US2462435A - Apparatus for uninterrupted reproduction of disk phonographrecords - Google Patents

Description

Feb. 22, 1949. R. E. STANTON 2,462,435

' APPARATUS FOR UNINTERRUPTED REPRODUCTION 0F DISK PHONOGRAPH RECORDS Filed May 15, 1945 4 Sheets-Sheet 1 r INVENTOR. ROBERT E. STANTON ATTORNEY l I I I l l I, l l. J

Feb. 22, 1949. R. E. STANTON 2,462,435

APPARATUS FOR UNINTERRUPTED REPRODUCTION OF DISK PHONOGRAPH RECORDS Filed May 15, 1945 4 Sheets-Sheet 2 INVENTOR. ROBERT E. STANTON ATTORNEY Feb. 22 1949. R. E. STANTON APPARATUS FOR UNINTERRUPTED REPRODUCTION OF DISK PHONOGRAPH RECORDS 4 Sheets-Sheet 3 Filed May 15, 1945 R mm NT EN m 5 E T. R E B 0 R WWW ATTORNEY Feb. 22, 1949. R. E. STANTON 2,462,435

APPARATUS FOR UNINTERRUPTED REPRODUCTION OF DISK PHONOGRAPH RECORDS 1 Filed May 15, 1945 4 Sheets-Sheet 4 A SELECTIVE 2 SPEED DRIVE ELEMENT INVENTOR. ROBERTE. STANTON ATTORNEY.

atented Feb. 22, 194$ UNITED STATES 2,462,435

APPARATUS Fo'n UNI TERRUPTED RE; PRODUCTION OF DISK PHONOGR'APH RECORDS Robert E. Stanton, Denver, 0010.

Application May 15, 1945, Stimson-2,817

50mins- (c1. ire-100.4)

1 I'his invention relates to improvements in phonographs and has reference morepa'rticularly to an improvement by means of which an ordinaryautomatic phonograph can be made to play many standard size records (either or 12 inch) that are to be played in regular sequence. Such records usually have recordings on both sides. When an ordinary automatic phonograph 'is em- ;ployed, there is a break in the continuity while the record is turnedand also when another record f-is substituted.

.It has been. found that an ordinary automatic phonograph requires about fifteen seconds for the operation of turning, or, for the changing of a record. The auxiliary transcribing device which forms the subject of this invention will continue the music during this time interval, thereby providing an uninterrupted rendition.

My invention, briefly described, and in its broadest aspect, consists in interposihg in the circuit between the electric tone arm of the automatic phonograph and its loud speaker, a device which will record the sound waves, corresponding to the record being played, onto another're'c- 0rd and transmit them to the loud speaker at a sufficiently reduced tempo to lengthen the sound reproduction period sufficiently to cover the gap of fifteen seconds necessary for changing the records on the phonograph.

My attachment, in its present embodiment, comprises a sound recorder and transcriber of the type known as the Poul'sen telegraphone, which is connected with the electric pickup on the tone arm of the phonograph in such a way that a steel wire becomes magnetized in a manner corresponding to the sound waves. An electric pickup of a type that responds to variations of the magnetism of the wire, generates an electrio current which is then subjected to amplification and transmitted to the loud speaker. The attachment or auxiliary transcriber is so constructed that it will conti'nuethe operation of'the loud speaker 'ior about fifteen seconds aftrthe playingof-the original record has been completed. The auxiliary attachment for at least a periodbi the time, records and reproduces the music at a slower tempo'than the "original thus prolonging the'souhd some time after the original record has been played.

Although a transcriber of the telegi'aphonetype will be used for explaining the invention, it is evident that a transcriber employing a disk reco'rdcan be used. H

In order to describe the invention so that its construction, mode of operation, and its relation to the brigina'l phonograph can bereadiIyundeF stood, reference will be hadto the accompanying drawings in which the invention has been illustrated, and in which:

Figure 1 isa diagramshowingth'e generalar ran'geme'nt and relationship of the several ele-- merits; I

Figure 2 is a perspective view '01 'thetraris'cfib irig attachment, partsbeing broken away to better disclose the construction;

Figures 3 and 4 areuiagrams for use in 'de-' scribing and eaplainirigthe operation;

Figures 5 and'sa are ViWSiIl-iltffitirig' the 00hstruction of the magnet poies empm ed;

Figure 6 is a diagram mus-trance, means or preventing a new "record from being stfa'ite'd. the phonograph 'uiitil the record oh the tram scriber is finished; I

Figure 7"i11ustates 'a 'iheans for automatically changing the fndt'or speed; and

Figur'etis a diagram showing one means for retarding "the speed shifting mechanism to coinpe'nsate for the time e ement due'to the'relative movement ofiecord i2 and recording magnet. '9

Refeiehcewillnow be had to the drawings and to the sever-a1 figures 'thefeon whre the various elements havebeen'd'esignated, either by reference characters, or by numbers.

