Category 5 cable
Category 5 cable,
commonly known as Cat 5, is an
unshielded twisted pair type cable designed for high signal integrity. The
actual standard defines specific electrical properties of the wire, but it is
most commonly known as being rated for its Ethernet capability of 100 Mbit/s.
Its specific standard designation is EIA/TIA-568. Cat 5 cable typically has
three twists per inch of each twisted pair of 24 gauge copper wires within the
cable. Another important characteristic is that the wires are insulated with a
plastic (FEP) that has low dispersion, that is, the dielectric constant of the
plastic does not depend greatly on frequency. Special attention also has to be
paid to minimizing impedance mismatches at connection points.
It is often used in structured
cabling for computer networks such as fast Ethernet, although it is often used
to carry many other signals such as basic voice services, token ring, and ATM
(at up to 155 Mbits/s, over short distances).
The other well known flavour of
this type of cable is the 10 Mbit/s Category 3 cable. Less well known is the 20
Mbit/s Cat 4. Cat 4 offered only a small advance in speed over Cat3, and was
generally ignored in favour of Cat 5. Cat 1 and Cat 2 are 1 Mbit/s systems for
voice and low-speed data.
Patch leads created from Cat 5
are often terminated with RJ-45 electrical connectors. Normal Cat 5 cables are
wired "straight through" and connect a computer to a hub. In other
words, pin 1 is connected to pin 1, pin 2 to pin 2, etc. The RJ-45 pinout for a
Cat 5 cable can either be TIA-568A or TIA-568B. TIA-568A is used by some phone
systems and Token Ring. Most everything else, such as the Ethernet standards
10BASE-T and 100BASE-TX, use TIA-568B.
In Ethernet,
"crossover" Cat-5 cables are used to connect two hubs together, in
which pairs two and three are reversed. Crossover cables can also be used to
connect two PC's NICs directly (with no intervening hub). See the TIA-568B
article for a pinout diagram.
Cat 5e cable
is an enhanced version of Cat 5 for use with 1000 Base-T networks, or for
long-distance 100 Base-T links (350 m, compared with 100 m for Cat5). It must
meet the EIA/TIA 568A-5 specification.
Cat 6 cable
is defined by the ANSI TIA/EIA 568B-2.1. It is suitable for 1000 Base-T
(gigabit) Ethernet up to 100 m.
Cat 7 cable,
with four individually-shielded pairs (ScTP) inside an overall shield, has been
proposed but is not in common use. It is designed for transmission frequencies
up to 600MHz, which should enable it to carry 10-Gigabit Ethernet (10GBaseT),
but requires a redesigned RJ-45 connector (called a GG45) to achieve this speed.
10GBaseT networks are not yet widely available, and may not be able to compete
with fibre optic networks.
The Anatomy of CAT5 Cable
What CAT5 Cable is
CAT5, which
is short for Category 5 and indicates the fifth generation, is a standard for
twisted pair Ethernet cable as defined by the EIA/TIA (Electronic Industries
Association and Telecommunications Industry Association).
CAT5 is the most common cabling system used for networks
today. CAT5 cable runs are limited to a maximum recommended length of 100m (328
feet).
How CAT5 Cable Works
CAT5 cables contain eight wires--usually 24-gauge copper.
The wires are divided into four pairs and each pair is twisted together, thus
the moniker “twisted pair.”
Pair 1:
White/Blue - Blue
Pair 2:
White/Orange - Orange
Pair 3:
White/Green - Green
Pair 4:
White/Brown - Brown
Fast
Ethernet (100 Mbps) communications utilize two pairs--Pair 2 and Pair 3 are
used while Pair 1 and Pair 4 are not.
CAT5 cable pairs are twisted together to promote signal
balance. Both wires in a pair carry the same information and the
electromagnetic fields generated by the individual wires cancel each other out
by virtue of being twisted together. Thus, each balanced pair poses less risk
of interference with the other pairs. Because each pair carries two copies of
the same information, less power is required to send the signal, further
reducing electromagnetic interference.
CAT5 cables have more twists per inch than earlier CAT
cable versions allowing CAT5 cable to run at higher speeds and span greater
lengths.
CAT5 cables are terminated by RJ45 connectors. There are
two standards for wiring RJ45 plugs and jacks—EIA/TIA T568A and T568B.
