set for each end of the line. On introducing a battery in the circuitthe level of the mercury is affected by electro-capillarity. The tubesare closed by plates or diaphragms at their tops, so as to enclose acolumn of air. It is evident that the pressure of this air will dependupon the level of the mercury in the tube, and this depends on theelectro-motive force. On speaking against the diaphragm the sound wavesaffect the air pressure, and consequently the level, enough to causepotential differences which reproduce the sound in the other instrument.Fig. 327. BREGURT'S CAPILLARY TELEPHONE.Telephone, Carbon.A telephone transmitter based on the use of carbon as a material whoseresistance is varied by the degree of pressure brought to bear upon it.Undoubtedly the surface contact between the carbon and the otherconducting material has much to do with the action. Many carbontelephones have been invented. Under Telephone the Blake transmitter isdescribed, which is a carbon telephone transmitter. The Edison carbontransmitter is shown in section in the cut. E is the mouth piece and Dthe diaphragm. I is a carbon disc with adjusting screw V. A platinumplate B B, with ivory button b, is attached to the upper surface of thecarbon disc. C C is an insulating ring. The wire connections shown bringthe disc into circuit. It is connected like a Blake transmitter. It isnow but little used.Fig. 328. SECTION OF EDISON CARBON TRANSMITTER.526 STANDARD ELECTRICAL DICTIONARY.Telephone, Chemical.A telephone utilizing chemical or electrolytic action in transmitting orreceiving. The electro-motograph is an example of a chemical receiver.(See Electro-motograph.)Telephone, Electrostatic.A telephone utilizing electrostatic disturbances for reproduction of thevoice. In the cut D and C are highly charged electrophori. Thediaphragms A and B when spoken to affect the potential of theelectrophorus so as to produce current variations which will reproducethe sound. Dolbear and others have invented other forms of transmittersbased on electrostatic action. Receivers have also been constructed. Asimple condenser may be made to reproduce sound by being connected witha powerful telephone current.Fig. 329. DIAGRAM OF EDISON'S ELECTROSTATIC TELEPHONE.Telephone Induction Coil.The induction coil used in telephone circuits for inducing current onthe main line. It is simply a small coil wound with two separatecircuits of insulated wire. In the Edison telephone the primary coil, incircuit with the transmitter, is of No. 18 to 24 wire and of 3 to 4 ohmsresistance. The secondary in circuit with the line and receivinginstrument is of No. 36 wire and of 250 ohms resistance. The Belltelephone induction coil has its primary of No. 18 to 24 wire wound to aresistance of 1/2 ohm, and its secondary of No. 36 wire, and of 80 ohmsresistance.527 STANDARD ELECTRICAL DICTIONARY.Telephone, Reaction.A form of telephone containing two coils of insulated wire, one of whichis mounted on the disc, and the other on the magnet pole in the usualway. These coils react upon each other so as to strengthen the effect.Telephone, Thermo-electric.A telephone transmitter including a thermo-electric battery, placed incircuit with the line. A plate of vulcanite faces it. When the soundwaves strike the vulcanite they move it backward and forward. Thesemovements, owing to the elasticity of the vulcanite, produce minutechanges of temperature in it, which affecting the thermo-electric pileproduce in the circuit currents, which passing through a Bell telephonecause it to speak. This type of instrument has never been adopted inpractice.Telephote.An apparatus for transmitting pictures electrically, the properties ofselenium being utilized for the purpose.Synonym--Pherope.Teleseme.An annunciator, displaying on a dial the object wanted by the personusing it. It is employed to transmit messages from rooms in a hotel tothe office, or for similar functions.Tele-thermometer.A thermometer with electric attachment for indicating or recording itsindications at a distance.Tempering, Electric.A process of tempering metals by electrically produced heat. The articleis made part of an electric circuit. The current passing through itheats it, thereby tempering it. For wire the process can be madecontinuous. The wire is fed from one roll to another, and if requiredone roll may be immersed in a liquid bath or the wire between the rollsmay be led therein. The current is brought to one roll and goes throughthe wire to the other. As it does this the wire is constantly fed fromone roll to another. The bath may be used as described to cool it afterthe heating. The amount of heating may be regulated by the rate ofmotion of the wire.528 STANDARD ELECTRICAL DICTIONARY.Ten, Powers of.This adjunct to calculations has become almost indispensable in workingwith units of the C. G. S. system. It consists in using some power of 10as a multiplier which may be called the factor. The number multipliedmay be called the characteristic. The following are the generalprinciples.The power of 10 is shown by an exponent which indicates the number ofciphers in the multiplier. Thus 10^2 indicates 100; 10^3 indicates 1,000and so on.The exponent, if positive, denotes an integral number, as shown in thepreceding paragraph. The exponent, if negative, denotes the reciprocalof the indicated power of 10. Thus 10^-2 indicates 1/100; 10^-3 indicates1/1000 and so on.The compound numbers based on these are reduced by multiplication ordivision to simple expressions. Thus: 3.14 X 10^7 = 3.14 X 10,000,000 =31,400,000. 