USRE22970E - begun r - Google Patents

Description

Feb. 10, 1948.

s. JIBEG UN I MAGNETIC SOUND RECORDING AND REPHODUCING Original Filed June 12, 1940 7 Sheets-Sheet 1 INVENTOR ATTORNEY Feb. 10, 1948. s. J. BEG-UN MAGNETIC SOUND RECORDING AND REPRODUCING Original Filed June 12, 1940 7 Sheets-Sheet 2 INVENTOR ATTORNEY Feb. 10, 1948. s. J. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING 7 Sheets-Shee 5 Original Filed June 12; 1940 Micmphane Volume 3mm 3 MAMRMLQL INVENTOR ATTORNEY.

Sam BY Feb. 10, 1948. 5, J, BEGUN Re. 22,970

MAGNETIC SOUND RECORDING AND REPRODUCING Original Filed June 12, 1940 'T Sheets-Sheet 5 I N VEN TOR.

1 Sen 11 Jbsep/r Begun BY 3 Liv/Mal 94 ATTORNEY Feb. 10, 1948. s. J. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING Original Filed June 12, 1940 7 Sheets-Sheet 6 3. NB- N wTm m m w mm 5% Feb. 10, 1948. s. .1. BEGUN MAGNETIC S'OUN'D RECORDING AND REPRODUCING 'r' Sheds-Sheet '7 Original Filed June 12, 1940 INVENTOR Sam? gonpfi BY Mkumfilw ATTORNEY Reiuued Feb. 10, 1948 MAGNETIC SOUND RECORDING AND REPBODUCING Semi J oseph Begun, Cleveland Heights, Ohio, as-

lignor to Magnetone, Inc., Cleveland, Ohio, a

corporation of Ohio Original No. 2,856,145, dated August 22, 1944, Se-

rlal No. 340,030, June 12, 1940. Application for reissue September 18, 194.6, Serial No.

33 Claims. 1

This application is a continuation-in-part of the copending application Serial No. 197,851, filed March 24, 1938, now Patent No. 2,224,854, granted Dec. 17, 1940, as a continuation-in-part of the copending application Serial No. 82,962, now abandoned.

This invention relates to magnetic recording and reproducing.

Among the objects of the invention are novel arrangements and methods for controlling the recording and reproducing operations of magnetic recording apparatus, some of which are of particular value in connection with speech correction, objective speech and language study and analogous applications.

The objects of the invention also include novel pole pieces, novel pole piece bobbins, novel pole piece magnetic heads, novel magnetic record transducing methods and arrangements, novel control arrangements, novel drives. and novel reel holders and reel holder arrangements for magnetic record transducing arrangements. The term magnetic record transducing" is used herein to designate either the process of recording electric signals into corresponding magnetic signal records impressed on a magnetic recording medium, or the process of reproducing magnetic records into electric signals, or the combination of both processes.

The foregoing and other objects of the invention will be best understood from the following description of exempliflcations thereof, reference being had to the accompanying drawings, wherein a Fig. 1 is a diagram illustrating the cooperative relationship of a magnetic recordin arrangement of the invention;

Figs. 2 and 3 are diagrammatic views of modifled forms of control arrangements for such recording arrangement;

Fig. 4 is a view similar to Fig. 1 of another form of the invention;

Fig. 5 is a side view of an amplifier chassis with a mechanical control mechanism of the type shown in Fig. 4;

Fig. 6 is a front elevational view of the ampliiier chassis of Fig. 5;

Fig. I is a cross-sectional detailed view of the control arrangement of Figs. 5 and 6;

Fig. 8 is a perspective view of the housing for a recording system of the invention equipped with a control mechanism of the type shown in Figs. 5 to '7;

Fig. 9 is a cross-sectional view similar to Fig. 7

2 of another control mechanism exemplifying the invention:

Figs. 10 and,11 are. views similar to Fig. 7 illustrating other forms of control arrangements with the associated control circuits;

Fig. 12 is a cross-sectional view similar to Fig. 7 of the control device shown in Fig. 11;

Fig. 13 is an elevational view of the control device of F18. 12;

Fig. 14 is a diagram illustrating another control arrangement for the recording system of the invention:

Fig. 15 is a circuit diagramof another-control arrangement for a recording apparatus of the invention; and.

Fig. 16 is a diagrammatic view of another form of recording and recording control arangement of the invention.

No person can hear his own voice as he hears the voices of others. This is due to the fact that all external sounds are transmitted to the inner ear of the listener through the air in the ear canal while the speaker receives much of the sound emitted by himself by conduction through the bones, the flesh, and other channels within his head.

Although the fact that a person cannot hear his own voice as he hears the voices of others has been known for a long time and there has long existed an urgent need for a simple device that would enable speakers. actors, singers,

students of elocution and foreign languagespersons having speech defects, such as stuttering and lisping, and all those desiring to hear their speech or voice, no simple, practical apparatus meeting these requirements have been available heretofore.

If the student could hear his own voice as he hears the Voices of others, he could readily perceive his mistakes. Only by hearing a good reproduction of his voice is the student able to study his voice objectively and improve and train it by self-correction.

In the past, only mechanical recording was available for voice training by self-correction. However, to make a disc record and play it back requires manual work and dexterity. In addition, each disc can be used for recording only once. Since voice training by self-correction requires recording and listening frequently to the recorded voice, a simple foolproof recording system requiring no special handling and enabling unlimited use of a single sound carrier would be ideal.

Furthermore, experience in voice training with aaavo mechanical sound recording has shown that the very fact that the student is aware, con-;.

sciously or subconsciously, that his recording remains permanent on the record and that each recording involves an expense sublects him to mental strain which prevents him from being his own self during the recording.v In most cases he must be assisted by another person in handling the recording apparatus, and the presence of any person prevents the student from recording in a relaxed mental state as he would ordinarily do if left by himself.

The present invention provides magnetic record transducing apparatus which makes possible recording and reproducing of sound records or the like while eliminating these difiiculties and making available an ideal medium for eil'ective voice study and training as well as speech correction.

A single recording medium is used over and over again for new voice records. A small magnetic recording head records and reproduces the speech without any observable change in the recording medium; the process of making a new record obliterates the preceding record. The speaker can hear his voice as soon as it is recorded, and can repeat the reproduction as many times as he desires. By a simple operation, the student may compare his own recording with a model record until by succession of his own recordings, he learns all his deficiencies and reaches an approach to the model record. The student is able to do it all by himself, without the presence of others, in a perfectly relaxed state, and is thus enabled to make great progress in a short period of time. a

All the operating and control elements of the recording and reproducing system are arranged and correlated to permit easy and economical construction and assembly of the apparatus of the invention and to assure its foolproof operation when in use.

Fig. 1 illustrates diagrammatically the cooperative relationship and the electric circuit connections of the various elements of one form of a magnetic recording apparatus arrangement exemplifying the invention.

It comprises a recording mechanism shown as a separate unit l-00, an amplifier arrangement shown as a unit 2-00, and a control unit, shown as a unit 2-00, each of the units being enclosed in a'separate casing, for instance, the

various elements of the several operating units" being interconnected by leads or interconnecting cords.

The recording mechanism l-00 comprises a frame structure, not shown, in which a magnetic record carrier, such as a recording track formed of tape l0i, of magnetizable material, is wound in the form of an endless helix, on a plurality of suitably-mounted spaced cylindrical guide rollers l-02, the loops of the helix having frictional driving engagement with the roller surfaces. A motor l-00, oi the squirrel-cage, induction-type, for instance, drives, through a belt l-Il, for instance, one of the rollers l-02, so as to impart to the magnetic tape i-0l uniform speed, in clockwise direction, for instance, as indicated by an arrow. A set =0! record transducing pole pieces 1-05, l-00, of magnetic material, having thereon transducer coils l-il, l0l. and an obliterating pole piece l01, having thereon an obliterating coil l-1l, arranged as a part of a magnetic transducer head, are pla'ced adjacent to a portion or the moving tape l0l. for making magnetic record transductions therewith, such 23 4 magnetic recordings, or reproducing the recordings therefrom.

The principles underlying the operation of such magnetic recording apparatus are explained in my paper published in the Journal of the Society of Motion Picture Engineers, vol. 28, 1931, pp. 464-472. 1

The amplifier arrangement 2-00 comprises an amplifier 2-0l, a power supply system 2-02 and a recording relay 2-01. The power supply ystem I 2-02 comprises a transformer 2-21 having a primary winding and secondary windlugs to which are connected a rectifier 2-22 and a illter network, formed of a choke coil, condensers and resistors connected through a lead 2-22 to ground and arranged to deliver at its terminals 2+20, 2+20, 2+21, filtered positive D. C. voltage required for operating the amplifier and other elements of the apparatus.

