In a data transmission system, the transmission medium is the physical path between transmitter and receiver.The transmission media that are used to convey information can be classified as guided or unguided.

 

The characteristics and quality of a data transmission are determined both by the characteristics of the medium and the characteristics of the signal.

In the case of guided media, the medium itself is more important in determining the limitations of transmission.For unguided media, the bandwidth of the signal produced by the transmitting antenna is more important than the medium in determining transmission characteristics.