The medium by which information is transmitted is known as a communication channel. Some of the common communication channels are fiber optic cable, coaxial cable, satellite and microwave. The transfer of data takes place in the form of analog signals and the transfer of data is measured in the form of bandwidth, the higher the bandwidth the more the data that will be transferred.
Communication channels are divided in two categories, namely guided media and unguided media.
Guided Media
In this category the communication device is attached to each other directly with cables. The data signals are restricted to a cabling platform and thus they are also known as bounded media. Generally the guided media is called LAN. Some kinds of guided media are coaxial cable, twisted pair wire and fiber optic cable.1) Twisted Pair Cable - It is the most common used communication media and used in LAN (local area network) for transfer of data between various computers. They are also used in landline telephones to transfer data signals and voice. They are made from a pair of copper wire. They are covered with insulating materials like plastic. The transmission of data takes place at a speed of 9600 bits/second within a distance of 100 meters.
2) Coaxial Cable - They are also known as coaxes and carries signals with high frequency range. They are made from a single copper wire. They are also used in telephone lines. The bandwidth is 80 times more than twisted pair cable. They are also used in LAN.
3) Fiber Optic Cable - They use light to transfer data. The data is transferred at a very high speed of billions bit/second. They are highly used by cable operators, telephone, and broadband internet companies. They are made from glass and is as thin as the human hair. They are coated with plastic also known as jacket.
Unguided Media
In this form the data is transferred in the form of waves. This means that they do not travel along a specific path. It is also known as unbounded media. Data can be transferred all over the globe. Kinds of unguided media are microwave, cellular radio, radio broadcast and satellite.1) Microwaves- In this kind the data is transferred via air. The waves travel in a straight line. The data is received and transferred via microwave stations. The speed at which data is transferred is 150 Mbps. They are widely used by telephone and cable companies.
2) Satellite- The signals are received from earth stations. Devices like GPS and PDAs also receive signals from these earth based stations. These satellites are located at a distance of 22300 miles above the earth. The process of transferring and receiving data takes place within few seconds. The data is transferred at a speed of 1 Gbps. They are used for purposes like weather forecast, military communication, radio transmission, satellite TV, data transmission, etc.
3) Cellular Radio- they are used for communication via mobile. High frequency radio waves are used for the transmission of data. You can receive and make calls and also access the internet.
4) Radio Broadcasting- Data is transferred and received via radio signals in the air. The transmission takes place for a long distance across cities or countries. The data is received and transferred via a transmitter. The speed at which data travels is 54 Mbps.
About the author: Jerry Martin is a well known author and writes articles for the website ctmelectrical.com.au. In this article Jerry has given information on Communications Melbourne.
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Source: http://www.naijatechguide.com/2012/08/communication-channel-overview-guided.html
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