillations at least two resonant currents of a common frequency differing by a predetermined relatively small frequency value from said prede termined oscillation frequency, separately recti fying said induced currents, combining in polarity opposition the rectified voltage resulting in each of said separate rectification steps, and concur coupled to a respective one of said output elements, said input circuits including a pair of resonating condensers of the type provided with a common mobile electrode, a common output resistor con nected in the space current paths of said recti ñers. said rectiñers being arranged in polarity opposition, and sound-responsive means for actu ating said mobile electrode. 11. In a system for translating sound-repre sentative modulations into sound Wave currents, a source of high frequency oscillations, a pair of rectiiiers having separate input circuits, reactive means common to said input circuits for tuning the latter to a like predetermined frequency dif fering by a relatively small frequency value from the normal source frequency, means common to the rectiiiers for combining the rectified outputs thereof in polarity opposition thereby to provide rently varying in opposite senses the frequency 40 said sound currents, and said reactive means in cluding a transducer device for varying the fre of each cf the induced currents. o_uencies of said input circuits in opposite senses 7, In combination, a pair of diode rectifiers relative to said source frequency. having a common output resistor, a separate 12. In a system for indicating physical dis tuned input circuit connected to each rectifier, placements of a mobile element, a source of high means for tuningY said separate input circuits to frequency oscillations vof a predetermined fre a common predetermined high frequency, said quency, a rectifier system provided with an out means including a pair of condensers having a put resistor, a network for providing amplitude common adjustable element whereby the frequen modulation of said oscillations in accordance with cies of said input circuits maybe concurrently displacements of said mobile element, said last varied in opposite senses, and means for applying network comprising a pair of reactances of like in substantially identical manner to said input circuits high frequency oscillations of a frequency reactive sign, each of said reactancesbeing tuned by a respective reactance of opposite reactive sign substantially diñerent from said common prede to said predetermined frequency, said mobile ele termined frequency of said input circuits. ment being operatively associated with said last 8. In combination, a pair of rectiñers having respective reactances for concurrently varying in a common output resistor, a separate tuned input opposite senses the magnitudes thereof, means circuit connected to each rectifier, means for tun ing said separate input circuits to a common pre applying said oscillations to said network, said rectifier system comprising a pair of rectiñers determined high frequency, said means including connected in polarity opposition, each rectifier a pair of condensers having a common mobile electrode whereby the frequencies of said input circuits may be concurrently varied in opposite senses, means for applying in substantially iden tical manner to said input circuits high frequency oscillations of a frequency substantially different from said common predetermined frequency of said input circuits, and a piezo-electric crystal device for accuratelymaintaining said high fre quency oscillations at said differentfrequency. being connected in a closed circuit with a respec tive one of said like reactances and said output resistor, and means applying the modulated oscil lation output of said network to said rectifier sys . tem thereby to develop across said output resistor -‘a’ voltage representative of said physical dis placements. y JOSEPH G.y BEARD. ROBERT W. HARRALSON.