Facsimile system

Claim 1

In a facsimile system for electrically transmitting pictures between a transmitting station and a receiving station for reproduction at said receiving station, wherein the picture to be transmitted and reproduced is photoelectrically scanned, line-byline, to produce a scanning voltage signal whose amplitude is proportional to the respective brightness values of the scanned line of the picture, and the scanning voltage signal is transmitted to the receiving station where it is utilized to control a facsimile recorder which only records black or white brightness values, the improvement wherein a scanning voltage signal converting circuit is connected in the single path to said facsimile recorder, said signal converting circuit comprising, in combination: first circuit means responsive to the amplitude of said scanning voltage signal for producing a first direct voltage signal of an amplitude to which said recorder will not respond, whenever the amplitude of the scanning voltage is below a first predetermined value and for producing a second direct voltage signal, of a second higher amplitude to which said recorder does respond, whenever the amplitude of said scanning voltage exceeds said first predetermined value; a plurality of second circuit means each of which is responsive to said scanning voltage signal for producing a periodic pulse sequence output signal, of an amplitude to which said recorder responds, whenever the amplitude of said scanning voltage signal exceeds a further predetermined value which is less than said first predetermined value, each of said second circuit means being responsive to a different predetermined value of the amplitude of said scanning voltage signal, and each of said second circuit means producing a different periodic pulse sequence output signal with the sum of the pulse widths per unit time in each periodic pulse sequence output signal being greater as the amplitude of said scanning voltage signal to which the respective one of said second circuit means responds becomes higher; and, third circuit means responsive to the output signals from said first and second circuit means for providing an output signal corresponding to only the input signal thereto representative of the highest determined amplitude range of said scanning voltage signal, whereby the output signal from said third circuit means controls said recorder to reproduce pictures having the effect of white, black and shades of gray picture content.