GB397205A - Improvements in and relating to the production of sound records - Google Patents

Abstract

397,205. Sound-records. THOMAS, R. V., 18, Rue Leon Delhomme, Paris. Feb. 25, 1932, No. 5673. Convention date, March 2, 1931. Drawings to Specification. [Class 40 (ii).] Sound is recorded optically by a beam of punctiform cross section oscillating at a frequency varying from 0 to 20000 per second, and the record so formed is adapted to be duplicated by a photo-engraving process. The record may be formed on a, travelling band or as a spiral trace on a disc. Recording may be effected by an oscillograph system. The record is first developed, then copied on to carbon paper, and this copy is transferred on to a plate of polished metal coated with a sensitive layer. The metal is engraved by means of powdered neutralized iron perchloride spread on the surface of the plate and, after the first etching, the protective layer may be reinforced by ink applied by a roller and a new etching effected. A counter-matrix with a record in relief may be obtained from this matrix for use in making discs or bands for reproduction by an ordinary sound-box or pick-up. Alternatively, by commencing with a positive of the record, the metal. plate may be formed directly with the record in relief. Reference has been directed by the Comptroller to Specifications 715/01, 4661/03, [both in Class 40, Electric telegraphs &c.], 1532/11, and 280,923, [both in Class 40 (ii), Phonographs &c.].