In Figure '1 the several elements of this machine have'beeh indica'ted in a general way. The automatic phonograph has been designatedby P; the series of records we; the tone ar'mbyT'rij the tone arm amplifier by TAA; the transcriber by T; the power ampl fier byPlajthe loud speaker by L; and the "monieritaryeohtact switch by sex. Since electronic amplifiers are old and well known, the specific arrangement and/or the circuits'h'ave n'dtbeen shown. The transcriber has been illustrated in Figure 2 to which reference will. now be had.

Reference numeral I designates a base on is supported a frame having at least two upright m'ei'nbers 2 and a transverse member 3. A shaft of tubular shaft 7.

4 is journalled in bearing 5 on the base and in bearing 6 in the transverse member. Surrounding this shaft is a tubular shaft "i that carries an arm {to the end of which is secured a recording mag net 9. A sound record it is carried by the upper end of shaft 4 and comprises a cylinder I I of nonmagnetic material such as aluminum or copper, or some suitable synthetic, preferably a nonconductor of electricity. Embedded in the cylinder tion indicated by A in Figures 3 and 4. When magnet 23 is energized, in a manner to be hereinafter explained, it moves the plunger and the inclined end portion 18 upwardly, thereby returning pinions 23 and 24 to the position shown in drawing and at the same time 46 moves the I6 is secured'to shaft l? and shaft 85 is slidable,

but nonrotatably connected therewith. Shafts "l5 and H are J'ournaled, respectively, in the upright frame members 18 and i9. Shaft 4 carries two gears 20 and 2 I, which are concentric and of different sizes,'as shown in the drawing. A gear 22 is nonrotatably connected with the lower end Shaft ll carries'pinions 223 and24. In theposition shown'in the drawing,

7 pinion 23 meshes with gear 22 and pinion 2d with gear 23. Shaft ll carries a spool-like member 25 between the flanges of which are positioned fingers 26, comprising the lower end of the downwardly projecting fingers' 2? of the bell crank lever. The bell crank lever is pivoted at 23 and a V has a horizontal arm 29 that extends to both sides of the pivot so as to form with arm 2? an unsymmetrical cross. When the bell cranklever is rotated in a counterclockwise direction, it moves pinion 24 into engagement with gear 2%, and disconnects pinion 23 from gear 22, whereupon tub'ular'shaft- 1 stops rotating. While pinions 23 i and 24 and gears 20, 2| and 22 have been shown as provided with teeth, a suitable friction gear may be substituted if found desirable. A worm .3Elis secured to the tubular shaft and engages a gear 31 on shaft 32. A disk 33 is carried by shaft 32 and has a notch 34 for the reception of arm 29. Whenever notch 32 gets into. position directly above this arm, the bell crank' arm 29 moves into the notch and shifts the gears as above explained. I

It will be observed that pinions 23 and gears 22 and 20 produce relative rotation of shafts 4 and 1 in opposite directions. For the purpose of this description the record Iii will rotate in a counterclockwise direction, as indicated -by the arrows, and recording magnet 9 will rotate in the opposite direction but at a much slower speed. Secured to one of the frame members 2 is a bracket 35 that carries a takeoff magnet 35 and an eraser magnet 37. Carried by the tubular shaft are two slip rings 38 to which the ends 39 of the soleprevent it, the music 7 different tempos.

