Information Technology Reference
In-Depth Information
niques can range from 15 MHz (per pair) to 33 MHz because of encoding of the
data. If a certain multi-pair encoding is used for 100 Mbps Ethernet (100BaseT4), it
can actually run on older Category 3 cable, which is rated to 16 MHz.
However, current-day installations should be at Category 5e or above, and can
easily accommodate 1000 Mbps data rates, and lower, including 155, 100, 50, 25,
16, and 10 Mbps. Category 6 extends operating frequencies to 200 MHz (tested to
250 MHz) and increases operating margins at lower speeds. Components, such as
jacks and patch panels, are also rated by category of performance. Augmented
Category 6 (AC6) has a testing frequency of up to 625 MHz, and operation to 500
MHz. Augmented Category 6 corresponds to ISO/IEC 11801 Class E-Augmented.
Category 7, the newest of the standards categories, is undergoing considerable
development, but will be able to support bandwidths up to 1200 MHz. It is roughly
equivalent to ISO/IEC 11801 Class F.
TIA-568 Connector Standards
Standard 8-pin (RJ-45 style) modular connectors are used for the TIA-568-C (nontradi-
tional connectors are added for Category 7 support, as will be covered later). Four-pair,
24 AWG, UTP provides the station cable. All eight wires are connected to the jack. A
system of optional punchdown termination blocks and patch panels completes the con-
nection system. Wiring connection is
straight through
, which means simply that Pin 1 at
one end of a cable will correspond to pin 1 at the other end. This is true whether we are
talking about a user cord, a patch cord, or the in-wall station cable. This is a departure
from normal 6-wire telephone cords, which reverse the connections from end to end.
The TIA-568-C system allows two different color-coded wiring patterns for the
specified 8-pin modular connectors. Figure 3.1 shows the two patterns, called
T568A and T568B (not to be confused with the “A” or “B” revisions of the origi-
nal standard). The two wiring patterns are electrically equivalent, but the positions
of Pair 2 and Pair 3 are reversed.
Practically, this means that the color-to-pin correspondence varies between the
two wiring standards, and it makes little difference which you use, as long as both
ends of the cable are pinned the same. In other words, if you use the T568A pattern
at the workstation outlet (called the telecommunications outlet in the standard), you
must also use a matching T568A patch panel or fan-out cable in the telecommuni-
cations room. Pairs 2 and 3 just happen to be the two pairs used by 10/100BaseT
Ethernet, so ignoring this wiring convention will cause the connection to fail.
Token-Ring and 4-wire communications circuits, including T1, will also have a fail-
ure. Many prewired components are not marked as to wiring pattern, particularly
nonrated octopus fan-out cables, so be aware of what you install.
