Telephone Receivers and Radio Telegraphy

The motional-impedance circle of telephone receivers is explained, the experimental methods of determining it are given, and the equation of motion of the diafram is derived. The effect of imperfect clamping of the diafram is studied. The influence of thickness, radius, and elasticity of the diafram on its natural period are considered. The electrical, mechanical, and acoustic methods of improving receiver sensitiveness are given. The significance of audibility measurements is next treated; together with suggested improvements in the direction of quantitative measurement of receiver response. The characteristic advantages and disadvantages of monopolar, bipolar, and quadrapolar receivers are given, followed by a partial bibliography of receiver investigations.