The amplifier 2-0 I, has, as shown conventionally, a grounded side, and an input lead 2-i 0, through which the input, that is to be a amplified, is impressed upon the amplifier. The amplified output is delivered by the amplifier through an output lead 2-08 either to a low impedance output lead 2-0! or by way of a transformer 2-02, or by way of coupling condenser 2-64 to a high impedance output lead 2-80.

The amplifier 2-0l may be of the conventional type and is designed to have a gain which is suflicient to deliver with an input voltage induced by a magnetic recording in the transducing coil windings l-ll, an output suflicient to operate a conventional loudspeaker. An equalizing network 2-0! is connected in the input circuit of the amplifier during the repreducing process and an equalizing network 2-50 is connected in the high impedance output circuitof the amplifier during the recording process, so as to give an overall amplification which secures high quality recording and reproduction of speech and music.

The recording relay 2-01 is of the conventional telephone relay yp In the form shown it has an actuating coil 2-10 and two sets of contact spring blades 2-1l to 2-12 and 2-12 to 2-10 which are normally biased to establish, in conjunction with their associated contact springs, the circuits required for reproducing a recording previously made on the magnetic carrier l0l. Upon energization of the recording relay coil 2-10, its contact spring blades are flexed to their opposite contact positions in which they establish the circuits to make a new recording on the magnetic carrier l0l.

There is also shown mounted on the amplifier casing 2-00 9. jack 2-0i, having a grounded 7 contact for connecting a cord plug from a ,blade 3-!0 is movable from the open position,

shown in the drawings, to the position I-l I, in which it connects the power supply lead 3+0 by way of a current limiting resistance 0+" and a lead 3+02 to one end of the primary winding of transformer 2-2l, the other end of which is connected to a cord extension or the other power supply lead 3-0 of opposite polarity.

The current limiting resistor 3+I3 through which the amplifier transformer 2-2i ls energlued in the standby position 3-l I, is so proportioned'as to apply a reduced voltage to the amplifier tube cathodes sufiicient to heat them to a recordingistobemadasuchas theiulllength I o! the endless tape, and the control mechanism sub-normal temperature and to enable rendering the amplifier i'ully operative the instant the en-- power supply lead 3-0 of opposite polarity,

thereby actuating the tape driving motor to drive a the tape at its normal uniform speed. A signal lamp 3l3 indicates the energized condition of the apparatus.

The control mechanism 3-03 is designed to enable selective control of the operating circuits required to make a new recording. In the form illustrated in the drawings, the control mechanism 3-03 comprises switch cam members 3-03, 3-03 arranged to be driven in a substantially synchronized relation to the travel of the magnetic carrier i-0l, in clockwise direction, for instance, by a small motor 3-01, through a reducing gear 3-ll and a friction coupling clutch 3-12. The clutch isarranged to be selectively actuated, for instance, by providing it with a cou. pling disc which is normally biased by a lever 3-13 to an uncoupled condition to break the driving connection between the switch cams 3-03, 3-03.and the synchronizing motor 3-l'l. A solenoid having a solenoid coil 3-13 serves to actuate the clutch coupling discs to the coupling position upon the energization of the solenoid coil.

A pointer knob 3-3l, extending from the switch cams 3-03, 3-03, and movable along a dial 3-32, enables manual rotation of the switch cams. When the coupling connection 3-03 is open, a return spring 3-33 automatically returns the switch cams 3-03, 3-03, and the pointer knob to the normal position shown in the drawings, a stop 3-34 serving to retain the pointer knob in the normal position.

Cam 3-03 operates 'a switch 3-3 which is I shown normally biased by its contact springs into a cam depression 3-30 so that its contact blades are flexed to their outward position when the cam 3-03 is turned from its normal position. Cam 3-03 serves to actuate a switch 3-3, which is normally biased by its contact spring to the open position shown in the drawings, and is arranged to be momentarily closed when the proiection 3-33 of cam 3-03 is given a slight clockwise turn, for instance. cam switch 3-8 is sufilciently damped so thatafter it is momentarily flexed to the closed position by turning the cam projection 3-00, it will aperiodically return to its normally open position and prevent the closure of its contacts when the cam 3-03 is returned to its normal position by spring 3-33.

In practice, the control mechanism 3-03 is so designed that substantially one full rotation ofthe synchronizing switch cam 3-03 corresponds to the full length or the tape track on which a The spring arm or the is so designed and arranged as to permit selective starting oi a new recording on any selected portion 01' the moving tape and to permit selective confining of a new recording to a'selected portion or the tape.

The dial 3-32 may be calibrated to indicate the progress of a recordingoperation in terms of the length of the recording period or the length oi the tape track on which a recordingis made.

The control mechanism 3-03 serves not only to control the length of the recording operation but also to indicate the progress or thetravel of the tape past the magnetic head and the progress of a new recording made on the magnetic carrier. Small standard, synchronous or slightly oil-synchronous motors, suitable for housing together with all the other elements of the control mechanism in a small portable casing, may be used to synchronize its operation to the motion of the tape-that is driven by a standard squirrel-cage induction-type motor.

The control mechanism 3-03 is so designed and arranged that upon g ving a slight turn to its switch cams 3-03. 3-03, iorinstance, by imparting a small turning motion to the pointer knob 3-3i, the cam discs actuate the spring contact switches to positions in which they establish circuits which effect a change in the operating conditions of the apparatus, in the present case, from a normal reproducing condition to a recording condition; and to maintain the recording condition for a predetermined length of the travel of the tape track.

The control arrangement may be combined with a separate recording starting switch 3-30 and-a separate recording stopping switch 3-03, which may be designed either for remote control operation. or for actuation by a push button mounted on the exterior oi the control unit, so as to enable starting and stopping of a new recording without direct manipulation of the control mechanism 3-03.

The control unit may have also mounted on its wall, a lack 3-3 I one side of which is grounded, for receiving the cord plug 3-32 leading to a shown in the drawings in which its contact springs establish the following record reproducingcircuits:

An amplifier input circuit from the transducer coil l-ll. in which the moving magnetic wave of the tape l-ll induces a signal voltage. through. cell lead l-33, byway of the cord, the closed recording relay contacts 2-13, the equalizing network 2-", and the recording relay contacts 3-13 to the input lead 2-l0 of the amplifier so as to impress thereon the signal voltage whichis to be amplified, the circuits being completed through the grounded sides of the transducer coil l -3l and the amplifier.

An amplifier output circuit from the secondary winding of the output transformer through the low impedance output lead 2-H, the closed to the amplifier input lead 3-", for impressing the microphone output on the input side of the amplifier M. The microphone M shown in the drawings is of a high impedance type, such as a crystal microphone, and requires no step-up transformer for coupling it to the input side of the amplifier.

An energizing circuit for the recording relay coil 2-10 and the clutch coil 3-15, from the positive power supply terminal 3+", through a lead including current adjusting resistor 3-53, recording relay coil 3-10, cord extension of lead 3-55, clutch actuating coll 3-15, the momentarily closed cam switch contacts 3-05, the closed cutoflf switch contacts 3-03 to ground, the circuit being completed by the grounded side of the filter.

At the same time, the synchronizing motor 3-01, one terminal of which is connected to the power supply lead 3-0 has its other terminal connected through the closed cam switch contacts 3-5l to the. power supply lead extension 3+0l of opposite polarity.

The so-energized synchronizing motor 3-01 will rotate the cam 3-05 and keep its cam switch A recording amplifier output circuit from the I high-impedance amplifier output lead 2-53, through the closed flexed recording relay contact 3-10, the recording equalizing network 3-50, junction lead 3-53, the closed flexed recording relay contacts 3-", the cord lead ex tension l-53 through the serially connected' transducer coils l-5I, 1-3! 01 the pole pieces l-5, l-3 to ground, the circuit being completed by the grounded side of the amplifier. The same circuit supplies to the transducer coils l-5l, i-3l, a superimposed D. C. depolarizing current through the connection to its lead 2-53 by way of a current adjusting resistor l-53, to the positive terminal 2+21 of thefilter rectifier circuit 3-02.

At the same time, there is also supplied a direct current to the obliterating coil l1l oi the obliterating pole piece l-01 from the positive filter terminal 2+31, through the current adjusting resistor l-10, closed flexed recording relay contacts 2-13, cord-lead extension l-13 and the obliterating coil l-1l to ground, the circuit being completed through the grounded side of the filter circuit.

