US2179445A - Signal transmission method and apparatus - Google Patents

Description

Nov. 7, i939. A. G. cooLEY S I GNAL TRAN SM I S S ION METHOD AND APPARATUS Filed oct. l. 193e INVENToRs BYfzQ/ Mm... i

Patented `Nov. 7, 1939 PATENT OFFICE ,altaar SIGNAL TRANSMISSION METHOD AND APPARATUS Austin c. Cooley. numeral-a, N.' J., manor to Wide World Photos, Inc., New York, N. Y., a corporation oi' New York Application october 1, 193s, smal No. 103,506I encinas. (ci. 11s-zi This invention relates to transmission systems and more particularly to system of transmission employing telephonefacilities as the transmission medium or as a connecting link in a transmission system.

An object of the invention is to provide a system of transmission of graphical representations., pictures, etc., whereby the usual telephone service line may be employed as a connecting link between a transmitter and a receiver, but without the necessity of eifecting physical connection to the line wires proper.

Various methods of coupling a picture signal transmitter or a picture signal receiver to a telephone line have been proposed heretofore. Thus in one type of system thef picture signals are translated into acoustic waves which are acousticallyfmpressed upon the usual telephone transmitter. One of the serious objections to the acoustic method is the unavoidable distortion that is introduced in the signal transmission. I have found that it is possible to employ the usual telephone service wire or wires for such traon as electro-optical transmission, without introducing any appreciable distortion and without making Vany physical connection to the line wires' proper; -V In carrying out this object ot the invention, the picture or electro-optical signals are impressed on the telephone line preferably byl electro-magnetic induction through the intermediary of the ear-piece or receiver of the usual telephone subscribers set.

A feature of the invention relates to a novel form of coupling member whereby electric signals may be applied to a telephone line by electromagnetic induction through the ear-piece or receiver of a telephone set.

Another feature relates to a novel coupling for applying signals to a telephone line through the usual ear-piece or receiver. the coupling means being provided with adjusting means whereby satisfactory coupling eiliciency to the line may be attained on various types of telephone receivers,

but without actual or physical connection tothe line. y

A further feature vrelates to a novel coupling arrangement whereby the usual telephone service l for picture or electro-optical transmission, without physicaiconnection t9 Ph? Wires and without disturbing the normal functioning of the telephone plant or equipment. As a result of this feature, it is possible to employ any telephone earpiece or receiver as a transmitter link for the purpose of electro-optical transmission, thus saving time required to install apparatus usually employed for that purpose. i

A still further feature relates to the novel organization, arrangement and relative location of parts which go to make up an improved electro-optical transmission system, and an improved device for coupling electro-optical apparatus to a telephone line without physical connection thereto.

Other features and advantages not specifically enumerated will become apparent after a consideration of the following detailed descriptionsv and the appended claims. In the drawing,

Fig. 1 is a composite schematic circuit diagram of an electro-optical system embodying features of the present invention.

Fig. 2 is a view partly in section, of an improved coupling device according to the invention.

Fig. 3 is a detailed view of part of the structure shown in Fig. 2. y

Fig. 4 is a view of a modification of the device of Fig. 2.

Fig. 5 is a schematic diagram showing a modication of part of the system shown in Fig. 1.

Referring to Fig. 1 there is shown in general- -ized schematic form a typical signal transmission system to which the invention may be applied. While the drawing shows, merely for explanatory purposes, the invention as embodied in an electrooptical transmission system, it will be understood that it is equally well applicable to similar systems of transmission, e. g., facsimile, printing telegraph, and in fact to any system where signais representing intelligence to be communicated are to be applied to a telephone line without physical connection thereto. In Fig. 1 the numerel l represents schematically any well-known form of electro-optical transmitter whereby the light values of a representation to be transmitted are translated into corresponding electric currents. Preferably vthe device l is of such a type that the signals are translated into a correspondingly modulated carrier Wave or other wave having an inherent frequency component which is directly and positively related to the speed of the electro-optical scanningor analyzing mechanism.

