US2047863A - Telecommunications system - Google Patents

Description

'Filed Feb. 26,1936 15 sheets-sheet 1 mm1-ALS( DED( IN VENT OR.

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' ATTORNEY.

W. G. H. FINCH TELECOMMUNICATIONS SYSTEM July 14, l1936.

1:5 sheets-sheet' InI Filed Feb. ze, 195e BY. Z

ATTORNEY w. G. H.l FlNcH TELECOMMUNICATONS SYSTEM 6 3 9 1 4., 1 lv... luA .J

Filed Feb. 26, 1956 13 Sheets-Sheet 3 mooY w vw. n R m D R me R T YCM A NN C. mw. r mM. m ww n. mw u R A T L L A R E v o .E

FREQUENCY-CYCLES yPER SECO ND COMPENSATION NETWORK" cHARAcTEmsnc FREQUENCY CYCLES PER SECQND Fig-4 IN VE NTOR. Zlfdlzanw'wclz ATTORNEY.

.lilly 14, 1936. l w` Q H. |=|NH 2,047,863

n `TELEclvuvlUNICATIONS SYSTEM Filed Feb. 26, 1936 l5 Sheets-Sheet 4 OVERALL TRANSMISSION CHARACTERSTIC COMPENSATED CARRIER Noi CARVER NO-Z 1 l l 0 25 400 1000 2000 3000 4000 5000 l FREQUENCY-CYCLES PER SECOND l llg: 5

I 5 ZZ l I y ATTORNEY.

July 14, 1936. w. G. H. FlNcH TELECOMMUNICATIONS S'YSTEM 1 3 Sheets-Sheet v5 COMPENSATION NETWORK Filed Feb. 26, 1936 PHONE BOX Aumo

AMPLu-lez Pigna.

- INVENTR. Williawj'nck ATTORNEY.

LJuly 14, 1936. f w` G. H. FlNcH 4 v 2,047,863L y TELECOMMUNIGATIoN SYSTEM Filed Feb. 26,1936 13 sheets-sheet e Aunlb AMPLlFlEz Y ATTORNEY.

W. G. H. FINCH TELECOMMUNICATIONS lSYSTEM July 14, 1936.

Filedfeb., 2s, 1956 v13 Smets-sheet a vAnf? l J l INVENTOR. 'lllzaw J'a/'vc BY i 1 ATTORNEY.

July 14, 1936. W, Q H FlNCH 2,047,863

TELECOMMUNICATIONS SYSTEM ATTORNEY.

y y July 14, 1936.v

' W. G. H. FINCH July l14, 1936 w. G. H. FlNci-l '2,047,863A l TELECOMMUNICATIONS SYSTEM 13 Sheets-Sheet. 11

Filed Feb. 26, 1936 \\\\\\\\\\N ...Y .Il

` INVENTOR. lillamrjf'ncll ATTORNEY.

' My 14,1936. w. G. Hmm y 2,041,863

TELECOMMUNICAT IONS SYSTEM Filed Feb'. 2e, 193s -13 sheetsfsheet 12 Il f f5 425 i Y 0 er QD 41a @D W4 451 15 July 14, 1936. w. G. H. FlNcH 2,047,863

TELECOMMUNICATIONS SYSTEM Filed Feb. 25, 1936 13 Sheets-Sheet 13 I INVENTOR.

WzZIz'an/{Qj'm 45 ATTORNEY.

it has been proposed to use telephone lines which` Patented pJuly 14, 1936 1 UNITED STATES PATENT .OFFICE i mmcormuiros'rms SYSTEM l I WillianrG. E. FincL'New York, N. I

1l Claims.

My invention relates to telecommunications systems and more particularly relates to novel apparatus for and methods of transmission oi pictures to remote points.

The widest us'e which telepicture systems today enjoy is Vin connection with vnewspaper service where pictures of importantl news events are transmitted from or near its source ,to newspaper oilices for publication. For such use, it is hig'hly desirable that the picture be transmitted #as near to the scene as practicable. Heretofore,

are usually available at almost any place for the transmission of pictures. inasmuch as the tele-v 'z phone company, however, generally does not persounds which in turn were impinged. on the usual telephone microphone.

. Although the acoustic method of inducing picture signals into the telephone line has still been. proposed as recently as within the past few years.

crophone ordinarily' used in telephone systems.-

yAlthough for the transmission ot speech, poor frequency characteristics are not material, as the ear tends to correct for audible distortions, they are serious in connection with telepicture systems where distortion would be visibly evident on the radio transmitting stations for the purpose of received picture. Y

I have discovered a novel electric coupling to the telephone lines which has alinearfrequency characteristic with respect tothe signals transmitted thereby. Specically, my system contemplates a novel method of inductively inducing transmitter by a novel portable member whichv picture signals into' the telephone linev at the maybe applied to any telephone subscriber station call box.

