Patent GB-543977-A (GB)
Title: Improvements in or relating to cathode ray apparatus
IPC: G09G1/18
Filed: 1940-08-12
Abstract: 543,977. Electric signalling systems. BAILLIE, G. H. (International Business Machines Corporation). Aug. 12, 1940, No. 12905. [Class 40 (i)] [ALso in Group XL] Any one of a set of characters (letters or numerals) is displayed on the screen of one or more cathode ray tubes by scanning two circular optical records carried by a rotating member and representing the varying values of the co-ordinates of a number of characters. The outputs of two photo-electric cells which receive the scanning beams are applied after amplification to the deflecting plates of a cathode ray tube and the desired character is selected by making the cathode ray ineffective except during the scanning of those parts of the records representing the character. As shown in Figs. 1 and 3, a rotating disc 10 carries two records 13x, 13y of the co-ordinates of numerals 0-9, the x co-ordinates of any one numeral being diametrically opposite the y co-ordinates, and the records being scanned by beams from sources 14x,14y. Character selection is made by selecting one of a. number of commutator discs 26 mounted on the rotating shaft 11 of disc 10. The circuit arrangement is shown in Fig. 7, two cathode ray tubes 21, 22 being employed to display tens and units denominations, and then deflector systems, which may be electro-magnetic, being controlled in common by the outputs of the amplifiers 23x, 23y. The inputs from the photo-electric cells 15x 15y and the outputs of the amplifiers are adjusted by potentiometers. The commutators are selected over contacts T. V of tens and units relays or keys, the effect of contact closure being to short-circuit the negative bias on the grid 19 of the corresponding tube during the passage of a conducting segment of the commutator under brushes 27. In a modification, a character is built-up by selecting appropriate portions of the records which are not necessarily individual to a particular character and by using a number of discs all the letters of the alphabet and the numerals may be made available. For example, the records on one disc may represent the coordinates of the assemblage of lines shown in Fig. 8a from which the letters C to G, J. L. O. Q, V, may be derived by suitable arrangement of the conducting segments on the commutators. This' modification involves disc selection in addition to commutator selection, the circuits being as shown in Fig. 12. Four discs and corresponding scanning sets and groups of commutators a .. d are provided, disc a providing the records of Fig. 8a described above. Two denominations and cathode ray tubes 17T, 17U are provided as before. Each commutator has an individual relay 46 for each denomination and each group has a common relay 48 for each denomination. Selection of commutator C and denomination T in group a is effected by closing the circuit 48t, 47t which operates individual relay 46a t to control the grid bias of tube 17T over commutator C, and common group relay 48a t which connects the outputs of the appropriate amplifiers 23Xa, 23Ya to the deflection system of the tubes. A photographic record may be made of the characters appearing on the screens of the' tubes. Specification 495,740 is referred to.