Instead of using only the transducer coil l-5l for the reproducing process both serially connected transducing coils l-5l, l-3l may be used for recording as well as reproducing, in

- which case the lead l-33 is disconnected from transducer coil l-il and connected to the blade 3-5 in the flexed position in which its closed contacts 3-5I maintains the synchronizing motor 3-01 energized, while its contacts 3-53 en'- ergizes signal lamp 3-33 to indicate that the apparatus is in the recording condition. The simultaneously rotated switch cam 3-05, after momentarily closing cam switch 3-3, releases it to its open position, but the previously established energizing circuit for the recording switch coil 2-10 and the clutch coil 3-15, is not broken because a parallel locking circuit has been completed by the closed recording relay contacts 2-18, the closed cam switch contacts 3-52, the

leads 3-53, 3-51 and ground.

of the recording relay contacts 3-15 to which transducer coil lead l-53 is connected.

As explained hereinabove, the various elements of the apparatus shown in Fig. 1 are so arranged that when the energizing switch 3-l0 of the control unit 3-0315 in the "on" position 3-", the signal recorded on the tape is continuously reproduced. The control mechanism 3-03 of the control unit serves to selectively start a new recording at any selected time on any selected portion of the traveling magnetic tape l-0l, and, also, to indicate the progress of a recordin operation.

Under normal operating conditions, the synchronizing switch cam elements 3-05, 3-05 and the associated cam switches remain stationary The cam switch 3-5 remains in its outwardly flexed positionv until the cam 3-05 has made almost one full rotation corresponding to the length of a new recording made over the full length of the magnetic carrier l-0l on which a new recording is to be made. The synchronizing switch cam 3-05 is so shaped, proportioned and arranged that the moment a new recording has been made on the entire length or the tape on which a new recording is to be made, it releases its cam switch 3-5 to its normally biased unfiexed position in which it breaks at its contacts 3-53, the energizing circuit for the recording switch coil 2-10 and the clutch coil 3-15', and at its switch blades 3-5l, 3-53 the energizing circuits for the synchronizing motor 3-01, and signal lamp 3-23, respectively.

Thereupon, the recording switch is instantaneously returned to its normal reproducing position shown in the drawings, breaking at its contacts 3-18 the locking circuit which maintains it energized during the recording operation. The return spring 3-33 returns the cam discs 3-05, 3-05, to their normal position determined by stop 3-30, and since switch contacts 3-3 remain open, the recording switch coil 2-10 remains deenergized. All operating circuits of the apparatus are thus restored to their normal reproducing positions.

By manual actuation of the synchronizing cam 3-05, namely turning it by its pointer knob 3-31, against the friction of the clutch 3-13, the recording may be stopped at any time before the end of one rotation of the cam 3-05, or the recording may be limited to a desired length of the tape, as indicated on dial 3-3! when the recording is started by initially turning the pointer knob -3-3l to the desired point on the suitably calibrated dial scale.

An arrangement such as the cutoff switch 3-03, actuated by a simple push button, for instance, enables instantaneous stopping of a recording without directly manipulating any element of the sac-lo control mechanism 2-. On actuating the recording cutoil' switch 2-", the energized locking circuit for recording relay coil 2-" and the clutch coil 2-" are instantaneously deenergized. causing the switch cam 2-" to be returned by its biasing spring 2-42 to its normal position, thereby completing reestablishlng the reproducing-circuit connections. v

An arrangement, such as the starting switch 2- actuated by a Push button, ior instance. enables instantaneous startingot a new recording without manually actuating the control mechanism 2-03. on actuating the starting switch 3-80, its contact blades 3-12, which are connected parallel to the cam switch contacts 8-6 and 2-, complete the same starting circuits as are completed by giving a slight turn to knob 2-2! of the control mechanism 2-".

with such arrangement, momentary actuation of the starting switch 2-" will start a recording a at any time, on any selected portionol the tape.

and the recording will continue until a new recording on the full length oi the tape is made, unless by a momentary actuation of the recording cutofl switch 8-" the recording is stopped on any desired point of the moving tape, before one complete revolution oi the synchronizing cam 2-08.

In the operation or magnetic recording devices it is important to suppress any remanent magnetism left in the recording and obliterating pole pieces after the completion or each recording. In accordance with the invention such complete suppression of remanent magnetism may be e1- lected by subjecting the pole piece to a continuous small D. C. demagnetizing current acting in a direction opposite to the D. C. magnetizing current to which the pole pieces are subiected during the recording operation. The demagnetizing current is left flowing during reproducing as well as recording. and is adjusted to neutralize, or suppress any remanent magnetization left in the pole pieces after the transducer coils l-Ii, l-II. i-H are disconnected from their circuits and while they are not subjected to any other magnetizing force. This adjustment may be made while subjecting the pole piece to a l magnetic checking test, or by reproducing with a completely demagnetized tape.

Such arrangement is illustrated in Fig. 1. The pole pieces l-Il. l-li. l-OI oi the magnetic recording head are shown provided with additional coil windings l-I2, l-l2, l-I2, respectively, which are connected to be supplied with a highly filtered D. C. current derived, for instance, from the positive illter rectifier terminal 2+2] through a lead I-ll, a series resistor l-Il and shunt condenser 1-18 being interconnected with lead l-ll to provide additional illtration for the small demagnetlzing D. 0. current supplied therethrough. The additional coil turns 01' the transducer pole pieces and obliterating pole piece are so wound and the D. 0. current ilowing through them is so adjusted. as by the adjusting and decoupling rheostats l-ll. [-14, respectively, that any remanent magnetization in the pole pieces is neutralized to assure that traces of remanent magnetization in the pole piece material do not affect the reproducing operation and do not raise the noise level.

Fig. 2 illustrates a' modified form of control mechanism for a recording apparatus of the type shown in Fig. l, in which the rectifier-filter system 2-02 is modiiled to supply in addition to the relatively high D. C. ampliiler operating voltl0 age. a low operating voltage for the relay circuits. thereby eliminating the difficulties encountered when using high D. C. voltages for operating relay circuits. The rectiiier-illter network 2-" is shown modined by connecting a series resistor 2-22 in the filter ground lead 2-22 between the rectifier 2-22 and the filter ground. The series resistor 2-22 is proportioned to give a low D. C. voltage drop against ground, for instance, of the order of about 50 volts. such as used in ordinary telephone relay circuits. The recording relay coil 2-" is directly connected between ground and a tsp of the series resistor 2-22. The control mechanism [-02, which is shown in simplified form, is rearranged so that during the normal reproducing condition, the illter ground lead resistor 2-22 and recording relay coil 2-" are short-circuited, and thus de- I energized.

' In the control arrangement shown in Fig. 2. which is, similar to that of Fig. 1, this is accomplished by arranging the auxiliary cam switch contacts 2-! and the recording relay contacts 2-1! to remain normally closed and apply I through lead 3- a short-circuiting de-energizing ground potential to the illter lead resistor 2-22, which is removed only upon momentary actuation of cam switch 2-! when starting a recording. In additiomthe synchronizing switch contacts 3-82 are rearranged to be normally closed and complete through lead 2-51. a deenergizing locking short-circuit around ground lead resistor 2-22, which is opened when the recording starting turn is given to the synchronizing cam 2-".

As in Fig. 1, a recording may be started by giving a slight turn to the pointer knob 3- of the control mechanism 3-", thereby opening the two parallel de-energizing short-circuits at the cam switch contacts 2-! and at the synchronizing cam switch contacts 3-52 whereupon the recording relay is energized and actuated to the recording position in which its open flexed contacts 2-" open the de-energizing circuit leading through the momentarily opened cam switch contacts 2-. As a result, the short circuit across resistor 2-22 remains removed, and the full operating voltage remains applied to the recording relay coil 2-", while the synchronizing cam makes one complete revolution. unless it is previously returned to the normal reproducing position. by manually actuating knob 2-H.

As in the arrangement of Fig. l, the control arrangement of mg. 2 may be provided with a starting switch 2- and a cutoff switch 8-.-

The starting switch 2-" has only one pair of normally open contacts connected parallel to the synchronizing switch contacts S-Il, so that m upon-their actuation to the closed position, the

synchronizing motor 2-01, is immediately energized. The initial rotation imparted by the synchronizing motor 2-" to the control cams 2-", 2-", has the same eflect in starting a new Frecording as the manual actuation of the con trol cams 3-", 3- described above.

The cutofl switch 2-" has likewise only one pair of normally open contacts, connected parallel to the synchronizing switch contacts 3-52. so that upon its actuation to the closed position. during the recording operation, it momentarily completes a short-circuit across the voltage supply to the recording relay coil 2-", and momentarily deenergizes it. As a result. the deenergized recording switch 2-", in returning afterone complete revolution, the cam depression 3-50 returns the cam switch 3-5 to its normal position in which the synchronizing motor 3-01 and the recording signal lamp 3-29 are deenergized, thereby restoring all the operating circuits to their normal reproducing condition.