3.14 X 10^-7 = 3.14/10,000,000 or 314/1000000000. Regard mustbe paid to the decimal point as is done here.To add two or more expressions in this notation if the exponents of thefactors are alike in all respects, add the characteristics and preservethe same factor. Thus:(51X 10^6) + (54 X 10^6) = 105 X 10^6.(9.1 X 10^-9) + (8.7 X 10^-9) = 17.8 X 10^-9.To subtract one such expression from another, subtract thecharacteristics and preserve the same factor. Thus:(54 X 10^6) - (51 X 10^6) = 3 X 10^6.If the factors have different exponents of the same sign the factor orfactors of larger exponent must be reduced to the smaller exponent, byfactoring. The characteristic of the expression thus treated ismultiplied by the odd factor. This gives a new expression whosecharacteristic is added to the other, and the factor of smaller exponentis preserved for both,Thus:(5 X 10^7) + (5 X10^9) = (5 X 10^7) + (5 X 100 X 10^7) = 505 X 10^7.The same applies to subtraction. Thus:(5 X 10^9) - (5 X 10^7) = (5 X 100 X 10^7) - (5 X 10^7) = 495 X 10^7.If the factors differ in sign, it is generally best to leave theaddition or subtraction to be simply expressed. However, by followingthe above rule, it can be done. Thus:Add5 X 10^-2 and 5 X 10^3.5 X 10^3 = 5 X 10^5 X 10^-2(5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2This may be reduced to a fraction 500000/100 = 5000.05.To multiply add the exponents of the factors, for the new factor, andmultiply the characteristics for a new characteristic. The exponentsmust be added algebraically; that is, if of different signs thenumerically smaller one is subtracted from the other one, and its signis given the new exponent.Thus;(25 X 10^6) X (9 X 10^8) = 225 X 10^14.(29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1(9 X 10^8) X (98 X 10^2) = 882 X 10^1529 STANDARD ELECTRICAL DICTIONARY.To divide, subtract (algebraically) the exponent of the divisor fromthat of the dividend for the exponent of the new factor, and divide thecharacteristics one by the other for the new characteristic. Algebraicsubtraction is effected by changing the sign of the subtrahend,subtracting the numerically smaller number from the larger, and givingthe result the sign of the larger number.(Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2.)Thus;(25 X 10^6) / (5 X 10^8) = 5 X 10^-2(28 X 10^-8) / (5 X 10^3) = 5.6 X 10^-11[Transcriber's note: I have replaced ordinary exponential notation bythe more compact and simpler "programming" representation. The last twoexample would be:25E6 / 5E8 = 5E-228E-8 / 5E3 = 5.6E-11]Tension.Electro-motive force or potential difference in a current system isoften thus termed. It is to be distinguished from intensity or currentstrength, which word it too greatly resembles.Tension, Electric.(a) The condition an electrified body is brought into byelectrification, when each molecule repels its neighbor. The conditionis described as one of self-repulsion.(b) The voltage or potential difference of a circuit is also thustermed.Terminal.The end of any open electric circuit, or of any electric apparatus; asthe terminals of a circuit, dynamo, or battery.Terminal Pole.In telegraph line construction the last pole of a series; one beyondwhich the line is not carried. Such pole, as the pull of the wires isall in one direction, requires special staying or support. The regularline poles are free from this strain, as the wire pulls in bothdirections.Tetanus, Acoustic.A term in electro-therapeutics. An effect produced on a nerve by veryrapidly alternating induced currents. The currents are produced by aninduction coil with a vibrator giving a musical note. This is a speciesof gauge of proper frequency of alternations.Theatrophone.An apparatus worked by automatic paying machinery by which a telephoneconnection is made with a theatre or opera by the deposition of a coinin a slot.Therm.A unit of heat. It has been proposed by the British Association andamounts to a redefinition of the smaller calorie. It is the amount ofheat required to raise the temperature of one gram of water one degreecentigrade, starting at the temperature of maximum density of water.530 STANDARD ELECTRICAL DICTIONARY.Thermaesthesiometer.An electro-therapeutic instrument for testing the sensitiveness of thesurface of the body to changes of temperature. Vessels of mercury areprovided with thermometers to indicate their temperature. One vessel issurrounded by an electric conductor wound in a number of turns. Thetemperature is raised by passing a current through this. By successiveapplications of the vessels to the same spot upon the skin the power ofdifferentiating temperatures is determined.Thermo Call.(a) An electric alarm or call bell operated by thermo-electric currents.It may serve as a fire alarm or heat indicator, always bearing in mindthe fact that differential heat is the requisite in a thermo-electriccouple.(b) See Thermo-electric Call.Thermo-chemical Battery.A voltaic battery in which the electro-motive force is generated bychemical action induced by heat.The chemical used generally is sodium nitrate or potassium nitrate. Thepositive plate is carbon. On heating the battery the nitrate attacks thecarbon, burning it and produces potential difference. For negative platesome metal unattacked by the nitrate may be employed.Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY.Thermo-electric Battery or Pile.A number of thermo-electric couples q. v., connected generally inseries.In Nobili's pile the metals are bismuth and antimony; paper bandscovered with varnish are used to insulate where required. In Becquerel'spile copper sulphide (artificial) and German silver, (90 copper, 10nickel) are the two elements. The artificial copper sulphide is madeinto slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about).Water is used to keep one set of junctions cool, and gas flames to heatthe other set. In Fig. 331, c, d represent the binding screws. Thecouples are mounted on a vertical standard, with adjusting socket andscrew B, so that its lower end can be immersed in cold water, or raisedtherefrom as desired.531 STANDARD ELECTRICAL DICTIONARY.FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES.Fig. 332 shows one couple of the battery. S is artificial antimonysulphide; M is German silver; m is a protecting plate of German silverto save the sulphide from wasting in the flame.Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES.Clamond's pile has been used in practical work. The negative element isan alloy of antimony, 2 parts, zinc, 1 part. The positive element is tinplate. Mica in some parts, and a paste of soluble glass and asbestus inother parts are used as insulators. They are built up so as to form acylinder within which the fire is maintained. The air is relied on tokeep the outer junctions cool. The temperature does not exceed 200° C.(392° F.)Sixty such elements have an electro-motive force of 300 volts and aninternal resistance of 1.5 ohms. Such a battery requires the consumptionof three cubic feet of gas per hour. (See Currents, Thermo-electric. )532 STANDARD ELECTRICAL DICTIONARY.Thermo-electric Call.A thermostat arranged to ring a bell or to give some indication when thetemperature rises or falls beyond certain points. It may be a compoundbar of brass and steel fixed at one end and free for the rest of itslength. Its end comes between two adjustable contacts. As thetemperature rises it bends one way (away from the brass side) and, ifhot enough, touching a contact gives one signal. If the temperaturefalls it curves the other way, and if cold enough touches the othercontact, giving another signal. (See Thermostat, Electric.)Thermo-electric Couple.If two dissimilar conductors form adjacent parts of a closed circuit,and their junction is at a different temperature than that of the restof the circuit, a current will result. Such pair of conductors arecalled a thermo-electric couple. They may be joined in series so as toproduce considerable electro-motive force. (See Thermo-electricity andother titles in thermo-electricity.)The efficiency of a thermo-electric couple according to the second lawof thermo-dynamics is necessarily low--not over 10 per cent.Thermo-electric Diagram.A diagram indicating the change in potential difference for a fixeddifference of temperature between different metals at differenttemperatures. It is laid out with rectangular co-ordinates. On one axistemperatures are laid off, generally on the axis of abscissas. On theother axis potential differences are marked. Different lines are thendrawn, one for each metal, which show the potential difference, say forone degree centigrade difference of temperature between their junctions,produced at the different temperatures marked on the axis of abscissas.Fig. 333. THERMO-ELECTRIC DIAGRAM,GIVING POTENTIAL DIFFERENCE IN C. G. S. UNITS.Thus taking copper and iron we find at the temperature 0° C. (32° F.) adifference of one degree C. (1.8° F.) in their junctions will produce apotential difference of 15.98 micro volts, while at 274.5° C. (526.1°F.) the lines cross, and zero difference of potential is indicated.Taking the lead line on the same diagram it crosses the iron line alittle above 350° C. (662° F.), indicating that if one junction isheated slightly above and the other is heated slightly below thistemperature no potential difference will be produced. Lead and copperlines, on the other hand, diverge more and more as the temperaturerises.533 STANDARD ELECTRICAL DICTIONARY.Thermo-electric Inversion.The thermo-electric relations of two conductors vary at differenttemperatures. Sometimes at a definite point they have no electro-motiveforce and after passing this point the positive plate becomes a negativeone and vice versa. This is inversion, or reversal. (See Thermo-electricDiagram.)Synonym-- Thermo-electric Reversal.Thermo-electricity.Electric energy, electro-motive force or electrification produced fromheat energy by direct conversion. It is generally produced in a circuitcomposed of two electric conductors of unlike material, which circuitmust possess at least two junctions of the unlike substances. By heatingone of these to a higher temperature than that of the other, or bymaintaining one junction at a different temperature from that of theother a potential difference is created accompanied by an electriccurrent.In many cases differential application of heat to an identical materialwill develop potential difference. This effect, the converse of theThomson effect, is not used to produce currents, as in a closed circuitthe potential differences due to differential heating would neutralizeeach other.Thermo-electric Junction.A junction between two dissimilar conductors, which when heated orcooled so as to establish a differential temperature, as referred to thetemperature of the other junction, produces potential difference and anelectric current.Thermo-electric Pile, Differential.A thermo-electric pile arranged to have opposite faces subjected todifferent sources of heat to determine the identity or difference