US2456592A - Commercial phonograph signal device - Google Patents

Commercial phonograph signal device Download PDF

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US2456592A
US2456592A US700689A US70068946A US2456592A US 2456592 A US2456592 A US 2456592A US 700689 A US700689 A US 700689A US 70068946 A US70068946 A US 70068946A US 2456592 A US2456592 A US 2456592A
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amplifier
feed
circuit
signal
recording
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Lucius P Petruschell
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Dictaphone Corp
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Dictaphone Corp
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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B25/00Apparatus characterised by the shape of record carrier employed but not specific to the method of recording or reproducing, e.g. dictating apparatus; Combinations of such apparatus
    • G11B25/02Apparatus characterised by the shape of record carrier employed but not specific to the method of recording or reproducing, e.g. dictating apparatus; Combinations of such apparatus using cylindrical record carriers

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  • Sound recording apparatus is frequently' used for recording merchandiseinventories, speeches and conversations.
  • Various-devices have been employed to-warnsuch an operator of unsuitable recording conditions, often by means of a buzzer or other audible signal generator mounted on the recordingequipment.
  • the distance and obstructions between the operator and recording apparatus are increased, such .a system is impractical for many applications.
  • an object of this invention is to provide a simple and inexpensive warning system whereby an audible signal is produced'near a remotely located operator of sound recording apparatus in response to a predetermined condition existing at the recorder.
  • a further object is to provide this warning signal, without requiring extra signalling vap-- paratus at the remote location or the use of additional connections between the microphone and the recording apparatus, by operating the microphone ordinarily used ,for recording reversibly as a loud-speaker and utilizing the already present microphone cable .for transmission of the warningsignal.
  • Still another object of thisinvention is to obviate the need for a special audio signal generator by utilizing the amplifierin the sound recording apparatus to generate the warning signal.
  • a crystal typemicrophone which may be remotely located; is connected to a conventional type-speech amplifier that amplifies the signal prior to-recording.
  • a teed-back circuit is provided between-the output and input-circuits of the'am-plifi'er, which, when connected, causes the amplifier togenerate an audio signal.
  • This fee-whack network is adaptedi'to be connected whenevena-nyone 'of the predetermined conditions. at the-recorder would---prevent proper recordingr
  • Withlthe feed-"back networkconnected and the amplifier operating as an audio signal generator Withlthe feed-"back networkconnected and the amplifier operating as an audio signal generator, :the audio signal voltage appearsacross the input network of the amplifier and consequently across the terminals-of the microphone, .causing; it zto act reversible as a loudspeaker. and .thus provide. the :desired warning signal.
  • a crystal'type' microphone-:2 is connected to the input circuit ofcan' audio amplifier, generally indicated at 4, byleads '6 .'andii8;-.which are :of sufiicient length to enable.thewmicrophoneto be remotely operated.
  • .A-push-buttonswitch-9 is associated with the microphone to permit remote: control of the recording mechanism.
  • the :signal .from the microphone 1-2 which isv applied to control grid l0, is amplifi ed by tube [1 three stagesoi 'm- Dlification, 'generallyindicated :at, 1:2,, :and the power amplifier tube :14.
  • the output :circuitzof this-power amplifier stage iszcoupled 'through :an audio transformer A16 to ,a recordingelemeut t8;
  • The-element: i8 records the audio signals .on .a-
  • cylindrical wax record- 210 which is arotated about; itsalongitudinalraxls byia-motorzzz as' the recording element 18 is moved axially by a threaded rod 24.
  • the position of the stylus on the recording element I8 is controlled by a lever 26 and may occupy either of two positions, one in which the stylus is in contact with the surface of the record 20 for recording and a second position in which the stylus is removed from the record to permit the recording element to be moved axially and records to be removed or replaced.
  • the feed-back circuit of the amplifier includes a condenser 21, a variable resistance 28 and a relay, generally indicated at 30, so arranged that when a relay actuating coil 32 is energized, thus closing relay contacts 34, energy from the output circuit of the amplifier will be applied to grid III in the amplifier input circuit.
