GB1069763A - Apparatus for generating electrical signals representative of characters to be displayed or printed - Google Patents

Abstract

1,069,763. Alpha-numeric television system. A. B. DICK CO. Aug. 7, 1964, No. 32311/64. Heading H4F. The invention relates to a system, Fig. 3, in which video signals representative of selected characters are generated by a character generator 38, e.g. a monoscope tube as illustrated or an equivalent arrangement involving a cathoderay tube flying-spot scanner, and are applied to a reproducing system 44, e.g. a cathode-ray display tube as illustrated or a printing system. The characters are selected by indexing circuits 32 controlled by a data pulse' source 30 and are scanned by signals from a small raster generator 38. The reproducing system is scanned in a similar manner and the characters are positioned under the control of display format circuits 46. The sequence of operation from producing the word THE are illustrated in Fig. 1 (not shown). In accordance with the invention from a first aspect, position indicating lines 20, 22, 24, Fig. 2, are positioned a predetermined distance below the characters in the character generator and serve to produce signals by which the reproduced characters are correctly positioned vertically despite the inevitable errors which occur in the positioning of the raster in the character generator. To. this end, the horizontal (slow) scan of the reproducer is controller by the horizontal output of small raster generator 38 but the vertical (fast) scan is controlled by a separate generator 54 which is triggered by signals. due to lines 20, 22, 24. The video signal from the character generator is shown in Fig. 4 (not shown), where the normal video component (64) in each vertical line which represents the character is preceded by a signal (64A) due to the position indicating line. These signals are separated from'the video component by a gate 53; Fig. 2, which is controlled by a pulse 66 from a multivibrator 52 triggered by a pulse 68 obtained by differentiating in circuit 51 the vertical scan signal from generator 38, and is applied to trigger generator 54. Since signals (64A) always occur at a fixed time before the video components (64), the vertical scans in the reproducer are timed to align the characters accurately vertically. According to the invention from another aspect, Fig. 5, each character has its own individual position line which apart from indicating the correct vertical position as in Fig. 2 also indicates by its length and horizontal position the horizontal space and position to be assumed by the reproduced character. For this purpose the arrangement of Fig. 3 is modified as shown in Fig. 6 (not shown) so that the output of gate 53 controls both a vertical and a horizontal scanning generator. The vertical scan generator is controlled so as to position the character vertically as described above with reference to Fig. 3, whilst the horizontal scan generator is caused to operate only whilst the position indicating signals are being generated.