oftemperature of the two sources of heat. It corresponds in use to adifferential air thermometer.Thermo-electric Power.The coefficient which, multiplying the difference of temperature of theends of a thermo-electric couple, gives the potential difference,expressed in micro-volts. It has always to be assigned to a mean oraverage temperature of the junctions, because the potential differencedue to a fixed difference of temperature between two metals varies withthe average temperature of the two junctions. (See Thermo-electricDiagram.)For bismuth and antimony at 19.5° C. (67.1° F.) it is 103 microvolts perdegree Centigrade (1.8° F.). This means that if one junction is heatedto 19° C. and the other to 20° C. (66.2° F. and 68.0° F.) a potentialdifference of 103 micro-volts will be produced.The potential difference is approximately proportional to the differenceof temperature of the two junctions if such difference is small. Hencefor large differences of potential the thermo-electric power coefficientdoes not apply.As a differential function it is thus deduced by Sir William Thomson,for expressing the E. M. F. in a thermo-electric circuit: If a circuitis formed of two metals with the junctions at indefinitely neartemperatures, t and t + dt, and dE is the E. M. F. of the circuit, thenthe differential coefficient dE/dt is called the thermo-electric powerof the two metals for the temperature t.534 STANDARD ELECTRICAL DICTIONARY.Thermo-electric Series.The arrangement of possible thermoelectric elements, q. v., in a tablein the order of their relative polarity. Bismuth and antimony form acouple in which when their junction is heated the bismuth acts as thepositive or negatively charged element and antimony as the negative orpositively charged. Between these two extremes according to Seebeck theseries runs as follows:Antimony, Silver, Copper,Arsenic, Gold, Platinum,Iron, Molybdenum, Palladium,Steel, Tin, Cobalt,Cadmium, Lead, Nickel,Tungsten, Mercury, Bismuth.Zinc, Manganese,A differential temperature of 1° C. (1.8° F.) in a bismuth-antimonycouple maintains a potential difference of 103 micro-volts.Matthiessen gives a different series; it is arranged in two columns; thefirst column has positive coefficients annexed the second has negative.On subtracting the greater one from the lesser, which, if the twoelements are in different columns, of course amounts to adding afterchanging the negative sign, the relative potential difference due to thecombination is obtained.+ -Bismuth 25 Gas Coke 0.1Cobalt 9 Zinc 0.2Potassium 5.5 Cadmium 0.3Nickel 5 Strontium 2.0Sodium 3. Arsenic 3.8Lead 1.03 Iron 5.2Tin 1 Red Phosphorous 9.6Copper 1 Antimony 9.8Silver 1 Tellurium 179.9Platinum 0.7 Selenium 290Thus the relative E. M. F. of a bismuth-nickel couple, as both are inthe + column, would be 25 - 5 = 20; that of a cobalt-iron couple, onebeing in the + column the other in the - column, would be 9 + 5.2 =14.2. Alloys are not always intermediate to their constituents, andsmall amounts of impurities affect the results largely. This may accountfor the discrepancies of different observers. Other compounds could beintroduced into the series.Artificial silver sulphide has been used by Becquerel in athermo-electric battery.535 STANDARD ELECTRICAL DICTIONARY.Thermo-electric Thermometer.A species of differential thermometer. It consists of twothermo-electric junctions connected in opposition with a galvanometer inthe circuit. Any inequality of temperature in the two ends or junctionsproduces a current shown by the galvanometer. It may be used todetermine the temperature of a distant place, one of the junctions beinglocated there and the other being under control of the operator. If thelatter junction is heated until no current is produced its temperatureis evidently equal to that of the distant couple or junction. Theheating may be done with hot water or mercury, or other melted metal.The temperature of the water, or other substance, gives the temperatureof the distant place.Thermolysis.Decomposition by heat; dissociation. All compound bodies aredecomposable by heat if it is intense enough. Hence at very elevatedtemperatures there can be no combustion.Synonym--Dissociation.Thermometer.An instrument for indicating the intensity of heat. Three scales ofdegrees of heat are used in practise, the Fahrenheit, Réamur, andCentigrade, each of which is described under its own title. (See Zero,Thermometric-Zero, Absolute.) The ordinary thermometer depends on theexpansion of mercury; in some cases alcohol is used. Besides these thecompound bar principle as used in the thermostat (see Thermostat,Electric) is employed.Thermometer, Electric.(a) A thermometer whose indications are due to the change of resistancein conductors with change of temperature. Two exactly similar resistancecoils maybe electrically balanced against each other. On exposing one toa source of heat, its resistance will change and it will disturb thebalance. The balance is restored by heating the other coil in a vesselof water when the temperature of the water gives the temperature of bothcoils. The coils are enclosed in water-tight metallic cases.Synonym--Electric Resistance Thermometer.(b) A differential thermometer may be made by connecting with a pair ofconductors, two thermo-electric couples in opposition to each other, andincluding a galvanometer in series. On heating the junction of onecouple more than that of the other a current at once goes through thegalvanometer.