US189184A - Improvement in automatic telegraphy - Google Patents

Description

I 3 Sheets-Sheet1. J. W'.'BR.OWN.

. AUTOMATIC TELEGRAPHY. No.189,184. Patnted Apri13,187 7.

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- J. W. BROWN. AUTOMATIC TELEGRAPHY.

Patented April 3, 1877.

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' 3 Sheets-Sheet 3. J'. W. BROWN. AUTOMATIC TELEGRAPHY.

N o.189,184. Patented A riia, 1877.

BA TIT/i Y Zwss: I 2 Y vnrran QFFIGE JAMES WALLACE BROWN, 0F PORT HURON MIOHIGAN IMPROVEMENT. IN .AUTQMATIC TELEG'RAPHY Specification forming part of LettersPatent Nod 89,184, dated April 3, 1877;. application filed May 21,1875

' To all whom it may concern 4 Be it known that I, JAMES'WALLAGE' -BROWN, of Port Huron Michigan, United "States of America,'but atpresen-t ot' :Leadenhall street, in the city-of- London, England,

electrical engincer, have in vented certain Improvements in Apparatusi'for Transmitting Telegraphic Signals, of which the following is a specification:

- This invention relates'to the working of chemically printingand recording telegraphs, I

the object being toincrease the speed of'transmitting to receiving-instruments telegraphic signals through long circuits, EtIld,lI10I6:'S-* pecially, through submarine cables and-under-ground wires. I accomplish thisobject by I a peculiarkind of perforated ribbon orstrip of paper, in combination with three transmitting pens, styles,--*orcontact -=points, i :(or

their equivalents,) set abreast of and insulated the one from the other, as will bepresently explained.

- Before, however, I proceed to describe in detail the nature andoperation of my inven tion, it will be well to :explainthe present state of telegraphy in itsnrelation to chemi cally-recording telegraphs, as the'adaptation of theinvention to existing systems will be thereby the better appreciated.

In working chemical telegraphs great difficulty is experienced in producing legible telegraph-signals through long aerial circuits, cables, andunder-ground wires, for the reason that as the telegraph -code is composed of dots and dashes, thewire is charged to a much higher potential when making dashes than I when making dots. 1 This unequal charging of the wire has the effect-0trunning the-(lasli into the dot that immediately follows it, and

wh n the cableor wire is very long-thisdash is unduly prolonged so much so that the whole letter, which should 1 be composed of dots and dashes, is littlebetter than onelong dash.

. If the cable or wire wereofshort-length, comparatively speaking, this would-not take place to any great extent, because the wire would discharge itself in so: short a 1 time that there would be no .appreciabledrag V upon'the signals. In longcircuits however,

.being the sameunintelligible signals. -when this condition is reached, there is apthe wire will not discharge quickly enough, and hence the dragging out of the signals. Thus, as the length of the circuit increases, so is .the difficulty of obtaining intelligible signals increased. By artificial means, however, this dificulty is remedied to a great extent.

- The mostcommon way of obtaining this re- 1 sult,-when;using single currents, is to put a leak inline beyond the transmitting-instrument-th at is, to connect the line-wire to earth through a suitable resistance beyond thetransmitting-instrument, so. as to allow the dine-wire, when battery-contact is broken, to discharge to earth through i this resistance; but this plan has the disadvantage-that the :battery, when sending theprinting-current to line,=has to supplythisleak or circuit between line and earth also; but as thevresistance between the line and'earth is reduced, so is the strength ofcurrent in the. line-wirere- :duced.

Now, if theline-wireis of considerable len th, it will take .so .long to discharge that it becomes necessaryto make this leak between line and earth .of very low-resistance, intord er to make the conditions of line right toiusure .good signals at the distant end. It a very powerfulbattcry-ofl0wJinternaLresistance, be used,. the= resistance between line and earth may be :reduced in proportion; but this is \limited, because beyond aeertain limit it "would be impossible to reduce this resistance between line and earth, for the reason that plied atthe receiving-instrument a-contrivancestyled a magnetic shunt, whichcon- :sists of a series ot electro-magnets, so ar- =ranged.-t hat itis possible to put in one or .more electro-rnagnets in the shunt-circuit, the

terminals ot'saidshunt-circuit being connectmade the signal.

