. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . this is a cover M, M provided witha suitable cavity for directing the sound-waves against the dia-phragm. The microphonic arrangement consists of a spring S,about the hundredth of an inch thick and the eighth of an inchbroad, fixed at one end to a lever L, and carrying at its free ex-tremity a brass block W. In one side of W a small disk C of gascarbon is inserted, resting on the hemispherical end of a smallplatinum pin K, about the twentieth of an inch in diameter, heldin position by a thin spring A. T
. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . this is a cover M, M provided witha suitable cavity for directing the sound-waves against the dia-phragm. The microphonic arrangement consists of a spring S,about the hundredth of an inch thick and the eighth of an inchbroad, fixed at one end to a lever L, and carrying at its free ex-tremity a brass block W. In one side of W a small disk C of gascarbon is inserted, resting on the hemispherical end of a smallplatinum pin K, about the twentieth of an inch in diameter, heldin position by a thin spring A. The pressure of the carbon on theplatinum point can be adjusted by the screw N, which turns thelever about the flexible joint G. The electrical connexions of theinstrument as arranged for actual use are also illustrated in thefigure. ^The curreat circuit gots through S, W, C, K, A, and the primary circuit of the induction coil I to the battery B, and thenc*to S again. This forms a local circuit at the transmitting line of circuit passes through the secondary of the inductioo. Fio. 13.— Blakea transmitter. coil I to the line, from that to the telephone T at the receivingstation, and then either to earth or back to the induction coil bya return line of wire. Telephonie Circuits. The lines used for telephone purposes are, generally speaking; Tele*BO far as erection, mode of inculation, and so on are concerned, much phoqthe same as those used for ordinary telegraphs. In towns where ^r^^a very large number of wires radiate from one centre or exchange,as it is called, where thick wires are unsightly, and where it isoften necessary to provide for long spans, a comparatively tliin wireof strong material is employed. For this reason various bronzes,such as silicon, aluminium, &c., have come to be extensively usedfor making wires for telephone lines. They are made from aboutthe twentieth to the thirtieth of an inch in diameter, and are foundto wear well in the somewhat mixed
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Keywords: ., bookcentury1900, bookdecade1900, bookidencyclopaedi, bookyear1902