, The transmission of low frequencies,` for example, frequencies 'be1ow'25 cycles, is greatly attenuated in present telephone systems. Colnmunication requiring signals below cycles may accordingly not be directly transmitted thereby.

(ci. ris-4)- f By modulatin'gan audio freque'ncy carrier wave withsuch signals, they may then be readily transmitted over the telephone system. Theoriginal telecommunicationssignalsare th'en obtained by'demodulation at the receiver.' Thetems, such'audio frequency carrier operation is,

preferable. l

By 'establishing aV linear'wide frequency band transmission characteristic, for example, linear from 25 cycles to 5000'cycles, over a telephone line, it is possible to transmit two independent telecommunications' signals utilizing `two independent 'audio frequency carrier waves. Simultaneous speech and telegraph or printing telegraph and telepicture transmission over a single telephone channel accordingly practical r With-A out physical connection thereto, according to my present invention. Y f

Among the advantages other than the well knowneconomic advantages, of utilizing a telephone system for telecommunications which my novel couplingmeans makes available, is the utilization-oi -a portable transmitter.- A'news-` paperl reporter, for example, provided with my novel coupling arrangement may be provided 4with a portable transmitter which he can employ at any telephone station for transmitting to hisv main omce a picture which has immediate news value.

other than'to utilize it as any subscriber when he lifts the phone off the hook.

In a further modiiication of my'invention, I contemplate transmitting the signals ofthe port- In doing so, he will in no way interfere with the normal operations of the telephone lineA able transmitter induced into the telephone line h to the nearest ofa number of strategically placed 'either simultaneous or subsequent transmission of the picture signals from such station. f arrangement would Vnot only reduce the telephone costs but would also provide quicker service for national coverage.

In a still further modication of my This' invention,

contemplate a portable transmitter which radiates switching arrangement be-immediately converted 'radio hook-up may simultaneously provide the picture at each oi these radio stations.

-Moreover such. a portableA Aradio telepicture tron unitmay', by the provision of simple for electrically .inducing-picture signals into the.

' telephone. line in the type of telephone coupling system described u. Bothin the case oi the modulated carrier signais over the telephone lines and'in the case or the radio transmission i= 2b well knownfinthe for automatic signal level con suring a properly received telepicture.

It is accordingly ari-object 'oi' myfi'nvex'ition to provideV novel methods of and means for electrically coupling to public telephone systems for the transmission and reception oi signals between re- .mote points.

Another object oi' my invention is. to provide novel methods 't and means for transmitting pictures over a telephone system.

. A further objectof my invention is to provide novel methods of and means for transmitting telecommunications signals across telephone lin, byv

modulating an audio irequencycarrier wave and electrically inducing the resulting Signals into a telephone system.

Still a further object of my invention is to providey novel methods of and means vfor transmitting pictures over -a telephone line utilizing an audiovfrequency. carrier wave whichis .elec- Another object of my invention is to linearly ltransmit two or more `independent or interdependvent telecommunications signals over a single telephone line without connectionthreto.

A further object ci my invention is to provide a novel system for the oi telepicture signals-from a portable transmitter by electrical subsequent retransmission thereby to other re'- coupling to a local telephone line to the nearest-ot a group of radio transmitters for simultaneous or ceiving stations. Y

Still a further object of my invention is to provide a novel system' of telepicture whereby a portable radiov transmitter radiates the telepicture signals to one or a group of radio transmitters for transmission.

In the transmission of pictures Vto remote points itis essential that the receiver picture drumbe in simultaneous or subsequent -rephase synchronism with the transmitter drum.; Many attempts have been made to attain such phase synchronization.V It is extremely desirable toDrQvide a positive driving connection between the motor'and the revolving drum to avoid any deleterious eiiects due tofrlction coupling. In'

system for connecting'and disconnecting the positive driving connection between the driving motor compensate'forany-vari- :ations-.mths 1x1- o 2,041,863 the pormue'mdio meer neeamc be ,tomaintainphssesynchronization Ininyprw' ent inventionI utilize an over-running orlpositive clutch with means responsive to the synchronizing signals i'or maintaining thedrumin phase synchronism. In one embodiment I revolve the receiving drum at a slightly higher rate than the transmitter drum, in the ratio of 101 to 100. so as to establish the synchronizing pulse at s predetermined portion oi' the receiving drum, which portion will accordingly always be in position due to the increased'speed ratio, to receive the synchronzing impulse. Y l Y To .overcome the effects of 'rotational inertia displacement-'dueto accelerating or decelerating z. fomesandrprompuyauwmauuy com- 20 displacements.

