US737170A - Apparatus for selective electric signaling. - Google Patents

Description

N0. 737,170. PATBNTED AUG. 25, 1903.

I J. S. STONE APPARATUS FOR SELECTIVE EEEQTBIG SIGNALING.

APPLICATION FILED A139 2;, 1902.

N0 MODEL 3 SHEETS-SHEET 1.

. TNI EEEE k/ENTER No. 737,170. PATBNTED AUG; 25, 1-903.

7 J.S.STONE.' APPARATUS FOR SELECTIVE ELECTRIC SIGNALING.

APPLIOATION FILED AUG. 2, 1902.

N0 MODEL. 3 SHEETS-SHEET 2.

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No. 737,170. FATENTEDJ AUG. 2 1903;

- J. s. STONE.

APPARATUS FOR SELECTIVE ELECTRIC SIGNALING.

- APPLICATION FILED AUG.2,1902. I N0 MODEL. 7 I a SHEETS-SHEET 3 WITPIEES as;

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so. 737,17'b.

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Patented August 25, 1903;

RAT NT OFFICE.

JOHN STONESTONE, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR TO STONE TELEGRAPH AND TELEPHONE COMPANY, OF PORTLAND, MAINE, A

CORPORATION OF MAINE.

APPARATUS FOR SEL ECTIVE ELECTRIC SIGNALING.

SPECIFICATION forming part of Letters Patent No, 7 37,1 70, dated August 25, 1903.

Application filed August 2, 1902.

5'0 all whom it may concern;

Be it known that I, JOHN STONE STONE, a citizen of the United States, and a resident of Cambridge, in'the county of Middlesex and Commonwealth of Massachusetts, have invented certain new and useful Improvements in Apparatusfor SelectiveElectric Signaling,

of which the following is a specification.

My invention relates to the art of wireless or space telegraphy-t'. e., to the artof transmitting intelligence from one station to an- T other by means of free or unguided electromagnetic signatwaves or waves which are developed by producing electric vibrations in. an elevated conductor, preferably vertically elevated, and which are not guided to their destination by wires, as in the system of telegraphy most commonly practiced to-day.

The object of the present invention is to realize a system in which the transmitting- I stationsmay selectively transmit their signals each to a particular receiving-station simultaneously or otherwise without mutual interference.

It is also the object ofthe invention to provide means whereby each of a plurality of transmitting and receiving stations in such a system may be enabled to selectively place itself in communication with any other station to the exclusion of all remaining stations.

It is further the object of the present inven- IiOll to enable the vertical or elevated conductor in such a system to be made the source of electromagnetic waves of any desired frequency independent of its length and other geometrical constants.

The fundamental or underlying principles of the present invention are fully described in an application for United StatcsPatent, Serial No. 4,505, filed by me FebruaryB, 1900, and the present invention is, moreover, tributary to an application for United States Patent, Serial No. 44,384, filed by me January 23, 1901. The present specification describes and claims a specific form of the broad inventions described and claimed in the aforesaid applications Serial Nos.4,505 and44t,384=.

Bymy invention the elevated conductor of,

Serial No- 118,048. (No model.)

of signal-waves of but a single frequency, and the translating apparatus at the receivingstation is caused to be selectively responsive to signal-waves of-but a single frequency, so that the transmitting apparatus corresponds to a tuning-fork sending buta single musical tone and the receiving apparatus corresponds to an acoustic resonator capableof absorbing the energy of that single musical tone only. When the elevated conductor is aperi- 6o odic, it is adapted to receive ortransmit all frequencies, and accordinglya single aperi odic elevated conductor may be associated with a plurality of local circuits each attuned to a different frequency after the manner well known in the art of multiple telegraphy by wire conductors.

When a single elevated conductor is to be made the source of a plurality of signal-waves of different frequencies and when, moreover, these signal-waves are to be simultaneously developed, it is obviously necessary that the trains of waves of different frequencies de-' veloped at the elevated conductor shall be independent of each otheri. 6. it is necessary that-the electric vibrations of one frequency impressed upon the elevated conductor shallnot be affected by the act of si= multaneously impressing vibrations of another frequency upon the conductor. The manner of developing the individual electric vibrations of a particular frequency described in this specification is such as to insure per se the required independence of the vibrations when severaldiiferent frequencies '85 v are simultaneously impressed upon the elevated conductor. Two preferred forms of such arrangement of apparatus will hereinafter he described. 7

When the apparatus at a particular receivo ingstation is made resonant to the same frequency as that of the electromagnetic waves emanating from a particular transmittingstation, then this receiving-station will respond to and be capable of selectively receiving messages from that particular transmit ting-station to the exclusion of messages simultaneously or otherwise sent from other the transmitting-station is made the source 50 transmitting-stations in the neighborhood which generate electromagnetic waves of other frequencies. Moreover, by my inveni tion the operator at the transmitting or receiving station may at will adjust the apparatus at his command in such a way as to place himself in communication with any one of a number of stations in the neighborhood by bringing his apparatus into resonance with the frequency employed by the station with which intercommunication is desired.

In order that the vertical conductor at the transmitting-station shall generate electromagnetic signal-waves of a given frequency, I cause the corresponding electric vibrations in the conductor to be of said given frequency, and this in turn I accomplish by producing forced electric vibrations in the vertical conductor in lieu of producing natural vibrations in the conductor, as has heretofore been practiced. In order that the electricjtranslating apparatus at a receiving-station shall be operated by electric Waves of a given frequency and by no others, I interpose between the elevated conductor at the receiving-station and the translating devices a circuit or circuits made resonant to the particular frequency of the electromagnetic waves the energy of which it is desired to have operate the translating devices.

Having thus broadly described the nature and object of the invention and having given at some length the electrical principles upon which it is based in the hereinbefore-mentioned applications Serial Nos. 4,505 and 4,384, it will suffice to give the following brief statement of the electrical phenomena involved in the operation of the apparatus to be hereinafter more fully specified.

If the electrical equilibrium of a conductor be abruptly disturbed and the conductor be thereafter left to itself, electric currents will flow in the conductor which tend to liltimately restore the condition of electrical equilibrium. These currents may be either unidirectional or oscillatory in character, depending upon the relation between the principal electromagnetic constants of the couductor-vl. (2., upon its electromagnetic and electrostatic capacities and its resistance. In general the determination of the relations which must subsist in order that an oscillatory restoration of equilibrium shall take place in an electric system and the determination of the periods of these oscillations is very difficult; but in certain simple cases the determination of the conditions for an oscillatory restoration of equilibrium and of the period of these oscillations is quite simple.

An example of a simple system capable of an oscillatory restoration of equilibriumis to be found in the case of a circuit consisting simply of a condenser and a coil withoutiron in its core. If a charge of electricity be imparted to the condenser and if electrodes be then connected to the coil, an isochronous oscillatory current will in general be developed in the circuit in the process of restoration of its equilibrium. Such a simple circuit is known as a system of a single degree of freedom, and the electric oscillations which it supports when its electrical equilibrium is abruptly disturbed and it is then left to itself are known as natural vibrations or oscillations of the system. These vibrations begin with a maximum of amplitude and gradually die away in accordance with what is known as an exponential law and are of a single frequency. Such oscillations are simple harmonic with respect to time and are commonly called simple harmonic oscillations or vibrations. When two such simple circuits are associated together inductively, the system so formed is known as a system of two degrees of freedom, and in the oscillatory restoration of equilibrium-4'. a, in the natural vibrations of such circuitsthe currents are in general not of a single frequency, but in general consist of the superposition of two currents of different frequencies. In general, it it simple circuits be associated together in a system either by conductive or inductive connections a system of at least 02. degrees of freedom results, and the natural oscillations of such a. system will therefore consist of the superposition of at least a currents. It is, moreover, a fact that the components of the oscillations which together constitute the oscillatory restoration of equilibrium of a complex system are in general not the same as those of the separate simple circuits when these circuits are isolated; but the presence of each simple circuit modifies the natural period of each of the other circuits with which it is associated. The inductive association of two circuits increases the natural period of the high-period circuit and decreases the natural period of the lowperiod circuit. It is, moreover, a fact that during the restoration of electrical equilibrium currents of each of the periods are found in each of the circuits of the connected system.