  • the amount of energy thus fed back is sufiicient to cause the amplifier to oscillate at an audio frequency rate thus developing an audio signal across a grid resistance 3B and consequently applying this voltage through the connecting cable to the microphone 2 causing it to act reversibly as a loud-speaker and produce an audible warning signal.
  • the frequency and volume of this signal are determined by the values of condenser 21, and resistance 28, condenser 21 being predetermined and fixed and resistance 28 being adjustable to permit control of the signal volume.
  • the amplifier may include an automatic volume control circuit to limit the amplitude of the oscillation to a safe value or this result may be accomplished by judicious choice of values for condenser 26 and resistance 28.
  • relay coil 32 When relay coil 32 is energized, thus closing contacts 34 and converting the amplifier into an audio generator, another set of contact points 38 is opened disconnecting the recording element l8 from the amplifier and thereby preventing the audio warning signal from being recorded.
  • the relay coil 32 is, in the example shown, responsive to three conditions which may exist at the recorder.
  • a centrifugal type switch generally indicated at 40, is associated with the record driving mechanism to indicate whether the recrd is rotating.
  • a second switch 42 is associated with the stylus control lever arm 26 and so constructed that when the arm has been moved to the position which lifts the recording stylus from the record surface the contact points of switch 42 are closed, but are open-circuited when the lever arm 26 is in position for recording.
  • a third switch 44 positioned near the right hand end of the record 20, is designed to be actuated by the recording element H! as it approaches the end of threaded rod 24, thus providing an indication when the recording surface has been substantially used up.
  • the switches 40, 42 and 44 are connected in parallel with each other and in series with relay actuating coil 32 and the commercial supply lines.
  • the coil 32 is thus energized whenever one or more of the switches 40, 42 and 44 are in a closed position, that is to say, when the record is not rotating, the recording surface has been substantially used up or the stylus of the recording element I8 is not in the recording position.
  • the relay 30, thus actuated, connects the amplifier feed-back circuit, thus warning the remotely located operator that the sound will not be properly recorded and simultaneously opening the amplifier output circuit to prevent the warning signal from being recorded on the wax record.
  • the warning signal responsive to any desired predetermined condition existing at the recorder, is thus produced at the physical location of the operator by a simple and inexpensive circuit arrangement that eliminates the need for a separate audio signal generator, additional cables between the microphone and amplifier locations or extra indicating mechanisms at the remote position.
  • a signal arangement for indicating the existence of a predetermined condition of operation of the sound recording apparatus comprising, in combination, are generative feed-back connection from an output circuit to an input circuit of said amplifier to produce an audio-frequency feed-back, switching means in said feed-back connection operative upon the occurrence of said predetermined condition of said apparatus to complete said feed-back circuit, and a translating means connected to the input circuit of said amplifier for producing an audible signal upon completion of said feed-back circuit.
  • a signal arrangement for indicating the existence of a predetermined condition of operation in the sound record apparatus comprising, in combination, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier to produce an audioirequency signal, means to control thefrequency of said audio-frequency signal, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to the input circuit of said am plifier for producing an audible signal upon completion of said feed-back circuit.
  • a signal arrangement for indicating the existence of some predetermined condition of operation in a sound recording apparatus comprising, in combination, an amplifier, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier to produce an audio-frequency, means to control the magnitude of said audio-frequency, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to the input circuit of said amplifier for producing an audible signal upon operation of said feed-back circuit.
  • a signal arrangement for indicating the existence of some predetermined condition of ane operation in ,said, recording apparatus comprising, in combination, a regenerative feed-back connectionfrom the output circuitto the input cir-- cuitoftarportion oft-said amplifierfito produce an audiosignal, means in saidlfeed i-back circuit-for controlling.- the. frequency of" said audio signal, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and reversible translating means connected to said amplifier for producing an audible signal upon operation of said feed-back circuit.
