. Journal of electricity. telegraph instruments, the variation of thetrolley current sets up a current in the telegraph cir-cuit, just as in the case of the ordinary transformer. The simple relations of primary and secondaryvoltages and currents described above do not hold,however, since in this case there is no appreciable ef-fect on the trolley circuit () whether thetelegraph circuit is opened or closed. This resultsfrom the very small degree of coupling of the two cir-cuits. The frequency, or rate of variation, of the inducedcurrent in the telegraph circuit is the same as that in
. Journal of electricity. telegraph instruments, the variation of thetrolley current sets up a current in the telegraph cir-cuit, just as in the case of the ordinary transformer. The simple relations of primary and secondaryvoltages and currents described above do not hold,however, since in this case there is no appreciable ef-fect on the trolley circuit () whether thetelegraph circuit is opened or closed. This resultsfrom the very small degree of coupling of the two cir-cuits. The frequency, or rate of variation, of the inducedcurrent in the telegraph circuit is the same as that inthe trolley circuit, just as an ordinary transformer doesnot alter the frequency. When the induced current inthe telegraph circuit approaches the telegraph signal-ling currents in frequency and amount, the interfer-ence becomes serious. *A third cause of disturbance is that part of the trolley cur-rent may follow the telegraph wire as a return path instead ofthe rails on earth. 176 JOURNAL OF ELECTRICITY [Vol. 40—No. 4. THE MAKING OF AN AEROPLANE (The giant forests of Oregon must supply the great bulk of spruce necessary in the manufacture of aero-planes. This wood, which is used for the entire framework of the machine, is found only in certainfavored localities, of which Oregon furnishes the major supply. The converting of the raw product intomachine parts is, therefore, the typically Western end of the manufacture, although some factories whichturn out the machines complete are also located on this coast. The story of the part electricity playsin this manufacture is here interestingly told.—The Editor.) THE MAKING OF AN AEROPLANE HE war has brought many industries into being on the Pacific Coast, of which perhaps none is more interesting than that of the making of aeroplanes. The O. K. Jeffery Airplane Factory of Portland, Oregon, is one of these new enter-prises built to meet a war need. As with so many of the by-products of war, however, it has its application to peace
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Keywords: ., bookcentury1900, bookdecade1910, bookidjo, booksubjectelectricity
