Various symbols are used to represent media types. Token Ring is represented by a circle. Fiber Distributed Data Interface (FDDI) is represented by two concentric circles and the Ethernet symbol is represented by a straight line. Serial connections are represented by a lightning bolt.

Each computer network can be built with many different media types. The function of media is to carry a flow of information through a LAN. Wireless LANs use the atmosphere, or space, as the medium. Other networking media confine network signals to a wire, cable, or fiber. Networking media are considered Layer 1, or physical layer, components of LANs.

Each media has advantages and disadvantages. Some of the advantage or disadvantage comparisons concern:

• Cable length
• Cost
• Ease of installation
• Susceptibility to interference

Coaxial cable, optical fiber, and even free space can carry network signals. However, the principal medium that will be studied is Category 5 unshielded twisted-pair cable (Cat 5 UTP) which includes the Cat 5e family of cables.

Many topologies support LANs, as well as many different physical media. Figure shows a subset of physical layer implementations that can be deployed to support Ethernet.

Web Links Physical Layer http://www.erg.abdn.ac.uk/users/gorry/course/ phy-pages/ phy.html