Information Technology Reference
In-Depth Information
Modern Patch-Panel Termination
With the second alternative, patch panels, the horizontal cables are directly terminated
into modular patch panels (unless you use a hybrid method of termination, described
later). Patch cords are connected between the patch panel jacks and the equipment hubs
(or between horizontal and backbone cables), and connections may be reconfigured at
will. This method is very convenient for smaller installations that use hubs (or other
equipment) with discrete modular jacks. You must use some sort of modular connec-
tion to these hubs, and the patch allows the use of individual modular cords, and avoids
the use of multipair fan-out cables and connectorized punchdown blocks. It is also
handy for companies that frequently move connections or add stations to the network.
Patch panel termination has several advantages for a high-performance Category
5e/6/AC6 system. Permanent link and channel testing (Chapter 15) are easier, because
you have the cable terminated in an approved outlet connector. In contrast, a channel
test cannot be performed on a punchdown system until the final cross-connects are
made. If the cross-connect has too much untwist, or if the jumper is later distorted in
some way, the link may fail later in the life of the channel. Patch connections are solid
and reproducible, and it is virtually impossible to diminish link performance, once the
initial termination has passed muster. And, future moves/adds/changes can be made by
virtually anyone, with no need for a trained cabling technician.
Testing a patch panel installation is very easy. You simply disconnect a patch
cord and connect your tester. The patch jacks are also more spread out than the
cable termination areas on cross-connects, and this may make it easier to provide
proper circuit marking. (If you have ever tried to mark on the little tabs of a 66
block, you can appreciate this a lot.) Newer designs for patch panel terminations use
IDC connections that are similar to those on traditional connecting blocks or outlet
jacks. These designs help preserve the pair twist on terminated cables and use inter-
nal jack wiring that is designed to meet the new categories of performance.
Direct patch panel termination of station cables, however, limits the flexibility
of a terminated cable, because the station cable pairs are available only on the cor-
responding patch jack. To gain access to unused cable pairs, an external adapter or
splitter must be used. Because of this limitation and other factors, there are differ-
ing opinions on whether you should use patch panels or cross-connect fields.
Pros and Cons of Patches and Cross-Connects
Obviously, there are valid arguments on each side of this question. On the one hand,
when you terminate your horizontal cables directly onto a patch panel, you avoid
the muss and fuss of at least three terminations (the horizontal punchdown and the
