Physical mediums: are actually wires or cables used to connect two or more devices. These can be twisted pair, coaxial and fiber optic cables. Twisted pair cables were traditionally used in telephone wire lines and cables. But they are still widely used in networks and other uses. They are called "twisted pair" cables because they have many small thin insulated wires twisted around each other in a balanced circuit. Twisted pair cables can contain up to 4200 pairs of wires.