ed to line-wire and earth, so when the printing-current acts upon or through the receiving chemical paper commencing to record the signal, it also acts through the magnetic shunt charging the electro-magnets, and in doing this part of the current is diverted from going through the receiving chemical paper;

or, in other words, the total current that arrives at the receiving-instrument is split, and and in proportion to the resistance of the magnetic shunt, so it is understood that the amount of current going throughthe receiving chemical paper can be regulated, thereby using butjust enough current to produce the signal at a given rate; but the great advantage of the magnetic shunt is (as is well understood) that when battery-contact is broken at the transmitting end it allows the electromagnets of this magnetic shunt to discharge, and this discharge of the magnetstakes place inthe opposite direction through the receiving chemical paper to that current which This being the case, it follows that this discharge of magnets cuts oft this drag or prolongation of signals, producing legible signals; but it only does this where the fall-of potential is in the same ratio as that of the line; but as it isalmost, if not quite, impossible to secure this condition with the magnetic shunt in working long circuits,

and more especially long submarine cables, the signals or dots and dashes are liable to run together, thus rendering them entirely unintelligible.

1f the leak or resistance before mentioned between wire and earth at the transmitting instrument be used in connectionwiththe magnetic shunt at the receiving end over a given circuit the signals will be better than if oneor the other is used alone; but the limit .is soon reached, when the signals become imperfect and unintelligible.

In. double current systems, as ordinarily used, the results are less satisfactory than that of single currents with the aid of the magnetic shunt and. leak at the transmitting end. In working double currents the same difficulty is experienced in making dots and dashes as in 'single currents. The wire is charged unequally, and the effect is, as before, dots and dashes run together; but better results are got by sending-a strong initial current to line, followed by insulation in case of making a dash, and then a reverse current, to cut'the dash, as it were, the right length,-

or, in other words, cut off the drag. This is technically termed intermittent currents,

the object of it being to have'the currents for making the dot and the dash of the same strength and duration 5 but in short circuits, to accomplish this object theysignals have to 'be transmitted so slowly that there is no advantage-gained. In longer circuits, or where the static capacity of line is great, and this system is used, it is found that the printing-current will be in excess; for instance, in transmitting R, (dot, dash, dot,), no current having been sent during the latter part of the preceding space, the line-wire is clear, and receives afull charge from the marking-current for the dot, the following reverse currentis immediately succeeded by a marking-current for thedash, and during the remainder of the dash no current is sent to line. Two marking-currents are thus sent to one reversal, and the tendency is for the dot and dash to run together, because the marking current, to

commence the dash, being followed by insulation, charges the wire to such an extent that it cuts the reversal or neutralizes it'so quickly that it has not time, or is not of suflicient strength, to cut oft the drag of the dot. In the case ofthedot following the dash, the reverse occurs. Owing to the longinterval since the markingcurrent was sent, the line has become nearly. m'l, so when the reversal is sent 'to cut the fdrag, it charges the wire so highly that the marking-current to make the dot is shortened, and a reversal being sent immediately after cuts the dot so quickly that it will be out of proportion withthe other signalsin fact, two reversals being sent to onemarking-current. v

Thereisanot'her appliance used at the transmitting-instrument. It is a large resistance placed between battery and line, said resistance being adjusted to conditions of line, and so manipulated that when a current is sent to line of one name, by means of transmittingpermanent currents or double currents, as it is called, with the exception that two-thirds of the current is weakened in comparison to the first third, for duringtwo-thirds of the time employed to make the dash the current has to act through a larger resistance, in addition to that of the 'line. This is styled sending compensating-currents.

Now, the difficulties in the abovementioned plans of transmitting telegraphic signals are capable of removal, to a great extent, by

adapting my invention thereto, it'being thereby possible to work over long circuits, submarine cables, and under-ground wires at a much greater speed than is accomplished by the existing systems. r

I will now first describet-he application of my invention to the system of workingchemically-recording telegraphs.

