GB1311283A - Electronic character generating apparatus - Google Patents

Abstract

1311283 Cathode-ray tube displays MARCONI CO Ltd 25 June 1970 [12 Sept 1969] 45048/69 Heading H4T A known type of character signal generator which produces characters in dot-matrix form each " dot " comprising a rectangular area composed of a number of brightened sections of a line raster as shown in Fig. 1 in respect of the numeral " 2 " is modified to improve the legibility of the character by causing the line sections at the top and bottom of each " dot " to be shorter than the sections in the middle of the " dot ". In carrying out the invention J-K type bistable elements 1, 2 (Fig. 2) are controlled by the field and line pulses of the display CRT system to supply the pulse trains 1L1 and 2L1 and their complements to respective +NAND gates G1, G2 the outputs from which form two of the inputs to a three-input OR gate G3. The third input to the latter gate comprises rectangular pulses of " dot " period delayed in device D by one-quarter of the dot-period and the output of gate G3 is then supplied to gate G4 which also receives on input CS signals from a known character signal generator which, if fed unchanged to the display would produce rectangular " dot ". These signals, however, are only passed to the display tube via inverter INV when gate G4 receives positive signals from gate G3. The lower right hand side of Fig. 3 shows the inverted output signals of gate G4 which comprise the second and third line sections L2, L3 in the first and second fields F1, F2 and the shape of the modified " dot " produced by such signals is designated as OUT. The " dot " may be comprised of more than four line sections, e.g. six.