501 STANDARD ELECTRICAL DICTIONARY.T.Symbol of time.Tailings.(a) In high speed transmission of telegraph signals by the automaticsystem, the definiteness of the signal marks is sometimes interferedwith by retardation. Wrong marks are thus produced called tailings.(b) The prolongation of the current at the distant receiving station ofa telegraph line due to the discharge of the line and to self-induction.Synonyms--Tailing--Tailing Current.502 STANDARD ELECTRICAL DICTIONARY.Tamidine.Reduced nitro-cellulose. Nitro-cellulose is dissolved in a propersolvent and is obtained by evaporation as a translucent solid mass. Byammonium sulphide or other reagent it is reduced so as to be virtuallycellulose. It is cut into shape for filaments of incandescent lamps,which shapes are carbonized and flashed.Tangent Law.In a galvanometer the tangents of the angles of deflection of the needleare proportional to the deflecting force--I. When the controlling force is unaltered in absolute magnitude anddirection by the motion of the needle.II. When the deflecting force acts at right angles always to thecontrolling force.These conditions are usually secured by having the actuating coilthrough which the current passes flat and of large diameter compared tothe length of the needle; by using the uniform field of the earth as thecontrol; by having a short needle; by placing the coil with its plane inthe magnetic meridian.For best proportions of tangent galvanometer coils see Bobbins.Fig. 310. GRAPHIC CONSTRUCTION OF TANGENT SCALE.Tangent Scale.An arc of a circle in which the number of graduations in any arcstarting from zero are proportional to the tangent of the anglesubtended by such arc. The system is for use with tangent galvanometers.Thus if for 45° a value of 100 is taken and marked on the scale then forthe arc 26° 33' + a value of 50 should be marked on the scale becausesuch are the relative values of the tangents.Thus the scale instead of being divided into degrees is divided intoarcs of varying length, growing shorter as they are more distant fromthe zero point, of such length that the first division being subtendedby a tangent of length 1, the first and second divisions added or takentogether as one arc are subtended by a tangent of length 2, and so on.In the cut a simple method of graphically laying out a tangent scale isshown. In it C is the centre of the arc, and H the radius running to thezero of the instrument. From C a circle is described and on H a verticalline tangent to the arc is erected. Taking any part of the tangent, asthe length shown ending at D, it is divided into any number of equalparts. Radii of the circle are now drawn whose prolongations passthrough the divisions on the tangent. These radii, where they intersectthe arc of the circle, determine equal divisions of the tangent scale,which, as is evident from the construction, are unequal angulardivisions of the arc.503 STANDARD ELECTRICAL DICTIONARY.Tanning, Electric.The tanning of hides in the manufacture of leather by the aid ofelectrolysis. A current of electricity is maintained through the tanningvats in which regular tanning liquor is contained. Very extraordinaryclaims are made for the saving of time in the tanning process. What isordinarily a process of several months, and sometimes of a year, is saidto be reduced to one occupying a few days only. The action ofelectrolysis is the one relied on to explain the results.Tapper.The key used in single needle telegraph transmitters. It comprises twoflat springs L, E, each with a handle, normally pressed upward againstone contact bar Z, and when pressed down by the operator making contactagainst a lower bar C when messages are to be transmitted. A doubletapper, such as shown, is used for each instrument.Synonyms--Double Tapper Key--Pedal Key.Fig. 311. TAPPER.Target, Electric.A target registering or indicating electrically upon an annunciator thepoint of impact of each bullet.Taste, Galvanic.The effect produced upon the gustatory nerves by the passage of anelectric current, or by the maintenance of potential difference betweentwo portions of the tongue. It is very simply produced by placing asilver coin above, and a piece of zinc below the tongue, or the reverse,and touching their edges. A sour, peculiar taste is at once perceived.It cannot be due to any measurable quantity of current or ofelectrolytic decomposition, because the couple can do little more thanestablish a potential difference. With a strong current the tastebecomes too strong for comfort, and if on a telegraph line the extracurrents produced by the signaling make the operation of tasting thecurrent a very unpleasant one. It is said that messages have beenreceived in this way, the receiver placing one terminal of the line onhis tongue, and a terminal attached to a grounded wire below it, andthen receiving the Morse characters by taste.504 STANDARD ELECTRICAL DICTIONARY.Teazer.Originally a fine wire coil wound on the field magnets of a dynamo inshunt with the regular winding to maintain the magnetism. It wasoriginally used in electroplating machines to prevent inversion of themagnetism, but has since developed into a component part of the windingof the compound dynamo. (See Dynamo, Compound.)Tee, Lead.A lead pipe of T shape used for connecting branches to electric cables.The tee is soldered by wiped joints to the lead sheathings of the cableand branches after the wires have been connected, and the junctionscoated with insulating tape or cement, or both.It is sometimes made in two halves, and is known as a split tee.Tel-autograph.A telegraph for reproducing the hand-writing of the sender at thereceiving end of the line. To save time a special spelling is sometimesused.Teleautograph.The special spelling used with the Tel-Autograph telegraph.Tele-barometer, Electric.A barometer with electric attachment for indicating or recording at adistance the barometric readings.Telegraph, ABC.This term is applied to alphabet telegraphs indicating the message bythe movements of a pointer on a