Coaxial (coax) cable Coax cable is similar to the cable used to connect a
television set to the cable outlet. There are two types of coax cable used in
networks: thick and thin. Thin coax (also called thinnet and thin wire) remains
common for many networking environments, such as in dam pand dusty places,
but it is slowly giving way to twisted pair. Thick coax (also called thicknet, thick
wire, and yellow wire) is rarely used today in LAN situations.
Coaxial cable is constructed with a single solid copper wire core, which is
surrounded by an insulator made of plastic or Teflon material. A braided metal
shielding layer (and in some cables, another metal foil layer) covers the insulator,
and a plastic sheath wrapper covers the cable. The metal shielding layers act to
increase the cable’s resistance to electromagnetic interference (EMI) and radio
frequency interference (RFI) signals. Figure 20-3 shows a piece of coaxial cable
and its construction. The connector shown in Figure 20-3 is a BNC (Bayonet
Neil-Concelman) type, which is the common connector for coaxial cable.
Twisted pair copper Twisted pair cable is also available in two types:
unshielded twisted pair (UTP) and shielded twisted pair (STP). UTP is similar
to the wiring used to connect your telephone. STP is the cable media of choice
in certain situations where the wire must pass near other electrical components
and is preferred for token ring networks (see “Network Topologies” later in
this chapter).Chapter 20: Networks and Communications^515
Figure 20-3. BNC (Bayonet Neil-Concelman) type cable