US2356145A - Magnetic sound recording and reproducing - Google Patents

Description

Aug. 22, 1944. s. J. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING Filed June R. 1940 '7 Sheets-Sheet l I I l l I I l I I I I I I I I I I I l I I I I I I I n? v0 INVENTOR .Se/mi Jmep @aga/m,

BY e MMQIML ATI'ORN E V Aug. 22, 1944. s, J, SEGUN 2,356,145

MAGNETIC SOUND RECORDING AND REPRODUCING ATTORNEY Aug. 22, 1944. s. J. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING Filed June 12, 1940 7 Sheets-Sheet 4 LLLHLULL 204 0 INVENTOR. Semi lass/:: Begun BY S MMCLQAPM ATTORNEY Aug. 22, 1944. s. .1. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING Filed June l2, 1940 7 Sheets-Sheet 5 INVENTOR Sem: Jose/nh Begun BY www.; 2.5

A TTORNEY Aug- 22, 1944. s. J. BEGUN 2,356,145

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Semi Josep/1 Begun BY S im @Il Pm A TTORNEY Aug. 22, 1944. 2,356,145

S. J. BEGUN MAGNETIC SOUND RECORDING AND REPRODUCING Filed June 12. 1940 7 Sheets-Sheet 7 0 INVENTOR BY Meh AWWA ATTORNEY Patented Aug. 22, 1944 UNITED STATES PATENT OFFICE MAGNETIC SDUND RECORDING AND BEPEODUCING Semi Joseph Begun, Cleveland, (lhlo, assignor to Magnetone Inc., Cleveland. Ohio, a corporation 28 Claims.

This application is a continuation-impart of the copending application Serial No, 197,851,1iled March 24, 1938, as a continuation-impart of the copending application Serial No. 82,962.

'Ihis 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 oi 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 arrangementsv for magnetic record transduclng 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 exempiications thereof, reference :zeing had to the accompanying drawings, where- Fig. 1 is a diagram illustrating the cooperative relationship of a magnetic recording 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 oi an ampliiler chassis with a mechanical control mechanism of the type shown in Fig. 4;

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

Fig. 7 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 'l;

Fig. 9 is a cross-sectional view similar to Fig. 7 of another control mechanism exemplifying the invention;

Figs. 10 and 1l are views similar to Fig. "I 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. 1l;

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

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

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

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

No person can hear his own voice as he hears the voices of others. 'I'his 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 languages, persons 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 oi 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 mechanical sound recording has shown that the very fact that the student is aware, consciously or subconsciously, that his recording remains permanent on the record and that each recording involves an expense subjects him to mental strain which prevents him from being his own sell during the recording. 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 ii' left by himself.

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

A single recording medium is used over and over again tor 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. 'Ihe 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.

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 oi a magnetic recording apparatus arrangement exemplifying the invention.

It comprises a recording mechanism shown as a separate unit I tl, an ampliner arrangement shown as a unit 2 lll, and a control unit. shown as a unit 3 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 of interconnecting cords.

The recording mechanism I lll comprises a frame structure. not shown, in which a magnetic recorde carrier, such as a recording track formed of tape I lii, of magnetizable material, is wound in the form of an endless helix. on a plurality oi' suitably-mounted spaced cylindrical guide rollers I II, the loops of the helix having frictional driving engagement with the roller surfaces. A motor I iil, of the squirrel-cage, induction-type, for instance, drives, through a belt I Sl, for instance, one of the rollers I Il, so as to impart to the magnetic tape I-OI uniform speed, in clockwise direction, for instance. as indicated by an arrow. A set of record transducing pole pieces l-IS, I l, of magnetic material, having thereon transducer coils I II, I Ii, and an obliterating pole piece I II, having thereon an obliterating coil I li, arranged as a part of a magnetic transducer head. are placed adjacent to a portion of the moving tape I lll, for making magnetic record transductions therewith, such as magnetic recordings, or reproducing the recordings therefrom.

I'he principles underlying the operation ot such magnetic recording apparatus are explained in my paper published in the Journal o! the Society of Motion Picture Englneerss, vol. 28, 1937, pp. 464-472.

The amplifier arrangement 2 00 comprises an amplifier 2 lli, a power supply system 2 0! and a recording relay 2 0?. The power supply system 2 0! comprises a transformer 2 2! having a primary winding and secondary windings to which are connected a rectifier 2 23 and a filter network, formed of a choke coil, condensers and resistors connected through a lead 1 to ground and arranged to deliver at' its terminals 2+", 2+", 2+2I, iiltered positive D. C. voltage required for operating the amplifier and other elements of the apparatus.

The amplifier I l, has, as shown conventionally, a grounded side. and an input lead 2 il, through which the input, that is to be amplified, is impressed upon the ampliiler. 'I'he amplified output is delivered by the ampliiier through an output lead 2 0! either to a low impedance output lead 2 6! or by way of a transformer 2 l2, or by way of coupling condenser 2-84 to a high impedance output lead 2 63.

The ampiiiler 2 Ill may be of the conventional type and is designed to have a gain which is sufficient to deliver with an input voltage induced by a magnetic recording in the transducing coil windings I BI, an output suiiiclent to operate a conventional loudspeaker. An equalizing network I li is connected in the input circuit of the ampliiier during the reproducing process and an equalizing network 2 50 is connected in the high impedance output circuit of the ampliiier during the recording process. so as to give an overall amplification which secures high quality recording and reproduction oi speech and music.

The recording relay 2 01 is of the conven tional telephone relay type. In the form shown it has an actuating coil I 'll and two sets of contact spring blades I II to 2 13 and 2 14 to 2 1 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 I l. Upon energization of the recording relay coil 2 1. its contact spring blades are ilexed to their opposite contact positions in which they establish the circuits to make a new recording on the magnetic carrier I M.

There is also shown mounted on the amplifier casing 2 Iil a Jack I ll, having a grounded contact for connecting a cord plug from a phonograph pickupor a microphone M to the input side of the ampliiier.

The apparatus is shown designed for energizetion from a domestic alternating current (A. C.) power supply circuit through two supply-leads I+II, l-I of opposite polarity. `An energizing switch having a contact blade I Il which may be actuated, for instance. by a pointer knob I l, serves to energize or deenergise the operating circuits of the apparatus. The energizing switch blade I il is movable from the open position. shown in the drawings, to the position I i i, in

which it connects the power supply lead I+! by way ci' a current limiting resistance I-l-lt and a lead I+II to one end o! the primary winding o! transformer 2 2l, the other end of which is connected to a cord extension of the other power supply lead I l 0f Opposite Polarity.

The current limiting resistor 3+!! through which the amplifier transformer 2 2! is energized in the standby position 3-i I, is so proportioned as to apply a reduced voltage to the amplifier tube cathodes suflicient to heat them to a sub-normal temperature and to enable rendering the amplier fully operative the instant the energizing switch blade 3-I0 is moved from position 3-ii to position 3--l2, in which the transformer 2-2I is fully energized from the power supply lead 3+Il.

When the energizing switch blade 3-l0 is moved to the position 3--i2, it also completes an energizing circuit from the power supply lead I-i-U, by way of lead 3+Ii| and its cord extensions to the tape driving motor I-03, the other terminal of which is connected to an extension of the power supply lead 3-0 of opposite polarity, thereby actuating the tape driving motor to drive the tape at its normal uniform speed. A signal lamp 3-i9 indicates the energized condition of the apparatus.

