b. Structure of handset. The material
of the handpiece is molded bakelite or a phenol
plastic. Its ends are designed to contain the
transmitter and receiver elements. These are
retained by molded bakelite or phenolic plastic
caps, perforated to pass the sound energy. The
transmitter cap is called the mouthpiece, the
receiver cap the earpiece. Connections to the
transmitter and receiver are made by silver-
plated contact springs, fastened to terminals
molded in the plastic. In the local-battery
telephone handset, the handle is recessed for
mounting the push-to-talk switch in the handle.
Metal tubes extending through this handle carry
the necessary conducting wires between the
transmitter, receiver, and handset switch.
FIGURE 32. Exploded View of Handset of
Local-Battery.
FIGURE 33. Talking Circuit of Two
Telephone Sets with Handset
72
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