US1931035A - Switching apparatus for sound reproducing systems - Google Patents

Description

Oct. 17, 1933. J. L. REYNOLDS SWITCHING APPARATUS FOR SOUND REPRODUCING SYSTEMS Filed April 1; 1927 3 Sheets-Sheet 1 Attornev Oct. 17, 1933. J. L. REYNOLDS SWITCHING APPARATUS FOR SOUND REPRODUCING SYSTEMS Filed April 1, 1927 5 Sheets-Sheet 2 ALJ A [tor/76y Oct. 17, 1933.

J. L. REYNOLDS 1,931,035

SWITCHING APPARATUS FOR SOUND REPRODUCING SYSTEMS Filed April 1, 1927 3 Sheets-Sheet 3 w K86 v'v v'vi'fivv'v H IIIVV MJ z; I \I] 4r AL I x" l 4 9 14 ttor ney Patented Oct. 17, 1933 UNITED STATES SWITCHING APPARATUS For: SOUND arrnonuomo sYs'rEMs John Louis Reynolds, Long Island'City, N. Y., assignor, by mesne assignments, to Electrical Research Products Inc., a corporation of. Delaware Application'April 1, 1927. Serial No. 180,323 15 Claims. (01. 179-10o.4)

This invention relates to transmitting and reproducing systems, and in particular to those systems wherein vibrations, such as sound or mechanical vibrations, are to be transmitted and reproduced.

In certain types of reproducing systems, for

example, those involving the use of an electromagnetically operated sound reproducer, it is highly desirable to be able to rapidly associate said reproducer in succession with a plurality of transmitters without causing any perceptible or disagreeable effects on the ears of an audience because of transition from one transmitter to another;

An object of the invention, therefore, is con cerned with methods and apparatus for control-. ling the effective connection 'of separate trans-j mitters, each of which may have different characteristics, with a common reproducer without the causing of any deleterious effects on the reproduction, and without renderingthe transfer of connections noticeable to an auditor.

For the purpose of illustrating one manner of attaining the above object as wellas other objects pointed out herein below, the invention is shown and described in connection with sound recording and reproducing apparatus suitable for use with picture projecting apparatus for the purpose of synchronizing the sound reproduction with the pictures being projected. In synchronized sound and picture systems of this character, the sound and picture records may be operated independently of each: other, At certain times it may be necessary to replace'one sound record by anothersoundrecord without interrupting the continuity of the picture projec tio'n or without rendering the change noticeable to an audience.

Accordingly, another object of the invention is to provide a synchronized sound and moving picture system wherein the sound vibrations may be recorded. in separate mechanical media and each of said media may be' effectively associated with the projected, picture without disturbing the continuity and pleasing quality of the sound reproduction.

Another object of the invention relates to the method of combining the effects produced by discrete sound records, so that the, effect on the ear of an auditor is the same as if but one continuous record were employed.

A feature of the invention resides in an adjustable electric network or artificial line connected between a plurality oftransmitters and a sound reproducer, for causing the effective more fully pointed'out herein below.

association of one transmitter with said reproducer and rendering ineffective the association of the other transmitter with the reproducer without disconnecting either of said transmitters from said reproducer during the associating process. n

Another feature of the invention pertainsto an electrical network and switch means associated with a plurality of transmitters and reproducer, said switch being capable by its operation, of concurrently rendering the effects of one transmitterupon said reproducer-inversely as regards the effects of the other-transmitter onsaid reproducer.

. Another feature of the invention is character.- 70,

ized by means for fading one series of sound modulated electrical impulses into another series of sound modulated electrical impulses.

An additional feature of the invention resides in the combination of means for 'rapidly associating in succession a number of mechanical sound records with a current amplifier, so that the output of said amplifier may be rapidly brought to the'same energy level for successively associated records. v

. The invention further comprises the various combinations of elements and structural details which go to make up an effective synchronized sound and moving picture system, as will be 8 In order that a clear understanding of the invention may be readily attained, attention is hereby'directed to' the accompanying drawings which illustrates certain modes of 'using the invention, but it is to be understood that the in ventive idea-is susceptible of many other uses, as will be apparentto those familiar with the practice of the art to which the invention relates.

