GB523811A - Improvements relating to audiphones or bone conduction telephone instruments - Google Patents

Abstract

523.811. Deaf aids. KOCH, H., and DICTOGRAPH PRODUCTS CO., Inc. Jan. 14, 1939, No. 1362. [Class 40 (iv)] A bone-conduction audiphone has a vibrating system comprising two members (e.g., the permanent magnet and its armature) connected by a stiff. spring member, one member being secured to the instrument casing and the other member being connected to a contact member which forms part or the whole of one wall of the casing, the arrangement being such that the vibrations of both the contact member and the casing are conveyed to the bone structure. As shown in Fig. 2, the reed or armature 22 secured to the face plate 11 of the casing 10 carries the permanent magnet 25 to which is secured a pole-piece 26 surrounded by -a speech-coil 27. A button 12 projecting slightly beyond the face plate 11 is adjustably connected to the magnet 25. In a modification, Fig. 3 (not shown), the magnet is attached to the reed by a spring strip and the threaded shank of the button is additionally secured to a cantilever spring mounted on the reed so that adjustment of the air gap between the reed and pole-piece can be effected. In further modifications the permanent magnet is secured to the casing and a button projecting through the face plate is carried by the reed, Fig. 4 (not shown), or a plate carried by the reed is recessed within the casing. Fig. 6 (not shown). In a further modification, Fig. 5, the reed 54 carries the face plate 56 which is separated from the bodv 53 of the casing by a thin ring 57 of soft rubber, felt or similar resilient material. The ends of the coil 27 are preferably connected to contact plates 29 engaged by springs 30 engaged by plungers 31 which project into apertures, 32 for the prongs of a connecting cord from a microphone circuit.