. Bulletin. Science. ifliiiiii!iii!'sii'^yiii?⬠" 'lib â â. Figure 44.âAbove, and onjaang page: English telegraph offices of the mid-igth century. From T. Shaffner, The Telegraph Manual, New York, 1859, pp. 233, 235. identical commutator moving synchronously at the re- ceiving station switched the combinations of signals to four groups of polarized relays, each relay being con- nected to one of the five subdivisions of the four seg- ments of the receiving commutator. Each group of relays actuated a certain one of the four printers at the end of the line. With this device the operator at
. Bulletin. Science. ifliiiiii!iii!'sii'^yiii?⬠" 'lib â â. Figure 44.âAbove, and onjaang page: English telegraph offices of the mid-igth century. From T. Shaffner, The Telegraph Manual, New York, 1859, pp. 233, 235. identical commutator moving synchronously at the re- ceiving station switched the combinations of signals to four groups of polarized relays, each relay being con- nected to one of the five subdivisions of the four seg- ments of the receiving commutator. Each group of relays actuated a certain one of the four printers at the end of the line. With this device the operator at each transmitting station could send about 150 letters per minute. (See figs. 49-53.) Also tried was another method of multiple teleg- raphy that used different transmittersâeach with its own characteristic frequency of alternating currentâ that sent the different currents simultaneously over the common line. These currents were sepa- rated at the receiving end of the telegraph by use of analyzers, each of which was sensitive to only one frequency. This method of communication did not have any commercial success until the 20th century, but such harmonic multiple telegraphy led to another means of electrical communication. After trying to send tones and combinations of tones over a telegraph line, some inventors went on to study the 310 BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution; United States. Dept. of the Interior; United States National Museum. Washington, Smithsonian Institution Press, [etc. ]; for sale by the Supt. of Docs. , U. S. Govt Print. Off
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