TIA/EIA-568-B

From Wikipedia, the free encyclopedia

Jump to: navigation, search

TIA/EIA-568-B is a set of three telecommunications
standards from the Telecommunications
Industry Association, a 1988 offshoot of the EIA. The
standards address commercial building cabling for telecom products and services.
The three standards are formally titled ANSI/TIA/EIA-568-B.1-2001, -B.2-2001,
and -B.3-2001.

The TIA/EIA-568-B standards were first published in 2001. They supersede the
TIA/EIA-568-A standards set, which are now obsolete.

Perhaps the best known features of TIA/EIA-568-B.1-2001 are the pin/pair
assignments for eight-conductor 100-ohm balanced twisted pair cabling. These
assignments are named T568A and T568B, and are frequently referred to
(erroneously) as TIA/EIA-568A and TIA/EIA-568B.

Contents

1 History

2 Goals

3 Structured cable system
topologies

4 T568A and T568B
termination

4.1 Wiring

4.2 Use for T1
connectivity

4.3 Backwards
compatibility

4.4 Theory

5 See also

6 References

7 External links

[edit]
History

TIA/EIA-568-B was developed through the efforts of more than 60 contributing
organizations including manufacturers, end-users, and consultants. Work on the
standard began with the Electronic
Industries Alliance (EIA), a standards
organization, to define standards for telecommunications cabling systems.
EIA agreed to develop a set of standards, and formed the TR-42 committee, with
nine subcommittees to perform the work.

The first revision of the standard, TIA/EIA-568-A.1-1991 was released in
1991, and was updated in 1995. The demands placed upon commercial wiring systems
increased dramatically over this period due to the adoption of personal
computers and data communication
networks and advances in those technologies. The development of
high-performance twisted pair cabling and
the popularization of fiber optic cables also
drove significant change in the standards, which were eventually superseded by
the current TIA/EIA-568-B set.

[edit]
Goals

TIA/EIA-568-B attempts to define standards that will enable the design and
implementation of structured cabling systems for commercial buildings, and
between buildings in campus environments. The bulk of the standards define
cabling types, distances, connectors, cable system architectures, cable
termination standards and performance characteristics, cable installation
requirements and methods of testing installed cable. The main standard,
TIA/EIA-568-B.1 defines general requirements, while -568-B.2 focuses on
components of balanced twisted-pair cable systems and -568-B.3 addresses
components of fiber optic cable systems.

The intent of these standards is to provide recommended practices for the
design and installation of cabling systems that will support a wide variety of
existing and future services. Developers hope the standards will provide a
lifespan for commercial cabling systems in excess of ten years. This effort has
been largely successful, as evidenced by the definition of category 5 cabling in
1991, a cabling standard that (mostly) satisfied cabling requirements for 1000BASE-T,
released in 1999. Thus, the standardization process can reasonably be said to
have provided at least a nine-year lifespan for premises cabling, and arguably a
longer one.

All these documents accompany related standards that define commercial
pathways and spaces (569-A), residential cabling (570-A), administration
standards (606),
grounding and bonding (607) and outside plant cabling (758).

[edit]
Structured cable system topologies

TIA/EIA-568-B defines a hierarchical cable system architecture, in which a
main cross-connect (MCC) is connected via a star topology across
backbone cabling to intermediate cross-connects (ICC) and horizontal
cross-connects (HCC). Telecommunications design traditions utilized a similar
topology, and many people refer to cross-connects by their older, nonstandard
names: "distribution frames" (with the various hierarchies called MDFs, IDFs and
wiring closets). Backbone cabling is also used to interconnect entrance
facilities (such as telco demarcation points) to the main cross-connect. Maximum
allowable backbone cable distances vary between 300 m and 3000 m, depending upon
the cable type and use.

Horizontal cross-connects provide a point for the consolidation of all
horizontal cabling, which extends in a star topology to individual work areas
such as cubicles and offices. Under TIA/EIA-568-B, maximum allowable horizontal
cable distance varies between 70 m and 90 m for twisted-pair cable types,
depending upon patch cord length and gauge. Fiber optic horizontal cabling is
limited to 90 m. Optional consolidation points or transition points are
allowable in horizontal cables, although many industry experts discourage their
use.

