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3. Specifications
3.1. Cable specifications
Straight-Through and Crossed-Over Cable Specifications Table
Ethernet Type Cable Requirements Maximum Length
10BASE-T Category 3 or better, UTP or STP 328 ft (100M)
100BASE-TX Category 5 or better, UTP or STP 328 ft (100M)
1000BASE-T Category 5e or better, UTP or STP 328 ft (100M)
Caution: Please do not use telephone cables .Telephone cables do not
support Ethernet or Gigabit.
Twisted-pair cabling comes in various grades, or categories. Category 5 is
required for Fast Ethernet, and is also the most reliable and most commonly
used category. You can buy UTP Category 5 (Unshielded Twisted Pair)
Ethernet cabling in pre-crimped lengths, or you can crimp your own. Crimping
your own can result in faulty connections if the RJ-45 tips are not attached
properly. Pre-crimped Category 5 cabling is available at most computer retail
stores.
The most reliable and commonly used type of Category 5 cabling used is UTP,
or "unshielded twisted pair. "STP” or "shielded twisted pair" wiring is only
necessary for network environments exposed to excessive amounts of
electromagnetic interference, or EMI. These environments include areas with
high sources of electrical power, air conditioning, generators, and radio
signals. STP is also used for wiring outdoors.
There are two types of the wiring: Straight-Through Cables and Crossover
Cables. Category 5 UTP/STP cable has eight wires inside the sheath. The
wires form four pairs. Straight-Through Cables has same pin-outs at both
ends while Crossover Cables has a different pin arrangement at each end.
In a straight-through cable, wires 1,2,3,4,5,6,7 and 8 at one end of the cable
are still wires 1~8 at the other end. In a crossover cable, the wires of 1,2,3,6
are reversed so that wire 1 become 3 at the other end of the cable, 2
becomes 6, and so forth.
To determine which wire is wire 1, hold the RJ-45 cable tip with the spring clip
facing towards the ground and the end pointing away from you. The copper
wires exposed upwards to your view. The first wire on the far left is wire 1.
You can also refer to the illustrations and charts of the internal wiring on the
following page.
There are two types of cables: Straight-through Cables and Crossover Cables.
Category 5 UTP/STP cable has eight wires inside the sheath. The wires form
four pairs. Straight-through Cables has same pin-outs at both ends while
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