. American telephone practice . ing into such an exchangeare frequently party lines of the bridging type, and more often thannot a call on such a line is for another party on the same line. Sucha call would throw the switch-board drop and bring the operatorto the board, unless some means were provided for the operator to 206 AM ERIC AX TELEPHOXE PRACTICE. distinguish between calls that required her attention and those thatdid not. Obviously the night alarm method of attracting theoperator does not answer in this case, for with it all calls are alikeat the switchboard. Frequently the magneto be
. American telephone practice . ing into such an exchangeare frequently party lines of the bridging type, and more often thannot a call on such a line is for another party on the same line. Sucha call would throw the switch-board drop and bring the operatorto the board, unless some means were provided for the operator to 206 AM ERIC AX TELEPHOXE PRACTICE. distinguish between calls that required her attention and those thatdid not. Obviously the night alarm method of attracting theoperator does not answer in this case, for with it all calls are alikeat the switchboard. Frequently the magneto bell is used as a line signal in place ofa drop. This serves admirably unless there are several lines to beso equipped, in which case confusion is liable to exist as to whichbell sounded. This may be overcome by using a magneto bell anda drop both bridged across the line, the drop serving to indicatewhich bell sounded. This, however, makes two bridges across eachline where one should suffice, which is often a disadvantage in case. FIG. 190.—COMBINED DROP AND RINGER. of heavily loaded lines. To obviate this a combined magneto belland drop is sometimes used. Two of these mounted on a common strip are shown in Fig. 190,the particular device illustrated being that of the Kellogg Switch-board and Supply Company. In this, as in types of other manu-facturers, the bell tapper carries a small conical latch which projectsforwardly to engage the shutter when in its raised position. Thefirst movement of the tapper in either direction releases the shutter,after which the tapper is free to play between the gongs. This de-vice is usuallv arranged to mount directly on the front of the switch-board, and for that purpose the line jack is often associated directlywith the bell as shown in this figure. The principal circuits used in magneto switch-boards, and also MAGNETO SWITCH-BOARD FOR SMALL EXCHANGES. 207 many of the various pieces of apparatus, such as drops, jacks, ring-ing and listening key
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