How to make the two kinds of cables which
can be used to network two or more computers together to form quick and
simple home or small office local area networks (LANs).
A LAN can be as simple as two computers, each having
a network interface card (NIC) or network adapter and running network
software, connected together with a crossover cable.
The next step up would be a network consisting of
three or more computers and a hub. Each of the computers is plugged
into the hub with a straight-thru cable (the crossover
function is performed by the hub)
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CABLE , CONNECTORS and TOOLS
| CAT 5 cable has four twisted
pairs of wire for a total of eight individually insulated
wires. Each pair is color coded with one wire having a
solid color (blue, orange, green, or brown) twisted around a second
wire with a white background and a stripe of the same color.
The solid colors may have a white stripe in some cables. Cable
colors are commonly described using the background color followed by
the color of the stripe; e.g., white-orange is a cable with a white
background and an orange stripe. |
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CONNECTORS.
The straight
through and cross-over patch cables discussed in this article
are terminated with CAT 5 RJ-45 modular plugs. RJ-45 plugs are
similar to those you'll see on the end of your telephone cable
except they have eight versus four or six contacts on the end of the
plug and they are about twice as big. Make sure they are rated
for CAT 5 wiring. (RJ means "Registered Jack").
Also, there are RJ-45 plugs designed for both solid core wire and
stranded wire. Others are designed specifically for one kind
of wire or the other. Be sure you buy plugs appropriate
for the wire you are going to use. |
| Modular Plug Crimp Tool. |
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COLOR-CODE STANDARDS
pin-out diagrams of the two types of UTP Ethernet cables
Note that the TX (transmitter) pins are
connected to corresponding RX (receiver) pins, plus to plus and minus to
minus. And that you must use a crossover cable to connect
units with identical interfaces. If you use a straight-through
cable, one of the two units must, in effect, perform the cross-over
function.
Two wire color-code standards apply: EIA/TIA 568A
and EIA/TIA 568B.
RJ-45 jacks as follows:
at the cable end:
If we apply the 568A color code and show all eight
wires, our pin-out looks like this:
Note that pins 4, 5, 7, and 8 and the blue and brown
pairs are not used in either standard. Quite contrary to what you
may read elsewhere, these pins and wires are not used or required to
implement 100BASE-TX duplexing--they are just plain wasted.
Again, the wires with colored
backgrounds may have white stripes and may be denoted that way in diagrams
found elsewhere. For example, the green wire may be labeled
Green-White. The background color is always specified first.
Now, all you need to remember, to
properly configure the cables, are the diagrams for the two cable ends and
the following rules:
It makes no functional
difference which standard you use for a straight-thru cable.
You can start a crossover cable with either standard as long as the other
end is the other standard. It makes no functional difference
which end is which. Despite what you may have read elsewhere, a 568A
patch cable will work in a network with 568B wiring and 568B patch cable
will work in a 568A network.
The total length of wire segments between a
PC and a hub or between two PC's cannot exceed 100 Meters (328 feet) for
100BASE-TX (and 10BASE-T).
MAKE the CABLES
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Strip one end of the cable a little over 1/2" of
the jacket off the cable. Untwist the pairs and arrange the wires in
the order of the desired cable end. It is very important that the
unstripped (untwisted) end be slightly less than 1/2" long.
If it is longer than 1/2" it will be out-of-spec and
susceptible to crosstalk. If it less than slightly less than
1/2" it will not be properly clinched when RJ-45 plug is
crimped on There should be little or no space between the wires. The
jacket should end just about where you see it in the diagram Hold
the RJ-45 plug with the clip facing down or away from you.
Push the wire firmly into the plug. Looking through the bottom
of the plug, the wire on the far left side will have a white
background. The wires should alternate light and dark from
left to right. The furthest right wire is brown. |
| The wires should all end evenly at the
front of the plug. The crimper pushes two plungers down on the
RJ-45 plug. One forces what amounts to a cleverly designed
plastic plug/wedge onto the cable jacket and very firmly clinches
it. The other seats the "pins," each with two teeth
at its end, through the insulation and into the conductors of their
respective wires. |
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