US 420884 A
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Description (OCR text may contain errors)
"(NO MOdeL) 8 2 Sheets-sheet 1.
. E. J. P. MERCADIER.
- MULTIPLE TBLBGRAPHY.
180.420,884. Patented Peb. 4, 1890.
2 Sheets-Sheet 2.
E. J. P. MERGAIBR.
Patented Peb. 4, 1890.4
' UNITEDV STATES PATENT GFFICE.
' ERNEST JULES PIERRE MERCD'IEIL or' PARIS, FRANCE.
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.To all whom it may concern.- Be it known that I, ERNEsT J ULEs PIERRE MERCADIm, electrical engineer,a citizen ofA theRepublic of France, residing at Paris, France, have invented certain new and useful Improvements in and relating to Multiple Telegraphy, of which the following is a specifcation. I My invention has reference to a system 'of multiple telegraphy for which I have'obtained Letters 'Patent in France, No. 190,909, on May 30; 1888; in Belgium, No. 83,056, on August 28, 1888; in Great Britain, No.- 10,363, onVJuly 17, 1888, and in Germany, No. 49,213, on Au- The fundamental yfeature of my invention is based upon the fact that if upon a continuous current in a line a particular set of that particular rhythm of current-undulations, and to no other, and that if at the same time electrical undulations of different rhythms are superimposed upon the continuous current, yreceiving-instrumeuts construct'- l ed to respond ,each to one of those addedrhythmical undulations may be used for the reception of messages spelled out by the 'added undulations.l
Prior to my invention it has been attempted to superimpose upon a continuons current in.
a line .electrical pulsations4 oft dillerent 5 frhythmsand to receive th'e messages spelled -3 5 'out' by each: -setof impulses by suitable-fra ceivinglinstruments, each constructed'to yre- Y spend to one particular rhythm of pulsations only. For practical purposes this old system could not be used with advantage, for the rea-l son that the pulsationscomposing the sets of different rhythms the two sets were respectively designed would.
- not respond, while another receiving-'instrument, which perchance' was 'constructed'to re-'.
' spond to the new rhythnnaccidentally formed,
would receive the lmessage.V The message ,would thereforeeither notbereceivedat'all vducing such undulations is to -netic energy, would frequently blend,y constitutinga separate and distinct 'set of pulsations ,having "mode Inay'be stance whose 420,884, amusent-wy 4, 1seo.
I or would be received at a station where it was l not designed to go in a mutilated and unintelligible form. It has also been suggested that if inhplace of sharply-defined electrical pulsationselectrical undulations in which the' current' gradually gradually decreases are used no blending of the sets of dierent rhythms takes place and no confusion in the reception of the mes 6o occurs. The production ofrhythmical eltrical undulations superimposed upon a conltinuous constant current can be effected in a variety of ways.- The simplest mode for pro' sistance of a charged electric circuit b'y va# lriations. of contact or pressure cordance with rhythmical mechanical vibrations', and this mode, which, for the sake of lclearness of exposition,
scribed, but to which I make no claim herein, I shall hereinafter call the mi'crophonic mode 'of multiple telegraphy.
-Anotl1er'mod e of producing'the electricalundulations for my graphy, and the one which'I prefer, consists in varying the resistance of -an electric circuit by rhythmical pulsations of radiantenergy, and this method I shall hereinafter call the phyf By the.' term radiant energy, which -I largely employ -in this specification, I under-` A stand those-forms of energy which are currently understood to be lines inA all directions, and which are allcornprised-.or found in a ray ofordinary light. I
therefore do not wish to be understood to em 0r Ilfvllg-A 99 the propagation of which is notl bracey by that l'term either electrical at present understood. .n v,
1 It will be understood that according to the4 vparticular kinds of radiant energy the radioy phonic mode of operation will be either pho .95
tophonic or thermophonic, and' 'the' latter practiced. in two ways: first, by causingheat-rays to act directly upon `a subelectrical resistance is varied by the same, or to cause, primarily, vibrations by the rhythmi'cal impact of heatrays,` and then to vary'the electrical resistincreases and .equally l vary the re- -by and in ac I have fully de- 7o system of multiple tele- ,75'
iophonic mod eof multiple telegra- 8o propagated by'ethe- 85 real vibrations" from their source in radial mechanical roo '1o ent modes, without, however, confining 2, y y `inattesa.
reference is made to the accompanying drawings, in which I have shown suitable apparatus for practicing my invention in its diterself to the use ot the identical instrumentalities shown and described.
