A B C of television; or, Seeing by radio; a complete and comprehensive treatise dealing with the theory, construction and operation of telephotographic and television transmitters and receivers; written especially for home experimenters, radio fans and students.. (1929)

Page scan 000176 from A B C of television; or, Seeing by radio; a complete and comprehensive treatise dealing with the theory, construction and operation of telephotographic and television transmitters and receivers; written especially for home experimenters, radio fans and students..

Record Details:

Title:
A B C of television; or, Seeing by radio; a complete and comprehensive treatise dealing with the theory, construction and operation of telephotographic and television transmitters and receivers; written especially for home experimenters, radio fans and students..
Date:
1929
Publisher:
New York, The Norman W, Henley publishing co.
Volume:
A B C of television; or, Seeing by radio; a complete and comprehensive treatise dealing with the theory, construction and operation of telephotographic and television transmitters and receivers; written especially for home experimenters, radio fans and students..
Leaf #:
000176
Language:
English
Contributor:
Prelinger Library
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 20, 2022
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SELENIUM CELLS 145 ance. An exceptionally clear analysis of this effect is shown graphically in Fig. 46. Here it will be seen that the current increases rapidly when the cell is illuminated, but that the cur rent value, instead of returning at once to normal, only par tially rises owing to the interference of the inertia effect. This time factor or variable may extend anywhere from a small fraction of a second to several minutes depending upon the particular characteristics of the cell and the intensity of the light to which it may be exposed. Naturally, in phototele- FIG. 47.—Korn method of connecting a selenium cell in one arm of a wheat- stone bridge to overcome the lag of the cell. graphic work this lag is not as important as it is in television where extremely rapid current changes are necessary to pro duce illusions. However, it is possible to design selenium cells so that they will act with sufficient rapidity for the instan taneous transmission of crude pictures. Prof. Korn has devised a most ingenious way of mitigating this lag effect by making the cell form the resistance of one arm of a Wheatstone bridge, the other arms being adjusted to a resistance value somewhere in the neighborhood of the resistance of the cell. The diagram of connections for this arrangement is illustrated in Fig. 47. The inertia effect can be reduced still further by enclosing the cell in exhausted glass tubes. This not only reduces the lag