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INOORPOKATED 1S87. TRANSACTIONS. W. B.— This Society, as a bdly, doca not hoM itself resimnsible for the facts and opiniona stated in any (il its imblicatiuns. TUK SlMPLIFICATIOISr OF THE QFADIUTPLKX, ANU THE IMI'OJJTANCE OF ITS ACHIEVEMENT. Uy D. H. Kkkiby, A.M. Can. Soc C. E. To 1)6 road Friday, lUli November, i892. If lb are u any one thing more than another in the domain of practical telegraj ,y that bangs on the consideiation of fine points, it is the .successful operation of a quadruplex system, and to those who have had opportunity for enquiring into the philos- ophy of the thing, this fact is more than pulont, inasmuch as it is found that a very serious difficulty exists whoro at the outset none whatever is apprehended. As a matter of fact, when the quadruplex was a novoKj- and not yet in extensive use the text books were silent on the one vital but seemingly unimportant point to which the delay in developing the .system was referable, and it was sometime before the really diflScult part of the problem was appreciated and under, stood by any excepting those immediately concerned in its con- ception. However, that time is past, and thostudesit of to-day in consulting his text book will find the whole anatomy of the quadruplex laid bare, and the devices in v jduced to obviate the diflSculty thiit is due to an inherent defect are taken into account as an essential part of the whole. That at any rate is the jjoint of view from which this paper is written; and its object is to show in the fii'st pltue, tluit in the established system of quadru- plex telegraph}' there is tin inherent defect whose obviation has encumbered the fundamental jirinciplo with complex apparatus — therebj', from a theoretical standpoint at least, demonstrating its inadequacy; and, in the second place, to show how by building upon a ditl'erent but equally simple principle, the same practical results can be secured with much less mtichinery. With this end in view, a little consideration can now be given to a comparison of the ditl'erent principles involved, and incident, ally the whereabouts tind character of the inherent defect to which allusion has been made, will be perceived, and the method proposed for its elimination understood. For convenience of elucidation it will be well to start with the conception that a quadruplex is a combination of two duplexes, A duplex is a system in which the recorder at each end of the line is so arranged as to be unaffected by currents outgoing, while free to re.spond to currents incoming. In tho quadruplex, there- fore, the distiint recorders respond to the home ke3's or trans- mitters, and the home recorders roupond to the manipulation of the distant transmitters; the result of which is that a single con- ductor is made to afford four distinctive circuits. These circuits, however, are not precisely similar, because the constitution of a quadruplex is such that the duplex element caimot be lost sight of, and a system of this kind is therefore necessarily always re- garded as having two siden. The apparatus on one side (one of the two duplexes) being o])erated by currents differing in polarity or in degree from those operating on the other side. The trouble has been to obviate not only the liability but the possihility of nn interference of one side with the other. The severid methods of quadruplex telograi)hy that have been invented are comprised in two general classes. (1.) Tho Polar systewti, or those in which the receivers on the one side tiro actuated by increase and decrease of a normal current, and on the other side by reversals of that eurrent, and (2.) the straight current systems, or those in which the receivers are actuated by three different strengths of current of a given and unchanging polarity. We can best con^. lor them separately under distinctive head- ings, and assume a practicable type as embracing the whole in each instance. THE POIiAE QUAnRUPLEX. It is the polar qnadruplex that has found favor in practice, but it presents several undesirable features, and, excepting where dynamic currents are available, is expensive to maintain in con- sequence of largo batteries being required for its exclusive use. According to this method, the signalling battery is arranged in two sections. One of the transmitters operates to put one or both of the sections to line; and the other transmitter operates to reverse the direction of the current. The receiving appaiatus corsists of polarized and neutral electro magnets. The arma- ture lever of the polarized instrument is normally held against its limiting stop by the — currunt of the smaller section of the bat- tery, that traverses the line when both of the transmitting keys are at rest (upraised), and it remains in the same position when ihe key that puts the second section of the battery in circuit, is depressed ; but it passes freely over to its front stop or signalling contact when the + current, from one or both sections of the battery, traverse the ciicuit, hence the polarized instrument re- sponds to the manipulation of the reversing key. The armature of the neutral instrument is responsive to both — and + currents, but it is held back by a retractile spring exerting a greater force than the magnetic attraction due to the current from the smaller section of the battery. This latter can therefore be reversed re- peatedly and continuously, thereby producing signals on the polarized receiver, v ithout in any way affecting the neutral in strument. Whenever the increment key is depressed, however, the current iVom both sections of the battery traverses the cir- cuit, the rctnictilc force is insufficiunt to withstand the magnetic attraction imparted to the neutral receiver, and its armature passes over to its front stop or signalling contact; the neutral relay is thus responsive to the manipulation of the incre- ment key. So far the action appears to be smooth and satisfactory, and one might think he could go to work and set up his quadruplex ; but he will discover, as did many an early investigator, that his knowledge is as yet incomplete. It will be found that while no effect is prodrced on the neutral relay by the changes of polarity of the jmal section of the battery, thei'o is a marked inter- ference vfh'u. 