A further' object otmy present invention is to provide a novel telepicture synchronizing system utilizing an overrunning or positive clutch at the 2 receiving station.

Y Still a Vfurther object of m'yinvention is to pro- A vide a mechanical exible coupling in the positive drive for a revolving drum, which automatically- Y compensates for anymomentary phase displacement due-to acceleration or deceleration forces.

y Another object oi' my invention is to provide a novel'methodof and means .for rapidv removal or insertion of the picture drum in a telepicture apparatus.

Still another object of my'invention is to provide a novel method of and meansy for motivating the scanning mechanism.

vAnother object .of my invention is to provide Figure 2 is a schematic illustration of a prel i'erred embodiment for lectromagnetically in.

ducing and receiving telecommunications signals o over a telephone system.

Figure 3 is` a typical over-al1 4'transmission characteristic curvefor an uncompensated electromagnetic transmission coupling system according to Figure 2.

Figure 4 is a -transmission characteristic of a preferred compensation network for use in conjunction with the vsystem of Figure 2.

lFigure 5 `is an over-all transmission characteristic for a compensated condition of the telecommunications transmission system according to Figure 2.

.Figure 6 is a .cross-sectional illustration. oi' preferred clamping means for rigidly securing a solenoid on the telephone box near the induction coil.

Figure 'uis'a modicationpof the electromagy netic coupling system of Figure. 2.

Figures t, 9, and 10 are illustrations of modipicture transmitter.

acariens-for eiedirostaucinduciioii or telecom;

munications signals into a telephone SYStem' acpicture drum showing details of the iilm clamping mechanism.

Figure 17 is a perspective view showing a set of nlm clamps in detail.

. erator.

1- signals of transmitter I in a well-known man-i Figure 18 is a schematic diagram of a. preferred telepicture receiver. Y j

Figure 19 is a plan view of the telepicture receiver .of my present invention.

Figure 19A is an enlarged side viewfof thereceiver synchronizing cam and switch.

Figure 20 is a cross-sectional view along 2li- 20 of Figure 19. Y

Figure 21 is a cross-sectional view along l2 I 2 I of Figure 19 thru the receiver drum and-drive.

Figures 22, 23, and'24 are cross-sectional views thru Figure 21', showing details of the clutch mechanism.

Figure 25 is a cross-sectional viewalong 25-25 of Figure 21 showing a'p'artially enlarged plan view of the drive mechanism .and clutch trip levers. l

Figure 26 is a perspective disassembled view of the clutch mechanism. v

Figure 27. is a cross-sectional view along2'I-21 of Figure 24 illustrating a fragmentary detail of a clutch roller.

Figure 28 is 'a perspective view illustrating details of the v,drum tail-stock supporting mechaa nism.

Figure `29 is a plan view of the worm-lock and cam lever mechanism.

Figure 30 is a cross-sectional view along 30 30 'of Figure 29. y i

Figure'31 is a plan view of the worm-lock and cam lever mechanism in open position. Figure 32 is a modification of the synchronizing magnet and lever mechanism corresponding to Figure 23. l Y

. Figure 33 is a cross-sectional view along 33 33 `of Figure 32.

Figure 34 is a plan viewtiif a modication for the carriage supporting mechanism.

Figure 35 is a cross-sectional view along 35-35' Y of Figure 34 illustratingltl'ie V slide arrangement. Telecommunitatiofns system Figure 1 is a schemic illustration of the telecommunications systein according to my invenltion. Transmitter I maybe a telegraph, -printingtelegraph,y speech or telepicture signal' gen- The audio frequency generator Ia isv modulated by the generated telecommunications;

ner, to provide an audio frequency carrier fori' .the signals to be transmitted. The output the transmitter I is connected to an audio frequency amplifier 2 by connection leads 3 4. The

my preferred vtelethe type of telecommunications transmitter I` used. For example, if a picture is to be transmitted by transmitter I,` translator II. will be a telepicture receiver designed'to translate the telepicture signals in accordance with the picture being transmitted. The audio amplifier' output leads II-'|5 connect the output of amplier I0 to the translator I I. 4In some applications it mayV be necessary to demodulate the signals so as to 'separate thev generated transmitter I signals 4from the audio frequency carrier of 'Ia. Such a demodulator is wellknown in the art,and is included in the translator II,- of Kmy schematic illustration.

