Wirephoto
As telegraphy is called method for remote transmission of images by transmission of electrical signals.
History and Development
The earliest method for telegraphy was developed by Arthur Korn 1901-1907. It is based on the semiconductor properties of selenium, which changes its resistance under the action of light. The light source came Nernstlampen used. A photo was exposed to a transparent film. This was drawn to a glass cylinder and line scanned it. A mirror inside the cylinder threw the light on a selenium cell. At the destination point, the electrical signals are converted back into light, to which a film was exposed on a corresponding glass cylinder. The first telegraphic image transmission method according to grain was from Munich to Nuremberg in 1904 and lasted 44 minutes. The quality of the transmitted images was initially unsuitable for practical applications. Until 1906 pass transmissions of sufficient quality and in only 10 to 15 minutes after the grain process.
In November 1907 began regular transfers between Paris, Berlin and London. On March 17, 1908, the first mugshot, transmitted in twelve minutes from Paris to London, printed in the Daily Mirror. With its help, a volatile jewel robber was caught.
1923 for the first time a picture from Rome to New York was sent across the Atlantic.
Another method for image transmission developed Édouard Belin beginning of the 20th century. This method was based on the formation of gelatin - dichromate reliefs in proportion to the incidence of light. It was first presented in 1908 and 1926 improved by Belin replaced the gelatin dichromate relief by an electric bulb. According to this method worked the famous "suitcase ", the Bélinograf, their images were transmitted over telegraph and telephone lines by the photographer.
The developed before 1938, Telegraph picture shown above worked on the following principle: To send the original image came on the role that turned while continuously shifted laterally. Accompanied by a photo cell, the level of darkness was a system of lenses ( today's term " scanning " ) and transmitted to the receiving device by phone technology.
To receive came photo paper on the role that moved with the same speed and feed rate as during scanning; a light source with optics made for a point light that has been controlled light and dark by telephone. To transfer an image took several minutes; it had to be fixed afterwards. The images almost as sharp as the originals, and quite suitable for the press and the police investigation.
Current methods
A development of this early method is facsimile, also known as a facsimile, which has been placed in 1983 by the Japanese company under the name Sakai Fax 2000 on the market.