The successful study of the problem of the transmission of light effects
electrically (vision, pictures, light signals, etc.) might well begin
with the division of the subject into its elements and sub-elements.
The major division is, naturally, into (_a_) the sending station
apparatus; and (_b_) the receiving station apparatus. A great variety of
devices have been invented for analysis of the picture at the sending
station, and the translation of the light values (which make up the
picture) into electrical modulation; and likewise a variety of methods
for receiving these electrical signals at a distant place (or places)
and there changing the electrical modulations back into light values
with which the picture is built up.