Another feature of the invention pertains to a combined picture and sound reproducing 'sys-' tem wherein the sound current amplifier may be operated at a substantially fixed gain, and may be located at any desired distance from the picture projector. The output level of the sound from the soundprojector may be controlled by an electrical network which may be adjusted from anyone of a number of convenient points. n Fig. 1 of the drawings show the invention incorporated in a synchronized sound and moving picture system employing, mechanical media sound records, mechanical electric translators, vacuum *tube amplifiers, and electromagnetic sound reproducers. j v

Fig. 2 of the drawings show the invention applied to a system similar to that disclosed in Fig. 1, and by means of which the fader network may be rapidly and efiectively interconnected with any two of a number of electromechanical sound translators.

Fig. 3 shows an alternative form of the fader using a slide wire resistance in place of an artificial line.

Fig. 4 shows schematically a sound reproducing switching system according to the prior art.

Fig. 5 shows a modified form of switching arrangement by which the number of sections in the artificial line may be reduced one-half.

Fig. 6 illustrates a fader network modified so that the transition from one record to another may be accomplished without reducing the energy level of the currents to zero.

Fig. 7 shows characteristic curves of the ffader networks shown in Figs. 1, 2, 3, 5 and6.

Referring to Fig. '1 of the drawings, which illustrates a' preferred embodiment'of, the invention, there are shown moving picture projecting'machine's, P and P and a plurality of transmitting phonographs schematically represented by the turntables 2 and 3, respectively. These turntables may be mounted on respective spindles 4 and,5 which may be operatively associated with their respective driving motors M and M by means of the diagrammatically represented clutchesG and 7. Each drawing motor should be sufiiciently powerful to simultaneously operate a turntable and its associated projecting machine; Devices 8 and 9, if desired, may be provided between theclutches and the turntables to' permit of relative adjustment between the moving picturefilm and the sound records while the sameare in motion. The mechanical records 10 and 11 may be of the well known disc type with the sound cuttings in the form of a continuous spiral of varying depth or of varying width, as may be desired. The discs may be of waxor other suitable material. The discs in the recording process may, if desired, be prepared so that there is an overlapping of' the records on each disc ;.that-is to say, a portion near the end of the recordin disc 10 may be duplicated in disc llfor purposes hereinbelow pointed out.

For the purpose of translating the disc cut-' tings into current impulses there are provided respective pick-up devices, 12 and 13, with each of which is associated its respective stylus 14, 15. The styli 14, 15 .trackv the cuttings in their respective discs. The varying amplitudes of the disc cuttings cause the stylus to be moved accordingly and this movement in turn serves to cause the pick-up? device to generate voltages whose amplitudes correspond to' the extent of movement of the stylus.

- H. type networks.

Assuming for the present that'turntable 2, and projector P are in operation, then the varying sound modulated currents from the device 12 are led by means of conductors 16 and 18 to the terminals 20 and 22 of the network or artificial line, AL. This artificialline is made up, as shown of a number of serially and bridge-com.

nected resistances or their electrical equivalents, and constitutes a series of so-called ladder or Connections are made from various points of this network by means of conductors 24,26, 27, etc., to corresponding contact points in the switch S,tl1ese contact points being arranged preferably, for rapid connection, in the form' of a circle as shown. For the purpose of connecting the primary winding of trans- ,high impedance.

