Transmission Medium and Its Types [Guided and Unguided Medium]

1.      Transmission medium
Transmission medium is a pathway that can transmit information from a sender to a receiver. The types of communication medium are

i) Guided Medium (Bounded or Wired)
ii) Unguided Medium (Unbounded or Wireless)

2.      Guided medium
The transmission media which comprises of cables or wires through which data is transmitted is called guided medium. They are called guided since they provide a physical channel from the sender device to the receiver device. The signal travelling through these media are bounded by the physical limits of the medium. E.g.: twisted pair cable, co-axial cable, fibre optics cable, etc.

3.      Unguided medium
The transmission media which transfer data in the form of electromagnetic waves that do not require any cables for transmission is called unguided medium. These media are bounded by geographical boundaries. E.g.: radio wave, microwave, infrared etc.

4.      Twisted pair cable

A pair of wires twisted with each other is known as twisted pair cable. A set of four pairs of twisted wires are bundled to form cable. These are the most common medium for LAN. Wires are twisted with each other so as to reduce crosstalk (A disturbance caused by electromagnetic interference, along a circuit or a cable pair). Its types are:        a) Unshielded Twisted Pair Cable       b) Twisted Pair Cable

5.      Unshielded twisted pair (UTP)

Unshielded twisted pair is a popular type of cable that consists of two unshielded wires twisted around each other which are used in telephone wiring and local area networks (LANs). It is called unshielded because it has no additional foil wrap, or shield. RJ-45 connector is commonly used with unshielded twisted pair.

6.      Shielded twisted pair (STP)

Shielded twisted pair is a type of copper telephone wiring in which each of the two copper wires are twisted together and coated with an insulating coating. The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference. D-shell connectors are used with shielded twisted pair.

7.      Co-axial cable

Coaxial (or “coax”) cable is a common type of cable used for transmitting data over long distances. They are most commonly used to transmit cable TV and Internet signals. The connectors used with co-axial cables are BNC, T-connectors and terminators in bus topology. 10 Mbps is the maximum speed of co-axial cable.

8.      Fiber optic cable

Fiber optics cable is one of the costlier cables used in data communication which uses light to carry a data signal through the cable. The connectors used in fiber optics are Screw Mounted Adaptors (SMA), Spring-loaded Twist (ST), SC and FC. It is costlier to maintain, produce and install.

9.      Radio wave transmission

The transmission making use of radio waves through air is called radio wave transmission. It provides low bandwidth for data communication. Radio, TV, cellular phones etc. uses radio transmission in one form or another. The radio waves can travel through walls and through an entire building. Depending upon the frequency, they can travel long distance or short distance. It does not require line of sight for data transmission

10.   Microwave transmission

Microwave is a line-of-sight wireless communication technology that uses high frequency beams of radio waves to provide high speed wireless connections that can send and receive voice, video, and data information. Microwaves do not pass through buildings. So, indoor receivers cannot be used effectively. It provides higher bandwidth for data communication. It requires line of sight for data transmission.

11.   Infrared transmission

Infrared Transmission is the transmission of data or voice information over infrared (IR) light over short ranges. It requires line-of-sight and is unable to break through walls.