Patent US 5,014,138

The invention provides for deciding whether a recording dot is to be printed for the reproduction of scan dots. The scan dots being considered are complied in an input switching network into groups, for which an arithmetic processor determines the tonal value sum. The arithmetic processor emits a signal, if the tonal value sum exceeds a certain figure. The recording dot to be printed is determined by the presence of the signal in an output switching network. This process is performed successively for increasingly larger areas of the original, that is, for increasingly larger quantities of scan dots.