dial marked with the characters to besent. In England the Wheatstone ABC system is much employed.Telegraph, Automatic.A telegraph system based on the operation of the transmitting instrumentby a perforated strip of paper drawn through it. The perforations madeby an apparatus termed a perforator, are so arranged as to givetelegraphic characters of the Morse or International Code in thetransmitting instrument. (See Perforator.) Bain in the year 1846 was theoriginator of the system. He punched a fillet of paper with dots anddashes, and drew it between two terminals of the line, thus sending overthe line a corresponding series of short and long currents which werereceived by his chemical receiver. (See Chemical Receiver.) The methodwas not successful. Its modern development, the Wheatstone AutomaticTelegraph, is highly so. The perforated paper by its perforationscontrols the reciprocating movement of two rods, which pass through eachhole in two rows, corresponding to the two rods respectively as theholes come opposite to the ends of the rods. The rods are keptconstantly moving up and down. If unperforated paper is above them theirupward motion is limited. This gives three positions for the rods, (a)both down, (b) one up and the other down, (c) both up. These positionsof the rods work a pole changing key by which dots, spaces, and dashesare transmitted to the receiving instrument, which is an exceedinglydelicate ink-printer. The latter can have its speed adjusted to receivefrom 200 to 450 words per minute.505 STANDARD ELECTRICAL DICTIONARY.Telegraph, Dial.A telegraph in which as receiver a dial instrument is used. A pointer orindex hand moves around a dial. The dial is marked with letters of thealphabet. The movements of the pointer are controlled by thetransmitting operator at a distant station. He by the same actions movesa pointer on a duplicate instrument before him and the two aresynchronized to give identical indications. Thus a message is spelledout letter by letter on both dials simultaneously. The motions of theindex are generally produced by what is virtually a recoil escapement.The scape wheel is carried by the axle of the index, and a pallet oranchor is vibrated by an electro-magnet whose armature is attached tothe stem of the pallet. As the pallet is vibrated it turns the wheel andindex one tooth for each single movement. There are as many teeth in thewheel as there are characters on the dial. The two instruments being induplicate and synchronized, the pallets move exactly in unison, so thatidentical readings of the dials are given. The pallets may be moved byany kind of make and break mechanism, such as an ordinary telegraph key.The index moves by steps or jerks, so that the system is sometimescalled step-by-step telegraphy.Fig. 312. DIAL TELEGRAPH.In the cut the make and break transmitter is shown at v v, with itshandle and contacts g and t. This mechanism sends impulses of current byF and Z to the receiving magnet l. This attracts and releases itsarmature K from contact into the position indicated by the dotted lines.This works the rocker n on the pin o, and actuates the double or anchorpawl s r, which turns the pallet or scrape wheel m.The system is dropping into disuse, being supplanted by the telephone.Synonym--Step-by-step Telegraph.506 STANDARD ELECTRICAL DICTIONARY.Telegraph, Double Needle.A telegraph system in which the message is read by the motions of twovertical needles on the face of the instrument in front of the receivingoperator. An identical instrument faces the transmitting operator. Bytwo handles, one for each hand, the needles are caused by electricimpulses to swing to right and to left so as to give a telegraphic code.It has been generally superseded by the single needle telegraph.Telegraph, Duplex.A telegraph capable of transmitting simultaneously two messages over onewire. The methods of effecting it are distinct from those of multiplextelegraphy. This term is used as a distinction from diode multiplextelegraphy, in which the work is done on other principles. There are twosystems of duplex telegraphy, the differential and the bridge systems.Telegraph, Duplex Bridge.A system of duplex telegraphy employing the principle of the Wheatstonebridge. The other or differential system depends on equality ordifference of currents; the bridge method on equality or difference ofpotentials. The cut shows the system known as Steam's Plan.At the ends of the line wire are two cross connections like duplicategalvanometer connections in a Wheatstone bridge, each including areceiving relay. The rest of the connections are self-explanatory.When A depresses his key the current splits at the point indicating thebeginning of the bridge. One portion goes through the line to B and toearth, the other goes to earth at A through the rheostats indicated bythe corrugated lines.On reaching B's end the current divides at the cross-connection and partgoes through the receiving relay shown in the center of thatcross-connection.Thus if A sends to B or B to A it is without effect on the homereceiving instrument. Now suppose that both simultaneously are sendingin opposite directions. If the connections be studied it will be seenthat every movement of the transmitting key will affect the balance ofthe distant or receiving end of the bridge and so its instrument willrecord the signals as they are sent.As shown in the cut the sending keys are on local circuits, and workwhat are known as duplex transmitters. These are instruments which sendline signals without breaking the connection.Fig. 313. STEARN'S PLAN OF DUPLEX BRIDGE TELEGRAPHY.In Stearn's plan condensers are introduced as shown. By this plandifferent receiving instruments can be used. The inventor once worked aMorse instrument at one end of the line, and a Hughes' instrument at theother end.507 STANDARD ELECTRICAL DICTIONARY.Telegraph, Duplex, Differential.A system of duplex telegraphy employing the differential action of twoexciting or magnetizing coils. The general principles are the