12-24– Slightly larger than the … -Tim D. (talk) 22:37, 8 September 2009 (UTC), I'm going to go ahead and edit. A 23-inch (580 mm) rack is used for housing telephone (primarily), computer, audio, and other equipment though is less common than the 19-inch rack. With the prevalence of 23-inch racks in the Telecoms industry, the same practice is also common, but with equipment having 19-inch and 23-inch brackets available, enabling them to be mounted in existing racks. Related Subjects. The amount of motion and resulting stress depends on the structural characteristics of the building and framework in which the equipment is contained, and the severity of the earthquake. Some manufacturers of rack-mount hardware include a folding cable tray behind the server, so that the cables are held into a neat and tidy folded channel when inside the rack, but can unfold out into a long strip when pulled out of the rack, allowing the server to continue to be plugged in and operating normally even while fully extended and hanging in mid-air in front of the rack. It doesn't seem to offer any information to the reader. The height of a rack can vary from a few inches, such as in a broadcast console, to a floor mounted rack whose interior is 45 rack units (200.2 centimetres or 78.82 inches) high. Oppose rename of article. Square holes allow the OEMs to design rapidly deployable rails or Rapid Rails that automatically latch into the square holes. But in light of the rapid growth of the toll network, the engineering department of AT&T undertook a systematic redesign, resulting in a family of modular factory-assembled panels all "designed to mount on vertical supports spaced 19​1⁄2 inches between centers. Equipment can be mounted either close to its center of gravity (to minimize load on its front panel), or via the equipment's front panel holes. If something is "always" the case then "especially" does not come into play. Since the spacing between the front and rear mounting posts may differ between rack vendors and/or the configuration of the rack (some racks may incorporate front and rear rails that may be moved forwards and backwards, e.g. Seismic racks rated according to GR-63, NEBS Requirements: Physical Protection, are available,[10] with Zone 4 representing the most demanding environment. It’s called a “4-post rack” because there are 4 uprights and as you can see the holes of the rack are square. In the event of a nut being stripped out or a bolt breaking, the nut can be easily removed and replaced with a new one. However, according to my calculations that means they are not quite in the middle of the 0.625" vertical mounting rails, which seems strange. - I think there are problems with this section, but both the article as it's written, and the comment above, are inaccurate. —Preceding unsigned comment added by 194.237.142.21 (talk) 14:36, 20 September 2010 (UTC), I don't know why the article says Square-hole racks allow boltless mounting, such that the rack-mount equipment only needs to insert through and hook down into the lip of the square hole. Most racks these days are made with square holes. Heavy equipment or equipment which is commonly accessed for servicing, for which attaching or detaching at all four corners simultaneously would pose a problem, is often not mounted directly onto the rack but instead is mounted via rails (or slides). The 42U Rack is completely customizable and can handle even the heaviest loads – up […] The gap between the posts is 500 millimetres (19.69 in). Originally, the mounting holes were tapped with a particular screw thread. The 19 inch rack article gives credit to AT&T for setting the height for 1U at 1.75 inches. According to Telcordia Technologies Generic Requirements document GR-63-CORE, during an earthquake, telecommunications equipment is subjected to motions that can over-stress equipment framework, circuit boards, and connectors.