Wikipedia
Pilottone
Pilottone (or Pilotone) and the related neo-pilottone are special synchronization signals recorded by analog audio recorders designed for use in motion picture production, to keep sound and vision recorded on separate media in step. Before the adoption of timecode by the motion picture industry in the late 1980s, pilottone-sync was the basis of all professional magnetic motion picture sound recording systems, whereas most amateur film formats used pre-striped magnetic coating on the film itself for live-sound recording.