US755586A

US755586A - Method of selecting electrical impulses.

Info

Publication number: US755586A
Application number: US16515203A
Authority: US
Inventors: Daniel Watts Troy
Original assignee: Individual
Current assignee: Individual
Priority date: 1903-07-11
Filing date: 1903-07-11
Publication date: 1904-03-22
Anticipated expiration: 1921-03-22

Description

10 MODEL.

PATENTBD MAR. 22, 1904.

. D. W. TROY. METHOD OI SELECTING ELECTRICAL IMPULSES.

APPLIOATION FILED JULY 11, 19Q3.

ions i UNITED STATES Patented lVlIarch Q2, 1904.-

PATENT OFFICE.

METHOD OF SELECTING ELECTRICAL IMPULSES.

SPECIFICATION forming part of Letters Patent No. 755,586, dated March 22, 1904.

Application fi1ed m 11, 1903.

My invention relates to the selection of electrical impulses according to their frequency,

selection beingrunderstood to mean the operation of receptive apparatus by impulses of a certain frequency or frequencies and the nonoperation of such apparatus by impulses of other or foreign frequencies. The method contemplates, in effect, both selection and noninterference, if the two can be considered a separable.

. The object of my invention is to provide an eflicient and reliable method for securing such selection for use in multiplextelegraphy over wires, selective telephony on party-lines,wire- Fig. 3, still another.

less or space telegraphy, and the wireless control of apparatus at a distance, such as torpedoes, or, in fact, any apparatus desired to be controlled by electrical impulses; and the object, is further, to obtain such selection for any purposes where desirable.

In the drawings, Figure 1 is one form of receiving instrument; Fig. 2, another form; Fig. 4 is a detail of a modification of Fig. 1, and Fig. 5 is an electrostatic application of the method.

I am familiar with the method of electrically tuning receiving-conductors used in wireless telegraphy; but my system has nothing in common with such method, except that it maybe used to advantage therewith. I am also familiar with the methods used by Prof'essor Fessenden, in which currents produced in receiving-conductors are divided by phasesplitting means related to the frequency of the transmitter from which it is desired to select' and in which an operative phase difference of one hundred and eighty degrees is used in the instruments; and I am also familiar with his system of transmitting simul- Serial N0. 165,152. (No model.)

' taneously out-of-phase waves and receiving them by tuned receivers and with his system of receiving by beats produced by two transmitted sets of waves of different periodicity. In my system, however, there is a distinct and radical difference from those above named in that my receiving instruments are not merely most responsive when energized by waves of the frequency desired to be selected, but are only responsive when energized by Waves of such frequency or, as extreme delicacy might be required to select to the exact frequency, are responsive only to a closely-related range of frequencies-say frequency N and a few frequencies below and above N or approximately frequency N.

In my method I split the phase of currents produced by the waves in receiving-conductors or split the phase of alternating currents, as the case may be, and then operate by such out-of-phase currents so produced receptive apparatus-operative only within a given frequency range, approximately frequency N. With the device shown in Fig. 3 the selection is practically to frequency N. I

Generally the method contemplates a receiving instrument operative only at a given phase displacement in the energizing-currents, and this condition is realized by causing a brake efiiectupon biphase apparatus by a portion of the received energy, except at the maximum efficiency of the receptive apparatus, when the brake is overcome I Referring to the drawings,'Fig. 1 shows a receiver in the form of a rotary field-motor,

1 l being a pair of field-coils and 2 2 being a second pair at right angles to the first pair. 10 is the armature or rotor embraced by such coils, (though it is obvious that either rotor or fieldcoils may be the movable member.) Said field-coils are supplied, respectively, in shunt relation from areceiving-conductor 5 through phasedisplacing means in one branch 7 (an inductance) and through another phasedisplacing means 8 (a condenser) in the other branch. 7 and 8 are so related as to cause a difi'erence of phase in the currents in the two pairs of field-coils of ninety degrees at frequency N. It is obvious that without further modification such a receiver would respond in degree to any reasonable frequency. To render the mstrument lnoperative at for eign frequencies, an electromagnetlc brake is provided, consisting of a pair of approxi,

