[Q] What is the difference between the TIA/EIA standards 568-A and
568-B?
[A] In order to explain the standard correctly, we must first discuss
a little history that is relevant to this standard.
In
1985, the Computer Communications Industry Association requested
that the Electronic Industries Alliance (EIA) to develop standards
for the cabling used in telecommunications applications.
The
first revision of this standard was released in 1991, but was
later updated again in 1995 due to the massive development of
networking technology and new faster high-speed ethernet cables
and networking components. This was also replaced later with
the current TIA/EIA 568-B standard.
Although
many aspects of networking structure and performance are addressed
in these standards, the most visible and often misunderstood
component is the definition of the wiring assignments in the
RJ45 plug. A colored wire must be placed in a specific pin location
in the plug in order for the cable to meet the standard. It
is these wiring assignments that differ between the T568A and
T568B standard.
The
pins on the RJ45 plug are numbered 1 to 8. If you are holding
a CAT 5 patch cable in your hand, as if inserting into a jack,
with the contacts facing in the up position, pin 1 will be on
the far left. Pin 8 will be the pin on the far right. This is
the orientation we will use when we define the wiring assignments
in the RJ45 plug and making understanding this easy.
CAT
5 Cable has four twisted pairs within the sheath. Each pair
has a specific color code, and is to placed into deliberate
pin location within the RJ45 plug. We will now identify the
wiring locations in each of the standards:
TIA/EIA
568-A (T568A)
Pin 1 - white / green stripe
Pin
2 - green
Pin
3 - white / orange stripe
Pin
4 - blue
Pin
5 - white / blue stripe
pin
6 - orange
pin
7 - white / brown stripe
pin
8 - brown
TIA/EIA
568-B (T568B)
Pin
1 - white / orange stripe
Pin
2 - orange
Pin
3 - white / green stripe
Pin
4 - blue
Pin
5 - white / blue stripe
Pin
6 - green
Pin
7 - white / brown stripe
Pin
8 - brown
If
you are making a patch cable, you will construct the cable using
identical pin assignments on each end. Although it does not
matter which standard you use for this, the 568-B standard is
usually used in the United States.
If
you are making a crossover cable, you will construct the cable
using the 568-A standard on one end, and the 568-B standard
on the other.
Mistakes
are easily made when making crossover cables, so if you do not
have experience with this type of work do not hesitate to get
an experienced installer. It is always best to defer this to
a professional.
It
is vitally important to use the very best material that you
can get in the construction of the cable, and that a top quality
crimper is used as well. Make certain that the cable is checked
using a test meter, to ensure that the wiring sequence is correct
on each end.
Remember,
the 568-B standard is used in virtually every application in
the United States, so make sure you discuss this before starting
your project. In some cases, there may be special reasons to
use the 568-A standard.
Special projects and temporary runs have been made specifying the 568-A standard, to serve as an easily distinguished visual cue for those servicing the network.
Other situations may exist as well that call for this application.
If you have any questions about which standard is most appropriate for your specific installation, refer to a qualified network specialist.
CAT
5 Cable Company provides CAT 5 and CAT 5e patch and crossover cables for all networking applications in
9 colors, and any custom length. Hand assembled and 100% tested
to ensure the finest quality.
RELATED
FAQ QUESTION: What is the difference
between CAT 5 and CAT 5e cable?
Keywords: Cat 5, Cat 5e, Cat 6, Ethernet cable, patch cable, crossover
cable
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