Dictabelt

The Dictabelt was commonly used in offices for much of the last half of the 20th century for recording memos, meetings, and so on. It worked on similar principles to the gramophone record and phonograph cylinder, using grooves to store sound, but instead of a disc or cylinder it used a plastic belt (3.5" wide) which rotated around a cylinder like a tank tread. The recording device created grooves by pressing into the plastic while it rotated past. There was no way to erase them, so each belt could only be used once for recording, but it could be played back many times.