GB295342A - Improvements in or relating to telephonic apparatus - Google Patents

Abstract

295,342. Turner, P. K., and Rickets, W. J. May 4, 1927. Magnetic instruments; diaphragms.- In a telephone transmitter or receiver a short-circuited conductor located in a unidirectional field is magnetically linked with the telephonic coils. As shown in Fig. 1, two diaphragms g, g<1> of a receiver or transmitter are connected by pairs of struts h to a shortcircuited conductor d which is pivoted so that its sides oscillate in unidirectional fields produced in the gaps y, y<1> formed between the polar extensions a<1>, a<2> of a permanent or electro-magnet a and a central magnetic member b, supported on extensions a<3>, a<4>. The telephonic coils c, c<1> are supported on the central member b. The closed circuit conductor may be rectangular, circular or triangular and may be made wholly of conducting material such as copper, aluminium or iron or partly of iron and partly of a better conducting material. Instead of completing the magnetic circuit of the member b through the magnet a separate soft iron flux paths may be provided. The magnetic system is supported by vertical supports k, k<1> on a base m, the diaphragms g, g<1> being supported between a ring i of soft material and a strip j of flexible material. In the modification shown in Fig. 4, the conductor comprises two loops having a common central side d<1>. The outer sides are located in gaps y, y<1> formed between the poles a<1>, a<2> of an electromagnet a and the links of an auxiliary magnetic circuit r associated with the telephonic coil c. The electromagnet is permanently excited by coil s, s<1>, and the conductor is supported for reciprocating motion by ligaments k on pins t<1> fixed to the pole pieces. Alternatively the ligaments may extend through holes on the pole pieces to external tensioning means. The conductor is mounted on a diaphragm g flexible supported at u' and provided with a supplementary cone g*. In a further modification one side only of the closed circuit conductor is located in an air gap, the other side forming the axis of oscillation.