. American telephone practice . j^y VL3 FIG. 509.—TRANSMITTING DEVICE, REAR VIEW. then released and returned to its normal position by a retractilespring, and in so doing the notched wheel within the box causes 704 AMERICAN TELEPHONE PRACTICE. a pair of springs to make a series of contacts, serving to im-part a vertical movement to the first selector of the subscribercalling. The operation is then repeated for the second, third andfourth digits in the number, the second movement of the dial impart-ing to the second selector the required vertical motion, the thirddoing the same for the connecto
. American telephone practice . j^y VL3 FIG. 509.—TRANSMITTING DEVICE, REAR VIEW. then released and returned to its normal position by a retractilespring, and in so doing the notched wheel within the box causes 704 AMERICAN TELEPHONE PRACTICE. a pair of springs to make a series of contacts, serving to im-part a vertical movement to the first selector of the subscribercalling. The operation is then repeated for the second, third andfourth digits in the number, the second movement of the dial impart-ing to the second selector the required vertical motion, the thirddoing the same for the connector, and the fourth serving to rotatethe arm of the connector into engagement with the line wanted, asalready described. The circuit and some of the mechanisms of the subscribers in-strument diagrammatically arranged are shown in Fig. 511. Thisis typical of the latest desk-stand telephone of the Automatic Elec-. FIG. 510.—TRANSMITTING DEVICE, SIDE VIEW. trie Company, this being somewhat more simple than is the wall set,although its electrical functions are identical therewith. The two sides of the line which, in manual practice, are designatedby such terms as tip and sleeve, or tip and ring, are, inautomatic practice, designated as vertical and rotary. Thesenames are given the limbs of the line because over the vertical sideof the line are sent those impulses which impart to the switch its ver-tical motion, and over the rotary side of the line single impulsesare sent, as a result of which the various switches are started in theirrotary movements. The letters, V and R, will be used through-out this discussion as designating the vertical and rotary sides ofthe line, respectively, or such extensions thereof as may be brought AUTOMATIC SWITCH-BOARD SYSTEMS. 705 about at the central office as a result of the movements of theswitches. The two limbs, V and R, are shown in Fig. 511, and in all posi
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