In this chapter we will look at the lowest layer of the OSI model - the physical layer. It defines connector and interface specifications, as well as the medium (cable) requirements. Its purpose is to transport a raw bit stream from one host to another. Electrical, mechanical, functional, and procedural specifications are provided for sending a bit stream on a computer network.
We will cover two kinds of transmission media: guided (copper wire and fiber optics) and wireless (terrestrial radio).