GB371329A - Improvements in and relating to methods of recording and/or reproducing sounds - Google Patents

Abstract

371,329. Sound records; reproducing apparatus. BRITISH THOMSONHOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Compagnie Francaise pour l'Exploitation des ProcÚdÚs Thomson-Houston ; 173, Boulevard Haussmann, Paris.) Oct. 17, 1930, No. 31208. Convention date, Oct. 17, 1929. Void [Published under Sect. 91 of the Acts]. [Class 40 (ii).] Relates to the use of electromagnetic or electrostatic processes for reproducing sound from records which have been obtained by optical methods. The necessary variations in the magnetic and dielectric properties of the record may be obtained by employing as lightsensitive material an agent, such as ferric bromide or ferric chloride. The records may be carried on a support of paper, Cellophane, cellulose, &c. Another suitable form of record is obtained on a paper or other support by a printing process from a photographic master record, the printers' ink being provided with magnetic material in suspension. Alternatively, a negative record, produced with bichromated gelatine which is treated so that the blackened parts of the film project above the unexposed parts, is passed with a paper film between a pair of rollers. Ink containing magnetic particles in suspension is caused to penetrate between the two films so as to produce a positive copy on the paper. Instead of printing as above, metallic deposits may be obtained by chemical precipitation with the aid of suitable developers. Fig. 1 shows electromagnetic apparatus for reproducing sound from a ribbon R which is caused to pass between the knife-bladed ends of the polepieces N, S of an electromagnet M. The ribbon R is guided by nonmagnetic elements A, C, D. If desired, the principal poles N, S of the electromagnet may be arranged between two pairs of auxiliary poles N1, S1 and N2, S2, as shown in Fig. 2. For electrostatic reproduction, two wires F<1>, F<2>, Fig. 4, are sunk into the bodies of two insulating guiding elements A for the ribbon R, the wires forming a condenser which is varied in capacity by the passage of the ribbon. The surfaces of the poles N, S or of the wires F<1>, F<2> may be of concave form as shown in Fig. 5.