The natural vibrations which would result in a circuit were it without resistance are termed the free vibrations of the circuit. Such vibrations cannot of course be developed in real circuits, but are interesting in the mathematical study of vibrating systems, because of the greater simplicityin the mathematical problem when resistance is ignored and because in the most important practical cases of oscillator-circuits the period of the natural vibration does not differ appreciabl from that of the free vibration.

The inductive association of two or more circuits need not necessarily result in an appreciable modification of their natural periods, since if the inductances of the circuits be made large compared to their mutual inductances by the addition to the circuits of large auxiliary inductancecoils the natural periods of the circuits will be sensibly the same as if they were isolated from each other.

Besides the ability to execute natural vi brations or oscillations electric systems are capable of supporting-what are termed currents resulting from thisimpressed force will also be of the given frequency. If the circuit in which the forced vibrations are developed be a system of asin'gle degree of freedo1nfor example, an isolated circuit consisting of a suitably-constructed inductance coil and condenserthen the circuit'will respond more powerfully to'vibratory forces of one particular frequency than to forces of any other frequency. Such a circuit is said to be a resonant circuit, and the particular frequency to which it responds most powerfully is said to be the frequency to which the circuit is resonant. 1 If a vibratory force of given amplitude or pressure be impressedupon sucha circuit and the frequency or rate of vibration of the force be slowly varied from zero to infinity,the amplitude or strength of the current so developed in the circuit will have but a single maxi-mum and that maximum will occur when the frequency or rate of vibration of the impressed force reaches that to which the circuit is resonant. Thisfrequency is numerically the same as the frequency of the free vibrations of the circuit.

1f the system in which the forced Vibrations are developed be a system of two or more degrees of freedom-for example, a group of simple resonant circuits brought into inductive relation with each otherthen the system-is in general not truly resonant to any particular frequency, since if a vibratory force of a given amplitude or pressure be impressed upon such a system and the frequency or rate of'vibration of the force be slowly varied from zero to infinity the amplitude or strength of the resulting currents will in general have maxima for two or more different frequencies of the impressed force. Such systems are said to be capable of multiple resonance and respond more or less powerfully to two or more frequencies or rates of vibration. The maxima in the amplitude of the currents referred to above are in general by no means sowell defined'in the case of systems of two or more degrees of freedom, as in the case of the single isolated circuit responding to the frequency of vibration to which it is resonant, and for this reason the ability of a system of several degrees of freedom to respond to any one of the several frequencies to which it is partially resonant may be termed quasi resonance. If two isolated simple circuits are resonant each to a particular frequency, and if thesetwo simple circuits be brought;

into inductive relation to each othertoiform a system of two degrees of freedom, the resulting system will in general be found to respond more or less strongly to two frequencies, neither of which is, however, the frequency to which either of the simple circuits constituting the system of two degreesof freedom was resonant before the simple cir cuits were brought into association with each other. In general the higher of the two frequencies to which the system will respond by virtue of its quasi resonance is higher than the higher frequency to which either of the two circuits of which it is composed responded when isolated, and the lower-of the two frequencies, to which the system will respond by virtue of its quasi resonance, is lower than the lower ofthe two frequencies to which either of the two circuits of which it is composed responded when isolated. The inductive association of two or more simple resonant circuits need not, however, necessarily result in an appreciable modification of the frequencies to which the individual circuits respond, nor need it necessarily materially diminish the power of the individual circuits to respond to the particular frequency to which-they were resonant when isolated, nor,

moreover, need it necessarily increase their susceptibility to-frequencies other than those ,to-which they were resonant when isolated,

tioned above be sensibly the same as if they were isolated from each other., and the vi-.

brations developed therein will be simple harmonic vibrations. H

The details of the invention may best be described by having reference to the draw ings which accompany and form a part of this specification.

The same letters so far as may be represent similar parts in all the figures of my drawings. 1

Figures 1 and 3 are diagrams illustrative of apparatus whereby several. stations may develop independently in a single elevated conductor forced electric vibrations of different frequencies, and thereby give rise to electromagnetic signal-waves of different fre-' quencies. Figs. 2 and 4 are diagrams illustrative of apparatus whereby several receiving-stations maybe associated with a single elevated 'conductorand selectively receive the energy of electromagnetic signal-waves of different frequencies each in a particular electroreceptive or translating device to the exclusion of the energy of electromagnetic waves of difierent frequencies. Figs; 5,6, and 7are illustrative of the tuning-condenser used as a receiver. 1

In the drawings, V represents an elevated conductor or vertical oscillator. I

M M M and M M M", are induction coilsj or transformers.

L L L and L, L, L, are auxiliary induct ance-coils.

C C C C and C, C, C, C are condensers. B and B, are batteries.

K and K, are coherers or other electroreceptive or electric translating devices.

and 7c, are keys.

R and R, are relays or other suitable translating devices.

- p andp, are automatic circuit-interrupters.

s and s, are spark-gaps.

P and P, are Plant batteries or condensers of large capacity.

E is an earth connection.

It is to be understood that in lieu of the batteries and automatic interrupters any source of periodically-varying electromotive force may be used-as, for example, an alternating-current generator such as shown in my Letters Patent Nos. 714,756 and 714,831.

In the organization shown in Figs. 1 and 3 the key 70 controls the supply of energy from the battery B to the circuit B 7c M When the key 70 is depressed, the battery B develops an interrupted current in the primary circuit of the induction or spark coil M", which by virtue of the action of the condenser C develops in the usual manner highpotential difierences between the terminals of the secondary of the spark-coil M. As the potential at the terminals of the secondary of M rises the charge in the condenser C increases till the potential difference is sufiicient to break down the dielectric at the spark-gap 3. When this occurs, the condenser C discharges through the spark at s, the primary of M, and the inductance-coil L. This discharge is oscillatory in character and of very high frequency, as will be eX- plained hereinafter. The spark-gap s and the condenser C may, however, be interchanged in position with like result, as shown in my hereinbefore-mentioned Letters Patent. The high-frequency current so developed passing through the primary of M induces a corresponding high-frequency electromotive force and current in the secondary of M, and forced electric vibrations result in the circuit M L M C. The circuit M LM C is made resonant to the same frequency as the circuit L s C M, and it therefore tends to weed out, and thereby screen, the elevated conductor V from harmonics, which may exist in the current developedin the circuitL s C M. This screening action of an interposed resonant circuitis due to the well-known property of such circuits by which a resonant circuit favors the development in it of currents of the frequency to which it is attuned and strongly opposes the development in it of currents of other frequencies. The forced electric vibrations induced in the circuit M L M C in turn induce a corresponding high frequency eleetromotive force in the secondary of M. The secondary of M is included in a branch circuit CL M of the elevated conductor V, which branch circuit is also made resonant to the frequency developed by the circuitL s C M, and the electromotive forces induced in M therefore give rise to forced electric vibrations of corresponding frequency in the vertical oscillator V C L M E. The energy of these vibrations is not absorbed in the branch C L M, of the elevated conductor V, because this latter branch is made resonant to afrequency different from that developed by the circuit L s C M, and therefore different from the frequency of vibration developed in the branch C L M. The circuits L s C M, M L M C, and C L M are each made resonant to the frequency of vibration, which is the frequency of the electromagnetic waves with which the operator of the key 70 transmits his signals. Correspondingly the circuits L, s, C, M,, M, L, M, C,, and C, L, M are each made resonant to another frequency, which is the frequency of the electromagnetic waves with which the operator of key 70, transmits his signals. WVhen the key 7c, is depressed, the result is exactly similar to that which results from the depressing of the key is except that the frequencies of the vibrations which result in the elevated conductor, and therefore also of the electromagnetic waves radiated, are differentin the two cases. The energy of the vibrations developed in the vertical oscillator V C, L, M, E, when the key 7t, is depressed is not absorbed in the branch 0 L M E of the elevated conductor V, because this branch is made resonant to a frequency different from that developed by the circuit L s, C, M,, and

