GB748136A - Improvements in or relating to microphones - Google Patents

Abstract

748,136. Microphones. PHILIPS ELECTRICAL INDUSTRIES, Ltd. March 10, 1953 [March 13, 1952], No. 6567/53. Class 40 (4): In a microphone comprising two readily separable sections, the first section, which embodies part of a magnetic system including a permanent magnet, is fixed upon a support, and the second section embodies the remainder of the magnetic system, the arrangement being such that when the two sections are fitted together a magnetic circuit is automatically completed by the juxtaposition of the two sections, a single operation, such as the engagement of a bayonet joint, serving to engage the two sections. The invention enables the defective portion only of a faulty microphone to be replaced, thus obviating the carrying of heavy portions of the magnetic system as spares. As shown in Fig. 2, a permanent magnet 3 is secured to a housing 1, which is in turn secured to a stand 8. Should the microphone become defective, the portion above the line B-B may be removed by turning it about a vertical axis to release the pins 20 (provided on the housing 1) from the bayonet sockets on the removable head, and a spare head is then fitted. The head comprises an iron ring 15 surrounded by an annular layer 16 of plastic material by which it is secured to an external profiled iron ring 17. The latter, which is secured to a cylindrical holder 19, supports the usual diaphragm and moving coil. Connections to the coil are made by plug and socket means of known type (not shown). In another embodiment (Fig. 1, not shown) a cylindrical permanent magnet is mounted on the stand and the remainder of the microphone, which includes the pole pieces, coil and diaphragm, fits over this magnet.