1. Anything that can carry information from a source to a destination.
Transmission Media
Anything that can carry information from a source to a destination.

2. Classification of Transmission Media
Guided
(Wired)
Twisted Pair Cable
Coaxial Cable
Fiber-Optic Cable
Unguided (wireless)
Free Space

3. Classification of Transmission Media
Guided Media: The media that contain some conducting material or metal to carry data or signals. It includes twisted pair cable, coaxial cable and fiber optic cable.
Unguided Media: Electromagnetic waves are transported without a physical conductor. Signals are broadcast through air, thus available to anyone who has a device capable of receiving them

4. Twisted Pair Cable
A twisted pair consists of two conductors (normally copper about 1mm thick), each with its own plastic insulation, twisted together.
The helical form reduces the electrical interference .
Used for transmitting analog or digital signals and frequency ranges from 100Hz to 5MHz.
Used in telephone lines to provide voice and data channels and in LANs

5. Coaxial Cable
Coax carries signals of higher frequency ranges than those carried twisted pair.
Coax has a central core conductor of solid wire (usually copper) enclosed in an insulating sheath which is in turn enclosed in an outer conductor of a metal.
Used in Analog telephone network, Cable TV and Thin Ethernet.
Frequency ranges from 100KHz to 500 MHz.

6. Optical Fiber
A fiber optic cable is made of glass or plastic and transmits signal in the form of light.
An optical transmission system has three components i.e., a light resource, the transmission medium and the detector.
Optical fiber consists of a central glass core, surrounded by a glass cladding of low refractive index. The cladding is surrounded by a plastic jacket. Light propagates through the core.
Less use of repeaters.
High bandwidth, immunity, Less attenuation, high cost.

7. Wireless communication No physical conductor used
Unguided Media
Wireless communication
No physical conductor used

8. Types of wireless communication
Micro Wave
Infra Red
Radio Wave

9. Propagation Methods
Ground Propagation: Low frequency Signals (Radio waves) travel in all directions through lowest portion of the atmosphere close to the earth.
Sky Propagation: High frequency radio waves are radiated upward and reflected back by the ionosphere back to the surface of earth.
Line Of Sight Propagation: Very high frequency signals are transmitted in a straight line path from one antenna to another.

10. Electromagnetic Spectrum
Band
Range
Propagation
Application
VLF
3-30KHz
Ground
Radio LF
30-300KHz MF
300KHz – 3MHz
Sky
AM Radio HF
3-30MHz
Citizens Band
VHF
30-300MHz
Sky and Line of Sight
TV, FM Radio
UHF
300MHz-3GHz
Line of Sight
TV, Cell phone, paging, satellite
SHR
3-30GHz
Satellite
EHF
30-300GHz
Line of sight
Radar, Satellite
Frequency Ranges
Radio Waves
Micro Waves
Infra Red
Visible Light
UV Rays
X-rays
Gamma Rays
3KHz-1GHz
1GHz- 300GHz
300GHz-400THz
400THz-900THz

11. Radio Wave Transmission
3KHZ-1GHZ Frequency
Omnidirectional
Penetrating Power
Ground and Sky Wave Propagation
Used for AM, FM radio, TV, Cell Phones, paging and wireless LANs

12. Micro Wave Transmission
1GHz-300GHz frequency
Unidirectional
Use of repeaters
Line of Sight Propagation
Taller the antenna, greater the distance covered by the signal.
Mostly used for one to one communication (unicasting) in cell phones, satellite network and wireless LANs.

13. Infra Red Waves 300 GHZ to 400 GHZ frequency.
Line of sight propagation.
Cheap, easy and Govt. license not required.
No penetration power.
Used for short range communication.
Used In TV Remote control, DVD players and stereo systems.
Also used for communication between keyboard, mouse, printers, etc with PCs.

14. Laser Transmission / Light Wave Transmission
400 GHz – 900 GHz frequency
A laser beam is used to transfer data.
Unidirectional
Line of Sight Propagation.
A laser and a photo detector is set on both sender and reciever sides.
Used to connect LANs in two buildings

15. Satellite Transmission
An artificial satellite revolves round the earth as the natural satellite moon.
Used for communication.
Revolve in orbits
A geostationary satellite contains several (12-20) transponders which receive the signal from earth, send it back after amplification.
Line of sight propagation
Signals from a satellite are aimed at a specific area called the footprint where the signal power is maximum.