therefore different from the vibrations so developed in the branch C, L, M E,. By virtue of the auxiliary inductance-coils L L" L, L,, designed according to the specifications set forth in my hereinbefore-mentioned Letters Patent, the inductances of the several circuits are made large compared to their mutual inductances, and thus the effects of their mutual inductances are swamped, and the oscillations developed in the circuits and impressed upon the elevated conductor Vare simple harmonic oscillations, and therefore the electromagnetic waves radiated by the elevated conductor are simple harmonic electromagnetic waves.

In Figs. 1 and 3 two stations are shown associated with a single elevated conductor, each station being capable of developing in the elevated conductor electric vibrations of a frequency different from that developed by the other station in said elevated conductor. Careful consideration will show that any desired number of stations may in like manner be associated with a single elevated conductor by means of branch circuits each made resonant to a particular frequency different from the frequency to which any of the other branch circuits is made resonant. Careful consideration will show that the operation must be the same in the case of the organizations illustrated in Figs. 1 and 3, since the apparatus and its disposition is thesame in the as shown in Fig. 1.

The operation of the receivingstation s (shown in Figs. 2 and 4) is as follows Electromagnetic waves of a given frequency impinging upon the elevated conductor V deof the current.

velop therein corresponding electric vibrations of like frequency. If the frequency of these vibrations be that to which the branchcircuit C L M is made resonant, the energy of the vibrations will be received in that branch to the exclusion of the branch C L M which is made resonant to a different frequency. The energy so received in branch 0 L M is communicated by means of the induction-coil M to the circuit C M L M, which is made resonant to the same frequency as the branch circuit- 0 L M, and thence the energy is communicated to the circuit C L" M, which is likewise'made resonant to the same frequency as that of the branches OMLMand C L M.

The energy so received in circuit C L M operates an electroreceptive or translating device. (Indicated at K in Fig. 2 and at ,L, in Fig- 4.) These electric translating devices will hereinafter be more fully specified. If the electromagnetic waves impinging uponthe elevated conductor V of Figs. 2 and 4 be of the frequency to which the branch circuit C, L M is made resonant, the energy of the resulting vibration in the elevated conductor V will be received in that branch to the exclusion ofthe branch 0 L M, which is made resonant to a different frequency. so received by the branch O L M will be comin unicated to the circuit O M L M,, which is made resonant to the same frequency as the branch O L M and thence to the circuit O L M which is made resonant to the same frequency as the circuits G M L M and G L M Energy so received causes the operation of an electroreceptive or translating device. (Indicated at O in Fig. 2 and at K in Fig. 4.)

In the circuit C L M of Fig. 4 the ele- ,ment L serves both as an electroreceptive or translating device and as an auxiliary inductance-coil, by which thecircuit C L M is made resonant to the desired frequency. It is actuated by the current developed in the circuit, utilizing therefor the kinetic energy This element will be hereinafter more fully described. Suffice it hereto say that by its operation the reception of the energy of the waves by the circuit C L M is made evident through the motion of the armature a.

In the circuit G L M of Fig. 2 the element G serves both as anelectroreceptive or translating device and as a tuning-condenser, by which the circuit O L M is made resonant to the desired frequency. Itis actuated The energy by the current developed in its circuit,'utilizing therefor the potential energyof the current. This element will be hereinafter more fully described.

When electric oscillations or oscillatory electric currents are developed in the circuit M L U P by electromagnetic waves of the frequency to which this circnit'is attuned,

these electric oscillations. or oscillatory electric currents pass through the coherer K, which is shunted around the terminals of the condenser O, and thereby cause the conductivity of said coherer to be so greatly increased that thecurrent of battery 13 is enabled to pass through the same. Because the highfrequency oscillatory electric currents developed in circuit M L C P are permitted to pass through the coherer and because a difference of electrical potential at the terminals of a coherer or of any other resistance is necessary to enable currents-to flow through said coherer or other resistance it maybe truly said that a coherer is both a currentoperated and a potential-operated electric translatin device or wave-res onsive de- 1 vice. In this connection it may be remarked that the condenser-receiver C above referred to and hereinafter more fully described, is, properly speaking, also a current-operated wave-responsive device or a current-operated electric translating device.

The use of a condenser in this relation has been described and claimed in my Letters Patent hereinbefore mentioned and in my Letters Patent No. 714,834, which the Commissioner of'Patents required me to divide from this application and is not herein.

they respond, respectively, to changes in cur-' rent or to changes in potential, it is herein pointed out that the only logical classification of such wireless-telegraph receivers, wave- I responsive devices, electroreceptive, or electric translating devices is with regard to the form of energy whereby they are operated. No instru ment whereby electric poweris measured can be said to be operated by current alone or by potentialalone. Thus an amperemeter is operated by potential as Well as by current and a voltmeter is operated by current as well as by potential. In other words, each is operated by electric energy, whichis the product of current by potential. virtue of a variable electromotive force .e, applied to a circuit, a current 2' is caused to flow therein, the energy imparted to the circuit in the time dt is the product e t dzf. The equation of electromotive forces in a circuit containing dissipative resistance, inductance, and capacity'is induction is L %,and that part of e necessary to overcome the counter electromotive force 'i all.

parted to such a circuit in the time (ll is, as above stated, e i (ll.

i (ll That part of this energy E i all which is used in heating the conductor and which is thus dissipated into heat is called the dissipative energy of the electric current. That part (h t dt which is expended in (ll creatinga magnetic field is called the kinetic energy of the electric current. That part of this energy 1 of the condenser is C lhe energy mof this energy L 'l at which is expended in charging the condenser is called the potential energy of the electric current. In the case of simple harmonic currents the dissi- 27r R 1 p 2 and the kinetic and potential energies expative energy expended in time 2 pended in time -2 are respectively? and 2 0 rent flowing in the circuit.

Examples of electroreceptive devices utilizing in their operation the dissipative energy of the currents developed in the circuits in which they are placed for detecting and measuring electromagnetic waves and for receiving space-telegraph signals are to be found in the following publications: Proceed lugs of the American Academy of Sciences, May 9, 1894, page 218, St. John; Elelctrotechm'sche Zeitscltmfl, XIX Jahrg. Heft 33, August 18, 1898, page 562, Tietz; LEclairage Eleolrique, Vol. 17, October 8, 1898, page 72, A. Turpain. I have described an electroreceptive device utilizing in its'operation the dissipative energy of the electric current developed in a resonant circuit in my applications for Letters Patent, Serial Nos. 119,211 and 122,853. Examples of electric translating devices utilizing in their operation the-kinetic energy of the currents developed in the circuits in which they are placed are to be found in United States Letters Patent No. 663,400, granted December 4, 1900, to E. Wilson and O. J. Evans, and examples of such electric translating devices are also to be found in the following publications: Proceedings ofthe Royal Society of London, Vol. LX, page 184, Rutherford; Philosophical Transactions ofthe Royal Society of London, Vol. CLXXXIX, A. page 1, Rutherford; Cir- I being the maximum value of the curcular No. 275, Condensers and their Applications, March, 1898, Philadelphia, J. G. Biddle.

