Patent GB-1379663-A (GB)
Title: Audio-visual system
IPC: G09B7/08
Filed: 1972-02-11
Abstract: 1379663 Audio visual system MINNESOTA MINING & MFG CO 11 Feb 1972 [12 Feb 1971] 6548/72 Headings G5G and G5R An audio-visual system for teaching purposes comprises a disc record member 10 having an outer audio portion 12, formed with a plurality of record sound tracks each commencing at the record periphery, which is rotatable about an inner portion 14 provided with a similar and associated plurality of transparencies 22 and a record playing and transparency projector member including a turntable for rotating the outer portion of the record for playback by a pick-up arm and speaker 40, the turntable being mounted on a platform which is reciprocatable in x and y directions to bring the transparencies into a projection beam directed to a display screen 34. Each transparency 22 includes an area 24 for displaying information associated with one of the sound tracks and an area 25 for displaying three choices which can be made by an operator in response to the displayed information by actuating a lever 42 to one of the positions 116- 118. Associated with each choice are indicia 27 including a direction 29 and number 28 in binary form which are read by photo-electric means to control movement of the turntable and platform to the next audio-visual presentation which is programmed to follow as a result of the selection. The record 10 is located on turntable 48 and platform 50 by pins 52-55 which engage holes 30, 31 to register the inner and outer parts of the record. The turntable and with it the outer audio portion of the record is rotated when turntable drive-wheel 58 is moved by drive solenoid 62 into engagement with capstan 60 and the turntable rim. Tone arm 65 is raised when a sub-audible tone at the end of each sound track causes de-energization of a tone arm solenoid 72 and on raising the arm a detecting element 82 is brought into operation by an arm 84 and detects a start position member 88 which rides on the turntable seated in‹ grooves in its fluted outer rim 90. On detecting the member the circuit to the drive solenoid is opened and a brake 64 is operated to accurately stop the turntable relative to the detector 82 at the position at which it started rotating. The projector apparatus comprises lamp 93 and a lens 94 for focusing the transparency being projected on screen 34 via mirror 96. During play-back of the information only the part 24 of the transparency is projected; however, when marker 88 is detected and the record is stopped a pulse is delivered to a solenoid which opens a shutter in the projection path to present the choices 25 to the operator. As lever 42 is moved by the operator and then depressed into one of the slots 116-118 to exercise his choice a bank of four photo-cells is moved to a position to read the indicia 27 associated with the choice. The first cell acts via a S.C.R. and relay to control the direction of stepping of the turntable and platform for the next audio visual presentation and the other three photo-cells gate three S.C.R.s to "on" or "off" conditions in dependence on the number of required steps in binary form. With at least one of the three S.C.R.s gated on, a solenoid 52 is actuated to control the stepping of the turntable. This is carried out by a drive tyre which engages and drives the fluted outer rim 90 in the required direction whilst an arm 158 holds marker 88 in position. As each flute passes the marker a pulse is generated which is supplied to a counter which presents the count in binary form and when this reaches that set in the three S.C.R.s the turntable stepping process is halted. The support platform 220 for the turntable 48 &c. is movable on rails and rollers 230 in an "x" direction on carriage plate 222 which in turn is movable on rails and rollers 234 in a "y" direction. The movement is accomplished by "x" and "y" stepping means 236, 238, each containing a pair of serrated arms which cooperate with pins depending from the platform 220 and carriage plate 222. The serrated arms are eccentrically mounted on a gear-wheel and one or other co-operates with its pin, depending on the direction of rotation of the motor driving the wheel, to move the platform or plate towards or away from the motor a distance. equal to that between transparencies during each revolution of the motor. The motors are controlled by the pulses generated by the marker as the turntable is stepped, by the direction information and also by column and row information supplied by switches 256-260 controlled by cams mounted on the movable platform and plate 220 and 222.