TRANSMISSION MEDIA part 1..../ Types of Transmission Media
As mentioned, the twisted-pair cable is the most common cable used in local area networks.
It’s relatively easy to work with, flexible, efficient, and fast. As a network administrator,
you should know how to identify the different types of twisted-pair cabling, as well as how
to install twisted-pair cabling in a permanent fashion and as a temporary solution. It’s
also important to know how to test twisted-pair cables in the event one fails or as a way of
proving that new installations work properly
Twisted-pair cables are the most common of all copper-based cables. A single twisted-pair
cable has eight wires; they are insulation-covered copper conductors that transmit
electric signals. This is just one type of copper media, but it is the most common. These
eight wires are grouped into four pairs: blue, orange, green, and brown. Each pair of wires
is twisted along the entire length of the cable. And all of the pairs are twisted together
as well. The reason the wires are twisted together is to reduce crosstalk and interference,
which you’ll learn more about later in this lesson
Examine the back of your computer and locate the network adapter. There should be
a twisted-pair patch cable that connects the network adapter to the network. If not,
and you use a wireless connection, examine the back of your central connecting device,
whether it’s a router, a switch, or a hub. Identify the patch cable that connects to that
device. If you decide to disconnect the cable, keep in mind that the Internet connection
will be temporarily lost, and any downloads will be stopped. The cable should look
similar to the one shown in Figure 3.1. The cable in the figure is being shown from the
side of the RJ-45 plug. You can see where the cable itself enters the plug and where the
plastic sheath is cut, exposing the individual wires. Also, notice the teeth that bite into
the plastic jacket (they are called out with a black rectangle). Once the plug is crimped
onto the cable, these teeth ensure that the cable does not slip out of the plug.
Twisted-pair cables are used in transmitting the information. We discussed this a little earlier
in the lesson, however, I wanted to share a comparison between STP and UTP cables.
Twisted-pair cables are typically used across distances. The twist in the wire cancels out
any magnetic interference that may develop. The common types of twisted pair cables are
shielded twisted pair (STP) and unshielded twisted pair (UTP). STP has shielding material
that is used to help terminate any external noise that may occur. UTP cables have no protection
against noise and their performance is often degraded.
One disadvantage of using STP is that it costs more. The shielding also causes the cable
to be heavier and can be more challenging to bend. UTP is used more in-home networks
and small offices since it has a lower cost than STP.
UTP CONNECTORS AND TOOLS
- AFFORDABLE
- MOST COMPATIBLE CABLING
- MAJOR NETWORKING SYSTEM
- SUFFERS FROM EXTERNAL ELECTROMAGNETIC INTERFERENCE
Pair of wires wound around each other placed inside a protective foil wrap Metal braid or sheath foil that reduces interference Harder to handle (thick, heavy) STP is used in IBM token ring networks. Higher transmission rates over longer distances.
ADVANTAGE
Shielded Faster than UTP
Disadvantages of STP:
More expensive than UTP High attenuation rate
