. An elementary book on electricity and magnetism and their applications. ywinding, which in turn induces an alternating current in thesecondary, which is superposed on the line. 361. Telephone switchboards. Telephone switchboards varyin style and are, as a rule, quite complicated, since an exchangeis always connected to a large number of wires and since theconnections of the telephone wires must be arranged so thatthe operators and the subscribers are able to signal and talkto each other and so that the subscribers lines may be quicklyconnected together. In the earlier and the simpler forms o
. An elementary book on electricity and magnetism and their applications. ywinding, which in turn induces an alternating current in thesecondary, which is superposed on the line. 361. Telephone switchboards. Telephone switchboards varyin style and are, as a rule, quite complicated, since an exchangeis always connected to a large number of wires and since theconnections of the telephone wires must be arranged so thatthe operators and the subscribers are able to signal and talkto each other and so that the subscribers lines may be quicklyconnected together. In the earlier and the simpler forms of telephone switch-boards still used for small exchanges, the subscribers wireson entering the exchange are each connected to a switchboardcircuit which contains a spring jack and an electromagnet,which controls a drop or shutter. The circuit terminates at aground plate. One form of the electromagnet with its drop Fig. 382. — Fixed and port-able parts of desk set oftelephone instruments. THE TELEPHONE 529 Book attached to/^ Armature. D Drop Raised Position. Plate carryingSubscriber». Number Fig. 383. — Electromagnet and shutter fortelephone switchboard. is illustrated in figure 383. The armature A of the electromag-net M has a hook D, which ordinarily supports the shutteror drop P, which ishinged at the bottomin a vertical the subscribersends a current over theline from his magneto,the armature A is at-tracted, the drop is re-leased and falls into thehorizontal position illus-trated in figure 383 andthereby discloses the subscribers number, which is painted atits back. A spring jack is an arrangement by means of which anelectrical connection may be made by inserting a metallicplug into a hole so that it touches a spring which is in electricalconnection with the circuit. Figure 384 illustrates one form ofa spring jack. When a subscriber calls by working his magneto,the fact is indicated at the exchange by the fall of the dropbelonging to his line. T
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