I have described an electric translating device utilizing in its operation the kinetic energy of the electric current developed in a resonant circuit in this specification. Examples of electric translating devices utilizing in their operation the potential energy of the electric current developed in the circuits in which they are placed are to be found in United States Letters Patent No. 685,957, granted November 5, 1901, to Nicola Tesla and in Wt'edemamzs Amialen, Baude 44, page 74, Bjerknes. I have described an electric translating device utilizing in its operation the potential energy of the electric current developed in a resonant circuit in my Letters Patent Nos. 714:,756 and 714,834, dated December 2, 1902.

When the coherer K is cohered, as above explained, the batteryB is thereby permitted to develop a current in the circuit B R M, L K, which operates the relay R. Similarly when electric vibrations or oscillations are developed in the circuit M, L, P, G", L, of Fig. 4 the coherer K, is cohered, and the relay R, is operated by the current developed by battery B, in a circuit B, R, K, L", M, L,.

The function of the Plante batteries or condensers P P, is simply to provide a low impedance or short circuit for the electric Vibrations, while preventing the batteries 13 B, from normally developing a current through the relays R 3,, respectively. It should be understood that these Plante batteries or condensers are not essential to the tuning of the circuits in which they are included, and in order that they may not appreciably affect the tuning of the circuits in which they are included, and thereby lower the resonant rise of potential at the plates of the condensers O C,, they must be constructed to have large capacities compared to the capacities of the condensers O C,, as fully explained in my Letters Patent Nos. 714,756 and 714,831. These relays by their operation may cause a telegraphic sounder or other telegraphic receiver to respond, and they may also set in motion a tapper or decoherer by which the coherer is restored to its normal condition of high resistance.

The electroreceptive or translating device shown at 0",, Fig. 2, is primarily a tuningcondenser for the circuit C, L, M,; but it also serves to make evident the presence of electric vibrations in said circuit. It consists of a fixed armature or electrode and a movable armature or electrode. If electrical vibrations be of the frequency to which the circuit is made resonant, the electrodes of 0, will be at a difference of potential many times greater than the induced or impressed electromotive force. This difference of po-.. tential will cause an attraction between the armatures of O, and will cause the movable armature to approach the fixed armature.

This motion maybe utilized to close a local circuit, and thereby operate a telegraphic relay or sounder, or it maybe caused to deflect a beam of light reflected from its, surface.

In Fig. 2 the condensersreceiver ismerely shown conventionally; but theform used in practice is shown in Figs. 5, 6, and 7.

In Fig. is shown one form of translating device wherein the light from the lamp 1, reflected by the mirror 2 on the movable armature 3 of the tuning condenser 0 records the movement of said armature on scale 4 when a current flows in the circuit MV1LII1CIII1. I 7 Q In Fig. 6 the movable armature 3 closes the circuit of relay or sounder 6 by making .the circuit with which it is associated, but leaves the dimensions of its armatures andtheir separation undetermined. In order to get the maximum sensitiveness in the instrument, the separation between the opposing surfaces of the armatures is made as small as practicable, and consequently therefore the area of the armature-surfaces is alsoa minimum. By these means the entire potential energy of the vibratory current in thecircuit O" L M' is made available to operate-the electric translating device, and since the armatures are very close to each other the rate of change of the energy produced by the motion of the movable armature .is at a maximum. The available force to produce this motion is thus made as great as' possible.

Theelectric translating device (illustrated at L, Fig. 4,) consists ofa tuning-coil or auxiliary inductance coil and a fiat movable conducting-armature a, preferably placed in the axis of the coil and with its plane at an angle of 1-1\4 or forty-five degrees to the axis of the coil in the manner now well known in the art of alternating-current-measuring instruments and described first by Elihu Thomson in United States Patent No. 363,186, May 17,1887. However, as the energy of the electric oscillations to be detected is exceedingly feeble and the frequencies excessively Y high the apparatus must be correspondingly man-ns AmmlemVolAZ, page {107,or I may use a silver disk similar to that of the well-known Northrup galvanometer described in the Electrical World, December 18 and 25, 189 7,

and in. Catalogue B of Electrical Measuring Instruments,published byJ.G.Biddle,-Philadelphia,1898,page 75, or in Circular No. 275, on Condensers and theirApplications, published by J. G. Biddle, Philadelphia, March, 1898, page 23. When a vibratory current is developed in the circuit C L M of Fig. 4, a rapidly-vibratory magnetic field is produced in the coil L". This field induces a current in the armature aand causes it to rotate about its axis of suspension through an angle which depends upon the amplitude of the magnetic field, its rate of change, and the torsional rigidity of the support by which the armature is maintainedin its normal position. The movement of the armature a may be made evident by causing it to close a local-battery circuit, and thereby operate a telegraphic receiver, or it may be observed by noting the deflection of a beam of light reflected from its surface. It is to be noted that this electroreceptive or electric translating device is to be diiferentiated from a coherer in that no auxiliary mechanisms are required to restore it to normal sensitive condition after the reception of a signal, this being accomplished by the torsional rigidity of its suspension, or, in other words, that it is a self-restoring electric translating device or a self-restoring'waveresponsive device, whereas a coherer when once cohered by electric vibrations remains thereafter insensitive to subsequent electric Vibrations until tapped or restored to its normal sensitive condition and is not, therefore constantly receptive. The electroreceptive or electric translating device L is, on the con-.

'Neugschwenden, or Aschkinass type, or an autocoherer consisting of two members of metal in contact atasingle point, or of metal and carbon in contact, by the fact that it is metallically continuous and does not consist of a plurality of members in imperfect electrical contact, between which there necessarily exists an infinitesimal dielectric layer. Finally, as explained'above, this translating device is operated by the magnetic com- ,ponent of the electric oscillations or oscillatory electric currents developed in the circuit in which it is included, or, in other words, it is operated by the kinetic energy of This electric the currents developed in said circuit, which kinetic energy is proportional to the inductance of the coil L and to the square of the current, so that the indications produced by the flat movable armature are proportional.

to the total energy absorbed by the receiving-circuit and to the total energy absorbed to respond.

by the resonant circuit in which the coil L is included.

