USRE10034E - Duplex telegraph apparatus - Google Patents

Description

QR 9E 101034 ITB. F

- BEST AVAILABLE COPY J. B. STEARNS,

Assignor to THE WESTERN UNION TELEGRAPH COMPANY.

DUPLEX TELEGRAPH APPARATUS. No: 10,034. Reissued Feb. 7,1882.

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UNTTED STATES PATENT OFFICE,

JOSEPH B. STEARNS, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE \VESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y.

DUPLEX-TELEGRAPH APPARATUS.

SPECIFICATION forming part of Reissued Letters Patent No. 10.034, dated February 7, 1882.

Original No 116.847, dated May H, 1:572; Reissue No. 5,3] I, dntul April I, i873. Application for reissue filed November 23, 1581.

DIvIsIoN B.

To aZZ whom it may concern.-

Be it known that I, JOSEPH B. STEARNS, a citizen of the United States, and a resident of Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements in Duplex Telegraphs, of which the following is'a specification.

My invention relates to an improvement in the apparatus heretofore employed for transw inimise e n iesieeelss meltzs enns y m, ernosifiiennscoicene. endanger-1 lir wire.

The general object of the invention is to prevent false signals, which have heretofore been [5 produced upon the receivi ng-instrument at the transmitting or home station by momentarycu'rrents due to and etfects of static induction upon the main line, commonly called the charge and discharge, though more accnrately designated as the current of static charge and the currentofstatic discharge. The charge or current of static charge accompanies the connection of a battery to line to begin a signal, and while the line is being charged an abnormally strong current is set up through the receiving-instrument at the 7 battery end of the line,whose strength rapidly diminishes until the line is fully charged and a current of normal and permanent strength 0 is established throughout its whole length. The discharge or current of static discharge consists of a quick return-current at the battery end of the line, immediately following the transmission of a signal in a direction op- 5 posite to that of the current of charge, and occurring after the line has been disconnected from said battery and connected with the earth.

The invention comprises the following sub- 0 division: First, at each station in a telegraph system for double transmission a receivinginstrument to receive signals from a distant station, a condenser and a transmitting device so arrange at the effects of staticinduction 5 upon the main line caused by and accompanying the transmission of signals to a distant station shall not produce false signals upon the as sociated receivinginstru ment, thereby leaving said receiving-instrument solely subject to the action of currents effecting the transmission of signals from a distant station; second, at each station in a telegraph system for double transmission a receivinginstrument, a condenser and circuit connect-ions so arranged that the current of static charge due to statically charging the condenser and the current of static discharge from said condenser shall respectively prevent the current of static charge and the currentof static discharge due to mainline induction from producing false signals upon the associated recciving-instru- -ment; third, at each station a receiving-instruincnt and a branch conductor electrically connected with the main line, having an artificial clectro static capacity whereby the 6 charge and discharge due to static induction upon said branch shall prevent the-charge and discharge of the main line due to staticinduction from producing false signals upon said associated receiving-i nstrument; fourth,a receiving-instrument at each station responding to signals sent from a distant station, but insensible to signals from its associate transmit-- ter at the same station, in combination with a branch having an artificial electrostatic capacity due to an increased conducting-surface of such branch, which is obtained by electrically connecting metallic plates immediately to said branch; fifth, a receiving-instrument at each station, in combination with a branch having an artificial electrostatic capacity, means for efl'ecting which consists of a metallie conducting-surface in electrical connection therewith, and an additional conducttug-surface in close proximity to the first one, but insulated therefrom and electrically connected with the earth, whereby the inductive reaction between the metallic plates of the branch and the earth may be made to correspond to that between the main line and the earth.

For the purpose of more clearly explaining my invention, I will first describe the construction and mode of operation of one form of telegraphic apparatus for the simultaneous transmission of signals in opposite directions over the same line, commonly known as a duplex telegraph, selecting for that purpose the apparatns described in my former patent of June 2, 1868, numbered 78,548. This apparatus is represented, in connect-ion with my present improvements, in Figure 2 of the accompanying drawings.

The conditions requisite for thed uplextransmission of signals in opposite directions are, first, the receiring-instrument at each station must remain at all times in connection with the line; second, the signals transmitted by the key at either end of the line must produce no effect upon its associate receiving-instru ment, technically termed the home instrument, at the same station; and, third, theresistance of the line must remain practically constant, irrespective of the position of the transmitting-keys. These several conditions are fulfilled in the apparatus iepresented in the accompanying drawings, and hereinbefore referred to, as will appear from the following description.

