US873042A - Apparatus for receiving and strengthening the reproduction of messages, signals, &c. - Google Patents

Apparatus for receiving and strengthening the reproduction of messages, signals, &c. Download PDF

Info

Publication number
US873042A
US873042A US37145107A US1907371451A US873042A US 873042 A US873042 A US 873042A US 37145107 A US37145107 A US 37145107A US 1907371451 A US1907371451 A US 1907371451A US 873042 A US873042 A US 873042A
Authority
US
United States
Prior art keywords
magnet
magnets
circuit
receiving
reproducing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US37145107A
Inventor
Emil Schack Hagemann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AMERICAN TELEGRAPHONE Co
Original Assignee
AMERICAN TELEGRAPHONE Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AMERICAN TELEGRAPHONE Co filed Critical AMERICAN TELEGRAPHONE Co
Priority to US37145107A priority Critical patent/US873042A/en
Application granted granted Critical
Publication of US873042A publication Critical patent/US873042A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor

Definitions

  • the said Poulsen invention also describes a MANN, a subject of the King of Denmark, remethod of wiping out or eliminating the siding at Copenhagen, in the Kingdomv of magnetic record or impression made in the Denmark, have invented certain new and wire, which consists in connecting up the useful Improvements entitled An Apparasame electro-magnet or any other electro- 60 tus for Receiving and Strengthening the Rem'agnet with a source of constant current, production of Messages, Signals, and the such as a battery, and' again passing the Like, (for which I-have applied for patents wire from end to end across the poles of the in Germany and Denmark, and which apmagnet.
  • This demagnetizes or produces plications are dated April 20, 1900, April a neutral condition throughout the whole 65 21, 1900,) of which the following is a specifilength of wire, whereupon it is again ready cation. to receive another record.
  • This invention relates to an. apparatus
  • the strength of the reproduced message for elect-ro-magnctically recording speech orin the receiving apparatus largely depends other signals, and reproducing the same, and upon the amount of resistance in the several 70 has special reference to the principle diselectric circuits utilized in the recording and closed in Letters Patent of the United States reproducing operations; for instance, a given No. 661,619, issued November 13, 1900, to record will be reproduced from the machine,
  • the object of the present invention is, priratus over a short circuit than over a long 75 marily, to provide means for amplifying or circuit.
  • the present invention is therefore strengthening the sounds or electrical imintended to amplify the sounds, or force of pulses reproduced from the instrument and the reproduced speech or signal, with any delivered to the receiving apparatusyto an given condition of resistance of circuits.
  • the amount or extent 85 the Poulsen instrument referred to, the elec of the amplification or increase in-the reprotrical impulses set up by the transmitting induction is therefore theoretically limited only strument, flow through an electro-magnet, by the number of records made and simultawhose poles are resting in contact with a steel neously reproduced, and it is evident that wire, the wire being simultaneously moved or for transmitting messages telephonically over 90 dragged past the poles.'
  • the varying maglong distances, unattainable in ordinary tele- 'netism thus created in the magnet, is imphone practice, it is only necessary to insert parted to successive portions of the steel atone or more points in the circuit, an ampli- 40 Wire, which retains the impressions, since i'yingapparatus of the character herein desteel is a paramagnetic body.
  • Facing ring 1 is an arc-shaped frame c, carrying on its inner face, a series of electro-magnets respectively lettered e, 6, e e etc.
  • the pole pieces of these magnets are presented to and preferably rest in contact ing pair are connected together in a closed circuit, by the wires g, said wires being connected to the terminals of the coils of each magnet.
  • h, h, h h etc. indicate another seriesof electro-inagnets, supported by a suitable part of the framework, as shown, being attached to the base of the instrument, and arranged in a horizontal line with their poles presented to'and preferably in contact with the respective rings, 1, 2, 3, etc.
  • These magnets h are all connectedtogether in series in the circuit 1", 1".
  • the circuit 9', 7c leads to and includes magnet e, which is the main re-
  • the circuit 1', 1* includes a suitable receiving apparatus R, which may be a telephone receiver.
  • Both the transmitting and receiving circuits may extend any distances from the relay instrument, whose o eration is as folfiat the cylinder is being rotated at a constant speed in the direction of the arrow in Fig. 2.
  • Speech or other signal is delivered to the transmitting apparatus T, and electrical impulses corresponding thereto, are thus created in the circuit j, k, which includes magnet c.
  • This magnet is therefore variably magnetized by the successive impulses, and its magnetic conditionis imparted to successive portions of the steel ring 1, against which its pole or poles rest.
  • the ring 1 and the magnet e correspond with the steel wire and magnet of the Poulsen instrument, and that instead of using the same magnet for reproducing as for recording, I use a second, a third and a fourth, etc. magnet of similar character, represented by e, 0 6 etc, placed on the same wire, so that the reproduction therefrom is obtained immediately after the record is made, the speed of the drum being such that the message is not perceptibly interrupted or retarded in traveling from the transmitting instrument T to the receiving instrument R.
  • the magnet e is a recording magnet
  • magnets e, e 0 etc. are all reproducing magnets
  • the magnets f, f f etc. are all recording magnets
  • the magnets h, h, h etc. are all reproducing magnets.
  • the instrument embodies a number of Ioulsen instruments all working together.
  • a receptive device in or upon which a record of the speech or signals is to be made, a transmitting circuit leading to said device, recording mechanism operated by said transmitting circuit, a receiving circuit leading from said device and means for re roducing and augmenting the record in sai receiving circuit.
  • a telephone relay consisting of a plurality of para-magnetic bodies, means for making a permanent magnetic record of speech thereon and means for simultaneously reproducing the speech from said bodies in a single receiving apparatus, substantially as described/ 11.
  • a telephone or telegraph rela consisting of means for making a plura ity of permanent magnetic records of a message or signal, in combination with means for simultaneously reproducing all of said records in a receiving apparatus.