following.Suppose that at each of two stations, there is a magnet working as asounder or relay. Each magnet is differentially wound, with two coils ofopposite direction, of identical number of turns.When the sending key at a station A is depressed two exactly equalcurrents go through the magnet in opposite directions. One called thecompensation current goes to the earth at the stations. The other calledthe line current goes through the line, through the line coil of thedistant station E, thereby actuating the relay or sounder armature.The instrument of the sender A is unaffected because he is sendingopposite and equal currents through its two coils. A special resistanceis provided on the compensation circuit for keeping the currents exactlyequal in effect. Nothing the sender at A does affects his owninstrument.Now suppose E desires to telegraph back at the same time that A istelegraphing to his station. He works his key. This does not affect hisown instrument except by sending the equal and opposite currents throughits coils. When his key is depressed and A's key is untouched, he worksA's receiving instrument.508 STANDARD ELECTRICAL DICTIONARY.When A's key is depressed simultaneously with B's key, the two linecurrents are in opposition and neutralize each other. This throws outthe balance in the instruments and both armatures are attracted by thecompensation currents left free to act by the neutralization of the linecurrents.Fig. 314. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEMSuppose that B is sending a dash, and it begins while A's key is raised.The line and compensation currents in B's receiving instrumentneutralize each other and no effect is produced, while A's receivinginstrument begins to register or indicate a dash. Now suppose A startsto send a dash while B's is half over. He depresses his key. This sendsthe two opposite currents through his magnet. His line currentneutralizes B's working current so that the compensation currents inboth receiving instruments hold the armatures attracted for the twodashes. Meanwhile A's dash ends and he releases his key. At once hisline current ceases to neutralize B's line current, his receivinginstrument is actuated now by B's line current, while B's receivinginstrument ceases to be actuated by the compensation current.Two assumptions are made in the above description. The line currents areassumed to be equal in strength and opposite in direction at eachstation. Neither of these is necessary. The line current received at astation is always weaker than the outgoing line current, and it is thepreponderance of the compensation current over the partly neutralizedline current that does the work. As this preponderance is very nearlyequal to the line current received from the distant station, the signalsare actuated by almost the same current, whether it is compensation orline current.509 STANDARD ELECTRICAL DICTIONARY.Both line currents may coincide in direction. Then when the two keys aredepressed, a line current of double strength goes through both receivinginstruments and both work by preponderance of the double line currentover the compensation current. In other respects the operation is thesame as before described.Fig. 315. DUPLEX TELEGRAPH, DIFFERENTIAL SYSTEM.Fig. 316. DIFFERENTIAL DUPLEX TELEGRAPH CONNECTIONS.The cut shows a diagram of the operation of one end of the line. R and Rare resistances, E and E are earth contacts, and the two circles showthe magnet of the receiving instrument wound with two coils inopposition. The battery and key are also shown. It also illustrates whathappens if the key of the receiver is in the intermediate positionbreaking contact at both 1 and 2. The sender's line current then goesthrough both coils of the receiving instrument magnet, but this time inseries, and in coincident direction. This actuates the instrument asbefore. Owing to the resistance only half the normal current passes, butthis half goes through twice as many coils or turns as if the receiver'skey was in either of the other two positions.In actual practice there are many refinements. To compensate for thevarying resistance of the line a rheostat or resistance with slidingconnection arm is connected in the compensation circuit so that theresistance can be instantly changed. As the electro-static capacity ofthe line varies sectional condensers are also connected in thecompensation circuits.510 STANDARD ELECTRICAL DICTIONARY.Telegraph, Facsimile.A telegraph for transmitting facsimiles of drawing or writing. Themethods employed involve the synchronous rotation of two metalliccylinders, one at the transmitting end, the other at the receiving end.On the transmitter the design is drawn with non-conducting ink. A tracerpresses upon the surface of each cylinder and a circuit is completedthrough the two contacts. In operation a sheet of chemically preparedpaper is placed over the surface of the receiving cylinder. The twocylinders are rotated in exact synchronism and the tracers are traversedlongitudinally as the cylinders rotate. Thus a number of makes andbreaks are produced by the transmitting cylinder, and on the receivingcylinder the chemicals in the paper are decomposed, producing marks onthe paper exactly corresponding to those on the transmitting cylinder.Synonyms--Autographic Telegraph--Pantelegraphy.Telegraph, Harmonic Multiplex.A telegraph utilizing sympathetic vibration for the transmission ofseveral messages at once over the same line. It is the invention ofElisha Gray. The transmitting instrument comprises a series of vibratingreeds or tuning-forks, each one of a different note, kept in vibrationeach by its own electro-magnet. Each fork is in its own circuit, and allunite with the main line so as to send over it a make and break currentcontaining as many notes superimposed as there are tuning forks. At theother end of the line there are corresponding tuning forks, each withits own magnet. Each fork at this end picks up its own note from themakes and breaks on the main line, by the principle