Information Technology Reference
In-Depth Information
(such as an elevator or other larger motor), and metal beams or metal walls. In gen-
eral, the electrical wiring and metal items may be crossed (preferably at right
angles), but not run alongside. Many authorities suggest that a 2-ft separation be
maintained from these sources.
EIA/TIA-569 provided specific guidelines, but these were dropped in TIA/EIA-
569-A.
Station wire must be of a category that conforms to applicable performance
standards. Obviously, a Category 5e installation requires Category 5e certified
cable. However, a Category 3 installation could actually use Category 5e or 6 certi-
fied cable, since either would exceed the requirement.
In some cases, existing telephone station wire may be able to perform at the
lower data rates of Category 3, which can be verified through testing. If the wire
was installed after about 1984, it probably has enough twists per foot to approxi-
mate current Category 3 standards.
Prior to that time, telephone twisted-pair cable was sometimes manufactured
with less than two twists per foot, unless it was made to meet more stringent AT&T
premises distribution standards. A cable scanner that measures impedance and near-
end crosstalk (NEXT) should give you an indication whether such cable will work
adequately. You should be aware that none of the current TIA/EIA standards
encourage you to “steal” pairs from an existing telephone station cable, but you
may be able to retrofit an existing installation if absolutely necessary.
Station wire must also have an insulation type that meets safety and fire pro-
tection standards. Fire protection and safety standards are specified by Underwriters
Laboratories (UL), the National Fire Protection Association's (NFPA's) National
Electrical Code
®
(NEC
®
), Canadian Standards Association (CSA), International
Standards Organization (ISO), and various European Community (EC) and individ-
ual country standards in other parts of the world. These standards are meant to
FIGURE 1.5
Horizontal structure components.