mated flat coils 9 and 9, one of which is rigidly connected to the movable member of the motor and the other fixed on the base of the instrument or otherwise. Either the whole or a part of the received energy is directed through such brake-coils in series or in parallel, and such coils are so proportioned, adjusted, or related to the power factor of the motor as to normally overpower it except at the maximum power for unit current of such motor. A local circuit 11 12 13, embracing indicating mechanism as a sounder, is adapted to be made operative whenever the motor overpowers the brake. In such a motor the maximum torque (practically the standstill torque) per'unit current will be when the condition of a circular magnetic field is reached viz., at aphase-angle of displacement equal to the coil-angle, or ninety degrees in both. In the further discussion it may be assumed that unit current is being transmitted through the coils and that means, such as resistance and the like, are provided to render the energizing-currents equal or their effects equal when out of phase the proper amount. It is obvious that a greater or less coil-angle would require a corresponding phase-angle for the condition of maximum efliciency, and in the case where several such motors were operated at one station one set of phase-displacing means might be used to supply several mo. tors.

It is obvious, further, that other means of producing an operative phase difference might be used, and it is evident that any known means-such as microphonic contacts, mirrors, or other devicesmay be used to advantage to indicate motion of the rotor or movable member of such motor instead of the means shown in Fig. 1. It is possible as a variation of this method that two such motors be placed in opposition, the power factor of the one varying practically with that of the other, except at and near the maximum of one, when the one having the higher maximum would overpower the other.

In Fig. 2 two brake or iii-phase coils 15 15 are shown similar to 9 9 and are opposed by two out-of-phase coils 16 16. Such outofphase coils are energized as follows: By a proper capacity 17 a lead of forty-five degrees is produced in 16 over the received current, while a lag of forty-five degrees is produced in the other branch of the split, as before, by inductance 17, (frequency N being assumed.) 16, however, is not energized directly from the lagging branch, but by a transformer 18,

having its primary energized by such lagging current. As the current in the secondary of the transformer would be lagging behind that of the primary by, say,-ninety degrees, a total-lag of one hundred and thirty-five degrees degrees out of phase, produced as above de scribed, and they are oppositely wound, as contemplated, they will have similar directional currents and will mutually attract, and

if given a mechanical advantage over theinphase or brake coils at such stage will cause movement of the light lever 20, supporting coils 15 and 16. At all other frequencies the iii-phase coils will prevent such motion and hold the lever down against the stop 22, (shown to the left of the fulcrum 21.) Movement of .the lever can be indicated by a mirror 23 or otherwise. It is obvious that only at one frequency will the

coils

16 and 16 have their maximum efiiciency, and it is possible by such means to select within a very narrow range of frequencies related to the maximum effect of the out-of-phase coils.

In Fig. 3, 34 is a reed of fixed rate N. 35 is a coil fixed on the free end of suchreed. 35 is a similar coil on the base of the instru: ment. 35 and 35 are supplied, respectively, with currents difiering in phase ninety degrees at frequency N the means being the same hereinbefore described and related to the frequency 1 2 desired to be selected. It is obvious that coils 35 and 35' will twice mutually attract and twice mutually repel during each cycle of the current at frequency N and such attractions and repulsions will be equally timed and alternated at such frequency. Should the frequency be lower than N there will not be a quarter-phase displacement, and consequently such operative impulses will not be equally timed, nor will the impulses be timed with the rate of the reed and the apparatus will be inoperative. A higher frequency than N will'also be inoperative for the same reasons. Instead of

coils

35 and 35 conductingdisks may be used instead and the electrostatic attractions and repulsions used instead of the electromagnetic effects. Combined with an electric tuning system this method of operating avibratory receiver insures a threefold safeguard against foreign rates.

Fig. 5 shows an electrostatic modification of Fig. 2, in which conducting-disks 40 and 40 are normally overpowered by other similar disks 41 and ll, the last pair energized by means similar to those shown in Fig. 2. Q5 is a light lever supporting the upper disks upon a fulcrum 4:6. The operation is analogous to that of Fig. 2 and needs no explanation.

Fig. 4 shows a microphonic contact 50, consisting of a cam on the axis of the rotor 10 and bearing on a carbon block 53. By this means variations of local currents may be utilized to indicate motion of the rotor. The microphonic method of indicating operative movement may of course be applied to others of the types of instruments shown herein.

