. An elementary manual of radiotelegraphy and radiotelephony for students and operators . hese has a small hole in the centre. These plates are held in a frame which can be immersed ina vessel of paraffin oil. One of the plates is attached to a steelshaft which runs in ball bearings, and can be rotated by an electricmotor. The plate is fixed with its plane perpendicular to the axisof rotation. The other plate is held by adjusting screws with itssurface parallel and very near to that of the rotating plate (see DAMPED ELECTRIC OSCILLATIONS 79 Fie;. 27). Honeo there is a thin film of oil betwoeii
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . hese has a small hole in the centre. These plates are held in a frame which can be immersed ina vessel of paraffin oil. One of the plates is attached to a steelshaft which runs in ball bearings, and can be rotated by an electricmotor. The plate is fixed with its plane perpendicular to the axisof rotation. The other plate is held by adjusting screws with itssurface parallel and very near to that of the rotating plate (see DAMPED ELECTRIC OSCILLATIONS 79 Fie;. 27). Honeo there is a thin film of oil betwoeii the the upper plate revolves, this oil is fluug out, but continuallyrenewed by suction through the central hole in tlie bottom two plates are electrically insulated, and form the surfacesbetween which the dischar<,e takes place. A number of thesepairs of j)lates can bo placed in series. This discharger is veryefticient as a quenched spark discharger, and as the spark con-tinually changes its place, the plates are worn away equally andnot pitted in one ^ c c c FiQ. 27.—Section of Fleming quenched spark discharger. The above form of discharger when inserted in a condensercircuit, produces a very rapid series of strongly damped discharo-es,and these create a similar series of feebly damped dischar<Tes ortrains of oscillations in a coupled secondary circuit, these latterhaving the frequency natural to the secondary circuit. On the other hand, there is nothing to control the exact sparkor train frequency. Dischargers in which there is an extremely regular spark 8o RADIOTELEGRAPHY frequency are called miisical spark dischargers. These aregenerally constructed with one fixed electrode, and the other arevolving one with projecting pins, balls, or studs, which makegrazing contact with the fixed electrode during their revolution. Such, for instance, is the high speed musical spark dischargerof Marconi, which is described in Chapter VII. These music
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
