Escient Fireball E-2, Руководство пользователя

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FIREBALL Advanced Users Guide WD041-1-1
10/26/2004
Page 8 of 70
6325 Digital Way Indianapolis, IN 46278 317.616.6789 phone 317.616.6790 fax www.escient.com
There are different grades, or categories, of twisted-pair cabling. Category 5 is the most
reliable and widely compatible, and is highly recommended. It runs easily with 10Mbps
networks, and is required for 100Mbps networks. You can buy Category 5 cabling that is pre-
made, or you can cut & crimp your own.
Category 5 cables can be purchased or crimped as either straight-through or crossed. A
Category 5 cable has 8 thin, color-coded wires inside that run from one end of the cable to the
other. Only wires 1, 2, 3, and 6 are used by Ethernet networks for communication. Although
only four wires are used, if the cable has 8 wires, all the wires have to be connected in both
jacks.
Straight-through cables are used for connecting computers to a hub. Crossed cables are used
for connecting a hub to another hub (there is an exception: some hubs have a built-in uplink
port that is crossed internally, which allows you to uplink hubs together with a straight cable
instead).
In a straight-through cable, wires 1, 2, 3, and 6 at one end of the cable are also wires 1, 2, 3,
and 6 at the other end. In a crossed cable, the order of the wires change from one end to the
other: wire 1 becomes 3, and 2 becomes 6.
To figure out which wire is wire number 1, hold the cable so that the end of the plastic RJ-45
tip (the part that goes into a wall jack first) is facing away from you. Flip the clip so that the
copper side faces up (the springy clip will now be parallel to the floor). When looking down on
the coppers, wire 1 will be on the far left.