Valdemar Poulsen in Denmark would succeed in 1898 where Smith had failed. He built and patented the first working magnetic recorder called the Telegraphone Poulsen had become a telephone engineer at the Copenhagen Telephone Company in 1893 and began to experiment with magnetism to record telephone messages. By 1899 he filed U.S. patent 661,619 for a vertical wire-covered cylinder, and in 1900 demonstrated improved drum and horizontal wire cylinder models at the 1900 Paris Exhibition. While making these improved models, Poulsen and his partner Peder O. Pedersen discovered the application of a direct current to the recording head, called dc bias, improved the sound quality on a steel tape version of the Telegraphone. At the Paris fair, Poulsen recorded the voice of Emperor Franz Joseph, today preserved in the Danish Museum of Science and Technology as the oldest magnetic sound recording. Poulsen stopped his work on magnetic recording and turned to radio after 1902, and only a small number of his machines were made in Denmark and Germany. The American Telegraphone Company acquired the patent rights in 1905 and made dictating machines, selling 50 to the Du Pont Company. However, the signal remained weak without amplification and the wire spools became twisted and were unreliable. The wax cylinder phonographs of the rival Ediphone and Dictaphone companies were cheaper and more reliable. By 1918, the company went into receivership and stopped manufacturing after 1924.
National Museum of Science and Technology in Denmark, has exhibits of the compass needle used by H.C. ¯rsted in the discovery of electromagnetism in 1820 and the first wire recorder in the world, invented by Valdemar Poulsen in 1898.