The telecommunications system of Figure 1 will operate across a radio channel I6 when the .transmitter switch 'l is'closed on contact Il, and the corresponding receiver switch I2 is closed on contact I6. Theputput of audio amplifier 2 is introduced by leads .2D-2i to the radio frequency modulator 22. The. radio frequency-oscillator 23 provides the radio frequency carrier for the radio frequency signals to be transmitted. The output of] modulator 22 is connected to radio frequency amplifier 24. The radio frequency signais are radiated by antenna 25 connected to the output of radio frequency amplifier 24. Y At -the receiving station, antenna 26 is im pressed by signals from transmitter antenna 25 across the radio channelv I6. A radio frequency receiver -21 amplies signals from antenna 26. The radio frequency receiver 21 may be tuned radio frequencyamplifier, or a superheterodyne receiver. The output ofthe receiver 21 is con -neoted to a demodulator or detector 28 for demodulating radio frequency signals. Thev audio frequency signals corresponding to those at the' vaudio amplifier 2 are accordingly produced at the output 30-3I of the detector 28. The receiving switch I2 being closed on contact I8, audio munications signals isschematically illustratedby the electrical induction means, into a public telephone system, forminga primary object of my present invention. The transmitter switch I is closed on contact 32 and the corresponding receiving switch I2 is closed on contact 33. The output of audio amplifier 2 is impressed upon leads 34-35 through an optional compensating network 36, the outputleads 31-38 of hich are connected to solenoid 40. Solenoid 40 s placed adjacent the ordinary' local telephone hox-l 4I associated with theA telephone 42 43 at the ansmitting4 station.` indication coil 44, shown in dotted lines within the phone box 4I, isassociated with each telephone unit 42 -43. The signals to be transmitted produce a magnetic field about solenoid 4I).

This magnetic neid is induced iii the induction '75 phone stations 42---43 andlS-SB is establishedthrough an automatic telephone vconnection or,

45-46 as will be hereinaftervdescribed in more detail. The phone box I1 of the receiving stacoil 48 tion contains the corresponding induction of the receivingtelephone 49- 50.

When the telephone circuit between `the teleby a telephone operator, the telecommunications 4signals induced into induction coil 44 by .transmitter solenoid 4i] are received bythe receiver- The signals through induc' induction coil 48. tion coil l8- produce a corresponding magnetic ileld about the induction coil, and the. receiver solenoid 5I placed in this magnetic eld has induced thereinv a voltage corresponding Ato the transmitted signals. The receiver solenoid 5I is connected to the audio ampliner Il Aby leads L B2-53 across contact 33 and through switch I2.

The signals amplified by audio ampliiler Ill ac-A cordingly correspond to those at the transmitter amplier 2. The amplied signals are' intro- `duced to the translator I I by leads II-IS.

i The electromagnetic inducingj' methodl for transmitting and receiving telecommunicationssignals provides a practical system for utilizing solenoid 40 for inducing the telepicture existing telephone communication systems for 'transmitting without interconnection thereoffl The signals 'are transmitted and received electromagnetically, or, as in a hereinafter described modication, electrostatically across the Itelephone lines 45-'46. Transmission characteristics of such .a systemmay be madeA substantially linear with frequency as will be hereinafter further explained. -l

An important feature tions system according to my present invention is the use of a portable transmitter for eillcien'tly relaying a message or picture toja centralofnce. FigurelA is a. schematic illustration of a modification of ljigure 1,' illustrating such a 'Y transmitter system. The portable transmitter is designed to be rugged and light in weightA so that it may bemanually transported, and operated from an automobile, airplane, ship, or the like. -The portable transmitter should prefer;

ably be operable from storage batteries and from standard power lighting circuits lective switching. Y

For newspaper work it is very desirable to have a telepicture transmitter which an operator or reporter' carries to the scene where pictures are to be talren.l The developed picture is inserted. into the telepictur'e transmitter, and the corresponding 'picture signals are transmittedto the nearest newspaper station in a manner to beV described. A newspaper service may have a plurality of lradio transmitter and receiver' stations positioned at stategic locations over the nation. These radio stations are equipped to 1e4 ceive and transmit telepicture signals. The portable telepictur'e -transmitter I is connectible to either a portable short wave transmitter 9, or to a Signals across the telephone lines lS-JS. V-The operator, 4of the -portable transmitter; I'

may, for example, transmit a picture of immediatev news value t'o his lnearest newspaper oilice from a telephone subscriber station.- He phones from his stationH-JS to the station 43-50 of 'his Umea The switch 1' of the transmitter -is closedV across contact 372 so 'that the telepicturesignals are impre'ssedrupon solenoid 40. -The solenoid 40 is placedin operative relation with the induction coil Il in phone box II at the local subscriber A Y 9,047,363 `coil 44 for transmission' along the telephone'lines l .The induction coil B in the phone box AIl will can? the telepicture signals and Ielettromagnetiwith receivedpicture signals over antenna 39.. In many instances a telephone subscriber staof the telecommunica- A lwith 'respect to the outputl'f-A of transmitter I' will accordingly be inductively induced across telephone circuit 45e-I6 to the newspaper oiiice telephonestation cally impress them upon the pick-up solenoid 5| on-contact 33' so that .the'signals `picked-up by solenoid 5I are impressed upon audio ampliiier ID' through leads'iZ-Bl The telepicture signals are then impressed upon the ,lepicture 'translator Il' which'reproduces the picture being transmitted by 'the transmitter I'.'