(c) (See Thermometer, Kinnersley's.)Synonym--Thermo-electrometer.536 STANDARD ELECTRICAL DICTIONARY.Fig. 334. KINNERSLEY'S THERMOMETER.Thermometer, Kinnersley's.A thermo-electrometer. A large glass tube is mounted on a standard andcommunicates with a small tube parallel to it. Water is poured in so asto rise in the small tube. Two wires terminating in bulbs enter thelarge tube by its top and bottom. The upper wire can be adjusted bymoving up and down through a stuffing box. On discharging a Leyden jarthrough the space between the knobs on the two wires the water for amoment rises in the small tube. There is little or no accuracy in theinstrument. It is allied to the electric mortar (see Mortar, Electric)as a demonstrative apparatus.Synonyms--Electric Thermometer--Thermo-electrometer.Thermo-multiplier.A thermo-electric battery including a number of couples. The term isgenerally applied to a small battery with its similar junctions facingin one direction and used for repeating Melloni's experiments on radiantenergy, or so-called radiant heat.537 STANDARD ELECTRICAL DICTIONARY.Thermophone.An apparatus for reproducing sounds telephonically by the agency ofheat; a receiving telephone actuated by heat. Thus a wire may beattached to the centre of a diaphragm and kept in tension therefrom, andthe transmitting telephone current may be caused to pass through it. Thewire changes in temperature and consequently in length with the pulsesof current going through it and vibrates the diaphragm, reproducing thesound. It is to be distinguished from the thermo-electric telephonewhich involves the action of potential difference produced bythermo-electric action.Thermostat, Electric.A thermostat or apparatus, similar to a thermometer in some cases, forclosing an electric circuit when heated. It is used in connection withautomatic fire alarms to give warning of fire. For this use atemperature of 52° C. (125° F.) is an approved one for setting one at,to complete the circuit. It is also applied to regulation oftemperature, as in incubators.(a) One kind of thermostat consists of a compound bar wound into aspiral and fastened at one end, to which a terminal of a circuit isconnected. The bar may be made of two strips of brass and iron rivetedtogether, and wound into a spiral. When such a bar is submitted tochanges of temperature it bends in different directions, because brassexpands and contracts more under changes of temperature than does iron.A contact point, to which the other terminal is connected, is arrangedto make contact with the spiral at any desired degree of temperature,thus closing an electric circuit and ringing a bell, opening or closinga damper, or doing anything else to notify an attendant or to directlychange the temperature.If the brass forms the outside of the spiral, increase of temperaturemakes the bending of the spiral bring the coils still closer. If thebrass forms the inside, increase of temperature makes the spiral tend tobecome less close. As shown in the cut, the brass should lie along theinside of the spiral.Sometimes a straight compound bar is used, one of whose ends is fastenedand the other is free. As the temperature changes such a bar curves moreor less, its free end moving to and fro. Two contact screws areprovided, one on each side of its free end. If the temperature falls itmakes contact with one of these; if the temperature rises, it makescontact with the other. Thus it may close one of two circuits, one for afall and the other for a rise in temperature.It is well to introduce a third bar between the brass and iron ones,made of some material of intermediate coefficient of expansion.(b) Another kind of thermostat comprises a vessel of air or other gas,which, expanding by heat, actuates a piston or other device and closesan electric circuit. Synonym--Electro-pneumatic Thermostat.(c) Another form utilizes the expansion of mercury. The mercury is madepart of an open electric circuit. As it expands it comes in contact withthe other terminal of the circuit, thus completing it, when the currentgives an alarm or does as is provided for in the apparatus employed.Thermostats may be worked on either open or closed circuits; normallythe circuit may be open as described and may close on rise oftemperature, or it may be normally closed and open as the temperaturerises.Fig. 335. ELECTRIC THERMOSTAT.538 STANDARD ELECTRICAL DICTIONARY.Thomson Effect.In an unequally heated conductor the differential heating is eitherincreased as in iron, or diminished as in copper by a current. In leadthe phenomenon does not occur. It is termed the Thomson effect. It isintimately related to the Peltier effect.In a thermo-electric couple a heated junction is the source ofelectro-motive force, if heated more than other parts of the circuit.The current in a copper-iron junction flows from the copper to the ironacross the heated junction. A hot section of an iron conductor next to acold section of the same is a source of thermoelectricity, in the sensethat the hot section is negative to the colder. A current passing fromthe hot to the cold iron travels against rising potentials, and coolsthe iron in the cooler parts. As it passes to the hotter parts ittravels against falling potentials and hence heats the iron in theseparts. In this way a current intensifies differential heating in an ironconductor.In copper the reverse obtains. In it the thermo-electric relations ofhot and cold copper are the reverse of those of iron, and a currenttends to bring all parts of a differentially heated copper conductor toan identical temperature.As a current travels