noid winding on therecording magnet are 0011-" nected. Brushes 49 contact with the slip rings and these in turn are connected to terminals M by means of wires 42. A magnet 43 is supported on thetransverse frame member 44. A plunger armature s5 is associated with magnet 43 and has a slotted opening for the reception of'the short end of arm 29; When magnetl} isdeenergized, 'the weight of the armature rests on thearm 2e and urges the long end of this v arm' upwardly against disk 33;

lever will rotate in a counterclockwise direction and move pinions 23 and 24 out of engagement the'recording. magnet will cease to rotate and shaft 4 will rotate at 'a slower speed. This takes place when the recording magnet is above the inclined extension 46 of plunger 45 in the posiand therefore Whenever slot 34 gets into position above arm 29, the bell crank -of time that recording'magnet 9 rotates is dependent on the speed ratio of the worm gear (30, Si) and it may make several complete revolutions before notch 34 reaches a position above 29. The relative speeds at which 9 and i0 rotate and the number of revolutions made by the recorder magnet 9 determine the increased distance traveled by the record lilrelative to the recorder,

ll over what this distance would have been if recorder t had remained stationary and this in turn determines the time the transcriber will continue to play after recorder 9 becomes inactive. This time interval must be long enough to permit the automatic phonograph to change records which is about fifteen seconds.

In Figure 3 an attempt has been made to illustrate the several positions. A shows the stationary position of the recorder 9 after lever arm 29 has moved into notch 34 and until magnet 43 is energized causing cam 96 to move the recorder from position A to position B. The number of complete turns that therecorder 9 makes while disk 33 makes one complete revolution determines the extent to which the record has been lengthened and the time it will continue to play after recorder 9 becomes inactive.

It will be observed that record Ill will be lengthened, due to the movement of the recorder magnet 9, in the opposite direction from that of record'i 6, and therefore the music or other sound will have a slower tempo than that of the master record on the phonograph. This is necessary in order to gain the time necessary for changing the record on the phonograph. That part of record i0 that is recorded after the recorder 9 has stopped in position A will have the same tempo as that of the master record; It is now apparent that unless some means is provided to will be reproduced at two Practically'all makes and types of automatic phonographs operate at a turntablespeed of 80 R. P. M. which permits an ordinary 10-inch record to be played in from two and one-half to three minutes. The transcriber lengthens the time aboutfifteenseconds and in order to produce an audible rendition at the original tempo of that part recorded while the recorder 2 moves, the speed ofthe phonograph turntable must be increased during this period or else record I'll must be rotated at a slower speed until recorder 9 7 stops and then at a higher speed; in the example given, this construction has been shown.

Referring toFigure' 2, it will be observed that as long as shaft 1 turns, pinion 24 is in engagement with gear 20, but as soon as the pinions are shifted to disengage pinion 23 from gear 22, pinion 24 will move into engagement with the smaller gear 2i and increase the speed of shaft 4. In the drawing the gears have been shown more on 1658i diagrammatically-L but it is. to, be a under-- stood' that the gear ratiosmust; be: carefully calmnlace. of changing; the speed'of motor i3, it. possible; to run the motor of the automaticv phono raph: semcwhat; higher during. the time that recorder 9 rotates anditzo reduce this speed. toinormahwhen lever 29; moves intonotch 34.

It:w is; of. course, understood that both the:

recorder: magnet. and: the. takeoff magnet havelaminatedr comes so. as. to. reduce the hysteresis and: the resultant. magnetic 1 lag and heat to a minimum. Gmes. and; other parts. made from compressed; powdered: iron or any othersuitable material mayvbe used.

It is evident that theseveral magnets must be pnovid'ed i with specially; constructed pole pieces for thepurpose of following thespirals of the magnetizable wire record l2; the construction adopted for this purpose will nowbedescribed amt reference for this purpose will be had to Figuresfi and 5w.

Referring now-'to-Figure 5, which is partly in section; the-corehasbeen designated by 50' and this terminatesin a triangular end 5|. Three pulleys 52" have beenmounted" for rotation on pivots 5%: A chain 54" comprising a series of hingedly connected links, encircles the pulleys.-

Pole pieces 55 are attached to the chain and spaced equidistantlythereon; as shown more clearly in- Figure 511 from which-it will be seen tliat-theopposite interior'base angles are somewhatsmallerrthan those shown inFigure 5. The

cylindrical? wall of record Ill in which the wire theridgesv Bii andptherefore when-record l0 turns.

relative" to the pole pieces, the latter will move downwardly; The-parts, are so proportioned and arrangedjthatbefore the lower pole piece leaves the record: the upper one will be in position. The number of turns of wire I2 between the pole pieces'1 must be of "sufiicient length to record a lfi incl'r record. This'is, however; notan, essential requirement as will later appear. Pole pieces Won the pickup magnet 36 and the eraser magnet 31 engage the samespiral ridge a few inches apart whereas pole piece 55'on recorder magnet 9'*may engage a ridge'spaced several-turns away: Whenever recorder 9 is in positionv Bit mustbe on thesame helical coil'as 36'and3l.

