Editing Transmission medium (section)

==Telecommunications==
A physical medium in data communications is the transmission path over which a signal propagates. Many different types of transmission media are used as [[communications channel]].

In many cases, communication is in the form of electromagnetic waves. With guided transmission media, the waves are guided along a physical path; examples of guided media include phone lines, [[twisted pair]] cables, [[coaxial cable]]s, and optical fibers. Unguided transmission media are methods that allow the transmission of [[data]] without the use of physical means to define the path it takes. Examples of this include [[microwave]], [[radio]] or [[infrared]]. Unguided media provide a means for transmitting electromagnetic waves but do not guide them; examples are propagation through air, vacuum and seawater.

The term direct link is used to refer to the transmission path between two devices in which signals propagate directly from transmitters to receivers with no intermediate devices, other than amplifiers or repeaters used to increase signal strength. This term can apply to both guided and unguided media.