FIGURE 17. Action of Soft Iron-ore
Electron Agent on Diaphragm
b. A receiver that provides improvements in efficiency and frequency response is shown in figure 19.
(1) The simple diaphragm of earlier receivers is replaced by a ring armature, a dome-shaped diaphragm of
phenolic impregnated fabric cemented to a circular magnetic ring. The outer edge of the ring rests on a circular seat of
nonmagnetic material. The inner edge is close to a circular pole piece which conducts the flux from a ring-shaped
permanent magnet. This design lowers the mechanical impedance of the diaphragm and improves the radiation
efficiency. As a result, when the receiver is held off the ear, the intelligibility of speech is much better than that of other