Comprehensive notes on Transmission Media Class 12

In this article we will talk about transmission media class 12. This is one topic of Unit 2 Computer Networks. So here we go!

Have a look at first session of Unit 2 Computer Networks by following the below given link:

Evolution of Network

Transmission Media Class 12

Transmission media or communications channel refers to the cables or links used in networking. Basically, the transmission media or communication channels are classified into two categories:

  1. Guided Media or Wired communication Channel
    • Twisted Pair Cable
    • Coaxial Cable
    • Optical Fibres
  2. Unguided Media or Wireless communication Channel
    • Microwave
    • Radio Wave
    • Satellite
    • Infrared
    • Laser transmission
    • Bluetooth

Now we will discuss Transmission Media Class 12 in brief.

Guided Media or wired communication channel

The guided media refers to the different types of cables used in the network. As you have seen above list, now let us talk about all types of guided media.

Twisted Pair Cable

twisted pair cable - transmission media class 12
twisted pair cable – transmission media class 12

As you have seen the above picture. This picture includes twisted-pair cables. These cables are twisted together in pairs of two wires wrapped together in helix form.


It is also available in two types:

  1. Shielded Twisted Pair (STP) – have a braided wired mesh that encases each pair of insulated wires
  2. Unshielded Twisted Pair (UTP) – comprise of wires and insulators

Used in

The twisted-pair cables are used into telephone lines, DSL lines, and LAN (Local Area Network)s. As in LANs so it is also known as an ethernet cable.


The twisted pair cables are classified into the following categories. These categories referred as CAT1, CAT2, and so on…

CategoryTypeSpeedUsed in
CAT1UTP<0.1 MbpsTelephone Lines
CAT2UTP2 MbpsTransmission Lines
CAT4UTP20 MbpsToken Ring


  • Reduces the crosstalk
  • It is simple
  • Easy to install and maintain
  • It is very flexible
  • It has low weight
  • It can be connected easily


  • Unable to provide connection over long distances
  • Low bandwidth
  • Not suitable for broadband applications

The next guided media in Transmission Media Class 12 is coaxial cables.

Coaxial Cables

Coaxial Cable - Transmission Media Class 12
Coaxial Cable – Transmission Media Class 12

As you have observed the picture, have you seen this cable in your real life?

The answer is, yes. This types of cables you have seen with your TV and Set-top boxes. These cables consist of a solid wire core surrounded by one or more foil or wire shields. Each foil or shield is separated by some kind of plastic insulator.

Used in

The coaxial cable is used in a telephone network that carries 10,000 voice signals, digital telephone network with 600 Mbps data transfer rates, in cable TVs, ethernet LANs and MANs.


The coaxial cables are classified into three categories as per Radio Government (RG) ratings:

CategoryWattsUsed in
RG – 5975TV Cables
RG – 5850thin Ethernet
RG – 11 50thick Ethernet


  • Suitable for high-speed communication
  • Better than twisted-pair cables
  • Can be used in shared cable network
  • Can be used for broadband transmission
  • Offers bandwidth up to 400Mbps


  • Expensive than twisted pair cable
  • Not compatible with twisted pair cable

The next and last guided media of Transmission Media Class 12 is optical fibers.

Optical Fibers

Fiber optic cable
Fiber optic cable

It consist of thin strands of glass or glass like material. These cables carry light from sources used from one end to another. The first end is considered as source and second is considered as detector.

The light sources are LEDs or LDs. These type of cables used frequency modulation for data transfer. These cable consists of three pieces:

  1. The core – It is made up of glass or plastic that is responsible for travel of lights
  2. The cladding – It is there to reflect the light back to the core
  3. Protective coating – provide protection to the cable

Used in

Fiber optic cables are used in cable TV, and high speed network transmissions.


The fiber optic cables are classified into two categories:

  1. Single-mode fiber
  2. Multi-mode fiber


  • Provides high-speed data transmission
  • Strong and protected cables
  • Provides secure transmission
  • Can be used for broadband transmission


  • The installation process is not easy
  • virtually impossible to to tap
  • Connection losses are more common problem
  • Most expensive cables

In the next section of Transmission Media Class 12, we will talk about the unguided media.

Unguided media or Wireless Communication Channel

The unguided or wireless communication channels referred to a wireless connection to the network. There is no physical connection given through wires in this channel. The connection will be done through either sensors, antenna or any other component. So let us discuss them in detail.

The first unguided media is microwave for Transmission Media Class 12.


This type of unguided medial is used for long distance networking. It consists of the following components:

  1. Transmitter
  2. Receiver
  3. Atmosphere

The microwave has a parabolic antenna mounted on towers to send a beam to other antennas which are tens of kilometres away. As much as the tower is high, the range is greater. With 100 meters high tower, 100 km distance range will be achieved.


  • Cheaper than cables
  • Land is required to fix towers only, saves the space of land to spread the cables
  • It can provide easy communication over difficult terrain
  • It can communicate over oceans


  • Insecure connection
  • The network can be affected by weather effects such as rains, thunderstorms etc.
  • Limited bandwidth
  • Very high-cost maintenance

In the next section of Transmission Media Class 12 we will discuss about radio wave.

Radio Wave

It is using the radio frequency modulation for data transmission. It has two parts:

  1. Transmitter – take data or message, encode it into sine wave and transmit into a radio wave
  2. Receiver – decodes the data or message from sine wave it recieves

In radio wave both transmitter and receiver antennas to radiate and capture the radio singal.

The advantages and disadvantages are similar as micro wave.

The satellite is third unguided media of Transmission Media Class 12 is satellite.


It is just a relay system of the microwave. It provides voice, fax, data, video, email, file transfer, and WWW internet applications. It can provide emergency backup facility when cable communication network crushed by a disaster. In satellite, dish functions as an antenna and the communication equipment to transmit and receive data.

The stationary orbits placed about 22,300 miles above the earth’s surface. These satellite act as relay system for the communication signals.


  • Covers a large area
  • Best alternative of cables
  • It provides good option for commercial use


  • Due to some technical limitations, cannot spread over large area
  • over-crowding at low antennas
  • High cost
  • Significant probability of failure

In the next section Transmission Media Class 12 we will discuss some of the wireless media we are using at personal level.


It uses an infrared lights send data. You are using these infrared at your home.

Guess where and how?

Yes, infrared is used in your remotes like TV, set top box, AC, wireless speakers, automotive doors etc.

It transmits data through the air and propagates within a range. It cannot penetrate the walls. It is suitable for a short distance.


It requires direct light-of-sight. Provides high speed than microwaves. It requires the use of a laser transmitter and a photo-sensitive receiver at each end. It requries point-to-point transmission and affect by weather.


The Bluetooth is very famous for PDAs and sharing files over PDAs like mobiles, smartphones, laptops and palmtops. Now a day a variety of devices can be connected through Bluetooth for file sharing. These devices can be printer, speaker, TV, and so on.

So that’s all from the Transmission Media Class 12. If you enjoyed the post hit the like button and share this article with your friends.

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