  • a signal arrangement for indicating the existence of some predetermined condition of operation in the apparatus comprising, in combination, an amplifier, a regenerative feed-back connection from an output circuit to an input circuit of said amplifier to produce an audio-frequency signal, means in said feed-back circuit for controlling the magnitude of said signal, means in said feed-back circuit to control the frequency of said signal, switching means in said feed-back connection responsive upon the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to said amplifier for producing an audible signal upon completion of said feed-back circuit.
  • a signal arrangement for indicating the existence of a predetermined condition of operation of said machine comprising, in combination, an amplifier, regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier, switching means responsive to the occurrence of said predetermined condition to complete said feed-back circuit and cause said amplifier to generate an audio-frequency signal, and a reverse acting translating device connected to the input of said amplifier to act as a microphone during recording and as a loud-speaker upon the operation of said switching means whereby an audible signal is produced at any remote location near the operator to warn of the existence of said predetermined condition of operation of the recording machine.
  • a signal arrangement for indicating the existence of a predetermined condition comprising, in combination, a sound amplifier, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier, switching means responsive to the occurrence of said predetermined condition to complete said feed-back circuit and cause said amplifier to generate an audio-frequency signal, and a piezoelectric crystal translating device connected to the input of said amplifier to act as a microphone and adapted to produce an audible signal on occurrence of said predetermined condition.
  • a signal arrangement for indicating the existence of a predetermined condition of operation of said recording apparatus comprising, in combination, a; vacuum-tube amplifier, a sound recording element coupled to the output of said amplifier, a recording surface adapted to be engraved by said element, a regenerative feed-back circuit from the output circuit to the input circuit of a portion of said amplifier, switching means in said feedback circuit responsive to the lateral position of said recording means on said recording surface to complete said feed-back circuit, and reversible translating means connected to said amplifier ands-adapted ton pro'duceuan audible") signal up on operations of.:sa1d.ifeed-back circuit,
  • aisignalar rangementlaforlindicatingstlie existence of a predetermined condition of operation of said recording machine comprising; incombination, a vacuum-tube. amplifier, ,a recordingelement, a record adapted to be engraved by saidielment a record driving mechanism for rotating said record, a regenerative feed-back circuit from the output circuit to the input circuit of a portion of said amplifier, switching means in said feed-back circuit responsive to rotation of said record driving mechanism to complete said feed-back circuit, reversible translating means connected to said amplifier and adapted to produce an audible signal upon completion of said feed-back circuit.
  • a signal arrangement for indicating the existence of a predetermined condition of operation of said recording machine comprising, in combination, a vacuum-tube amplifier, a sound recording element coupled to the output of said amplifier, a record adapted to be engraved by said recording element, control means for manually determining the position of said recording element relative to said recording surface, a positive feed-back circuit connected between an output and an input circuit of said amplifier switch means in said feedback circuit responsive to the position of said recording element relative to said surface, and reversible translating means connected to said amplifier and adapted to produce an audible signal upon completion of said feed-back circuit.
  • a remotely operated dictating apparatus comprising, in combination, a sound amplifier, a crystal microphone connected to the input terminals of said amplifier, a record, a recording element connected to the output of said amplifier.
  • a driving mechanism for rotating said record, a regenerative feed-back circuit coupled between output and input circuits of said amplifier to produce an audio-frequency feedback, means in said feed-back circuit for controlling the fre-, quency of said audio feedback, means in said feedback circuit for controlling the magnitude of said feedback, and switch means in said feed-back circuit responsive to a predetermined condition in said recording apparatus to complete said feedback circuit causing said amplifier to oscillate at an audio-frequency rate, thereby causing said microphone to emit an audible warning signal upon occurrence of said predetermined condition.
