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Rack with sample component sizes including an A/V half-rack unit. A rack unit (abbreviated U or RU) is a unit of measure defined as 1 + 3 ⁄ 4 inches (44.45 mm). [1] [2] It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well as the height of equipment that mounts in these frames, whereby the height of the frame or equipment is expressed ...
The size denotes the width of the faceplate for the installed equipment. The rack unit is a measure of vertical spacing and is common to both the 19 and 23-inch racks. Hole spacing is either on 1-inch (25 mm) centers (Western Electric standard), or the same as for 19-inch (482.6 mm) racks (0.625 in or 15.9 mm spacing).
Two common heights are 3U (a 100 mm card in a 5.25 in (133.35 mm) subrack) and 6U (a 233.35 mm card in a 10.5 in (266.70 mm) high subrack). As two 3U cards are shorter than a 6U card (by 33.35 mm), it is possible to install two 3U cards in one slot of a 6U subrack, with a mid-height structure for proper support.
The height increment of a front panel is 1U, equal to 44,45 mm. Thus is would seem that the actual value of the U unit is in fact 44.45 mm, NOT 44.50 mm as stated in the article. This makes a lot of sense, since the system is obviously based on Imperial units, and 1.75 inch is in fact 44.45 mm. I would suggest that this be corrected in the article.
3U (5.06 inches or 128.5 mm), where height "U" is measured in rack units, rounded for a lip (nb: 3U in standard rack units would be 5.25 inches or 133.3 mm). 1HP (0.2 inches or 5.08 mm), where width "HP" is measured in horizontal pitch units. A card width is generally integer multiples of 1HP, although some manufactures work in multiples of 0.5HP.
FlexATX specifies that a motherboard be no larger than 9 × 7.5 in (229 × 191 mm), and can have no more than three expansion slots. The term is used also for the form factor of a PSU that is smaller than a standard ATX PSU and is used in small cases that host a FlexATX or Mini-ITX motherboard or in thin rackmount servers such as 1U racks .
Date/Time Thumbnail Dimensions User Comment; current: 00:32, 6 August 2007: 318 × 609 (30 KB): Sakurambo~commonswiki {{Information |Description=A section of rail from a 19" server rack unit, showing how typical rack units 1U through 4U are distributed among the mounting holes. |Source=Own work, based on the public-domain image [[w:Image:Server-Rack-Rail-
Horizontal pitch (HP) is a unit of length defined by the Eurocard printed circuit board standard used to measure the horizontal width of rack mounted electronic equipment, similar to the rack unit (U) used to measure vertical heights of rack mounted equipment.