I am aware that 011 page 23 of Circular No. 375, above referred to, a Northrupgalvanometer is shown connected in series with aloop of wire about ten meters in diameter and with a condenser which is described as capable of being adjusted so that the circuit may be brought into tune with a second circuit containing a spark-gap, a similar condenser, and a similar loop of wire, whereby the magnetic induction effects of the oscillations created in said second circuit may be observed at ashort distance; but such an arrangement is not capable of radiating elec' tromagnetic waves, and, as explained below, such an arrangement is not capable of receiving high-frequency electromagnetic waves. I am aware that on page 24 of said Circular a Northrup galvanometer is shown connected in series with a I-Iertzian resonator designed to be used in conjunction with a Hertzian oscillator and capable of having its constants varied so that the galvanometer will give maximum defections when the frequency of the electromagnetic waves radiated by theoscillator is that to which the resonator is tuned This apparatus is designed to be used for the purpose of detecting electromagnetic waves emitted from and received by unclosed circuits--viz., a Hertzian oscillator and a Hertzian resonatorand is not intended to be used for the purpose of detecting the magnetic induction effects which one closed circuit, having rapidly-oscillating currents produced in it by a transformer, Hertz oscillator, or other suitable means, produces on another closed circuit, as is the case with the apparatus illustrated on page 23 of said Circular .No. 275. The efiects to be obtained by the apparatus shown on page 24 of said Circular are the same in kind as those sought in wireless telegraphy, and the means for producing these eifects while different from the means described herein are the same as those generally used in wireless telegraphy today in which natural oscillations are created in an elevated conductor containing a sparkgap in series therewith, the period of which oscillations, irrespective of any condenser which may be connected to the spark-gap by conductors of either negligible or appreciable inductance, being determined by the resistance, radiating power, capacity, and the inductance of said elevated conductor. It is not my purpose, however, to use the Northrup galvanometerpcrsc,and,in fact, the construction of this galvanometer is such as to preclude its use in the receiving system described herein. For whereas the Northrup galvanometer is described in Catalogue B, above referred to, as having twenty, forty, and even one hundred turns of copper wire in its fieldcoils closely crowded together in the smallest possible space and wound on solid dielectric cores I find it essential to the operativeness of my system to separate the turns of all coils in order to prevent excessive displacement currents, and I also find it necessary to avoid the use of solid dielectric cores in order to prevent electrostatic hysteresis, as hereinbefore described and as fully set forth in Letters Patent Nos. 714,756 and 714,831. Furthermore, the excessive distributed capacity and inductance reactance of the coils of the Northrup galvauometer due to its mode of construction would effectively prevent the tuningof its circuit to a single frequency, and their high resistance would mask the resonant rise in said circuit, whereas I find that for complete selectivity, as well as the efficient operation of the electric translating device shown at L, it is imperative that the latter be placed in a truly resonant circuit.

A IIertzian resonator is not accurately described as a resonant circuit, because it does not have sufiicient capacity or inductance to hold in the form of electrification and electromagnetism an appreciable amount of the electrical energy supplied thereto. In the form used by l-lertz merely a rectangular or circular loop of wire provided with a minute spark-gap or merely two wires separated by a spark-gap and each provided with a metallic wing or capacity area-the first oscillation, more powerful than the succeeding oscillations, produces a minute spark at the gap; but if it fails to develop sufficient potential difference at the terminals of the gap to break down the dielectric therebetween there is no cumulative action whereby the succeeding oscillations may develop the requisite potential. (See Lodge, Electrician, London, November 12, 1897.) Furthermore, a Hertz resonator in a manner similar to a stretched cord or a tuning-fork responds not only to the waves of the fundamental frequency to which it is attuned, but also to waves of all frequencies which are aliquot parts of said fundamental frequency l. 8., to all harmon'ies-and in general it may be stated that this is true of all electric circuits in which the inductance or capacity, or both, are distributed and not lumped or localized, as I have fully set forth in my Letters Patent Nos. 714,756 and 714,831. This phenomenon is aptly described by the term quasi resonance, to which I have referred in said Letters Patent, and it is called by Lodge, in referring to his now famous syntonic jar experiment, sympathetic resonance or syntony. (See Lodge, flloclcrn Views of Electricity, London, 1892, pages 339 and 443.) In such a tuned circuit the curve of variation of current with frequency, other things being equal, shows several maxima, or one for each harmonic frequency, and not, as in the circuits I have herein described, a single maximum for a given frequency. All .resonant circuits may properly be termed tuned circuits, but the converse is by no means true, although I am aware that this distinction has recently been overlooked by some. Then two resonant circuits are each i'earto attuned to the same frequency, they may properly be said ,to be syntonic but because two circuits are syntonic it by no means follows that they are necessarily resonant circuits or that they are attuned to the same frequency to the exclusion of other frequencies. Syntony is a property of two or more systems. Resonance is a property which may be possessed by a single system. Syntony may and in general does involve a multiplicity of poriods. Resonance involves only a single periodicity or simple harmonic vibration. If in a group of mechanical or electrical systems one of the systems be permitted to execute its natural vibrations, those other systems in the groupwhich are in syntony with this system will have sympathetic vibrations developed in them. If an electrical system be resonant, it will respond 'and execute greater vibrations when influenced by a simple harmonic force of one particular frequency than for any other, and it will show no marked tendency torespond to vibratory forces of any other frequency than that to which it is attuned even if these vibrations be of periodswhich are aliquot parts of the particular period to which the system is attuned. Syntony is a relation which may he established between two or more systems, but which cannot be the property of a single system. Resonance is a property of electrical systems which a system possesses without any reference to any other systems. For a vibratory electromotive force of any frequency other than that ofa certain predetermined critical frequency the respouse of a resonant circuitis extremely feeble. The current depends, other things being equal, upon the frequen.cy,and there is a certain critical frequency at which the said 'current is a maximum, and any change in the frequency from this point in either direction produces a decreased resulting current. The property of true resonance depends upon the simultaneous presencein the circuit of capacity and inductance, and in order that an electric circuit may have appreciable resonance it is requisite that'it possess sufficient capacity and inductance to hold in the form of electrification and electromagnet-ism an appreciable amount of the electrical energy supplied to it. For this purpose the capacity of the circuit must be lumped orlocalized capacity, as a condenser, and the inductance must bea lumped orlocalized inductance, as a coil. Such a circuit was first mathematically investigated by J.

Clerk Maxwell in the London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, Vol. 35,1868, page 362, and in Scientific Papers, Vol. 2, page 121, the peculiar properties of the circuit having been accidentally discovered by Grove, (Phil. 1l[ag., Vol. 35, 1868, page 184,) and it was afterward rediscovered by Dr. Muirhead and independently investigated by Professor Hopkiusou,-wl1o was the first to apply the term electrical resonance to the phenomenon. (Journal of the Society of Telegraph Engineers, Vol. 13, 1884, page 513.)

Although the literatureon the subject of electrical resonance is most voluminous, I shall herein set forth a few of the more important contributions thereto: first, Blakes- Hutin and Leblanc, No. 522,564, July 3, 1894; I

United States Patent to Paul Boucherot, No. 548,511, October 22, 1895; United States Patents t0 Pupin, Nos.'640,515 and 640,516, January 2, 1900.

I have fully described the property of a resonant circuit to selectively absorb the energy of currents of the frequency towhich it is attuned to the exclusion of the energy of currents of different frequency in the follow-' ing patents: No. 638,152, November 28,1899; No. 714,756, December 2, 1902; No. 714,831, December 2,1902; No. 714,834, December 2, 1902; No. 715,515, December 30, 1902; No. 717,467, December 30, 1902, and also in the following pending applications: application Serial No. 506,316, series of 1880, filed April 4, 1894, and in the divisions thereof, Serial Nos. 147,535, 115,056, and 115,057, series of 1900; in application Serial No. 506,517, series of 1880, filed April 4,1894, and in the divisions thereof, Serial Nos. 113,249, and 113,343, series of 1900, and in application Serial No. 526,986, series of 1880.