Fig. 2 represents the apparatus at one terminal station of the line, that at the other station being similar thereto in construction and operation.

The receiving-instrument M (here shown as a Morse relay) is constructed in the ordinary manner, and consists of an electro-magnet, m, an armature, a, and a retracting-spring, s, to which is added, for duplex working, an equating clectro-magnet, m, so placed as to he capable of exerting an attraction equal to that of the electroanagnct m upon the same armature a, but in a contrary direction. Such an arrangement is technically termed a differential electro magnet. One terminal of the main battery M B is connected with the earth and the other to the lever d of the transmitter T, which acts as a key to transmit signals over the main line,as hereinafter explained. WVhen the transmitter is closed the lever d is brought against the stopp, making contact with it and lifting it from the stop 1', whereupon the current from the battery M B passes by the wire 2 through the contact-1ever q to the point 0, where it divides, one portion passi'ng through the electro-magnet m of the receiving-instrument to the main line, while the other portion passes through the elcctro-magnetm ot'the receiving instrument and returns directly to the earth, or, what amounts to the same thing, to the other pole, c, of the main battery. This latter branch of the circuit, from the point 0 to the point a, is technically termed the artificialline, in order to distingnishit from the main line, whichextends from the point 0 to the distant station. Byinserting a rh'eostat, It, which has approximately the same resistance as the main line, into the artificial line, as shown in the drawings, the electric current going out from the transmitter will divide at 0 into two equal portions; and as these produce an equal development of magnetism in the two electro-magnets m and m, the latter will counteract each other in their effect upon the armature a, which will therefore remain at over the line to the distant station. If, how ever, the distant station transmits a current at the same time, the strength of current in the main line is doubled by the combined action of bot-h terminal batteries, and the electro-magnet m overpowers the eqnatingmagnet m, draws the armature (it away from it, and produces a signal at the home station. Thus it will be understood that the receiving-instrument at the home station responds only when currents or signals are transmitted from the distant station, and not to those proceeding from its associate key at the home station, and consequently the two stations can transmit signals simultaneously, the instrument at each station, though always traversed by the current of the main line, responding only to the signals which are transmitted from the other station.

In operating this apparatus it is preferable to make use of a transmitter actuated by an electromagnet, which is in turn excited by a current from a local battery controlled by an ordinary Morse finger-key, as shown in the drawings, where K is the key; L B, the local battery; E, the electro-magnet which actuates the transmitter-lever d,and r is a contact-stop connected to the earth by a wire, in \Vhen the key and the transmitter are open the line is connected directly to the earth through the wire a.

In Figure 1 of the drawings, I have represented another form of double transmitting apparatus, also patented by me J nne 2, 1868, and numbered 78,547; in which the neutralization of the efiectof the divided currents is accomplished by providing the relay with two coils wound in opposite directions on the same magnet, as described-in the aforesaid patent.

v In this form of apparatus, also, a rheostat or resistance is used having the same, or nearly 4 he same, resistance as the line.

Having thus described two forms of appatus to which it may be applied, I will now describe the nature of my improvement and the mode of its application.

It is well k nown that an insulated telegraphic line-wire of considerable length, whether sus pended above the earth or submerged in water, is capable of accumulating or storing up a quantity of electricity while connected with a battery. This property of an insulated condnctor is termed its inductive or electrostatic capacity, and the electricity so retained is called the "static charge of the conductor. While the line is being charged an abnormally strong current of momentary duration is set up through the receiving-instrument at the battery end of the line. The strength of this current is at its greatest when the battery is first connected to line, but rapidly diminishes untilthe line is fully charged and a current of normal strength is established from the battery throughout its wholelength. This abnormally strong current momentarily set up through the receiving-instrument Iterm the current of rest, notwithstanding that a current is passing static charge. It, therefore, alongline of telegraph, arranged in the manner hereinbefore described, be connected with the battery, by depressing the key at the sending-station, as for the purpose of transmitting a signal, the line will acquire a considerable static charge. At the termination of the signal, when the key is raised, the line is disconnected from the bat tery and connected to the earth at the home station, whereupon the accumulated electricity stored up in the line will suddenly escape to the earth, traversing the electro-rnagnet m of the receiving-instrument. Such momentary current I term the current of static discharge. As the rheostat R and the short line inwhich it is placed have no perceptibleelectro-static capacity, there will be no current of static charge nor current of static discharge through the equating-magnet m, and consequently false signals of momentary duration will be produced by the uncompensated action of the main-line currents of static charge and static discharge in the electro-magnet m.

