The industry-standard rack cabinet is 42U tall; however, 45U racks are also common. The term relay rack appeared first in the world of telephony. By 1911, the term was also being used in railroad signaling.
The earliest repeaters from 1914 were installed in ad hoc fashion on shelves, in wooden boxes and cabinets.
There is little evidence that the dimensions of these early racks were standardized. The 19-inch rack format with rack-units of 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.
in all cases to be a whole multiple of 1 inches". By 1934, it was an established standard with holes tapped for 12-24 screws with alternating spacings of and The EIA standard was revised again in 1992 to comply with the 1988 public law 100-418, setting the standard U as + + , making each "U" . The 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably and the set of fields to which racks are applied has greatly expanded.
in all cases to be a whole multiple of 1 inches". By 1934, it was an established standard with holes tapped for 12-24 screws with alternating spacings of and The EIA standard was revised again in 1992 to comply with the 1988 public law 100-418, setting the standard U as + + , making each "U" . The 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably and the set of fields to which racks are applied has greatly expanded.
in all cases to be a whole multiple of 1 inches". By 1934, it was an established standard with holes tapped for 12-24 screws with alternating spacings of and The EIA standard was revised again in 1992 to comply with the 1988 public law 100-418, setting the standard U as + + , making each "U" . The 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably and the set of fields to which racks are applied has greatly expanded.
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Page generated on 2021-08-05