US778177A - Telegraphy. - Google Patents

Description

No. 778,177. PATENTED DEC. 20', 1904.

T. B. DIXON.

TELEGRAPHY.

APPLICATION FILED APR. 22, 1902.

2 SHEETS-SHEET 1.

N0 MODEL.

E E W/TNESSES: A & INVENTOI? I v 1 V ATTORNEYS I PATENTEDYDEG. 20, 1904. 'T. B. DIXON.

TELEGRAPHY.

APPLICATION FILED APR. 22, 1902.

2 SHEETS-SHEET 2.

N0 MODEL.

'- W/TNESSES;

, INVENTOH 7 a TTORNEYS Patented December 20, 1904.

PATENT OFFICE.

THOMAS B. DIXON, on NEW YORK, iv. Y.

TELEGRAPHY.

SPECIFICATION forming part of Letters Patent No. 778,177, dated December 20, 1904. I Original application filed October 11, 1898, Serial No. 693,205. Divided and this application filed April 22, 1902. Serial lie-104,154.

.To a whom it may concern:

va citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telegraphy; and I do hereby declare the followingto'be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to' make and use the same.

My invention relates generally to signaling systems, and particularly to improvements in systems of multiplex telegraphy whereby a plurality of distinct and separate messages may be transmitted simultaneously over a single wire or conductor or over a submarine cable.

My invention, resides in a novel system of transmitting two telegraphic messages simultaneously in the same direction over a single line wire or, conductor, which may be combined with other well-known systems of duplex telegraphy, so as to permit the simultaneous transmission of an equal number of messages in the opposite direction.

The objects of my invention are, first, to improve multiplex signaling systems, and particularly multiplex systems of telegraphy, and render it possible to operate such multiplex systems over longer lines and with greater rapidity than has been practicable with former systems, to avoid all interference between the messages transmitted, and to avoid interference with the transmission due to leakage, mutilation of signals, induction, and similar disturbing causes; second, to render it practicable to transmit two messages simultaneously in the same direction and an equal number of messages in the opposite direction over long submarine-cable lines, which cannot be done with the systems of multiplex telegraphy now in use on such lines, and, third, to make the system assimple as possible.

These objects are attained in the systems of signaling, particularly adapted for telegraphic signaling, herein described, apparatus and circuits for which are illustrated in the drawings which accompany and form a part of this specificatlon. v

In the drawings, Figure 1 is a diagram 1llustrating an arrangement of circuits and instruments for transmitting two simultaneous messages over a single line conductor in one direction. Fig. 2 is a diagram illustrating the arrangement of circuits and transmitting and receiving instruments at one end of a quadruplex line, the arrangement of circuits and transmitting and receiving instruments being similar to those shown in Fig. 1.

In the duplex and quadruplex telegraph systems herein described all of the signals are transmitted by pulsatory currents, each signal being transmitted by two pulses, one at the beginning and the other at the end of the signal. One transmitter atthe end of the line produces positive pulses only in the line, the other transmitter producing only negative pulses. spond to the said transmitters are operated one by positive pulses only and the other by, negative pulses only, each relay being changed from and restored to normal condition by alternate pulses of that polarity by which said relay may be operated.- Interference with the operation of the receiving instruments at one end of the line by the currents produced by the operation of the transmitting instruments at the same end of the line is prevented by any of the ordinary methods of duplex telegraphy.

Referring now to the drawings, and first of The two receiving-relays which re-' all to Fig. 1, which illustrates the, arrange- I ment of circuits and instruments for diplex telegraphy over land lines and short submarine-cable lines, A is a transmitting-station, and B a receiving-station, at opposite ends of a line-wire L. O and D are transmitting instruments, andE a selecting instrument, at the transmitting end of the line,'and F and Gare receiving-relays at the receiving end of the line. H and I are line batteries or generators oppositely connected to the line, so as to furnish thereto currents of opposite direction, andK a localbattery or generator of the transmitting-station which supplies current for circuits connecting the selectorE and the transmitting instruments O and D. Other batteries at the transmitting-station are local to the instruments to which they'are connected and will be mentioned hereinafter.