'may be such, with regard to the width of the brushes 37 and 38, that each brush in moving makes contact with the one segment before breaking contact with the preceding segment. It is obvious then that when the arm 34 is rotated the primary winding 40 of transformer T1 is at all times in circuit with the artificial line AL. Various other well known arrangements 'might be used for insuring the continuity of this circuit while the switch S is being moved. In addition, the degree of fineness of adjustment attainable by switch S may be increased by using a greater number of contact points and a correspondingly greater number of H sections in line AL. It is desirable that the impedances of the end sections S and S be designed so as to match the impedances or" thecircuits looking toward the respective reproducers l2 and 13, and the other sections of the artificial line may be designed so' that the mid-series value of impedance will bear the correct relation to the input of the amplifier,' thus providing optimum impedance matching relations.

Heretofore, in controlling the volume of sound from the reproducer, it has been customary to use an amplifier whose gain was controlled by apotentiometer which, in most cases is of very In as much as such a potentiometer and the intimately associated connecting circuits are very susceptible to electromagnetic pickup it was necessary to locate them very close'to the amplifier proper. In certain cases it is not practical to have the'amplifierand control potentiometer in the same room as the picture'projecting apparatus, which fact would necessitate the operators leaving his machine whenever the volume required changing. In accordance with the present invention the line AL may be a relatively low impedance device which renders it capable. of being located at a considerable distance from the amplifier without its being affected appreciably by the electrostatic capacityv of the'connecting wires, and also is less susceptible to any other form; of parasitic'interference. As a result the line AL may be placed at the location which is most convenient for the picture operator. For this purpose thesspindle 36 of switch S has rigidly mounted thereon the gear 43 which cooperates with gear 44. This latter gear is fixed in any suitable manner to the shaft 45, at the end of which is fixed theadjusting hand wheel 46. .Shaft 4-5 may also be mechanically connected by a suitable pinion 'tothe rack 91 which in turnfi's adapted to be moved by the handwheels 9 2, 93 located at other convenient points in the operating room. 1 V 7 From the foregoing description, it is seen that the function of switch S is to cut-in a greater or less number of sections of the line AL in en'- cuit with theamplifier 41 and a given onset the devices l2, l3. Amplifier 41 is preferably of the three-electrode space discharge type, which is preferably designed that during reproduction it has a fixed gain relation between the input and output voltages.

Referring to Fig. 7, there are shown character the power device 13 is simultaneously varied.

The point P at which curves T and T1 cross each other corresponds to the electrical midpoint of the line AL, the energy level of the point P is dependent upon the characteristics of each half section of the artificial line AL. For example'as shown in Fig. '7 the energy level of the :point P is substantially zero. If desired the. artificial line may be so proportioned thatwhen the brushes 37 and 38 are on'the middle set of .con-

tacts 4'7, 48, the energy level may have any other minimum value, for example, that indicated by the'point P in Fig. 7, in which case the rest of the system including the amplifier 41 may be adjusted so that these currents have no appreciable effect on the reproducer 60. in other words, the artificial line may be so proportioned that the energy level of'the currents applied to theamplifier 41 may have any desired minimum value. Anotherarrangementfor controlling the minimum energy level is shown in Fig. fi'wherein the rectangles T3 and T4 represent schematically transmitting devices which may be similar to the devices '12, 13 and the associated apparatus '(Fig. 1); The artificial line AL may be similar to the line AL of Fig; l and maybe so proportioned thatwith brushes 3'7 and 38making contact with the midsection of the line, the energy level of the currents reaching the amplifier 41 from the devices 12, 13 is substantially zero in which case the attenuation characteristics .of .the' currents from the respectivetransmitters can be represented by curves si'rnilarto curves T and T1" of Fig. 7. Should it be desired to raise the minimum energy level to any other point above zero, for example tothe point P of Fig. 7, switches 95 and 96 may be operated toconnect the'sections 97 and 98 directly from the respective transmitters 12, 13 to the input circuit of the amplifier, 41 thus providingfla by-path for the sound modulated currents which is independent of the position of rents after being led to the terminals 20 and 22 of the artificial line AL thence passing thru contacts of switch S to transformer T1 are attenuated to a greater or less degree in'acc'ordance with the position of the brushes of switch S. In the particular position shown in the drawings only the end section S1 of the line AL is connected in circuit with the device 12 and the transformer T1, accordingly these cur v rents will undergo minimumattenuation when they reach the transformer T1., On the other hand, should the device 13 be'also operating at this time,'the currents generated thereby and reaching transformer T1 undergo maximum attenuation. Under this condition, with both devices 12 and 13 operating simultaneously, the