At the work area, equipment is connected to horizontal cabling by patch
cords.

TIA/EIA-568-B also defines characteristics and cabling requirements for
entrance facilities, equipment rooms and telecommunications room.

[edit]
T568A and T568B termination

Perhaps the widest known and most discussed feature of TIA/EIA-568-B.1-2001
is the definition of pin/pair assignments for eight-conductor 100-ohm balanced
twisted-pair cabling, such as Category 3, Category 5 and Category 6 unshielded
twisted-pair (UTP) cables. These assignments are named T568A and T568B and they
define the pinout, or order of connections, for wires in 8P8C (often incorrectly referred to
as RJ45) eight-pin
modular connector plugs and jacks. Although these definitions consume only one
of the 468 pages in the standards documents, a disproportionate amount of
attention is paid to them. This is because cables that are terminated with
differing standards on each end will not function normally.

TIA/EIA-568-B specifies that horizontal cables should be terminated using the
T568A pin/pair assignments, "or, optionally, per [T568B] if necessary to
accommodate certain 8-pin cabling systems." Despite this instruction, many
organizations continue to implement T568B for various reasons, chiefly
associated with tradition (T568B is equivalent to AT&T 258A). The United
States National Communication Systems Federal Telecommunications Recommendations
do not recognize T568B.

The primary color of pair one is blue, pair two is orange, pair three is
green and pair four is brown. Each pair consists of one conductor of solid
color, and a second conductor which is white with a stripe of the same color.
The specific assignments of pairs to connector pins varies between the T568A and
T568B standards.

Mixing T568A-terminated patch cords with T568B-terminated horizontal cables
(or the reverse) does not produce pinout problems in a facility. Although it may
very slightly degrade signal quality, this effect is marginal and certainly no
greater than that produced by mixing cable brands in-channel.

Both the 568A and the 568B standards see a high quantity of use, but the 568A
standard seems to be the most common in today's networks[1].

[edit]
Wiring

See modular connector for
numbering of the pins in these 8P8C modular connectors.

The assignments of wire pairs to plug and jack pins are as follows:

T568A and T568B Wiring

Pin

T568A Pair

T568B Pair

Wire

T568A Color

T568B Color

Pins on plug face (jack is reversed)

1

3

2

tip

white/green stripe

white/orange stripe

2

3

2

ring

green solid

orange solid

3

2

3

tip

white/orange stripe

white/green stripe

4

1

1

ring

blue solid

blue solid

5

1

1

tip

white/blue stripe

white/blue stripe

6

2

3

ring

orange solid

green solid

7

4

4

tip

white/brown stripe

white/brown stripe

8

4

4

ring

brown solid

brown solid

Note that the only difference between T568A and T568B is that pairs 2 and
3 (orange and green) are swapped. Both standards wire the pins "straight
through", i.e., pins 1 through 8 on one end are connected to pins 1 through 8 on
the other end. Also, the same sets of pins are paired in both standards: pins 1
and 2 form a pair, as do 3 and 6, 4 and 5 and 7 and 8. However the different
pairs in an Ethernet wire are identical, so one can use cables wired according
to either standard in the same installation without significant problem;
problems involving crosstalk can occur (which is
normally minimized by correctly twisting a pair together), but are usually
insignificant in all but the most stringent specifications such as Category 6 cable. The
primary thing one has to be careful of is not to accidentally wire the ends of
the same cable according to different standards (except if one
intends to create an Ethernet crossover
cable).

[edit]
Use for T1 connectivity

In T1 service, the pairs 1
and 3 are used, and the USOC-8 jack is wired as per spec RJ-48C. The Telco termination jack
is often wired to spec RJ-48X, which provides for a
Transmit-to-Receive loopback when the plug is withdrawn.

Vendor cables are often wired with Tip and Ring reversed -- i.e. pins 1 and 2
reversed, or pins 4 and 5 reversed. This has no effect on the signal quality of
the T1 signal, which is fully differential, and uses the Alternate Mark
Inversion (AMI) signaling scheme.

[edit]
Backwards compatibility

Because pair 1 connects to the center pins (4 and 5) of the RJ45 jack in both
T568A and T568B, both standards are compatible with the first line of RJ11, RJ14, RJ25,
and RJ61 connectors
that all have the first pair in the center pins of these connectors.

