Eugene Ducretet (1844 -1915) was a scientific instrument maker, opening his first shop in 1864. He made galvanometers, Whimshurst machines, Tesla apparatus, Crookes tubes, etc. Ducretet also made telegraph instruments including keys and Morse registers. The Ducretet name is associated with the early development of wireless in France; he was an early experimenter and maker of wireless apparatus. Descriptions of his experimental Ducretet and Roger oil break spark keytransmitters and receivers are shown in Electrical World and Engineer in 1899. Ducretet wrote a wireless telegraphy guide in 1901, declaring himself a "constructeur" or builder. Ernst Roger was a collaborator in the Ducretet experiments as early as 1898.

(From http://www.telegraph-office.com/pages/DuCretet_and_Roger_key.html )