In this arrangement, only a simple friction clutch coupling 3-12 is provided between the synchronizing motor and the synchronizing cam 3-05, and the return spring 3-43 is eliminated. The control arrangement of Fig. 2 has thus all the advantages of the control arrangement of Fig. 1, except for the fact that ii the recording is cut off by its cutofl switch 3-09, a new recording cannot be started until the cam 3-05 has completed a full revolution and has returned the synchronizing cam switch 3-5 to its normal position.

In Fig. 3 is shown a simplified recording control arrangement for an apparatus of the type shown in Fig. 1. In this arrangement the synchronizing cam disc 3-05 with its cam switch 3-5 serve as the sole control element for selectively starting and stopping a new recording. The synchronizing cam switch 3-5 has only two sets of contacts 3-5I and 3-52, which, as in Fig. 2 control the energization of the synchronizing motor 3-01 and of the recording relay coil 2-10, respectively.

To start a new recording, a slight turn is given to the synchronizing switch cam disc 3-05 to complete at its closed flexed contacts 3-5i the energizing circuit for the synchronizing motor 3-01 and recording signal lamp 3-29 and at lead 3-55 the energizing circuit for recording relay coil 2-10 the other end of which is as in Fig.1, connected to a positive filter terminal 2+25, for instance.

As in the arrangement Fig. l, the synchronizing switch cam 3-05 and its drive are so arranged and proportioned that one complete rotation of the switch cam 3-05 corresponds substantially to a full length of the moving tape i-0l on which a new recording is to be made. As soon as the cam 3-05 has completed one rotation, its cam switch 3-5 is released into the cam depression 3-50, thereby breaking the recording switch coil circuit and the synchronizing motor energizing circuits, and instantaneously reestablishing the reproducing circuits. I

To stop the recording before the cam competes one revolution, the user has merely to manually turn the pointer knob 3-3! to its starting position, or to initially turn the pointer knob 3-3l to a point on the dial corresponding to the length or the tape on which he desires to make a recording.

By the new apparatus of the invention, a person desiring to learn a language is free from the burden of handling the recording medium, such as a disc or film. A student 0! speech or of a foreign language, can hear his own speech as soon as it is recorded and. without waiting, he may repeat the recording and reproducing oper its closed flexed contacts 3-52 completes through ations as many times as desired. By plu88 8 in a phonograph or radio receiver lead to jack 2-0 i he may record a model sound sequence from another record or a broadcast that he desires to imitate on a portion 0! the carrier and compare such model recording with his own recordings made on a diflerent'part of the carrier, which he is able to obliterate at any time by a new recording of his'own voice without obliterating the model recording.

The apparatus of the invention serves thus not only as a'simple foolproof mirror of the voice.

but it also enables a student of speech and languages to compare his own speech with a sample speech recorded from a phonograph or a radio on one portion of the tape, while he uses another portion of the tape for making his own record.

By combining the endless magnetic ,carrier with a control mechanism having a movable control member arranged to be selectively driven in predetermined synchronized relation to the moving carrier for controlling the duration oi the recording operation, a simple single grip control makes possible starting a new record on any selected portion of the endless carrier; and a simple single grip control makes it possible to confine the new recording to a selected portion of the endless carrier without obliterating a selected portion of a previous recording.

Fig. 4 illustrates a magnetic recording apparatus of the type described in connection with Fig. 1 having its elements arranged in a somewhat difierent way. It comprises a recording mechanism l00, similar to that of Fig. 1, an amplifier 2-0l having an input lead 2-l0 and an output lead 2-5l and a manually operated recording control switch 2-01 which, as in Fig. 1, has sets or springcontacts, which, in the shown normally biased position, establish the reproducing circuits and are arranged to be flexed for breaking the reproducing circuits and establishing the recording circuits.

The amplifier and the tape driving motor are arranged to be energized from supply leads 3-0, 3+0, and as in Fig, 1, an energizing switch 3-ll completes in position 3-l I an energizing circuit for the amplifier only, and in position 3-l2, an energizing circuit for the amplifier as well as for the tape driving motor l-03. There is also provided a control mechanism 3-03 for selectively controlling the recording operation as well as for indicating the progressive travel of the magnetic carrier l-0l during the recording operations.

The control mechanism comprises a synchronizing cam 3-05 arranged to be selectively coupled. as by a friction coupling clutch 3-12, to a shaft which is connected through a speed reduction gearing 3-1l to one of the tape guiding rollers 1-02, which are driven in synchronism with the tape l-0l. The speed reduction mechanism 3-1l is so designed as to impart to the synchronizing cam 3-05 one revolution during the time required for making a new recording on the substantially complete length of the endless carrier l-0 l.

The synchronizing cam 3-05 is shown in the form of a rotatably mounted disc having on one point of its periphery a depression 3-50 which in the position shown in Fig. 4 is engaged by a locking projection of a switch key 3-58 of the recording switch 2-01, the biasing action oi! the spring contacts of the recording switch 2-01 holding the switch key 3-50 in the locked position. The synchronizing cam 3-05 is also shown provided with a pointer knob HI for indicati ingonadial Hltheprogressivetraveloithe carrier I-ll when the synchronizing cam 3-" is unlocked and is driven by the motion coupling 3-12 in predetermined synchronized relation to the travel or the magnetic carrier tape l-li.

The cam disc 3-33 with its synchronizing drive, the recording switch 2-01 and their associated elements are so designed and proportioned that when the key 3-" is actuated to release its locking engagement with the cam depression 3-50, the synchronizing cam 3-05 is driven by its coupling clutch 3-12 during one iull revolution while the outer cam surface of the synchronizing cam 8-33 holds the key in the lifted position in which it actuates the contacts springs 01 the recording switch 1-01 to their flexed position in which they establish the recording circuits; and to cause the biasing action 01' the spring contacts or the recording switch 2-" to their normal reproducing positions to return and to actuate the switch key 3-" into its looking engagement with the cam depression 3-80 of the synchronizing cm 3- at the end or one revolution the synchronizing cam, and thereby reestablish reproducing conditions.

In the normal operating position. shown in Fig. 4. in which the synchronizing cam 3-5 is held locked in stationary position by the switch key 3-", the contacts oi the recording switch 2-01 remain in their normally biased unfiexed position in which they establish the following record reproducing circuits:

From the ungrounded side of the serially connected transducer coils l-Il, I-Bl in which the moving magnetic wave oi the tape induces a sig nal voltage, through lead l-il, by way of the normally closed recording switch contacts 2-12 to the amplifier input lead 2-" for impressing on the amplifier the signal voltage which is to h amplified, the circuits being completed through the grounded side or the transducer coil l-ll and the grounded side oi the amplifier.

The amplified output is delivered by the ampliher through a circuit including amplifier output lead 2-", the normally closed recording switch contact 2-18 to the reproducer R, the circuits being completed by the grounded side of the amplifier 2-3! and the grounded side or the reproducer It.

When the key 3-" of the recording switch is actuated to unlock the synchronizing cam 3-05 and to fiex the contacts oi the recording switch 2-31, itsfiexed'blades, which remain in the flexed recording position while the synchronizing cam 3-03 rotates, establish the following recording circuits:

A recording amplifier input circuit from the amplifier input lead l-lll, through the flexed closed recording switch contacts 2-12, to a tap oi' the volume control potentiometer 2-32, one side of which is connected through a contact at the phonograph jack 2 -33, to ground. The other end or the volume control potentiometer 2-33 is connected by way or a jack 2-" to a microphone M, indicated as a carbon microphone, to which its small exciting current may be supplied i'rom a dry cell 2-". As shown in Fig. 4, the dry cell 3-" is normally disconnected from the operating circuits by the normally open relay contacts 2-, which are closed only when the associated relay coil 3-11 is energized upon the actuation of the power supply switch 3-" to the position 3- in which the amplifier as well as the tape driving motor l-l3 are energlad.

In the arrangement shown, the amplifier input circuit from the carbon microphone M i co pleted through the upper contact of the microphone iack 2-ll. the closed flexed recording switch contacts 3-33, closed relay contacts 3-". to one terminal of dry cell 2-"; the other terminal of which is grounded. Ii. a record is to be made from a phonograph pick PU, its plug is inserted into the pickup Jack 2-83,

thereby flexing its upper spring contact and connecting the phonograph plckuppotentiometer 2-34 to the amplifier input circuit instead or the microphone potentiometer 3-82.

