Patent GB-1354091-A (GB)
Title: Teaching system and devices
IPC: G09B5/06
Filed: 1973-01-15
Abstract: 1354091 Automatic electric control C J JOANNOU 15 Jan 1973 [10 Jan 1972] 2023/73 Heading G3N [Also in Divisions G1 and G5] Teaching apparatus whereby a lecture, including voice and drawings, is recorded on magnetic tape, and subsequently reproduced, comprises a stylus 1 movable over a sheet of paper 3 in x and y directions, a cassette tape recorder 5, a microphone 8 and a loud speaker with a grill 10. As shown diagrammatically in Fig. 2 the stylus is driven by electric motors 12, 13, in x and y directions respectively, and signals indicative of the x and y co-ordinates of the stylus are derived from resistive transducers 15, 16. A solenoid 14 operates to lower the stylus by tilting its holder, whereupon a switch 17 is closed. Recording procedure is effected Fig. 3 (not shown) by the signals from 15, and 16 controlling oscillators 18, 19 whose frequencies are dependent on the transducer signals. An oscillator 20 is controlled by the switch 17 and the three oscillator inputs are fed to one input of the recorder whose other input is fed by the microphone. Reproducing is effected Fig.4 (not shown) by feeding the one output from the tape through filter 22, 23, 24. The output of filter 22 is fed to a convector 25 supplying one input of amplifier 28 whose other input is fed from the x potentiometer 15. The output of the amplifier feeds a motor 12 to control the stylus in the x direction and the potentiometer 15. Similarly the output of filter 23 controls y movement. Narrow band filter 24 controls a solenoid to move the stylus in the z direction. Switches on the stylus associated with the motors 12, 13 provide for "power assisted steering" for the recording procesure, diagrammatical representations of the switches being disclosed in Figs. 5-9 (not shown). In a modification Figs. 10-18 (not shown) two styli are provided, one for record and one for playback. As shown in Fig. 11, the x and y motors 12, 13 drive a carriage arrangement which includes a support 74 carrying 4 electrodes 64.. .. 67 which moves under a dielectric sheet 4 which carries the paper 3. In recording procedure as shown in Fig. 17 the x electrodes 65, 67 are capacitatively coupled with the stylus and act through amplifier 86 and motor 12 to equalize the amplifier input. Similarly the y electrodes 66, 68 operate, so that the electrodes are centred with respect to the stylus, and the appropriate x and y signals from potentiometers 15, 16 are fed to oscillators and thence are recorded. An alternative method of processing the signals derived from potentiometers 15, 16 is disclosed in Figs. 18 (not shown). These signals control the pulse widths of outputs from multivibrators, these outputs being differentiated and used to trigger a multi-vibrator 96, which is also triggered by a relative low frequency signal from 95. Hence after each signal from 95 the multivibrator 96 produces a train of 4 pulses. The intervals between these is related to the pulse widths at 92, 93, 94, i.e. the signals from potentiometers 15, 16, and the pulses are fed to the first track of the tape. In playback, these signals from the tape are decoded and fed to operate the x and y motors and the stylus Fig. 19 (not shown). In alternatives postulated in the specification, (a) a single track channel may be utilized for both sound and graphics, (b) use of phonograph records is envisaged.