[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 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.

[Illustration:  Fig. 176.  Circuit of Four-Party Station without Relay]

[Illustration:  Fig. 177.  Circuit of Four-Party Station with Relay]

The detailed wiring of the telephone set employed in connection with the system illustrated in Fig. 173 is shown in Fig. 177.  The wiring of this set is arranged for a common-battery system, inasmuch as this arrangement of signaling circuit is more especially adapted for common-battery working.  However, this arrangement is frequently adapted to magneto systems as even with magneto systems a permanent ground connection at a subscriber’s station is objectionable inasmuch as it increases the difficulty of determining the existence or location of an accidental ground on one of the line conductors.  The wiring of this set is also arranged so that one standard type of wiring may be employed and yet allow any telephone set to be connected as an A, B, C, or D station.