The recording amplifier output is delivered through output lead 3-" to the closed flexed recording switch contacts 3-"; output volume control potentiometer 3-" and from the tap o! a potentiometer by way 01a serially connected condenser, through, the closed fiexed recording switch contacts 2-", and, transducer lead l-II to the serially connected transducer coils l'll, l-il and therethrough to ground. the volume control potentiometer 3-38 permitting adjustment of the input to the transducer coils for optimum recording conditions. The additional contact spring of the closed flexed recording switch contacts 2-33 also completes additional D. C. supply circuits from dry cell 2-88 through lead l-l3 by way of current adjusting resistor [-56 to the serially connected transducer coils l-il, l-GI, for impressing thereon the polarizing current required for recording, and through current adjusting resistor l-li to the obliterating coils l-H' for impressing thereon the current required for obliterating the previous recording. .The circuit from cell 2-8! is prepared by closure of the normally open contacts 3-33 of relay 2-3! when the supply switch l-lfl is actuated to its fully energizing position 3-l2.

The recording arrangement described in connection with Fig. 4 enables the user to start a new recording at any time, at any selected point of the moving carrier tape l-lll, by merely actuating the button of recording switch key 3-" to unlock the synchronizing cam 3-05 which is driven for the duration of one complete revolution by the friction coupling clutch 3-13, while its pointer knob l-3l indicates on the dial 3-33 the progress or the recording, until. at the end of one complete revolution oi. the synchronizing cam 3-05, the switch key 3-83 is returned by the biasing action 01' the switch springs into lock-' ing engagement with the locking depression 3-", thereby locking the' synchronizing cam 3-05 in the way shown in Fig. 4.

By actuating switch key 3-58 to the unlocking position at a selected point of the travel of the carrier tape, and turning the synchronizing cam 3-05, by means of the pointer knob 3-3l, to a selected portion 01' the dial, for instance, to a point from the normal position, only the next following halt of the tape length will be recorded while leaving on the preceding halt oi the tape length a previously recorded sequence that is to be reproduced. Similarly, a recording operation that has been started, may be stopped at any point of the tape, as indicated on the dial 3-32, by turning the pointer knob 3-3l and returning manually the synchronizing cam 3-".

to its locked position shown in Fig. 4.

Flexible control of the recording and the res, producing operations is thus secured. Upon the completion of each recording the entire recording on the tape is reproduced and the reproduel tion of the recording on the tape is continuously repeated until a new recording is made.

In Figs. 5 to 8 is illustrateda practical form' of a manually operated control arransement 01' the type shown diagrammatically in Fig. 4.

The control arrangement 9-99 is part of the chassis of the amplifier 2-111, which is mounted,

in conjunction with the frame structure, on which the tape rollers 1-92 and the associated tape driving and guiding elements are mounted inside a housing 9-ll.' The amplifierchassls has an exposed panel wall 9-12 and the c ntrol mechanism is mounted on the panel wall.

One of the tape rollers 1-92 drives through a suitable speed reduction mechanism. such as a flexible shaft 9-19 and a worm gear 1- mounted on a control shaft 9-19 of the control mechanism which is revolvablv'mounted in an opening of the panel 9-12 and ahole of a bracket 91-19 secured to the panel 9-12. The worm gear 9-14 of the flexible shaft is suitably fixed,

9-12 and serves as the bearing-for the front end of the control shaft 9-19. Oil impregnated washers 9-29, of felt or similar material, are placed adjacent the bearing surfaces of the revolving elements of the control mechanism to maintain the bearing surfaces lubricated and assure quiet operation.

To th projecting stub shaft end 9-19 of the control disc 9-19 is secured a pointer 9-21 which serves also as a grip for rotating the control disc 9-19 relatively to the coupling disc 9-11. A dial 9-22 with a suitable scale is mounted on the panel behind the pointer 9-21, and the reduction gear drive connection between the control shaft 9-19 and its drivingroller 1-92 is so proportioned and arranged'that when the control disc 9-19 is coupled to the coupling disc '9-11, the control disc 9-l9 will make one complete revolution when the guide roller has made the number of revolutions required to pass one complete length of the endless carrier 1-91 through the magnetic head 1-9, while the move ment of the pointer 9-21 along the scale of the dial 9-22 indicates the progress of the travel of the complete length of the endless carrier.

The periphery of the control disc 9-19 has a stop notch 9-25 shaped to engage a control rod 9-29 slidably mounted in a bushing 9-21 extending through the panel wall 9-12 so that when the control rod 9-29 is in the position shown, the control disc 9-19 will remain locked in place and will not be rotated by the coupling disc 9-11. On applying pressure to button grip 9-29 of the control rod-9-29 andpushing it inwardly till its annular groove9-29 releases the control disc 9-19, so that it is now free, the control disc is rotated by the worm-driven coupling disc 9-11. The slowly revolving periphery of the control disc-9-19 engages the groove 9-29 of the control rod 9-29 and holds it in the inward dotted-line position until after one complete revoward locking position to which it is biased by the spring blades of the recording switch 2-91 pressing on the switch cam' provided on the inward end of the control rod 9-29.

The control rod 9-29 may be arranged for actuation by a flexible push rod extension 9-91 which is enclosed in a flexible tube 9-32 having a coupling collar 9-99 which is detachably coupled to the bushing 9-21, so that by actuating push rod 9-91, the plunger attached to its inner end will actuate the control rod 9-29 to release the control disc 9-19.

In Fig. 9'is shown a modified form of control mechanism of the type described in connection with Figs. 5. to 8. A control shaft 9-19 journalled in the amplifier is driven by-a worm gear 9-14 in definite correlation to the; travel of the endless magnetic carrier 1-91. To the outer end of the control shaft 9-16 is secured a dial 9-99 having a peripheral scale on which a pointer 9-99 mounted on the panel indicates the progressive travel of the endless carrier 1-91.

A control disc 9-19 which is revolvably journalled to a control shaft 9-19 is frictionally cou pled to the shaft by a coupling disc 9-l1 which is slidingly keyed on the shaft 9-16 and is pressed against the control disc 9-19 by its coupling spring, the several elements being seated on the shaft between oil impregnated felt washers 9-29 to secure quiet and smooth operation or all the moving parts.

The control disc 9-19 may be locked in a stationary position and prevented from rotation by the locking engagement of its peripheral stop notch 9-25 with the lock arm 9-41 of a control lever 9-42 which is pivotally mounted on a pivot pin 9-49 and has a stop 9-44 engaging one side of the control lever 9-42, so that by tilting the control lever 9-42 against the pressure of an adjustably mounted biasing spring 9-49, the lock arm 9-41 may be swung out ofits looking engagement with the stop notch 9-29 of the control disc 9-19 to release it and permit it to be rotated by the coupling disc 9-11 in. correlation with the travel of the carrier 1-91, while the lock arm 9-41 is held in its unlocked position by the periphery ,of the rotating control disc 9-19. until'after one complete revolution the biasing spring 9-45 returns the lock arm 9-41 into its locking engagement with the control disc 9-19 to stop its further rotation. However, the articulated knee junction between the lock arm 9-4l and its control lever 9-42 makes its possible to return the control lever 9-42 to its normal position shown at any time during the rotation' of the control disc 9-19, while the lock arm 9-41- sion of the control lever member 9-42, so that upon moving it from its normal locking position shown to the unlocking position in which the control disc is released, for one complete revolution, the lever cam 9-41 will move to the dotted-line position and actuate the switch cam 9-99 to flex the contact blades of the recordingswitch 2-91 to their recording position. The lever cam 9-41 and the associated elements of the control mechanism are so arranged that the spring forces exerted thereon by the flexed blades 01' the re.

To this end, the actuating cam 9-59 of Y cordingswiteh' 2-91 will look the lever cam 9-41 in'the'-dotted-line position once the cam 9-41 has been moved from the normal fullline position past the unstable equilibrium position to the unlocking position in which the control disc 9-" is released for one complete revolution; and to return the control lever 9-42 to its normalposition shown once it has been moved on its return path to bring its cam 9-41 on its return path beyond its unstable equilibrium point to its normal full-line position.

By combining a control arrangement of the type shown in Fig. 9 with an endless carrier magnetic recording reproducing apparatus in the way described above in connection with Figs. 1 to 4, the portion of the traveling carrier which passes through the magnetic head isat all times" indicated on the revolving dial. When the amplifier and the driving motor are energized, the entire sound sequence recorded on the endless carrier will be continuously repeated as long as the control lever member 9-42 is left in its normal position. To start a new recording on a selected portion or the endless carrier, the recording lever 9-42 is actuated against the pressure of its biasing spring 9-95 to release the control disc cam 9-" from its engagement with the lock arm 9- and to flex the contact blades of the recording switch 2-01 to the recording position. The new-recording starts thus simultaneously with the releasing of the control cam 9-l9 for one complete revolution, and the full length of the carrier l-ili passing through the magnetic head l-5 is recorded during one complete revolution of the dial 9-95.

