. An elementary manual of radiotelegraphy and radiotelephony for students and operators . means ofdetecting tbem. To achieve this it must possess unilateral con-ductivity, in other words, it must permit the passage of electricitythrough it in one direction but not in the other, or permit it toflow in one direction under much less electromotive force than inthe other direction. A very simple but eflective form of oscillation valve wasinvented by the author in 1904, based upon researches mademany years previously, viz. in 1890, uj^>on the Edison eftect inincandescent electric lamps An ordinar
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . means ofdetecting tbem. To achieve this it must possess unilateral con-ductivity, in other words, it must permit the passage of electricitythrough it in one direction but not in the other, or permit it toflow in one direction under much less electromotive force than inthe other direction. A very simple but eflective form of oscillation valve wasinvented by the author in 1904, based upon researches mademany years previously, viz. in 1890, uj^>on the Edison eftect inincandescent electric lamps An ordinary incandescent lamp withcarbon tilament has a metal plate included in the glass bulb, ora metal cylinder, C, placed round the tilament, the said plate orcylinder being attached to an independent insulated platinumwire, T, sealed through the glass (see Fig. 18). When the carbonis rendered incandescent by electric current, the space l»etweenthe filament and the plate, occupied by highly rarefied gas,possesses a unilateral conductivity, and negative electricity will RA DIO TELEGRA PH Y. Fig. 18.—Fleming OscillationValve. pass from the incandescent filament to tlie plate, but not in the opposite direction. This eifect dependsupon the now well-known fact thatcarbon in a state of high incandescenceliberates electrons or negative ions;that is to say, point charges of negativeelectricity. These electrons, or cor-puscles,iare constituents of the chemicalatom. Hence, a carbon filament in anincandescent lamp is discharging fromits surface negative electricity, whichmay even amount to as much as anampere or even several amperes persquare centimetre. If, then, an incan-descent lamp made as described hasits filament rendered incandescent bya continuous current, and if anothercircuit is formed outside the lampconnecting the negative terminal ofthe filament with the insulated metalplate or cylinder in the bulb, and ifoscillations are set up in this circuit,negative electricity will be able
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