'I'he 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 3-05, 3--06 arranged to be driven in a substantially synchronized relation to the travel of the magnetic carrier i-lli, in clockwise direction, for ing stance, by a small motor 3-01, through a reducing gear 3-1I and a friction coupling clutch 3-12. The clutch is arranged to be selectively actuated, for instance, by providing it with a coupling disc which is normally biased by a lever 3-13 to an uncoupled condition to break the driving connection between the switch cams 3-05, 3-06 and the synchronizing motor 3 4". A solenoid having a solenoid coil 3-15 serves to actuateit'he clutch coupling discs to the coupling position upon the energization of the solenoid coll.

A pointer knob 3-3I, extending from the switch cams 3|l5, 3-il6, 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-li5, 3-ii6, and the pointer knob to the normal position shown n the drawings, a stop 3-34 serving to retain the pointer knob in the normal position.

Cam 3-05 operates a switch 3-5 which is shown normally biased by its contact springs inf to a cam depression 3-50 so that its contact blades are flexed to their outward position when the cam 3--05 is turned from its normal position. Cam 3--06 serves to actuate a switch 3 5, 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 projection 3-60 of cam 3-06 is given a slight clockwise turn, for instance. The spring arm of the cam switch 3-6 is sufficiently damped so that after it is momentarily ilexed to the closed position by turning the cam projection 3-60, it will aperiodically return to its normally open position and prevent the closure of its contacts when the cam B-BB 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 of the synchronizing switch cam 3--05 corresponds to the full length of the tape track on which a recording is to be. made, such as the full length of the endless tape, and the control mechanism lili is so designed and arranged as to permit selective starting of a new recording on any selected portion of the moving tape and to permit selective confining of a new recording to a selected portion of the tape.

The dial 3--32 may be calibrated to indicate the progress of a recording operation in terms of the length of the recording period or the length of the tape rack on which a recording is made.

The cont ol' mechanism 3-03 serves not only to control the length of the recording operation but also to indicate the progress of the travel oi' the tape past the magnetic head and the progress of a new recording made on the magnetic carrier. Small standard, synchronous or slightly off-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-Ii3 is so designed and arranged that upon giving a slight turn to its switch cams $-Ii5, 3-ll6, for instance, by imparting a small turning motion to the pointer knob 3-31, 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 3-90 and a separate recording stopping switch 3-09, which may be designed, either for remote control operation. or ior actuation by a push button mounted on the exterior of the control unit, so ns 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 jack 3BI one side of which is grounded, for receiving the cord plug 3-82 leading to a reproducer such as a loudspeaker R. A volume control potentiometer 3--83 mounted on the control unit enables adjustment of the volume of the sound delivered by the reproducer R.

When the energizing switch l-iil is in its on" position 3-i2, in which the amplifier and the tape driving motor I03 are fully energized, a record previously made on the magnetic carrier I-ill will be reproduced, and the reproduction will be continuously repeated, the recording relay 2-01 remaining biased in the normal position shown in the drawings in which its contact springs establish the following record reproducing circuits:

An amplifier input circuit from the transducer coil i--SL in which the moving magnetic wave of the tape |-0I induces a signal voltage, through coil lead I-BB, by way of the cord, the closed recording relay contacts 2-13, the equalizing network 2-05. and the recording relay contacts 2--12 to the input lead 2-I0 of the amplifier so as toimpress thereon the signal voltage which is to be amplified, the circuits being completed through the grounded sides of the transducer coil I-SI and the amplifier.

An amplifier output circuit from the secondary winding of the output transformer through the low impedance output lead 2-6I, the closed contacts 2-18 of the recording switch` by way of the cord lead extension of the reproducer lead l-ll to volume control potentiometer l-ll and Jack l-li to the reproducer R, the various circuits being completed through the conventionally indicated grounded sides of the output transformer winding and the Jack.

In order to make a recording. the recording relay 2-01 is energized to establish in the ilexed position oi its contact blades the following circuits: 1 A recording ampuner in t from the microphone M; for instance,` through lack I-II, the closed ilexed recording relay contact 1 to the amplier input lead !-il, for impressing the microphone output on the input side oi' the smpliiler 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.

A recording ampliiler output circuit from the high-impedance amplifier output lead 2-43. through the closed flexed recording relay contact 2-14. the recording equalizing network I-Il, liunction lead 2--l8, the closed exed recording relay contacts !-|5, the cord lead extension I-il through the serially connected transducer coils I-ll. i-tl of the pole pieces |-l, I-l to ground, the circuit being completed by the grounded side of the amplifier. The same circuit supplies to the transducer coils i--IL l-II, a superimposed D. C. depolarizlng current through the connection to its lead 2 5! by way of a current adiusting resistor i-il, to the positive terminal I+II o! the illter rectiller circuit l-II.

At the same time, there is also supplied a dlrect current to the obllterating coil i-ll of the obliterating pole piece i--II from the positive illter terminal I+II. through the current adjusting resistor closed ilexed recording relay contacts 2-1I, cord-lead extension i-ll and the obllterating coil I-Ii to ground, the circuit being completed through the grounded side of the lter circuit.

Instead of using only the transducer coil I--SI ior the reproducing process both serially connected transducing coils i-Il, i-ll may be used for recording as well as reproducing. in which case the lead i--sl is disconnected from transducer coil I-Ii and connected to the blade oi the recording relay contacts l-ll to which transducer coil lead I- is connected.

As explained hereinabove. the various 'elements oithe apparatus shownlnFlg.l aresoarranged that when the energizing switch S-Il oi the control unit I-Il is in the "on" position l-il.

the signal recorded on the tape is condnuously reproduced. The control m loi' the control unit serves to selectively start a new recording at any selected time on any selected portion of the traveling magnetic tape i-li, and,also. toindlcatetheprogressotarecording operation. l

Under normal operating conditions, the synchronizing switch earn elements Hl, I-ll and the associated cam switches remain stationary in their positions shown in Figrl.

Anewrecordingmaybestartedbygivinga slightturntothepointerknob l-Il oi'thecontrol mechanism t-II thereby momentarily closing its cam switch H and closing cam switch t-I in which position they establish the following operating circuits:

An energizing circuit for the recording relay coil I-Il and the clutch coil t-Jll. from the 1l postitlve power supply terminal I+. through a lead including current adjusting resistor I-ll. recording relay coil 2 1.. cord extension o! lead I-It, clutch actuating coll I'|I. the momentarily closed cam switch contacts Hl, the closedtmh switch contacts I-II to the clrcul g completed by the grounded side or the ma.

At same time. the synchronizing motor t-l'l. one terminal of which is connected to the powermpplyleadl-Dhasitsotherterminal connected through the closed oam switch contacts 3--Ii to the power supply lead extension I+II of opposite polarity.

