Abstract: The invention relates to facsimile reproduction and particularly to a method for converting a video signal obtained by scanning an original dot by dot and line by line, into a bilevel black/white signal.In the black/white recording of colored originals in which both the background and the information can be white, black, grey or colored, grey/black transitions coming from "white" and grey/white transitions coming from "black" are frequently not evaluated correctly by the dynamic threshold so that information is lost in the copy.In order that these types of transitions are also detected, it is suggested to eliminate the DC component of the video signal and to compare the video signal modified in this way with a second dynamic threshold signal derived from it.

Abstract: This invention relates to a method of boosting a discontinuous-value video signal (in pulse or stepped form). From the video signal there is derived an upper accompanying signal extending above it and a lower accompanying signal extending below it, which follow the video signal dynamically. First differential values are formed between the upper accompanying signal and the video signal and second differential values are formed between the video signal and the lower accompanying signal. To boost the discontinuous-value video signal, multiples of the first differential values are subtracted continuously from the video signal and multiples of the second differential values are added to the video signal.

Abstract: A facsimile scanning method for converting a video signal, generated by opto-electronic scanning of an original copy, into a bilevel black/white signal in facsimile reproduction.In the black/white recording of colored originals in which both the background and the information can be white, black, grey or colored, white/grey (colored)/black transitions in the original are frequently not picked up correctly so that information is lost in the copy.The invention solves this problem by recording colored, grey or black areas in the original as "white" with black boundary lines, by means of suitable electronic circuits.If the colored area in the original is a background area without information content of its own but containing a black item of information (letter), the legibility of the black letter in the area is increased in the copy by reproducing the background area as "white".

Abstract: A facsimile scanning method for converting a video signal obtained by opto-electronic scanning of an original into a two-level signal suitable for transmission.A first companion signal is first generated which lies essentially above the video signal and which follows the video signal when it rises but when the video signal declines remains at the voltage reached when the video signal was at a maximum until a difference value between the first companion signal and a reference signal is reached, which then comes close to the declining video signal until the difference value is reached, which remains at the voltage value then reached until the first companion coincides with the video signal, and which then follows the rising video signal.At the same time a second companion signal is generated which lies substantially below the video signal and which progresses accordingly. From the first and second companion signals is derived a threshold signal which follows the video signal dynamically.