#4u full#
These are commonly used when a piece of equipment does not require full rack width, but may require more than 1U of height. Whereas there is no formal specification for "half rack", the term "half-rack" can have different separate meanings: It can describe equipment that fits in a certain number of rack units, but occupy only half the width of a 19-inch rack (9.5 inches (241.30 mm)).
#4u full size#
Configurations Ī typical full size rack is 42U, which means it holds just over 6 feet (180 cm) of equipment, and a typical "half-height" rack is 18–22U, which is around 3 feet (91 cm) high. The 19-inch rack format with rack-units of 1.75 inches (44.45 mm) was established as a standard by AT&T around 1922 in order to reduce the space required for repeater and termination equipment in a telephone company central office.
Although it is called a 19-inch rack unit, the actual mounting dimensions of a 19-inch rack unit are 18 5⁄ 16 inches (18.3125 in or 465.1 mm) wide, center to center. The mounting-hole distance (as shown to the right) differs for 19-inch racks and 23-inch racks: The 19-inch racks uses uneven spacings (as shown to the right) while the 23-inch racks uses evenly spaced mounting holes.
Manufacturing allows for dimensions with less precision. If n is number of rack units, the ideal formula for panel height is h = (1.75 n − 0.031) for calculating in inches, and h = (44.45 n − 0.794) for calculating in millimetres. To allow space between adjacent rack-mounted components, a panel is 1⁄ 32 inch (0.03125 in or 0.794 mm) less in height than the full number of rack units would imply. While a rack unit is defined as 1 + 3⁄ 4 inches (44.45 mm), a front panel or filler panel in a rack is not an exact multiple of this height. The standard was adopted worldwide as IEC 60297 Mechanical structures for electronic equipment – Dimensions of mechanical structures of the 482.6 mm (19 in) series, and defines the sizes for rack, subrack (a shelf-like chassis in which cards can be inserted), and the pitch of printed circuit boards/cards providing physical compatibility of technological equipment, typically in telecommunications. The Eurocard specifies a standard rack unit as the unit of height it also defines a similar unit, horizontal pitch (HP), used to measure the width of rack-mounted equipment. The rack unit size is based on a standard rack specification as defined in EIA-310.
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