c. Circuit with handset switch.
(1) Figure 33 shows the talking circuit of two local-battery telephone sets, each of which includes a handset
switch. It differs from the circuit of figure 28 in that the transmitters and receivers are in parallel instead of in series. This
manner of connecting the components automatically results in a closed talking circuit between the two telephones when
either handset switch is closed. This would not be the result if the components were connected in series with each of the
transmitters; in the normal position, the spring-metal conductors hold the handset switch open, and the talking circuit
would not be completed unless both handset switches were closed at the same time. In use, this could be managed, but it
would require, between the persons speaking, a coordination that is unnecessary with the circuit of figure 33.
(2) The heavy lines (fig. 33) show the complete talking circuit between the two telephone sets: the transmitter, the
battery, and the handset switch of telephone A and the receiver of telephone B. The handset switch of telephone A is
shown in the talking (closed) position, and that of telephone B is in the listening (open) position. (Telephone circuit
diagrams usually show the switch in the open position.)
In most telephone sets, the transmitter and receiver units are contained in a single mounting, the handpiece,
also called the handle and the handset handle. The combination of handpiece with transmitter, receiver, and connecting
cord is called the handset. In the local-battery telephone set, the handset usually includes the push-to-talk handset switch.
Figure 32 is an exploded view of the components of a local battery telephone handset.
a. Advantages of handset. The handset provides a convenient support or mounting for the transmitter and
receiver. In addition, its design results in an increase in the output of the transmitter. The transmitter is at the proper
distance from the mouth of the telephone user when the receiver is against his ear; more of the sound energy of the
speakers' voice is directed into the transmitter than might otherwise be the case, and the result is a greater average output
of voice current.