# United States patent 723188

| No. 723,188 | | Patented March 17, 1903 |
| | N. Tesla. Method of Signaling. Application filed June 14, 1901. | |
United States Patent Office.
Nikola Tesla, of New York, N. Y.
Method of Signaling.
Specification forming part of Letters Patent No. 723,188, dated March 17, 1903.
To all whom it may concern:
Be it known that I, Nikola Tesla, a citizen of the United States, residing in the borough of Manhattan, in the city, county, and 5State of New York, have invented certain new and useful Improvements in Methods of Signaling, of which the following is a specification, reference being had to the drawings accompanying and forming a part of the the 10same.
In certain systems for transmitting intelligible messages or governing the movements and operations of distant automata electrical impulses or disturbances produced by 15suitable apparatus are conveyed through the natural media to a receiving-circuit capable of responding to the impulses, and thereby effecting the control of other appliances. Generally a special device, highly sensitive, is 20connected to the receiving-circuit, which in order to render it still more susceptible and to reduce the liability of its being affected by extraneous disturbances is carefully adjusted so as to be in tune with the transmitter.25 By a scientific design of the sending and receiving circuits and other apparatus and skilful adjustment of the same these objects may be in a measure attained; but in long experience I have found that 30notwithstanding all constructive advantages and experimental resources this method is in many cases inadequate. Thus while I have succeeded in so operating selectively under certain favorable conditions more than one 35hundred receivers in most cases it is practicable to work successfully but a few, the number rapidly diminishing as, either owing to great distance or other causes, the energy available in the tuned circuits becomes 40smaller and the receivers necessarily more delicate. Evidently a circuit however well constructed and adjusted to respond exclusively to vibrations of one period is apt to be affected by higher harmonies and still 45more so by lower ones. When the oscillations are of a very high frequency, the number of the effective harmonies may be large and the receiver consequently easily disturbed by extraneous influences to such an 50extent that when very short waves, such as those produced by Hertzian spark apparatus, are used little advantage in this respect is to be derived from tuning the circuits. It being an imperative requirement in most practical applications of such systems of signaling55 or intelligence transmission that the signals or messages should be exclusive or private, it is highly desirable to do away with the above limitations, especially in view of the fact which I have observed that the 60influence of powerful electrical disturbances upon sensitive receivers extends even on land to distances of many hundreds of miles and consequently, in accordance with theory, still farther on sea. To overcome these 65drawbacks and to enable a great number of transmitting and receiving stations to be operated selectively and exclusively and without any danger of the signals or messages being disturbed, intercepted, or interfered with in any70 way is the object of my present invention.
Broadly stated, this invention consists in generating two or more kinds or classes of disturbances or impulses of distinctive character with respect to their effect upon a 75receiving-circuit and operating thereby a distant receiver which comprises two or more circuits, each of which is tuned to respond exclusively to the disturbances or impulses of one kind or class and so arranged that the80 operation of the receiver is dependent upon their conjoint or resultant action.
By employing only two kinds of disturbances or series of impulses instead of one, as has heretofore been done, to operate a 85receiver of this kind I have found that safety against the disturbing influences of other sources is increased to such an extent that I believe this number to be amply sufficient in most cases for rendering the exchange of 90signals or messages reliable and exclusive; but in exceptional instances a greater number may be used and a degree of safety against mutual and extraneous interference attained, such as is comparable to that afforded by a95 combination-lock. The liability of a receiver being affected by disturbances emanating from other sources, as well as that of the signals or messages being received by instruments for which they are not intended, may,100 however, be reduced not only by an increased number of the coöperative disturbances or ​series of impulses, but also by judicious choice of the same and order in which they are made to act upon the receiver.
Evidently there are a great many ways of 105generating impulses or disturbances at any wave length, wave form, number or order of succession, or of any special character, such as will be capable of fulfilling the requirements above stated, and there are also many 110ways in which such impulses or disturbances may be made to coöperate and to cause the receiver to be actuated, and inasmuch as the skill and practical knowledge in these novel fields can only be acquired by long experience 115the degree of safety and perfection attained will necessarily depend upon the ability and resource of the expert who applies my invention; but in order to enable the same to be successfully practiced by any person 120possessed only of the more general knowledge and experience in these branches I shall describe the simplest plan of carrying it out which is at present known to me.
