 Magnetic recording was conceived as early as 1878 by the American engineer Oberlin Smith and demonstrated in practice in 1898 by Danish engineer Valdemar Poulsen.Analog magnetic wire recording, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves with a constant speed past a recording head.An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal.