Information Technology Reference
In-Depth Information
multiple-of-12 convention. For example, a group of twelve 4-pair circuits can be
accommodated by both sides of a 66 block (50 pairs), whereas a group of twenty-
four 4-pair circuits can be accommodated by a 100-pair 110 wiring block.
Additionally, the number 24 is convenient to use, because a row of 24 modular jacks
fits nicely across a 19-in panel width.
The connectors on a LAN patch panel are standard 8-pin modular jacks, wired
either to T568A or B. The connections for station cables at the rear of the panel are
usually color coded by pair number, which corresponds to the wiring pattern at the
jack. It is possible to use other wiring patterns for special applications, but that isn't
covered here. The connectors are spaced according to the manufacturer's preference,
and you may find individually spaced connectors or connectors that are placed in
groups of four or six adjacent jacks. The connectors are usually numbered accord-
ing to their position on the panel. Optional circuit marking is described later in this
section.
If you still have questions on whether to use the T568A or the T568B wiring
pattern, see the discussion in Chapter 6 under “Standard Jack Pinouts.” For station
cable wiring, it basically doesn't matter which you use, as long as the outlet jacks
use the same pattern. Patch panels that use color-coded wire terminations are
prewired to support either the T568A or the T568B pattern, so make certain which
you order. You could use the opposite pattern for your needs, but you would have
to reverse the orange and green pair (pairs 2 and 3) and be forever confused when
it came time to add new cables.
Standard patch panels will generally use some type of insulation-displacement
connection (IDC) at the rear of the panel to terminate station cables (or other cables,
such as those from nonmodular hubs and other equipment). The two basic design
variations for patch panels either use groups of connectors that have a common ter-
mination block, or use individual connectors that have their own terminations at the
rear of each connector. Another type of panel uses multicircuit connectors and is
described in the next section.
The terminations for patch panels (Fig. 8.3) are identical in function (and often
in appearance) to the terminations used in workstation outlet jacks or in connecting
blocks. Variations in panels are available that use individual IDC connections, 110C
blocks, 66 blocks, BIX blocks, and Krone blocks. Each method has the advantages
and disadvantages that were described in Chapters 7 and 8, and you should choose
according to your preferences. It should be pointed out that the use of standard 66
blocks is not generally recommended for LAN wiring, particularly above Category
3. The use of newer Category 5e-rated 66 blocks is still somewhat controversial, but
if the manufacturer has UL-verified performance, you can probably use the blocks
in this application.