In Figures 3 and 4 the pole pieces have been shown pointed in orderto simplify the drawing.

It is to be understood" that the poles must be of" such construction" thatthey will 'followthespiral ridges;

Alrrecords are not of the same length even when; of the same diameter. especially; ofa series, is likely to be shorter than the others;., any one or all of the records of a series'may be of*difier,ent,length. Unless means is provided" for" preventing such an occurrence,

The last record the automatic: phonograph; atterihaving: platt d? a record of average length followedsb record. would chan e 1' records; and; begins tor play another: before: the. transcriber; had: completed; 1 a.

i to be. engagechand'i closedrrw-hen; the toneamris:

moved: into; operative position. bythe automatim mechanism In. Figure 2. the sameswitch has: beenv shown: as controlling the: flow of current? from i a. source of electric current supply; suclraasf the batt'eryrBw, to the mag-net 43: Assoon there fore as the tonearm-TA is: moved 'intmoperative engagement with the record on the; turntables magnet 433' is energized and cam 46 moves the recorder magnet fl -fromposition A to position- B (Figs. 3 and 4) and: the-recorder begins at once to=magnetize wire l2 in-accordance wit-hthenew record. It is necessary tha-tno new recordingbemade' on wire I 2 until the-last1 notes have passed the pole of recorder magnet 9= whenirr position-B;

In order toprevent overlapping of magneticrecordings on wire l2; the following means havebeen provided.

Referringnow to' Figure'fi; it *wi11 be notedthat a magnet 58-: has been positionedadjacent the pickup" magnet 36' in'position tohave acurrent induced in its" windingwhen the magnetized record l 2-= passes its pole. The terminals of the winding of magnet 58 areconnectedby; wiires-59 and Gilto a'relay filthat is'heldin open-position as long-as acurrent is'fi owing through wir'es-59'*- and- 60: Such rela-ys are-availableand-the=con-- struct-ion has thereforenot been illustrated-z lever-62' is "pivoted to the-tonearmat== 63:; onc end is bent downwardly and provided with aroller 64 positioned toengagewtheupper surface of arecord: The-otherend or lever 62 extends upwardly as indicated at 55; magnet fih iscam ri'ed 'by the tone arm adii'acent'itspivoted end ancf this hasan armature 6*! pivoted-:at- 6i? and held" in such aposition by a spring 6=9 that the end of arm 65 will engage it and thereby hold-thetone arm in such position that the pickup needle-can not come into engagement with the record:- When the erased portion of wire I? reaches' a* point under thepole ot magnet-"5a, no current is induced inthe-winding and-relay B lclOses; there by-energizing magnet 66 which attracts armature 61' and-releases -lever-6'2; permitting? the tone-arm to dropandpla'ce' the pickupneedl'e into engagement-with the record. When electromagnet Bit-is energized 'and' the tone -arm drops into operative position, switch SjwX closes and energizes magnet" 43, moving recorder 9* from. position. A to position. B and shifting. pinions 23" and Z'4into the position shown in Figure 2; whereupon .a new record. wil1.be recorded on wire 12. andttranscribed into musicorsound;

It 1 is, of. course, understood. that. the. automatic shorten: I

. 7 r p'lifiedby the power amplifier 1 A transmitted to the loud speaker.

The operation of the device is as follows: A

number of records R which are to be played in succession are arranged in order in the automatic" phonograph; The several elements are connected as shown and described. The current generated by the electric pickup on the tone arm of the.phonograph energizes the coil on magnet S and the pole 55 of the lattermagnetizes wire I2.

