GB411566A - Improvements relating to microphones and receivers - Google Patents

Abstract

411,566. Transmitters and receivers. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and SUTTON, G. W., 25, Cranleigh Road, Merton Park, both in London. Dec. 30, 1932, No. 36898. [Class 40 (iv).] Liability to electrolytic corrosion at places where a metal diaphragm of a telephone transmitter or receiver is clamped to the casing or other support giving rise to a comparatively high contact potential is reduced by arranging that, at the places where contact would take place, the area of contact or such of it as is most exposed to moisture is covered by material giving rise to no or a comparatively low contact potential. According to one arrangement in which an aluminium alloy diaphragm is clamped to a brass case by a brass ring, the case and ring are plated with cadmium or zinc. With certain combinations of materials, the diaphragm may be plated instead of the case and ring. According to a modification, Fig. 1, rings or washers 4, 5 of the same material as the diaphragm or of a metallic material giving rise to a comparatively low contact potential relative to the diaphragm material are interposed between the diaphragm 1 and the case 2 and clamping ring 3. If desired, either or both rings may be omitted and the ring 3 made of the same material as the diaphragm or of a metallic material giving rise to a comparatively low contact potential relative thereto. Fig. 3 shows a construction of receiver in which an iron diaphragm 1 is clamped to a brass &c. case 2 by a non-metallic earpiece 3, a packing ring 5 of iron or of a metallic material giving rise to a comparatively low contact potential relative to iron being interposed between the diaphragm and the case.