FRIEDRICHSDORF, a town of Germany, in the Prussian province of Hesse-Nassau, on the southern slope of the Taunus range, 3 m. N.E. from Homburg. Pop. 1300. It has a French Reformed church, a modern school, dyeworks, weaving mills, tanneries and tobacco manufactures. Friedrichsdorf was founded in 1687 by Huguenot refugees and the inhabitants still speak French. There is a monument to Philipp Reis (1834-1874), who in 1860 first constructed the telephone while a science master at the school.