Variations of the electromotive force, on account of the utilization of a part of the received energy to operate the brake, will not prevent the selective action, as stronger impulses prod uce related brake efiects. It is obvious that reed as herein used does not necessarily mean a fixed vibratory member, as the same operative effect can be obtained with apparatus controlled in any manner so as to produce a fixed mechanical rate of vibration. So far as I am aware split-phase current impulses have not been used to any extent in ordinary telegraphy over wire circuits or in selective telephony, and as far as I am advised the only use of split-phase devices in wireless or space telegraphy is where apparatus is made thereby more sensitive to a certain frequency of waves, though not in any sense sensitive only to a given frequency as I contemplate. It should be noted that an instrument operative only by electrical impulses of given frequency is an instrument inoperative by impulses of other frequences and not merely operative to less extent by the foreign fre quencies.

I do not confine myself in my method of selection to cases where the out-of-phaseness of currents is the governing feature by producing greatest power at such a phase difference as may be desired, for it is obvious that apparatus of a dilferential nature might be constructed where the out-of-phaseness would be manifest as a reactance merely and not operate to produce a rotating magnetic field or to produce the timed intervals necessary in my reed-controlled instruments.

In the claims following I mean by electrical impulses all kinds of electromagnetic or electrical waves capable of producing currents in receiving-conductors;

With very high frequencies it is obvious that it would be impracticable to use motorcoils in the receivers with high self-inductive coeflicients, for at such very high frequencies the energy would be choked out of the currents by coils of many turns. At lower frequencies, however, such as in some of the applications noted herein, there need not necessarily be a destructive reactance in the coils,'as shown. Itis of course intended in all cases that the phase-lagging coil be proportioned to the frequency desired to be selected and might and could in extreme cases take the form of a single turn. The reactance of this coil would be only such as to cause the desired phase displacement and would not choke out energy or render the It is obvious, of course, in view of the well-' known phenomena of alternating or wave-like currents of electricity, that phase difierences can be produced in a variety of ways not particularly pointed out herein.

Having described my invention, what I claim is 1. The method of selection herein set forth, consisting in causing a ,phase difl'erence between currents produced by electromagnetic waves in receiving-conductors by means at the receiving station related to and capable of causing a given phase difference at the frequency ofthe waves desired to be selected, and energizing by the phase-differing currents so produced responsive apparatus operative only at substantially such given phase difference.

2. The method of selecting electrical impulses herein set forth consisting in causing a phase difference between currents produced by such impulses in receiving-conductors by means at the receiving-station related to and capable of causing such phase difference of given degree at the frequency of the impulses desired to be selected, and energizing by such phase-differing currents so produced responsive apparatus operative only at a phase difference of approximately such given degree, substantially as set forth.

3. The method of selecting electrical impulses herein set forth, consisting in causing a phase difference between currents produced by such impulses in receivin -conductors by means at the receiving-station related to and capable of causing at the frequency of the impulses it is desired to select a given phase difference, and directing such outof-phase currents so produced respectively in shunt relation through independent windings of apparatus operative only at approximately such phase difference between currents in said windings, substantially as set forth.

at. The method of selecting electrical impulses herein set forth, consisting in causing a phase difierence between currents produced in receiving-conductors by such impulses by ratus except approximately at the maximum mechanical force ofsuch apparatus, substantially as set forth. I

5. The method of selection herein set forth, consisting in causing a phase difference between currents produced in receiving-conductors by electrical impulses by means at the receiving-station related to and capable of producing a given phase difference at the frequency of the impulses it is desired to select, and by directing such. phase-differing currents so produced respectively in shunt relation through independent windings of biphase responsive apparatus, producing a mechanical force passing through a maximum at a given phase difference between currents in said windings, and energizing by currents produced by such impulses a stop device operative against said responsive apparatus except at approximately such maximum, substantially as set forth.

6." The method of selecting electrical impulses consisting in causing a phase difference in currents produced in receiving-conductors by means at the receiving-station related to and capable of producing at the frequency of the impulses which it is desired to select a given phase difference, and by energizing by such out-of-phase currents s0 produced biphase responsive apparatus, producing a mechanical force passing through a maximum at a certain phase difference between such phase-differing currents so produced, and energizing by means of currents produced by such impulses a stop mechanism operative against said responsive apparatus except at approximately such maximum, substantially as set forth.

