ight
be wired in a number of ways without affecting the principle of
selective ringing employed; however, the circuits shown are those most
commonly employed with the respective selective ringing systems which
they are intended to illustrate. In connecting the circuits of this
telephone instrument to the line, the two line conductors are
connected to binding posts _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 common-battery systems. In this figure the
line conductors are connected to binding posts _1_ and _2_, and a
ground connection is made to binding post _3_. In order that all sets
may be wired alike and yet permit the instrument to be connected for
any one of the various stations, the bell is not permanently wired to
any portion of the circuit but has flexible connections which will
allow of the set being properly connected for any desired station. The
terminals of the bell are connected to binding posts _9_ and _10_, to
which are connected flexible conductors terminating in terminals _7_
and _8_. These terminals may be c