It may be-desirable to simultaneously re'radiate 'the picture signals -being radiated bythe portable 'transmitter I' by a'powerful radio. station trans,-

station |244# The telepicture from the The switch I2' at the newspaper ofllce-is closed mitte: for reception at distant newspaper vreceiving stations. The output of the audio amplifier I Il is connected to the relatively powerful radio frequency transmitter 29 which radiates a radio frequency carrierwave modulated in accordance tion may not'be available 'to the operator and accordingly I provide a modic'ation fortransmitting picture signals to a newspaper office by a portable radio transmitter. .Theuseful range of such a transmitter be several/hundred miles so that a corresponding short wave receiver at the'newspaper o illce may properly receive the picture signals. The radio picture relaying modi- -cation is illustrated in Figure 1A in conjuncand the newspaper'short wave receiver I9.l

' The transmitter switch 'I' is closedupon contion with the portable` short wave transmitter! mitter I' .are conducted'to the input 21V-2l of the portable short'wavc transmitter! for'modulating its carrlerwave which is radiated by -antenna 25'. Itis tobe understood that the port` able short wave transmitter 9` is designed along the linesof the portable telepiotm'e transmitter type'of power supply,` weight, and so forth.

'I'he modulated short wave carrier transmitted y' along radio. channel -i8 is received at the vnews-A paper omce short wave receiver I9 by. antenna 262 The short wave receiver i9 should be dei` fm/ay be locally reproduced by translator] I', 'and may also be simultaneously rfa-.transmitted by the powerful station radio-frequency transmitter 2 9 over antenna 39; It is to be Aunderstood* that the transmission of pictures from the radio station 2l may occur simultaneously with the recep-v tion oi the picture from the ileld'portable trans-A mitterA I' as herein described, or may' be subse quently transmitted from the reproduced'picture as .obtained from the telepicture translator .I I'. The use of simultaneous re-radiation over a more powerful radio-frequency carrier-wave of picture signals immediate news value as received 75x from a field portable telepicture transmitter makes possible a cheap, eflicient and rapid national coverage of the particular pictureto all the newpaper receiving oilices strategically located over the country,

Figure 2 is a schematic illustration of the telephone system 43-50 in operative relation, including the connections between transmitter microphone 54 and ear-piece 55 to the phone box 4l by leads 56, 51, and 58, the connections to the receiver phone box 41 across lines 45-45; and the connections to the receiver microphone 60 which the induction coils 44 and 48 are generally connected in telephone systems. The particular connections of the induction coils in the system are not important, since in every case the effects described in conjunction with the illustrated connections will be eiected. The dashed portion 45-4E of the telephone line 45-46 represent all the auxiliary apparatus necessary to maintain the telephone stations 43 and 50 in operative relation. Included between the stations 43 and 50, as is well known, are repeating stations, batteries, ringers, etc.

At the transmitter station, the microphone 54 is connected lto line 45 by lead 56.. The microphone 54 circuit is completed by lead 51 to the line 46, with the primary 65 of induction coil 44 connected in series therebetween. As is well known, the carbon microphone 54 requires a. direct current energization which is supplied through the last mentioned series circuit arrangement. The telephone .earpiece 55 is coupled in this manner to the telephone lines to eliminate the passage of direct current therethrough. The earphone 55 is connected to the secondary 65 of the induction coil 44 by lead 58. The opposite side of the secondary GE is connected to line 45 ln series with the condenser G1. The primary -BB and secondary 69 of the receiver induction coil 4B, together with condenser 10 are connected at the receiver microphone 60 and earpiece 6l in a manner similar to that at the transmitter 43 herein described.

The transmitter solenoid 40 is placed adjacent to the induction coil 44 to provide for -optimum induction of the telecommunications signals therein. I have found that when the axis 1I of solenoid 40 coincides with the axis of the induction coil 44 maximum signal energy transfer 'is had. The solenoid 40 is placed as close as practicable to the one end of induction coil 44 to insure maximum signal induction. The phone box 4I'is enclosed by a sheet metal cover 12 indicated in` dotted lines in Fig., 2. In a. practical performance of the coupling arrangement according to my invention therefore, one side of the solenoid 40 is juxtaposed Vwith the metal cover 12 at a region so that its axis coincideswith the induction coil 44 axis, or is as close-thereto as physical conditions permit.