I have illustrated in Figure 1 a plan view,
partly in section, of a radiophonic transmitter, with the circuit-connections shown in diagram; in Figs. 2 and 2, a side elevation of the same, showing' also an auxiliary apparatus used as an acoustic speed-gage or tachom eter; in Fig. 3, a side elevation of a pre- 2 0 ferred form of selenium or other cell sensitive *to radiant energy; in Fig. 4, a modified form of the same, also in side elevation; in Fig. 5, "sa cross-section of a monotelephonic receiver; in Fig. 6,a diagrammaticview of two stations 2 5 equipped for practicing my process of multiple telegraphy by the radiophonic mode, some of the details being omitted for the sake of clearness; in Fig. 7, a vertical sectional view of a transmitter adapt-ed to operate by what 3o I have'v called the thermo-microphonic. mode; in Fig. 8, a diagrammatic view of the equipment of a station for the transmission' and reception of signals by themicrophonic mode, andin Fig. 9 a diagrammatic view of a system arranged for the transmission of signals photophonically.
Like numerals of reference indicate like -parts all throughout the drawings.
-Referring 110W more particularly to Fig. 8,
.4o. there are shown two station apparat-us 1 2 of a series of seven or twelve such apparatus, which are supposed to be located at each station. They are all constructed alike, each consisting of a tuning-fork rheotome mount- .4,5 ed upon a resonating-box, a microphone also mounted upon a box, an induction-coil, a telephonicreceiver, and a key.` Each tuning-fork 3 is tuned to a certain definite pitch corresponding to a tone of a diatonic or chromatic 5o scale, so that when there `re seven station apparatus a diatonic musi al scale will be represented by the seven tu ing-forks, and if.
twelve station apparatus'be used a chromatic scale will be represented. 5 5 Each tuning-fork is mounted with its stem 4, as usual, upon a resonator 5, and between' the prongs of the tuning-fork is mounted an Y `electro-magnet'(i, included in a local circuit 7, charged by a'battery S. One terminal of 6cr this circuit is formed by the adjustable contact-screw 9 and the other by an elasticallymounted platinum disk l0, carried by one of the prongs of the tuning-fork. This construction is well known in the art, and it '65 causes the tuning-forkto vibrate continuously in accordance with its inherent rate of vibration, and being mounted upon the ressociated will pass over the line and a series onator 5, the latter, re-enforcing the sound of the tuning-fork, vibrates in unison therewith.
The microphone 11, of any ordinaryor pre- 7o .ferred construction, is mounted upon the top plate of the resonator and is vibrated by the same, producing as many electrical undulat-ions in the circuit 12, in which it is included, as there are vibrations in the tuning-fork.
The microphone-circuit 12 is a local circuit, and is charged by a battery 13, and in the same circuit is included the primary coil of an vinductorium 14 and a key 15, which, for convenience of operation, will be 'constructed 8o like a Morse key.
It will now be understood that if the tuning-fork rheotome is at work and the circuit 12 is closed by the key 15 electrical undulatons of the same rhythm as that of the tuning-fork will bev produced in the microphonecircuit and alternating electrical undulations of the same rhythm will be produced by induction in the secondary of the inductorium, in the exterior circuit 10 of which is placed apeculiar telephone-receiver constructed to respond to electrical undulations of the rhythm of' the tuning-fork, and to no other, and which,for this reason, I call a monotelephone, the construction of which will hereinafter more fully appear.
I have so far described one station apparatus shown in Fig. 8; but the same description applies .-toall the station apparatus, which only differ from each other in the pitch of their tuning-forks and in the adjustment of their monotelephones, it being understood that each monotelephone responds only to electrical undulations of the rhythm of its corresponding tuning-fork.
, As stated above, at the station represented in Fig. 8 there are supposed to be either seven or twelve station apparatusof the kind described, each representing one tone of a diatonic or chromatic scale and the secondaries of the induction-coils with the monotelephones all in series, as shown, one end of which circuit may be grounded 'at 17, while the other is connected with the line which passes to a distant station, and is there connected with a series of station apparatus identical in all respects` with the apparatus at the home station.