Upon completion oi a, recording on the entire length of endless carrier, as indicated by one complete revolution of the dial 9-95, the lock arm 9- which has been riding along the periphery of the control cam 9-" is automatically returned by its biasing spring into the locking slot 9-25 of the control cam 9-l9, thereby stopping its rotation, while at the same time the lever arm 9-42 and the switch cam 9-59 are returned to their normal position shown, thereby releasing the contact blades of the recording switch to their normal reproducing position. The apparatus will thereupon repeat the newly recorded sound sequence and continue to repeat it until either the motor is stopped or a new recording is started.

A new recording may be confined to a selected portion of the endless carrier as indicated on the scale of the rotating dial 9-95 by swinging the tilted control lever 9-42 with its lever cam 9-" from the dotted-line recording position to the normal full-line position, thereby releasing the flexed spring blades of the recording switch 2-01 to their normal reproducing position, while the lock arm 9- is still riding along the periphery of the control disc until it is released into the lock notch of the control cam 9-l9 at the end of a complete revolution. The return of the control lever 9-42 to its normal position before the control cam 9-i9 completes a full revolution enables instantaneous return of the record-' ing switch 2-01 from its recording position to its normal reproducing position so as to confine the new recording only to a portion of the endless carrier as selected by the scale of the revolving dial 9-22. This arrangement enables the student to compare his own new recording on a selected portion of the endless carrier with another specimen recording, for instance, of a phrase recorded by a teacher, or from a phonograph record. or from a radio broadcast. he may repeat making his own new recording as. often as he desires until he is satisfied that he learned to imitate the specimenrecording.

The control mechanism of Fig. 9 with the articulated control lever members 9-, 9-92 for starting and stopping the revolving control cans pletion of each recording, the new recording as well as the selectively retained previous recording may be reproduced as many times as desired.

In Fig. 10 is shown a modified form of a control arrangement for selectively starting and stopping the recording operation on the endless magnetic carrier in a way similar to the arrangement of Fig. 9. Itcomprises a control shaft 9-15 with an indicating dial 9-95 and a friction coupling 9-" for selectivly coupling a control cam disc 9-i9 to the.control shaft 9- which is driven by a reduction gear mechanism 9-" so that one revolution of the dial corresponds to the travel or .the entire length of the endless carrier through the magnetic head. i

The control disc 9- is normally locked in a stationary position through the engagement of its lock hole 9-59 with a lock pin 9-5! of a lock magnet 9-52 arranged to release the control disc 9- when the magnet winding is energized from a supply source indicated by plus and minus signs, upon the closure of a normally open contactor 9-53. The recording switch 2-91 with its block of normally unflexed spring contact springs is arranged to be actuated to the flexed recording position by a magnet 2-19 when its windings are energized by the closure of an actuating circuit including the normally open'control-cam actuated contactor 9-55 and the normally open control-lever actuated contactor 9-55.

When the control cam 9-" is in its normal locked position shown, its contactor 9-55 is released to its open cam notch position and it is flexed to the closed position when the control cam 9-i9 is released and rotated by the coupling disc 9-".

The other contactor 9-55 is arranged to be closed by a cam 9-58 of a control level 9-49 pivotally mounted on a bracket so that when the lever 9-59 is tilted to the dotted-line position 9-59, its cam 9-59 closes the contactor 9-59. the cam 9-58 being retained in the contactor closing position by the spring pressure of the contactor blade. A handle 9-5i pivotally Joined to the control lever 9-59 and biased by a relatively strong spring against a stop 9-54 of the control lever 9-59 is so arranged that in swinging handle 9-H to bring the control lever 9-" to the dotted-line position, the handle 9-5! is tilted until its projecting knob closes the contactor 9-53 and energizes the lock relay 9-52 to release the control disc 9-l9. These actions bring about the closure of the two contactors 9-53, 9-59 and the energization of the switch magnet 2-19 which actuates the recording switch 2-91 to'the. recording position. As soon v as the handle 9-51 is released, its biasing springv returns it against the stop of the control lever ,,9-59, thereby .de-energizing the lock magnet 19 9-92 while the lock pin rides on the surface oi the revolving control disc 9-i 9.

The control arrangement shown in Fig. will operate in combination with an endless magnetic sound carrier in a way similar to the control arrangement of Fig. 9. In the normal reproducing position, the control disc 9-l9 is held locked by the lock pin of the lock magnet 9-92; the control disc contactor 9-99 is released to its open position by the control disc notch 9-29; the switch magnet 2-19 is kept de-energized by the open contactors 9-99, 9-99; and the blades of the recording switch 2-91 min the unilexed normal reproducing position.

To start a new recording on a selected portion of the endless carrier as indicated on the scale of the revolving dial 9-99, the lever handle 9-9l is tilted to close the contactor 9-99 and bring the control lever 9-99 with its cam 9-99 to the dotted-line position, thereby locking the contactor 9-99 and its cam 9-99 in the closed position while the released control disc 9-l9 closes its contactor 9-99. As a result, the switch magnet 2-10 is instantaneously energized to actuate the recording switch 2-91 to the recording position and start the recording operation. The new recording starts simultaneously with the release of the control disc 9-i9 and the full length of the endless carrier I-ll passing through the magnetic head l-9 will be recorded during one complete revolution of the dial 9-99.

Upon the completion of the new recording on the entire length of the endless carrier, the lock pin 9-9l locks the control disc 9-l9 in its normal position in which its contactor 9-99 is released to its open position, de-energizing the recording switch magnet 2-19 and releasing its flexed blades to their normal reproducing position.

A new recording may be confined only to a selected fraction of the endless carrier as indicated on the scale of the revolving dial 9-99 by tilting the control lever 9-99 to its normal position shown before the control disc 9- l9 has completed a full revolution, thereby de-energizing the switch magnet 2-10 and releasing the recording switch 2-91 to the normal reproducing position, whereupon the new recording as well as the retained previous recording will be reproduced as many times as desired.

In Figs. 11 to 13 is shown another control arrangement for selectively recording only on a portion of the endless carrier. It comprises a revolvably mounted control shaft 9-l9 which is driven by a worm drive 9l9 and drives through a friction coupling disc 9-l1 to control cam discs 9-1l and 9-12. The control disc 9-1i has a shaft extension 9-19 which is journalled in a hollow shaft extension 9-19 of the second control disc 9-12. The two control discs 9-11 and 9-12 are arranged to be adiustably coupled to each other by a semi-circular coupling plate 9-19 secured to the shaft projection 9-19 of the control disc 9-1l and a coupling plate 9-19 slldingly keyed on the hollow extension 9-19 of the coupling disc 9-12 and pressed by a coupling spring into coupling engagement with the semi-circular coupling plate 9-19.-

In the form shown in Fig. 13, the coupling connection is eflected by the engagement of a coupling pin projection 9-19 of the coupling plate 9-15 with one of a semi-circular row of coupling holes 9-1-9 of the coupling plate 9-19. This makes it possible to adjust the angular cou- 9-19. 9-19 y fl pp the knurled edge of the circular coupling plate 9-19 and after pushing it rearwardly to disengage one of its coupling holes 9-19 from the coupling pin 9-19, turn itby the desired angle, and release another of its coupling holes 9-19 intocoupling engagement with the coupling pin 9-19 of the semi-circular coupling plate 9-19. Any other simple adjustable angular coupling connection, such as serrated coupling surfaces, may be used instead.

As indicated in Rig. 13 by the shading W and B, one hall of the front surface of the coupling plate 9-19 and the front surface of the semi-circular plate 9-19 are of one color, white, for instance, and the other half of the coupling plate 9-19 which has the row of coupling holes is 0! a different color, red. for instance, so that the exposed red segment of the plate 9-19 indicates at a glance the relative angular coupling displacement between the two control discs 9-1l and 9-12. The two control discs 9-1l and 9-12 are provided with control notches 9-9l, '9-92 for controlling the operation of two contactors 9-99, 9-99, respectively, and the angular displacement of the coupling plates 9-19, 9-19 shown by their colored segments indicated the angular displacement of the control notches 9-9 i -9-92 of the two control discs.

As shown in Fig. 11, the recording switch 2-91, with its block of spring contact blades and supplemental contact blades 9-99, 9-99, are arranged to be actuated from the normally unflexed reproducing position to the\i'iexed recording position by a switch magnet 2-10 which is energized from a supply source, indicated by plus and minus signs, through an actuating circuit which is controlled by the control disc contactors 9-89, 9-99 and a starting button 9-91 in con- Junction with an auxiliary relay -989 having normally open contact blades 9-89 and a selector switch 9-90 having contact blades 9-9i, 9-92, 9-99, '9-99 cooperating with a set of double throw contacts as shown in the drawings.