These standards dictate the color code pattern used to connect the cable wires
to the RJ45 plugs and jacks. Most pre-made patch cables use T568B.
CAT5 Cable Type
Unshielded Twisted Pair (UTP) is the most common and is simply
made up of the twisted pairs enclosed in the vinyl jacket.
Shielded Twisted Pair (STP) is a bit more expensive and the
twisted pairs are encased an insulating wrapper and then enclosed in the vinyl
jacket. The insulating wrapper is designed to protect the signal from
electromagnetic interference leaking into or out of the cable.
How to make a CAT5 Cable.
A good CAT5
termination Provides a proper wire crimp, a wire insulation strain relief crimp
and a cable strain relief crimp. Also important, is not unwinding the wires
more than necessary, maintaining the twists as far as possible is important,
but don't let it stop you from inserting the wires as far as possible. I've
made a lot of these cables personally, and this is how I do it.
*Strip the cables Jacket back one full inch.
*Strip the cables Jacket back one full inch.
*Untwist the wires back to within 1/8" of the jacket.
*Arrange the wires in the order in which you want to crimp them, (ie. 568A, 568B, etc.).
*Grasp the wires firmly, between your thumb and forefinger, flatten them, and even wiggle them a bit, to take out the curliness, (concentrate your efforts on the bottom 1/2") the wires must lay flat and together, aligned as close as possible.
*While holding the wires firmly, cut off the the wires 1/2" from the cables jacket (Cut the wires with some sharp wire strippers or even high quality scissors, avoid wire cutters that flatten the ends of the wires insulating material, this makes stuffing the wires very difficult.)
* Stuff the wires into the connector, making sure the wires stay lined up. * The wires should reach the end of the little tube they are in, if possible, or at least past the farthest point of that "little funny Gold Plated thingy"above it, which will terminate it.
* The jacket should go even with the end of the first indent, if possible, it's a strain relief for the cable.
*Insert it into the crimping tool, and Crimp it! All of this is very dependant on the tools you are using, the connectors you are using, and the cable you are using. A bad combination can be hell!
How to wire a CAT5 (EIA 568-B*) Cable.
connector #1
|
connector #2
|
1 WHT/ORG
2 ORG/WHT 3 WHT/GRN 4 BLU/WHT 5 WHT/BLU 6 GRN/WHT 7 WHT/BRN 8 BRN/WHT |
1 WHT/ORG
2 ORG/WHT 3 WHT/GRN 4 BLU/WHT 5 WHT/BLU 6 GRN/WHT 7 WHT/BRN 8 BRN/WHT |
How to wire a CAT5 (EIA 568-A*) Cable.
connector #1
|
connector #2
|
1 WHT/GRN
2 GRN/WHT 3 WHT/ORG 4 BLU/WHT 5 WHT/BLU 6 ORG/WHT 7 WHT/BRN 8 BRN/WHT |
1 WHT/GRN
2 GRN/WHT 3 WHT/ORG 4 BLU/WHT 5 WHT/BLU 6 ORG/WHT 7 WHT/BRN 8 BRN/WHT |
*The only real difference between 568A
and 568B is that
the White/Orange-Orange/White and White/Green-Green/White pairs are swapped.
the White/Orange-Orange/White and White/Green-Green/White pairs are swapped.
How to wire a
"Crossover" Cable.
(EIA 568-B*)
(EIA 568-B*)
connector #1
|
connector #2
|
1 WHT/ORG
2 ORG/WHT 3 WHT/GRN 4 BLU/WHT 5 WHT/BLU 6 GRN/WHT 7 WHT/BRN 8 BRN/WHT |
1 WHT/GRN
2 GRN/WHT 3 WHT/ORG 4 BLU/WHT 5 WHT/BLU 6 ORG/WHT 7 BRN/WHT 8 WHT/BRN |
USOC crossover cables are like this:
1 WHT/BRN
2 WHT/GRN 3 WHT/ORG 4 WHT/BLU 5 BLU/WHT 6 ORG/WHT 7 GRN/WHT 8 BRN/WHT |
8 WHT/BRN
7 WHT/GRN 6 WHT/ORG 5 WHT/BLU 4 BLU/WHT 3 ORG/WHT 2 GRN/WHT 1 BRN/WHT |
color abbreviations:
WHT-WHITE
BRN-BROWN
ORG-ORANGE
GRN-GREEN
BLU-BLUE
WHT-WHITE
BRN-BROWN
ORG-ORANGE
GRN-GREEN
BLU-BLUE
The first color listed in the color
pair is the dominant color of the wire.
