| Dictabelt | |
| Type: | Grooved belt |
| Encoding: | Analog groove modulation |
| Capacity: | 15 minutes |
| Owner: | Dictaphone |
| Use: | Dictation, audio storage |
| Released: | 1947 |
The Dictabelt,[1] in early years and much less commonly also called a Memobelt, is an analog audio recording medium commercially introduced by the American Dictaphone company in 1947. Having been intended for recording dictation and other speech for later transcription, it is a write-once-read-many medium consisting of a 5mil thick transparent vinyl (according to a 1960s Dictaphone user manual: cellulose acetate butyrate) plastic belt wide and around.[2] The belt is loaded onto a pair of metal cylinders, put under tension, then rotated like a tank tread.[3] It is inscribed with an audio-signal-modulated helical groove by a stylus which is slowly moved across the rotating belt. Unlike the stylus of a record cutter, the Dictabelt stylus is blunt and in recording mode it simply impresses a groove into the plastic rather than engraving it and throwing off a thread of waste material.[4] The Dictabelt system was popular, and by 1952, made up 90% of Dictaphone's sales.[5]
Dictabelts were more convenient and provide better audio quality than the reusable wax cylinders they replaced. The belts can be folded for storage and will fit into an ordinary letter-size envelope. However, the plastic loses flexibility as it ages. If a belt is stored sharply folded for a long time, it will become permanently creased and unplayable without special treatment.[6] Dictabelts were red until 1964, blue from 1964 to 1975, then purple until they were discontinued around 1980. Each has a capacity of about 15 minutes at the standard speed. At least one Dictaphone model featured a half-speed, low-fidelity 30-minute option.
In the 1960s, Virginia required that all of its circuit courts be outfitted with Dictabelt machines.[7]
Along with a Gray Audograph sound recorder, a Dictabelt recorded the police department radio channels in Dallas, Texas, during the John F. Kennedy assassination.These recordings were reviewed by the United States House Select Committee on Assassinations (HSCA).