currents in the transformer Ti will be sub- 3 stantially those generated bydevice 12. By moving the brushes 37 and 38 in a "counterclockwise direction the currents from device 12 are gradually attenuatedand, in the inverse sense, the currents from device 13 undergo decreasing attenuations. When. brushes 3'77 and 33 passbeyond the middle points 47 and 48, the device 12 begins totake control. Thus by means of the switch S the "energy level of'the currents reaching transformer T1 from device 13 are gradually increased and the energy level of the currents reaching this transformer from device 12 are gradually" decreased, these two currents gradually and imperceptibly blending with each other'in the primary winding of transformer T1' and transition between the records 10 and 11 is smoothly, gradually'and continuously effected.

Under certain circumstances it may be des'irable not to have the currents from the devices 12 and 13 blend or fade into each other as abovefdescribedin which case the switch'49 is closed and-places a short circuit across the electrical center of the artificial line AL. Hence;

with the switch S in the position shown'in the drawings, the currents from device 13 are entirely' shunted from the transformer 'T1 which is energized solely under control of the device 12. Theconverse is true when switchSis rotated past the middle points 4'? and 48.

For various reasons the records 10 and 11 may not be always-cut to the same average amplitude, which, if certain precautions are not taken may result in a different energy level of the currents reaching transformer T1, when switching i" effected between one record and the next. For this purpose, according to the 'prior art. amplifiers with variable gain werejrequired. A. system of this type is shown schematically in .Fig. 4 of the drawings. .In such a system, should it be desired to switch'from the upper record 55 to the lower record 54, it would be necessary inorder not to produce any objectionable sounds clenly take off the load "from theamplifier, to move the contact 50 relatively slowly tothe point 51, at which time theswitch 53 may be manipulated to cut-in thelower, reproducer, after which the contact 50 must be movedback to the desired point. If the record 54 happened to be cut to the same average degree of amplitude as record 55, the; contact 50 might be moved to its original position. Should these two records, however, differ in the degree of cutting, it would be necessaryto further adjust contact 50 in order to produce the same volume in-the loud speaker 52 as was produced when record 55 was functioning. Thus with records of different degrees of cutting, in order to maintain the same volume of sound from the device 52, three distinct operations were necessary in order to switch from one. record to. another.

With a fading device such as hereinabove When it is desired to produce synchronized sound and moving pictures, the positive film to be projected is-inserted: in the projecting mawith the projecting -machine are started: Switchfi'l, may then be operated and switch 8 chine .(Fig. 1), and the turntable 2, together c v adjusted until the desired outputxis obtained from amplifier 41, as indicated 'by a device 58 which may take the form of a monitoring loud speaker. Switch 56 may then be operated to'connect the loud speaker 60. in circuit.- .For the purpose of description, it will be assumed that the switch S has thus been adjusted to close the circuit through contacts 61 and. 62.

Assuming it is desired to blend the effects of record 10 into those of record 11 when the end of the cuttings on disc 10 is nearly reached, the turntable 3 and projector P are started in operation, the switch 49 being open as hereinabove described. Switch S is now rotated to increase the number of sections of line AL in circuit with device 12 and amplifier 41, at

V the same time decreasing the attenuation of the currents from device 13. Switch S is rotated in this manner until device 58 indicates the same output from amplifier 41 as was obtained when record 10 was functioning.

