stations. A small electric bell is placed in each subscriber's house or office, having a hook projecting from its base on which the hand telephone is hung when not in use (Fig. 20). When the telephone is removed this hook can be thrown either to the right Fig. 20. or left. When thrown to the right the line wire on one side of the station is connected through the telephones to the ground and the line on the other side is opened, preventing any one on that side hearing what is said. When thrown to the left the reverse is true. It is obvious that no person between the two that are conversing can put his telephone in circuit without breaking the line, and consequently, interrupting the conversation. All other stations on the circuit are notified that the line is being used by the striker being away from the bell. In this case the subscriber must not attempt to call or use the telephone. The signaling is done by pressing and releasing a knob the requisite number of times. . . .

To make a good telephone exchange switchboard, however, out of an ordinary telegraph switch, we concede that considerable remodelling is necessary; and after the first heat of invention was over, practical men began to look about them, to see the disadvantages they were laboring under and endeavor to overcome them. It was seen that time and money were, in telephone offices, the two main articles to be economized. Time, because speed of connection is the very life-blood of the business. Money, because in many of the exchanges the telephone business was managed and owned by men of little or no capital; and, in others, the expense, in any case, would be great, and economy was necessary to make anything at all out of the business. Soon, therefore, it became obvious that the telephone switch must be compact; all the apparatus must be easily and quickly under control; everything about it must be well made and well put together; the motions required in a connection must be reduced to a minimum, and yet the apparatus must be cheap. The cry of cheapness for a long time obscured the vision of the practical man.