7. The method of selecting electrical impulses hereinsetforth consisting in receiving such impulses by conductors electrically tuned to the frequency of the transmitter from which it is desired to select, causing a phase difference in currents produced in receiving-conductors by such impulses by means at the receiving-station related to and capable of producing at the frequency of the transmitter from which it is desired to select a given phase dilference in such currents, and, by energizing biphase responsive apparatus with such out-of-phase currents so produced, producing a mechanical force varying with a factor of the phase difference of such currents and passing a maximum at the phase diiierence corresponding to the frequency of such transmitter, and energizing by currents produced by such impulses astop mechanism operative against such responsive apparatus except at approximately such maximum, substantially as set forth.

8. The method of selecting electrical impulses herein set forth consisting in receiving such impulses by electrically-tuned conductors, producing a phase difference between currents produced by such impulses in such conductors by means at the receiving-station related to and capable of causing such phase difference of given degree at the frequency of the impulses desired to be selected, and energizing by such phase -differing currents so produced responsive apparatus operative only at a phase difference of approximately such given degree substantially as set forth.

9. The method of selecting electrical impulses, received by electrically-tuned conductors at the receiving-station, and energizing current-operative biphase-responsive appara tus, consisting in producing by means of currents produced by such impulses a stop effect on such responsive apparatus except at approximately a given frequency, substantially as set forth.

10. The method of selecting electrical currents of wave character consisting in energizing by such currents in shunt relation responsive apparatus of biphase character, and, by phase-displacing means related to the frequency of the current desired to select, producing a mechanical force in such apparatus varying with a factor of phase diflerence be tween its windings, and energizing by such currents a stop mechanism operative against such apparatus except at approximately such maximum, substantially as set forth.

11. The method of selecting alternating, pulsatory or oscillatory currents consisting in splitting the phase of such currents at the receiving-station by means related to the frequency of the current desired to be selected and directing the phase-differing currents so produced in shunt relation through independent windings of a motor operative only when such currents have approximately a given phase difference, substantially as set forth,

12. The method of selecting herein set forth consisting in directing alternating currents by independent paths in shunt relation through separate windings of biphase-currentrespon sive apparatus operative only at substantially a given phase difi'erence between the currents in its windings and producing an operative phase diflerence in said windings by means related to the frequency of the current to be selected, substantially as set forth.

13. The method herein set forth consisting in directing wave-produced currents by separate paths in shunt relation through independent windings of biphasecurrentrespon sive apparatus operative only at approximately a given phase difierence in such windings and producing an operative phase difference by means related to the frequency of the waves desired to be selected, substantially as set forth.

14:. The method herein set forth consisting in splitting the phase of wave-produced currents by means at the receiving-station related to and capable of causing a given degree of phase difference at the frequency of the waves desired to be selected, and energizing by the components of such split-phase currents apparatus of biphase character operative only at approximately such given degree of phase difference, substantially as set forth.

15. The method herein set forth, consisting in splitting the phase of wave-produced currents by means related to the frequency of the waves desired to be selected, energizing by the components of such split apparatus of biphase character and preventing by currentoperated brake mechanism any movement of such apparatus except at a certain phase clifference in such components, substantially as set forth.

16. The method of selecting electrical Waves herein set forth consisting in splitting the phase of Wave-produced currents at the receivingstation by means capable of producing a given degree of phase difference at a given frequency, and energizing by the resulting phase-differing components responsive apparatus operative only at a phase difference of substantially such given degree, substantially as set forth.

17. The method herein set forth, consisting in dividing the energy of received electromagnetic waves, producing by a portion of such energy a force varying with a function of the frequency and producing by the other portion of such energy an oppositely-acting force less than the first only at substantially a given frequency of such waves, substantially as set forth. v y

18. The method of selection of electric waves herein set forth, consisting in producing by a portion of the energy of such waves a force varying with a function of their frequency and producing by another portion of the energy of such Waves another and oppositelyact ing force less than the first only at approximatelya given frequency of such Waves, substantially as set forth.

19. The method of selection herein set forth consisting in energizing a rotary field-motor by split-phase components of wave-produced currents and preventing the operation of such motor except at its maximum efliciency'by a brake operated by Wave-produced currents substantially as set forth. p

20. The method herein set forth consisting in splitting the phase of wave-produced currents at the receiving-station by means capable of producing a phase difference of given degree at a given frequency, and energizing by the components so produced apparatus operative at a phase difference between such components of substantially such given degree, substantially as set forth. 7

21. The method herein set forth consisting in opposing forces produced by wave-produced currents and by means at the receivingstation related to the frequency of the waves desired to be selected causing an operative difference in such forces only at approximately such frequency, substantially as set forth.

energy of electromagnetic Waves a force vary ing with a function of the frequency and producing by the remaining portion of such energy an opposing force less than the firstonly at substantially a given frequency, substantially as set forth.