The so-energized synchronizing motor I-ll will rotate the cam 8-08 and keep its cam switch H in the ilexed position in which its closed contacts I-Ii maintains the synchr motor S-II energized, while its contacts I-II energizes signal lamp I-Ili to indicate that the apparatus is in the recording condition. The simultaneously rotated switch cam i-ll. after momentarily closing cam switch l-I, releases it to its open position, but the previously established energizing circuit for the recording switch coll 2-10 and the clutch coll l'il, is not broken because a parallel locking clncult has been completed by the closed recording relay contacts l-ll, the closed cam switch contacts H2, the leads I-II, 3-51 and ground.

The cam switch I-i remains in its outwardly ilexed position until the cam I-Ill has made almost one lull rotation corresponding to the length of a new recording made over the full length of the magnetic carrier I-ti on which a new recording is to be made. The synchronizing switch cam 8-05 is so shaped, proportioned and arranged that the moment a new recording has been made on the en length ofthetapeonwhichanewreco gistobe made, it releases its cam switch l-l to its normally biased unilexed position in which it breaks at its contacts l-II. the energizing circuit for the recording switch coll I-'Il and the clutch coil l-, and at its switch blades l-II, l-II the energizing circuits for the synchronizing motor Hl, and signal lamp l-ll. respectively.

Thereupon, the recording switch is instantane ously returned to its normal reproducing' position shown ln the drawings, breaking at its contacts I-'Il the locking circuit which maintains it encrgined during the recording operation. The return spring 3-83 returns the cam discs Hl. l-lt. to their normal position determined by stop l-Il, and since switch contacts I-O remain open, the recording switch coil 2-`Il remains deenergized. All operating circuits of the apparatus are thus restored to their normal reproducing positions.

By manual actuation of the synchronizing cam 1 namely turning it by its pointer knob I-II, against the friction o! the clutch I-ll. the recording may be stopped at any time before the end o! one rotation oi' the cam 3 0. or the recording may be limited to a desired length ol the tape. as indicated on dial I-li when the recording is started by initially turning the pointer knob l-II to the desired point on the sultably calibrated dial scale. v

An arrangement such as the cutoil switch I-Ol. actuated by a simple push button. for instance.

enables instantaneous stopping o! a recording without directly manipulating any element of the control mechanism I-. 0n actuating the recording cutoi! switch l-dl, the energized locking circuit for recording relay coil 1-10 and the clutch coil 3 1! are instantaneously deenergised. causing the switch cam I-Irl to be returned by its biasing spring t-Il to its normal position, thereby completing reestabiishing the reproducing circuit connections.

An arrangement. such as the starting switch l-ll actuated by a push button. for instance, enables instantaneous starting of a new recording without manually actuating the control mechanism 3 03. On actuating the starting switch 3-00, its contact blades HI, which are connected parallel to the cam switch contacts 3-5 and I-ll, complete the same starting circuits as are completed by giving a slight turn to knob I-Il o! the control mechanism 3-01 With such arrangement, momentary actuation of the starting switch twill start a recording at any time. on any selected portion of 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 cutoil switch 3-08 the recording is stopped on any desired point oi the moving tape. before one complete revolution of the synchronizing cam l-llt.

In the operation of magnetic recording devices it is important to suppress any remanent magnetism left in the recording and obliterating pole pieces after the completion of each recording. In accordance with the invention such complete suppression oi remanent magnetism may be effected by subjecting the pole pieces 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 subjected during the recording operation. The demagnetizing current is leit 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 |5|, I-GI, l-'II 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 magnetic checking test, orby reproducing with a completely demagnetized tape.

Such arrangement is illustrated in Fig. 1. The pole pieces i-II5, I-Ilt, I-Il'l oi the magnetic recording head are shown provided with additional coil windings |-52, i-62, I--12, respectively, which are connected to be supplied with a highly filtered D. C. current derived, for instance, from the positive iilter rectifier terminal 2+21 through a lead l-l, a series resistor I-lil and shunt condenser I--18 being interconnected with lead I-' to provide additional illtration for the small demagnetizing D. C. current supplied therethrough. The additional coil turns of the transducer pole pieces and obliterating pole piece are so wound and the D. C. current iiowing through them is so adiusted, as by the adjusting and decoupling rheostats i-5I, i-1l, 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 aiIect the reproducing operation and do not raise the noise level.

Fig. 2 illustrates a modiiied form oi control mechanism for a recording apparatus of the type shown in Fig. l, in which the rectiiier-iilter system 2--02 is modiiled to supply in addition to the relatively high D. C. amplitler operating voltage, a low operating voltage for the relay circuits, thereby eliminating the dimculties encountered when using high D. C. voltages i'or operating relay circuits. The rectifier-mier network 2-ll is shown modied by connecting a series resistor 2-22' in the illter ground lead 2-22 between the rectier 2-23 and the lter ground. The series resistor 2-12' is proportioned to give a low D. C. voltage drop against ground, for instance, oi the order of about 50 volts, such as used in ordinary telephone relay circuits. The recording relay coil 2-10 is directly connected between ground and a tap of the series resistor 2-222 The control mechanism -Ilt which is shown in simplied form. is rearranged so that during the normal reproducing condition, the filter ground lead resistor 2-22' and recording relay coil 2-1ll are short-circuited, and thus deenergilied.

In the control arrangement shown in Fig. 2, which is, similar to that of Fig. 1, this is accomplished by Varranging the auxiliary cam switch contacts 3 8 and the recording relay contacts 2-18 to remain normally closed and apply through lead 3--56 a short-circuiting de-energizing ground potential to the iilter lead resistor 2-22', which is removed only upon momentary actuation of cam switch I-B when starting a recording. In addition, the synchronizing switch contacts 3-52 are rearranged to be normally closed and complete through lead l-tl, a deenergizing locking short-circuit around ground lead resistor 2--212 which is opened when the recording starting turn is given to the synchronizing cam #-05.

As in Fig. 1, a recording may be started by giving a slight turn to the pointer knob 3-3i o! the control mechanism 3-03, thereby opening the two parallel de-energiaing short-circuits at the cam switch contacts 3--8 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 exed contacts 2-18 open the de-energizlng circuit leading through the momentarily opened cam switch contacts 3 6. As a result, the short circuit across resistor 2-22 remains removed, and the full operating voltage remains applied to the recording relay coil 2-10, while the synchronizing cam makes one complete revolution, unless it is previously returned to the normal reproducing position, by manually actuatir'g knob l-ll.

As in the arrangement o! Fig. 1, the control arrangement of Fig. 2 may be provided with a starting switch 3-90 and a cutoii' switch 3-09. The starting switch 3-90 has only one pair o! normally open contacts connected parallel to the synchronizing switch contacts 3-5I, so that upon their actuation to the closed position, the synchronizing motor l-IIL is immediately energized. The initial rotation imparted by the synchronizing motor l-ll to the control cams 3-05, 306, has the same eiIect in starting a new recording as the manual actuation oi the control cams S-t, 3-08 described above.

