A transmission medium (plural media) is one which carries a signal from one computer to another. It is also known as communication channel. Transmission medium can be wired or wireless. We also name them as Guided and Unguided Media respectively.
- Wired transmission media includes twisted pair cable, Ethernet cable, coaxial cable and optical fibre whereas wireless transmission media includes microwave, radio wave, satellite, infrared, Bluetooth, WIFI etc.
The wired or guided transmission media physically connects the two computers. The data signal physically gets transferred from the transmitting computer to the receiving computer through the wired transmission medium.
- Coaxial Cables
It is the most commonly used transmission media for LANs. It consists of solid wire cores surrounded by one or more foil or wire shields, each separated by some kind of plastic insulator. The inner core carries the signal and the shield provides the ground. It has high electrical properties and is suitable for high speed communication. It is widely used for television signals and also by large corporations in building security systems. Multi channel television signals can be transmitted around metropolitan areas at considerably less cost.
- Optical Fibres
These consists of thin strands of glass or glass like material which are so constructed that they carry light from a source at one end of the fibre to a detector at the other end. The light sources used are either light emitting diodes (LEDs) or laser diodes (LDs). The data to be transmitted is modulated onto a light beam using frequency modulation techniques. At the receiver’s end, the signals are demodulated.