Thursday, April 25, 2019

Transmission Media and Its Types [Guided and Unguided Media]


Transmission Media

}  Transmission medium is a channel through which data or signals can be transmitted from sender to receiver.
}  Data is transmitted through the electromagnetic signals.
}  Transmission media are also called communication channels.




Guided Media
}  It is a wired transmission media, in which data signals are guided along a physical path i.e. within a wire. 
}  Also known as Bounded or wired media.
}  Examples are Twisted Pair Cable, Coaxial cable and fiber optic cable.




Twisted Pair Cable
}  A pair of wires which are made of copper and are twisted with each other is known as twisted pair cable.
}  A set of four pairs of twisted wires are bundled to form cable.
}  The wires are twisted to reduce cross talk and electrical interference.
}  It was invented by Alexander Graham Bell in 1881.
}  Its types are :
      Unshielded Twisted Pair Cable (UTP)
      Shielded Twisted Pair Cable (STP)





Unshielded Twisted Pair Cable (UTP)
}  The unshielded twisted pair cable is a Guided Transmission Media, which is used for transmitting both data and voice. 
}  It consists of 4 pairs of colour-coded wires twisted around each other.
}  The wires are twisted to prevent electromagnetic interference (cross talk)
}  Cat 5 cable with RJ-45 connector is commonly used with unshielded twisted pair





Shielded Twisted Pair Cable (STP)
}  The shielded twisted pair cable is a Guided Transmission Media , which is quite expensive than unshielded twisted pair cable.  
}  It has a foil shield that covers the wires.
}  The foil shield adds a layer of protection against electro-magnetic interference leaking into and out of the cable.
}  Shielded Twisted Pair Cable are more expensive than Unshielded Twisted Pair Cable, but less susceptible to noise.




Co-axial Cable
}  A cable which is used with single ended single reference where the central conductor carries the data signal is called co-axial cable.
}  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.
}  Coaxial cable is used in cable television.
}  It is preferred for long distance telephone lines as well.



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.  
}  Fiber-optic cable do not get affected by electromagnetic interference.
}  Works for both analog as well as digital signals.
}  Point to point one way communication generally uses the cable.



Unguided Media
}  Unbounded media are wireless media that does not require any physical medium to transmit electromagnetic signals. 
}  The electromagnetic signals are broadcasted through air to everyone instead of cables.
}  e.g.: radio waves, micro waves and infrared waves.


Radio Wave
}  It is a form of wireless communications in which signals are sent through radio frequency waves.
}  It provides low bandwidth for data communication.
}  The radio waves are generated easily; they are low-frequency signals and can travel a long distance.
}  The radio waves can penetrate through the buildings.
}  Frequency Range:3KHz – 1GHz.
}  AM and FM radios and cordless phones use Radiowaves for transmission.




Microwave
}  It is a form of wireless communication in which data signals are sent through pulses of electromagnetic energy.
}  The microwave has a frequency higher than the radio waves.
}  The microwaves are transmitted in a straight line and hence require the line-of-sight transmission
}  More the taller are antennas longer is the distance covered by the signal.
}  Frequency Range:1GHz – 300GHz. 
}  Microwave are used for telephone communication mobile phones, television distribution, etc.




Infrared
}  Infrared waves are used for short range communication.
}  Like, the remote control for televisions, VCRs, wireless mouse, keyboard, printer, etc. uses infrared waves.
}  It can not penetrate (enter) through obstacles. 
}  Frequency Range:300GHz – 400THz.



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