Abstract

An electronic half-tone generating circuit for enabling a black and white facsimile transmission system to accurately and efficiently transmit and reproduce images including shades of grey as well as black and white and including an integrator responsive to a first data signal and operative to integrate the difference between an input analog signal and a first reference potential to develop a first integral signal commensurate therewith, and responsive to a second data signal and operative to integrate the difference between the input analog signal and a second reference signal to develop a second integral signal commensurate therewith, a comparator responsive to the first and second integral signals and operative to develop a comparison signal when the first and second integral signals exceed a predetermined threshold value, and a signal generator responsive to the comparison signal and operative to develop the first data signal upon each odd numbered occurrence of the comparison signal and to develop the second data signal upon each even numbered occurrence of the comparison signal. The data signals are comprised of a series of data bits each of which identifies the data state of a discrete elemental area of the scanned information. Also disclosed are a screened version in which mezzo data is converted to a particular format for transmission, and a hybrid version in which mezzo system elements are used alternately with screened system elements to produce a reproduction having optimum picture quality.