'he current of both sections together is traversing the circuit. When the increment key is depressed the neutral receiver responds ; if now the reversing key is depressed, a short false signal will be produced on the neutral receiver. The re- versal of the battery by the reversing key momentarily with- draws the current from the circuit, and in that brief interval the magnetic attraction of the neutral receiver drops sufficiently to allow its armature to fall back from its signalling contact. Here, then, we have the inherent defect of the system clearly defined. It resides in this lack of continuity of current. Divers devices — perhaps multitudinous is a better word to de- scribe their number— have been worked out with a view to obviating this ill effect of the current reversals. Out of them all, the clever arrangements due tf) the ingenuity of Messrs. (ierritt Smith and F. L. Jones have been sifted and adopted in the standard quadruplex of the telegraph companies. There is not much to choose between these two devices; they are distinct- ive types, and have gone a long way to make the quadruplex what it is. Smith puts an extra coil on the neutral receiver coio and connects it in circuit with a condenser shunting a consider- able resistance. The current from both sections' of the signalling battery charges the condenser, and the instant the current ia witliiirawn the condener discharges throujjh the shunted rcsist- anic ami the extra c il on ilio neutial idciver, the magnetic attraction of which latter is thereby maintained. Jones substi- tutes an induction coil for the condenser; the secondary wire is in circuit with the extra coil on the receiver, and the primary i« ti'aversed by the current from hotli sections of the sigiwilling battery; the instant the current is interrupted an induced cur- runt travorees the extra coil, and, as in the other case, retains the armature attracted. Either of these devices necessitates the use of heavier currents than would be required for the mere production of signals on the receivers, because the condenser discharge and the induced wave have to impart nearly the same degiee of magnetism as the transmitted current, so it is found that tiie coils traversed by the transmitted current in the staii> aid quadruplex of to-day are not designed to i)roduce a maximum magnetic effect, whereas the coils traversed by the secondary currents are designed to that end and wound to suit the high potential of the condenser and induction coil discharges. It is seen now that the feature of heavy currents has been dragged into and made a necessary part of the standard quadiu- plex, in eonseiiuenee of a defect that seemingly could not in any other waj' be surmounted. Let us see whether this feature of lieavy currents is attended with any considerable drawback. In consequence of eleetricit}' being as a general thing now so ))lenliful and cheap, it might at first sight be considered im- material, from an economical standpoint, whether heavy or light currents were used in the operation of the quadruplex ; but we have to boar in mind that only a small percentage of the tele, graph wires of this continent are supplied by dynamos, and that, as regards the vast majority of cases, the customary gal- vaiuc battery is in use the world over, and its cost is just as great now as it was 15 or 20 j-eais ago. This fact, dealing with the quadruplex alone, is in itself worth looking at; but when we go further and consider the circumstance that in the course of oper- ation of a polar quadruplex, the positions of the transmitting keys are at times mch as to throw the entire current + from one end and — from the other into the line, whence it follows that the line becomes inordinately charged and by induction would interfere with every other circuit running parallel with it were they not also supplied with otherwise unnecessarily large currents in order to obviate the ill effects occasioned in them : we can appreciate the very great importance of this question. A few years ago, before the days of the quadruplex, our tele- graph circuits were equipped with receivers designed to afford a maximum of magnetic attraction, and the necessity for anything like large currents did not exist. The ordinary run of the old relays measured in the neighborhood of 300 ohms, and we could get good work out of them over long distances. To-day the ordinary run measures 150 ohms; and without going into calcula- tions wo can see that on a given line the latter instrument will be loss efficient than the former, and to make it answer our pur- pose an increased current must be supplied. So we have per- force reduced the sensitiveness of our apparatus and increased our currents; and this it appears is the only way we could keep pace with the quadruplex, for had the more sensitive instruments with comparatively weak currents been retained, the induction from the quadruplex circuits would have rendered the ordinary single circuits well nigh inoperative. ■\Vo see in all this then that the advances made in telegraphy while admittedly very groat from a piactical standpoint, have been at the sacrifice of an economic and a scientific principle. Is it now too late to rectify this error and to return to the old and economical practice that was departed from ? Per- haps if an improvement in quadruplex apparatus, recently de- vised with a view to dispensing with the necessity of heavy cur- rents, had been hit upon some twelve or fifteen years ago, this regrettable departure from the old practice might have been averted ; and even now it might suggest the practicability of going back to fiist jirinciples, if the advantages to be gained thereby were considered ofMntticit'nt importance to warrant the I'eversion. a Tile" iiiijii i.> piiiriii ii!tV-iir.| III I III 1 1'liiiti tiuij v» ith tnd taikjLl Ut^ -V t><: l<«L.