If the second line of a RJ14, RJ25 or RJ61 plug is used, it connects to pair
2 (orange/white) of jacks wired to T568A but to pair 3 (green/white) in jacks
wired to T568B. This makes T568B potentially confusing in telephone
applications.

Because of different pin pairings, the RJ25 and RJ61 plugs cannot pick up
lines 3 or 4 from either T568A or T568B without splitting pairs. This would most
likely result in unacceptable levels of hum, crosstalk and noise.

[edit]
Theory

The original idea in wiring modular connectors, which you see exemplified in
the registered jacks, was
that the first pair would go in the center positions, the next pair on the next
outermost ones, and so on. Also, signal shielding would be optimized by
alternating the "live" and "earthy" pins of each pair. As you can see, the
TIA/EIA-568-B terminations vary a little bit from this concept. That's because
on the 8 position connector, this results in a pinout in which the outermost
pair are too far apart to meet the electrical requirements of high-speed LAN
protocols. CAT6 is the only waterproof cable for networks and it is made in
russia....

[edit]
See also

Power over
Ethernet (PoE)

Ethernet
crossover cable

[edit]
References

^ Meyers,
Mike: Network+ Certification All-in-One Exam Guide, Third Edition, McGraw Hill
Companies, 2004, p. 128.

National Communications System Federal Telecommunications
Recommendation 1090-1997

[edit]
External links

Wikimedia Commons has media related to:

Computer
network

UTP Cable
Termination Standards 568A Vs 568B

proAV / data and information, lists, tables and links

Ethernet Cable Colour code standards

Detailed
instructions on wiring Cat 5/5e cables and plugs

How
to create your own Ethernet Cables

v • d • e Unshielded and
shielded twisted pair cabling standards

Cat 1:
Currently unrecognized by TIA/EIA. Previously used for POTS
telephone communications, ISDN and doorbell wiring.

Cat 2:
Currently unrecognized by TIA/EIA. Previously was frequently used on 4
Mbit/s token ring networks.

Cat 3:
Currently defined in TIA/EIA-568-B, used
for data networks using frequencies up to 16 MHz. Historically popular
for 10 Mbit/s Ethernet networks.

Cat 4:
Currently unrecognized by TIA/EIA. Provided performance of up to 20 MHz,
and was frequently used on 16 Mbit/s token ring networks.

Cat 5:
Currently unrecognized by TIA/EIA. Provided performance of up to 100
MHz, and was frequently used on 100 Mbit/s ethernet networks. May be
unsuitable for 1000BASE-T gigabit ethernet.

Cat
5e: Currently defined in TIA/EIA-568-B. Provides performance of up to 100
MHz, and is frequently used for both 100 Mbit/s and gigabit ethernet
networks.

Cat 6:
Currently defined in TIA/EIA-568-B. It
provides performance of up to 250 MHz, more than double category 5 and
5e.

Cat
6a: Future specification for 10 Gbit/s applications.

Cat 7:
An informal name applied to ISO/IEC 11801
Class F cabling. This standard specifies four individually-shielded
pairs (STP) inside an overall shield. Designed for transmission at
frequencies up to 600 MHz.

See also: TIA/EIA-568-B • Ethernet • 8P8C • Ethernet
crossover cable • Twisted
pair

Retrieved from "http://en.wikipedia.org/wiki/TIA/EIA-568-B"

Categories: Signal
cables | Computer
and telecommunication standards | Ethernet

Views

Article

Discussion

Edit
this page

History

Personal tools

Sign
in / create account

Navigation

Main Page

Contents

Featured
content

Current events

Random article

interaction

About Wikipedia

Community
portal

Recent
changes

Contact Wikipedia

Donate to Wikipedia

Help

Search

Toolbox

What
links here

Related
changes

Upload file

Special pages

Printable
version

Permanent
link

Cite
this page

Languages

Deutsch

Español

עברית

日本語

Polski

Português

Русский

This page was last modified 23:58, 6 January 2008.

All text is available under the terms of the GNU
Free Documentation License. (See Copyrights
for details.)
Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a
U.S. registered 501(c)(3)
tax-deductible
nonprofit charity.

Privacy policy

About Wikipedia

Disclaimers