Information Technology Reference
In-Depth Information
in transceiver. Thinnet uses BNC-type connectors and T-adapters. The cable is about
1/4 inch (1 cm) in diameter and is much more flexible than thicknet cable. It is also
less expensive, giving rise to another nickname,
cheapernet
. Distances for a thinnet
Ethernet segment are limited, as compared to thicknet.
ARCnet is another LAN topology that originally used coax cable. Several types
of coax have been used with ARCnet, including RG-11/U, RG-59/U, and RG-62/U.
RG-11/U and RG-59/U are 75-ohm coax cables, while RG-62/U is a 93-ohm cable.
The workstations are connected directly to the coax in a star arrangement. Each leg
terminates in a passive or an active hub device that couples the LAN signal to all of
the other connected workstations or servers.
Coax Wire Sizes
Wire sizes for coax cable are usually specified by “RG” number or manufacturer's
part number. Thick Ethernet cable is a special case that is referred to by the names
Ethernet trunk cable, backbone cable, or 10Base5 cable. A list of coax types used in
LAN wiring is shown in Table A.3. The RG numbering system is a standard coax
cable rating system that identifies physical size, characteristic impedance, power
handling, and other characteristics. Common LAN coax cables are Ethernet, RG-
TABLE A.3
Types of Coax Used in LAN Wiring
Coax type
Impedance
LAN use
Special considerations
RG-6/U
75 ohms
ARCnet
Smaller and cheaper alternative to RG-11/U.
Lower loss but more rigid than RG-59/U.
Must use RG-6/U connectors.
RG-8/U
50 ohms
Ethernet
May substitute for 802.3 cable in an
Thicknet
emergency or special circumstances.
Rg-11/U
75 ohms
ARCnet
Heavy cable is difficult to work with. See
RG-59/U.
RG-58A/U
50 ohms
Ethernet
Stranded center conductor required. Original
“cheapernet” cable.
RG-59/U
75 ohms
ARCnet
Smaller and cheaper than RG-11/U, this cable
is easier to install and readily available, as it is
also used for CATV.
RG-62
93 ohms
ARCnet,
The famous IBM Terminal cable can be
IBM 3270
adapted to ARCnet.
Ethernet
50 ohms
Ethernet
Cable is marked for 802.3. Double-shielded
10Base2
Thinnet
cable similar to RG-8/U.
Ethernet
50 ohms
Ethernet
Cable is marked for 802.3. Similar to
10Base5
Thicknet
RG-58A/U with stranded center conductor.