The operation of the system thus far described will now be easily understood. In the normal condition of both stations the tuning-fork rheotomes are all atwork and the keys 15 are all open. The monotelephoncreceivers, therefore, will not be affected. It now at the one station one of the keys is closed and opened successively in the manner of Working Morse keys, a series of electrical undulations having the rhythm of the particular tuning-fork with which said keyis as- IOO 1 3o of sounds of different durations and of a pitch equal to that of the tuning-fork willbe heard in the home receiver associated' with that particular key, 'and will be heard in no will also actuate the monotelephone of thek rIO other receiver at the home station. :The series of electrical undulations thus produced with their tuning-forks and monotelephones notelephone.do respond, andno other.
one particular rhythm only will be affectedA .3o
.reason I have constructed 5.
rather high resistance,
tuned seriatim to the diatonic scale-do, re, mi, fa, sol, hc-and if the key of the apparatus do at one station is actuated, the moat 'the distant station will If, however, two or more keys at one lstation same time, the electrical undulations upon the line will have the characteristics of the rhythms of all the transmitters called into action, or, in otherwords, there will be electrical undulations of the rhythms of all the Atransmitters which are in operation at the and each monotelel same timevupon the line, phono at the distant station responding to by the characteristic of the electrical und ulationsdue to such rhythm, and by no other, so that seven or twelve messages can be transmitted at the same time over a single line, and can be received at lthe distant st -ation without confusion. A
The ordinary magneto-telephone receiver constructed. with a diaphragm having its edge or edges clamped has the peculiarity that it .will respond to all rates of vibration, and this it mustvdo in order to adapt it to the reception of articulatespeech or other complex sounds. Obviously a telephone .of this character cannot be used in my system of multiple telegraphy, for if. it'were used it would take'up and reproduce the messages from all station apparatus, whatever the rhythm of the same might be, 'and'no .single-message could be distinguished from the other. For this and use in my system telephone-receivers. responding each to one rhythm only,gand theseltelephones I call monote1ephones, one form of which I have illustrated in Fig. 5. l, v
An electro-magnet 18, havinga/ coil of is'mounted in asuitable casing 1 9, with its free active pole 2O slightly` projecting through a partition A21.
. Upon this partition are mounted three guides guides are equallyspaced, so that the sectors q 22 22 22, arranged radially on the partition, if the same is circular, and by preference the into which the circle is thusdivided are equal. Upon each guide isymounted a stud 23, adj ustable upon 'the guide, and if these v'studs are eachadjusted at' the same distancefrom the'center. of the partition they mark the corners of an equilateral triangle inscribed ina are operated at the- In Amy monotelephone I adjust the support- 23 so that when the diaphragm is ing-studs placed upon them they correspond to the -nodal line of the first harmonic of the diaphragm, and a diaphragm thus supported will perceptibly respond to a rhythm due to that first harmonic, and to no other. i am thus enabled to make a telephone responding to one particular sound only, and 'telephones of this or similar construction must be used in my system of multiple telegraphy.
The nodal line of the first harmonic of the diaphragm cannot be determined with absolute accuracy, and therefore, as a rule, the
-rst adjustment of the' studs 23 will not be perfect, and in order to compensate for this defect I use an adjusting-weight 25, which may be a short heavy cylinder 'of brass resting upon the diaphragm and connected on one side with a rubber or other elastic cord 2G and on the other with a thin wire or cord 27, both of which are fixed at their other ends to winding-pegs 28, and by turning the-latter one Way or the other the adj ustin g-weight 25 may be brought to any desired position upon the diaphragm, and by a proper adjustment of the same the defect of adjustment of the supporting-studs 23 may be neutralized and the diaphragm tuned to respond powerfully IOO to the first harmonic of its fundamental note.
In fact, the pitch of the diaphragm may be varied Within a 'major second by proper adjustment of the Weight 25, although such vio-A lent adjustments are not necessary in practice. Sound-conveying tubes 29 29, terminating in ear-pieces 30, are arranged to convey the sound from both sides of the diaphragm to the listener, who will preferably use both ear-pieces. v
If in plac'eof a circular diaphragm one of rectangular form is used, the supportingstuds 23 will beso adjusted that two of them will be on one of .the two nodal lines of the fundamental sound of the diaphragm, which are at about twenty-two one-hundredths'of thc whole length, measured from either end, and the other supporting-stud will be on the other of said nodal lines. A telephone thus constructed will respond to the rhythm of itsl fundamental' tone only. Monotelephones differently constructed may be used in my system, and I am therefore not -those herein described.