The cutoil switch 3-09 has likewise only one pair ci 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 2-10, and momentarily deenergizes lt. As a result. the deenergized recording switch 2-1I, in returning to the normal reproducing position. instantaneouslv closes its locking contacts z-n, re-

6 nasales establishing a deenergizing ground connection he may record a model sound sequence from anto the rectiiier end oi' the ground lead resistor other record or a broadcast that he desires to 2 22', and short-circuiting the energizing imitate on a portion of the carrier and compare source of the recording relay coil' 2 1.. The such model recording with his own recordings synchronizing cam switch. I l still remains in 5 made on a dinerent part of the carrier. which its outward position while its cam is being ro.. he is able to obliterate at any time by a new retated by the energized synchronizing motor cording ci his own .voice without obliterating the I ii'i, until after one complete revolution, the model recording.

cam depression I ll returns the cam switch The apparatus of the invention serves thus not I I to its normal position in which the synl0 only as a simple foolproof mirror oi' the voice. chronixing motor I ol and the recording sigbut it also enables a student of speech and lannal lamp 8 29 are deenergized. thereby restoring guages to compare his own speech with e sample all the operating circuits to their normal respeech recorded from a phonograph or a radio `producing condition. on one portion oi' the tape, while he uses enthis arrangement. only a simple friction is other portion of the tape for making his own clutch coupling I i! is provided between the record. synchronizing motor and the iiynchronizing cam By combining the endless magnetic carrier I ll. and the return spring 3 3! is eliminated. with a control mechanism having a movable The control arrangement oi' Fig. 2 has thusall control member arranged to be selectively driven the advantages o! the control arrangement of in predetermined synchronized relation to the Fig. 1. except for the fact that ii' the recording moving carrier i'or controlling the duration oi' is cut on' by its eutoil' switch 3-49, a new rthe recording operation. a simple single grip eording cannot be started until the cam 3 l5 control makes possible starting a new record on has completed a full revolution and has returned any selected portion ol' the endless carrier; and the synchronizing cam switch 3 5 to its normal 25 a simple single grip control makes it possible to position. corinne the new recording to a selected portion In Fig. 3 is shown a simpiiiied recording conof the endless carrier without obliterating a setrol arrangement for an apparatus ot the type lected portion oi' e previous recording.

shown in Fig. 1. In this arrangement the syn- Fig. 4 illustrates a magnetic recording appachronizing cam disc I Il with its cam switch ratus of the type described in connection with I I serve as the sole control element for se- Fig. 1 having its elements arranged in a somelectiveiy starting and stopping a new recording. what diirerent way. It comprises a recording The synchronizing cam switch 3 5 has only mechanism I IIII. similar to that of Fig. 1, an two sete ot contacts I li and I ll, which, as ampliiier 2 0! having an input lead 2 Iii and in Fig. 2 control the energization ot the syn- 3s an output lead 2 lii and a manually operated chronialng motor O II and' oi the recording rerecording control switch 2 01 which, as in Fig. lay coil I il. respectively. 1, has sets of spring contacts, which, in the To start a new recording. a slight turn is shown, normally biased position. establish the given to the synchronizing switch cam disc 3 0! reproducing circuits and are arranged to be to complete at its closed flexed contacts I Ii 40 iiexed for breaking the reproducing circuits and the energizing circuit for the synchronizing motor establishing the recording circuits. 3 01 and recording signal lamp 3 2. and at The ampliier and the tape driving motor are its closed flexed contacts I W completes arranged to be energized from supply leads 3 0. through lead I lli the energizing circuit for 3+il. and as in Fig. 1, an energizing switch recording relay coil 2 1! the other end of which 45 3 iil completes in position I ii an energizing is as in Fig. 1. connected to a positive nlter tercircuit for the ampiier only. and iny position minal 2+, for instance, A 3 I2, an energizing circuit for the amplifier as As in the arrangement of Fig. 1, the synchro. well as for the tape driving motor I ot. 'I'here nizing switch cam 3 0! and its drive are so aris also provided a control mechanism I ll for ranged and proportioned that one complete roselectively controlling the recording operation as tation of the switch cam lcorresponds sub- Well as for indicating the progressive travel oi' stantially to a full length of the moving tape the magnetic carrier I tl during the recording i-ll on which a new recording is to be made. operations. As soon as the cam 3 II has completed one Ihe control mechanism comprises a synchrorotation. its cam switch yI--s is released into ninna com #-05 arranged to be selectively coupled, as by a friction coupling clutch 8 12, to recording switch coil circuit and the synchrca shaft which is connected through a speed reously reestabiishing the reproducing circuits. rollers I II, which are driven in synchronism To stop the recording before the cem comwith the tape I iii. The speed reduction mechpietes one revolution. the user has merelytomano enism 3 ll is so designed es to impart to the ually tum the po vr knob I M to its starting synchronizing cam 3 06 one revolution during position, or to ini itily turn the pointer knob the time required for making a new recording 3 3i to a point on the dial corresponding to on the substantially complete length oi' the endthe length of the tape on which he desires to less carrier I ill. make a recording. The synchronizing cam 3 05 is shown in the By the new apparatus of the invention, a perform of a rotatably mounted disc having on one on desiring to learn a language is free from the point of its periphery a depression 3 50 which in burden of handling the recording medium, such the position shown in Fig. 4 is engaged by a as a disc or film. A student of speech, or of a locking projection of a switch key 3 6! of the foreign language, can hear his own speech as recording switch 2 01, the biasing action of the soon as it is recorded and, without waiting. he spring contacts of the recording switch 2 01 may repeat the recording and reproducing operholding the switch key 3 5! in the locked posiations as many times as desired. By plugging in tion. The synchronizing cam 3 05 is also shown a phonograph or radio receiver lead to Jack I li. Provided with a pointer knob 33| fOr indicatassaut '7 ing on a dial 3-32 the progressive travel of the carrier I-Ol when the synchronizing cam 3-05 is unlocked and is driven by the friction coupling l-'l in predetermined synchronized relation to the travel of the magnetic carrier tape i-IIL The cam disc I-lll with its synchronizing drive, the recording switch 2-01 and their associated elements are so designed and proportioned that when the key I-III is actuated to rclease its locking engagement with the cam depression S-lli, the synchronizing cam I-Ill is driven by its coupling clutch 2 1! during one full revolution while the outer cam surface of the synchronizing cam 3-06 holds the key in the lifted position in which it actuates the contact springs of the recording switch 2-01 to their flexed position in which they establish the recording circuits; and to cause the biasing action oi the spring contacts of the recording switch 2--01 to their normal reproducing positions to return and to actuate the switch key 3--58 into its locking engagement with the cam depression 3 5! ot the synchronizing cam 3-05 at the end o! one revolution oi' 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 3-58, the contacts of the recording switch 2-ill remain in their normally biased unilexed position in which they establish the following record reproducing circuits:

From the ungrounded side of the serially connected transducer coils I-BI, l-BI in which the moving magnetic wave oi' the tape induces a signal voltage. through lead l-53, by way of the normally closed recording switch contacts 2-12 to the ampliiler input lead Z-IB for impressing on the ampliiier the signal voltage which is to be amplied, the circuits being completed through the grounded side oi the transducer coil I--BI and the grounded side of the amplifier.

The amplified output is delivered by the amplier through a circuit including ampliiier output lead Z-BI, the normally closed recording switch contact 2-16 to the reproducer R, the circuits being completed by the grounded side oi the ampliiler 2--0l and the grounded side of the reproducer R.

