Transmission media.
Definition :
1. It describes the type of physical system used to carry a communication signal from one system to another ; OR
2. Materials or substances capable of carrying one or more signals in a communications channel.
Two types of transmission media: physical and wireless.
Example
-physical transmission media: twisted-pair cable, coaxial cable & fiber-optic cable.
-wireless transmission media: Infrared, broadcast radio, cellular radio, microwave radio & communication satellite.

Transmission Media Terms

Terms	Definition
Twisted-pair cable	A networking cable consisting of wire strands twisted in sets of two and bound into a cable.
Coaxial Cable	A networking cable consisting of center wire inside a grounded, cylindrical shield, capable of sending data at high speeds.
Fibre-optic cable	A networking cable that utilizes hundreds of thin transparent fibers over which lasers transmits data as light.
Communication Satellite	An earth-orbiting device that relays communications signals over long distances.
Cellular Radio	A form of broadcast radio designed for use with cellular telephones that broadcast using antenna located inside honeycomb—shaped cells.
Microwave	An earth-based device that sends and receives high-frequency, high-speed radio signals.