FIGURE 13. U.S. Army Type T-45 Lip
a. Function of telephone receiver. The function of the telephone receiver is to reproduce the sound made in the
transmitter at the other end of the transmission line. It is accomplished by reconverting to sound waves the electrical
waves transmitted to it. The function of the receiver, therefore, is the reverse of that of the transmitter. The receiver also
must prevent leakage of sound. This requirement is satisfied by the construction of the earpiece, which is designed to be
held close to the ear.
b. Types of telephone receivers. According to their means for converting electrical waves to sound waves,
telephone receivers may be either magnetic-diaphragm or moving-conductor types.
(1) The magnetic-diaphragm receiver (A, fig. 14) contains a permanent magnet, and operates by variation of the
strength of its magnetic field. The amplitude and frequency of the variation of the magnetic field cause a corresponding
variation of the motion of the magnetic diaphragm. This is the receiver most commonly used in telephone