When the key 3-58 of the recording switch is actuated to unlock the synchronizing cam 3-05 and to ilex the contacts of the recording switch 2-01, its exed blades, which remain in the flexed recording position While the synchronizing cam 3-05 rotates, establish the following recording circuits:

A recording amplilier input circuit from the amplifier input lead 2--ill, through the flexed closed recording switch contacts 2-12, to a tap oi.' the volume control potentiometer 2-82, one side of which is connected through a contact at the phonograph jack 2-83, to ground. The other end of the volume control potentiometer 2-82 is connected by way of a jack 2-8I to a microphone M, indicated as a carbon microphone, to which its small exciting current may be supplied from a dry cell 2-85. As shown in Fig. 4, the dry cell 2-85 is normally disconnected from the operating circuits by the normally open relay contacts 2--86, which are closed only when the associated relay coil 2-81 is energized upon the actuation of the power supply switch 3--i0 to the position 3-l2 in which the amplifier as well as the tape driving motor l-II3 are energized.

In the arrangement shown, the amplifier input circuit from the carbon microphone M is completed through the upper contact of the microphone jack l-lll, the closed flexed recording switch contacts 2 8., closed relay contacts 2-88, to one terminal of dry cell I-IS, the other terminal of which is grounded. Ii a record is to be made from a phonograph pickup PU, its plug is inserted into the pickup jack 2-03, thereby exing its upper spring contact and connecting the phonograph pickup potentiometer 2-86 to the ampller input circuit instead oi the microphone potentiometer 2-82.

The recording ampliiler output is delivered through output lead 2-Bi to the closed ilexed recording switch contacts 2-16, output volume control potentiometer 2-05 and from the tap of a potentiometer by way of a serially connected condenser, through the closed flexed recording switch contacts 2-15, and transducer lead l--SI to the serially connected transducer coils l--SL i--Bl and therethrough to ground, the volume control potentiometer 2-ll5 permitting adjustment of the input to the transducer coils for optimum recording conditions. The additional contact spring of the closed flexed recording switch contacts 2-89 also completes additional D. C. supply circuits from dry cell 2-85 through lead I-13 by Way of current adjusting resistor [-56 to the serially connected transducer coils i-SI, l-BI, for impressing thereon the polarizing current required for recording, and through current adjusting resistor I16 to the obliterating coils I-ll ior impressing thereon the current required for obliterating the previous recording. The circuit from cell 2-85 is prepared by closure of the normally open contacts 2-86 of relay 2-81 when the supply switch 3-lil is actuated to its fully energizing position 3-I2.

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 I-Ill, by merely actuating the button oi' recording switch key 3-58 to r unlock the synchronizing cam 3-05 which is driven for the duration of one complete revolution by the friction coupling clutch 3-12, while its pointer knob 3-3I indicates on the dial 3-32 the progress of the recording, until at the end oi one complete revolution of the synchronizing cam 3-05, the switch key 3-58 is returned by the biasing action of the switch springs into locking engagement with the locking depression 3-50, 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 -llE. by means oi the pointer knob 3-3i, to a selected portion of the dial, for instance, to a point from the normal position, only the next following half of the tape length will be recorded while leaving on the preceding half of 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 3-3I and returning manually the synchronizing cam 3-05 to its locked position shown in Fig. 4.

Flexible control of the recording and the reproducing operations is thus secured. Upon the completion of each recording the entire recording on the tape is reproduced and the reproduc- 8 assaut tion oi the recording on the tape is continuously repeated until a new recording is made.

InFlgs toiiisillustratedapractical formo! a manually operated control arrangement of the type shown diagrammaticaily in Fig. t.

The control arrangement 3-.3 is part of the chassis of the amplifier I-Iii, which is mounted. in conjunction with the frame structure. on which the tape rollers l-II and the associated tape driving and guiding elements are mounted inside a housing I-II. The ampliner chassis has an exposed panel wall l-II and the control mechanism is mounted on the panel wall.

One of the tape rollers I-I2 drives through a suitable speed reduction mechanism. such as a iiexible shaft t-il and a worm gear I-ll mounted on a control shaft l-Il of the control mechanism which is revolvably mounted in an opening of the panel l-l I and a hole of a bracket l-Il secured to the panel I-II. The worm lear l-II of the exible shalt is suitably fixed. as by a pin, to the control shaft B-IO on which is slidingly keyed a friction coupling disc I-I'I which is pressed by a coupling spring into engagement with a control disc -I Il which is revolvably mounted on the control shaft S-ll, a layer of friction material covering one of the facing coupling surfaces.

The coupling disc B Il! is provided with a hollow shaft extension I l! which is revolvably mounted in the Journalilng opening of the panel I-I and serves as the bearing for the front end of the control shaft Q !I. Oil impregnated washers 9-2i1, 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 the projecting stub shaft end I Il of the control disc Q is secured a pointer I-2I which serves also as a grip tor rotating the control disc l-il relatively to the coupling disc I I'I. A dial 9 2! with a suitable scale is mounted on the panel behindthe pointer l-II. and the reduction gear drive connection between the control shaft Q !S and its driving roller i-H is so proportioned and arranged that when the control disc t-IO is coupled to the coupling disc i-il, the control disc i-ia 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 i-l! through the magnetic head I l. while the movement of the pointer 9 2! along the scale of the dial 8 2! indicates the progress oi' the travel of the complete length of the endless carrier.

The periphery of the control disc l-ll has a stop notch .-25 shaped to engage a control rod I Il slidably mounted in a bushing I Il extending through the panel wall I II so that when the control rod I-Il is in the position shown. the control disc Q will remain locked in place and will not be rotated by the coupling spring blades of the recording switch Z-ll pressing on the switch cam provided on the inward end of the control rod I-Il.

The control rod 9 2! may be arranged for actuation by a flexible push rod extension l-ll which is enelom in a flexible tube I-II having a coupling collar .-13 which is detachably coupled to the bushing 9 2?, so that by actuating push rod l-SI. the plunger attached to its inner end will actuate the control rod I Il to release the control disc I-II.

In Fig. 9 is shown a modified form of control mechanism of the type described in connection with Figs. to 8. A control shaft I Il journailed in the amplifier is driven by a worm gear S-ll in denite correlation to the travel of the disc I-I'i. 0n applying pressure to button l-IC of the control rod 8 2! and Pushing it lnwardly till its annular groove 0 2! releases the control disc Q !l. so that it is now free. the control disc is rotated by the worm-driven coupling disc I i 1. The slowly revolving periphery oi the control disc l-il engages the groove l-l of the control rod l-li and holds it in the inward dotted-line position until after one complete rev'olution of the control disc l-Il its notch I Il releases the control rod 8 2! to its normal outward locking position to which it is biased by the endless magnetic carrier I-ll. To the outer end of the control shaft l-II is secured a dial .-35 having a peripheral scale on which a pointer 0 3. mounted on the panel indicates the progressive travel o! the endless carrier I-II.

A control disc l-II which is revolvabiy Journalied to a control shalt I-II is frictlonally coupled to the shaft by a coupling disc I i'l which is slidingiy keyed on the shaft l-I 0 and is pressed against the control disc D-ll by its coupling spring, the several elements being seated on the shaft between oil impregnated felt washers 0 20 to secure quiet and smooth operation of all the moving parts.

