Page:Popular Science Monthly Volume 70.djvu/240

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into, and were connected to the disconnecting switch through an indicator 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. Doolittle'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 switchboard for use in Bridgeport, in which he substituted simple switches for the usual telegraph plugs, as the former were more easily manipulated 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 operator'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