Should the records 10 and 11 be such that it is not desirable to blend the effects of one into those of the other the switch 49 is closed prior to the beginning of the operations. Accordingly, when it is desired to switch from record 10 to record 11, the procedure is similar to that already described. In this case, however, movement of brushes 3'7 and 38 from contacts 61 and 62 in a counter clockwise direction, reduces the current from device 12 gradually until contacts 47 and 48 are reached when this current is zero. Further movement of switch S increases thecurrent from device 13, which thereupon takes control of the loud speaker 60, thus at no time is there a feeding of current from device 12 to device 13 or vice versa.

- When the discs are so prepared that the'end portion of the cutting in'disc 10 is repeated at the beginning of the cutting in disc 11, the element of the artificial line AL are soproportioned 'that the movement of switch S has no effect 7 upon the volume of sound produced in the loud speaker 60, but simply transfers thecontrol of said speaker to one or the other of the records. Consequently, advantage may be taken of the overlapping of the records to perform the switching over process.

' Referring to Fig. 2 of the drawings, there is disclosed a system of the general type disclosed in Fig. 1," but with more than two pick-up devices. numerals 63, 64, 65,'etc., may be similar to cor-. responding devices in Fig. 1, comprising a turntable and an associated electromechanical pickup translator. Each of the spindles on which the turntables are mounted may be mechanically connected through suitable gearing to the same motor that drives the'associated picture projec- 1 tor, or they may be driven by separate motors which are. synchronized by any well-known means. Each'of the sets of conductors 69 and 70 leading from the respective devices 67, 68, etc., terminatesin corresponding plugs '71, 72, etc. The apparatus shown within the dotted rectangle is .a fader similar to that described in connection with Fig. 1 and comprises an artifi-' cial line AL and a progressively movable switch represented schematically by the contacts 73 and '74. The end'sections 'of this artificial line are'connected to respective jacks 75 and '76 by.

means of which any two of the pick-up translator devices 63, 64, etc., maybe associated with the fader. Thus the fader may be connected to any one or more of the pick-up devices as The devices indicated generally by the conditions demand, thus forming a very flexible system of interconnection and transfer. The rest of the apparatus disclosed in this figure, namely, the coupling transformers, vacuum tube amplifier and loud speaker, may be similar to those described in connection with Fig. 1. The switch contacts 73 and 74 may be moved in an equivalent manner to that disclosed in Fig. 1 and the procedure, in changing from record to record, is the same as already described. It is believed, therefore, that further description of this figure is unnecessary.

Fig. 3 shows an alternative form of fader in which slide-wire resistances are employed to vary the input to the amplifier. In this modification the conductors 16, 18 and 17, 19 leading from the transmitting devices T3 and T4, re-

spectively, terminate in corresponding artificial line sections AL1 and ALz. Line sections ALi and ALz are connected by the high-resistance slide-wires '77 and 78. In addition, an artificial line section .ALs is inserted in the conductors 33 and 35 leading to an input transformer, such as T1 (Fig. 1). These artificial line sections are so designed that for varying positions'of the sliding contacts 79 and 80, the impedances of the circuits looking from the respective devices T3 and T4 are substantially constant. In a similar manner, the artificial line sections AL:

The operation of this form of fader is with device T4 decreases, causing" the currents from these devices to blend into each other in a similar manner to that described in connection with Fig. 1. If this blending is not required, a short circuit maybe placed'across the electrical midpoints of the slide-wires 7'7 and 78; as described hereinabove in connection with switch 49.

Figure 5 whereby the artificial line may be reducedto shows a switching arrangement one half of the length of the lineshown in either Figs. 1, 2 or 3. Inthis figure, T3 and T schematically represent transmitting devices similar to those shown in the lefthand portion of Fig. 1; The artificial line AL may consist of electrical impedance elements similar to the sections of line AL ofFig. 1. It will be noted however that each of the devices T3, T4 feeds into the same end of line AL, the number of effectivesections of'line AL in series with each device being de-' pendent upon the position of the brushes of switch S. Switch S in'the construction shown.