Landscapes

  • Recording Or Reproducing By Magnetic Means (AREA)

Description

APPARATUS FOR R EGEIVIN 0P MESSAGES, SIGNALS,;&0.
- PATENTED DEGL10',1907., B. s. HAGEMANLL, 6 AND STRENGTHENING THE REPRODUCTION.
APPLICATION FILED um: 19. 1900. nnnnwnn nu 2,1901.
- 2 SHBBTB-SHEET 1.
I w ll I 016', wwwea WWII Q --J a WI I g iI'WW I Jail -alllll lk-q N0- a7s,042. PATENTED DEC. 10, 1007.
E. s. HAGEMANN.
APPARATUS FOR RECEIVING AND STRENGTHENING THE REPRGDUGTION 0F MESSAGES, SIGNALS, 6w. APPLIOATIOH FILED mm: 10, 1000. nmwnwnn MAY 2, 1007.
2 SHEETS-SHEET 2.
WITNESSES UNITE STATES PATENT. OFFICE.
EMIL SCHACK HAGEMANN, OF COPENHAGEN, DENMARK, ASSIGNOR, BYMESNE ASSIGNMENTS, TO AMERICAN TELEGRAPHONE COMPANY, A CORPORATION OF THE DISTRICT OF COLUMBIA.
APPARATUS FOR RECEIVING AND STRENGTHENING TEE REPRODUCTION OF MESSAGES, SIGNALS, 8w.
N 373 042 v Specification of Letters Patent. Patented Dec. 10, 1907. Application filiad June 19. 1900. Serial No. 20.816- Renewed Hay 2. 1907. Serial No. 871.451.
T all whom it may concern: sent through the transmitting apparatus. 55
Be it known that I, EMIL SCHACK IIAGE- The said Poulsen invention also describes a MANN, a subject of the King of Denmark, remethod of wiping out or eliminating the siding at Copenhagen, in the Kingdomv of magnetic record or impression made in the Denmark, have invented certain new and wire, which consists in connecting up the useful Improvements entitled An Apparasame electro-magnet or any other electro- 60 tus for Receiving and Strengthening the Rem'agnet with a source of constant current, production of Messages, Signals, and the such as a battery, and' again passing the Like, (for which I-have applied for patents wire from end to end across the poles of the in Germany and Denmark, and which apmagnet. This demagnetizes or produces plications are dated April 20, 1900, April a neutral condition throughout the whole 65 21, 1900,) of which the following is a specifilength of wire, whereupon it is again ready cation. to receive another record. This invention relates to an. apparatus The strength of the reproduced message for elect-ro-magnctically recording speech orin the receiving apparatus, largely depends other signals, and reproducing the same, and upon the amount of resistance in the several 70 has special reference to the principle diselectric circuits utilized in the recording and closed in Letters Patent of the United States reproducing operations; for instance, a given No. 661,619, issued November 13, 1900, to record will be reproduced from the machine,
V. Poulsen. more loudly or forcibly. in the receiving appa- The object of the present inventionis, priratus over a short circuit than over a long 75 marily, to provide means for amplifying or circuit. The present invention is therefore strengthening the sounds or electrical imintended to amplify the sounds, or force of pulses reproduced from the instrument and the reproduced speech or signal, with any delivered to the receiving apparatusyto an given condition of resistance of circuits. In
extent more than can be done with the inaccomplishing this Ire'cord the message upon 80 strument as described in the said Poulsen a plurality of different steel wires or bodies, patent. In accomplishing this, I produce a and in reproducing, I utilize all of the records species of relay or repeater, which may be simultaneously, to produce a joint or cumuused in transmitting telephonic and telelative effect in the circuit containing the re graphic messages over long distances. In ceiving apparatus. The amount or extent 85 the Poulsen instrument referred to, the elec of the amplification or increase in-the reprotrical impulses set up by the transmitting induction is therefore theoretically limited only strument, flow through an electro-magnet, by the number of records made and simultawhose poles are resting in contact with a steel neously reproduced, and it is evident that wire, the wire being simultaneously moved or for transmitting messages telephonically over 90 dragged past the poles.' The varying maglong distances, unattainable in ordinary tele- 'netism thus created in the magnet, is imphone practice, it is only necessary to insert parted to successive portions of the steel atone or more points in the circuit, an ampli- 40 Wire, which retains the impressions, since i'yingapparatus of the character herein desteel is a paramagnetic body. After the rccscribed. .ord has thus been made, it can be reproduced My invention will be described in detail by again passing the same or a similar magwith reference to the accompanying drawing, net over that portion of the wire which rein which i ceived the impressions and connecting the Figure lisaside elevation of my improved magnet in circuit with areceivin apparatus, relay apparatus ;-Fig. 2 is an end elevation such as a tele hone receiver. 11 this case thereof; Fig. 3 is a diagrammatical or conthe magnetic ines of force in the Wire are ventional view, corresponding to Fig. 1; Fig. communicated to the core of the electro- 4 is -a similar view corresponding to Fig. 2,
