One of the pioneers of telegraphy is Ferdinand Kovacevic (1838-1913). He invented the possibility of telegraphic connection along a single wire (the duplex connection), whereas before four wires had been used. By the way, Zagreb had its telegraph lines only six years after the first telegraph lines in the world introduced by Morse (Washington-Baltimore, 1844). Telegraph connection with the Croatian region of Lika, where Kovacevic was born, had been established already in 1854. Kovacevic published several electrotechnical books in Zagreb in German language. It is interesting that Ferdinand Kovacevic was born in the village of Smiljan in Lika, i.e., in the same village as Nikola Tesla.