in Fig. 5 has series of separated contact points C, C similar to contact points 47, 48, etc. of Fig.1, and two long segments 39, 50, in addition a continuous segment 94. Conductors 33, 35 leading from the amplifier 41 are connected respectively to the brushes 95, 96 which are insulated from each other and are adapted to contact with the associated segments C, C Also mounted on the shaft carrying brushes, 95, 9,6 is a brush 97 which bridges the segmentsBQ, 40, with the continuous segment 94. Assuming that brushes 95, 96, 97am moved to contact with contacts 98, 83, 94, 40,'the loud speaker 60'is connected in circuit with only the first section of the artificial line AL. This circuit may be traced from the conductor 33, brush 95, segment 98, conductor 81, first sectionof the line AL, conductor 84, brush 97, through device vTa, conductor 86, conductor 82, brush 96, to conductor 35. As brushes 95, 96, 97 are moved downward a corresponding greater number of sections of line AL are included in circuit with device Ta and loudspeaker 60. When it is desired to switch to the transmitter T4, brushes 95,96 and 9'7 are moved to engage segments 8'7, 88 and 39 in which position the transmitter Ta is out of the circuit, and transmitter T4, is in circuit with all the sections of line AL. As brushes 95, 96, 97 are moved further downward the number of sections of line AL in circuit with the transmitter T4 is reduced causing a gradual increase in the volume of sound from the loudspeaker 60. As hereinbefore described in connection with Figs. 1 and 6, the line AL may. be proportioned so that when all the sections. are

in circuit with a transmitter the energy level of the currents applied to the amplifier 41 may be substantially zero, or the line may be such that this minimum energy level has any other desired value. Similarly a direct by-path represented by the dotted lines of Fig. 5 may be provided by which the minimum energy level may be varied from zero to any value required.

From a consideration of the foregoing ,description it is clear that many modifications may be made 'in the apparatus disclosed withtransmitters or the like. 40'

. in this respect. 60"

out departing materially from the spirit and scope of the invention. For example, thepickup device T3 and T4 may take any of the wellknown forms such, for example, as telephone Similarly, switch S may be replaced by any other well-known form of switch for progressively varying the connections between the input transformer T1 and the pickup devices. While the artificial lines are shown as comprised of resistances it is clearthat any form of impedance device whether inductive, condensive, or a combination of. both, may be employed, it being understood that the showing of Fig. l is meant to be essentially schematic In addition, while a separate picture projector has been shown associated with each turntable, the invention includes within its compass the use of a single projector which may be used in common with a number of turntables. For

example, the motor for driving the projector P- may also serve to drive both the turntables 2 and 3 which may be associated in succession with the projector in the manner hereinbefore described.

Finally, while the invention-for the purposes of illustration merely, has been shown-in connection with a sound reproducing system, it is understood that the compass of the invention sections of said network, wipers for said-contact sets, means for moving said wipers progressively overone of said groups of contacts sets to gradually increase the number of sections of said network in circuit with one of said transmitters,

and for moving said wipers over the other group each group being electrically multipled, wipers for said sets, and means for moving said Wipers over said sets so that during one half of their movement the number of sections of said line in circuit with one of said transmitters is gradually increased and during the other half of their movement the number of sections in circuit with the other transmitter is gradually decreased.

3. In a sound reproducing system, a plurality of sound transmitters each connected toan incoming circuit, a sound reproducing device connected to an outgoing circuit common to said incoming circuits, a progressively operable imped ance adjusting device interconnecting said circuits, and means to variably operate said impedance adjusting device to successively and at will effectively associate said transmitters with said sound reproducing device, said impedance-adjusting 'device being designed to substantially maintain the impedance matching of said apparatus at all times.

