Its main competitors were the `` Bélinographe '' by Édouard Belin first , then since the 1930s the `` Hellschreiber '' , invented in 1929 by German inventor Rudolf Hell , a pioneer in mechanical image scanning and transmission .
Its main competitors were the `` Bélinograf '' by Édouard Belin first , then since the 1930s the `` Hellschreiber '' , invented in 1929 by German inventor Rudolf Hell , a pioneer in mechanical image scanning and transmission .