For a detailed description of such a device refer-V.

ence may be had to Patent No. 2,045,294, issued to Austin G. Cooley on June 23, 1936. .g

The output of the device I consisting preferably of an audio frequency signal-modulated carrier wave, may be applied to a terminal amplifier tube represented schematically by the numeral 2, although it will be understood that the tube 2 may be the last or output stage of the amplifier usually incorporated as' part of the device I. The output circuit of tube 2 is represented schematically as including the primary winding 3 of a suitable output coupling transformer, although any other well-known form'of coupling may be employed. 'I'he secondary winding 4 of the output transformer is preferably connected through a polarizing battery 5 to the movf ing switch. The xedcontacts of switch 5 are connected to the coils 1, 8 of an electro-magnetic coupling device 9.

As shown more clearly in Fig. 2 this coupling device comprises a U-shaped laminated iron core I on each leg of which is mounted one ofthe coils 1, 8. The coupling device 9 is arranged to be mounted in predetermined spaced relation to the diaphragm II of any common type ear-piece or receiver, such for example asA the receiver of the usual telephone subscribers set. For this purpose the coupling magnet may be fastened in any suitable manner to the cross-bar I2 and suitable projections or pins I3 may be provided on t e core to engage a non-magnetic washer I4 so as `prevent the ends of the core from touching the diaphragm II. As shown in Fig. 2 the coupling device is designed for use with one wellknown form of telephone receiver the latter comprising an enclosing casing I -of .hard rubber or similar material Phaving suitably fastened on its the coils I1, I8. 'I'he diaphragm II is clamped in place between the peripheral edge of thecasing I5 and the annular rim I9 of the cap or the casing I5 in the well-known manner. As shown clearly in Fig. 2 the ends of core III project through the circular opening in the cap 20 into proximity with the coils I1 and I8. Preferably, although not necessarily, the core I0 is designed s'o that the spacing between the poles and the diaphragm is aboutthe same as the spacing between the poles of the receiver magnet and diaphragm.

The bar I2 carrying the coupling device may be held in place on the cap 20 in any suitable manner, preferably however it is held in place by a substantially closed cap 2| of rubber or other non-magnetic and 'sound-deadening material, this cap 2| being provided'with a flexible rim 22 which is capable of being stretched to t over the rim ofthe cap 20. The coupling device is thus held firmly in place without the necessity of employing screws or other similar fastening means, and the coupling device can be readily removed for adjustment or repair, without affecting the telephone receiver in any way. If. desired the cap. 2| may be provided with suitable binding posts 23 to which the lead wires to the coils 1, 8

4are connected. 1f desired also a compressible washer 24 may-lie inserted between the bar I2 and the rim of cap 2,0 as shown.-

In order that the telephone receiver may be used simultaneously for the purpose of impressing the locally generated sgnals'on the telephone line and also for-its usual purpose of translating distantly generated signals or for monitoring the locally generated signals, the rubber cap 2| is 75 provided with an outlet 25 into which iS tightly able arms of a double-pole double-throw revers interior the magnet |6 carrying at its upper ends mouth-piece 20, the latter being threaded on to tted the end 26 of a suitable listening tube. While any known form of listening tube or other arrangement may be employed, it is preferred to employ a tube constructed similar to a stethoscope having a pair of branched tubes 21, 28 with suitable ear-pieces at their ends (not shown).

