DF1UD EN
FAX
Homemade > FAX
FAX (Faksimile)
To the history of FAX (facsimile)
The facsimile-Telegrafie ranks among the oldest techniques. Already before the practical application of the Morsetelegrafie in Europe (1848) by Alexander Bain (1843) a suggestion for a copying devices one made, which should transfer drawings, documents and such a thing. A practical practical application took place only many later. The largest problem was the scanning and recording of the collecting main. A stormy development time began. Attempts with chemically prepared paper, metal foil paper or ink write system were - well-known like also the use of photosensitive paper around the turn of the century already.
The scanning of the collecting main by a light beam as well as its transformation into an amplitude oscillation of the current was the prerequisite of a picture transmission in the today's sense.
Particularly the companies RCA, BeIl, Western union, Alden (the USA) as well as Philips (Holland) and Muirhead (England) contributed crucially to the fact that the picture transmission takes today the workstation, which is entitled to her. In Japan for the 20's picture transmission are developed, which led today to one of the largest remote copying networks.
In Germany particularly the companies Siemens and Halske, Telefunken and the company Dr. Ing. Rudolf bright (1926 first suggestion of a radio-photogram receiver) advanced the developments.
Mode of operation
The collecting main which can be transmitted is divided transmit-moderately into individual lines and scanned line for line, similarly as during the transfer of a television picture. The brightness values of the pixels of a line are converted by means of an optical scanning a direction into electrical values. If it concerns with the collecting main a black and white picture, then one receives a voltage step (binary signal) after the transformation into an electrical signal, whose specific status are to be assigned to the black or white of the collecting main. During the scanning of collecting mains with grey tones - also half-tone pictures mentioned - the transformation is into electrical values a similar process. According to the grey gradations between black and white a linear voltage develops. The in such a way won picture signals are supplied to a modulator, in order to be able to transfer it with a subcarrier (SubCarrier). On the receipt page the picture signals in a demodulator, transmitted with a subcarrier, are demodulated. The in such a way won DC voltage values (voltage step or similar voltage) control for their part the write mechanism of the receiver.
The quality of the transmission method becomes essentially of the number of pixels for each line, the number of the lines/mm, which determines amount of that line/min and possibly the number of transferred and reproducible grey tones.
To the own homemade devices of the Fax-Techniques:
[ CLICK ==> ENLARGE ]
Top