The scheme is just a long camera with miles instead of inches between lens and plate. For example, the lens in Washington and its photographic plate in Boston; with this exception, that the one lens in Washington can put a negative on one, ten or one hundred photographic plates in as many different cities at the same time, and at distances limited only by the power of the broadcasting station, radio instead of light carrying the image from lens to plate.
The time for transmitting a picture depends upon the size of the picture and strength of light, say, from three to six minutes, using a filament lamp as a source.
The radio photograph receiving instruments are rather simple and inexpensive and, like a loudspeaker, can be attached to any standard amplifying audio-radio receiving set.
FILAMENT LAMP:
For the light source for radio photographs a filament lamp is employed, and in a single turn coil enclosed in a hydrogen atmosphere. This miniature filament coil is imaged on a photo negative plate, and the variation in the light is caused by putting the incoming radio signals through this lamp, perhaps after the filament has been brought to a red glow by a battery current. By adjusting the speed of the motor to the temperature change of this filament soft gradations of light and shade are obtained which probably can never be equaled by any other device, a photograph of true photographic value, entirely free of lines.
The author wishes to take this occasion to express his appreciation of the splendid assistance of the General Electric Company, under the personal supervision and hearty cooperation of Mr. L. C. Porter, who from the very first has shown his confidence in the ultimate successful conclusion of this development.
GLOW LAMP:
For the high speed radio photograms, where only blacks and whites are needed, a corona glow lamp of very high frequency has been developed. This lamp is lighted by the plate current of the last tube of the amplifier; and as the lamp can be lighted and extinguished a million times a second, it is obvious that the permissible speed is almost limitless, and a thousand words per minute is believed ultimately possible.
This lamp has been developed for the author by Professor D. McFarlan Moore, an expert in lamps incorporating this phenomena, and who some years ago, it may be remembered, produced a lamp of this type more than two hundred feet long. It is probably safe to predict that no other lamp will ever be able to compete in speed.
As photography is the quickest means of copying anything; and radio the swiftest in travel, it seemed logical that the two hitched together should constitute the most rapid means of communication possible.