Edison's electro-motograph, 1879 (engraving)

Edison's electro-motograph. Mr Thomas A. Edison; the inventor of the electro-motograph; states that he has a machine in operation in his laboratory constructed upon the principle shown in fig. 169; with which he has succeeded in repeating automatic signals from one circuit into another; at the rate of one thousand two hundred words per minute; an average of six thousand letters; or twenty-four thousand waves per minute; compelling the lever A (fig. 169) to move backward and forward from the point on the left to the point D on the right four hundred times per second.