Ts _1_ and _2_ and a ground connection is made to binding post _3_. In
practice, in order to avoid the
necessity of changing the permanent wiring of the telephone set in
connecting it as an A or B Station (Fig. 170), the line conductors are
connected to the binding posts
in reverse order at the two stations; that is, for Station A
the upper conductor, Fig. 170, is connected to binding post _1_ and the
lower conductor to binding post _2_, while at Station B the upper
conductor is connected to binding post _2_ and the lower conductor to
binding post _1_. The permanent wiring of this telephone set is the same
as that frequently used for
a set connected to a line having only one station, the proper ringing
circuit being made by the method of connecting up the binding posts. For
example, if this telephone
set were to be used on a single station line, the binding posts _1_ and
_2_ would
be connected to the two conductors of the line
as before, while binding post _3_ would be connected to post _1_ instead
of being grounded. [Illustration: Fig. 175. Circuit of Two-Party
Station] _Circuits
of Four-Party-Line Telephones._ The wiring
of the telephone set used with the system illustrated in Fig. 172 is
shown in detail in Fig. 176. The wiring of this set is
arranged for local battery or
magneto working, as this method of selective ringing is more frequently
employed with magneto systems, on account of the objectionable features
which arise when applied to c