of sympatheticvibration.To each pair of operators a pair of forks of identical notes areassigned. As many messages can be transmitted simultaneously as thereare pairs of forks or reeds.The movements of a telegraph key in circuit with one of the transmittingreeds sends signals of the Morse alphabet, which are picked out by thetuning fork of identical note at the other end of the line.511 STANDARD ELECTRICAL DICTIONARY.Telegraph, Hughes'.A printing telegraph in very extensive use in continental Europe. Itsgeneral features are as follows:The instruments at each end of the line are identical. Each includes akeyboard like a piano manual, with a key for each letter or character.On each machine is a type wheel, which has the characters engraved inrelief upon its face. With the wheel a "chariot" as it is termed alsorotates. The type wheels at both stations are synchronized. When a keyis depressed, a pin is thrown up which arrests the chariot, and sends acurrent to the distant station. This current causes a riband of paper tobe pressed up against the face of both type wheels so as to receive theimprint of the character corresponding to the key. The faces of thewheels are inked by an inking roller.Fig. 317. ELECTRO-MAGNET OF HUGHES' PRINTING TELEGRAPH.The most characteristic feature is the fact that the current sent bydepressing a key does not attract an armature, but releases one, whichis then pulled back by a spring. The armature is restored to itsposition by the mechanical operation of the instrument. The magnet usedis a polarized electro-magnet. Coils are carried on the ends of a strongpowerful magnet. The coils are so connected that a current sent throughthem by depressing a key is in opposition to the magnetism of thepermanent magnet so that it tends to release the armature, and inpractice does so. This release permits the printing mechanism to act.The latter is driven by a descending weight, so that very slightelectric currents can actuate the instruments.Synonym--Hughes' Type Printer.Telegraphic Code.(a) The telegraphic alphabet, as of the Morse System. (See Alphabet,Telegraphic.)(b) A code for use in transmitting messages either secretly, orcomprising several words or short sentences in one word, in order toeconomize in transmission. Such codes are extensively used in commercialcable messages.512 STANDARD ELECTRICAL DICTIONARY.Telegraph, Magneto-electric.A telegraph in which the current is produced by magneto-electricgenerators. It has been applied to a considerable extent in England. TheWheatstone ABC or dial telegraph is operated by a magneto-generatorturned by hand.In this country the magneto-electric generator by which the calling bellof a telephone is rung is an example. The magneto-electric key (See Key,Magneto-electric) is for use in one kind of magneto-electrictelegraphing.Telegraph, Morse.A telegraph, characterized by the use of a relay, working a localcircuit, which circuit contains a sounder, or recorder for giving dotand dash signals constituting the Morse alphabet. The signals are sentby a telegraph key, which when depressed closes the circuit, and whenreleased opens it. The two underlying conceptions of the Morse Telegraphsystem are the use of the dot and dash alphabet, and the use of thelocal circuit, which circuit includes a receiving instrument, and isworked by a relay, actuating a local battery. It would be difficult toindicate any invention in telegraphy which has had such far-reachingconsequences as the one known as the Morse telegraph.In other places the principal apparatus of the system will be founddescribed. The cut Fig. 318, repeated here gives the general dispositionof a Morse system. (See Circuit, Local.)Fig. 318. DIAGRAM OF MORSE SYSTEM.513 STANDARD ELECTRICAL DICTIONARY.The key by which the messages are transmitted is shown in Fig. 319. M isa base plate of brass. A is a brass lever, mounted on an arbor G carriedbetween adjustable set screws D. C is the anvil where contact is made bydepressing the key by the finger piece B of ebonite. E, Fl are adjustingscrews for regulating the vertical play of the lever. H is the switchfor opening or closing the circuit. It is opened for transmission, andclosed for receiving. By screws, L L, with wing nuts, K K, the whole isscrewed down to a table.Fig. 319. MORSE TELEGRAPH KEY.In the United States the simplest disposition of apparatus is generallyused. The main line is kept on closed circuit. In it may be included alarge number of relays at stations all along the line, each with its ownlocal circuit. There may be fifty of such stations. Battery is generallyplaced at each end of the line. Very generally gravity batteries areused, although dynamos now tend to supplant them in important stations.As relays the ordinary relay is used. Its local circuit includes asounder and local battery. The latter is very generally of the gravitytype, but oxide of copper batteries (See Battery, Oxide of Copper) arenow being introduced. At main or central offices, the terminals of thelines reach switch boards, where by spring-jacks and plugs, any desiredcircuits can be looped into the main circuit in series therewith.In European practise the main line is kept on open circuit. Polarizedrelays are used to work the local circuits. The currents for these haveto be alternating in direction. When the line is not in use its ends areconnected to earth at both ends, leaving the battery out of circuit.Each intermediate station has its own main, or line battery for use whenit desires to send a message. In the American system as first described,it will be seen that the main batteries are at most two in number.For the details of the different apparatus, the following definitionsmay be consulted: Embosser, Telegraphic--Recorder, Morse--Relay--RelayConnection--Sounder.514 STANDARD ELECTRICAL DICTIONARY.Telegraph, Multiplex.A system of telegraphy by which a number of messages can be transmittedin both directions over a single wire. The principles underlying thesystems are the following:Suppose that at the two