Wel have found that with this arrangement, it is possible'for the 4coupling device to'be acting for purposes oi transmission at the same time that one is listening in through the tubes 21, 28 to the character of the transmission so as to detect any irregularitiesv thereon, i. e., for monitoring or to listen-in on signals transmitted back from the receiving station. It will be understood that the use of the listening tube is not necessary, and if desired Athe listening-in may be effected directly through the opening 25. As an alternative, the cap 2| may be provided with a series of perforations for listening-in purposes. When the signals are being transmitted in the form of a modulated vaudio-frequency carrier wave it is preferable to design the acoustic chamber defined by members 20, 2| 25, 26, 21 and 28, or a part thereof, so that,V

the acoustic carrier frequency component is suppressed at the ear-pieces of tubes 21, 28. This may be achieved by proportioning the length, internal diameter and frictional resistance" of the inner surface of tubes 21, 28 so as to absorb or attenuate the carrier frequency to the desired extent. Inasmuch .as the method of proportioning the characteristics of the ltubes 21, 28 for this purpose, is `well-known in the acoustic filtering art further description thereof is not deemed necessary herein. This acoustic chamber may also be employed as a load, or damping factor,

the telephone line. Thus the ear-pieces may be .used to monitor the outgoing signals. or they may be used to listen-in on signals that originate at ,the opposite -endvof the telephone line.

`While Fig. 1 of the drawing shows the coupling arrangement applied to one particular form of ,telephone line coupling, it will be understood that this is merely representative. Thus the modulated carrier wave which is impressed upon the coils 1, 8, is repeated by electro-magnetic induc- -tion through the coupling device described, to

the subscribers loopl comprising the repeating coil 30, 3|, the condenser 34, and the switch-hook contacts. A similar arrangement may be employed at the receiving end of the telephone line. Thus-the modulated carrier wave is received in the conventional manner by the telephone receiver 36 which carries a coupling device 31 similar tothe device 9. The received waves are transferred by electro-magnetic induction'to the conductors 38, 39 to the picture synthesizing or reproducing device represented schematically by 'the numeral 4|, which maybe of any wellknown type such for example as illustrated in ,Patent No. 2,045,294.

I have found that in order toaehieve the optimum coupling eiciency between the device 9 and. the telephone line it is necessary to polarize 76 the core In in a predetermined relation tol the normal polarization of the magnetA I 6.-

purpose preferably the output 'circuitpf the tube eiect optimum coupling. It will be imderstood" of course that any well-known method may be employed to synchronize the transmitting picture analya'er with the reproducing synthesizer, and

' preferably,l although not necessarily, the carrier receiver cap. The bar l2 carrying the couplingy Aco freuzlue'ncyl itself may be used for synchronizing as described in said Patent No. 2,045,294. It will be understood also that the invention is not necessarily limited to a system wherein the received picture signals are transferred to the reproducer 4l through the receiver 36, and it will be obvious to those familiar with the art that the received signals may be transferred from the telephone line 32, 35 to the device Il in any well-known manner. l

Instead of employing a separate polarizing battery such as the battery 5 for polarizing the coupling device, the usual plate supply source or battery of the output tube 2 may be employed for this purpose. Thus as shown in Fig. 5 the-"output or plate circuit of tube 2 including the usual.

plate supply source 43, is connected to the coupling coils l, 8 through the reversing switch t.

In certain cases, it may be desirable to adjust the spacing between the core I0 and the diaphragm it. While the arrangement shown in Fig. 2 enables the coupling core to be rotated around the vertical axis of the receiver merely by turning the cap 2i and while the spacing between the core it and magnet it may to a certain extent be varied by employing washers 2li of different thicknesses, it may be desirable to provide independent spacing adjustment. Thus as shown in Fig. 4 the cap may be formed in two parts it and tb the former being of a rigid nonmagnetic material, while the latter is preferably of a ilemble non-magnetic material, the two parts being either joined together as a unit or separable from each other. In the latter case the part d5 should have-sumclent resiliency to rmly grip the part M against the rim 2d of the core and coils is provided with two adjusting screws 4t, Il by means oi which the spacing between the core I 0 and the magnet I6 may be ac'- curately adjusted. Instead of fastening the adjusting screws 46, 41 to the bar l2 as shown', a spring or rubber washer (not shown) may be interposed between the bar and the rim 48 of the receiver cap, this spring or washer normally tending to impel the coupling unitV upwardly against the ends of the adjusting screws 46, l1. Likewise, if desired, a spring or rubber washer may be interposed between the stop disc I4 and the magnet coils., With this arrangement, therefore, -iti is possible to orientate the core I0 with respect to the magnet coils I1, i8; to polarlze electrically the coils 1, 8; and to adjust the spacing between the` core I0 and the'coils I and .8 or magnet I C for optimum results.

