Electrographic writing system with diode switching assembly

摘要

An electrographic writing system including an electrographic writing head operatively connected to a switching system is disclosed. The electrographic writing head includes a plurality of electrically conducting styluses arranged to produce an electrostatic charge on a record medium which is normally dielectric coated paper. The styluses are supported by an insulating material, and one of the ends of each of the styluses is either substantially flush with one end of the writing head or slightly recessed. The other ends of the styluses act as part of a connecting means to the switching system. The switching system includes a plurality of diode assemblies. Each diode assembly has a sequence of diode switching circuits including a first high stored charge or slow diode, a second low stored charge or fast diode in series therewith and a capacitor. The capacitor has one end connected between the diodes and the other end to ground or a dynamic voltage. A stylus is connected to each capacitor and a transistor setup switch is operatively connected to a plurality of diode switching circuits, including one from each of the diode assemblies. Electrical drive means, i.e. a voltage source, is operatively connected to and controls the input to the diode assemblies. A positive bias and a clamping diode may be used with the transistor setup switch to prevent damage thereto and prevent the stylus from going positive under certain conditions.