Types of Medium (Types de cables )
Unshielded Twisted Pair (UTP) Cable:
The cable has four pairs of wires inside the jacket.Each pair is twisted with a different number
of twists per inch to help eliminate interference from adjacent pairs and other electrical devices.
Categories of Unshielded Twisted Pair
Unshielded Twisted Pair Connector (RJ-45 connector):
The standard connector for unshielded twisted pair cabling is an RJ-45 connector.This is a
plastic connector that looks like a large telephone-style connector (See fig.2) RJ stands for
Registered Jack, implying that the connector follows a standard borrowed from the telephone industry.
This standard designates which wire goes with each pin inside the connector.
Fig. 2. RJ-45 connector
Coaxial Cable & Connectors:
Coaxial cabling has a single copper conductor at its center.A plastic layer provides insulation
between the center conductor and a braided metal shield (See fig. 3).
The metal shield helps to block any outside interference from fluorescent lights, motors, and
Fig. 3. Coaxial cablediv>
Fig. 4. BNC connector
Fiber Optic Cable:
Fiber optic cabling consists of a center glass core surrounded by several layers of protective
materials (See fig. 5). It transmits light rather than electronic signals eliminating the problem
of electrical interference.This makes it ideal for certain environments that contain a large
amount of electrical interference.
It has also made it the standard for connecting networks between buildings,due to its immunity
to the effects of moisture and lighting.
Fig.5. Fiber optic cable
Ethernet Cable Summary:
Wireless LANs use high frequency radio signals, infrared light beams,or lasers to communicate
between the workstations and the file server or hubs.Each workstation and file server on a
wireless network has some sort of transceiver/antenna to send and receive the data.
Information is relayed between transceivers as if they were physically connected. For longer
distance, wireless communications can also take place through cellular telephone technology,
microwave transmission,or by satellite.
Wireless LANs have several disadvantages. They are very expensive, provide poor security,
and are susceptible to interference from lights and electronic devices. They are also slower
than LANs using cabling.