Information Technology Reference
In-Depth Information
TIA Performance Category
It is very important to fully understand the categories of operation of the various
modular jacks. The TIA-568-C standard contains strict performance requirements
for the outlet connectors that are used for Category 3 or 5e or 6/AC6 operation. The
requirements differ somewhat by category, although Category 4 and 5 parameters
are often the same, and thus Category 4 has now been dropped. Although
Categories 1 and 2 exist, they are not the subject of the standards because they really
are not appropriate for any type of LAN cabling.
Components, as well as cable, should be marked as certified for a particular
category of use. Thus, a connector that is intended for Category 5e use should be
marked for Category 5e, as explained below. However, you may have occasion to
need to determine the appropriate use of an unmarked jack. While it may not be
possible to categorize an unmarked jack without some uncertainty, there are some
guidelines that can help out. If you can identify the jack assembly style, you should
be able to determine its probable category of rating. The jack styles and their appro-
priate categories for use are shown here:
TIA performance category Termination style
1-3 Screw terminal or IDC
4 IDC, including 66- and 110-type
5e IDC using PC board, only*
6/AC6/7 IDC using PC board, offset pins*
7 nonmodular IDC, crimp, or solder flow
*Category 5e/6 jacks can also use 110, BIX, and Krone type connections.
Of course, any jack that is rated for a higher category than the intended use
can be substituted. For example, it is perfectly acceptable to use a Category 6 or 5e
jack for a Category 5e installation. However, you could possibly upgrade the entire
wiring system for very little more cost. The IDC jacks are so easy to use, they are
often used even when their higher category of operation is not required.
Keyed-Plug Entry
Some modular jacks have an extra slot at the side to supposedly limit connections
to cable plugs with a matching slot. These side-keyed jacks are largely useless
because they easily accommodate a nonkeyed plug.
The original intent was to protect delicate digital equipment from the higher
voltages that can sometimes be present on telephone circuits. For example, the com-
mon open circuit voltage for a telephone line in the United States is -48 DC, and the
