Owner manual

Marking the Rack

You must allow 2 U (88 mm or 3.5 inches) of vertical space for each system you install in the

two-post rack.

Universal-Hole Spacing Racks

Industry-standard two-post racks with universal-hole spacing have an alternating pattern of

three holes per U with center-to-center hole spacing (beginning at the top hole of a 1-U

space) of 15.9 mm, 15.9 mm, and 12.7 mm (0.625 inch, 0.625 inch, and 0.5 inch) for the

front and back vertical column of holes (see

Figure 1-13).

Figure 1-13. Two-Post, Open-Frame Relay Rack Universal-Hole Spacing

44 mm 1.75 inches (1 U)

i k

15.9 mm (0.625 inch)

12.7 mm (0.5 inch)

15.9 mm (0.625 inch)

Wide-Hole Spacing Racks

Some two-post racks with wide-hole spacing have an alternating pattern of two holes per U

with center-to-center hole spacing (beginning at the top hole of a 1-U space) of 31.7 mm

and 12.7 mm (1.25 inches and 0.5 inch) for the front and back vertical column of holes (see

Figure 1-14).

1-20 I Rack Installation Guide