5.2.9 Office Dictation Systems Sound recording technology has been marketed and used as a business tool virtually since its inception. Three broad categories of mechanical dictation formats can be defined, namely cylinders, discs and belts (see 5.4.15 for magnetic dictation formats). Early cylinders and recording equipment sold for office use were generally the same as those used for other purposes, the resultant recordings being on standard 105 mm (4 1/8”) length cylinders (see However cylinder formats designed specifically for office use were made for many years by both Columbia (later Dictaphone) and Edison, both producing cylinders approximately 155 mm (6 1/8 inch) long with 160 and 150 grooves/inch respectively (Klinger 2002). Some later cylinder dictation machines recorded electrically rather than acoustically, but little if anything is known today about pre- emphasis applied. Various grooved disc formats were launched, mostly after World War II, including the Edison Voicewriter and the Gray Audograph.While many such formats require specialist replay equipment, seven inch flexible Edison Voicewriter discs may be replayed on a standard turntable employing a US-type spindle adaptor and microgroove stylus. Recording speeds for these were generally below 33 1/3 rpm. Beginning in the 1940s, several belt recording formats appeared. These were essentially flexible plastic cylinders, fitted over a twin drum assembly for recording and playback. Perhaps the best known of these is the Dictaphone Dictabelt. Their flexibility allowed them to be flattened for storage and delivery much like other office stationery, but this often resulted in their becoming permanently creased, creating challenges for the replay engineer. Carefully and gently raising the temperature of the belt and replay equipment has been known to be effective in this regard, though how appropriate this is will depend on, among other things, the particular plastic used in the belt. Specialist replay equipment will be required to replay belt formats.