extremities of a telegraph line two arms arekept in absolute synchronous rotation. Let the arms in their rotation,press upon as many conducting segments as there are to be transmissionsover the line. A transmitting and receiving set of instruments may beconnected to one segment at one end of the line, and another set to thecorresponding segment at the distant station. For each pair of segmentstwo sets can be thus connected. Then if the arm rotates so rapidly thatthe contacts succeed each other rapidly enough each pair of sets ofinstruments can be worked independently of the others. In practice thisrapid succession is effected by having a number of contacts made foreach pair during a single rotation of the arm or equivalent.The multiplex system has been perfected by the use of La Cour's phonicwheel (see Phonic Wheel), and brought into a practical success byPatrick B. Delany, of New York.Two phonic wheels rotate at each end of the line. They are kept insynchronous motion by two vibrating steel reeds of exactly the samefundamental note, and the axle of each wheel carries an arm whose endtrails over the contacts or distributor segments already spoken of. Thereeds are adjusted to vibrate at such speed that the trailer is incontact with each segment about 1/500 second. The number of groups ofsegments required for each working is determined by the retardation ofthe signals owing to the static capacity of the line. To convert therapidly recurring impulses of current into practically a single current,condensers are connected across the coils of the relay. One batteryserves for all the arms.Multiplex telegraphy can effect from two to six simultaneoustransmissions over one wire. For two or four transmissions the methodonly distinguishes it from duplex or quadruplex telegraphy. The termsdiode, triode, tetrode, pentode and hexode working are used to indicaterespectively the simultaneous transmission of two, three, four, five, orsix messages over one wire.It will be seen that the multiplex process really assigns to eachtransmission separate times, but divides these times into such short andquickly recurring intervals that the work is executed as if there wascontinuous contact. In no case is there the popular conception of thesending of several messages actually simultaneously over one wire. Eachsignal in reality has its own time assigned it, divided into shortperiods of high frequency, and only utilizes the line when it is free.515 STANDARD ELECTRICAL DICTIONARY.Telegraph, Over-house.An English term for telegraph lines led over houses and supported onstandards on the roofs.Telegraph Pole Brackets.Arms for carrying insulators, which arms are attached to telegraph polesor other support. They vary in style; sometimes they are straight barsof wood gained into and bolted or spiked in place; sometimes they are ofiron.Telegraph, Printing.Various telegraphs have been invented for printing in the ordinaryalphabet the messages at the receiving end of the line.Representative instruments of this class are used for transmittingdifferent market and stock reports to business offices from theexchanges. The type faces are carried on the periphery of a printingwheel, which is rotated like the hand of a dial telegraph, and againstwhose face a paper riband is pressed whenever the proper letter comesopposite to it. As each letter is printed the paper moves forward thespace of one letter. Spacing between words is also provided for. In therecent instruments two lines of letters are printed on the paper oneabove the other.In England, and on the continent of Europe, printing instruments havereceived considerable use for ordinary telegraphic work. Hughes' typeprinter and Wheatstone's ABC telegraph meet with extensive use there forordinary transmission.Telegraph, Quadruplex.Duplex telegraphy is the sending of two messages in opposite directionssimultaneously through the same wire. Duplex telegraphy is the sendingof two messages simultaneously in the same direction. The two combinedconstitute quadruplex telegraphy. [SIC]The system was suggested by Stark of Vienna and Bosscha of Leyden in1855; the successful problem was solved by Edison in 1874.The principle is based on the two orders of difference in electriccurrents; they may vary in strength or in direction. Thus we may haveone instrument which works with change of strength of current only, theother with change of direction only. The two can be worked together ifthe direction of the current can be altered without alteration ofstrength, and if strength can be altered without alteration ofdirection. Double current and single current working are so combinedthat one relay works by one system of currents and another relay by theother system. A current is constantly maintained through the line. Therelay operated by change in direction is a simple polarized relay whichworks by change of direction of current. The relay operated by change instrength is the ordinary unpolarized relay.516 STANDARD ELECTRICAL DICTIONARY.For the following description and the cuts illustrating it we areindebted to Preece and Sivewright. The cut shows the arrangement of theapparatus and connections for terminal offices."Sufficient table room is provided to seat four clerks. The apparatus isarranged for the two senders to sit together in the centre, the messagesto be forwarded being placed between them. The section on the left ofthe switch Q is known as the 'A' side, that on the right as the 'B' sideof the apparatus.K1 the reversing key, reverses the direction of the current. K2 is asimple key, known as the increment key; it is used simply to increasethe strength of the current.Fig. 320. QUADRUPLEX TELEGRAPH CONNECTIONS.The way in which the keys K1 and K2 combine their action is shown byFig. 