A drive circuit for a matrix coupled thermal printing bar which permits the address of large arrays as would be used in a thermal facsimile printing system without the necessity for individually driving each element or providing isolated diodes to prevent leakage paths. The circuit utilizes the application of an intermediate voltage to the unaccessed rows or columns to limit the applied power to the unaccessed elements below that required to raise them to printing temperatures.

A matrix addressed electrochromic display includes first and second spaced apart opposed planar panels, a dielectric spacer peripherally sealing the panels to provide an interior cavity therebetween to define a display region, an electrochromic fluid filling the interior cavity, a plurality of parallel rows and columns of electrodes disposed in the mating surfaces of the first and second panels respectively and a low output impedance electrical refresh circuit coupled to electrically energize the electrodes in a repetitive matrix selection pattern to provide a selected dot matrix display.

In order to perform a multi-gradation display of high quality on a liquid crystal panel (6) by a small-scale A/D converter (1), a 4 - bit A/D converter (1) is equipped with four reference potential couples for performing the dither method using arbitrary two reference potential couples in each of two fields to display a signal at a first pixel. Likewise the remaining two reference potential couples are used for the dither method to display the signal at a second pixel adjacent thereto. In this way, the dither method is applied to adjacent pixels using different reference potential couples to generate an area gradation, so that it is possible to represent 64 gradations owing to the multiple effect of the dither method and the dot area modulation method. Moreover, it is possible to obtain a display of high quality which is free from flicker disturbance since the dither cycle is 1/30 second.

Several embodiments of an apparatus for directly driving all addressed and unaddressed resistive heating elements in a matrix of heating elements is disclosed. Since the unaddressed heating elements are directly driven, the parasitic voltages that are found across unaddressed heating elements in prior-art arrays are replaced with specified constant voltages. Additionally, the variation in total power dissipation of all the heating elements in the matrix can be reduced. When a matrix of directly driven heating elements is used in a thermal printer or thermal-ink-jet printer several advantages are realized. The directly driven unaddressed heating elements have a specified low voltage across them instead of a parasitic voltage which may have a magnitude large enough to cause the printhead to misfire. Additionally, the reduction in the variation of the total power dissipation reduces the variation in the printhead temperature which reduces the variation in the printed dot size.

For the display of a phenomenon or a small number of phenomena by means of an oscilloscope comprising a liquid crystal display screen, a simple matrix excitation circuit is described wherein a time-division multiplex excitation with a great number of lines and a good contrast appears possible if for each column only one or a few picture elements must be set to the ON-state, costly provisions such as voltage and temperature stabilization being required.