(The region qi' optimum coupling is determined in'the following manner. The audio frequency carrier or. tone from generator la: is introduced to the line through amplifier 2 (Fig. 1) and impressed upon solenoid 40 as hereinabove described. This operation is preliminary to the transmission of the telecommunication signals for optimum adjustments of lthe transmitting and receiving apparatus. Telephonie communications' between stations 43 and 50' areV established through automatic dialing or by telephone operators. The solenoid 40 is placed close to one end and earphone GI by leads 62, 63, and 64. I have ofthe induction coil 44. The tone or audio i'requency carrier may beheard locally by the transmitter operator through earpiece 55. The position of solenoid 40 is adjusted on box 4l with respect to induction coil A44, so that a tone of maximum intensity is heard by the operator in earpiece 55. A- rapid and simple determination/ of the optimum coupling position is had in this manner.

The solenoid I at the receiving station is positioned for a maximum signal transfer or pickup with respect to induction coil 58. This position is determined in a manner similar to that described at the transmitter, namely the axis of solenoid 5I preferably coincides with the axis of induction coilv 48, and one end of solenoid 5| is juxtaposed on the metal casing 15 of the receiver phone box 41. .The receiving coil 5I is experimentally adjusted to this optimum position by listening to the tone in earpiece 6I and is rigidly clamped inplace asherein described.v Such adjustment is preferably made during the transmission of a constant amplitude carrier from the transmitter. The optimum position may more accurately be indicated by an output meter (not shown)l connected at the audio ampliiier I0 as will be evident to those skilled in the art.

Figure 3 is a graphical representation of a typical overall transmission characteristic which I have obtained between a transmission and receiving station, corresponding to signals at the transmitter I and translator I I of Fig. l. The curve 15 was plotted with frequency, in cycles per second, and with E, representing the received voltage at thel translator Il. At the transmitting station 4 signals of constant amplitude were in- .troduced to the audio amplifier 2 .at frequencies extending Yfrom 25 cycles to 5000 cycles and beyond. Curve 16 demonstrates the' substantial lineararity of this method of transmission from 900 cycles to 5000 cycles as indicated by the coraswill be understood by those skilled in the art.V

If intermediate equipment between the telephone stations 43 and 50 introduce a-cut-off frequency below 5000 cycles to the transmission characteristic, the audio frequency carrier may accordingly be adjusted so that theV sidebands may be uniformly transmitted. It is also practical to transmit a single sideband upon an audio frequencyv carrier, and utilize the linear transmission characteristic on single side band audio frequency carrier transmission as is well knownin the art. Another important feature of my invention resides in extendingthe linear characteristic transmission relation frorm 25 cycles, by eliminating.

the eil'ec't of the peak 11 by inserting a compensation network 35 between the transmitter solenoid .40 and the transmitter amplifier 2 output. The purpose of this network is to attenuate sig- Y, nais between 25 cycles and'900 cycles inversely proportional tothe peaked relation 11 of Fig. 3.

' In Fig. 2 I illustrate a simple form of compensation network for this purpose; An inductance 36a and capacitance 35h are connected in series across to 5000 cycles and above.

' printing telegraplly.'

quenqy it is tuned to, namely, 400 cycles. to cor-v respond to the peak of the -system herein described.

induction coupling Fig. 4 illustrates the transmission characteristic 11 of the compensation network Il. It will be'seen that minimum trn occurs at 400 cycles. The proportion of decrease is made equal to the-ratio of the peak 11 to the plateau 6 of Fig. 3.

Fig. 5 represents the overall ion characteristic corresponding to Fig. 3 with the compensation network Il connected as'iilustrated in Fig. 2. The super position of compensation network characteristic 1B of Fig. 4, upon the transmission of characteristic 11-'ll of Fig. 3, produces the transmission characteristic Il oi Fig. 5 which is substantially linear from 25 cycles It is accordingly evident that the electrical induction method for transmitting audio frequency signals according to my present invention, may be attained with substantially no amplitude diselimination with respect to the frequency. I have y alsofcund that the noise level oi' this transmission system is negligible as compared tol the telecommunications signalstrength, resulting in an excellent signal to noise ratio.

