Physical Layer

At the end of the day, all these bits and bytes have to be converted into a physical effect so that they can be transmitted.

There are various methods of transmitting information. For example a pulse of light can be used to represent a data bit, fibre optic cables are then used to provide a path in the network.

A radio signal can be used and recently ‘Wi-Fi’ networks have become very popular.

Or plain old electrical signals can be used, which are carried along copper wires. There are millions of Ethernet networks using this method.

It is the job of the PHYSICAL LAYER to convert the abstract ‘data bit’ inside the computer into a physical effect of some kind.

It is concerned about the fine details of the physical bits and pieces that make up the network – how many pins a certain kind of plug has – how long a pulse of light needs to be to represent a ‘bit’. How many volts represent a ‘high’ bit and so on.

Once again, it makes sense to have standards to define this detail and many have been developed to cover the various network types.