The control disc l-IB may be locked in a stationary position and prevented from rotation by the locking engagement of its peripheral stop notch 0 2! with the lock arm 9 4! of a con trol lever 9-42 which is pivotally mounted on a pivot pin 9 4! and has a stop Q engaging one side of the control lever 8 42, so that by tilting the control lever 0 4! against the pressure oi an adjustably mounted biasing spring l-, the lock ann I-ll may be swung out of its locking engagement with the stop notch 8 26 of the control disc I i! to release it and permit it to be rotated by the coupling disc l-l! in correlation with the travel ci the carrier I-l! while the lock arm l-II is held in its unlocked Position by the periphery of the rotating control disc I-II. until after one complete revolution the biasing spring 9-45 returns the lock arm O-ll into its locking engagement with the control disc l-IO to stop its further rotation.' However. the articulated knee junction between the lock arm 0 4! and its control lever 8 42 makes it possible to return the control lever 8 4! to its normal position shown at any time during the rotation of the control disc l-II. while the lock arm 9 4! is held in its unlocked position by the periphery of the rotating control disc member I As in the arrangement oi Figs. 5 to 8, the control lever member 9-42 is utilized to control the operation or the multi-blade recording switch 2-01. To this end, the actuating cam l-ll of the recording switch 2-0'! with lts slidably mounted actuating rod O- is arranged to be operated by aV cam 9-4! mounted on an extension of the control lever member I II, 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 I I'! will move to the dotted-line position and actuate the switch cam I ll to flex the contact blades of the recording switch I-II to their recording positions. 'Ihe lever cam #-41 and the associated elements of the control mechanism are so arranged that the spring forces exerted thereon by the flexed blades of the reonitsreturnpothtobrlngitscaml-"onit grinforstartinganewrecordingonaselected rcturnpothhcyondltsunstsblccquilibrlnmpolnt 1 portion orthconslcm csrrlcrwhllc permitting of the endless carrier before its type shown in Pig. 8 with an endless carrier magentire length is recorded. so that upon the oomnetic recording reproducing apparatus in the pietion of each recording, the new recording as way described above in connection with Figs. l l5 we u the selectweiy retained previnug mordm4,thep0l'u0n0f|ihemveungrrlerwhlh ingmayberepmdudasmnymesdepattiroughthemgtiiileadisat atllltimes ,tx-ed,

in 011 the W0 when am In Fig. 10 is shown a modilled form of a con- Plil' 8nd the driving mm1' are enerizedthe trol arrangement lor selectively starting and entire wund Sequen recorded 0n the endless 2 stopping the recording operation on the endless carrier will be continuously repeated as 10118 u magnetic carrier in a way similar to the arrangeme control lever member is in n.01'- ment of Fig- 9. comprises a mol position To Stm o new fefdin im 8- with on indicating dial s-as and s friction coulected portion of the endless carrier. the recordplm n for selectively coupling a control um ins lever H2 is tried oom the Pme 2o ruso s-ls to the control shaft a-ls which ls 0f it! bim Spring s t0 release the @nml driven by a reduction gear mechanism O-Il so disc 23m 9 4. imm its engagement th "he that one revolution oi the dial corresponds to the lock arm s-II and to flex the contact blades of the recording switch l--IIT to the recording ttrahrvmellggftheemenagnremel of the wm carrier position. The new recording starts thus simulso The mal asked taneously with the releasing o! the control cam stamgmstguihn egemenno l-Il for one complete revolution. and the full its lock hole I-Sli with a lock pin 0-5i o! a lock length of the carrier 'u passing through the magnet l-ll arranged to release the control mm he "-4 s mme im "ne wm' also s-ls when thc magnet winding is energized plete voluti of the dm s u' u from a supply source indicated by plus and minus t Upon completion of a recording on the entire signs, upon the closure o! a normally open conlength ot endless carrier. as indicated by one mm The recording mmh 2 u with complete revolution of the dial .-45, the lock am u man has been riding um the its block of normally unilexed spring contact l earn l rrmfbtogfng spun; tutin'gicg recording position by a magnet l-ll when its slot l--IB of the control cam l-, thereby stopbhhe clown o! an ac' ping its rotation, while at the same time the lever c c s norman open con m H2 and the switch cam n are returned trol-cam actuated contacto:- s-ll and the norto their normal position shown. thereby releas- 45 many @en nml'lever mm @amr ing the contact blades of the recording switch params will thereupon repeat the newly recorded locked POSltiOn Shown. its @DMW ,-55 iS 1'8- sound sequence and continue to repeat it until ma w s ope am mmh Pmo 5nd it is 1th 50 nexed to the closed position when the control es .tir the motor is stopped or a new recording I. s rel l and rotated by the coupling A new recording may be connned to a selected um nportion of the endless carrier as indicated on the The 0th Wilmot 9 is maimed t0 be me of the rotating dial Q by swinging the closed by a cam s-BB of a control level s-Sil tilted control lever a-az with its lover com s -u as Pivotllv mounted 0n o bracket so that when the from the dotted nne recording position to the lever -5. is tilted t0 the dotted-line position normal run-unc position, thereby releasing thc H y its cm 9 5' Closes the mm Hl sence sp1-lng blades of thc recording switch z-sl the com 9-58 being retained in the contaotor to their normal reproducing position, while the closing position by the Spring Pressure 0f the look arm u is stm riding along the periphery w contactor blade. A handle s-Gi pivotaliy joined oi the control disc until it is released into the t0 the @am level' H9 and biased by 8 11513- lock notch of the control com s-ls et the end tively strong spring ssainst s stop s-N ci the of a complete revolution. The return of the con- 0ntrl lever l-59 1S S0 arrnged that in swingtrol lever l-l! to its normal position before ins handle B-II to bring the 0Dtl`0l lever 9 5! the control cam 9-18 completes a full revoluo5 to the dotted-line position. the handle Q-BI is tion enables instantaneous return of the recordtilted until its projecting knob closes the coning switch 2-01 from its recording position to taccor -Sl and energizes the lock relay B--S its normal reproducing position so as to corinne to release the control disc D-IO. 'I'he actions the new recording only to a portion of the endbring about the closure oi the two contactors less carrier as selected by the scale of the re- 'I0 l-IL l-Sl and the energization of the switch volving dial 9-21 This arrangement enables magnet l-l which activites the recOrdinS the student to compare his own new recording switch 2-II1 to the recording position. As soon on a selected portion of the endless carrier with as the handle 0 6! is released. its biasing spring another specimen recording, for instance, of a returns it against the stop of the control lever phrase recorded by a teacher. or from a phono- 75 I-Sl, thereby cle-energizing the lock magnet l-l! while the lock pin rides on the surface oi the revolving control disc l-il.

The control rangement shown in Fig. 10 will operate in combination with an endless msgin s way similar to the contro oiFlg.9.Inthenormalre producing position. the control disc l-II is held locked by the lock pin o! the look magnet I l2; the control disc contacter l-ll is released to its open position by the control disc notch G ll: the switch magnet 2-10 is kept ie-energized by the open contactors l-Il. Ht; and the blades of the recording switch I-I are in the unilexed normal reproducing position.

llo start a new recording on s selected portion or the endleu carrier as indicated on the scale of revolving dici i-Il. the lever handle S-BI is tilted to close the contacter I-ll and bring the control lever I-Il with its cam l-II to the thereby locking the concam D-ll in the closed p0- sition while the released control disc l-ll closes its contactor I-II. As s result. the switch magnet 2 1! is instantaneously energized to sctuate the recording switch I-I'I to the recording position and start the ot the endless carrier I-ill passing through the magnetic head I-I will be recorded during one complete revolution of the dial I-Il.

