Fig. 12 from the plate on "telegraph" in rees's cyclopædia, illustrating richard lovell edgeworth's proposal for an optical telegraph system in ireland. Each indicator was used to display the number of a particular unit, to form a four-figure number, which then represented characters and words via a codebook. For further explanatory text, see entry on "telegraph", volume 35 of the cyclopædia. Date: 1802-1820 (serial publication of the source work).
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