Vision by radio, radio photographs, radio photograms

by C. Francis Jenkins

Radio Corporation Machine

The accompanying “photoradiogram” is a development by the Radio Corporation of America, and was transmitted from London to New York on November 30, 1924.

“The transparent picture film is placed on a glass cylinder. An incandescent lamp inside the cylinder is focused in a minute beam onto the film as the cylinder rotates, and this transfers the light values of the picture into electrical impulses, in a General Electric Company photo-electric cell.

“The receiving cylinder has white paper placed thereon, and the incoming dots-and-dashes, amplified in passing through a bank of vacuum tubes, are recorded in ink on this paper with a special vibrating fountain pen, drawn down by magnet coils to record the picture much in the style of an artistic stippled engraving.” The cylinders of both the sending and the receiving machines are “rotated back and forth, the electric camera itself advancing down the length of the picture one notch at a time.”

“The necessary synchronism of the two machines is maintained by the use of special driving motors, and a special controlling mechanism based on the constant pitch of a tuning fork.” (See Radio News, February, 1925.)

By courtesy of “The World,” New York.
A RADIO CODED PHOTOGRAPH.
How the picture looked after being sent from Rome by radio and decoded on Professor Korn’s machine.

The above is an example of one of the rather odd methods of “sending pictures by radio.” The picture to be sent is divided into many small squares with varying values of dark in the squares. Seventeen different grades of light in these squares are translated into seventeen letters printed on a tape.

This coded picture is transmitted to a distant place and there decoded into dots of sizes corresponding to the seventeen values, and each dot placed in its corresponding square on a white paper. The collection of large dots builds up the dark areas; a similar collection of smaller dots makes up the halftones; and still other collections of very minute dots make up the light areas. (From the New York World.)