in iron from hot to cold it absorbs heat; in coppertraveling from cold to hot it absorbs heat.The convection of heat by a current of electricity in unequally heatediron is negative, for it is opposed to that convection of heat whichwould be brought about by the flow of water through an unequally heatedtube. In copper, on the other hand, the electric convection of heat ispositive. (Daniell.)The above effects of the electric current upon an unequally heatedconductor are termed the Thomson effects. In iron, at low red heat, theyare reversed and are probably again reversed at higher temperatures.539 STANDARD ELECTRICAL DICTIONARY.Three Wire System.A system of distribution of electric current for multiple arc orconstant potential service. It is the invention of Thomas A. Edison.It includes three main wires which start from the central station orgenerating plant, and ramify with corresponding reduction in size,everywhere through the district or building to be lighted. As ordinarilycarried out when dynamos are used, the dynamos are arranged in groups oftwo. One lateral lead starts from the negative binding post of onedynamo. The positive terminal of this dynamo connects to the negative ofthe other. Between the two dynamos the central or neutral lead isconnected. The other lateral lead starts from the positive binding postof the second dynamo.The lamps or other appliances are calculated for the potentialdifference of a single dynamo. They are arranged between the neutralwire and the laterals, giving as even a disposition as possible to thetwo laterals.Fig. 336. DIAGRAM OF THREE WIRE SYSTEMSHOWING NEUTRAL WIRE.If evenly arranged and all burning or using current, no current goesthrough the neutral wire. If all the lamps situated on one lateral areon open circuit all the current goes through the neutral wire. In othercases the neutral wire receives the excess of current only.The advantages of the system are that it uses smaller wire than the twowire system for lamps of the same voltage. If lamps of double thevoltage were used the two wire system would be most economical.540 STANDARD ELECTRICAL DICTIONARY.Four wire and five wire systems have been more or less used, based onidentical considerations, and involving in each case the coupling ofthree or of four dynamos respectively, or else employing a dynamo withspecial armature connections to give the requisite three-fold orfour-fold division of total potential. In the five wire system the totalvoltage is four times that of a single lamp, the lamps are arranged fourin series across the leads and the central wire is the only one that canbe considered a neutral wire. When lamps are burning entirely from threeside-leads they constitute a sort of three wire system by themselves,and their central wire may for the time be a neutral wire.In some of the three wire mains, especially in the larger sizes, theneutral wire is made of much smaller section than that of a lateralconductor, because in extensive districts it is practically impossiblethat the current should be concentrated in the neutral wire.Throw.In a galvanometer the instantaneous deflection of the needle when thecontact or closing of the circuit is instantaneous, or when thedischarge is completed before the needle begins to move. The throw ofthe needle is the datum sought when the ballistic galvanometer is used.Synonym--Elongation.Throw-back Indicator.A drop annunciator, whose shutter or drop is electrically replaced.Thrust-bearings.Bearings to support the end-thrust or push of a shaft. In disc armatureswhere the field-magnets attract the armatures in the direction of theiraxis of rotation, thrust-bearings have to be provided. In ordinarycylinder or drum armatures end-thrust is not applied, as a little endmotion to and fro is considered advantageous as causing more even wearof the commutator surface.Thunder.The violent report which, as we hear it, succeeds the lightning flash instormy weather. It is really produced simultaneously with the lightningand is supposed to arise from disturbance of the air by the discharge.The rolling noise has been attributed to successive reflections betweenclouds and earth, and to series of discharges reaching the ear fromdifferent distances and through air of varying density. The subject isobscure. By timing the interval from lightning flash to the report ofthe thunder an approximate estimate of the distance of the seat ofdischarge can be made. The first sound of the thunder should be timed.An almost concurrence of thunder and lightning indicates immediateproximity of the discharge.[Transcriber's note: The speed of sound at sea level is about 5 secondsper mile.]Ticker.A colloquial name for a stock or market report automatic printingtelegraph, which prints its quotations and messages on a long tape.541 STANDARD ELECTRICAL DICTIONARY.Time Constant.(a) When current is first turned into a circuit of considerableself-induction it is resisted rather by the inductance than by theresistance. It is governed by the ratio of resistance and self-inductionand this factor represents the time which it takes for the current toreach a definite fraction of its final strength. This fraction is(2.7183 - 1)/2.7183 or 0.63. 2.7183 is the base of the Napierian systemof logarithms. Thus if in any circuit we divide the inductance inhenries by the resistance in ohms, the ratio gives the time-constant ofthe circuit, or it expresses the time which it will take for the currentto reach 0.63 of its final value.