4. In a sound reproducing system, a plurality of sound transmitters each connected to an in coming circuit, a sound reproducing device connected to an outgoing circuit common to said incoming circuits, a'progressively operable impedance adjusting device interconnecting said circuits, and means to variably'operate said adjusting device to effectively associate either one or both of said transmitters with said sound reproducing device, said impedance adjusting device 'beingdesigned to substantially maintainthe impedance matching of said apparatus at all times. 5. In a sound reproducing'system, a pluralityof sound transmitters each connected to an incoming circuit, a sound reproducing device con-- nected toan outgoing circuit common toflsaid incoming circuits, a progressively operable impedance adjusting device interconnecting said circuits, and means to change said sound reproducer fromeffective association with one train mitter to effective associationwith theother and "at the same time control the energy. level of the incoming circuit, a progressively operable impedance adjusting device interconnecting said circuits, and means to variably operate said impedance adjusting device tochange said sound reproducer from effective association with one transmitter to effective association with the other by progressivelyattenuating the currents from one transmitter and at the same time progressively increasing the energy level of the currents from the other transmitter, said impedance adjusting device being designed to substantially maintain the impedance matching of said ap-- paratus at all times;

' 7. In a sound reproducing system, a progressively operable switching device, fixed and movable contacts for said switch, a sound reproducing device connected to the movable contacts of 7 so designed that impedance matching for said sound reproducing .device and said transmitters is substantially maintained in all positions of said switching device.

8. In a sound reproducing system, two transmitters, a sound reproducer, a switching and controlling device acting on the potentiometer principle, said device consisting of a series of electrical network pads and means including suitable electrical connections between said transmitters, sound reproducer and switching device to operate saiddevice to effectually associate said sound reproducer with a desired one of said transmitters, the design'of said net work being such that mid-series impedance matching is substantially maintained with respect'to said'transmitters and reproducer.

9. A music synchronizing attachment for phonographs with two record tables, corresponding tone arms, electric pick-ups, and electric motors rotating said tables; said attachment comprising a manually operated synchronizing control embodying a resistance coil in circuit with both pick-ups and a control lever arranged in circuit with said resistance coil to gradually increase current to one of said pick-ups and simultaneously decrease current to the other pick-up to respectively increase the volume of sound produced by'the first pick-up from the record it isin contact with, and to decrease the volume of sound produced by the other pick-up from its record, and a control for volume of sound arranged in circuit between said synchro-' nizing control means and the tone chamber of the phonograph.

10. An electric reproducer for sound accompaniment to motion picture films including, a plurality of records of sounds, a plurality of electric current pick-up means, a loud speaker means, and a, single fader means associated with said pick -up means adapted to selectively switch overfrom one of said pick-up means to another of said pick-up means to translate sound selectively from any of said records to'the other without audible break between the selections.

11: In an electric reproducer for sound accompaniment to theatrical productions, ,includ-- i g, aplurality of record means, a plurality of electric current modulating devices for translating the recorded sound variations from said record means into corresponding electric current.

variations, amplifier means, reproducer means, and a single fader means associated with said electric current modulating devices and said re.-

producer means to switch over and blend selec-.

tively from said record means.

12. In an electric reproducer for sound accompaniment .to motion picture films including,

recorded sound variations without audible break between sections of said recordings.

1 3. The combination with apair of pick-updevices for translating records of sound varia-:

tions into-corresponding electrical variations, a

sound radiating device responsive to audiofre-' quency' electrical variations, electrical circuits connecting said pick-up'devices and said sound radiating device, and an electrical switch for transferring the effective connection to the input of the sound radiating device from the output fromone pick-up device to the output of the the output from one pickup device to the out-- put of the other pick-up device, of means under the control of said switch for effecting, in the course of the switching operation, gradual overlapping and complementary changes in the cir-' cuit impedance between each of'said pick-up devices and the sound radiating device. Y a

15. The combination with a pair of pick-up de vices for delivering audio-frequency electricalvariations; a receiver responsive to audio-frequency electrical variations, outputcircuits for the pick-up devices and an input circuit for the receiver, of adjusting means common tofsaid pick-up devices and connecting said output circuits to said input circuitfor gradually, oppositely, and simultaneously varying the effect of the respective pick-up devices on the receiver.

JOHN LOUIS REYNOLDS.

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