  • a remotely operated dictating apparatus comprising, in combination, a sound amplifier having input and output vacuum tubes, a resistor connected between the grid and cathode circuit of said input tube and a crystal microphone connected in parallel therewith, a record, a recordin element connected to the output of said amplifier and adapted to record sound signals on said record, a driving mechanism for rotating said record, a regenerative feed-back circuit comprising a capacitor connected in series with a variable resistor between the plate of said output tube of said amplifier and the grid of said input tube to produce an audio-frequency feedback, a relay actuating coil responsive to the existence of a predetermined condition of operation in said recording apparatus, and relay contacts operated by said relay actuating coil to complete said feedback circuit causing said amplifier to oscillate at an audio-frequency rate, whereby said microphone is caused to produce an audible warning 7 8 signal at any remote location near the operator to warn of the existence of said predetermined UNITED STATES PATENTS condition of operation.

Description

Dec. 14, 1948. P. PETRUSCHELL COMMERCIAL PHONOGRAPH SIGNAL DEVICE Filed Oct. 2, 1946 INVENTOR Lucius Z Pelrusc/zell I I I Patented Dec. 14, 1948 GOMMERCIALPHONOGRAPH SIGNAL V ."DEVICE Lucius P. :Petruschell, :Mount Dora, -.Fla., assignor to Dictaphone florporation, New "York, N. 'Y.,, a corporation of New York Application ctober'2, 1946,Serial'No. 700 689 .1-2-0 laims., (01. 119-1004) This invention relates to sound recordingapparatus of the type using electronic amplification and more particularly to remote operation indicating mechanisms for such sound' recording apparatus. a
Sound recording apparatus is frequently' used for recording merchandiseinventories, speeches and conversations. In these and other applications it is often desirable to locate the microphone at considerable-distance from the recording apparatus and under suchcircumstances it becomes particularly important that an operator located at the remote position be cognizant of any condition existing at the soundrecording apparatus that would interfere with proper recording of the audible signals. Various-devices have been employed to-warnsuch an operator of unsuitable recording conditions, often by means of a buzzer or other audible signal generator mounted on the recordingequipment. However, because of the higher volume required .as the distance and obstructions between the operator and recording apparatus are increased, such .a system is impractical for many applications.
Earlier remotesignalling systems, such as thatv described in U. S. Patent No.. 2,284,678,:require a special remote indicatingmechanism and the use of additional connecting cables between the microphone location and the sound recording equipment. The extra cableand indicator unit are not only expensive but particularly cumbersome in applications where it is desirable for the operator to frequently change physical location, as for example, when making a .merchandise inventory.
Accordingly, an object of this invention .is to provide a simple and inexpensive warning system whereby an audible signal is produced'near a remotely located operator of sound recording apparatus in response to a predetermined condition existing at the recorder.
A further object is to provide this warning signal, without requiring extra signalling vap-- paratus at the remote location or the use of additional connections between the microphone and the recording apparatus, by operating the microphone ordinarily used ,for recording reversibly as a loud-speaker and utilizing the already present microphone cable .for transmission of the warningsignal.
Still another object of thisinvention is to obviate the need for a special audio signal generator by utilizing the amplifierin the sound recording apparatus to generate the warning signal.
, sents more or less diagrammatically a sound recording apparatus embodying the principles of this invention.
A crystal typemicrophone, which may be remotely located; is connected to a conventional type-speech amplifier that amplifies the signal prior to-recording. A teed-back circuit is provided between-the output and input-circuits of the'am-plifi'er, which, when connected, causes the amplifier togenerate an audio signal. This fee-whack network is adaptedi'to be connected whenevena-nyone 'of the predetermined conditions. at the-recorder would---prevent proper recordingr Withlthe feed-"back networkconnected and the amplifier operating as an audio signal generator, :the audio signal voltage appearsacross the input network of the amplifier and consequently across the terminals-of the microphone, .causing; it zto act reversible as a loudspeaker. and .thus provide. the :desired warning signal.