The control arrangement shown diagrammatically in Fig. 11 will operate in combination with a magnetic recording and reproducing apparatus such as shown diagrammatically in Fig. 1 as follows: As long as the main motor and amplifler supply switch are closed and the recording switch is in its normal reproducing position, the endless carrier I-9I and the two control discs 9-1l, 9-12 will be continuously driven and the traveling carrier will continuously reproduce all the sound sequences recorded on the endless carrier, while the progress of the reproduction is indicated by the pointer on the dial scale of the continuously revolving coupling plate 9 19. In other words, the reproducing operation proceeds in the same way as in the arrangement described in connection with Fig. 1.

The control discs 9-1l, 9-12 which revolve in unison with the travel of the endless carrier through the magnetic head are used for controlling the actuation of the recording switch 2-91 to selectively start or stop the recording on the entire length of the endless carrier or on a selected portion of the endless carrier depending on the position of the selector switch 9-99 and the angular displacement of the control discs 9-1l, 9-12 as indicated by the dial segments of their coupling plates 9-19, '9-19. If the selector switch 9-99 is in the position shown in Fig. 11, indicated by the arrow R, a new repling relation between the two coupling plates 7 cording started by the closure ofthebutton switch H1 will be confined to the portion of the en less carrier corresponding to the red segment R of the dial plates l-Il. If, on the other hand, the selector switch 9-" is in the other position, indicated by the arrow W, a new recording started by the closure oi the button switch 9ll will confine the new recording to the portion of the endless carrier corresponding to the white segment W of the dial plates lll, Oll. The simple angular adjustment or the coupling connection between the two control discsl'|l, ll2, as indicated by the colored dial plate segments, in conjunction with the simple' a'ctuation' oi the selector switch 9-", make it thuseasy to control the selective recording on selected portions of the carrier.

Thus, if a new recording is to be made on the portion oi the endless carrier indicated by the red "segment of the dial plates 0-15, l-II, the

selector switch 9- is placed in the position indicated by the arrow R as-shown in Fig. 11. Thereupon,-' each time a new recording confined to this. selected portion of the endless carrier is to b'e 'made; the user has merely to close starting switch l-Ql for a moment, This completes an energizing circuit for the starting relay 9-4! which is connected to the minus terminal, from the plus terminal of the relay supply, through the closed starting switch 8-81, and the blade 1-" of the recording switch 241. The energization o! the starting relay 9-" completes a locking circuit at its inner contracts, and it remains locked until its locking circuit is opened at the contact blade 8-8! of the recording switch 2-0! when the recording switch relay 2-10 is energized-;"--' The closed'startin'g relay contacts 9-" prepare an actuating circuit for the recording switch magnet .2-|0 leading from the minus supply terminal, through the winding of magnet l-ll; by way of the closed selector switch contactsQ-fll to the open contacts of the control disc switch 0-, and therefrom through the closed selector blade contacts 9-83 to the plus supply terminaL the circuit being completed when thefnotch oi the revolving control disc Hfreleases its'contactor 9-84 from its flexed position and through the energization oi the recording switch magnet 2-10 actuates the recording switch to start the recording operation. The energization of the recording switch magnetz- -1o eil'ects also the closure of its lock-in contacts 9-" which complete its lock-in circuitleading Irom the positive supply terminal through the closed selector contacts 9-, the closed contacts of the control disc contactor 9-83, the closed selector switch contacts 3-", the closed relaylock-in contacts 0-" and the winding 0'! the recording switch magnet 2-10 to the negative'supply terminal. At the same time, the energization of the recording switch magnet 1- opens at its contacts 9-88 the lock-in circuit of the starting relay 9- and thereby returns its contacts to their normal open positions.

The recording operation, which was thus started when the control disc switch 9-84 was ,momentarily released from its flexed position into no'tch 8-82 of the revolving control disc cam [-12, will now continue until, as indicated by the motion 01' the red dial segment past thepointer 8- the notch HI 0! the revolving control disc S- II releases its associated contactor from its flexed position, thereby breaking at its normally closed contacts the lock-in circuit oi the recording'switch magnet I-ll, and by resulting de-energization or the recording switch magnet i-Il returns the recording switch 1-" to its normal reproducing position.

The user will then hear the reproduction of the retained part or the previous recording, as indicated by the white part ,W of the dial, followed by the reproduction of his new recording, as indicated by the red part of the scale. He may make new recordingsand hear the retained recording and his new. recordings as many times as he desires by merely pressing the button of the starting switch HI each time he desires to make a new recording.

By moving the selector switch l-OI to the opposite position, in the direction of the arrow W, any new recording started by the momentary closure 0! the starting switch 1-" will be confined to the length oi the endless carrier corresponding to the white segment W-W oi the dial, and once the new recording is made, the retained sound sequence corresponding to the dial segment R with the newly recorded sequence corresponding to the segment W will be continuously repeated until a new recording is substituted for the last recording on the length corresponding to the segment W of the dial. Once the starting switch H1 is momentarily closed, the apparatus will be automatically switched over for recording when the front edge of the white segment area of the revolving dial reaches the pointer HI and the recording period will be automatically stopped when the rear edge of the white segment reaches the pointer 8-", whereupon both recorded sequences of the endless carrier will be continuously repeated until a new recording is to be made on the portion of the endlesscarrier corresponding to the white:

segment 01 the'rei'rolving dial.

This arrangement makes it thus possible to apportion one length of the carrier for recording thereon a model sentence or paragraph, for instance, by a teacher, which should remain on the endless carrier for a substantial period of time, while reserving for the pupil the remaining portion of the endless carrier for repeatedly making his own recordings until he is satisfied that his own recording approaches the standard of the model recording. With such arrangement, once the teacher has made a model recording on one section of the endless carrier as indicated on the'dial, he merely has to throw the changeover switch into the other position. whereupon the'pupil may make as many recordings as he desires on the portion of the endless carrier reserved for him until he has completed his training.

Although the friction coupling connection between the controlfshaft 9-H and the control disc 9- -18 is not required for the operation of the control arrangement of Figs. 11 to 13 in the way described above, this friction coupling makes it possible to independently turn the intercoupled control discs l|l, 8-12 relatively to the coupling plate 0-11 for independently selecting the portion of the endless tape upon which the new recordings are to be started.

In Fig. 14 is shown another type of control arrangement oi the invention which makes it possible to continuously reproduce only a selected the user desires to play back only a selected short sound sequence, such as a single sentence.

An endless carrier l-ll, which is driven at a uniform speed along a plurality of guide rollers ll2 has, in addition to a main magnetic head i--I with obliterating magnets l-l'l and transducer magnets i-Ii, several additional sets of transducer magnets iliA, i-ll-B, l-flS-C, located at different selected points along the path of the endless carrier. To simplify the description, the four sets. of transducer magnets are shown spaced from each other by one-quarter of the total length of the carrier.

The recording and reproducing operations are controlled by a control mechanism which comprises a control shaft 9Il which drives through a friction coupling disc l-il a control disc cam 8-" so that when the control disc l-ll-is released, it will make one revolution while the entire length of the endless carrier: passes through the magnetic head. The control disc l- -il cooperates with an articulated control lever arrangement 9-, 9-42 of the type shown in connection with Fig. 9 for selectively actuating a recording switch 2-01 to start a new recording operation on a selected portion. of the endless carrier and to automatically-stop the recording operation and start the reproducing operation after one complete revolution of the control disc 9-", or to stop the recording operation by actuating the lever handle -42 to release the switch 2lll from its recording position while the lock member of the control lever HI is still riding on the periphery of the revolving control disc 9-48 in the way explained in connection with Fig. 9. If desired, the fully automatic control arrangement. ofl'ls. 11 may be for controlling the recording operation.

The control shaft 9il is arranged to revolve a pair of contact wiper arms 'll-i i', ill-i2 along insulatingly mounted segments of the split contact rings iii-l3, il-H of a rotary switching device illill. The switching device ll-ill may be angularly revolved, as by means of a handle or a friction roller iii-Ii operated through a flexible shaft so as to, permit adjustment of the phase relation of the contact segments ill-ll, V

ll-H with respect to the moving endless carrier i0l. I

A switch ill--i6 having a blade movable between the position shown, in which it completes a circuit connection to the lead l-JI connected to the transformer windings of the magnetic head i-B, and two otherpositions, in which it completes circuit connections to the switch'wipers [0-H and Ill-i2, respectively, is associated with the rotary switching device ll'll in performing the control operations. An amplifier 2i|0 and a recording switch 2,-01 are arranged to establish the reproducing'circuit connections to normally play back a recording made -on the endless tape, and to selectively establish the recording circuit connections 'when the control switch is actuated by the control lever 0-42 to flex its blades from the the normally biased reproducing position to the flexed recording position.

