SRS-What is a 19" Subrack?

A 19-inch rack is a standardized (EIA 310-D, IEC 60297 and DIN 41494 SC48D) system for mounting various electronic modules in a "stack", or rack, 19 inches (480 mm) wide. Equipment designed to be placed in a rack is typically described as rack-mount, a rack mounted system, a rack mount chassis, subrack, rack mountable, or occasionally, simply shelf. The slang expression for a subrack (generally 1U = 1.75 in = 44.45 mm height) is "pizza box" due to the similarity in size and shape, see also pizza box form factor. Most racks are sold in the 42U form: that is, a single rack capable of holding 42 1U pizza box servers, or any combination of 1U, 2U, 3U or other height units.