Abstract: An electrostatic matrix printer has a movable print head (1) in which a row of selectively energizable needles (2) is fixed for printing dots on a surface to be printed by selective energization of the needles in response to binary coded electrical signals having a number of bits, equal or less than the number of needles in the row. The binary signals, as well as determining the state of a group of consecutive needles in the row, to print different character columns, also include at least one further bit which determines the position of the said selected group of needles in the row, enabling characters of different height and vertical position to be printed.

Abstract: A portable electro-mechanical printer has a platen (1) over which electro-sensitive paper is advanced, relative to a print head (6) having a few row of selectively energizable needles (8) which is movable by an electric motor transmission (18,19,21,24) parallel to the platen in a scanning direction transverse the row of needles. A timing disc (25) is driven by the drive transmission, the disc being subdivided into sectors and cooperating with two relatively displaced photocells (26,27) which produce two periodic signals upon rotation of the disc, these signals being utilized to provide clock pulses controlling successive energizations of the print head needles as the latter is scanned across the paper.