(b) In a static condenser the time required for the charge to fall to1/2.7183th part of its original value.Time Cut-outs.Cut-outs which automatically cut storage batteries out of the chargingcircuit when they are sufficiently charged.Time-fall.In a secondary battery the decrease with use of electromotive forcemaintained by a primary or secondary battery. As the battery becomesspent its voltage falls. The conditions of the fall are represented byits discharging curve. (See Curve, Discharging.)Time-reaction.A term in electro-therapeutics; the period of time occupied in thepassage of the effects of an electric current from nerve to muscle.Time-rise.In a secondary battery the increase of electromotive force producedduring the charging process. Its rate and conditions are graphicallyshown in the charging curve. (See Curve, Charging.)Tin.A metal; one of the elements; symbol, Sn; atomic weight, 117.8;equivalent, 58.9 and 29.5; valency, 2 and 4; specific gravity, 7.3.It is a conductor of electricity.Relative resistance, compressed, (Silver = 1) 8.784Specific resistance at 0° C. (32° F.), 13.21 microhms.Resistance of a wire at 0° C. (32° F.),(a) 1 foot long, weighing 1 grain, 1.380 ohms.(b) 1 foot long, 1/1000 inch thick, 79.47 "(c) 1 meter long, weighing 1 gram, .9632 "(d) 1 meter long, 1 millimeter thick, .1682 "Resistance of a 1 inch cube at 0° C. (32° F.), 5.202 microhms.Percentage of variation in resistanceper degree C. (1.8° F.), at about 20° C. (68° F.), .0365Electro-chemical equivalent (hydrogen = .0105), .619 mgs..310 "542 STANDARD ELECTRICAL DICTIONARY.Tinnitus, Telephone.A nervous affection of the ear, of the order of professional cramp; itis attributed to too much use of the telephone.Tin Sounders.A recent addition to the single needle telegraph. (See Telegraph, SingleNeedle.) It consists of small tin plates, cut and bent, and so fitted inpairs to the instrument, that the needle as deflected strikes one or theother on its right and left hand movements. The sounders can be made togive sufficiently distinctive sounds to make sound-reading, q. v.,possible. Commercial tin plate, which is really tinned iron, seems togive the best results.Fig. 337. TIN SOUNDERS.Tissandier's Solution.A solution for bichromate batteries. It is composed as follows:Water, 100 parts by weightpotassium bichromate, 16 parts66° sulphuric acid, 37 parts.Tongue of Polarized Relay.The German silver extension of the vibrating or oscillating member of apolarized relay, corresponding to the armature of an ordinary relay.Tongue of Polarized Relay, Bias of.In a Siemens' polarized relay the pole pieces are adjustable so thatthey may be brought nearer to or withdrawn from the tongue. One of thepoles is adjusted so as to be nearer the tongue. This one-sidedadjustment is the bias. Its effect is that when the relay is unexcitedthis pole attracts the armature so that it normally is drawn towards it.This ensures the normal contact of the tongue either with the contactpoint, or with the insulated stop piece or adjustment screw. Withoutbias the armature remains in contact with or drawn towards whicheverpole it was last attracted to. In its usual use a bias is given it.Top, Magnetic.A toy illustrating magnetic attraction. It consists of a disc or body oflead or other material, through which a magnetized steel spindle pointedat its lower end is thrust. A number of short pieces of iron wire areused with it. It is spun like an ordinary top upon the point of thespindle and one of the pieces of iron wire is laid by the side of itspoint. As it turns the magnetic adherence causes the piece of wire to becarried along in one direction by the rotation of the spindle, until theend is reached, when it goes over to the other side of the spindle andtravels back again.By using bent pieces of wire of various shapes the most curious effectsare produced. Circles and S shaped pieces give good effects. To increasethe mysterious effect covered iron wire (bonnet wire) may be employed.Fig. 338. MAGNETIC TOP.543 STANDARD ELECTRICAL DICTIONARY.Torpedo, Electric.(a) A fish, the Raia Torpedo, which possesses the power of givingelectric shocks. (See Ray, Electric.)(b) An instrument of war; a torpedo whose operations include electricaldischarge or other electric function or factor of operation.Torpedo, Sims-Edison.A torpedo driven by an electric motor, and also steered by electricity.Its motions are all controlled from the shore. The torpedo proper iscarried some distance below the surface of the water by a vesselimmediately above it, from which it is suspended by two rigid bars. Inthe torpedo is a cable reel on which the conducting cable is disposed.An electric motor and controlling gear are also contained within thetorpedo. In its front the explosive is placed. It is driven by a screwpropeller actuated by the electric motor. As it moves it pays out cableso that it has no cable to draw after it through the water, the cablelying stationary in the water behind it. This avoids frictionalresistance to its motion. The maintenance of the torpedo at a properdepth is one of the advantages of the system.544 STANDARD ELECTRICAL DICTIONARY.Torque.A force tending to produce torsion around an axis. An example is thepulling or turning moment of an armature of an electric motor upon itsshaft. It is often expressed as pounds of pull excited at the end of alever arm one foot long.The expression is due to Prof. James Thompson, then of the University ofGlasgow."Just as the Newtonian definition of force is that which produces ortends to produce motion (along a line), so torque may be