. American telephone practice . nted bya small circle, and then through the winding of the annunciator orelectro-magnetic drop, represented by a larger circle. From this the 176 MAGNETO SWITCH-BOARD FOR SMALL EXCHANGES. 177 circuit of each line passes to a common wire leading to the spring-jack serves the purpose of allowing the operator to makea connection between a flexible conductor and any line circuit, whilethe drop serves the purpose when actuated by a current from thesubscribers generator to display a visual signal to the operator, asan indication that her attention is require
. American telephone practice . nted bya small circle, and then through the winding of the annunciator orelectro-magnetic drop, represented by a larger circle. From this the 176 MAGNETO SWITCH-BOARD FOR SMALL EXCHANGES. 177 circuit of each line passes to a common wire leading to the spring-jack serves the purpose of allowing the operator to makea connection between a flexible conductor and any line circuit, whilethe drop serves the purpose when actuated by a current from thesubscribers generator to display a visual signal to the operator, asan indication that her attention is required1 on that line. After thecall has been received on a line, the drop is of no further use, whilethe line is being used by the subscriber for conversation, and there-fore arrangements are made in each spring-jack to cut off the dropof each line when the connection is made. Each operator is providedwith a number of pairs, c, of flexible conducting cords and plugs bymeans of which and the spring-jacks she may connect any two lines. FIG. 155.— GROUNDED-CIRCUIT SWITCH-BOARD. for conversation, at the same time cutting off the call-receiving de-vices or drops belonging to those lines. The operator is also providedwith a telephone set represented at T, and a calling generator repre-sented at G. One terminal of each of these is connected with theground1, as shown, and the other terminal of each may be put inconnection with a flexible cord or plug, enabling the operator eitherto converse withw a subscriber by means of her telephone set orto ring the bell of a subscriber who is called for, by means of hergenerator. Looking now at Fig. 155, we see that lines 2 and 3 have been con-nected for conversation by means of a flexible cord, 0, similarly lines7 and 8 and lines 4 and 11 have been connected by cords b and 178 AMERICAN TELEPHONE PRACTICE. Each of these pairs of lines., it will be seen, are cut off from the call-receiving devices, and each pair of subscribers thus enjoys an ex-cl
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