Equipment of Local-Battery Telephone System.
The equipment of the local-battery telephone system may be classified as telephone-station equipment,
central-office equipment, and interconnecting equipment. The unit of equipment at the telephone station is the telephone
set, and the unit of equipment at the central office is the switchboard. The interconnecting equipment is the telephone
line. Because electrical properties of the telephone line are, in general, similar for both the local-battery and the common-
battery systems, discussion of the line will be deferred for a later chapter, following the discussion of the common-battery
In both systems, the telephone set, often simply called the telephone, is the device supplied to the telephone
user to initiate and receive telephone calls. In the telephone circuit of figure 25, the group of components at each station
comprises a simple telephone set. The group includes the transmitter, the receiver, the hand generator, and the ringer.
a. Principle circuits of telephone set. The components of the telephone set of both systems are connected to
provide two principal circuits: the talking circuit in A, figure 28, and the signaling circuit, shown in B. Each one is the
telephone circuit of figure 25 modified to represent two local-battery telephone sets connected directly to each other. The
circuits of the telephone sets are completed by the telephone line connected to terminals L1 and L2 of the sets.
(1) The talking circuit of the telephone set provides an electrical path for the voice current.
Its prime components are the transmitter and the receiver.
In the local-battery telephone set, it also
includes a battery. In the two-station local-battery system shown in A, the heavy lines show the com-