Lesson 2 - The Physical Layer

   Introduction

As we learned in the last unit, each protocol provides a service to the layer just above it in the protocol stack, and uses the services of the layer below. Because the Physical Layer (Layer 1) is the lowest layer of the OSI model, it does not use the services of any other layer. However, it provides Layer 2 the service of transmitting a signal, across a physical communication medium, that represents binary bits.

   Objectives

At the end of this lesson you should be able to:

1.	Describe the function of Physical Layer protocols
2.	Explain why each physical medium requires its own Physical Layer protocol
3.	Explain the difference between Manchester encoding and Differential Manchester encoding

Key Point
The Physical Layer deals with transmitting and receiving bits across a physical medium.

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