The function of transmitter C is to place battery H to the line for an instant at the beginning and again at the end of each signal sent through that transmitter, and similarly the function of transmitter D is to place battery I to the line momentarily at the beginning and again at the end of each signal sent through that transmitter. Since both batteries may not be connected with the line simultaneously without each neutralizing the effect produced by the other, the selector E is employed to give precedence automatically to one battery, placing the other battery to the line as soon as the pulse from the battery having preced enee is completed. The selector consists of a main or selecting relay. M and a vibrator N, itself composed of two polar relays 1 and 2, which alternately reverse each other, thus producing exceedingly rapid vibration of their armatures. The circuits of or controlled by selector E are as follows: The positive pole of battery K is connected to the armature 3 of the relay 1. To the two contact-stops of this armature are connected the local-circuit conductors 4E and 5, leading to opposing magnet-coils of relay 2 and thence to a returnconductor 6, leading to the negative pole of battery K. The one circuit or the other is complete according to with which contaet-stop the armature 3 makes contact at any instant.

To the armature 7 of relay 2 is connected the local-circuit conductor 8, connected to one set of coils of relay 1 and thence to batteries 9 and 10, oppositely placed, which are connected each to one of the contact-stops of armature 7. Circuit4 when complete tends to move armature 7 to the left, so as to complete circuit 8 through battery 9, and circuit 8 when completed through battery 9 tends to move the armature 3 of relay 1 to the right, so completing circuit 5. tends to move armature 7 to the right, so completing circuit 8 through battery 10, and since battery 10 is placed oppositely to battery 9 the completion of circuit 8 through battery 10 tends to deflect the armature 3 to the left again. hen two polar relays are connected together in this Way, each reversing the other, their armatures vibrate with great rapidity, particularly if the armatures be light and their stops adjusted so as to permit only a small amplitude of movement. Such a vibrator is preferable for use in my system to vibrators consisting of spring-reeds electrically driven, because when either armature is in either of its extreme positions no tendency exists for it to move to the opposite position until the polarity of its magnets has been reversed, and if such reversal of the magnets of one of the relays be prevented at any instant as, for instance, by energizing other coils of the relay, which exert a preponderating influence on the armature-the vibration of the armatures ceases instantly, to be resumed instantly when the circuit exerting such preponderating in- Circuit 5 when complete.

fluence is broken; but I do not limit myself to the use of this type of vibrator.

Transmitters G and D are exactly similar in construction, and the circuits by which they are connected to selector E are similar. Only transmitter U need be described. It consists of polar relays 11 and 12, a handkey 13, and suitable circuits now to be described.

From conductor 4 a branch conductor 14; leads through coils of relays1 and M to a contact-tongue of hand-key 13, forming a part of transmitter C. The coils of relays 1 and M, through which this circuit 14- passes, are so wound that when energized the armature i) of relay 1 is held to the left and the armature 15 of relay M is moved to the left. The coils of relay 1, through which circuit 11 passes, exert a stronger influence upon the armature 2% when energized than do the coils through which circuit 8 passes. This is indicated in the drawings by showing the battery Ii as made up of a greater number of cells than batteries 9 and 10. Key 13 has contact-points similar to the contact-points of an ordinary continuity preserving transmitting relay that is to say, it has a spring contact-tongue 16, mounted upon a movable lever 17, having a contact point or hook adapted to make contact with the tongue, and a stationary con tact-point 18, adapted to make contact with the contact-tongue when the key is depressed and to move the tongue away from the contact-hook. To the lever 17 of key 13 is connected a conductor 19, leading through coils of relay 11 to the left-hand contact-stop of relay 12. Normally conductors 14; and 19 are in communication, their circuit being broken at relay 12, the armature 20 of said relay being in contact with its right-hand contact-point. To the contact-point 18 of key 13 is connected a conductor 21, leading through coils of relay 11, which oppose those coils to which conductor 19 is connected to the right hand contact-point of relay 12. To the contact-stops of the armature 22 of relay 11 are connected batteries or generators 2 and 24;, the poles of which are oppositely placed. both of these batteries being connected to a conductor 25, leading through coils of relay 12 to the armature 22. \Vhen the circuit 25 is complete through battery 24-, it tends to move the armature 20 to the right and hold it in that position, and when complete through battery 23 said circuit tends to move the armature 20 to the left and to hold it in that position. Relay 12 is very quick-acting, having a very light armature, while relay 11 is slower acting, its armature having upon it a weight 26, by moving which along the armature the speed of the relay may be adjusted.