In view of the mass of literature on the subject of electrical resonance there is but one meaning which can be given to this'term and but one interpretation for the term resonant circuit,the properties of-whi'ch are now generally understood by those skilled in the art to be the properties investigated by Maxwell, Hopkinson, Lodge, and others above cit-e cl, although I am aware that it has recently been held by some that an elevated conductor connected in series with an inductance-coil,which .of course possesses lumped or localized induct-an ce, is resonant to the frequency determined by the capacity of the elevator-conductor, which of courseis distributed capacity and the lumped inductance of said coil. been even alleged in all seriousness that the capacity of the elevated conductor or aerial is lumped orlocalized and not distributed, because of the high frequency of the electromagnetic waves received by said aerial and because the length of the aerial is merely a fraction of the wave length of the received It has waves. The fallacy of this must be apparent upon mature consideration, because lumped capacity does not mean lumped as compared to the wave length, but lumped as compared to the inductance, just as distributed capacity does not mean distributed as compared to the wave length, but distributed as compared to the inductance. If the aerial conductor possesses lumped capacity for the reason above alleged by a parity of reasoning it must also possess lumped inductance, and the logical conclusion of the whole matter is that every aerial heretofore considered aperiodic is resonant to waves of some predetermined critical frequency by virtue of this alleged lumped capacity and lumped inductance without the interposition of condensers or coils, whereas experience teaches, on the contrary, that such a circuit, like a stretched cord or a Hertzian resonator, responds not only to a certain fundamental frequency, but to all frequencies which are aliquot parts of said fundamental. In a resonant circuit the kinetic energy and the potential energy are equal. The kinetic energy of a simple circuit is represented by the expression and its potential energy is represented by the expression CVKwhere L is the inductance in Henries, O the capacity in Farads, V the potential difference at the terminals of the coudenser, and 2' the current flowing in the circuit, is equal to the impressed electromotive force E divided by the ohmic resistance R of the circuit. From this it follows that in the case of resonance L (E); "13", R o n which shows that the ratio of the resonant rise of the potential at the terminals of the condenser to the impressed electromotive force, or, in other words, the selectance or the selectivity of the circuiti. c., its ability to differentiate currents of the frequency to which it is attuned from currents of all other frequencies-is highest or sharpest when the inductance is great as compared to the capacity and resistance, as I have pointed out in my Letters Patent Nos. 714,756 and 714,831.

I am aware that in a paper entitled The Possibilities of Wireless Telegraphy, published in the Transaction-90f the American Institute ofElectri'cal Engineers,Vol. 16, 1899, page 607, there is described a receiving apparatus for electromagnetic waves comprising an aluminium-wire ring similar to the aluminium-wire ring employed by Hertz (T Viedemmtns Annalee, Vol. 42, page 407) suspended so that its plane makes an angle of forty-five degrees with the axis of a coil in a manner substantially identical with the silr ver disk of the Northu p galvanometer. However, this coil does not form part of a closed resonant circuit, as no condenser is shown in the diagram on page 612 illustrating this apparatus, and while the use of a condenser is described the dispositon of such condenser with respect to the coil taken in connection with the subjoined statement in the text-- viz., that for a given voltage the opposition to the current is reduced to the ohmic resistance of the circuit-is such as to preclude the inference that it was the intention of the author to construct or describe a resonant circuit. I am aware that in the Electrical l Vorld and Engineer, Vol. 3%, August 12, 1899, page 239, a somewhat similar apparatus is described by the same author; but in the figure illustrating this paper the condenser is shown in series with the elevated conductor and galvanometer-coil, and no specifications are given for any proportionment of the capacity of this condenser and the inductance of this coil sufficient to justify the inference that a resonant circuit was contemplated. Furthermore, the disposition of the condenser in the system described in this paper is such as to increase the energy dissipated in the vertical Wire, and thus defeat the advantage alleged in the American Institute paper for the condenser in shunt to the coil. I am aware that in the Electrical l Vorlcl and Engineer, Vol. 34-, September 16, 1899, page 491, a somewhat similar receiving apparatus is described. In one of the forms illustrated in this paper a condenser is shown shuntingthe galvanometer-coil, but in the context there is nothing to indicate that the capacity of the condenser is so related to the inductance of the coil that the circuit containing the condenser and coil is resonant and responds to currents or oscillations of one predetermined critical frequency to the exclusion of currents of other frequencies.

3y means of a closed resonant circuit containing a condenser and inductance-coil correlated, as hereinbefore set forth, I am onabled to absorb the energy of electric oscillations created in the elevated conductor by electromagnetic waves of one frequency to the exclusion ofthe electric oscillations created therein by electromagnetic waves of other frequencies, and I am enabled to develop in this closed resonantcircuit currents of maximum amplitude when the oscillations created therein are of the frequency to which the circuit is resonant, and thus I am onabled to obtain appreciable deflections of the fiat movable armature Ct by electromagnetic waves of the proper frequency transmitted from a far-distant transmitting-station containing a source of persistent or maintained electromagnetic radiation.

In constructing the various parts of the apparatus shown and described in this specification there is great latitude as to the special forms that may be given them; but it must be remembered that when a circuit is to be made resonant and it is desired to-gain a high degree of resonance both electrostatic and electromagnetic hysteresis must be carefully excluded from the resonant circuit. For this reason all iron should be excluded from the coils in the resonant circuits and solid dielectrics should not ordinarily be employed in the condensers. These injunctions apply to the construction of circuits made resonant.

to very high frequencies, but not with the same force to the construction of circuits to be resonant to low frequencies. Another precaution to be takenin the construction of the apparatus included in the resonant circuits when very high frequency currents are employed is that conductors between which there exists considerable potential difference during the operation of the apparatus shall be kept as far apart as practicable, because of the excessive displacement-currents which tend to flow in the case of high frequencies.

.For this reason I so design the coils used in of vibration of the coil itself is made very great compared to the frequency to which the circuit in which the coil is included is made resonant.

Having described my invention, I claim- 1. In a system of selective electric signaling by means of electromagnetic Waves without connecting-Wires between the transmitting and receiving stations, means for independently impressing electric vibrations of different frequencies upon a single elevated conductor, comprising branch circuits conductively connected with said elevated conductor and made resonant each to one of said different frequencies.

2. In a system ofselective electric signaling by means of electromagnetic waves of different frequencies without connecting- Wires between the transmitting and receiving stations, a single elevated conductor in which the energy of the electromagnetic waves of the different frequencies is received, and branch circuits conductively associated with said elevated conductor-and made resonant each to one of said different frequencies.

3. In a system of selective elec'tricsignal ing by means of electromagnetic waves without connecting-wires between the transmitting and receiving stations, means forimpressing electric vibrations of a predetermined frequency upon an elevated conductor comprising at its lower end a circuit conductively connected with said elevated conductor and made resonant to the frequency of said electric vibrations p,

4. In a system of selective electricsignaling by means of electromagnetic waves or a definite frequency without connecting-wires between the transmitting and receiving stations, an elevated conductor in which the energy of electromagnetic waves of said definite frequency is received and a circuit conductively associated With said elevated conductor and made resonant to the frequency of said waves.

5. In a system of space telegraphy, a metallically continuous elevated conductor, comprising branch circuits conductively con:

nected with said elevated conductor and made resonant each to a different frequency.

6. In a system of space telegraphy, a metallically-continuous elevated conductor 00 m-' prising at its lower end a circuit conductively connected with said elevated conductor and maderesonant to a certain selected and predetermined frequency.

v 7. .In a system of space telegraphy, a metallically-continuous elevated conductor, serially connected with a plurality of closed resonant circuits, each attuned to a different frequency.

8. In a system of space tel'egraphy, a metallically-continuous elevated conductor, se-

rially connected with a closed resonant circuit attuned to a certain selected and predetermined frequency; 7 1

9. In a system of space telegraphy, an elevated'cond uctor conductively connected with a closed resonant circuit attuned to a certain selected and predetermined frequency.

10. In asystem of space telegraphy, means for generating electric energy of relatively means for transforming said energy into energy of high frequency and high potential and means for impressing or forcing saidenergy of high frequency and high potential upon a circuit conductively connected to an elevated.

conductor and made resonant to said high frequency.

