CHAPTER 5
COMMON-BATTERY TELEPHONY
Section I. Basic Principles and Components of Common-Battery System.
44.
Introduction.
a. The essential difference between the common-battery systems discussed in this chapter and the local battery
systems discussed in chapter 4 is the number and location of the batteries which furnish the power to operate the system.
A common-battery telephone system is one in which a centrally located storage battery is used in place of the individual
dry cells required at each telephone station of a local-battery system. The single common battery serves all the stations of
the system.
b. As might be expected, many of the components of common-battery systems are identical with, or at least very
similar to, the corresponding local-battery components. In this chapter, such components are only briefly treated, and the
similarities and differences between them and their local-battery counterparts are pointed out.
c. In order that a single battery may serve all stations in the system, it is necessary that the stations be in parallel
with each other as far as dc is concerned, with the battery connected across the line instead of in series with it. It follows
from this requirement that certain circuits and components of common-battery systems are different from their local-
battery counterparts, and that certain other circuits, not used at all in local-battery systems, are included in a common-
battery system. Such circuits, which differ materially from components discussed in earlier chapters, are explained fully
here. In presenting the complexities of common-battery systems, the method followed is the same as that in chapter 4,
starting with a highly simplified circuit incorporating only the barest essentials, and then adding components and auxiliary
circuits one at a time as the need for them is developed. In the interest of clarity, it sometimes will be necessary to
postpone the discussion of certain components when they first are mentioned until a later point, and therefore only by a
careful reading of the entire chapter can the complete system, its components, and their functions and interrelations be
understood.
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