Further details of the control arrangement of Fig. 14 will be clear from a description of its operation. It is assumed that the driving motor, not shown, has been energized to drive the endless tape on which a recording "has been made, and that the operating circuits'are in the condition shown in the figure. I

In this position. the following circuits are establiah d f r reproducing from thetransducer windthe'volume control potentiometer il-II connected thereto, through the unfiexed recording switch blade 2-12, to the input lead I-ll'of the amplifier, the amplified output being delivered through output lead 2-", by way of the recording switch blade contacts I'|6, to the reproduce!" R. .5

Accordingly. the previously made recording from the entire length of the endless tape l-ll will be reproduced. To make a recording, the recording control lever 9-42 is actuated to release the cam 8-", thereby actuating the blades of the recording switch 2-01 to the flexed recording position in which they are maintained for. one full rotation of the control disc l-il.

In this flexed recording position, the flexed blades of the recording switch 2 l'l break the reproducing circuit connections and establish the following recording circuit connections: A recording amplifier input circuit from the amplifier input jack 2-, the closed flexed recording switch blades 2'|i', to the primary winding of the input transformer ifl-ll, and from "the'lsecondary winding of the input transformer il -II, through a tap of the recording volume control potentiometer iii-l9, the closed flexed contacts of the recording switch blade 2-H, tothe input lead 2-H] of the amplifier 2-40: 'I'hereoordin: output is delivered through amplifier recording output lead 2-58, the closed flexed'recording switch blades 2-18 and lead l l, to the serially connected transducer windings I LII, i-Ii to ground. I

At the same time, there is also supplied it D. C. obliterating current from the positive supply lead l-ll extending from the p. Q. filter network of the amplifier, through the flexed closed contacts of the recording switch blade 2 |l, to the lead I-Jl the obliterating coils l'| i' oi the magnetic head l-I, the flexed recording switch blade'2|l the transducer coils l-il' of the magnetic 'head 1 l-i for superimposing on the recording A. C. currents the required D. C. polarizing current. Accordingly, the apparatus will be in th? recording condition and enable the making of a. recording on the entire length of the t m b of the magnetic head l-I. f

The provision of the rotary switching device Ill-ill, the wipers of which are revolved in synohronism with the movement of the tape, and the associated selector switch ill-JO, makes it possible to selectively confine the play backfl-from the recording so made on the tape to only a portion of the tape. Thus, by moving the selector'switch llii to the position in which it completes a circuit from the recording switch blade 2-" to the rotary wiper iii-i i, therevolving wiper il-li will, during each full revolution, successively engage the four segments of the contact ring Ill-l3 leading to the four sets of the transducing coil windings |-,5| i5lA, l-.--6|B, i'Ii--C, thereby successively connecting another transducing winding to the input side of the amplifier during each revolution of the wiper. As a result, the rotating wiper ll-ll will, after each ,quarterof a'revolution of the control shaft,

I through selector switch blades some establish circuit connections for playing back the same sequence recorded on a quarter or the length of the endless carrier, without playing back the record made on the remaining threequarters of the endless carrier.

In a similar way, when the arm of the selector switch Ill-l6 is moved to the position in which it completes a circuit to the selector switch wiper III-Ii, the latter will, in the course of each revolution, establish successive engagement with-the contact segments illll connected to the transducer input windings i-Il and l-iB tor successively playing back the recording onone selected half of the endless carrier, without playing back the record on the other half of the carrier.

This arrangement enables the user to start the reproduction of a sound sequence on a selected portion of the moving endless carrier as indicated on the dial by turning the switching device ill-l0 either by the handle or by the remote control drive 9-" to the desired angular position. After the switching device ll-lli has been turned to the right position, the selected sound sequence'wili be continuously reproduced without reproducing the other parts of the recorded sound.

By providing a selector switch Ill-l8 with a larger number of selector contacts and a corresponding wiper switch Ill-ll, the reproducing process may be confined to any selected fraction of the endless carrier and the user may quickly select any desired short part'of the endless carrier for reproducing.

Fig; shows how the recording control mechanism of Fig. 14 is applied to such apparatus. A control can 9-" is driven through a friction coupling drive at a speed correlated to the travelof the endless carriers, and an articulated control lever 9-, 9-42 associated with the control cam 9-" controls the operation of the recording switch 2-01.

A key-operated multi-blade selector switch Illmay be actuated by a cam movable from the neutral position shown in the drawings for selectively confining the recording or reproducing operations to the endless carrier l-ll-A or to the positions indicated by the arrows B, C for recording and reproducing sound on the endless carriers l-lll-B or i-li-C.

When the selector switch lO-Il is in its position shown in the drawings, the following circuit connections for reproducing and recording connections by means of the sound carrier i-M-A are established: The obliterating winding l--Il of the magnetic head i-5-A is connected ill-28 and il-2I to a contact of the recording switch blade 2-" through which a magnetizing current is supplied during a recording operation: the transducer winding i-Bi of the magnetic head l-I-A is connected through selector blades iii-28 and Ill-22 to the center contact of the recording switch blade 1-15 through which the transducer winding is connected either to the amplifier input winding 2-" for reproducing or to the output transformer winding 2-52 for recording, while the recording switch blade 2-44 supplies through resistor i-BB the depolarizing current to the transducer windings i-5l.

Accordingly. as long as the selector switch iii-20 is in its neutral position, the transducer and obliterating coils of the magnetic head l-i-A will operate in conjunction with the amplifier 2-00 under the associated recording control arrangement to selectively reproduce orrecord sound on the tapeas in the arrangements 0! Fig. 1 or 9.

When the selector switch ill-20 is actuated to the position indicated by the arrow B, its flexed blades break at the contacts Ill-2|, iii-22, Ill-23 the recording and reproducing connections to the magnetic head i5-A of the endless carrier liI|-A. and establishes the following reproducing and recording connections to the magnetic head l--i-IB of the carrier l-ill-B: Its obliterating coil l-ll is connected over the closed lock-out switch iO-Il through the flexed selector blade IIII to the outer contact of the recording switch blade 2-", through which a magnetizing current is supplied during the recording operation; and its transducer coil i-Bl is connected through the flexed selector blade l022 to the recording switch blade 2-15, through which the connection is completed to the input lead 2-" o! the amplifier for reproducing sound from tape i-ill-B, or in the flexed recording switch position, through the closed lock-out'bypass contacts ill-42, by way '0! the unflexed selector contacts Ill-29, to the amplifier output lead 2- for recording sound on the tape l-li-B.

'When the selector switch "-20 is flexed to the position indicated by arrow 0, it breaks at the flexed blades "-28, "-49 the recording and reproducing connections to the magnetic head i-B-A of the endless carrier i-iii-A, and establishes the following reproducing and recording connections for the magnetic head l-S-C of the endless carrier i-lli-C. Its obliterating coil IIi is connected over the closed lock-out contacts ll83, through the flexed selector blade "-25 to the recording switch blade 2-", through which a magnetizing current is supplied to the obliterating coil during the recording operation; and its transducer coil i--5i is connected through the flexed selector blade iD-fl to the recording switch blade 2-15 through which the connection is completed either to the input lead of the amplifier for reproducing sound; or in the flexed recording switch osition, by way of the unflexed selector contact iii-2i and the lock-out bypass contacts i034 to the amplifier output lead 2-83 for recording sound on the magnetic tape i-ili-C.

The arrangement described above in connection with Fig. 15 makes it thus possible to selectively reproduce or record on either one of a plurality of magnetic carriers. By a simple manual or remote-control actuation of the selector switch ill-2 0, either one of the several magnctic carriers may be connected for recording and reproducing sound in conjunction with a common amplifier 2-" under the utilization of one or the various recording control arrangements described hereinabove.

The two sets of lock-out contacts iii-3|, Ill-32 and lB-fl, ill-I4 are associated with the circuits to the tapes i-Ili-B and l-fli-C, respectively, and are so arranged that the opening of one set of lock-out contacts disables the recording circuit connections of the respective magnetic heads, so that as long as a lock-out switch is open, it is only possible to reproduce, and it is impossible to record on the particular tape. The lock-out switches may have the form of removable plugs, or may be key operated so as to prevent recording as long as they are locked in the open position.

A sound recording and reproducing apparatus

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