Figure 1 shows a transmitting and receiving instrument connected to opposite'ends ot' a ing-currents.

line-wire or cable. In their general construction they are similar to thosein common use for transmitting and receiving messages antomatically; but in this case there is applied to the transmitting-instrument three insulated transmitting-pens or styles,set abreast of each other, and in connection therewith I use a strip of perforated paper similarto that shown at Fig. l.

- A is the transmitting-drum, formed of metal, and rotated by clock-work or equivalent motive power. Bearing upon this drum are the three contact points, pens, or stylcsa be, connected, respectively, with wires leading to the battery and to earth.; B is the receivingdrum, which is similar to the transmittingdrum, but is fitted with butone pen or style,

d- The office of .this pen is to record signals upon chemical paper in the usual manner. The transmitting pens or styles are manipulated by the strip of perforated paper, Fig. 1*, the perforations being peculiar in their arrangement. The three pens are insulated one from the other, each pen performing its work independently of the others.

In this case the reversing-pen b is connected to the reverse pole of the battery, and thus, when it drops into a perforation, a reverse current is sent to line. To accomplish this I prefer to arrange my battery as shown, hav-.

ing the center of battery put to earth, using the extreme zinc pole to print, and the extreme copper for the reversal. A resistancecoil may be placed between the printing and compensating pen, as shown by dots atDin the figure, for the purpose of sending compensat- It will be seen that when'the compensating-pen drops into a perforation, (which only occurs when making a dash,) it will send a much weaker current than that sent by the printing-pen; or, in other words,the printing-pen sends a strong initial current to line, followed by a weak current (which can be regulated by the amount of resistance introduced between the two pens) of same denomination. This prolongs the signal upto the limit when the printing-pen again enters a perforation. This will have the effect of governing the wire, as it were, and only allowing the potential to fall to a certain extent.

cessity of having the full'strength of current to line in making a dash, and thereby charging the wire to a greater degree than is required for making a dot. When the printing- The 1 pen drops into the last perforation of the dash it sends the current of full strength, so as to makethe dash of sufficient length but in doing this the wire does not become so highly charged as it would have vbeen if the full strength of current had been sent throughout the-signal, as in the previous case, where no resistance was interposed between the printing-pen and compensation-pen, the current which makes the dash charging the wire little, if at all, more than thatwhich makes the dot, and the reversal being sent immediately to charge the wire in proportion, the peculiarity of my plan being that I send a strong initial current followed by a weaker one, termed compensation, in the same direction, and then for the last third of the dash I send another current in the same direction as the initial current, followed by a reversal, the compensation making only the center of the dash. Of course, it is understood that I only have reference to those circuits where this peculiar form of compensation can be employed with profit either on other systems or my own, the arrangement of battery being the same as before. i

I will now describe an arrangement by which I gain the advantage, in chemical telegraphy, of having the currents that make the dash of the same duration as that which makes the dot, the static electricity of the line-wire being utilized to make the center of the dash by filling up the interval which occurs between the two currents, in the same direction, which are sent to make the dash. In this case, as before, it will be seen that, by depending upon the static electricity to make only one-third of the dash, I can transmit telegraph-signals much more rapidly than where the staticelectricity is depended upon to make two-thirds of the dash, asI do not have to charge the wire so high with my first initial current.

- I also derive another advantage by having the resistance between the compensating-pen and earth adjustable, as I obtain a larger margin to work uponfor instance, if the resistance'is too small, and discharges the wire so quickly, at a given speed of working, that the dash is weak or split in thecenter,'l can-add more resistance until the dash is made perfect in the center at the same rate of speedas before, and, vice versa, the commencement and end of dash always being full.

4 lemu- In thelarrangement shown at Fig. 2, the pens or styles or and b I connect with opposite poles of. the battery, and the compensa tion pen or style a I connect with the earth, interposing a resistancecoil, D. The perforations in the ribbon (see Fig.1)are so arranged that one-only of the pens shall be in contact at a time with the metal 'drum of the transmitting instrument. When making a dash, I send first a strong initialcurrent to line throughthe pen a, and thereby charge the line-wire toja high potential. When the.