In other words, WHT/ORG is a white wire with orange stripes.
In other words, WHT/ORG is a white wire with orange stripes.
RJ45 Ends:
The RJ45 end is a
8-position modular connector that looks like a large phone plug. There are a
couple variations available. The primary variation you need to pay attention to
is whether the connector is intended for braided or solid wire. For
braided/stranded wires, the connector has contacts that actually pierce the
wire. For solid wires, the connector has fingers which pierce the insulation
and make contact with the wire by grasping it from both sides. The connector is
the weak point in an ethernet cable, choosing the wrong one will often cause
grief later. If you just walk into a computer store, it's pretty impossible to
tell what type of connector it is, if it isn't specifically labelled. Strain
relief boots are somewhat helpful sometimes. Here is a diagram and pinout:
Cut a piece of Cat 5 as long as you need. When you
cut, remember the old saying: Measure twice, cut once. Make sure the cut on
each end is clean and straight.
Strip about an inch of the insulation off the
cable. Cut it back nice and square. Some crimping tools such as the one used in
this article come with a built-in wire stripper. You put the cable in to a stop
on one side of the cutter. It will cut the jacket the right length to make a
perfect crimp. It is extremely important that you only cut the plastic
insulation/jacket and not the wire. Damaging one of the 8 wires, even if you
just nick it or partially cut it, will ruin your cable.
Untwist the wires. You'll notice that there are 4
pairs of multi-colored wires inside. Sort the pairs by color. You should end up
with wires color coded as follows: blue/blue-white, orange/orange-white,
green/green-white, brown/brown-white.
Note: Some Cat 5 cable skimps on the color-coding
and you will have to keep the track of which wire was wrapped around which. If
at all possible, check the cable before you buy and make sure the color-coding
is easy to recognize. If not, you'll be cursing up a storm later and wish you
would have spent the extra 5 bucks on the better cable.
Now align the wires in the following order from
left to right. The order is important since there is a wiring standard defined
by the Telecommunications Industry Association (TIA).
It's called the EIA/TIA-568 Commercial Building Telecommunications Wiring
Standard.
W
H I T E O R A N G E |
O
R A N G E |
W
H I T E G R E E N |
B
L U E |
W
H I T E B L U E |
G
R E E N |
W
H I T E B R O W N |
B
R O W N |
Get the wires lined up and nice and straight. Then
clip off the top millimeter so that they are all the same length and stick out
about half an inch from the insulated part.
Connecting two machines
to each other
Ethernet has two pairs of
wires in a twisted pair setup: one pair for transmit and one for recieve.
When
you connect a bunch of machines together using a hub, the hub relays all the
information from all the Transmit pairs to all the Receive pairs. That is, each
machine sees on its receive pairs the information sent on every machine's
Transmit pairs. The hub logically connects all the Transmit pairs to all the
Receive pairs. I say "logically" because this represents the information
flow. You can't physically connect all these wires together because all the
electrical signals would get messed up.
N.B.: If you're trailer-trash, think of it like the
thingie you have to put between your truck's turn signals and the trailer
wires, so it don't flash too fast. You do got a truck, don't you?
Now, if all you want to do is connect your trusty 386 to
your friend's Powerbook, then you don't need to deal with all this crap. All
you need, assuming both machines have an Ethernet RJ-45 connection, is a
cross-over cable. The cross-over cable works only between two machines to
connect one's transmit to the other's receive. It's like a hub with only two
ports.
Update:
if you have a new powerbook, you can forget the cross-over cable. In fact with
most new switches you can forget it too. Most equipment now has autosensing to
determine if a cross-over connection is required, in which case it just
switches the connection electronically automatically. You don't need a special
cable.
You can
- A. Buy a cross-over cable
- B. Make a cross-over cable
- C. Make a cross-over plug, so you don't have
any weird cables around.
B isn't hard. Here's the connection diagram:
C
is maybe best. You just take two RJ-45 sockets and wire them back to back,
crossing over the orange and green pairs. Then you can use conventional,
non-cross-over ethernet cables to connect each machine to the cross-over
sockets.