While certain preferred -embodiments have been disclosed herein it will be understood that various changes and modiiications may be made therein without departing from the Spirit and scope ofthe invention. For ,example while the drawing shows the coupling as applied to a service receiver of the type forming part of a deskset type telephone, it will be understood that the invention may be readily applied to service res ceivers of the so-called French or hand-phone V type, and that corresponding changes in dimensions of the parts can be readily made to accommodate them to the latter type of receiver. What is claimed is:

, 1. In a signaling system the combination of a line, a device at one end of said,line normally designed only to transmit signals to the line and another device at said end of the line normally designed only to receive signals from the line,

said otherV device including an electromagnet. and

electromagnet induction means positioned adjecent said electromagnet and energized by signal currents in the form of an audio frequency mod: ulated carrier to' be transmitted to the line for applying 'said signals to the line through said I electromagnetic means.

2. In a signaling system, the combination of a telephone line, a telephone service transmitter at. one end of said line designed normally only to transmit signals Vto the line, an electromagnetic telephone service receiver at said end of 'the line normally designed only to receive signals from" said line, electromagnetic induction means posi- `tioned adjacent said receiver and energized by signal currents to be transmitted for applying said signal currents to said line through said receiver for transmission to a distant station.

3. In a signaling system, the combination of a v telephone line terminating in a subscribers loop including a telephone service transmitter designedl normally only to transmit signals to the line and a service telephone receiver having an ear-piece designed normally only to receive sig? nals from-said line, a source of signals local to said loop and to be transmitted over said/telephone line, and electromagnetic means for applying saidsignals to said line by induction through said receiver for transmission to a distant station.

4. In a signalingsystem, the combination of a telephone line terminating in a subscribers loop', a service telephone receiver for said loop normally designed only to receive signals from the line and to reproduce them acoustically, said receiver including an ear-piece with a magnetiz-A ing coil, a source of other signals local to said ing a core positioned adjacent to but in spaced relation tosaid diaphragm, and means for energizing said electromagnet under `control of said picture signals for transmitting said picture signals to a distant station.

6. In a signaling system, the combination of a telephone line terminating in a subscribers loop,

a service telephone receiver for said loop having an ear-piece normally designed only to receive signals from said line to reproduce said signals acoustcally, said receiver having a magnet therein, means local to said loopnfor generating Asignals in the form of a modulatdcarrier wave;

and electromagnetic means for applying said wave to said line by electromagnetic induction throughl the magnet in said receiver".

7. In a signaling system, the combination of a telephoneline terminating in a subscribers loop,

a service telephone receiver for said loop having an ear-piece with a diaphragm and designed normally only to reproduce acoustically signals received from said line. a source of other signal currents local to said loop, a space induction device Aenergized by signals from saidV other source, means to moynt said device in spaced relation to said diaphragm; whereby said other signalsare transmitted to said line by electromagnetic coupling to said ear-piece, and means to limit the proximity of said device to said diaphragm.

8. In a signaling system, the combination of a telephone line terminating in a subscribers loop, a service telephone receiver for said loop and normally designed only to receive electric signals from the line and for reproducing said signals acoustically, an electromagnet mounted in spaced relation to the diaphragm of said receiver, means to pass Va steady polarizing current through said electromagnet and means to apply a signal modulated carrier wave to said electromagnet for transmission to a distant station over said telephone line. 9. In a signaling system, the combination of telephone line terminating at each end in a subscribers loop, each l'oop having associated therewith a telephone service transmitter and a telephone service receiver, the transmitter being designed normally only to transmit signals to the line and the receiver being designed normally only to receive signals from the line and to reproduce them acoustically, a picture signal transmitter, a picture signal receiver, and means to couple said receiver and transmitter to said line without physical connection thereto, the lastmentioned means including an electromagnet mounted adjacent the ear-piece of the service receiver at one of the subscribers loops for transmitting signals from the picture signal transmitter to the line electromagnetically through said service receiver.

