5. Specifications
5.1 Cable Specifications
Table 5.1 lists the cables you can use and their specifications.
Caution:
Please do not use telephone cables. Telephone cables do not
support Ethernet or Fast Ethernet
Table 5.1
Straight-Through and Crossed-Over Cable Specifications
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)
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 precrimped lengths, or you can crimp your own. Crimping
your own can result in faulty connections if the
RJ-45 tips are not attached properly. Precrimped 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 pinouts 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
26
