GB1268822A - Television decoder - Google Patents

Abstract

1,268,822. Cathode-ray tube circuits. SANDERS ASSOCIATES Inc. 13 March, 1969, No. 43036/70. Divided out of 1,268,821. Heading H4T. [Also in Division G5] A "coded" display on the screen of a television receiver is "decoded" by means which includes a light-sensitive detector responsive to light from the display. The invention is described in connection with an educational system in which test questions together with a multiple set of answers, one of which is correct, are displayed on the screen of a television receiver (Fig. 1). A respective symbol 14, 16, 18, 20 is associated with each answer the symbols being "coded" by on-off flashing, at a rate which is not interpretable by the unaided eye, the rate of flashing of the symbol associated with the correct answer (symbol 16) being different from that of the other symbols. As described, symbol 16 is flashed an odd number of times (e.g. 61) the other symbols being flashed an even number of times (e.g. 60). In operation an examinee is required to select the answer deemed to be correct by positioning the light-sensitive detector of the "decoding" means in proximity to the symbol associated with such answer and if the selected answer is the correct one a steady light signal is given whilst, if incorrect, no light signal results. Fig. 2 shows the "decoding" means (all of which may be contained in an easily handled configuration, e.g. a gun) which comprises a photo-cell 24, a buffer amplifier 26, an amplifier and pulse shaper 28 and a flip-flop 30 which is initially set by switch 22 such that, when an odd number of flashes, each of which changes the state of the flip-flop, have been received, the latter is in the state in which an amplifier 32 conducts and causes lamp 34 to be lit to indicate that the correct answer has been selected. If an incorrect answer is selected the even number of flashes results in flip-flop 30 being left in its other state so that the lamp is not energized.