For a better understanding of the subject 125reference is now made to the accompanying drawings, in which—
Figures 1 and 2 represent diagrammatically an apparatus and circuit connections employed at the sending and receiving stations 130respectively, for the practice of my invention; and Figs. 3, 4 and 5, modified means which may be employed in the practical application of the invention.
In Fig. 1, S$^1$ S$^2$ are two spirally-wound coils 135or conductors connected with their inner ends to preferably elevated terminals D$^1$ and D$^2$, respectively, and with their outer ends to an earth-plate E. These two coils, conductors, or systems D$^1$ S$^1$ E and D$^2$ S$^3$ E have different and 140suitably-chosen periods of vibration, and, as pointed out in other patents relating to any system of energy and intelligence transmission, their lengths should be such that the points of maximum pressure developed therein 145coincide with the elevated terminals D$^1$ D$^2$. By suitably-chosen periods of vibration such periods are meant as will secure the greatest safety against interference, both mutual and extraneous. The two systems may 150have electrical oscillations impressed upon them in any desired manner conveniently by energizing them through primaries P$^1$ and P$^2$, placed in proximity to them. Adjustable inductances L$^1$ and L $^2$ are preferably included 155in the primary circuits chiefly for the purpose of regulating the rates of the primary oscillations. In the drawings these primaries P$^1$ and P$^2$ surround the coils S$^1$ S$^2$ and are joined in series through the inductances L$^1$ 160L$^2$, conductor F, condensers C$^1$ and C$^2$, brush-holders B$^1$ and B$^2$, and a toothed disk D, which is connected to the conductor F and, if desired, also to the ground-plate E, as shown, two independent primary circuits being thus 165formed. The condensers C$^1$ and C$^2$ are of such capacity and the inductances L$^1$ L$^2$ are so adjusted that each primary is in close resonance with its secondary system, as I have explained in other patents granted to me. The brush-holders B$^1$ and B$^2$ are capable 170independently of angular and, if mevessary, also of lateral adjustment, so that any desired order of succession or any difference of time interval between the discharges occurring in the two primary circuits may be obtained.175 The condensers being energized from a suitable source S, preferably of high potential, and the disk D being rotated, its projections or teethe p p coming at periodically-recurring intervals in very close proximity to or, as the180 case may be, in contact with conducting rods or brushes n n cause the condensers to be discharged in rapid succession through their respective circuits. In this manner the two secondary systems D$^1$ S$^1$ E and D$^2$ S$^2$ E are set185 in vibration and oscillate freely each at its proper rate for a certain period of time at every discharge. The two vibrations are impressed upon the ground through the plate E and spread to a distance reaching the 190receiving-station, which has tow similar circuits or systems e s$^1$ d$^1$ and e s$^2$ d$^2$, arranged and connected in the same manner and tuned to the systems at the sending-station, so that each responds exclusively to one of the two195 vibrations produced by the transmitting apparatus. The same rules of adjustment are observed with respect to the receiving circuits, care being furthermore taken that the tuning is effected when all the apparatus is200 connected to the circuits and placed in position, as any change may more or less modify the vibration. Each of the receiving-coils s$^1$ and s$^2$ is shunted by a local circuit containing, respectively, sensitive devices a$^1$ a$^2$, batteries205 b$^1$ b$^2$, adjustable resistances r$^1$ r$^2$ and sensitive relays R$^1$ R$^2$, all joined in series, as shown. The precise connections and arrangements of the various receiving instruments are largely immaterial and may be210 varied in many ways. The sensitive devices a$^1$ a$^2$ may be any of the well-known devices of this kind—as, for example, two conducting-terminals separated by a minute air-gap or thin film of dielectric which is215 strained or weakened by a battery or other means to the point of breaking down and gives way to the slightest disturbing influences. Its return to the normal sensitive state may be secured by momentarily interrupting220 the batter-circuits after each operation or otherwise. The relays R$^1$ R$^2$ have armatures l$^1$ l$^2$, which are connected by a wire w and when attracted establish electrical contacts at c$^1$ and c$^2$, thus closing a circuit containing225 a battery b$^3$ and adjustable resistance r$^3$ and a relay R$^3$. From the above description it will be readily seen that relay R$^3$ will be operated only when both contacts c$^1$ and c$^2$ are closed.230
