Patent GB-1318051-A (GB)
Title: Apparatus and method for use in playing games on a cathode ray tube
IPC: G09B19/22
Filed: 1970-05-22
Abstract: 1318051 Indoor games SANDERS ASSOCIATES Inc 22 May 1970 [27 May 1969] 25007/70 Heading A6H [Also in Divisions H3 and H4]  Symbols representing objects such as bats, balls, hockey sticks &c: are displayed on the screen of a cathode-ray tube, which may be a conventional television receiver, by employing appropriate, locally generated, video type signals to intensity modulate the tube beam as it is scanned in normal line raster fashion and by means of manual control devices which vary the positions of the -individual symbols a variety of simulated games may be played by one or more participants. The symbols referred to as "spots", may have various shapes such as shown in Fig. 1 where the rectangles 20 represent "paddles" (table tennis bats) and the circle 20 represents a ball or they may take various other shapes some of which are shown in Fig. 6. "Solid" or "hollow" spots may be produced.  The video type signals producing the "spots" are generated under the control of, for each spot, a pair of slicers 29, 36 (Figs. 5 and 8) comprising back-to-back germanium diodes 47-50 which produce "slices" Wv, WH (Fig. 3) of vertical and horizontal frequency 6 volt sawtooth waveform 37 and 35 (Fig. 5) at instants TV, TH determined by the magnitude of manually adjustable voltages Tv 1  and T H1 . Instead of germanium, silicon diodes may be employed (Fig. 20, not shown). Coincidence of the "slices" is then detected by gate means 40, which is provided with an adjustable threshold, to enable size and shape to be varied, and the output of the gate 40 is then supplied via OR gate and pulse shaper 46 to a summer modulator 28 (Fig. 4 not shown) in which it is combined with vertical and horizontal syncle signals and then employed to modulate a RF carrier oscillator to provide a signal for connection to the aerial terminal of a conventional television receiver. The sawtooth waveform 37, 35 may be synchronised with the vertical and horizontal scan frequencies of the receiver by means of synch pulses derived respectively by means of a photo sensor and a pick-up coil positioned at the bottom centre of the receiver tube screen. Alternatively they may be synchronised by signals derived from the synch separator or from the deflection yoke of the receiver (Figs. 18B and 18C neither shown) and instead of modulating a carrier oscillator the output of the pulse shaper 46 may be fed via switch means directly to the video circuit of the receiver (Figs. 18A, B and C, none shown). The switch means may also allow the display of normally broadcast or closed circuit programmes or of video signals derived from a tape or slide projector when such relate to symbols, background displays &c. with which the "spots" can cooperate when playing certain games.  In general, each player has control of two potentiometers 56, 57 (Fig. 9A), e.g. operated by knobs 16 1 , 17 1 , or 16 2 , 17 2  (Fig. 1) but preferably operated by a joystick control 58 (Fig. 9B) and providing the positioning voltages eH and ev for position controlof the associated spot. This gives direct control of the spot which returns to the screen centre when the joystick is returned to its central position. For some games, however, a "spongier" motion is preferable and this is produced by the inclusion of integrator 59, 60 as shown in Fig. 9C. With this latter arrangement the spot moves when the joystick is off-set from its central position with a speed determined by the offset distances and in a direction determined by the angular position of the joystick, the spot remaining wherever it happens to be when the joy-stick is returned to its central position. When games employing a ball are to be played the ball "spot" is generated by circuitry similar to that already described and to produce movement of the ball spot, other than that resulting from a "hit", e.g. by a bat, a circuit of the kind shown in Fig. 10A is employed. This circuit provides a horizontal positioning voltage e H  (a similar circuit being employed to produce ev) of polarity and magnitude determined, respectively by the state of flip-flop 61 and the settings of potentiometers 65, 66, the voltage e H  being derived from point 64 if rapid motion is required or via RC circuit 71, 72 which causes the motion to be fast initially, giving the impression of being "kicked" or "hit" and then to slow down gradually and stop. This circuit is employed inter alia in table tennis, hockey &c. to serve the "ball" from an off screen position at one side towards an off screen position at the opposite side unlessintercepted by a "bat" or other obstacle such as a billiard table cushion or a boundary, when coincidence circuitry is effective to reverse the direction of motion by reversing the state of the flip-flop 61. Figs. 19A and 12B show the general use of this circuit in playing table tennis where coincidence of a bat and the ball (recognised by coincidence of the eH and ev voltages of each) causes flip-flop 122 to reverse the direction of motion of the ball which is automatically effected by slow flip-flop 120 (i.e. to "serve") in the event that a "hit" between a bat and the ball does not occur. Fig. 11A, shows an arrangement generally applicable in the playing of games utilizing a "hit" spot, e.g. a ball and two "hitting" spots, e.g. bats, hockey sticks &c. In operation, a "hit" between either "hitting" spots and the "hit" spot results in coincidence detector 83 or 84 triggering one-shot multivibrator 81 or 82 which cause horizontal or vertical gated differentiations 85 or 86 to pass the H and V control voltages of the "hitting" spot via bilateral gates 92 or 93 to "stretching" capacitors 94, or 95 which then provide via the control voltages eH, ev for the hit spot via integrator 90 and 91. The amplitudes of the pulses provided by the gated differentiators 85, 86 are proportional to the horizontal and vertical components of the velocity of the "hitting" spot at the instant of a "hit" and by integrating such pulses the "hit" spot is caused to move in the direction in which it was "hit" over a distance and at a speed proportional to how "hard" it was "hit". The "stretching" capacitor 94, 95 are included to increase the time for which the pulses are integrated in order to prevent too fast a spot movement which the relative short width of the gating pulses from the one shot multivibrators 81, 82 would give rise to. An additional feature is the provision of a "bounce" facility which operates when the "hit" spot reaches a predetermined limiting position in any direction, e.g. a wall or the cushion on a billiard table. As shown (Fig. 11A) the outputs of the integrators 90, 91 are supplied to wall sensors 109, 110 in which horizontal and vertical control voltages representative of such position are set up the sensors operating when the "hit" spot control voltages are equal to the set-up voltages to open normally closed switches 105 or 192 and close normally open switches 104 or 193 so that the input to the integrators is now supplied via inverting amplifiers 108. The sign of the control voltage is now reversed so that the "hit" spot "bounces" off the boundary at an angle equal to the angle of incidence as shown in Fig. 11B. Circuit details of the elements of Fig. 11A are described with reference to Figs. 11C and 11D (neither shown). The Specification includes description of the playing of other games e.g. "base-ball" and "bowling" a feature of the latter game being to control the size of the "bowl" i.e. to reduce it, as it "moves away" to give a three dimensional perspective effect. Word and letter games may also be played and where a colour television receiver is employed suitable chroma control voltages may be generated and employed to cause desired portions of the display to be reproduced in a distinctive colour, e.g. blue ice in ice-hockey. Some or all of the circuitry may be built into conventional television receivers or a separate construction embodying its own cathode-ray tube may be employed (Fig. 19, not shown).