321. E1 and E2 are the line batteries, the one having two andone-third (2-1/3) the number of cells of the other, so that if E1 be theelectro-motive force of the smaller, that of the whole combined batterywill be 3.3 E1. The negative pole of E1 is connected to z and z1 of K1and the positive pole of E2 to a of K2 through a resistance coil s. Awire, called the 'tap' wire, connects the positive pole of E1 and thenegative pole of E2 to b of K2. This wire has in it a resistance coilr2. The springs c and c1 of Kl are connected to the lever L of K2. Now,when both keys are at rest, the negative pole of E1 is to line throughz, and the positive pole of E1 to earth through b of K2 and c of K1; thepositive pole of E2 being insulated at a of K2.517 STANDARD ELECTRICAL DICTIONARY.There is thus a weak negative current flowing to line. When K1 alone isworked, the current of E1 is reversed. When K2 is worked alone, c of K1is transferred from b to a, and the strength of the negative currentgoing to line is increased through the increase of the electro-motiveforce from E1 to 3.3 E1 for the whole battery is brought into play. WhenK1 and K2 are depressed together, then the negative pole of E1 goes toearth through Z1; and the positive pole of E2 to line through a of K2and c1 of K1 and a positive current, due to the whole electro-motiveforce 3.3 E1 goes to line. Hence the effect of working K1 is simply toreverse the current, whatever its strength, while that of K2 is tostrengthen it, whatever its direction.The resistance coil s, of 100° resistance, is called a spark coil,because it prevents the high electro-motive force of the whole batteryfrom damaging the points of contact by sparking or forming an arc acrosswhen signals are sent; and the resistance r2 is made approximately equalto the combined resistance of E2 and the spark coil, so that the totalresistance of the circuit may not be altered by the working of theapparatus.Fig. 321. QUADRUPLEX TELEGRAPH.A1 and B1 (Fig. 320) are the relays which are used to respond to thechanges in the currents sent by the keys K1 and K2 at the distantstation.A, is a simple polarized relay wound differentially, each wire having aresistance of 200 [omega], and so connected up as to respond to the working ofthe reversing key K1 of the distant station. It acts independently ofthe strength of the current, and is therefore not affected by theworking of the increment key K2. It is connected up so as to completethe local circuit of the sounder S1 and the local battery l1 and formsthe receiving portion of the 'A' side.B, is a non-polarized relay also wound differentially, each coil havinga resistance of 200 [omega]. It responds only to an increase in thestrength of the current, and therefore only to the working of theincrement key K2 of the distant station.[Transcriber's note: In current usage upper case omega indicates ohms andlower case omega denotes angular frequency, 2*PI*f.]518 STANDARD ELECTRICAL DICTIONARY.The relay spring is so adjusted that the armatures are not actuated bythe weak current sent from E by the key K1.In its normal position this relay completes the circuit of the localbattery through the sounder S. This sounder S, called the uprightingsounder, acts as a relay to a second sounder, S2, called the readingsounder, which is worked by another local battery, l2. Of course,normally, the armature of S is held down and that of S2 is up, but whenthe tongue t moves, as it does when the increment key K2 is depressed soas to send the whole current to line, then the current from l isinterrupted, and the circuit of l2 is completed by the rising of thearmature of S, causing the reading sounder S2 to work. This is the 'B'side.R is a rheostat for balancing the resistance of the line, as used induplex working.C is a condenser used for compensating the static charge of the line. Itis provided with an adjustable retardation coil, R1, to prolong theeffect of the compensating current from the condenser.G is a differential galvanometer, used for testing, and for facilitatingadjustment and balancing.Q is a switch for putting the line to earth, either for balancing, orfor any other purpose. There is on the earth wire leading from Q aresistance coil, r1, equalling approximately the resistance of the wholebattery, 3.3 E1, and the resistance s.The connections shown in Fig. 321, are for an 'up' office. At a 'down'office it is necessary to reverse the wires on the two lower terminalsof the galvanometer and the two battery wires on the reversing key K1.The keys K1 and K2 are, for repeaters, replaced by transmitters.The adjustment of this apparatus requires great care and great accuracy.Its good working depends essentially on technical skill that can only beacquired by patience and perseverance.Faults in working generally arise from careless adjustments, dirtycontacts, loose connections, battery failures, and the ordinary lineinterruptions, but there are no troubles that are beyond the reach ofordinary skill, and it can be safely said that, within moderatedistances, wherever and whenever duplex working is practicable, thenquadruplex working is so too."The above is a typical quadruplex bridge system. There is also adifferential system, the full description of which, in addition to whathas been given, is outside of the scope of this work.519 STANDARD ELECTRICAL DICTIONARY.Telegraph Repeater.An extension of the relay system, adopted for long lines. A repeatingstation comprises in general terms duplicate repeating apparatus. Oneset is connected for messages in one direction, the other for messagesin the opposite direction. The general operation of a repeating set isas follows. The signals as received actuate a relay which by its localcircuit actuates a key, which in ordinary practise would be the sounder,but in the repeater its lever opens and closes a circuit comprising abattery and a further section of the line.Repeaters are placed at intervals along the line. Each repeater repeatsthe signals received for the next section of line with a new battery. Itrepresents an operator who would receive and repeat the message, exceptthat it works automatically.The Indo-European line from London to Teheran, 3,800 miles long, isworked directly without any hand retransmission, it being carried out byfive repeaters. This gives an average of over 500 miles for eachrepeater.