Circuits of Two-Party Line Telephones. In Fig. 175 is shown in detail the wiring of the telephone set usually employed in connection with the party-line selective-ringing system illustrated in Fig. 170. In the wiring of this set and the two following, it must be borne in mind that the portion of the circuit used during conversation might 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.

Fig. 175. Circuit of Two-Party Station
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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 connected to the binding posts 4, 5, and 6 in the proper manner to connect the set as an A, B, C, or D station, as required. For example, in connecting the set for Station A, Fig. 172, terminal 7 is connected to binding post 6 and 8 to 5. For connecting the set for Station B terminal 7 is connected to binding post 5 and 8 to 6. For connecting the set for Station C terminal 7 is connected to binding post 6 and 8 to 4. For connecting the set for Station D terminal 7 is connected to binding post 4 and 8 to 6.

Fig. 176. Circuit of Four-Party Station without Relay
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