\Vhen key 13 is depressed, its contacts 16 and 18 make contact, and if the armature i be then in contact with its left-hand contact-stop circuit 14. is completed through conduct-or 21,

thereafter, since it is in rapid vibration.

armature 20, and a return-conductor 27, connected to the return-conductor 6,- which leads 'to the negative pole of battery K. If armature 3 be not in contact with its left-hand contact-stop at the very instant when contact is made between contacts 16 and 18 of key 13, it will be in contact therewith an instaAnt s soon as the circuit 14 is complete armatures 3 and 7 stop vibrating and the armature-15 of relay M moves to' the left, as does the armature 22 of relay 11. As soon as armature 22 reaches its lefthand contact-stop it completes circuit'25 through battery 23, thus reversing relay 12 and breaking circuit 14. Armatures 3 and 7 of relays 1 and 2 then commence vibrating again. When the key 13 is released, contact-tongue 16 and contact-hook 17 make contact, completing circuit 14- through c'onductor 19, armature 20, and return- conductors 27 and 6, if as soon as armature 3 is in contact with its left-hand contact-stop and the armature 22 of relay 11 is deflected to the right, circuit 14 remaining complete, however, until armature 22 has reached its right- 7 hand contact-stop and by completing circuit .25 through battery 24 has reversed relay 12.

depressed and again when key 13 is released,

as shown above,) armature 15 is moved to the left until it makes contact with its left-hand contact-point, to be returned to central position as soon as circuit 14 is broken. To the left-hand contact-stop of armature 15 is connected the positive pole ofline-battery H, and to the armature itself is connected the line conductor L. When key 13 is depressed and again when key 13 is released, therefore, battery H is placed to the line momentarily, so

producing in the line a momentary current pulsation'of positive polarity.

A conductor 29, branching from conductor 5, passes-through magnet-coils of relays. 1 and M, these coils being wound, however,-so as to hold armature 3 and deflect armature 15 to the right when energized, and said conductor isconnected to the contact-tongue of the key 13 of transmitter D. When said key is de pressed and again when itis released, the armature of relay M is moved to the right, and since the right-hand contact-stop of said relay is connected to. the negative pole of linebattery I said battery is placed to, the line momentarily when the key is depressed and again when it IS released, so produclng 1n the l1ne a momentary current pulsation of negative polarity. Both batteries H and I may v ing it to be placed to the line before the other battery isso placed and holding. back the pulse from the second battery until the pulse from the first battery is completed. Which of the two batteries is thus given precedence depends upon whether the armature ,3 of relay 1 of the selector makes contact with its righthand stop or with its left-hand stop the instant after the'keys are depressed. With whichever stop it first makes contact it is held in contact therewith until the pulse from the corresponding battery-Flor I is completed that is to say, until the armature 22 of the relay 11 of the corresponding transmitter has reversed the relay 12 of the transmitter. As soon as one pulse has been completed, so that the armature 3 is released, it moves to the opposite contact-stop, and so permits the pulsations of current from the other battery to pass through the line. I

If one transmitting-keyis depressed after the other transmitting-key has been depressed and after the line-battery controlled thereby has been placed to the line, the placing to the line of that line-battery which corresponds to the transmitting-key last depressed willbe delayed until the battery corresponding to the transmitting-key first depressed has been cut out of the line by the operation of its transmitter. The length of the current pulsations produced by the operation of the transmitters is so brief as compared with the length of a dot of the telegraphic code thatthe slight delay in'the production of a pulsation from one of the batteries due to the selecting action of the selector E, above described, does not produce any appreciableor detrimental delay in the operation of the corresponding receiving'instrument at the distant end of the line nor does it appreciably orv detrimentally shorten the signal whether it be a dot or a dash.

The function of relays 11 and 12 of the transmitters is simply to so operate the circuits connected to the corresponding transmittingkey 13 that a pulsation of the current of the proper polarity will be produced in the line at the instant when the key is depressed and again at the instant when the key is released; but I do not limit myself to the use of any particular devices for producing double pulses each timea key is depressed and then released,

