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 of these 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.