GB1009029A - Improvements in character display apparatus - Google Patents

Abstract

1,009,029. Cathode-ray tube displays. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 24, 1963 [April 24, 1962], No. 16067/63. Heading H4T. In an arrangement for tracing Alpha- Numeric characters on the screen of a cathoderay tube separate signal generating units supplying beam deflection and intensity control signals are provided for each character and rendered operative selectively in response to a command signal. The signal generating units, all of which are contained in an analogue level synthesizer 18 (Fig. 1), and connected to common bus-bars 148, 149, 180 comprise, as shown at 18R (Fig. 2) in respect of the unit concerned with tracing the letter " R," transistors 60, 62, 72 appropriate, respectively, to the X-deflection, the Y-deflection and the beam intensity control of cathode-ray tube 30 together with resistors (except 190), of various values in accordance with the co-ordinate deflection requirements of the particular character, connected via isolating diodes to, in this case, the first ten outputs on cable 20 (see also Fig. 1), of a time period distributer 22 which operates in response to a "start" command over line 56 from a computer 10 to cycle through its twenty-four stages (unless the cycle is stopped before completion) and so cause the transistors 60, 62, 72 to provide the required signals for the cathode-ray tube control, the latter transistors being initially conditioned for operation when the particular character is selected by means of a potential (ground) on cable 16 derived via decoder 14 from the computer 10. The number of connections between each character signal generator and the time period distributer 22 (which produces twenty-four cyclically repeating outputs (TP1 . . . TP24) is made to be one plus the number of control signal elements required to trace the particular character the additional connection furnishing a " character completed " signal which is sent over conductor 24 to the computer 10. In the case of the signal generator unit 18R, the character " R " requires nine deflection steps TP1 . . . TP9 (see also Figs. 5 and 6) and the time period TP10 is then utilized for end of character signalling the latter operating via resistor 190 (Fig. 2) to overdrive the X-deflection system 248 (Fig. 5), thus causing the potential on line 50 to fall below a predetermined value which value then arrests the operation of the time period distributer 22. The latter then sends a signal over line 54 to condition the computer for selection of the next character, e.g. the generator 182 (Fig. 2), concerned with tracing the character " Q " (Fig. 7, not shown) If desired, the circuitry of some of the character generators may be modified so that each does double duty as, e.g. by arranging for the blanking of portions of the characters " R " and " Q " to produce the characters " P " and " O." For setting the main position of each character on the tube screen a further deflection system 42 (Fig. 1), controlled via computer 10 via a digital-to-analogue converter 46 is provided. The time period distributer 22 (Fig. 1) is described with reference to a blockcircuit diagram (Fig. 3, not shown).