24C. The method herein set forth, consisting in receiving electrical impulses by electrically-tuned conductors at the receiving-station,

opposing forces produced by currents caused by such impulses, and, by means related to the frequency of the waves desired to be se lected, causing an operative difference between such forces only at. substantially such frequency, substantially as set forth.

25. The method herein setforth consisting in combining selection by electrical syntony with selection by opposing forces produced by Wave-produced currents, and by means related to a given frequency causing an operative difference between such forces only at substantially such frequency, substantially as set forth.

26. The method of selection herein set forth consisting in producing from a portion of the divided energy of electric Waves a force having a maximum at substantially a given frequency, and from the other portion of such energy another force less than the first at such maximum, substantially as set'forth.

27. The method of selection herein set forth consisting in dividing the energy of received electrical impulses and normally nullifying the action of the one portion of such energy by the other portion except at substantially a given frequency of the received impulses, substantially as set forth.

28. The method of selection herein set forth consisting in dividing the energy of received 1 energy to normally nullify the action of the remaining portion except at substantially a given frequency, substantially as set forth.

30. The method herein set forth consisting in producing by means related to the frequency of the impulses desired tobe selected a phase difference between components of the received impulses and energizing by such components apparatus operative only at substantially a given phase difference between such components, substantially as set forth.

31. The method herein set forth consisting in splitting the phase of received electrical impulses by means related to the frequency of the impulses desired to be selected and energizing by the phase-diflering components so produced apparatus responsive only at substantially a given phase difference between such components, substantially as set forth.

32. The method herein set forth consisting in receiving electrical impulses by conductors electrically tuned to the transmitter, and opposing forces produced bysuch impulses,and, by means related to a given frequency, causing an operative difference between such forces only at substantially such frequency, substantially as set forth.

33. The method herein set forth consisting in receiving electromagnetic waves by conductors electrically tuned to a given frequency and utilizing a portion of the energy of received electrical impulses to normally nullify the action of the remaining portion of such energy except at substantially such given frequency, substantially as set forth.

34:. The method herein set forth consisting in dividing the energy of syntonicallyre ceived electrical. impulses and producing by one portion of such energy a force varying with a function of thefrequency, and having a maximum at a given frequency, and producing from theremaining portion of such energy a force less than the first only at substantially such given frequency of said impulses, substantially as set forth.

35. The method herein set forth consisting in energizing a rotary field-motor by splitphase components of an alternating current and preventing the operation of such motor except at its maximum efficiency by a brake operated by such current, substantially as set forth.

36. The method herein set forth, consisting in dividing the energy of received electromagnetic waves and opposing one portion of such' energy against the other, and, by means related to a given frequency, producing an operative difierence only at substantially such ireqklliency of such waves, substantially as set ort 37 The method herein set forth consisting in mutually opposing portions of the energy of received electromagnetic; waves and by means related to a given frequency of such waves producing an operative difference only at substantially such given frequency, substantially as set forth. 7

38. The method herein set forth, consisting in receiving electromagnetic waves by syntonically-tuned conductors; mutually opposing portions of the received energy, and, by means at the receiving-station, producing an operative difierence between such portions of such energy only at approximately a given frequency of such waves, substantially as set forth.

39. The method of selection herein set forth, consisting in causing one portion of the received energy of electrical impulses to nullify the action of the remaining portion except at substantially a given frequency of such impulses, substantially as set forth.

40. The method herein set forth consisting in causing one portion of the received energy of electrical impulses to act against the remaining portion of such energy and so produce an inoperative power factor from the. received energy except at substantially a given frequency of such impulses, substantially as set forth.

L1. The method herein set forth, consisting in combining with selection by electrical resonance selection by causing one portion of the received energy of electrical impulses to normally nullify the action of the remaining portion of such energy except at substantially a given frequency of such impulses, substantially as set forth.

L2. The method herein set forth consisting in mutually opposing portions of the energy of syntonically-received electromagnetic waves, and by means related to a given frequency, producing an operative difference between such portions only at substantially such given frequency, substantially as set forth.

