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