The wide channel afforded by my present invention with no physical connection to telephoney lines, may be utilized with more than one carrier wave transmission. Accordingly, in Fig. 5 I have illustrated two audio frequency carriers, namely carrier No. 1 and carrier No. 2. Carrier No. 1 may, forexample, be a tone of 1500 cycles, and carrier No. 2, a. tone of 3500 cycles. The ilat frequency characteristic B0 of the side-bands of the carriers Nos. l, and 2, repre'- senting independent or interdependent telecom- .munications signals to be transmitted without' any signal discrimination. 4

The utilization of two carriers as herein described may be for simultaneous telegraphy and transmission of two independent. similar systems, forv example, simultaneously transmitted. lAnother modification for .utilizing the wide audio `i'requency channel with two independent-audio frequency carriers is to. simultaneously transmit adjacent lines of'a picture being scanned with two scanners oppositely disposed uponthe picture drum, so as to cut in half the time forrtransmitting a single picture. Such a system requires each of the audio frequency carriers to be -associsted with one'of the corresponding `alternate scanning lines ofi-the picture being transmittedpto actuate corresponding alternate telepicture translat ors for simultaneouslyreproducing the predetermined 'alternate picture lines at the. receiver.

` Itis to be understood thatsuitableillter means Vare necessary at the receiving station for prop- 'erly directing the two independent audio frequency carriers to their predetermined respective translators.

' Another modification resides in transmitting Va. plurality of tones suitably spaced along the audio frequency transmission channel for actuating a printing telegraph apparatus. A pluralthe system permits or telegraphy and speech.. or telepicture and speech, or the simultaneous two facsimile pictures :being ,omsoa mission of the impulses of the code combinations.

' Another modiilcatlon is to utilize 'the peaked portion 11 of the characteristic illustrated in Fig. 3 for transmitting synchronizing impulses. A four hundred cycle note corresponding to the frequency of the peak 11 is intermittently impressed upon the transmission line for synchronizing the v telecommunications receiver and transmitter. For example, in a telepicture system, a vsynchronizing impulse is sent at the beginning or end of each line being scanned for maintaining synchronism of the revolving drums. The synchronizing impulse is generally of increased'intensity for operating a marginal synchronizing relay. In this modiiication, however, the synchronizing impulse at the transmitter need only ^be of normal intensity. The uncompensatedinduction transmission characteristic willv impress the synchronizing note of 400 cycles at an inicreased relatlveamplitude to operate the marginal synchronizing relay. I

Fig6 is a cross-sectional illustration of a clamp for rigidly attaching the transmitter solenoid 40 upon the phone box Il'. The induction coil M is supported `within the phone box I I by wooden uprights Il. The core of the induction coil Il comprises laminated metal strips l2 which generally project into the wooden uprights BI. One end of the bracket is attached to'the solenoid l0 by screws 84. A threaded rod I5 passes through a hole at the opposite end of the bracket noid I0 is rigidly fastened in position upon the phone. box 4I.

is preferably positioned in axial relation with the iron core! Il of induction coil u in a manner has-a similar arrangement for fastening to the receiving phone-box 41. In my preferred 4embodiment .the receiver solenoid 5 I` has an air core. VFig. 'l is a modification of the electromagnetic The iron core 13 of solenoid lili hereinabove described. The receiver' solenoid 5| inducing arrangement illustrated in Fig. 2. Two 7 solenoids '4l and a are arranged at opposite ends of the induction coil 'so that the induc- A greater etliciencyof electrical induction is had tloncoildlhassignalsinducedatopposite ends. 60,'-

by such an arrangement. The solenoids Il and laminated 'iron coresl 1i and 1Ia,re' zspectively. A'common'iron yoke Il supportathe :ciencias imposition ,the phone box u. 65..;

of' the yo'ke' may beconstructed similar to that of bracket, l1 `of Fig. 6 for properly will 4l a'n'd a -in the optimum position' upon the phone box casing 1l.

It to be understood 'thatthe polar-ities of 70- the solenoids Il and Ila are arranged to induce v the electricaly dgnalr into induction coil Il' in vadditive relation. Atthe receiving station phone box I1, two 'pick-up solenoids II and lla yare Dit sides of -the induction Ik -accesos and lila are connected to the receiving apparatus through leads 52 and 53 through contact 33 of s ment of twofoppositely disposed pick-up solenoids providesat least twice the signal pick-up as compared to the use of a'single solenoid. .N The energy levels of the signals induced into' the telephone system at Vthe transmitter indue-fA tion coil 44A 1s limited bythe magneticsaturation lof the iron core 82 induction coil. Toavoid signal distortion due to overloading of the telephone lines, the maximum .signal intensity transmitted is kept below the predetermined distorting intensity. Interference due to "cross-tails" is also minimized in this manner. The intensity of the telecommunications signals induced into the telephone system scco'rding to my invention is. comparable to the peak voice signal intensity transmitted by the telephone line.4 Such signal level tion is feasible for quality intercommunication.