I have discovered that by producing artificial currents of static charge and of static discharge of electricity at the home station. which I also term effects of staticinduction, and causing the same to occur simultaneously with the currents of static charge and of static discharge on the line, the effect of the latter upon the homeinstrumentcan bepracticallyeliminated, provided proper precaution is taken that the artificial currents of static charge and of static discharge shall occur at the same instant of time, but shall be contrary in their effect to those respectively of the main line. This result is effected by making use of a device for accumulating or storing up electricity, which is termed a condenser. [have shown such a condenser in the drawings at C. It consists of two sets of thin metallic plates of considerable surface separated by insulatingspaces. One set of said condenser-plates is electricallyconnccted to the artificialline circuit by wire w at a point between the electromagnct m and the rheostat It, while the second set is connected to earth.

It is to be observed that the first set of condenser-plates constitutes an insulated terminal, having a large metallic surface, of a branch wire connected to the artificial line. The amount of inductive charge which said plates will receive will of course depend upon the aggregate area of the sheets, the strength of current passing 'over the artificial line, the resistance of the artificial line between its junction with wire to and the earth, and the inductive reaction between said plates and the second set, which is connected to earth. If such resistance below, very little current will be forced upon the insulated terminal plates, while if high the condenser-plates will receive a charge of high tension. It is therefore apparent that by connecting one set of inductive platesto the artificial 1ine,when in close proximity to a second set connected to earth, such artificial line at such point of connection is virtually given a large artificial inductive capacity. My artificial line and condenser therefore constitute an artificial line having alargely increased metallic surface, and in close proximity thereto. but insulated therefrom, a metallic conducting-surface electrically connected with the earth.

I do not limit myself to the use of a condenser with the particular form of duplex apparatus shown, as the apparatus ltereinbefore described may be employed with equally good results in connection with other forms of apparatus.

\Vhat I claim, and desire to secure by Letters Patent, is-

1. At each station in a telegraph system for double transmission, the combination of the main line, a branch electrically connected with the main line, provided with means for giving said branch an artificial electrostatic capaeity, a receivinginstrument responsive to signals sent from a distant station only, and transmitting apparatus whereby the effects of static induction of the branch shall prevent the effects of static induction of the main line due to the transmission of signals from the home station from producing false signals upon the associated instrument.

2. The combination,inatelegraphicapparatus for double transmission at each station, of a receiving-instrument always in circuit and responsive to signals from a distant station only, a condenser electrically connected therewith, and a transmittingdevice, whereby the effects of static induction caused by and accompanying the transmission of signals toa distant station shall not produce false signals upon the associated reeeiving-instrument.

3. At each station in a telegraph system for double transmission, the combination of a receiving-instru ment constantly in the main line, and responsive to signals from a distant station only, and a cgndenser electrically connected therewith, whose static discharge shall prevent the static discharge from the main line from producing a false signal upon said receiving-instrument at the termination of each signal sent to a distant station.

4. A transmitting device and a receivinginstrument at each station, which is responsive to signals from a distant station only, in combination with a branch conductor, and means forgiving said branch an artificial electro-static capacity, said branch conductor being electrically connected with the associated transmitting and receiving apparatus, whereby the current of static charge and current of static discharge set up in the branch 'accompanying the transmission of a signal to a distant station shall prevent the current of static charge and the current of static discharge of the main line from producing false signals.

5. Areceiving-instrument ateach station,iu

combination with a branch, and means for giving said branch an artificial electrostatic capacity, said means consisting ir a metallic conducting-surface in electrical connection with Signed by me this 4th day of August, A. D.

saidbra'nch,andanadditionalconducting-sur- 1881.

face in close proximity to the first one, but

insulated therefrom, and electrically connected 5 withtheearth,whcrebytheinrluetivereaction between the metallic plates of the branch and \Vitnesses:

the earth may be made to correspond to that CHAS. T. GARRET,

between the main line and the earth. l HENRY BALDWIN, Jr.

J. B. STE ARNS.

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