When the magnetized portion of wire I 2 passes the pole 55 of pickup magnet 36, a current is in :duced in itswinding and this is amplified and transmitted to the loud speaker Magnet 37 WhiCh is energized by a constant direct current,

erases the magnetic record from wire l2 immedi creases the-length of wire between its pole and :ately after it has served its purpose in connection with magnet Recorder'magnet 9 moves in the :opposit-e direction to wire it and gradually inthat ofmagnet '35 until the distance will result 7 in a playing time of about fifteen seconds or sufii cient for the automatic phonograph to. change records, another record is to be recorded. a Means have been described for correcting for lhe recorder magnet then stops until the slower tempo that results fromthe movement,

of magnet 9 during a portion of the recording, and for correcting the speed of the phonograph turntable or of the'record iii to maintainthe original tempo, both during the time magnet 9 moves as well as when it stands still. Means comprising switch SwX and magnet 43' shifts the position of magnets at the beginning of each record and; means has also been provided for 'preventing overlapping of recordings on Wire l2 It is; evident that specifically different mechanisms may be usedand it is even possible to re-. place the telegraphone type of transcriber by one using ordinary records and a'pplicant therefore considers that his invention embraces the combination disclosed regardless of the form and/or construction of thevarious elements'so long as -,the elements perform the same function insube stantially the same way. r

Sincepractically all records manufactured are turntables rotate 80 R. P. M. the normal tempo of such records is attained only when they are rotated at, this speed. If the record is rotated at .;a=higher speed than this, the tempowill be above uiormal and vice versa.

It is evident that the music or sound emitted :from the loud speakermust have normal tempo.

'i-isturning, it follows that for the period that the recorders movesin a direction counter to that io'f1 record lit, the turntable of thephonograph must rotate sufii ciently above the normal speed to-producea normal tempo of the transcribed grriusic. 'Io; accomplishthis the phonograph motor must be speeded up during the time that the record ll-is rotating and reduced to normal speed when the record stops. Means for accomplishing this isshown in Figure '7 7 The iiivention has been illustrated and described in connection witha device for reproducin'gj sound. ,It is to be understood that protection 'is d'esired for any and all uses to which the invention can be put; .If it is found thatthe device can ,Vbeused for television ,or any other purpose requiring the reproduction of electric curintended to belused with phonographs whose" 8 rents having specialwave forms and frequencies, such use is contemplated.

The niagnetizable wire helix may be formed from any suitable material that can be magnetized and which will retain its'magnetism for a cient length of time to efiect the results desired. Certain kinds of steel are suitable and in addition such alloys as are now used for making permanent magnets.

It has been pointed out that the sound waves which are transcribedupon the electromagnetic record during the normal transcribing speed, which is an additive result of the drum speedplus the rate of the recorder magnet advance, will be delivered into the takeoff element at higher tempo during a brief interval immediately following the arresting of the recorder magnet and the shifting of the drum speed at the conclusion of a predetermined period.

At this time, the relationship of the various elements will be substantially as shown in Figure 4," when the'recorder 9-is shown in position A, and approximately one full turn of the record wire 52 separates the recorder 9 from the takeoff magnet 3. Assuming the normal rotating speed of the drum to be R. P. M., this increased tempo may result in distortion of the sound rendition for approximately /80 of a minute until the portion of the electromagnetic record, properly adjusted to the increased drum speed, reaches the takeoff magnet 3.

For the purpose of preventing a sudden changein tempo when the recorder magnet stops at point A the change in speed of the record l2 must remain the same until the point on record [2 reaches the pickup magnet 36, whichshould be 7 between pins 73 is greater than-the width of lever.

H to provide a lost motion connection. Shaft can move towards the right a sufficient distance to disengage pinion 23 from gear 22 before the dashpot becomes effective. Pinion 2d is quite wide as shown and the parts are adjusted so that it will take approximately fifteen seconds for' pinion '24 to disengage gear 2i! and engage gear The above is merely illustrative of means for this purpose and any mechanical equivalent can besubstituted. a

. Having described theinvention what is claimed as new is: V

1. A' mechanism for playing records in sequence, comprising; means for rotating a' record at a-predetermined constant speed, anelectric pickup operatively associated with a record adapted to be carried by the record rotating" means, a sound recording device operatively connected with the electric pickup, means translating the sound recordings into an electric current having amplitude and frequenc characteristics corresponding to therecorded sound, an electro dynamic loud speaker, means transmitting ourrent from the translating means to the loud speaker including. an electronic amplifier, said sound recording device including recording means,

an element upon which the recording. means records the sound, the recording means and translating means being relatively movable with respect to said element, the rate of relative movement of the recording means being greater than that of the translating means whereby a predetermined rate of decrease in the tempo of the sound emitted by the loud speaker relative to that of the record is effected, to obtain a time lag, and the loud speaker as a result of said decrease in tempo will continue functioning a sufficient time after the electric pickup and recording means become inoperative, to provide sumcient time to change to another record of the sequence.