[Transcriber's note: … 650 miles for each repeater.]Repeaters introduce retardation, and each repeater involves a reductionin the rate of working. Yet in many cases they increase the speed of aline greatly, as its speed is about equal to that of its worst section,which may be far greater than that of the whole line in one.Synonym--Translater.Telegraph Signal.In the telegraph alphabet, a dot, or dash; the signal or effect producedby one closing of the circuit. A dash is equal in length to three dots.The space between signals is equal to one dot; the space between lettersto three dots; and the space between words to six dots.Telegraph, Single Needle.A telegraph system in which the code is transmitted by the movements ofa needle shaped index which oscillates to right and left, the left handdeflection corresponding to dots, the right hand deflection to dashes.The instruments for sending and receiving are combined into one. Theneedles are virtually the indexes of vertical galvanometers. In one formby a tapper key (see Tapper), in another form by a key worked by adrop-handle (the drop handle instrument), currents of oppositedirections are sent down the line. These pass through both instruments,affecting both needles and causing them to swing to right or left, asthe operator moves his key.As galvanometer needle or actuating needle a soft iron needle isemployed, which is polarized by the proximity of two permanent magnets.This avoids danger of reversal of polarity from lightning, a troubleincident to the old system.520 STANDARD ELECTRICAL DICTIONARY.The cut, Fig. 322, shows a single needle telegraph instrument of thetapper form. The action of the tapper can be understood from the nextcut.Fig. 322. SINGLE NEEDLE TELEGRAPH INSTRUMENT, DOUBLETAPPER FORM.Fig. 323. DOUBLE TAPPER KEY FOR SINGLE NEEDLE TELEGRAPH.C and Z are two strips of metal to which the positive and negative polesof the battery are respectively connected. E and L are two metallicsprings; E is connected to earth, L is connected to the line; at restboth press against Z. If L is depressed so as to touch C, the currentfrom the battery goes to the line by the key L, goes through the coilsof the distant instrument and deflects the needle to one side, and thengoes to the earth. If the key E is depressed, L retaining its normalposition, the direction of the current is reversed, for the other poleof the battery is connected to the earth and the reverse current goingthrough the coils of the distant instrument deflects the galvanometerneedle to the other side.In the drop-handle type an analogous form of commutator worked by asingle handle produces the same effects.521 STANDARD ELECTRICAL DICTIONARY.Telegraph, Wheatstone, A. B. C.A magneto-electric telegraph of the dial system. An alternating currentmagneto-generator is turned by hand and by depressing keys its currentis admitted to or cut off from the line and receiver's instrument. Themessage is received by a dial instrument working by the escapementmotion described under Telegraph, Dial.Telegraph, Writing.A telegraph in which the message is received in written characters. Thetransmitter includes a stylus which is held in the hand and whose pointbears against the upper end of a vertical rod. The rod is susceptible ofoscillation in all directions, having at its base a spring supportequivalent to a universal joint.The stylus is moved about in the shape of letters. As it does this itthrows a series of resistances in and out of the circuit.At the receiving end of the line the instrument for recording themessage includes two electro-magnets with their cores at right angles toeach other and their faces near together at the point of the angle. Anarmature is supported between the faces and through it a vertical rodcarried by a spring at its bottom rises. These magnets receive currentproportional to the resistances cut in and out by the motions of theother rod at the transmitting end of the line. These resistances arearranged in two series at right angles to each other, one for eachmagnet. Thus the movements of the transmitting stylus and rod arerepeated by the end of the rod in the receiving instrument. A species ofpen is carried at the end of the rod of the receiving instrument, whichmarks the letters upon a riband of paper which is fed beneath it.Telemanometer. Electric.A pressure gauge with electric attachment for indicating or recordingits indications at a distance.It is applicable to steam boilers, so as to give the steam pressure inany desired place.Telemeter, Electric.An apparatus for electrically indicating or recording at a distance theindications of any instrument such as a pressure gauge, barometer orthermometer, or for similar work. The telemanometer applied to a boilercomes into this class of instrument.Telephotography.The transmission of pictures by the electric current, the requisitechanges in the current being effected by the action of light uponselenium. The picture is projected by a magic lantern. Its projection istraversed by a selenium resistance through which the current passes.This is moved systematically over its entire area, thus constituting thetransmitter, and synchronously with the motion of the selenium a contactpoint at the other end of the line moves systematically over a sheet ofchemically prepared paper. The paper, which may be saturated with asolution of potassium ferrocyanide and ammonium nitrate, is stained bythe passage of the current, and by the variation in intensity ofstaining, which variation is due to variations in the current, producedby the effects of the light upon the selenium, the picture isreproduced.522 STANDARD ELECTRICAL DICTIONARY.Telepherage.An electric transportation system, hitherto only used for the carryingof ore, freight, etc. Its characteristic feature is that the electricconductors, suspended from poles, supply the way on which carriagesprovided with electric motors run. The motors take their currentdirectly from the conductors.There are two conducting