defined as thatwhich produces or tends to produce torsion (around an axis). It isbetter to use a term which treats this action as a single definiteentity than to use terms like 'couple' and 'moment,' which suggest morecomplex ideas." (S. P. Thompson.)A force, acting with radius r gives a torque equal to f X r ; f and rmay be expressed in any units. S. P. Thompson gives the followingequivalents :To reducedyne-centimeters to gram centimeters, divide by 981dyne-centimeters to meter-kilograms divide by 981E5dyne-centimeter, to pound-feet divide by 13.56E6pound-feet to meter-kilograms divide by 7.23In each of these compound units the first unit is the force and thesecond unit is the radius or lever arm of the torque.Synonyms--Turning Moment--Moment of Couple--Axial Couple--AngularForce--Axial Force.Torsion Balance, Coulomb's.Originally an apparatus in which electrostatic attraction or repulsionis measured against the torsion of a filament, often of silk-worm cocoonfibre. It consists in one form of a cylindrical glass vessel in which alight shellac needle is suspended horizontally by a fibre. This needlecarries at one end a gilded disc or sphere and is suspended by a finewire, or filament. A proof plane, q. v., is excited by touching it tothe body under trial; it is then inserted in the case. The disc on theneedle is first attracted and then repelled. The position finally takenby the needle is noted. The force of torsion thus produced is determinedby twisting the filament by the torsion head on the top of the apparatusso as to move the needle a certain distance towards the proof plane. Themore the torsion-head has to be turned to carry the needle through aspecified arc the greater is the torsion effected or the greater is therepulsion exerted, The torsional force of a wire is proportional to theangle of torsion; this gives the basis for the measurement.With magnetic needle it is used to measure magnetic repulsion andattraction. The best material for the filament is quartz, but theinstrument is not very much used.Torsion Galvanometer.A galvanometer in which the torsion required to bring the index back tozero, when the current tends to displace it, is made the measure of thecurrent strength or of the electro-motive force. It involves the use ofa torsion head, q. v., or its equivalent.545 STANDARD ELECTRICAL DICTIONARY.Torsion Head.The handle and disc from whose undersurface the filament depends towhich the needle or magnet is attached. It is turned to measure thetorsional effect, the edge of the disc being marked or graduated so asto give the angle of deflection required to overcome the effect of thetorque of the needle.Torsion Suspension.Suspension by one or more wires, fibres, or ribands, involving therestitutive force of torsion. Thus fibre suspension, q. v., is a varietyof torsion suspension.Often a single riband of steel stretched horizontally and secured atboth ends is used, the suspended object, e. g., a balance beam, beingattached at its own centre to the centre of the stretched riband. Quitesensitive balances are constructed on this principle. It is peculiarlyavailable where an electric current is to be transmitted, as absolutecontact is secured, as in William Thomson's ampere balances.Touch.A term applied to methods of magnetization, as "single touch," "doubletouch," or "separate touch," indicating how the poles of the inducingmagnet or magnets are applied to the bar to be magnetized. Under thetitles of Magnetization the different methods are described.Tourmaline.A mineral; a subsilicate; characterized by the presence of borictrioxide, which replaces aluminum oxide. It is notable for possessingpyro-electric properties. (See Pyro-electricity.)Tower, Electric.The tower used in the tower system, q. v., of arc light illumination.Tower System.In electric lighting the system of lighting extended areas by powerfularc lamps placed on high towers, generally of iron or steel frame-work.The lights are thus maintained at a high elevation, giving greateruniformity of illumination than if they were lower, but at the expenseof considerable light which is lost. Sometimes wooden masts are employedinstead of towers.The principle involved is that the intensity of light at any place givenby a source of illumination varies with the square of its distance fromthe place in question. Hence in using strong arc lights it is an objectto have the distances of all parts of the area illuminated at as nearlyuniform distances from the light as possible. An approximation touniformity is secured by placing the lamps at a very high elevation.546 STANDARD ELECTRICAL DICTIONARY.Transformer.In alternate current lighting the induction coil by which the primarycurrent with high initial electro-motive force is caused to produce asecondary current with low initial electromotive force.A typical transformer consists of a core of thin iron sheets. Theprimary is of comparatively thin wire and often of ten or more times asmany turns as the secondary. The latter is of thicker wire. Where theratio of 10 to 1 as regards number of turns in the primary and secondaryobtains, the initial E. M. F. of the secondary is one-tenth that of theprimary circuit.The cores are laminated, as described, to avoid the formation ofFoucault currents.The counter-electro-motive force of the transformer when the secondarycircuit is open, prevents any but the slightest current from passingthrough the primary. In proportion as the secondary is closed and itsresistance diminished, as by lighting more lamps in parallel, the