|i:l ilii'li rui>Ul lilt: Infill ol IBS S'lRAHHIT ClIRRKNT yUADRIIl'MIX. In thiH Hystem the signulM are produced, as luw ulroudy been Htatod, by throe different strongths of current of n given polarity. Thirt method of trannnuHHion was for a long time the favorite hunting ground of inventors seeking a solution of the problem of sextuplex telegraphy. It appeared to be an easy matter to form a quadruplox on this plan, and add thereto the reversing key of the polar system and thus obtain as many as six circuits in a single conductor. It, however, came about in the long run that the formation of the quadruplex itself, according to this method, was extremely problamatical. As a matter of fact, (hero never was a straight current quadruplox in practical operation. The diflficultice that were presented in the way of its successful adop- tion have, however, been investigated in many quarters, and the Invention as a whole has in the course of time been improved to an extent that warrants its now being characterized the amplified and perfected system. That this simplified quadiuplex is fairly calculated to fill the bill already outlined for the practicable operation of the general telegraphs on currents of much less power than are at present employed, will be recognized in view of the fact that the straight current quadruplex, as a system, presents none of the objection- able features of the polar system already pointed out. There are no reversals of the current to occasion disturbance in one of the receivers, so the necessity for extraordinarily largo batterias for the operation of devices such as those described is done away with ; and thoiT; is no need to charge the line beyond the voltage of the maximum current emanating from one end alone, because a system .)f this description IS operative with either like or un- like poles to line, so there are no ill ott'ectsdueto induction com- municated to circuits adjacent, to the line upon which this qiuid- ruplex may be in operation. The impoi-tanco and value of the invention need not perhaps, in view of those facts be further emphasized. The straight current qundruplex in its simplest and perfected form is shown in the accompanying diagram. It will be noticed that the signalling battery is in one unbroken series, with its — pole to earth. The terminal and two top wiies are connected with the transmitters, which operate to put the main line in con- nection with the battery at some one of the three points tapped according to the position of the transmitter lovers, ainl in this way the requisite three strengths of current are presentable for the transmission of signals. The buttery being in one unbroken series with one pole constantly to earth, is rendered available for the supply of current to other wires or circuits independent of the quadruplex ; just as in the case where several Morse circuits are supplied from a single battery common to them all in one of the regular main offices. This is a feature of great advantage, as it obviates the necessity for separate and exclusive batteries for the operation of the quadruplox circuits. This arrangement of the battery and transmitters was supposed to have originated quite recently, along with a further improvement of the writer's to be described further on. But an examination of the fyles of the United States Patent Office disclosed the fact that its inven- tion was anticipated, as far back as January, 1877, by Benjamin Thompson, of Toledo, to whom it was patented (No. 195,055) in September of that year; and it is perhaps due to the unfortunate circumstance of its being covered in conjunction with an unwiekl}' and inadequate mass of receiving apparatus, that it never worked its way forward to the recognition that its merit deserves. As will be seen by an examination of the diagram, the transmitters are so coimected that when both of the levers are upraised the line is to earth ; when K' alone is depressed, the line connects with B'; when K" alone is depressed, the line connects with B''; and when both K' and K- are depressed, the lino connects with 15-. It follows, therefore, that K' semis the minimum current to line; K- senls the miiximuin curiTiit to line; ami when bith 4 PI KM key. togothoi- are in action, an inlermediule strength ot current ffOOBtolino. At the .listant end theio uro two roeoivoiH. One of them man ordinary dnpl.x rclu> R-' connected in the usual way • a retra.tile Hi.rini,' hold, its armutuio with a torce superior to the magnetic etle.t of the n.inimuni current, but it is respou- 8ive to the intennediato and muximum current-, ; K" tiioretore, freely and readily renponds U> the manipulation of the trans- mitter K^ The other receiver comprises the .listinctly unique feature that has raised the straight current quadruplex to its present perfection. Us contrivance is such that the sounder or recording i..slrun.ent Oi.erat.n,^' in its local circuit responds nromplly and accurately t.. the nuinipulation of k'. under the action of the minimum and intermo.liate currents, while the maximum current pro.luccs ,,p'>i. it absolutely no ellect what- ever In this arrangement the sounder is operated directly by the armature lever c .ntucts, and there is consequently no eu- feeblement of the signals and no uncertainty whatever about its anion In consequence, the transmissions on both sides are eoually rapid ami reliable. For the Information of those interested in the solution of the pn.bU-m involved, a delaile.l explanation of the receiver U' is given in the accompanying note. A test which the writer was enabled to maUe, in con.iunctu.n with Mr U. Hotl of Ottawa, on a line bolweeii this pla.:c and Toronto, nearly iJOO miles long, showed that the apparatus wouKl respond properly to currents (= -038 amp. max.) derived f.om batteries of loO cells at each end of the line. (Jn the selfsame line wire the standard polar quadruplex is regularly operated with eurrents C=0«" »'"P-) ^"1''^'"^ ''""'^ batteries of 275 cells at each end of the line; which, under certain po.ntions of the transmit- ting keys, produce* in the circuit a current of (-070x2^) -140 amp. max. from the combinati.m of the (275 x 2=) 5o0 cells. The comparison speaks for itself. Wo have now arrived at the conclusion of this paper. Its pur- pose has been to show that the practice of telegraphy today, despite the many advances that have been made in the service in one way and another, is not so scientitic as we find it to have been so long as twenty years ago. An endeavor has been made to show that the development ot the polar