Referring now to the drawing, a crystal'type' microphone-:2 is connected to the input circuit ofcan' audio amplifier, generally indicated at 4, byleads '6 .'andii8;-.which are :of sufiicient length to enable.thewmicrophoneto be remotely operated. .A-push-buttonswitch-9 is associated with the microphone to permit remote: control of the recording mechanism. The :signal .from the microphone 1-2, which isv applied to control grid l0, is amplifi ed by tube [1 three stagesoi 'm- Dlification, 'generallyindicated :at, 1:2,, :and the power amplifier tube :14. The output :circuitzof this-power amplifier stage iszcoupled 'through :an audio transformer A16 to ,a recordingelemeut t8;
. Operating, potentials ,iior'zthe amplifier are obtained from a conventional: type rectifier-filter power supply, generally indicated at 2.0;
The-element: i8 records the audio signals .on .a-
cylindrical wax record- 210 which is arotated about; itsalongitudinalraxls byia-motorzzz as' the recording element 18 is moved axially by a threaded rod 24. The position of the stylus on the recording element I8 is controlled by a lever 26 and may occupy either of two positions, one in which the stylus is in contact with the surface of the record 20 for recording and a second position in which the stylus is removed from the record to permit the recording element to be moved axially and records to be removed or replaced.
The feed-back circuit of the amplifier includes a condenser 21, a variable resistance 28 and a relay, generally indicated at 30, so arranged that when a relay actuating coil 32 is energized, thus closing relay contacts 34, energy from the output circuit of the amplifier will be applied to grid III in the amplifier input circuit. The amount of energy thus fed back is sufiicient to cause the amplifier to oscillate at an audio frequency rate thus developing an audio signal across a grid resistance 3B and consequently applying this voltage through the connecting cable to the microphone 2 causing it to act reversibly as a loud-speaker and produce an audible warning signal. The frequency and volume of this signal are determined by the values of condenser 21, and resistance 28, condenser 21 being predetermined and fixed and resistance 28 being adjustable to permit control of the signal volume. The amplifier may include an automatic volume control circuit to limit the amplitude of the oscillation to a safe value or this result may be accomplished by judicious choice of values for condenser 26 and resistance 28.
When relay coil 32 is energized, thus closing contacts 34 and converting the amplifier into an audio generator, another set of contact points 38 is opened disconnecting the recording element l8 from the amplifier and thereby preventing the audio warning signal from being recorded.
The relay coil 32 is, in the example shown, responsive to three conditions which may exist at the recorder. A centrifugal type switch, generally indicated at 40, is associated with the record driving mechanism to indicate whether the recrd is rotating. A second switch 42 is associated with the stylus control lever arm 26 and so constructed that when the arm has been moved to the position which lifts the recording stylus from the record surface the contact points of switch 42 are closed, but are open-circuited when the lever arm 26 is in position for recording. A third switch 44, positioned near the right hand end of the record 20, is designed to be actuated by the recording element H! as it approaches the end of threaded rod 24, thus providing an indication when the recording surface has been substantially used up.
The switches 40, 42 and 44 are connected in parallel with each other and in series with relay actuating coil 32 and the commercial supply lines. The coil 32 is thus energized whenever one or more of the switches 40, 42 and 44 are in a closed position, that is to say, when the record is not rotating, the recording surface has been substantially used up or the stylus of the recording element I8 is not in the recording position. The relay 30, thus actuated, connects the amplifier feed-back circuit, thus warning the remotely located operator that the sound will not be properly recorded and simultaneously opening the amplifier output circuit to prevent the warning signal from being recorded on the wax record.
The warning signal, responsive to any desired predetermined condition existing at the recorder, is thus produced at the physical location of the operator by a simple and inexpensive circuit arrangement that eliminates the need for a separate audio signal generator, additional cables between the microphone and amplifier locations or extra indicating mechanisms at the remote position.
It Will be apparent that the manner of coupling the feed-back circuit to the output of the amplifier will depend upon the total number of amplifier stages and must be so coupled that the phase of the energy fed back is such as to produce self sustained oscillation. Obviously any one of the wide variety of feed-back circuits may be employed and it is not intended to limit the scope of this invention to the particular circuit described above.
