English: A Telegraphone steel wire recorder , the first audio magnetic recording technology, invented in 1898 by Danish-American engineer Valdemar Poulsen . Working similarly to a tape recorder, the fine steel wire unwinds from one reel, passes though a recording head, and is wound onto the other reel. In the head, the audio signal to be recorded passes through an electromagnet, creating a varying magnetic field. This creates a varying magnetization in the wire which is a record of the instantaneous sound amplitude. To play it back the wire is passed through a playback head where another electromagnet detects the varying magnetization and translates it back to a varying electrical signal, which is amplified and applied to a loudspeaker. Wire recorders had poor audio quality and were replaced by magnetic tape recording in the 1940s.

This example from 1922 was used by the RCA transatlantic telegraph operations center in New York to record incoming high speed Morse code radiotelegraph messages from Europe at 100 WPM, which were then replayed at lower speed to telegraph operators who translated it into text and typed it onto telegram forms to be sent to the recipient.