Instead of produciu g electrical und ulations on the line by the' react-ion of a tuning-fork con fined to -are in the same radius.
upon a microphone, I preferably produce them by the action of radiant energy upon a selenium cell or other device sensitive thereto, and one apparatus for producing electrical undulations in this manner is illustrated in Figs. 1, 2, and 3. Referring to these figures of drawings, there is shown a rotary disk 31, of some opaque material, or it may be made of glass and rendered opaque by pasting over 'it a sheet of card-board `or paper. '.lhis disk is mounted in suitable bearings '32,and is driven at a great and uniform speed by an electric motor 33, (see Fig. 2.) connected by a belt 34 with a pulley 35 upon the shaft 36 of the disk. In the disk y31 are formed a series of concentric holes, which from the center toward the periphery are marked in the drawings seriatim by the musical notations do re,mi, fa, sol, la, si, and the numbers of holes in the circular series are related to each other as the numbers of vibrations which form the tones do, re, mi, fa, sol, la, si, or they may be equal to these numbers, so that when the wheel is rotated as many holes of each series will pass a given point in one second as there are vibrations per second in the notes represented by the respective series, provided, of course, that the wheel is rotated with the proper speed.
Parallel with the axis of the disktor wheel is arranged a series of electro-magnets 37, each included in an open circuit 38, charged by a battery 39 and opened or closed by'a Morse key 40. In operative relation to each .magnet is arranged a pivoted armature 4l,
to the rear end of which, which extends parallel with the disk 3l, is secured a shutter 42, which is large enough to cover one of the holes in the disk. The rear arms of these armatures are of different lengths and so arranged thatthe holes of one series will pass in succession b'ehind one shutter, the holes ot the next series behind another shutter, and so forth, so, that there will be a shutter for each series of holes and an electromagnet for actuatingY each shutter. 'lhc extended Varmature-levers are vall parallel to the plane of one radius of the wheel, and the shutters extend downwardly, crossing the plane of such radius, so that when the armaturesl are in their retracted position the shutters carried by their extended arms will obstruct those holes of all the series which If, now, the local circuit of one of the magnets 37 is momentarily closed by the key 40, its armature will be al?-A y,t1-acted and the shutter carried bythe same will bc raised to expose the hole which it covers@ in its normal position. ni pulating the keys magnets any one or obstructed by the shutters may Thus by ma-l of the different electroall of the holes formerly be exposed so long as the circuit remains closed. When the circuit is again opened,.the armature is withdrawn from the magnet and the shutter returns to its normal position.
Since I Ahave shown seven series of holes in the disk corresponding to the diatonic scale, there must be seven electro-magnets and seven shutters, and by reference to Fig. 1 it will be seen that the electro-magnets and shutters are disposed on each side of the disk, four of them,being on one side and three on the other. One extended arm of the armature on each side of the disk is straightand the others are angular in order to bring their shutters as nearas possible to the face of the disk. A source 43 of radiant energy-as, for instance, an electric-arc light-is arranged at the focus of a condensing-lens 44, which renders the diverging rays 45 from the former parallel, as shown at 46. 'lhese parallel rays are arranged to fall upon a cylindrical lens 47, mounted parallel tothe disk 31, and with its axis in the horizontal'plane of that radius of the disk which is occupied by the shutters 42 in their normal position. Thus a narrow which will prevent the passage of radiant energy to the selenium cell 48, arranged on the other side of the disk or wheel, and which is designed to vary circuit in accordance with the intensity and frequency 'of flashes of radiant energy impinging thereon. If,now, one of the shutters 42 be raised by depressing key while the disk 3l is rotating at its proper speed, flashes of radiant energy having a certain definite rhythm will fall upon the selenium cell through the apertures thus uncovered, and the resistance of the selenium cell being reduced momentarily by each impact thereon of such radiant energy there will be set up in the electric circuit, including said selenium cell, electrical undulations of a corresponding detinite rhythm, and a nionotelephone having the pitch corresponding to such rhythm, g spond to such undulatons. If more than one key is actuated at the same time, several series of electrical nndulations will be produced in the line, or, more correctly speaking, there will be electrical undulations having the characteristics-of allthe undulations produced or tending to be produced by the same selenium cell, so that if there are .a number ,of telephones in the line-circuit those hav- .ingthe pitch corresponding to the rhythms of the several electrical undulations will respond and multiple telegraphy will be carried tions which have been described with reference to the microphonic method. v
In Fig' I have illustrated diagrammatically the equipment of two stations 49 and 50 for radiophonic multiple telegraphy; but I have omitted, for the sake of clearness and simplicity, the shutters and the operating mechanism for thel same. disks 31 are supposed to be rotated at a proper uniform speed, and the selenium cells 48 48 are inthe line-circuit charged 'by a line-battery 51, and at each station there is a series i.iii.i.iiiiiiiiiii.iiiiiuminwwwwlmiliMutanteni... i
The perforatedy bundleof rays will fall upon the shutters,
the resistance of an electric f the corresponding l ICO IIO
on radiophonically by the 4same manipulaof monotelephones d16 arranged tandem. 'In z rheoton1e`constructed substantially like the tuning-fork rheotomes described with refer-- ence to Fig. 8, and in addition thereto there is a flexible sound-conveying tube 52 leading from the interior of the resonator 5 towithin avery short distance cf the face of the disk 31@ For convenience sake this tube is mounted upon standards 53 53. The tuning-fork 3 is accurately tuned to a definite pitch-say to the pitch of the tone si and the length of the sound-conveyer 5i' is such thatrthe fundamental note of the column of air within the same and Within the resonator, when set into vibration-,will also be .si. If, now, the tuning-fork is actuated, air-vibrations of the note si will proceed from the, open end of the sound-conveyer. If, on the other hand, the open end of the sound-conveyer is brought' into close proximity to the face of the disk 31 just yopposite one of the holes of the series si, and if the disk is rotated with such speed that as many holes'as there are air-vibrations due tothe tone si will pass in one second in front ofthe open end of the sound-conveyer,
'the column of air within the sound-conveyer will receive a like number of impulses, since the walls of "the holes actlike so many diminutive fans. It is now clear that if the tuning-fork is at work and the disk .rotates at the proper speed, the tones produced in the sound-conveyer by the tuning-fork and by the'disk, respectively, will be identical and will re-enforce each other. If, however, the speed of the disk is too high or Vtoo low, there will be an. interference of sound, which' will manifest itself bybeats. Itis now .easy to adjust the speed of the disk` so that the beats' disappear, and when this isl reached we are certaimthat the disk rotates at the proper speed, and' it is onlyneeessary to maintain such lspeed by any known or .improved regu-v lator.
As has heretofore been stated, the disk will preferably be rotated by an electric motor 33, fed-,by abattery or other source of electricity 54, in the circuit of -which is also included a rheostat 55, composed of a platinum or German-silver wire 5 6 and a movable contact 57, all substantially like the well-known rheocord -of Poggendorif. A current-meter 58 is also included in the motor-circuit to indicate variations of current, so that by adjusting the contact 57 the current canbe maintained con- -'ten centimeters long.
stant and the unitormity of the speed of the ,sensitive to radiant energy, for I'can use not only selenium, but also an alloy of selenium and tellurium, tellurium alone, also lampblack, sulphide, iodide, bromide, or chloride of silver, sulphide of tin, sulphide of antimony, galena, oxide of copper or of iron, and phosphide of zine. I shall adhere to the term selenium cell as a generic name for all devices adapted to varyl the resistance of a circuit by the action thereon of radiant energy, and I will now describe the construction of selenium cells which I use by preference.
One of my new forms of selenium cell is illustrated in Fig. 3. I use two brass plates 59 59', two centimeters wide and from six to They are 'placed parallel to -each other, and are covered with layers of asbestus paper G0, by which they are bound together, and at the same time insulated from each other. They are connected together at their ends by hard-rubber crosspieces 61 61. Onpthe asbestus covering are wound in close spirals t and parallel to each other two wires 62 62', of platinum, copper, brass, or other metal, one of said wires 62 lbe.- ing shown in dotted lines. The two endsv of the wire 62 arev connected with the plate 59', and those'of the wire 62 are connected with thevplate 59, as shown. l
' Before applying the vhard-rubber crosspieees the device is heated on a mica plate to such temperature that a pencil of selenium placed thereon will just begin to melt. This temperature is about 210 centigrade or 410 Fahrenheit. The pencil of selenium is then rubbed rapidly over the surface of the device,care being taken to ll the spaces between' the two wires 62 62 and to maintain the'l temperature. The device is then allowed to cool slowly, so that the selenium surface may preserve a dark-gray color.