It is further to be understood that although a crystal type microphone has been described in the above embodiment of the invention, a dynamic or other reversible microphone could be substituted therefor without departing from the scope of this invention.
As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.
I claim:
1. In a sound recording machine having an amplifier, a signal arangement for indicating the existence of a predetermined condition of operation of the sound recording apparatus comprising, in combination, are generative feed-back connection from an output circuit to an input circuit of said amplifier to produce an audio-frequency feed-back, switching means in said feed-back connection operative upon the occurrence of said predetermined condition of said apparatus to complete said feed-back circuit, and a translating means connected to the input circuit of said amplifier for producing an audible signal upon completion of said feed-back circuit.
2. In a sound recording machine having an amplifier, a signal arrangement for indicating the existence of a predetermined condition of operation in the sound record apparatus comprising, in combination, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier to produce an audioirequency signal, means to control thefrequency of said audio-frequency signal, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to the input circuit of said am plifier for producing an audible signal upon completion of said feed-back circuit.
3. A signal arrangement for indicating the existence of some predetermined condition of operation in a sound recording apparatus, comprising, in combination, an amplifier, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier to produce an audio-frequency, means to control the magnitude of said audio-frequency, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to the input circuit of said amplifier for producing an audible signal upon operation of said feed-back circuit.
4. In a sound recording apparatus having an amplifier, a signal arrangement for indicating the existence of some predetermined condition of ane operation in ,said, recording apparatus comprising, in combination, a regenerative feed-back connectionfrom the output circuitto the input cir-- cuitoftarportion oft-said amplifierfito produce an audiosignal, means in saidlfeed i-back circuit-for controlling.- the. frequency of" said audio signal, switching means in said feed-back connection responsive to the occurrence of said predetermined condition to complete said feed-back circuit, and reversible translating means connected to said amplifier for producing an audible signal upon operation of said feed-back circuit.
5. In sound recording apparatus a signal arrangement for indicating the existence of some predetermined condition of operation in the apparatus comprising, in combination, an amplifier, a regenerative feed-back connection from an output circuit to an input circuit of said amplifier to produce an audio-frequency signal, means in said feed-back circuit for controlling the magnitude of said signal, means in said feed-back circuit to control the frequency of said signal, switching means in said feed-back connection responsive upon the occurrence of said predetermined condition to complete said feed-back circuit, and translating means connected to said amplifier for producing an audible signal upon completion of said feed-back circuit.
6. In a sound recording machine, a signal arrangement for indicating the existence of a predetermined condition of operation of said machine, comprising, in combination, an amplifier, regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier, switching means responsive to the occurrence of said predetermined condition to complete said feed-back circuit and cause said amplifier to generate an audio-frequency signal, and a reverse acting translating device connected to the input of said amplifier to act as a microphone during recording and as a loud-speaker upon the operation of said switching means whereby an audible signal is produced at any remote location near the operator to warn of the existence of said predetermined condition of operation of the recording machine.
7. In a sound recording machine a signal arrangement for indicating the existence of a predetermined condition comprising, in combination, a sound amplifier, a regenerative feed-back connection from the output circuit to the input circuit of a portion of said amplifier, switching means responsive to the occurrence of said predetermined condition to complete said feed-back circuit and cause said amplifier to generate an audio-frequency signal, and a piezoelectric crystal translating device connected to the input of said amplifier to act as a microphone and adapted to produce an audible signal on occurrence of said predetermined condition.