60 magnet and thus induce corresponding curand-Figs. 5 and 6 show modifications of my rents of electricity in the coil 0 the electroinvention. magnet which flow to, and afiect the receiv- Referring to the drawing by letter, A indiing apparatus, and reproduce therein the cates a cylinder or drum mounted on a shaft same sounds or signals that were originally a in bearings a, and fitted with a pulley 'a through which it may be rotated from any suitable source of power. On the surface of this cylinder, are applied a number of steel rings or hands, lettered respectively, 1, 2, 3, 4 etc. ring, so-as to present a smooth endless surface. Facing ring 1 is an arc-shaped frame c, carrying on its inner face, a series of electro-magnets respectively lettered e, 6, e e etc. The pole pieces of these magnets are presented to and preferably rest in contact ing pair are connected together in a closed circuit, by the wires g, said wires being connected to the terminals of the coils of each magnet. h, h, h h etc. indicate another seriesof electro-inagnets, supported by a suitable part of the framework, as shown, being attached to the base of the instrument, and arranged in a horizontal line with their poles presented to'and preferably in contact with the respective rings, 1, 2, 3, etc. These magnets h are all connectedtogether in series in the circuit 1", 1". Beyond the series of magnets h is still another series of magnets'i, 'i, etc-., corresponding respectively, and in contact with the several rings 1, 2, 3, 4, etc. These magnets are all connected in circuit with a source of constant current, such as a battery I. The initial message is sent to the instrument through a circuit j, 7c, containing a transmitter T and the usual equipment of battery'M, and may also contain an induccording magnet of the instrument.
- lows: Let it be assumed t tion coil in the usual way, this, however, not being illustrated; The circuit 9', 7c leads to and includes magnet e, which is the main re- The circuit 1', 1* includes a suitable receiving apparatus R, which may be a telephone receiver.
Both the transmitting and receiving circuits may extend any distances from the relay instrument, whose o eration is as folfiat the cylinder is being rotated at a constant speed in the direction of the arrow in Fig. 2. Speech or other signal is delivered to the transmitting apparatus T, and electrical impulses corresponding thereto, are thus created in the circuit j, k, which includes magnet c. This magnet is therefore variably magnetized by the successive impulses, and its magnetic conditionis imparted to successive portions of the steel ring 1, against which its pole or poles rest. These magnetic impressions are Each of these is a completely closed.
rotates the cylin er.
said magnet e, 6 e etc., in the well understood manner of a dynamo electric machine,
the power being su plied by the motor which The current generated in the magnet c, flows over the connecting wires g, through the magnet which is resting upon ring 2; hence the mstant a magnetic impulse or impression in the ring 1,-passes the magnet e, it will be accompanied in its further movement onward, by an exactly similar magnetic impression in the ring 2, the two impressions traveling abreast; as it were, towards the receiving magnets h, h, etc. The impression in the ring 1 reaches the magnet h at the same instant that the impression in the ring 2 reaches the magnet h; hence magnets h and h which then become receiving magnets, will'have similar current impulses generated in their coils, and since these coils are connected together in the same circuit, their electromotive forces will combine andbe theoretically double that which is produced by either magnet acting alone. After a given magnetic impression in the ring 1, has passed the magnet e,it acts upon themagnet e and sends therefrom a current which energizes magnet j, which, in turn, impresses a corresponding magnetic impression on rlng circuit 1", 1*, theoretically, three