GB675435A - Improvements in or relating to magnetic sound recording methods - Google Patents

Abstract

675,435. Magnetic sound recording apparatus. ROHLING, H., (trading as ROHLING PHYSIKALISCHES LABORATORIUM, H.). July 3, 1950. [July 4, 1949] No. 16585/50. Class 40 (ii). In a magnetic sound recording apparatus the means producing the speech frequency magnetic field is spaced away from the core or head so that the speech frequency field is induced in the part of the core adjacent to the record carrier, and in the part of the carrier adjacent to the core, means being also provided for a bias magnetisation field. In the embodiments described the core is on one side of the record carrier and the speech frequency field is produced on the other side. In the embodiment described with reference to Fig. 3, a core 2 is surrounded by a coil 3 producing the bias field, which may be A.C. or D.C. The gap 5 of the magnetic core is displaced and a pair of pole-pieces 6 rest on the record carrier 1, forming a recording gap 7. The speech frequency field is generated by an air cored coil 4 which induces a speech field in the part of the record carrier 1 lying between the pole-pieces 6. In a modification, Fig. 4, the bias field is produced by a separate iron-cored magnet 10. In a further modification, Fig. 5 (not shown), both the biassing current and speech current are applied to the terminals of the air-cored coil. In another embodiment, Fig. 6 (not shown), bias magnetisation is provided by the coil 3 on the core 2, and speech magnetisation by a pair of air-cored coils, which may be coupled with a U-shaped core.