The physical layer is responsible for the transmission of data in the form of raw bits over a physical link between two connected nodes.

Note: The data is transmitted through a medium that can take up many different forms, as we will see later on.

Services provided by the physical layer

Now we will see some of the services that are provided by the physical layer:

Line coding

This is the process of encoding digital data in the form of bits, into a pattern of voltage, current, or photons that can be transmitted through a physical medium.

Some examples of line coding are unipolar, polar, bipolar, and Manchester code, as we can see in the following illustration.

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