Patent GB-1187701-A (GB)
Title: Display Apparatus
IPC: G09G1/10
Filed: 1968-01-16
Abstract: 1,187,701. Cathode-ray tube displays. BUNKEB-BAMO CORP. 16 Jan., 1968 [15 Feb., 1967], No. 2339/68. Heading H4T. In a symbol generating system for a cathoderay tube display in which the symbols are produced by deflecting the beam in a continuous visible trace, data signals representative of the X, Y co-ordinates of a sequence of point positions in a 6 x 6 dot matrix on the tube screen which define the symbols are written into a memory and subsequently readout, point-bypoint, during successive time periods of a cycle comprised of a plurality of such time periods. Signals representative of the required "on-off" condition of the tube beam are also written into the memory and read out during certain time periods. The read-out X, Y co-ordinate signals are in digital form and are converted to an analogue form comprised of rectangular pulses. These are supplied to wave shapers which modify the pulse rise time and provide three selectable outputs of, respectively, increasing rise times, (Fig. 5a). The selected outputs are then supplied to respective X, Y, beam deflection amplifiers termed minor deflection amplifier controlling the production of the symbols and the outputs of these amplifiers are supplied to the tube deflection plates via further respective deflection amplifiers termed major deflection amplifiers controlling, the initial positioning of the beam, e.g. for symbol and word spacing. The signals controlling the "on-off" condition of the beam are utilized to produce un-blanking pulses for a beam control electrode (Z-axis) so that the beam is blanked during undesired traces e.g. the run to the starting point, and to prevent varying the intensity of the display when it is necessary in the production of a symbol to trace some lines more than once. Additionally, to maintain uniform intensity of the display, the X, Y symbol deflection waveforms are differentiated and utilized to control the beam intensity as a function of beam tracing velocity. The symbols may be traced in two different size formats by modifying the gains of the minor deflection amplifiers when the input control data to the system specifies a change of format. Fig. 1 shows the overall system and is selfexplanatory in depicting the operation after the X, Y and Z control signals have been derived from the symbol signal source 28. The latter comprises and adress section (Fig. 3, not Shown) and a memory section comprising a matrix of magnetic cores (Fig. 4, not shown). In operation 6 bit digital signals representative of 64 different symbols and derived from the data source 38 are, after de-coding utilized to energize individual ones of 64 symbol write lines uniquely threaded through the cores of the memory such so that, when the latter are "read" row-by-row digital signals appertaining simultaneously to the requirements of the X, Y and Z axes for each point in the 6 x 6 matrix of a particular symbol are derived sequentially during successive time periods in the cycle. Other columns of cores are provided in the memory to derive signals indicative of "end-of-symbol"; signals controlling the spacing of individual symbols (i.e. justifying) ; signals which perform a recycle function e.g. when a complex symbol requires more than one reading cycle a portion of it is produced during successive cycles; signals responsive to input data for controlling the symbol size, and signals specifying which of the three selectable pulse rise-time outputs of the waveshapers (referred to above) are required. The use of the different pulse rise-times is illustrated in tracing of the symbol "B", Fig. 2a, by the application of the X, Y and Z signals which appertain to the dot matrix points shown in Fig. 2b during successive time periods t 0  . . . t 11  the X and Y signals being the outputs of the digital-to-analogue converters 30, 32 (Fig. 1) which are supplied to the wave shapers 34, 36. Initially, at time to the beam is assumed to be at point 50 (X=2, Y=2) in the 6 x 6 dot matrix. At time t 1  the beam is directed towards point 52 (X=2, Y=6) by an output from the wave shaper 36 which has a rise time such that two time periods of the cycle are required for the transition between points 50 and 52, thus, at the end of period t 1 , the beam will have reached point 54 and at the end of period t 2 , will have reached point 52. At t 3  the beam is deflected towards point 56 (X=5, Y=6) but at the end of t 3  when the beam has reached point 58 the beam is directed, at period t 4 , towards point 60 (X= 5, Y=4) so that the beam veers downwardly and at the end of t 4  will be approximately at point 62. Thereafter the beam is directed towards point 54 (X=2, Y=4) at time period t 5  the direction being maintained for two time periods so that point 54 is reached at the end of time period t 6 . To complete the lower half of the symbol the beam is directed toward point 60 (X=5, Y=4) at the start of period t 7  the beam being blanked (Z signal "OFF" see Fig. 2b) to avoid retraversing the central portion of the "B" and at the end of period t 7  the beam is unblanked (Z signal "ON") and directed towards point 66 (X=5, Y=2) during period t 8 . At the end of t 8  however the beam is directed towards point 50 (X= 2, Y= 2) which is reached at the end of time period t 10 . Thus, by selecting pulse rise times from the shapers 34, 36 such that the transition time of the beam between any two selected points corresponds to two (or more) of the time periods in the cycle and by changing the destination point during the beam traversal curved lines may be drawn. When the symbol requires long curves, pulse rise times corresponding to transition times of one or more time periods are selected. For rapid movement of the beam between any two points a pulse rise time corresponding to a transition time of one time period is utilized. The recycling operation may also be utilized to permit a group of symbols to be displayed in sequence automatically.