Upon the completion of the new recording cn the entire length of the endless carrier, the lock pin I-ll locks the control disc l-II mal position in which A new recording may be conilned only to a selected fraction of the endless carrier as indicated on the scale o! the revolving dial I- by tilting the control lever .-50 to its normal position shown before the control disc l-II has completed a full revolution, thereby ie-energizing the Il ond l-l. The control disc F1! has a. shaft extension 0 1! which is journalled in a hollow shaft extension I-ll or the second control disc 0 12. The two control discs l-H and l-l2 are arranged to be adjustably coupled to each other by a seml-circular coupling plate the coupling disc I-l! and pressed by s coupling spring into coupling engagement with the semi-circular coupling plate I-ll.

In the form shown in Fig. i3. the coupling connection is eilected by the engagement oi' a coupling pin proiection I-II or the coupling plate l-ll with one of s .-15. l-'I by 811994118 the circular l-ll. I-ll. respecti angul placement o! the coupling pistes l-ll, l-ll shown by their colored segments indicated the angular displacement oi the control notches l-ti, .-82 ci' the two control discs.

As shown in Pig. 1l, the

ilexed recordposition by s switch magnet I-ll which is energized from a supply source. indicated by plus and minus signs. through on actuating circuit which is controlled by the control disc contactors starting button .-81 in conauxiliary relny I-Il having assai lesscarriertotheredsegmentn of the dial plates l`|l, l-1l. II. on the other hand, the selector switch l-II is in the other poeitlmindicatedbythearroww.anewre cording started by the closure oi the button switch I-ll will conilne the new recording to the portion of the endless carrier corresponding to the white segment W ot the dial plates B-li, l-ll. The simple angular adjustment oi' the coupling connection between the two control discs l-H, 9-12, as indicated by the colored dial plate ents, in conjunction with the simple actuation of the selector switch 9-90, make it thus easy to control the selective recording on selected portions of the carrier.

Thus,ifanewrecordingistobemadeonthe portion of the endless carrier indicated by the red segment oi' the dial plates B-l, 8 18, the selector switch l-B is placed in the position indicated by the arrow R as shown in Fig. ll. Thereupon. each time a new recording confined to this selected portion of the endless carrier is to be made, the user has merely to close starting switch 9-81 for a moment. This completes an energizing circuit for the starting relay 9-88 which is connected to the minus terminal, from the plus terminal of the relay supply, through the closed starting switch 9-81. and the blade 9-88 of the recording switch 2-01. The energization o! the starting relay 9-88 completes a locking circuit at its inner contracts. and it remains locked until its locking circuit is opened at the contact blade l-SI of the recording switch 2--ill when the recording switch relay Z-Ill is energized. The closed starting relay contacts l-BI prepare an actuating circuit for the recording switch magnet 2-lll leading from the minus supply terminal, through the winding of magnet 2-10, by way of the closed selector switch contacts 9-94 to the open contacts oi the control disc switch B-ll, and therefrom through the closed selector blade contacts 9-93 to the plus supply terminal, the circuit being completed when the notch of the revolving control disc 8-82 releases its contactor 9-84 from its flexed position and through the energization of the recording switch magnet 2-10 actuates the recording switch to start the recording operation.

The energization of the recording switch magnet 2-10 effects also the closure of its lock-in contacts --Ii which complete its lock-in circuit leading from the positive supply terminal through the closed selector contacts B-l, the closed contacts of the control disc contacter 9-83, the closed selector switch contacts 9-92, the closed relay lock-in contacts 9-85 and the winding of the recording switch magnet 2-1 to the negative supply terminal. At the same time, the energization of the recording switch magnet 2 1!) opens at its contacts 9-86 the lock-in circuit of the starting relay 9-83 and thereby returns its contacts to their normal open positions.

The recording operation, which was thus start ed when the control disc switch S-ll was momentarily released from its flexed position into notch 9 8! of the revolving control disc cam 9-12, will now continue until, as indicated by the motion of the red dial segment past the pointer 9-36, the notch 9-8I of the revolving m control disc S-li releases its associated contac tor from its flexed position, thereby breaking at its normally closed contacts the lock-in circuit of the recording switch magnet 2-10, and by the resulting de-energization of the recording switch magnet I-ll returns the recording switch I-ill toits normal reproducing position.

The user will then hear the reproduction of the retained part of the previous recording, as

I indicated by the white part W of the dial. i'ollowed by the reproduction oi his new recording, asindicatedbythered'partoi' thescale. He may make new recordings and hear the retained recordingandhisnewrecordlngsasmanytimes 1 as he desires by merely pressing the button of the starting switch l-l'l each time he desires to make a new recording.

By moving the selector switch l-il to the opposite position. in the direction of the arrow l W, any new recording started by the momentary closure oi the starting switch I-Il will be conilned to the length oi' the endless carrier corresponding to the white segment W-W o! 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 0-81 is momentarily closed. the apparatus will be automatically switched over for recording when the iront edge of the white segment area oi' the revolving dial reaches so the pointer S-Il and the recording period will be automatically stopped when the rear edge of the white segment reaches the pointer l-ll, whereupon both recorded sequences of the endless carrier will be continuously repeated until a new recording is to be made on the portion oi' the endless carrier corresponding to the white segment oi the revolving dial.

This arrangement makes it thus possible to o 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 oi' the endless carrier for repeatedly making his own recordings until he is satisiled 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 o! 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 h e desires on the portion of the endless 56 carrier reserved for him until he has completed his training.

Although the friction coupling connection between the control shaft l--IB and the control disc l-IB is not required for the operation of .o 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-1I, l--l relatively to the coupling plate l-II 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 of the invention which makes it possible to continuously reproduce only a selected sound sequence recorded on a selected portion of the total length of the carrier without repeating the sound recorded on the remainder oi the endless carrier. Such arrangement is desirable, for instance, i! the endless carrier has a length sui'- 'll cient for recording a long sound sequence and A lished for reproducing the user desires to `play back only a selected short sound sequence, such as a single sentence.

An endless carrier I-III, which is driven at a uniform speed along a plurality of guide rollers I-M has, in addition to a main magnetic head i-I with obliterating magnets i--ll and transducer magnets L M. several additional sets of ucer magnets i-Il-A, I-ll-B, i-cB-C, located at diiferent 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 s-it which drives through a friction coupling disc l-il a control disc cam I-II so that when the control disc l-Il 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 O-Ii, .-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 oi' the control disc Q-il, or to stop the recording operation by actuating the lever handle l-I2 to release the switch 2-01 from its recording position while the lock member of the control lever l-li is still riding on the periphery oi' the revolving control disc s-il in the way explained in connection with Fig. control arrangement of Fig. l1 may be used for controlling the recording operation.