The apparatus at the sending-station may be controlled in any suitable manner—as, for instance, by momentarily closing the circuit of the source S, two different electrical vi-​brations being emitted simultaneously or in rapid succession, as may be desired, at each closure of the circuit. The two receiving circuits at the distant station, each tuned to 235respond to the vibrations produced by one of the elements of the transmitter, affect the sensitive devices a$^1$ and a$^2$ and cause the relays R$^1$ and R$^2$ to be operated and contacts c$^1$ and c$^2$ to be closed, thus actuating the 240receiver or relay R$^3$, which in turn establishes a contact c$^3$ and brings into action a device a by means of a battery d$^4$, included in a local circuit, as shown. But evidently if through any extraneous disturbance only one 245of the circuits at the receiving-station is affected the relay R$^3$ will fail to respond. In this way a communication may be carried on with greatly-increased safety against interference and privacy of the messages may be 250secured. The receiving-station shown in Fig. 2 is supposed to be one requiring no return message; but if the use of the system is such that this is necessary then the two stations will be similarly equipped, and any well 255known means, which it is not thought necessary to illustrate here, may be resorted to for enabling the apparatus at each station to be used in turn as transmitter and receiver. In like manner the operation of a receiver, 260as R$^3$, may be made dependent instead of upon two upon more than two such transmitting systems or circuits, and thus any desired degree of exclusiveness or privacy and safety against extraneous disturbances may 265be attained. The apparatus as illustrated in Figs. 1 and 2 permits, however, special results to be secured by the adjustment of the order of succession of the discharges of the primary circuits P$^1$ and P$^2$ or of the time 270intervals between such discharges. To illustrate: The action of the relays R$^1$ R$^2$ may be regulated either by adjusting the weights of the levers l$^1$ l$^2$, or the strength of the batteries b$^1$ b$^2$, or the resistances r$^1$ r$^2$, or in other 275well-known ways, so that when a certain order of succession or time interval between the discharges of the primary circuits P$^1$ and P$^2$ exists at the sending-station the levers l$^1$ and l$^2$ will close the contacts c$^1$ and c$^2$ at the same 280instant, and thus operate the relay R$^3$, but will fail to produce this result when the order of succession of or the time interval between the discharges in the primary circuits is another one. By these or similar means 285additional safety against disturbances from other sources may be attained and, on the other hand, the possibility afforded of effecting the operation of signaling by varying the order of succession of the discharges of the two 290circuits. Instead of closing and opening the circuit of the source S$^1$, as before indicated, for the purpose of sending distinct signals it may be convenient to merely alter the period of either of the transmitting-circuits arbitrarily, 295as by varying the inductance of the primaries.
Obviously there is no necessity for using transmitters with two or more distinct elements or circuits, as S$^1$ and S$^2$, since a succession of waves or impulses of different characteristics may be produced by an instrument300 having but one such circuit. A few of the many ways which will readily suggest themselves to the expert who applies my invention are illustrated in Figs. 3, 4, and 5. In Fig. 3 a transmitting system e s$^3$ d$^3$ is partly shunted305 by a rotating wheel or disk D$^3$, which may be similar to that illustrated in Fig. 1 and which cuts out periodically a portion of the coil or conductors s$^3$, or, if desired, bridges it by an adjustable condenser C$^3$, thus altering the310 vibration of the system e s$^3$ d$^3$ at suitable intervals and causing two distinct kinds or classes of impulses to be emitted in rapid succession by the sender. In Fig. 4 a similar result is produced in the system e s$^4$ d$^4$ by 315periodically short-circuiting, through an induction-coil Land a rotating disk D$^4$ with insulating and conducting segments, a circuit p$^4$ in inductive relation to said system. Again, in Fig. 5 three distinct vibrations are caused320 to be emitted by a system e s$^5$ d$^5$, this result being produced by inserting periodically a number of turns of an induction-coil L$^4$ in series with the oscillating system by means of a rotating disk B$^5$ with two projections p$^5$ p$^5$325 and three rods or brushes in, placed at an angle of one hundred and twenty degrees relatively to each other. The three transmitting systems or circuits thus produced may be energized in the same manner as those of Fig. 1330 or in any other convenient way. Corresponding to each of these cases the receiving-station may be provided with two or three circuits in an analogous manner to that illustrated in Fig. 2, it being understood, of course,335 that the different vibrations or disturbances emitted by the sender follow in such rapid succession upon each other that they are practically simultaneous so far as the operation of such relays as R$^1$ and R$^2$ is concerned. 340Evidently, however, it is not necessary to employ two or more receiving-circuits, but a single circuit may be used also at the receiving-station constructed and arranged like the transmitting-circuits or systems illustrated in Figs.345 3, 4, and 5, in which case the corresponding disks, as D$^3$ D$^4$ D$^5$, at the sending will be driven in synchonism with those at the receiving stations as far as may be necessary to secure the desired result; but whatever the 350nature of the specific devices employed it will be seen that the fundamental idea in my invention is the operation of a receiver by the conjoint or resultant effect of two or more circuits each tuned to respond exclusively to355 waves, impulses, or vibrations of a certain kind or class produced either simultaneously or successively by a suitable transmitter.
