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Computer Networks/Networks Ma Profession University

Notes Unit 3: Physical Layer

CONTENTS
Objectives
Introduction

3.1 Transmission Concepts and Terms
3.2 Bounded Media
3.2.1 Twisted Pair (Copper Conductors)

3.2.2 Coaxial Cable
3.2.3 Optical Fiber
3.3 Summary
3.4 Keywords
3.5 Review Questions

3.6 Further Readings

Objectives

After studying this unit, you will be able to:

Identify the major types of transmission media
Describe transmission terms and concepts
State few advantages and disadvantages of each transmission medium
Analyze the general properties of each type of bounded transmission media

Introduction

Information has been attached with considerably increased value if it can be conveyed clearly to
others. This is a basic principle that is well understood in this information age. The conveyance,
or transmission, of information across a distance necessarily involves some form of transmission
medium. The selection of physical transmission media that serve to transport the information is
critical to its successful conveyance. In interactive communication, the medium can be critical to
the message. The transmission of an electrical signal requires the use of a transmission medium,
which normally takes the form of a transmission line. There are various ways to transmit the
signal. These ways can be broadly categorized into guided and unguided media. The guided
media includes all wired media, also referred to as conducted or bounded media. The second
category includes all traditional wireless media, also referred to as radiated, or unbounded. In
the transmission of signal the data is encoded to energy and then energy is transmitted. Similarly
at the receiving end the energy is decoded back to data. This energy can be electrical, light and
radio, etc. Therefore this transmitted energy is carried through some sort of medium which
depend upon the type of energy being transmitted. The energy in different forms has different
properties and therefore cannot be transmitted using the single media. They have different
requirements for transmission which may include special hardware for data encoding and
connection to transmission medium. Media can be copper and glass as bounded media and air as
unbounded media.

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