Foreword
The rapid development of apparatus for the transmission of photographs by wire and by radio may now be confidently expected, because the public is ready for it. At this very moment it is going through the same empirical process by which motion pictures arrived, and out of which finally the long film strip was born.
In the motion picture development there appeared the spiral picture disc; the picture “thumb book”; picture cards radially mounted on drums and bands; and the picture film continuously moved and intermittently illuminated.
But finally the development resolved itself into a single, long, transparent picture film, intermittently moved in the exposure aperture of the projecting machine; and upon this has been built one of the large industries of the world.
Doubtless this will be the history of the development of electrically transmitted photographs, and of radio vision, for many schemes have already been tried and more may yet be seen before the final, practical form shall have been evolved, and this new aid to business and to entertainment shall have taken its place in human affairs.
The transmission of a photograph electrically, a portrait, for example, is not so much a matter of mechanism, once the tools are perfected and their operation understood; it is more a matter of blending of line and tone, just exactly as it is with the artist. The great portrait photographer uses the same tools the amateur uses, but an acquired technique of high order enables him to produce a superior portrait,free of chalky contrasts, and soft in tone and blending. Just so in radio photography, it is a matter of simple mechanism, and an acquired skill in its use.
The author expects to see, very soon, the radio amateurs using flash-light lamps and electric pens where they now use headphones; and halftones or potassium cells where they now use microphones, for the radio problem between the two is practically the same—if anything rather more simple with light than with sound. And new means for modulating electric current by changing light values may be expected when the American boy starts to play with this new toy.
There has been a veritable army of engineers engaged in the development of radio as a service to the ear, while relatively few engineers have been developing radio as a service to the eye.
It is believed that the distant electric modulation of light for many purposes will soon become a common phenomena and eventually of inestimable service in science, in engineering, in industry, and in the home.
Nor will this service be confined to radio. Present metallic channels now employed for other purposes,i. e., high tension power lines, railroad rails, city lighting wires, and water pipes, can be made a new source of revenue, and at a ridiculously insignificant cost.
Radio is none the less valuable by reason of its application as such a rider on the present metallic grids of every city, and of interurban connections. There are many channels where only space radio can be employed, but the neglect of the application of high frequency currents to metallic channels which lead into every place of business, and into every home, is unnecessary waste.
The author confidently believes the application ofthese several ideas to the control of light at distant points is the next great advance in electricity, and to hasten such development the information in the following pages is set down to assist the research worker and the application engineer. The mechanisms and circuits herein disclosed may be accepted with assurance.
With a radio photographic technique, the result of ten years of concentration on this subject, it may be asserted with confidence that the requirement of a particular application rather than a particular machine is the governing factor in each case; for with full working knowledge of the art, and the special application requirements known, the design of the machine best adapted to that service is a simple matter.