is transmitted with an extremely favorable signal to noise ratio so that subsequent amplifica- 'Although I have described preferred electromagnetic coupling methods which provide the most efcient and best transmission characteristic for transmitting telecommunications signals across a telephone system without physical connection thereto, other electrical couplingA methods are feasible. For example'. the signals may be induced into the telephone earpiece windings or other parts of lthe local telephone station. However, the concentration of the winding turns at the induction coil provides the most practical point for electromagnetically inducing the signals. Preferred methods of electrostatic induction of telecommunications signals into atelephone system is illustrated in Figs. 8, 9, and i0. Eig. 8 illustrates a metallic plate Si connected to one terminal of the output of the audio frequency amplier 2 of the telecommunications signals to be transmitted. The audio frequency amplier, as hereinabove described, is connected to the switch l which is closed on contact 12 for connecting the output of amplifier 2 to the leads 32 and 35 connected to theinput of the compensation network 35". The characteristic of the compensation network 3S is designed to compensate for the frequency discrimination presented by the particular electrostatic induction method usted according to principles'well known in the as The output ci audio frequency ampliiier 2 is preferably of a high voltage to place the plate 9G et a high electrostatic potential with respect to ground.v The lead 38 from the output of compensaticn network 38' is connectedto plate '86: theother lead 3l beingconnectcd'to ground. Fi. 8 shows a hand set desk telephone positioned upon the plate in operative condition.. the hand set 43 being removed from its' position on the telephone stand l2. An automatic telephone dial Il is shown inthe telephone base l2. ATelephone cable 92 corresponding to leads 58, 51; and 58 of Fig. 2 connects the telephone instrument 42-43 to the phone bo`x il. Leads 45 and 48 of the output of phone boxli connect the instrument to the remainder of the telephone system' as described hereinabove. The metallic plate 80 is isolated from ground. The telecommunications signals impressed upon-the audio ampliner 2, as described in connection with Eig. l.. are electrostatically induced tothe telephone system,

the telephone base 42 and hand set, no physical interconnection beingnecessary. The signals are transmitted over lines 55-56 to the receiving station to be received as. hereinabove described.

Figure 9 is apractical embodiment of 'a transmitter using the electrostatic induction principle -of Fig. 8. A transmitter cabinet B3 housing a nal generatonior example, a portable telepicture or facsimile transmitter. contains a metallic plate '-34 set into the insulation cover 95 of the cabinet 10 I3. Cover 95 may, for exampl ebe wood, hard rubber or other insulation material. The telephone base l2 is placed upon the metallic plate Si. It is also feasible to provideroom for the hand set 43 on plate 84, although it is not necessary. Plate Sl corresponds toplate of' Fig.) 8 and is connected to the lead 38 o f the electrical circuit.

Figure 10 is another embodimentfor electro ,statically inducing telecommunications signals into the telephone system. The portable tele- 20 communications transmitter 9S contains a compartment 81 at one side thereof intoV whichthe telephone l2 may be inserted. Compartment Sl is lined with Aa sheet metal 98 such as copper, to

. provide the electrostatic inducing surface corre- 25 spending to plate 90 of Figure 8. The lining 93 is insulated froml the reminder of the receiver, and the material 99 to which it. is fastened is wood or other insulation. The embodiment of Fig. '10 provides electrostatic inductionby sur- 3o rounding the telephone apparatus; The hand set 43 may optionally be inserted in compartmentl.

The electrical inducing methods hereinbefore described make it possible for a portable telecommunicatons transmitter, for example, a telepic- 35 ture transmitter, to transmita picture which may have immediate news value from any telephone station to the"central newspaper plant by merely establishing a telephone connection between the A stations, verbally` establishing the conditions of the trnsmission, and proceeding to transmit the picture in a. manner already described. The tremendous commercial advantage, particularly to newspaper ofiices, of such an arrangement is selfevident. No permanent leasing of telephone lines between permaanent stations is required. Payment for the use of the line is according to the actual time taken in transmitting the picture instead of over a 24 hour period as is at present required.

By employing the two channel transmission method hereinabove described-in connection with Fig. 5, simultaneous printing telegraph and tel'epicture transmission may be carried on between the stations, so that the lnews story inconnection with the picture may be had. -A further method is to employ the frequency'renge from 25 cycles to 2000 cycles for an intelligible speech channel,

'in place of carrier No. 1- (of Fig. 5), and simulcused to -a point by a, lens system Inrupon the .A source of lightvv I lllLproduces picture. i@ be transmitted which is mounted du 'itA

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