Fig. 186. Principle of Broken-Line System
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Obviously, if a proper ringing current is sent over the metallic circuit from the central office, only the bell at Station A will operate, since the bells at the other stations are not in the circuit. If by any means the switch lever 2 at Station A were moved out of engagement with contact 1 and into engagement with contact 3, it is obvious that the bell of Station A would no longer be in circuit, but the limb R of the line would be continued to the extension Rx and the bell of Station B would be in circuit. Any current then sent over the circuit of the line from the central office would ring the bell of this station. In Fig. 187 the switches of both Station A and Station B have been thus operated, and Station C is thus placed in circuit. Inspection of this figure will show that the bells of Station A, Station B, and Station D are all cut out of circuit, and that, therefore, no current from the central office can affect them. This general scheme of selection is a new-comer in the field, and for certain classes of work it is of undoubted promise.
Fig. 187. Principle of Broken-Line System
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