Patent GB-1239661-A (GB)
IPC: G09G1/12
Filed: 1969-03-18
Abstract: 1,239,661. Cathode-ray tube displays. BEVAUGE A.G. 18 March, 1969 [18 March, 1968], No. 14306/69. Heading H4T. In an arrangement for producing symbols &c. on the screen of a cathode-ray display tube by effecting appropriate deflections of the beam under the control of appropriate deflection waveforms the latter are produced under the control of sybmol cards selected from two sets of symbol cards one set being supplied with a sequence of timing pulses and arranged to produce a corresponding sequence of independent X, Y deflection waveforms for generating " polygon" traces and the other set being supplied with the sine and cosine outputs of a generator (which also controls the production of the timing pulses) and arranged to produce deflection waveforms for generating " Lissajous" type traces. Each card is concerned with the production of a different symbol and a plurality of cards from one or both of the sets may be selected and the corresponding symbols displayed in a cyclically repeating sequence, the " polygon " and " Lissajous " traced symbols being displayed simultaneously if desired. Facilities are also provided for altering the size, position and orientation of the displayed symbols. As shown in Fig. 1, a sine wave generator 1 supplies sine and cosine outputs to the " Lissajous " cards 6 and controls a pulse generator 2 the output of which is supplied to a binary counter 3 feeding a binary-decimal decoder 4 from which a cyclic sequence of pulses is fed to the " Polygon " cards 5. The cards, which consist of plug-in units each of which is concemed with the production of a different symbol, comprise, in the case of the " Polygon " cards, two groups of potentiometers 31, 32 (Fig. 2) to inputs 1x ... and 1y . . . of which pulses from decoder 4 are supplied and from outputs 33 and 34 of which respective X, Y deflection voltages for the display tube are derived. Input voltages supplied to potentiometres 35, 36 serve to position the symbol and blanking voltages for blanking undesired portions of the trace are derived from terminal 37. In addition, an " end of symbol" " signal is obtained from output 38. An embodiment of a " Lissajous " card is shown in Fig. 4 and comprises an input 41 supplied with the cosine output and an input 42 supplied with the sine output of generator 1 the amplitudes of which may be modified by respective potentiometers 43, 44 to provide X and Y deflection voltages at outputs 45 and 46 respetively. Symbol positioning voltages may be supplied via potentiometers 47, 48 or if desired via terminals 49, 50 and decoupling resistors R. Other " Lissajous " cards for the production of a symbol consisting of two parallel straight lines of variable length and spacing and for the production of a symbol consisting of a crossshaped pattern are described with reference to Figs. 5 and 6 (not shown). In operation the voltage outputs derived from the " Polygon " cards 5 are supplied via individual ones of a multiple switch 7, controlled by a binary symbol counter 24 and a binary-todecimal decoder 25 according to a selected programme, to inverting summation circuits 8 . . . 11 (the X and Y deflection voltages to circuits 8 and 9 respectively, the blanking voltage to circuit 10 and the " end of symbol" " voltage to circuit 11) and the voltage outputs derived from the " Lissajous " cards 6 are supplied by a similarly controlled multipole switch 20 to the inverting summation circuit 11 and further summation circuits 14, 15 associated respectively with the X and Y deflection circuits of the display tube 27. Circuits 14 and 15 also receive the outputs of integrators 12, 13 fed respectively with the X and Y deflection voltages of the " Polygon " cards derived from summation circuits 8 and 9. In addition circuits 12, 13 receive shift voltages from a switch 16 (also controlled by 24, 25). The symbols to be displayed are selected by a three position two-pole switch 22a, 22b (one switch per symbol) and the appropriate deflection voltages are fed to the display tube via a two-pole change-over switch 17 which, in position I of switches 22a, 22b is conditioned by means of an OR gate 21 to pass the deflection signals to the display tube via a circuit 23 controlling the size, position and orientation of the symbols. In position II switch 17 passes the deflection signals directly to the display tube and in position III the output from the first stage of decoder 4 (which effects beam blanking via circuit 10 also receiving the blanking outputs of the cards from the switches 7, 26) is supplied to the " symbol termination " input of switch 7 and operates via circuit 11 to re-set the integrators 12, 13 and the binary counters 3 and 24.