times the electromotive force that could be reproduced from any one ring. In like manner the same magnetic impression in ring 1., will be'communicated to ring 4, and act upon the circuit 1", r at the same time with theothers, and soon throughout the entire capacit of the instrument, a given "ma netic imp ession being conveyed and simultaneously presented to the magnets h, it, etc. upon respective rings 1, 2, 3, etc. receiving circuit 1", 1* is a current impulse having an electromotive force equal to the combined electromotive forces produced by the respective rings. leaving the instrument and roceeding to the receiver R, are thus muc stronger than could be obtained by the use of a single re producing magnet only.
The result in the.
The current impulses It will be understood that there willbe some loss due to the resistance of the coils of the intensity of the ring 1, is obtained on each ring 2, 3, 4, etc., then 25 rings wilLbe necessary in order to reproduce the message with its original intensity.
On comparing the relay instrument with the instrument described in the Poulsen patent referred to, it will be seen that the ring 1 and the magnet e correspond with the steel wire and magnet of the Poulsen instrument, and that instead of using the same magnet for reproducing as for recording, I use a second, a third and a fourth, etc. magnet of similar character, represented by e, 0 6 etc, placed on the same wire, so that the reproduction therefrom is obtained immediately after the record is made, the speed of the drum being such that the message is not perceptibly interrupted or retarded in traveling from the transmitting instrument T to the receiving instrument R. It will be seen that the magnet e is a recording magnet, the
magnets e, e 0 etc. are all reproducing magnets, the magnets f, f f etc. are all recording magnets and the magnets h, h, h etc. are all reproducing magnets. Hence the instrument embodies a number of Ioulsen instruments all working together.
In order to be able to use the instrument continuously for transmitting a message, it is necessary to eliminate the magnetic impressions from each of the rings after they have been utilized to repeat the message, and before the same portions of the rings again pass the poles of the recording magnets. To accomplish this, the magnets i, t, i etc. connected with the constant source of current I, are placed beyond the reproducing magnets h, it, etc. in the direction of the rotation, and they wi e off the message and allow the rings to fie presented clean and ready for the new message or anotherpart of the same message.
It is not necessary to use a cylinder or drum with rings upon its surface, as described, since steel ribbons suitably mounted to move with respect to the poles of the magnets, can be used to produce the same result. It is also obvious that since the function of the connected magnets e and f etc. is merely to transfer magnetism from a ma netized body to one which is not magnetized, an iron brid e connecting the two bodies together, could also be used, this construction is shown in Fig. 5. The magnetic impression from the ring 1 magnetizes the bridge 8, which, in turn, similarly magnetizes the rmg 2, 3 or 4, with which it is connected. It
- is also obvious'that the transmitting circuit 7', 7c, could be made to actdirectly upon all of the rings 1, 2, 4, 5, etc. by simply connectin a number of the magnets e in the circuit and applying one magnet to each of the ,stanti'ally as described. In an apparatus for electro-magnetic- 130 rings. This method, however, has its objections, from a practical standpoint, and is merely mentioned .as a possible way ofoperating.
Having described my invention, I claim:
1. The combination of a telephone transmitting circuit and a telephone receiving circuit, with an instrument adapted to electromagnetically record a message from the transmitting circuit and simultaneously electro-magnetically reproduce the said message in the receiving circuit, and means whereby the strength of the message delivered to the receiving circuit is made greater than that recorded from the transmitting circuit.
2. In an apparatus for electro-magnetically recording and reproducing speech or signals, the combination of a receptive device, a transmitting circuit, means for making a plurality of records in said. device of the speech or signals traversing the transmitting circuit, a receiving circuit and means for simultaneously reproducing corresponding portions of each record in said receiving cir- I cuit, substantially as described. 7