8. In sound recording apparatus, a signal arrangement for indicating the existence of a predetermined condition of operation of said recording apparatus comprising, in combination, a; vacuum-tube amplifier, a sound recording element coupled to the output of said amplifier, a recording surface adapted to be engraved by said element, a regenerative feed-back circuit from the output circuit to the input circuit of a portion of said amplifier, switching means in said feedback circuit responsive to the lateral position of said recording means on said recording surface to complete said feed-back circuit, and reversible translating means connected to said amplifier ands-adapted ton pro'duceuan audible") signal up on operations of.:sa1d.ifeed-back circuit,
9. In a sound recordingzmachine, aisignalar rangementlaforlindicatingstlie existence of a predetermined condition of operation of said recording machine comprising; incombination, a vacuum-tube. amplifier, ,a recordingelement, a record adapted to be engraved by saidielment a record driving mechanism for rotating said record, a regenerative feed-back circuit from the output circuit to the input circuit of a portion of said amplifier, switching means in said feed-back circuit responsive to rotation of said record driving mechanism to complete said feed-back circuit, reversible translating means connected to said amplifier and adapted to produce an audible signal upon completion of said feed-back circuit.
10. In a sound recording machine, a signal arrangement for indicating the existence of a predetermined condition of operation of said recording machine comprising, in combination, a vacuum-tube amplifier, a sound recording element coupled to the output of said amplifier, a record adapted to be engraved by said recording element, control means for manually determining the position of said recording element relative to said recording surface, a positive feed-back circuit connected between an output and an input circuit of said amplifier switch means in said feedback circuit responsive to the position of said recording element relative to said surface, and reversible translating means connected to said amplifier and adapted to produce an audible signal upon completion of said feed-back circuit.
11. A remotely operated dictating apparatus, comprising, in combination, a sound amplifier, a crystal microphone connected to the input terminals of said amplifier, a record, a recording element connected to the output of said amplifier.
and adapted to record sound signals on said record, a driving mechanism for rotating said record, a regenerative feed-back circuit coupled between output and input circuits of said amplifier to produce an audio-frequency feedback, means in said feed-back circuit for controlling the fre-, quency of said audio feedback, means in said feedback circuit for controlling the magnitude of said feedback, and switch means in said feed-back circuit responsive to a predetermined condition in said recording apparatus to complete said feedback circuit causing said amplifier to oscillate at an audio-frequency rate, thereby causing said microphone to emit an audible warning signal upon occurrence of said predetermined condition.
12. A remotely operated dictating apparatus comprising, in combination, a sound amplifier having input and output vacuum tubes, a resistor connected between the grid and cathode circuit of said input tube and a crystal microphone connected in parallel therewith, a record, a recordin element connected to the output of said amplifier and adapted to record sound signals on said record, a driving mechanism for rotating said record, a regenerative feed-back circuit comprising a capacitor connected in series with a variable resistor between the plate of said output tube of said amplifier and the grid of said input tube to produce an audio-frequency feedback, a relay actuating coil responsive to the existence of a predetermined condition of operation in said recording apparatus, and relay contacts operated by said relay actuating coil to complete said feedback circuit causing said amplifier to oscillate at an audio-frequency rate, whereby said microphone is caused to produce an audible warning 7 8 signal at any remote location near the operator to warn of the existence of said predetermined UNITED STATES PATENTS condition of operation. Number Name Date LUCIUS RPETRUSCHELL. 07, av y u y 9, 1940 5 2,305,681 Dunning Dec. 22, 1942 REFERENCES CITED 2,320,429 Hasbrouck, Jr. June 1, 1943 The following references are of record in the file of this patent:
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615078A (en) * 1949-12-29 1952-10-21 Ohmega Lab Frequency analyzer system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2207539A (en) * 1939-07-26 1940-07-09 Brush Dev Co Piezoelectric apparatus
US2305681A (en) * 1940-06-12 1942-12-22 Edison Inc Thomas A Phonograph system
US2320429A (en) * 1940-08-20 1943-06-01 Rca Corp Signal recording and reproducing system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2207539A (en) * 1939-07-26 1940-07-09 Brush Dev Co Piezoelectric apparatus
US2305681A (en) * 1940-06-12 1942-12-22 Edison Inc Thomas A Phonograph system
US2320429A (en) * 1940-08-20 1943-06-01 Rca Corp Signal recording and reproducing system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615078A (en) * 1949-12-29 1952-10-21 Ohmega Lab Frequency analyzer system

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