11. In a system of space telegraphy, means for generating electric energy of relatively low frequency and relatively low potential,

low frequency and relatively low potential,

IIO

means for transforming said energy intoenergy of high frequency and high potential and means for impressing or-forcingsaid. energy of high frequency and high potential .upon a closed circuit conductively connected to an elevated conductor and made resonant to said high frequency. Y

12. In a system for developing electromag.

netic signal-waves, means for developing electric oscillations in a closed, persistently-omit. lating circuit having symmetrically-disposed sources of capacity and inductance and means for impressing or forcing said electric oscillations upon an elevated. conductor.

. 13. In a system for receiving'the energy of electromagnetic signalwaves an, elevated.

conductor and a closed circuit resonant to the frequency of the waves, the energy of which is to be received, and having symmetricallydisposed sources of capacity and inductance.

14. In a system for receiving the energy of electromagnetic signal-waves, a closed circuit resonant to the frequency of the waves, the energy of which is to be received, an electric translating device shunted around the terminals of one of the elements of said resonant circuit, a local circuit containing a battery and a signalindicating device in series with said electric translating device and aportion of said resonant circuit, and an electrolytic cell for preventing the normal closure of said local circuit while ofiering a low impedance to the high-frequency oscillations developed in the resonant circuit.

15. In a system for receiving the energy of electromagnetic signal-waves, a local circuit, containing a signal-indicating device and a battery, and an electrolytic cell for preventing the normal closure of said local circuit.

16. In a system for receiving the energy of electromagnetic signal-waves of a definite frequency, an elevated conductor comprising at its lower end a circuit conductively connected to said elevated conductor and resonant to the frequency of the waves the energy of which is to be received, and means for conveying the energy of the electric oscillations developed in said circuit to an electric translating device.

17. In a system for selectively receiving the energy of electromagnetic signal-waves of difierent frequencies, an elevated conductor comprising at its lower end a plurality of circuits conductively connected to said elevated conductor and resonant each to one of said different frequencies, and means for conveying the energies of the electric oscillations developed in said circuits, each to a separate electric translating device.

18. In a system for receiving the energy of electromagnetic signal-waves of a definite frequency, an elevated conductor comprising at itslower endaclosed circuit conductively connected to said elevated conductor and resonant to the frequency of the waves the energy of which is to be received, and means for conveying the energy of the electric oscillations developed in said circuit to an electric translating device.

19. In a system for selectively receiving the energy of electromagnetic signal-waves of different frequencies, an elevated conductor comprising at its lower end a plurality of closed circuits conductively connected to said elevated conductor and resonant each to one of said different frequencies, and means for conveying the energies of the electric oscillations developed in said circuits, each to a separate electric translating device.

20. In a system for developing electromagnetic signal-waves of a definite frequency, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to said definite frequency and means for developing in said circuit electric vibrations of corresponding frequency.

21. In a system for receiving the energy of electromagnetic signal-waves of a definite frequency, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, the energy of which is to be received, and a resonant circuit or a group of resonant circuits associated with the first-mentioned circuit and attuned to the same frequency as said circuit.

22. In a system for independently developing electromagnetic signal-waves of different frequencies, an elevated conductor comprising circuits conductively connected to said elevated conductor and made resonant each to one of said diderent frequencies and means for independently developingin each said circuit electric vibrations of the frequency to which it is attuned.

23. In a system for selectively receiving the energy of electromagnetic signal-waves of different frequencies, an elevated conductor comprising circuits conductively connected to said elevated conductor and made resonant each to the frequency of a different one of the trains of waves, the energy of which is to be received, and a resonant circuit or group of resonant circuits, each associated with one of the first-mentioned resonant circuits and each attuned to the same frequency as the circuit with which it is associated.

24. In a system for developing electromagnetic signal-waves of a definite frequency, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to said definite frequency, a source of electrical energy and the group of resonant circuits interposed between the first-mentioned resonant circuit and said source of electrical energy, said circuits being attuned to the frequency of the Waves to be developed.

25. In a system for receiving the energy of electromagnetic signal-Waves of a definite fre quen cy, an electric translating device, an elevated conductor comprisinga circuit conductively connected to said elevated conductor and resonant to the frequency of the waves, the energy of which is to he received, and a resonant circuit or a group of resonant circuits interposed between said electric translating device and the first-mentioned resonant circuit and attuned to the frequency of said waves.

26. In a system for selectively receiving the energy of electromagnetic signal-waves of different frequencies, an elevated conductor comprising a plurality of circuits conductively connected to said elevated conductor and made resonant each to the frequency of a different one of the trains of waves, the energy of which is to be received, and a plurality of resonant circuits, each associated with ICO IIO

a dilferent one of said first-mentioned resonant circuits and attuned to the same frequency as the circuit with which it is associated. v

27. In a system 'for developing free or unguided simple harmonic electromagnetic signal-waves of a definite frequency, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to said definite frequency and means for developing in said circuit forced simple harmonic electric vibrations of corresponding frequency.

28. In a system for receiving the energy of free or unguided simple harmonic electromagnetic signal-waves of a definite frequency, to the exclusion of the energy of signal-waves of otherfrequencies, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, theenergy of which isto be received.

29. In a system for receiving the energy of free or unguided simple harmonic electromagnetic signal-waves of a definite frequency, to the exculsion of the energy of signal-waves of other frequencies, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, the energy of which is to be received, and a resonant circuit or group of resonant circuits, associated with the first-mentioned circuit and attuned to the same frequency as said circuit.

30. In asystem for independently developing free-or unguided simple harmonic electromagnetic signal-waves of different frequencies, an elevatedconductor comprising circuits conductively connected to said elevated conductor and made resonant each to one of the said different frequencies and means for independently developing in said circuits forced simple harmonic electric vibrations of different and correspondingfrequencies.

31. In a system forselectivelyreceiving the energy of free or unguided simple harmonic electromagnetic signal-waves of different frequencies, each to the exclusion of the rest, an

elevated conductor comprising circuits conductively connected to said elevated conductor and made' resonant each to the frequency of a different one of the trains of waves, the energy of which is to be received.

32. In a system for selectively receiving the energy of free or unguided simple harmonic electromagnetic signal-waves of different frequencies, each to the exclusion of the rest,

'an elevated conductor comprising circuits mentioned resonant circuits and each attuned to the same frequency as the circuit with which it is associated.-

33. In a system for developing free and uu-' guided electromagnetic signal-waves of adefiof the waves to be developed.

34. In a system for receiving the energy of free or unguided simple harmonic electromagnetic signal-waves of one frequency to the exclusion of the energy of signal-waves of other frequencies, an electric translating device, an elevated conductor comprising a circuit conductively connected tosaid elevated conductor and' resonant to the frequency of the waves, theenergy of which is to be received, and a resonant circuit or a group of resonant circuits interposed between said electric translating device and the first- 'mentioned resonant circuit and attuned to the frequency of said waves.

35. In a system for selectively receiving the energy of free or unguided simple harmonic electromagnetic signal-waves of different frequencies, each to the exclusion of the rest,

an elevated conductor comprising a plurality of'circuits conductively connected to said elevated conductor and made resonant each to the frequency of a different one of the trains of waves, the energy of which is who received, and a plurality of resonant circuits, each associated with a different one of said first-mentioned resonant circuits and attuned to the same frequency as the circuit with which it is associated.

36. In a system for developing free or unguided simple harmonic electromagnetic sig- 7 nal-waves, a condenser, means for charging and discharging said condenser through a closed circuit having inductance adapted to produce under such conditions simple harmonic electric vibrations, andmeans for communicating the vibrations so. produced to an open circuit or elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to said vibrations.

37. In a system for developing free or unguided, simple harmonic,electromagnetic signal-waves, a condenser, means for charging and discharging said condenser througha closed circuit having inductanceadapted to produce under such conditions simple harmonic electric vibrations, means for communicating said vibrations to a' resonant circuit or group thereof attuned to the'frequency of these vibrations and means for communicat-' ing the resulting electric vibrations in said resonant circuit or group thereof to an open circuit or elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of said-vibrations.