It will be seen from a consideration of the nature of the method hereinbefore described360 that the invention is applicable not only in the special manner described, in which the transmission of the impulses is effected through natural media, but for the transmis-​sion of energy for any purpose and whatever the medium through which the impulses are conveyed.
What I claim is—
3651. The method of operating distant receivers which consists in producing and transmitting a plurality of kinds or class one of a plurality of circuits tuned to respond to impulses of such kind or 370class and operating or controlling the operation of a receiver by the conjoint action of two or more of said circuits, as set forth.
3752. The method of signaling, which consists in producing and transmitting a plurality of kinds or classes of electrical impulses or disturbances, developing by the impulses of each class a current in one of a plurality of receiving380-circuits tuned to respond exclusively thereto and controlling by means of conjoint action of such circuits a local circuit, as set forth.
3. The method of signaling which consists 385in producing a plurality of series of impulses or disturbances differing from each other in character and order of succession, exciting by the impulses of each series one of a plurality of receiving-circuits tuned to respond 390exclusively thereto and controlling by the conjoint action of such circuits a local circuit, as set forth.
4. The method of signaling which consists in producing a plurality of series of electrical 395impulses of different character, varying the time interval between the emission of such impulses, exciting by the impulses of each series one of a plurality of receiving-circuits tuned to respond exclusively thereto and 400controlling by the conjoint action of such circuits a local circuit, as set forth.
5. The method of transmitting electrical energy for conveying intelligible signals which consists in producing a plurality of electrical 405impulses of different character, developing by the impulses of each kind a current in one of a plurality of receiving-circuits tuned to respond exclusively thereto, controlling the action or effect of the transmitted impulses 410upon the receiving-circuits by varying the character of said impulses, and operating or controlling the operation of a receiver by the conjoint action of two or more of said receiving-circuits, as set forth.
6. The method of transmitting electrical 415energy which consists in producing a plurality of electrical waves or impulses of different periodicities, varying the order of transmission of the waves or impulses forming elements of the signal sent, according to one or420 another receiving-station is to be communicated with where (proper circuit-closing mechanism being provided at each receiving-station) the transmitted signal will be intelligible at and only at the intended receiving425-station.
7. The method of transmitting intelligence, which consists in selecting and associating together in predetermined order of succession two or more electrically-generated impulses430 of different periodicity, forming elements of signals to be sent, and transmitting such selected impulses with reference to the conjoint action of both or all in the production of a signal at a distant point, substantially as set435 forth.
8. In a system of telegraphy, wherein signals or messages are sent by the use of a plurality of electrical impulses of different periodicities and in a predetermined order of succession,440 the method of ascertaining at any particular station the particular signal sent to that station, which consists in the selection, to form a signal, of certain transmitted impulses of different periodicities and of a predetermined445 order of succession to the exclusion of all others, as st forth.
9. The improvement in the art of transmitting electrical energy which consists in operating or controlling a receiving mechanism450 by series or group of electrical impulses of different periodicities and of a predetermined order of succession.
10. In a system for the transmission of electrical energy, for sending signals or messages455 to any one of two or more receiving-stations, the method of transmitting the message with reference to the intelligible receipt thereof transmission of electrical waves or impulses460 of different periodicities in varying order of transmittal by a separate order or grouping of transmittal for each receiving-station.
Nikola Tesla.
    Witnesses:
       M. Lawson Dyer,
       Benjamin Miller.
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
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