a primary winding, P, and a secondary winding, S, a ringer, RG, a capacitor, C, and a hookswitch, H. Each telephone set
has a circuit similar to the circuit of a local-battery telephone set except for these differences: There is no battery or hand
generator in the common-battery set, and the handswitch shown is replaced by a hookswitch in the common-battery set.
(In a local-battery system, the hand generator is needed to signal the operator. In a common-battery system, the
switchboard operator is signaled automatically by the operation of the hookswitch.)
(2) The primary and secondary windings of the induction coil are shown in figure 45 as separate windings. This
representation, although not important for the discussion of the operation of the basic circuit of figure 45, must be used in
connection with the explanation of some of the other circuits which will follow.
(3) The theory of operation of the several components of a common-battery telephone set--transmitter, receiver,
inductions coil, capacitor and ringer--is the same as that of corresponding components of a local-battery telephone set.
FIGURE 45. Basic Circuit of Common-
Battery Telephone Set.