88. In a system for developing free or unguided, simple harmonic, electromagnetic signal-waves, a condenser, means for charging and discharging said condenser through a closed circuit having symmetrically-disposed sources of inductance adapted to produce under such conditions simple harmonic electric vibrations, and means for communicating the vibrations so produced to an open circuit or elevated conductor.

39. In a system for receiving the energy of electromagnetic signal-waves, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, the energy of which is to be received, and an electric translating device forming one of the tuning elements of a second resonant circuit, associated with the first-mentioned resonant circuit and attuned to the same frequency as said circuit, said electric translating device being adapted to utilize in its operation the energy of the electric oscillations developed in said second resonant circuit.

40. In a system for receiving the energy of electromagnetic signal-waves, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, the energy of which is to be received, and an electric translating device adapted to utilize in its operation the energy of the oscillations developed in a second resonant circuit, associated with the first-mentioned resonant circuit and attuned to the same frequency as said circuit.

41. In a system for receiving the energy of electromagnetic signal waves, an elevated conductor comprising a circuit conductively connected to said elevated conductor and made resonant to the frequency of the waves, the energy of which is to be received, and an electric translating device forming one of the tuning elements of a second resonant circuit, associated with the first-mentioned resonant circuit and attuned to the same frequency as said circuit.

42. In a system for receiving signals transmitted by electromagnetic waves, an electric translating device constituting one of the tuning elements of a closed resonant circuit and adapted to utilize in its operation, the energy of the magnetic component of the electric oscillations developed in said resonant circuit, said resonant circuit being attuned to the frequency of the transmitted waves.

43. In a system for receiving signals transmitted by electromagnetic waves, an electric translating device constituting one of the tuning elements of a closed resonant circuit and adapted to utilize in its operation, the kinetic energy of the currents developed in said resonant circuit, said resonant circuit being attuned to the frequency of the transmitted waves.

4:41. In a system for receiving signals transmitted by electromagnetic Waves, the combination of a closed resonant circuit attuned to the frequency of the transmitted waves and an electric translating device constituting one of the tuning elements of said closed res-- onant circuit and adapted to utilize in its operation the kinetic energy of the electric os-- cillations developed therein.

45. In a system for receiving signals transmitted by electromagnetic waves, the combination of a closed resonant circuit attuned to the frequency of the transmitted waves and an electric transmitting device adapted to utilize in its operation the kinetic energy of the currents developed in said closed resonant circuit.

46. In a system for receiving signals transmitted by'electromagnetic waves, the combination of a closed resonant circuit attuned to the frequency of the transmitted waves and an electric transmittiu g device adapted to utilize in its operation the energy of the magnetic component of the electric oscillations developed in said closed resonant circuit.

47. In a system for receiving signals transmitted by electromagnetic waves, the combination of a closed resonant circuit attuned to the frequency of the transmitted waves and a metallically-continuous electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said resonant circuit.

48. In a system of space telegraphy, the combination of means located at a sendingstation for radiating electromagnetic waves, an elevated conductor at a receiving-station, a closed circuit resonant to the frequency of the waves, the energy of which is to be received, associated with said elevated conductor, an electric translating device adapted to directly translate the energy of the currents developed in said closed resonant circuit by the electromagnetic waves into the energy of motion, and means for observing such motion. 49. In a system for absorbing the energy of electromagnetic waves of one frequency to the exclusion of the energy of like waves of a different frequency, a closed circuit resonant to the frequency of the waves, the energy of which is to be absorbed, and an electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said closed circuit.

50. In a system for absorbing the energy of simple harmonic electromagnetic waves of one frequency to the exclusion of the energy of like waves of a different frequency, a closed circuit resonant to the frequency of the waves, the energy of which is to be absorbed, and an electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said closed circuit.

51. In a system for the transmission of energy by electromagnetic waves of a certain predetermined frequency, a transmitting system comprising a sonorous or closed persistently oscillating circuit conductively connected to an elevated conductor, said system being adapted to radiate electromagnetic to to the frequency of the transmitted Waves,

and an electric translating device adapted to utilize in its operation the kinetic energy of the electric currents developed in said closed circuit.

i 53. In a system'for'receiving the energy of electromagnetic waves, an elevated conductor containing the primary of a transformer, an electric translating device in series with a closed resonant circuit and adapted to utilize in its operation the kinetic energy of the currents developed in said closed resonant circuit, and a second closed resonant circuit inductively related to the primary of said transformer and the first-mentioned closed resonant circuit, said circuits being resonant to the frequency of the transmitted Waves.

54. A system of signaling by electromagnetic waves having in combination therewith a closed circuit resonant to the frequency of 0 the electromagnetic Waves to which it is desired to respond and an electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said closed circuit. 55. In a system of signaling byelectromagnetic waves, the combination of a closed resonant circuit, attuned to the frequency of the transmitted waves, and an electric translat ing device adapted to utilize in its operation 0 the kinetic energy of the currents developed in said resonant circuit and to give indications proportioned to the total energy developed therein.

56. In a system of signaling by electromag- 5 netic waves, an apparatus for utilizing the energy of said waves, said apparatus including in combination an elevated conductor for absorbing the energy of said waves whereby electric currents are developed therein by each wave, means for conveying or translating said electric currents to a closed circuit, resonant to the frequency of the transmitted waves, whereby the current-flow is caused to be persistent and the currents developed by i 5 successive waves are coordinated so that they act cumulatively upon each other and produce an increased or reinforced resultant current-flow, and means operated by said resultant current-flow to produce a sensible etfeet or indication.

57. Ina system of signaling by electromagnetic Waves, a closed circuit resonant to the frequency of the electromagnetic waves,'the energy of which is to be received, and a constantly-receptive electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said resonant circuit.

58. In a system of signaling by electromagnetic waves, a closed circuit resonant to the frequency of the waves, the energy of which is to be received, and a constantly-receptive, self restoring electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said resonant circuit.

59. In a system of signaling by electromagnetic waves, a closed circuit resonant to the frequency of the waves, the energy of which is to be received,'and a self-restoring electric 8o translating device adapted to utilize in its operation the kinetic energy of the currents developed in said resonant circuit.

60. In a system of signaling by electromagnetic waves, a closed circuit resonant to the frequency of the electromagnetic waves, the energy of which is to be received, and a constantly-receptive electric translating device adapted to utilize in its operation the kinetic energy of the currents developed in said reso- 9o nant circuit, in combination with a source of Y maintained or persistent electromagnetic ranetic waves, a closed circuit resonant tothe 1o5 frequency of the electromagnetic Waves, the energy of which is to be received, and a selfrestoring electric translating device adapted to utilize in its operation the kinetic energy of the current developed in said resonant cir- 1 1o cuit in combination with a source of maintained or persistent electromagnetic radiation at a sending-station.

In testimony whereof I have hereunto subscribed my name this 31st day of July, 1902.

JOHN STONE STONE.

Witnesses;

CHARLES C. KURTZ, v ELLEN B. TOMLINSON.

It is hereby certified that in Letters Patent No. 737,170, granted August 25, 1903, upon the application of John Stone Stone, of Cambridge, Massachusetts, for an improvement in Apparatus for Selective ElectrieSignalling, errors appear in the printed specification requiring correction, as follows: In line 6, page 8, the word constance 2 m, and in line 50, page 7, fi\4 should read 7H4; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of December, A. D., 1903.

, 2 should read constants; in line 35, page 6, the fOrmuIa shOuldread F. I. ALLEN, Commissioner of Patents.

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