penor breaks contact with the drum A, by reason of a solid portion of the ribbon coming under the pen, the compensation-pen 0 drops into contact with the drum, a perforation of the traveling ribbon being brought under it. This has the efi'ect of clearing the wire of static electricity, (the said penbeingconnected to earth.) If, however, no appreciable resistance were interposed between this pen and earth, the wire would discharge in so short a time that there would be only adot produced at the receiving end; but by introducing a given resistance. as at D, between the pen and earth, the discharge'of the wire will be retarded sufficientlyto insure the pro1onga tion of the signal at the receiving end up to a certain limit. To finish the signal or dash, a second strong current, is now sent 'to line through the marking-pen. a, and this is in stantly followed by acurrent to line in the opposite direction, caused "by theyreversingpen bdroppiug intoa perforationin theribbon.

In circuits that have great static capacity,

and that will discharge through the compensation-pen and wire to earth during the inter-t v-al between the twoinitial currents that make the dash,this arrangement may be used with out the resistance-coils between compensating-pen and earth, it being supposedthat the wire connecting compensating-pen. to earth, has no' appreciable resistance, a reversal being sent immediately after the last. initial cur-1 l y,

I In Fig.1, which has been referred to rent. 1

Fig. 3 shows an arrangement for sending reversals of varying strength, as may be required in center of'dash, the printing. and reversal pens being arranged as in Fig. 2,; The object of this-arrangement is to enable me to work over circuits where the static capacity is so "great that themeans just described will 1 not discharge the wire during the, interval that occurs between the two currents in the same direction which are used .in making the dash'.- a I The compensating-pen in this case is-connected, through the adjustable resistance diately upon the printing-pen rising out of the perforation, the compensating-pen drops into a perforation, sending a reverse current to line. The strength of this reverse current is determined by theamountof resistance in troduced between the batteryand pen, and the amount of resistanceto be introduced is determined by the static capacity of the 1ine,'the object being tohave the resistance such that thewcurrentthrough it to line will discharge the wire'atithe poi'nt where the p inbi g p n gain drops ntoa per at o sending the second current for thedash, in- St nd) fol o by a l re ersal, t sb a ing the wire equally in making dots and dashes, "It will beseen that in all, these the dashis formed by toursuccessive stepsefirst, a strong the battery and a momentary earth=connec tion in the still longer lines, or those ofgreatest staticcapacity, a reverse current, weaker than that used in fourth step. Hence,I speak of these as means of compensation,or compensating connections. y I

It will be obvious to electricians. that all which is accomplished hythe three insulated pens may also 'beefifected by three drums, in= sulated the ionerfrom theother, and correspondingto the three insulated pens before described, in which case the transmittingp n Wmildbe l c n ected t geth r! r ng one which would be connected towthe linewire; but- Iprefer thetliree insulated pens, ,as beingmore simple iuarrangement.

I wouldremark that the manner of piercing the strip or ribhon used c to work thethree pens or styles may be modified tosuitvarying circumstances. it

throughout the foregoingdescription, the rib- .bon is shown as pierced totrausn it, the word printed. When the static ,capacity of the line is greatyand it is desirableto put the line-wire to earthrhet'ween each signal, as well as on the middle of each dash, I use; the strip or ribbon shown ,atFig. .5 This figure shows theiletters who (2 e as perforated; for transmis ion, l y l Having how set forth the nature of; myinvention, and explained the manner of carrying the'same into effect, I wish itte be understood that I claiml ut m ic .te e r rh l th me odn form ng (la e hylfirst, ensm i ine tr initialcurrent; second,coinpeusating by weakllng, cutting 9113.1 1 ere sins .si l r nt, as the, state-p17 line may determine, as ezrf p a ned; t i d y tra m c r nt identical with the initial current; and, finally,

a reverse current, equal in strength to initial lar to initial current; and, lastly, a reversing current, substantially as set forth.

2. Combination of strip, perforated as de scribed, the marking, compensating and reversing pens, thebattery, and resistance, with circuit-connections, as described, whereby a dash is transmitted, by using, first, a strong initial current; second, the compensation therefor, as explained; third, a current simior clearing current. I

London, the 26th day of April, 1875.

' J. W. BROWN. Witnesses:

A. SIMMONS,

17 Leadenhall street. H. K. WHITE, Y 66 Chancery Lane.

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