3. In an apparatus for recording and reproducing speech or signals, the combination of a receptive or recording body or surface, a recording device adapted to act upon said body or surface, a reproducing device and an obliterating device presented at successive \points thereto, whereby s eech or signals may be recorded on the b0 y or surface, re produced therefrom and obliterated in succession, substantially as described.
4. In an apparatus for electro-magneticall recording and reproducing speech or signa s, the combination'of a receptive device in or upon which a record of the speech or signals is to be made, a transmitting circuit leading to said device, recording mechanism operated by said transmitting circuit, a receiving circuit leading from said device and means for re roducing and augmenting the record in sai receiving circuit.
5. In an apparatus for electro-magnetically recording messages'and signals, the combination of'a receptive body or surface, two electro magnets presented at successive points thereto, one for recording a message or signal on the body or. surface, and the other for reproducing it therefrom, and one or more receptive bodies or surfaces, each having a recording and reproducing magnet presented to it at successive points; the re producing magnet of the first set being connected with the recording magnet of the second, and soon throughout the series, and means for moving all of the bodies or sur-- faces and their respective magnets simultaneously with respect to each other, whereby the message or signal may be successively recorded, reproduced and transmitted, subbodies or surfaces,
. ally recording and reproducing messages or slgnals, a receptive body or surface, a recording magnet presented thereto, one or more reproducing magnets also presented thereto at successive points following the recording magnet, one or more other receptive bodies or surfaces, a recording magnet for each of the same, connected respectively with the reproducing receptive body or surface, a receiving electric circuit containing a plurality of magnets presented respectively to the said receptive and means whereby similar magnetic impressions will be Inade in each receptive body or surfacefand all simultaneously magneto electrically impressed upon the said receiving circuit, substantially as described.
7. In an apparatus for electro-magnetically recording and reproducing messages or signals, the combinatlon of a receptive body or surface, a recording magnet, a reproducing magnet and an obliterating magnet presented at successive points thereto, whereby a message or signal may be recorded on the body or surface, reproduced therefrom and o'bliterated in succession, substantially as described. v
8. In an apparatus'for electro-magnetically recording and reproducing messages or signals, the combination of an endless recept1ve body or surface, a recording magnet, a
reproducing magnet and an obliterating magnets presented to the first stantially as described.
9. In an apparatus for electro-magnetically recording and re roducing messages or. signals, the combination of a plurality of receptive bodies or surfaces, means whereby a message or signal can be impressed upon each of said bodies or surfaces and means for reproducing the message or signal simultaneously from all of said bodies or surfaces.
10. A telephone relay consisting of a plurality of para-magnetic bodies, means for making a permanent magnetic record of speech thereon and means for simultaneously reproducing the speech from said bodies in a single receiving apparatus, substantially as described/ 11. A telephone or telegraph rela consisting of means for making a plura ity of permanent magnetic records of a message or signal, in combination with means for simultaneously reproducing all of said records in a receiving apparatus.
' In testimony whereof I have hereunto set my hand in the presence of two witnesses.
Witnesses A. LEIsNER, A. LIMOMEN.
US37145107A 1907-05-02 1907-05-02 Apparatus for receiving and strengthening the reproduction of messages, signals, &c. Expired - Lifetime US873042A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US37145107A US873042A (en) 1907-05-02 1907-05-02 Apparatus for receiving and strengthening the reproduction of messages, signals, &c.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US37145107A US873042A (en) 1907-05-02 1907-05-02 Apparatus for receiving and strengthening the reproduction of messages, signals, &c.

