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POPULAR SCIENCE MONTHLY 



Fig. 16. 



into, and were connected to the disconnecting switch through an indi- 

 cator and jump jack. 



In July, 1878, Thomas B. Doolittle planned and had constructed 

 by Charles Williams, Jr., of Court Street, Boston, a twenty-circuit 

 telephone switchboard, which Mr. Williams has stated ' was the first 

 switchboard completely equipped with signaling apparatus ever made 

 at my establishment.' This board (Fig. 17) was placed in Mr. Doo- 

 little's exchange at Bridgeport, Connecticut, which succeeded to the 

 first mutual telephone exchange system, and is the small board shown 

 in Fig. 18. 



In 1877, Mr. Doolittle had made a small six-point cross-bar switch- 

 board for use in Bridgeport, in which he substituted simple switches 

 for the usual telegraph plugs, as the former were more easily manipu- 

 lated in making connections. Then he brought out the small board 

 above referred to. Meanwhile he devised his ' direct-connecting board ' 

 (Fig. 18) in which each line terminated in the board after passing 

 through a single stroke bell, to the hammer of which was attached a 

 hollow brass ball suspended by a silk thread. To each circuit an op- 

 erator's telephone was attached, and the cords were of sufficient length 

 to reach the furthermost limit of the board. Following a subscriber's 

 call the stroke of the bell set the brass ball to swinging, thus notifying 