The control shaft S-il is arranged to revolve a pair of contact wiper arms il-Ii, Il-II along insulatingly mounted segments of the split contact rings lil-il, Il-H oi' a rotary switching device Il-Il. The switching device ill-II may be angularlv revolved, as by means of a handle or a friction roller l-ii operated through a flexible shaft so as to permit adjustment of the phase relation of the contact segments II-II. ill-i4 with respect to the moving endless carrier l-II.

A switch Ill-ll having a blade movable between the position shown, in which it completes a circuit connection to the lead i-BI connected to the transformer windings of the magnetic head i-I, and two other positions, in which it completes circuit connections to the switch wipers ll-I l and Ill-i2, respectively, is associated with the rotary switching device lill in performing the control operations. An ampliier l--ill and a recording switch 2-tl are arranged to estab lish 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 ilex lts blades from 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.

In this position. the following circuits are estabfrom the transducer wind- 9. If desired, the fully automatic Accordingly, the previously made recording from the entire length of the endless tape I-lli will be reproduced. To make a recording. the recording control lever .-42 is actuated to release the cam I-II, thereby actuating the blades of the recording switch 2ill to the nexed recording position in which they are maintained for one full rotation of the control disc I-It.

In this flexed recording position, the flexed blades of the recording switch 2-01 break the reproducing circuit connections and establish the circuit connections: A repotentiometer lll-il, the closed flexed contacts ofthe recording switch blade 2-12, to the input lead 2il of the amplii'ler 2-Ilil. The recordlng output is delivered through ampliner recordlng output lead 2 4. the closed flexed recording switch blades 2 1! and lead L to the serially connected transducer windings l-ii, I-tl to ground.

At the same time, there is also supplied a D. C. obliteratlng current from the positive supply lead I-li extending from the D. C. filter network oi the amplifier. through the flexed closed contacts of the recording switch blade 2-14, to the lead I-ll the obliteratlng coils i-'ll of head i-B, the flexed recording switch blade 2-14 also completing D. C. supply lead ing resistor I-Il,

the magnetic head i-l.

The provision of the rotary switching device II-II. the wipers of which are revolved in synchronism with the movement of the tape, and the associated selector switch III-I8, makes it possible to selectively confine the play-back from the recording so made on the tape to only a portion of the tape. Thus. by moving the selector switch iI-Il to the position in which it completes a circuit from the recording switch blade 2 1! to the rotary wiper il-i.i, the revolving wiper Il-Ii will, during each full revolution, successively engage the four other transducing winding to the input side of the ampliiier during each revolution of the wiper. As a result, the rotating wiper IU-I i will, after each quarter of a revolution of the control shaft.

establish circuit connections [or playing back the same sequence recorded on a quarter ol the length of the endless carrier, without playing back the record made on the remaining threequarters o! the endless carrier.

In a simiiarway, when the arm of the selector switch lli-ll is moved to the pomtion in which it completes a circuit to the selector switch wiper ill-l1, the latter will. in the course oi each revolutionestablish successive engagement with the contact ts IO-II connected to the transducer input I-Sl and I-iI-B for successively playing back the recording on one selected half o! the endless carrier, without playingbacktherecordontheotherbaliofthe carrier.

This t enables the user tostart the reproduction oi' a sound sequence on a selected portion of the moving endless carrier as indicated on the dial by turning the switching device IU-II either by the handle or by the remote control drive l--IS to the desired angular position. After the switching device iI--Il has been turned to the right position, the selected sound sequence will be continuously reproduced without reproducing the other parts of the recorded sound.

By providing a selector switch III-i6 with a larger number of selector contacts and a corresponding wiper switch lll-II, the reproducing process may be conilned 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. l shows how the recording control mechanism o1' Pig. 14 is applied to such apparatim. A control cam S-IB is driven through a friction coupling drive at a speed correlated to the travel oi' the endless carriers, and an articulated control lever l-Ii, 9-42 associated with the control cam l-II controls the operation of the recording switch 2-01.

A key-operated multi-blade selector switch lilmay be actuated by a cam movable from the neutral position shown in the drawings for selectively conning the recording or reproducing operations to the endless carrier i-UI-A or to the positions indicated by the arrows B, C tor recording and reproducing sound on the endless carriers I-Ii-B or i-UI-C.

When the selector switch Iii-2li is in its position shown in the drawings, the i'ollowing circuit connections for reproducing and recording connections by means o! the sound carrier I-Bi-A are established: The obliterating winding I-li of the magnetic head l-l-A is connected through selector switch blades it-lli and lil- 23 to a contact of the recording switch blade 2--14 through which a magnetizing current is supplied during a recording operation: the transducer winding i-Si of the magnetic head l-S-A is connected through selector blades lil-2l and il-IZ to the center contact of the recording switch blade I-ll through which the transducer winding is connected either to the amplifier input `winding I-I ior reproducing or to the output transformer winding 2-52 for recording, while the recording switch blade 2--14 supplies through resistor l-BB the depolarizing current to the transducer windings I--SL Accordingly, as long as the selector switch ill-2l is in its neutral position, the transducer and obliterating coils of the magnetic head I-S-A will operate in conjunction with the amplifier I-II under the associated recording control arrangement to selectively reproduce or record sound on the tape as in the arrangements oi Fig. l or 9.

When the selector switch lli-20 is actuated to the position indicated by the arrow B, its licxed blades break at the contacts lb-ZI, in-22, lli-23 the recording and reproducing connections to the magnetic head l-S-A of the endless carrier l-iii-A, and establishes the following reproducing and recording connections to the magnetic head l-S--B of the carrier I-IlI-B: Its obliterating coil l--1I is connected over the closed lock-out switch ill-3i through the flexed selector blaue ll-u to the outer contact oi the recording switch blade 2-14. through which a magnetizing current is supplied during the recording operation; and its transducer coil l-5I is connected through the flexed selector blade III-22 to the recording switch blade 2`I5, through which the connection is completed to the input lead l--ii of the amplifier for reproducing sound from tape I-I-B. or in the ilexed recording switch position, through the closed lock-out bypass contacts I0-32, by way oi the unexed selector contacts III-29, to the ampiiiier output lead 2-83 for recording sound on the tape l-Ill-B.

When the selector switch i-li is iiexed to the position indicated by arrow C, it breaks at the flexed blades Il-lll lli-29 the recording and reproducing connections to the magnetic head i-S-A of the endless carrier l-iii-A, and establishes the following reproducing and recording connections for the magnetic head i-S-C of the endless carrier I-III-C. Its obliterating coil i-1I is connected over the closed lock-out contacts io-, through the flexed selector blade lll-25 to the recording switch blade 2'I4, through which a magnetizing current is supplied to the obliterating coil during the recording operation; and its transducer coil I--Si is connected through the flexed selector blade III-24 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 iiexed recording switch position, by way oi the uniexed selector contact Il-ZI and the lock-out bypass contacts Iii- 3l to the amplifier output lead 2--68 for recording sound on the magnetic tape l-oI-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 ci the selector switch III-2li, either one o! the several magnetic carriers may be connected for recording and reproducing sound in conjunction with a common amplifier 2 0! under the utilization oi one of the various recording control arrangements described hereinabove.

The two sets oi lock-out contacts lil-3i, lll-32 and Ill-4l, Il--ll are associated with the circuits to the tapes I-Oi-B and I-iiI-C, respectively, and are so arranged that the opening o1 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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