Information Technology Reference
In-Depth Information
User cords are a required part of the Channel, the total end-to-end LAN con-
nection, but they are not part of the Basic Link or Permanent Link, both of which
exclude user cords. These terms are defined in TIA-568-C.1, Sec. 11, “Cabling
Transmission Performance and Test Requirements,” and they are very useful in
describing the component parts of a cable link. The theory is that a cable plant could
be installed and tested before any of the user network hardware is installed. To do
the testing, we need to have performance specifications for the portion of the hori-
zontal cabling that excludes the user cables. That portion is called the Basic Link or
Permanent Link. However, channel performance levels are also defined, so we could
also test with the user cables in place. In fact, that type of test is the ultimate assur-
ance that a link meets the requirements for a particular category of operation. More
information on Channel and Permanent Link is included in Chapters 1 and 15.
Construction
User cords are flexible, 4-pair cables, terminated at either end in an 8-pin (IEC 603-
7) modular plug. The cords may be provided in various lengths, as needed for the
application. The cords should meet the transmission and construction requirements
for patch cords in TIA-568-C, as user cords are not explicitly defined elsewhere in
that standard. The color code for the conductors and the wiring pattern connections
for the modular plug are the standard configuration, as shown in the first part of
this chapter, as well as in Chapters 2 and 5. Either the T568A or B pattern may be
used, as long as the same pattern is used at both ends of the cord. The standard also
allows an alternative color pattern consisting of eight solid colors that can be used
for user cords.
User cords are made from AWG 24, stranded, thermoplastic insulated conduc-
tors, arranged into four pairs, with an outer thermoplastic jacket (Fig. 9.6).
Conductors of 22-gauge wire may be used, if the cord meets the same performance
requirements, but you must be certain that the connector plugs are designed for the
larger wire size. The various jacketing materials are described in Chapter 5.
Stranded wire is used because of its flexibility.
From a technical standpoint, solid wire could be used, but it lacks flexibility
and is more difficult to connect with modular plugs. In most locations, nonplenum
insulation, such as PVC, is acceptable. PVC is also much more flexible than most
plenum-rated plastics and it is more easily tinted.
The outer jacket color should be appropriate for the office environment.
Some of the cable manufacturers offer Category 5e cable in a bright color, to
distinguish it from lower category wire. There is no need to use this bright color in
the work areas. The cable should be marked to indicate the category if there is any
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