Radio, miracle of the 20th century ... a story of human achievement that stands unrivalled in the history of humanity, together with a colorful portrayal, giving a broad, general view of the whole subject of wireless telegraph and telephone and its marvelous development (1922)
Drinker, Frederick E. [from old catalog], Lewis, James G., [from old catalog] joint author · [Philadelphia, Printed by National publishing co.] · leaf 307
Fig. 30. … electrons strike the minute particles of the air or gas andare soon stopped. The facts stated above are applied in the vacuum tube.The air is pumped from the tube (hence the name vac-uum) so that the passage of the electrons will not bestopped. The filament, marked F in figure 30-A, is heatedso…
Radio
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