43; The method herein set forth consisting in combining selection by electrical syntony with selection by causing one portion of the energy of received electrical impulses to nullify the action of the remaining portion of such energy except when such received impulses have approximately a given frequency, substantially as set forth.

4:4. The method herein set forth, consisting in causing a phase difference between components of received impulses and energizing by such phase-differing components apparatus operative only at substantially a given frequency, substantially as set forth.

L5. The method herein set forth, consisting in modifying by reactances the power factor of components of received impulses and energizing by such modified components a responsive device operative only at substantially a given frequency of such impulses, substantially as set forth. a

4:6. The method herein set forth, consisting in modifying by respective reactances the power factor of components of received impulses and energizing by such respectively modified components responsive apparatus operative only at substantially a given fre quency of such impulses, substantially as set forth. 1

4:7. The method herein set forth, consisting in dividing the received energy of electrical impulses and modifying the power factors of the components of the division, and energiz ing by such modified components apparatus operative only at substantially a given modification of such components, substantially as set forth.

48. The method herein set forth, consisting in causing phase differences between components of received impulses and energizing by such phase-differing components apparatus responsive only at substantially a given phase difference between such components, substan tially as set forth.

4:9. The method herein set forth, consisting in causing, by means related to a given fre quency, a phase difference between components of received impulses, and energizing by 7 queney producing an operative differe in pulses have substantially a such phase-differing components apparatus} responsive only at substantially such given frequency, substantially as set forth.

50. The method herein set forth, consisting in causing, by means related to a given frequency, modifications in the power factor of divided components of received impulses. and energizing by such divided components apparatus operative only at substantially such given frequency, substantially as set forth.

51. The method herein set forth, consisting in producing varying power factors in respective components of received impulses and energizing by such components apparatus responsive only at substantially given power factors of such components, substantially as set forth.

52. The method herein set forth, consisting in varying the power factors of components of the energy of received impulses and energizing by such components apparatus opera tive only at substantially a given diiference between the power factors of such components, substantially as set forth.

53. The method herein set forth consisting in producing two energy components from received impulses, opposing one against the other, and by means related to a given frethe record of the case in the Patent Office.

such energy components only when sIlQ given frequq ya substantially as set forth.

51. The method herein set forth consisting in producing more than one energy compo: nent from received power factor of such components respectively and independently, and energizing by such components apparatus operative only at substantially av given frequency of such impulses, substantially as set forth.

55. The method herein set forth consisting in modifying by separate reactances the phase of energy components of received electrical impulses and energizing by such phase-modified energy components apparatus operative only at substantially a given amount of phase modification in such components, substantially as set forth.

56. The method herein set forth consisting in energizing bi phase apparatus operative only at substantially a given phase difference by separate energy components of received electrical impulses and by means related to a given frequency causing a phase difference between such energy components, substantially as set forth.

5?. The method herein set forth consisting in causing phase-differing components from received impulses and energizing thereby re sponsive apparatus operative only at substantially a given phase difference between such components, substantially as set forth.

In witness whereof I have hereunto signed my name at New York, N. Y., the 8th day of ARCHIE HALL,

EDWARD S. HULL.

It is hereby certified that in Letters Patent N 0. 755,586, granted March 22, 1904, upon the application of Daniel Watts Troy, of New York, N. Y., for an improvement in Methods of Selecting Electrical Impulses,

errors appear in the printed specification requiring correction, as follows: In lines 100, 102, 105, 108, 113, page 2, the referencedetter and numeral N should read N /2; and that the said Letters Patent should be read with these corrections therein that the same may conform to [SEAL.] Y

E. B. MOORE,

Acting- Commissioner of Patents.

impulses, varying the operative only at substantially a given modification of such components, substantially as set forth.

EDWARD S. HULL.

E. B. MOORE,

Acting- Commissioner of Patents.

impulses, varying the the record of the ease in the Patent Ofiice.

It is hereby certified that in Letters Patent No. 755,586, granted March 22, 1904, upon the application of Daniel Watts Troy, of New York, N. Y., for an improvement in Methods of Selecting Electrical Impulses,

cation requiring correction, as follows:

errors appear in the printed specifi- In lines 100, 102, 105, 108, 113, page 2, the

should read N /2; and that the said Letters Patent should he read with these eorrecti reference letter and numeral N' ons therein that the same may conform to Signed and sealed this 24th day of May, A. D., 1904.

[SEAL] E. B. MOORE,

Acting Commissioner of Patents.