Publications (1)

Publication Number Publication Date
US873042A true US873042A (en) 1907-12-10

Family

ID=2941489

Family Applications (1)

Application Number Title Priority Date Filing Date
US37145107A Expired - Lifetime US873042A (en) 1907-05-02 1907-05-02 Apparatus for receiving and strengthening the reproduction of messages, signals, &c.

Country Status (1)

Country Link
US (1) US873042A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2468224A (en) * 1945-05-11 1949-04-26 Bell Telephone Labor Inc Magnetic reproducer using endless tape records
US2610257A (en) * 1949-12-22 1952-09-09 Warner Bros Magnetic record volume control
US2723315A (en) * 1948-11-05 1955-11-08 Indiana Steel Products Co Method and means for duplicating magnetic records by magnetic transfer phenomenon
US2747027A (en) * 1948-11-05 1956-05-22 Armour Res Found Recording apparatus and method for making duplicate magnetic records
US2747026A (en) * 1948-11-18 1956-05-22 Armour Res Found Recording apparatus and method for making duplicate magnetic records
US2816174A (en) * 1952-04-26 1957-12-10 Rca Corp Magnetic compression system
US2900191A (en) * 1953-02-11 1959-08-18 Dictaphone Corp Dictation apparatus
US3081457A (en) * 1949-03-03 1963-03-12 Int Standard Electric Corp Decade method of noise reduction

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2468224A (en) * 1945-05-11 1949-04-26 Bell Telephone Labor Inc Magnetic reproducer using endless tape records
US2723315A (en) * 1948-11-05 1955-11-08 Indiana Steel Products Co Method and means for duplicating magnetic records by magnetic transfer phenomenon
US2747027A (en) * 1948-11-05 1956-05-22 Armour Res Found Recording apparatus and method for making duplicate magnetic records
US2747026A (en) * 1948-11-18 1956-05-22 Armour Res Found Recording apparatus and method for making duplicate magnetic records
US3081457A (en) * 1949-03-03 1963-03-12 Int Standard Electric Corp Decade method of noise reduction
US2610257A (en) * 1949-12-22 1952-09-09 Warner Bros Magnetic record volume control
US2816174A (en) * 1952-04-26 1957-12-10 Rca Corp Magnetic compression system
US2900191A (en) * 1953-02-11 1959-08-18 Dictaphone Corp Dictation apparatus

Similar Documents

Publication Publication Date Title
US873042A (en) Apparatus for receiving and strengthening the reproduction of messages, signals, &c.
US1828190A (en) Method of preparing a magnetizable body to receive and reproduce wave frequencies
US2312897A (en) Method of transmitting signals
US1828189A (en) Method of recording and reproducing wave frequencies
US873541A (en) Method of receiving and strengthening the reproduction of speech signals, &c.
US1941618A (en) Multiple system
US699630A (en) Method of recording messages, signals, & c.
US2006961A (en) Secret signaling
US900392A (en) Sound recording and reproducing instrument.
US934601A (en) Sound-record.
US752858A (en) Pedek oltje pedebsen
US873083A (en) Telegraphone.
US882328A (en) Amplifying-magnet system for telegraphones.
US1459202A (en) Method of sensitizing the telegraphone
US3319241A (en) Electromechanical data transmission
US768541A (en) Means for intensifying telephonographic records.
US685239A (en) Apparatus for recording and repeating telephonic speech.
US1792859A (en) Sound-recording apparatus
US384323A (en) mallett
GB131131A (en) Improvements in Electrical Signalling Apparatus.
US2863712A (en) Electric printer for magnetic codes
USRE18126E (en) Phone labqsatokies
US619157A (en) Chusetts
US1381698A (en) System of train control
US1812635A (en) Signaling system