nor do I limit myself to the particular selecting devices'employed for giving precedence to oneor the other of the pulses when two keys are depressed simultaneously, although I believe the transmitting instruments and the selector to be particularlysuitable for use in this system. The relays 11 may be termed primary relays of the transmitters and the relays 12 ,secondary relays. Thecircuits The receiving-relays F and G at the receiv ing-station B may be termed single-direction double-current relays, since each responds to current impulses of but one direction, but is changed from and restored to normal condition by alternate current impulses of that direction. Each of the relays consists, essentially, of a polar relay provided with means for reversing the polarity of its armature when the position of said armature is reversed, so that a current impulse of the same direction as the impulse which first defleeted the armature from its normal position will send it back to normal position; but in order to obtain great delicacy of operation and also steadiness I prefer to employ in the relay the principles employed in the polar relay covered by my Patent No. 560,313, dated March 19, 1896that is to say, to employ a secondary circuit which tends to hold the armature stationary, but is broken when the armature moves and is reversed when the position of the armature is reversed, and a tertiary circuit which normally opposes the secondary circuit, but is weaker than the secondary circuit, and is reversed by a reversingrelay controlled by said secondary circuit when the position of the main armature is reversed.

Each receiving-relay consists of three subrelays-viz., a main relay 30, through which the line-circuit passes, a secondary relay 31, and a reversing-relay 32. The armatures of relays 30 and 31 are mechanically connected, so as to move together, and may be connected in the manner shown diagrammatically, one having a rounded end fitting within a forked end of the other, though I do not limit myself to their connection in this manner. Relay 32 is an ordinary polar relay, having, however, a weighted armature, the weight being adjustable, as is the case with the relays 11 of the transmitters. Each receiving-relay has two local batteries 33 and 34, the poles of which are oppositely placed. The positive pole of battery 33 is connected to the left-hand contact-stop of the connected armatures of relays 30 and 31 and is also connected to the left-hand contact-st0p of relay 32. The negative pole of battery 34 is similarly connected to the right-hand contact-stop of relay 32 and to the right-hand contact-stop of relays 30 and 31 through a sounder or other receiving instrument, which is lettered O, for receiving relay F and P for receiving relay Preferably a shuntresistance-coil is connected across the terminals of each sounder, as shown in the drawings. One of the two connected armatures of relays 30 and 31 is con nected to a conductor 35,leading through coils of relay 32 to a return-conductor 36, connected to a conductor 37, which connects the negative pole of battery 33 and the positive pole of battery 34. W hen battery energizes this circuit of conductor 35, the armature of relay 32 is moved or held to the left, and when battery 34 energizes the circuit said armature is moved or held to the right. A branch conductor 38 leads from conductor 35 through coils of relay 31 to return-conductor 36, and these coils of relay 31 when energized by battery 33 tend to hold the two connected armatures to the left, while when the coils are energized by battery 34 they tend to hold the connected armatures to the right.

Relays 31 and 32 have their armatures magnetized by permanent magnets, or if their armatures be magnetized by elcctromagnets the polarity of such magnets is never changed with respect to that of the main or lield magnets. The armature of relay 30, however, is magnetized by an clectroniagnet 39, the polarity of which is reversed by the relay 32 when it operates, owing to the fact that relay 39 is energized by current from whichever of thebatteries 33 or 34 is in comniunication with the armature of relay 32 and passing from said armature through conductor 40, which is also connected to the coils of magnet 39 and through the return-00nductor 36. A branch conductor 41 leads from conductor 40 through coils of relay 31, which opposes those to which conductor 38 is connected, and through an adjusting-rhcostat 42 to the return-conductor 36. The resistance of the rheostat 42 is so adjusted that the cfl'ect upon the connected armatures of the coils to which conductor 36 is connected when said coils are \energized is almost neutralized by the ell'ect on said armatures of the coils to which conductor 41 is connected, suiiicient of the magnetizing force of the coils connected to the conductor 38 being left unneutralizcd, however, to hold the armatures stationary against the effects of leakage or induction-currents in theline. Theline conductorL 'iasscs through the coils of the main magnet of subrclay 30 of relay F and through the corresponding coils of subrelay 30 of relay G to ground.

Conductors 35 and 38, passing through magnet-coils of subrelays 31 and 32, together with conductors connecting the batteries 33 and 34 to the contact-points oi the connected relays 30 and 31 and the rcturn-comluctors, may be said to constitute a secondary circuit. Conductors 40 and 41, passing through magnet-coils of relay 31 and through the armature-magnet 39 of relay 30, together with the conductors connecting the batteries 33 and 34: to the contact-points of relay 32 and the return-conductors, may be said to constitute a tertiary circuit.

A's willbe shown, each of the relays F and G responds only to the currents of one .po-

larity, being extremely sensitive, however,

larly. The magnet 39 of relay F is so wound.

