2 Transmission Media

Transmission Media The most common network transmission media  Coaxial cable Twisted-pair cable  Fiber-optic cable  Wireless communications

Transmission Media Factors to be considered for cable installation      

Cost. Ease of installation. Transmission rates (Bandwidth). Immunity to EMI.(Electromagnetic Interference) Signal interception. Attenuation

Transmission Media Coaxial Cable 

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Coaxial cables were the first cable types used in LANs. Coaxial cable consists of two electrical conductors sharing the same axis, with insulation in between and encased in a protective sheath. Coaxial cable is used bus topology

Transmission Media Coaxial Cable Coaxial cables are categorized by their by their radio grade (RG) ratings. Each RG number denotes a unique set of physical specifications. These include the wire gauge of the inner insulator, the construction of the shield, and the size and type of the outer casing. There are two types of coaxial cable : • RG58, which is known as Thin Ethernet (0.195 inches, used in Thin Ethernet 10BASE2 network)

• RG8, also known as Thick Ethernet (0.405 inches , used in Thick Ethernet 10BASE5 networks.) RG59 is another type of coaxial cable that has 75-Ohm impedance. It is used to connect a cable modem to a CATV network. RG6 also has 75-Ohm impedance and is commonly used for satellite CATV.

Transmission Media Coaxial Cable Connector •Type N : - Used with RG8 coaxial cable. •Type BNC :- Used with RG58 coaxial cable. •Type F :- Used with CATV coaxial cables.

Transmission Media Twisted-pair cable • Twisted-pair is a type of cabling that is used for telephone communications and most modern Ethernet networks • A pair of wires form a circuit that can transmit data. The pairs are twisted to prevent cross talk, the noise generated by adjacent pairs There are two basic types: 1.Shielded twisted-pair (STP) 2.Unshielded twisted-pair (UTP)

Transmission Media Shielded twisted-pair (STP) cable •STP cable costs more than thin coaxial or unshielded twisted-pair cable. STP is less costly, however, than thick coax or fiber-optic cable. Maximum transmission rate of 500 Mbps (Although only few implementations exceed 155 Mbps with 100-meter cable runs ) STP

Shielded twisted-pair (STP) cable consists of pair of wires is wrapped in metallic foil to further shield the wires from noise. The four pairs of wires are then wrapped in an overall metallic braid or foil. STP reduces electrical noise, both within the cable, termed crosstalk, and from outside the cable, termed EMI and RFI.

Uses RJ-45 Connectors to connect to the network.

•Distance limited to 100 meters for 500 Mbps •At minimum the shield of the STP cable must be grounded at both ends of a continuous cable. •Used in IBM Token ring network and Ethernet (10BASE T/100BASE TX/ 1000BASE TX etc.)

Transmission Media Unshielded twisted-pair cable (UTP) •Low cost compared to other media •Relatively easy to install, requiring very few specialized tools. •Used in 10BaseT, 100Basetx, 100BaseT4, 1000BaseT. Unshielded twisted-pair (UTP) cable has two or four pairs of wires. This type of cable relies solely on the cancellation effect produced by the twisted wire pairs to limit signal degradation caused by electromagnetic interference (EMI) and radio frequency interference (RFI). Uses RJ-45 Connectors to connect to the network.

•Because UTP cable lacks a shield, it is more sensitive to EMI than coaxial or STP cables.

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Transmission Media

Available UTP cable categories

Transmission Media Fiber-Optic Cable Fiber optic cables transmit pulses of light over a glass or plastic conductor. than are copper cables .Fiber optic cable has a glass or plastic core surrounded by cladding that reflects the light pulses back and forth along the cable's length.

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Transmission Media Wireless Media

A wireless network is an alternative method for connecting a Network. These networks use electromagnetic waves such as radio frequency (RF), laser, infrared (IR), and satellite/microwaves to carry signals from one computer to another without a permanent cable connection

Transmission Media Crimping of Twisted UTP/STP. The Telecommunications Industry Associations and Electronics Industry Associations (TIA/EIA) Building Wiring Standards specify two standards, T568A and T568B T568B to identify which color wire in a UTP connection needs to be associated with each contact on the connector.

Transmission Media The types of Ethernet cables available are: Straight-through cable Crossover cable Rolled cable Straight-Through Cable The straight-through cable is used to connect • Host to switch or hub • Router to switch or hub Crossover Cable The crossover cable can be used to connect • Switch to switch • Hub to hub • Host to host • Hub to switch • Router direct to host

Transmission Media