SE368468

1321413 Electric bells SIEMENS AG 8 Sept 1971 [25 Sept 1970] 41811/71 Heading G5S The armature of a polarized electromagnetic acoustic generator is stiffened against bending in the direction of movement to prevent it acting as a microphone when the generator is used in a telephone set. The armature may be stiffened by means of longitudinal ribs or creases which extend over most of the length of the armature. Alternatively one, or both of the sides of the armature may be bent up at right angles to produce the required stiffness. Part of the sides may remain in the plane of the armature for ease of location. An armature 6, Fig. 8, of rectangular tubular crosssection material may also be used and the central region can be removed so as to accommodate the coils in order to keep magnetic stray flux losses at a minimum.