' or so connected in its circuit that said relay circuit is broken, and the effect of the tertiary circuit on the'armatures being then unopposed the current in said tertiary circuit will carry the armatures over, eventhough the current pulsation in the line which primarily caused the armatures to move should cease before they have reached the right-hand contact-stop. As soon as the armatures reach such stop the secondary circuit is completed from battery 34 through sounder 0, thus operating the sounder, holding the connected armatures against their right-hand contactstop and reversing the armature of relay 32, so reversing the tertiary circuit, which when reversed again opposes the secondary circuit in relay 31. The reversal of the armature of relay 32 reverses the polarity of magnet 39, so that when a second positive pulse comes over the line the connected armatures of relays 30 and 31 will be moved to the left and relay 32 again reversed, thus cutting out the sounder O andvrestoring the parts to their.

and when said armatures are against their right-hand stop, the polarity of magnet 39 having been reversed negative pulses in the line conductor simply tend tohold the armatures in that position.

Tothe contact-stop of contact-lever 28.. of

selecting-relay M is connected a conductor 50, leading to ground. When the armature 15 of said relay occupies an intermediate'position, theline conductor L is connected through the armature and lever 28 to conductor 50, and so' to ground. This ground connection facilitates the discharge of the line after each signal.

The operation of the instruments and circuits shown in Fig. 1 is a follows: Normally the armatures of relays 1 and 2 of vibrator N are in rapid vibration. If one of the transmit terkeys-as, for instance, that of transmitter Cbe depressed, a selector-circuit is'completed through conductor 14 in this case and through conductor 21 of the transmitter, thus deflecting the armature of selecting-relay M to the left and placing battery H to the line and arresting the vibration of armatures 3 and 7 of the vibrator. Energizing the magnetcoils of relay 11, through which conductor 21 passes, causes the armature of said relay to move to the left, and when it has reached its left-handcontact-point it completes thelocal circuit of conductor 25 through battery 23, thus reversing the relay 12, breaking the selector-circuit of conductor 1 1, and ending the current impulse from battery H, the vibrator beginning to operate again immediately.

When the transmitter-key is released, selectorcircuit 1 1 is again completed, this time through conductor 19, the battery H is again placed to the line by relay M, and the relay 11 is again reversed, thus reversing relay 12 and breaking the selector-circuit again, thus ending the current impulse from battery H. 'In this way a brief current impulse is produced in the line at the beginning and again at the end of each signal of transmitter O, the length of the impulse being determined by the adjustment of the weight on thearmature of relay 11 and the distance between the stops of said armatures. If transmitter D be operated, an impulse of current from batteryI passes through the line at the beginning and again at the end of each signal of the transmitter. Both selector-circuits'viz. the circuits of conductors 14 and 29cannot be complete at the same instant, forsaid circuits pass through opposing contacts of relay 1. Hence if the transmitter-keys of the two transmitters be operated simultaneously that selector-circuit will be completed first with the contact-point of which the armature 3 first makes contact, and as each impulse in each selector-circuit checks the vibration of the armature 3 the impluse in the other selector-circuit will be delayed until the impulse in the selector-circuit first completed is finished. In this way conflict between the two transmitters is avoided. The impulses are of such short duration, however, that the slight delay in the sending of an impulse by one transmitter under such circumstances is imperceptible, and the delay is never sufficient to convert a dot into a dash. When an impulse Ice 4 of positive current passes through the line at the beginning of a signal of transmitter C, it deflects the connected armatures of relays 30 and 31 of receiving instrument F to the right. The secondary circuit through conductor 31 is broken the instant said armatures begin to move, so that the tertiary circuit will carry the armatures ever even should the impulse cease before the armatures have reached their right-h and con tact-point. When they do reach said right-hand contact-point, the secondary circuit is again completed, but with the current reversed, and the reversingrelay 32 is reversed, thus reversing the direction of current in the tertiary circuit and reversing the magnet 39, by which the armature of relay 30 is magnetized. Negative impulses in the line can have no influence on relay F When the parts are in this position therefore; but when a succeeding positive pulse passes through the line the armatures are deflected back to their first positions by a similar action of the circuits, magnet 39 recovering its former polarity. The completion of the secondary circuit through the right-hand contact-point of relays 30 and 31 operates the sounder O. Receiving-relay G is operated in a similar manner by negative current impulses, but does not respond to positive current impulses.

