Valdemar Poulsen (1867-1942) and P.O. Pedersen (1874-1941), 1915

Source: http://www.kb.dk/expo/kb/porten/96-illus/345-4r.htm

The inventor pair Valdemar Poulsen and P.O. Pedersen were at the beginning of this century world-famous for their cooperation in the development of the wireless telegraph and the "buesender" transmitter, important preliminary work for the radio