By leaving a space of about one millimeter between the two wires a selenium cell is obtained which is very sensitive to intense light. The electrical resistance of suchacell gradually risesl to about three hundred thousand (300,000) ohms, and then remains con- 'stant .for several years without losing its sen- 'sitiveness -It will be understood that cells may be constructed having a much smaller normalelectrical resistance if the two wires are placed closer to each other.
If, in place of selenium, sulphide of silver is used, the cell will assume the shape shown in Fig. 4. The two wires62 62 in this case maybe made of silver, platinum, aluminium,
' iron, &c., and they are wound in the same manner as in the construction shown in Fig. 3; but in-this case they are placed upon a layer of sulphide of silver spread on an insulating-plate 63 of asbestus, cork, or mica, the upper surface of which is rounded off. The plate 63 itself is mounted upon a plate '64 of hard rubber, which is arranged parallel .to another similar plate 64', fixed upon stand-4 ards 65. Adjusting-screws 66, passing through the lower hard-rubber plate, bear upon the underside of plate 61, whereby the two plates may be adjusted to and from each other and the pressure of the wires 62 62" upon the sulphide of silver maybe varied, thlis varying the'normal resistance of the ce ing-post 67,'and one endof the wire 62 is connected with binding-post 67.
Insteadof varying the resistance'of a eircuit directly by the impact of radiant energy upon selenium or other. similar bodies, this can be done indirectly in the manner which 1 have called the thermo-microphonic mode, and in Fig. 7 I have illustrated one apparatus which may be used for this purpose. Upon `a standard (58, mounted by a ball-and-socket joint 69, is a microphone-box 70. The diaphragm 71 of this microphone may be made of hard rubber, or it may be made 'of any other resonant material, upon the upper surface of which is then deposited a thin layer of lamp-black. The microphone proper,` which Yin the drawingsis shown of the Hughes form, is mounted upon the rear side of the diaphragm, and a protecting glass plate 72 is placed on the front of the same.
The operation of such an apparatus is based upon .principles Anow well understood in the art. It is known that when heat-rays impinge upon the hard-rubber or lamp-black surface of the diaphragm the same will be set into vibration. Consequently the microphone, which I mount upon the diaphragm, will be actuated, and will produce electrical undulations in the local circuit 12', which includes a battery 13' vand the primary of an induction-coil 14:. The
- secondary f said induction-coil, which may or may not include a line-battery '51', is then Yconnected in the sam'e manner as has been explained with reference to Fig. 8.
In Fig. 9 the arrangement for practicing my system of multiple telegraphy by the photophonlc mode is diagrammatically illustrated.
One end of wire 62 is carried to bind- The optical system` described with reference to Fig. 1 and thc perforated disk and shutters with their actuating magnets and keys are used in this case. inder-lens 47 is marked in the drawings by the numeral 73, and this line is coincident with the focus of another condensing-lens 44', from which the rays proceed in a cylindrical parallel bundle 46 and-,fall upon a third condensing-lens 4i at the distant station. These raysvare thus concentra-tod upon the surface of the selenium cell 4S, in the circuit of which are placed the monotelcphones 16. By thusv combining the apparatus described with reference to Figs. 1 and 2 with the additional lenses just described I can practice multiple telegraphy without the use of a line-wire, as will now be readily understood; but,
Having now fully described 'my invention,I do claim and desire to secure by Letters Pntent- A 1. In the art of multiple telegraphy, the hereinbefore-described method, which consistsin producing electrical undulations bearing the characteristics of two or more sets of as many distinct rhythms byand in accordance with rhythmical impulses of radiant cnergy, and thereby producing sound-waves in sets of the different rhythms.
2. In the art of 'multiple telegraphy, the hereinbefore-described method, which consists in producing electrical undulations bearing the characteristics oftwo or more sets of as many distinct rhythms by and in accordance with. rhythmical flashes of light, and thereby producing sound-waves in sets of the different rhythms.
3. In the art of multiple telegraphy, the hereinbefore-described method, which consists in producing simultaneously two or more sets of rhythmical Yariations of resistance in a charged electric circuit by and in accordance with two or more sets of rhythmical impulses of radiant energy, each set having a different rhythm,l and thereby' producing sound-waves in sets of the different rhythms.
In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.
ERNEST JULES PIERRE MERCADIEII.
R. J. PRESTON,-I ALBERT COHEN.V
.i cambiante iiiii thm.- wultmmwumt.
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