Media Chapter 2

Two types of Cables Baseband Broadband

Baseband Digital signaling over one wire Electrical pulses or laser light Bi-directional – allows computers to send and receive using one cable. Capable of multiplexing Using TDM (Time Division Multiplexing) – method of putting multiple data streams in a single signal by separating the signal into many segments of short duration. Only changes the way data is transmitted.

Categories of Media Coaxial Twisted pair Fiber Optic

Types of Media Copper – coaxial cable, twisted pair Glass – fiber optic

Interference EMI Could come from fluorescent lights, ungrounded electronic equipment Crosstalk There are 8 wires in twisted pair cable. When electricity flows through a wire, it emanates a electromagnetic field. A pair of wires create a circuit for transmitting data via electrical current. If two wires are in the same electrical circuit, electrons flow from the negative voltage source to the destination along one wire and then the electrons flow from the destination to the positive voltage source along the other wire. If two wires within the cable are carrying a signal, energy from one wire can wind up in an adjacent wire. Thus, EMI within the cable is crosstalk.

Cancellation When two wires in an electrical circuit are placed close together, their magnetic fields are the exact opposite of each other. These magnetic fields cancel out one another. The twisting of the wires improves the cancellation effect.

Attenuation Cable length is specified because as a signal moves along the media it weakens (attenuates).

Coaxial Cable

Thin – 10Base2 Commonly called thinnet, thin wire, or thin Ethernet or cheapernet BNC connector Thick – 10Base5 Commonly called thicknet, thick wire, or thick Ethernet Transceivers and Vampire Taps

Twisted Pair Shielded Twisted Pair (STP) Contains eight copper wires covered in plastic The wires are twisted to reduce crosstalk. Insulated Reduces EMI (electromagnetic interference) Fairly expensive Uses RJ45 connectors Unshielded Twisted Pair (UTP) Commonly called Cat5 Contains eight copper wires covered in plastic The wires are twisted to reduce crosstalk. Not insulated Inexpensive Uses RJ45 connectors

Twisted Pair Categories Cat 1 – Voice-grade UTP telephone cable. Cat 2 – Data grade – transmits up to 4Mbps Cat 3 – Data grade – transmits up to 10Mbps Cat 4 – Data grade – transmits up to 16Mbps (often used with Token Ring) Cat 5 – Data grade – transmits up to 100Mbps Cat 5e – Data grade – transmits up to 1000 Mbps

Thin Coaxial Cable (10Base2) Max speed: 10 Mbps Max length: 185 meters Max #nodes/segment: 30 Max #segments: 5 (only three can have nodes connected) Min distance b/w nodes:.5 meter Transmission method: Baseband Connector: BNC

Thick Coaxial Cable (10Base5) Max speed: 10 Mbps Max length: 500 meters Max #nodes/segment: 100 Min distance b/w nodes: 2.5 meters Transmission method: Baseband Connector: Vampire tap and transceiver

Twisted Pair (10BaseT) Max speed: 10 Mbps Max length: 100 meters Transmission method: Baseband Cable type: Cat 3, 4, 5 UTP or STP Connector: RJ45