lines, running parallel with each other,supported at the opposite ends of transverse brackets on a row ofsupporting poles. At each pole the lines cross over so that right linealternates with left, between consecutive pairs of poles.The cars are suspended from pulleys running on one or the other of theconductors. A train of such cars are connected and the current is takenin near one end and leaves near the other end of the train. Thesecurrent connections are so distant, their distance being regulated bythe length of the train, that they are, for all but an instant at thetime of passing each of the poles, in connection with segments of theline which are of opposite potential. To carry out this principle thedistance between contacts is equal to the distance between poles. Owingto the crossing over of the lines the contacts are in connection asdescribed and thereby the actuating current is caused to go through themotors.Cars running in one direction go on the electric conductors on the oneside, those running in the other direction go on the other conductor.A great many refinements have been introduced, but the system has beenvery little used.Telephone.An instrument for the transmission of articulate speech by the electriccurrent. The current is defined as of the undulatory type. (See Current,Undulatory.)The cut shows what may be termed the fundamental telephone circuit. Aline wire is shown terminating in ground plates and with a telephone incircuit at each end. The latter consists of a magnet N S with a coil ofinsulated wire H surrounding one end. Facing the pole of the magnet is asoft iron diaphragm D, held in a frame or mouthpiece T. Any change ofcurrent in the line affects the magnetism of the magnet, causing it toattract the diaphragm more or less. The magnet and diaphragm reallyconstitute a little electric motor, the diaphragm vibrating back andforth through an exceedingly short range, for changes in the magneticattraction.The principle of the reversibility of the dynamo applies here. If themagnet is subjected to no change in magnetism, and if the diaphragm ismoved or vibrated in front of its poles, currents will be induced in thewire bobbin which surrounds its end. If two such magnets with bobbinsand diaphragms are arranged as shown, vibrations imparted to onediaphragm will send currents through the line which, affecting themagnetism of the distant magnet, will cause its diaphragm to vibrate inexact accordance with the motions of the first or motor diaphragm. Inthe combination one telephone represents a dynamo, the other a motor.If the vibrations of the diaphragm are imparted by the voice, the voicewith all its modulations will be reproduced by the telephone at thedistant end of the line.523 STANDARD ELECTRICAL DICTIONARY.Fig. 324. DIAGRAM OF BELL TELEPHONESAND LINE WITH EARTH CONNECTIONS.Fig. 325. SECTION OF BELL TELEPHONE.The above gives the essential features of the Bell telephone. Inpractice the telephone is used only as the receiver. As transmitter amicrophone is employed. To give the current a battery, generally of theopen circuit type, is used, and the current in the line is an induced orsecondary one.The microphone which is talked to, and which is the seat of the currentvariations which reproduce original sound, is termed the transmitter,the telephone in which the sounds are produced at the distant end of theline is termed the receiver.Fig. 325 shows the construction of the Bell telephone in universal usein this country as the receiver. M is a bar magnet, in a case L L. B Bis a bobbin or coil of insulated wire surrounding one end of the magnet.D is the diaphragm of soft iron plate (ferrotype metal), and E is themouthpiece. The terminals of the coil B B connect with the bindingscrews C C. The wire in the coil is No. 36, A. W. G., and is wound to aresistance of about 80 ohms.524 STANDARD ELECTRICAL DICTIONARY.As typical transmitter the Blake instrument may be cited. It is a carbonmicrophone. It is shown in section in the cut; a is the mouthpiece and eis a diaphragm of iron plate, although other substances could be used; fis a steel spring, with a platinum contact piece at its end. One endbears against the diaphragm, the other against a carbon block k. Thelatter is carried by a brass block p, and pressure is maintained betweenthese contacts by the spring g and weight of the piece c, which bygravity tends to press all together. The current passes by way of thespring f, carbon button k and spring g through the circuit indicated.A battery is in circuit with these parts. If a telephone is also incircuit, and the transmitter is spoken against, the diaphragm vibratingaffects the resistance of the carbon-platinum contact, without evenbreaking the contact, and the telephone reproduces the sound. The heavypiece of metal C acts by its inertia to prevent breaking of the contact.The position of this piece c, which is carried by the brass plate m, isadjusted by the screw n.Fig. 326. SECTION OF BLAKE TRANSMITTER.In practice the transmitter and battery are usually on a local circuit,which includes the primary of an induction coil. The line and distantreceiving telephone are in circuit with the secondary of the inductioncoil, without any battery.Telephone, Bi-.A pair of telephones carried at the ends of a curved bar or spring sothat they fit the head of a person using them. One telephone is heldagainst each ear without the use of the hands.525 STANDARD ELECTRICAL DICTIONARY.Telephone, Capillary.A telephone utilizing electro-capillarity for the production oftelephonic effects. The following describes the invention of AntoineBreguet.The point of a glass tube, drawn out at its lower end to a capillaryopening dips vertically into a vessel. This vessel is partly filled withmercury, over which is a layer of dilute sulphuric acid. The end of theimmersed tube dips into the acid, but does not reach the mercury. Oneline contact is with mercury in the tube, the other with the mercury inthe vessel. The arrangement of tube and vessel is duplicated, giving one