2. In a continuously playing phonograph having a turntable adapted to carry records in sequence, a tone arm carrying an electric pickup device operatively associated with a record carried by the turntable, means for rotating the turntable at a predetermined constant speed, and means for lifting the electric pickup from the record and for replacing a played record with another; means translating electric current generated by the pickup into audible sound waves comprising a sound recording device including a movable magnetizable wire operatively associated with the electric pickup by means of a recorder magnet operatively associated with the movable magnetizable wire, means for translating the recordings on the wire into a variable electric current having the same wave form and amplitude characteristics as the current generated by the pickup, comprising a take-01f magnet operatively associated with the wire record, means for trans-- lating the current generated in the takeoff magnet into audible sound, comprising an amplifying device and a loud speaker operatively associated with the take-ofi magnet, and means for progressively increasing the distance between the recorder magnet and the take-off magnet along the wire to decrease the tempo of the current in the take-01f magnet relative to that in the recorder magnet.

3. A continuously playing phonograph comprising, a turntable, a sound record supported thereon, an electric pickup operatively associated with the record, means for rotating the turntable and record at a predetermined constant speed, a helical coil of magnetizable wire, a base on which the coil is supported, means rotating the coil about its axis, a recorder electromagnet carried by the base, said magnet having a pole positioned adjacent the wire whereby the latter will be magnetized in response to variations in the magnetic flux from the pole, means varying the magnetization of the pole in accordance with the variations in intensity, frequency and characteristics of the current generated by the electric pickup, comprising an electronic amplifier in a circuit interposed between and operatively connected with the recorder electromagnet and the electric pickup, a take-ofl electromagnet positioned with its pole in inductive relation to the wire, the last named electromagnet being stationary relative to the frame, means for moving the first named magnet in a path parallel to the wire in the direction opposite to that which the wire travels but at a slower speed whereby the space between the two magnets will gradually increase, an electromagnetic loud speaker, means comprising a circuit in series with the magnet windings of the 10 take-off magnet and of the loud speaker and an electronic amplifier in the circuit, for operating the loud speaker, whereby the variations in the magnetism of the wire will be translated into sound waves, and an eraser magnet operatively 7 associated with the take-off magnet and the wire, and spaced from the latter in the direction of wire travel.

4. A continuous phonograph comprising, a continuously rotating turntable, a sound record supported thereon for rotation therewith, an electric pick-up operatively associated with the record, a continuously moving magnetizable wire record, a recorder magnet of the telegraphone type positioned in operative relation to the wire, means including an amplifying device and circuit connections for energizing the recorder magnet by current from the pick-up, a take-off magnet positioned in operative relation to the wire record, a a

sound reproducing device, a circuit including a power amplifier connecting the take-off magnet with the sound reproducer, and means for progressively increasing the distance between the recorder magnet and the take-off magnet along the wire to progressively decrease the tempo of the sound emitted by the sound reproducing device relative to the tempo of the record, whereby the sound will continue to be reproduced after the recorder magnet has ceased to function.

5. A device for reproducing the recorded sound from a plurality of phonograph records played with short time intervals between them, so that the reproduced sound will be continuous, comprising in combination, an automatic phonograph having a turntable, a record mounted thereon, means for rotating the turntable, an electric pickup operatively associated with the record, and means for lifting the pick-up and substituting another record for the one just finished, means for reproducing the sounds in unbroken sequence and at a slower tempo consisting of a constantly moving magnetizable wire record, a recorder magnet mounted adjacent the wire for relative movement therealong, means for energizing the recorder magnet by current from the electric pickup, comprising a circuit containing an amplifying device, a take-oil" magnet positioned adjacent the wire record and spaced from the recorder magnet in the direction of movement of the wire, means for increasing the distance between the recorder magnet and the take-oil magnet along the wire to decrease the tempo of the electric current induced in the take-off magnet relative to that of the electric pick-up, a loud speaker, and means for energizing the loud speaker from the take-off magnet comprising a circuit containing a power amplifier.

ROBERT E. STANTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,780,414 Andres Nov. 4, 1930 2,038,647 Clausen Apr. 28, 1936 2,170,751 Gabrilovitch Aug. 22, 1939 2,362,803 Clausen Nov. 14, 1944 2,380,392 Begun July 31, 1945

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