10. In combination, a telephone service receiver normally designed only to receive telephone signals from the associated telephone line, f

said receiver having a magnet and diaphragm enclosed by an ear-piece, means to removably mount an electromagnet on said ear-piece in spaced relation to said diaphragm while allowing sound waves generated by said diaphragm to pass through said means, said electromagnet being arranged for energization by signals to be transmitted to the telephone line by electromagnetic induction from said electromagnet to said receiver magnet.

11. In a device of the character described, the

, combination of a pair of electromagnets, a sound reproducing diaphragm mounted between said electromagnets in spaced relation thereto, one of Vsaid electromagnets being designed normally for energization by incoming signal currents to reproduce said currents acoustically, the other of said electromagnets being designed for energization by outgoing currents for impressing said outgoing currents on said line electromagnetically through the rst electromagnet.

12. In combination a device of the character described comprising a diaphragm and a cooperating electromagnet normally designed'to be energized by sound currents received from a distant station, and another electromagnet mounted in spaced relation to the diaphragm andon the opposite side of the diaphragm from the "iirst electromagnet, and means to energize said other electromagnet by locally generated picture signal currents to induce picture currents into4 er having an ear-piece and an electromagnet enl ergized by received telephone currents to produce audible signals, a cover for said`ear-piece and forming therewith an acoustic chamber, another electromagnet mounted within said chamber in inductive relation to the iirst electromagnet, said cover having an opening for the emergence of sound waves.

15.- The combination according to claim 14 in which said chamber, together with said opening, are designed to act as an acoustic filter.

16. In combination a telephone service receiver having 'an ear-piece, a cover for said earpiece, a listening tube coupled with said cover and forming therewith an acoustic filter, said iilter being designed to suppress acoustic waves of an undesired frequency, and an electric coupling device mounted between said cover and said ear-piece.

1'7. In combination, a telephone lne, a telephone subscribers sub-station set connected to said line, said sub-station set having a service telephone receiver including a magnet energized by received telephone currents, means to transmit signals to the said telephone line through said receiver including an electromagnet energized by the signal currents to be transmitted, and means to polarlze said electromagnet by a steady polarizing current.

18. In combination, a telephone line having a telephone subscribers sub-set including a service telephone receiver with a pair of magnetic poles, an electromagnet mounted in inductive relation with said poles, a signal generator, means to pass a steady polarizing current through said electromagnet and to energize said magnet in accordance with the signals from said signal generator whereby said signals are impressed on the telephone line for transmission thereover.

19. In combination according to claim 18,.in which the means to polarize saidA electromagnet includes a polarizing battery and a reversing switch which is connected between the signal generator andthe said electromagnet.

20. In a signaling system, means to couple, a signal generator to a telephone line comprising a service telephone receiver .having a magnet and sound reproducing diaphragm, an electromagnet mounted in spaced relation to said diaphragm and adapted to be energized by signal currents to be transmitted to the line by electromagnetic induction from said electromagnet to the magnet in the receiver and thence to the telephone line, a housing for said electromagnet and forming with said receiver an acoustic chamber having it isbeing used tc couple the transmitted signals system which includes a pair of magnets in cirto the telephone line. cuit with said device, polepieces for said mag- 21. In s device of the characterdescribed, an nets shaped to ttheopening in a. receiver cap, audio frequency device, and a telephonesystem and means for securing the irst mentioned including telephone receivers; means to connect means to a telephone receiver. Y 5

said audio frequency device to said telephone AUSTIN G. OOQLEY.

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