Edison, His Life and Inventions by Frank Lewis Dyer;Thomas Commerford Martin
page 118 of 844 (13%)
page 118 of 844 (13%)
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dispatch, by perforating narrow strips of paper with holes--work which
can be done either by hand-punches or by typewriter apparatus. A certain group of perforations corresponds to a Morse group of dots and dashes for a letter of the alphabet. When the tape thus made ready is run rapidly through a transmitting machine, electrical contact occurs wherever there is a perforation, permitting the current from the battery to flow into the line and thus transmit signals correspondingly. At the distant end these signals are received sometimes on an ink-writing recorder as dots and dashes, or even as typewriting letters; but in many of the earlier systems, like that of Bain, the record at the higher rates of speed was effected by chemical means, a tell-tale stain being made on the travelling strip of paper by every spurt of incoming current. Solutions of potassium iodide were frequently used for this purpose, giving a sharp, blue record, but fading away too rapidly. The Little system had perforating apparatus operated by electromagnets; its transmitting machine was driven by a small electromagnetic motor; and the record was made by electrochemical decomposition, the writing member being a minute platinum roller instead of the more familiar iron stylus. Moreover, a special type of wire had been put up for the single circuit of two hundred and eighty miles between New York and Washington. This is believed to have been the first "compound" wire made for telegraphic or other signalling purposes, the object being to secure greater lightness with textile strength and high conductivity. It had a steel core, with a copper ribbon wound spirally around it, and tinned to the core wire. But the results obtained were poor, and in their necessity the parties in interest turned to Edison. Mr. E. H. Johnson tells of the conditions: "Gen. W. J. Palmer and some New York associates had taken up the Little automatic system and had |
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