Marcel Bayard (1895-1956) was a French mathematician and telecommunications engineer. He made pioneering contributions to the telecommunications theory in the 1930s. As Chief Engineer of French telecommunications after World War II, he supervised and modernized the French telecommunications system. 
Biography.
Born in 1895, son of a farmer, he obtained his baccalauréat in 1914. He served as young officer during the World War I where he was seriously wounded and received the Croix de Guerre. He entered the École polytechnique in 1919.
In 1923 he became an engineer in the French PTT and started his career by supervising submarine cable installations. As professor at the "École nationale supérieure des télécommunications", he published several noted scientific papers. He was the first to establish in 1935 what is called the “Bayard-Bode relations” (relations linking Phase and Amplitude of a signal in specific cases. He also wrote the theorical electricity lessons for the École nationale supérieure des télécommunications where he was the first in France to introduce the matrix calculations for electrical network theory.
He represented France in international telecommunications committees in the 1930s.
After World War II, he was responsible for rebuilding and modernizing the French telecommunications network.
References.
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Sources
Les pionniers de la téléphonie sous-marine 