The receivingrelays are not aifected by leakage and induction-currents in the line, since a line-current in order to operate either relay must overcome, though but for an instant, that portion of the influence of the secondary circuit on the armatures of relays 30 and 31 which is not balanced by the tertiary circuit.

In Fig. 2 the transmitting and receiving instruments at one end of a quadruplex line are shown. The transmitting instruments and circuits are the same as those shown in Fig. 1. Since the receiving-station corresponds to a transmitting-station at the distant end of the line, it is lettered B. The receiving instruments are the same as those shown in Fig. 1, except that each main relay is provided with two separate sets of coils, one connected to the line conductor L and the other to an artificial line conductor L. The effect of the artificial line is to balance the influence of outgoing messages in the line upon the home receiving instruments.

A great advantage of the system of duplex and quadruplex telegraphy herein described is that it employs nothing but pulsatory currents. I have found that much better results may be obtained by the use of such currents than by the use of currents of longer duration. Arcing at the contact-points is avoided, and it is possible to use a higher line potential without excessive leakage than would be possible otherwise, thus insuring clearer signals. Another great advantage of this system is that it employs nothing but polar instruments, which are far more seiisitive. quick-acting, and reliable than instruments of the neutral type.

For convenience in following the action of opposing magnet-coils of certain of the instruments herein illustrated 1 have sought in certain instances as, for example, in the illustration of relay l to indicate the opposing action of the several coils in each magnet-spool of the relay by showing the same wound in opposite directions about the core. It will be understood that such illustration is purely diagrammatic and illustrative and does not indicate any specilicdircction of winding. Furthermore, it has been necessary to avoid confusion of the drawings to show correspending coils on opposite sides of the armatures of the said relays as wound in the same direction. It will be understood that in so doing I illustrate merely therelative winding with respect to each core considered separately of the coils surrounding the same and that the connection of the several corresponding coils to their respective circuits must, nevertheless, be such that corresponding coils on opposite sides of an armature tend in every case to produce opposite magnetic poles, as in any ordinary relay or horseshoe-electromagnet.

In another application for Letters Patent, filed October 11, 1898, Serial No. 693,205, of which this application is a division, I. have illustrated, described, and claimed the apparatus herein illustrated and described and which carries out the method of transmission herein described and claimed.

hat I claim is 1. The herein-described method of trans mitting simultaneous telegraphic messages in the same direction, through a single circuit, which consists in transmitting the signals of each message by current impulses occurring in pairs, one at the beginning and the other at the end of each signal, the signals of one message being transmitted by positive impulses and the signals of the other message by negative impulses.

2. The herein-described method of transmitting simultaneous telegraphic messages in the same direction, through a single circuit, which consists in transmitting the signals of each message by current impulses occurring in pairs, one at the beginning and the other at the end of each signal, the signals of one message being transmitted by positive impulses and the signals of the other message by negative impulses, and in giving precedence to an impulse of one signal over an impulse of another signal, when required.

3. The herein-described method of trans mitting simultaneous telegraphic messages, through a single circuit, which consists in transmitting two messages in each direction by current impulses occurring in pairs, one at the beginning and the other at the end of each signal, the signals of one message being trans- 7 mitted by positive impulses and the signals of the other message by negative impulses, and in counteracting, ateach end of the line, the effect of the outgoing messages upon the receiving instruments located at that end of the line, by a method of duplex telegraphy, substantially as described.

4:. The herein-described method of transmitting simultaneous telegraphic messages, through a single circuit, which consists in transmitting two messages in each direction by current impulses occurring in pairs, one at the beginning and the other at the end of each signal, the signals of one message being transmitted by positive impulses and the signals of the other message being transmitted by negative impulses, in giving precedence to an impulse of one signal over an impulse of another signal, when required, and in counteracting, at each end of the line, the effect of the outgoing messages upon the receiving instruments located at that end of the line, by a method of duplex telegraphy, substantially as described.

5. The herein-described method of transmitting telegraphic/signals, which consists in transmitting signals by current impulses always of the same polarity, which occur in pairs, one at the beginning and the other at the end of each signal, each signal, dot or dash, as the case may be, comprising two such impulses, the duration of the interval between the impulses of each signal determining whether that signal is a dot or a dash,

In testimony whereof I aflix my signature in the presence of two witnesses.

THOMAS B. DIXON.

Witnesses:

' HARRY M. MARBLE,

A. H. PERLES.

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