Tranmission Medium -Introduction:

Hai friends in this article let us discuss about, how we are ablet to transmit the signal between the sender and receiver with the help of different transmission medium.Usually a telecommunications system, delivers the message, using different kinds of transmission media.These different types of transmission media includes

1)Copper wires

2)Fiber-optic cables

3)Communication satellites

4)Microwave radio.

Usually to categorize any telecommunications media we consider whether the media uses wire or not.In the case of Wire-based telecommunication, the initial link is provide  between most telephones and the telephone network prior to the transmission and usually this wired media is considered as a reliable means for transmitting messages.These are also called as wireline media.

Telecommunications without wires,are known as wireless communications,and the devices which use these technologies includes

1)Cordless telephones

2)Cellular radio telephones

3)Pagers

4)Satellites.

The mainreason why we use wireless communications is that they offer increased mobility and flexibility and some specialists belive that in the future the wireless devices will also offer high-speed Internet access.The different type of transmission medium used are explained below


i)Wires and Cables:

The original and most dependable medium of communication is wires and cables and they still they remain as the primary means for telephone connections.

These kind of wireline (i.e wired)  have evolved from telegraph to telephone service and inspite of all the advancements, thisc ontinues to provide the majority of telecommunications services all over the world. These Wires are used to connect telephones together not only within a home or office but they are also used to connect these telephones to the nearest telephone switching facility.

Apart from these other type of wireline services employ usually coaxial cable, which is used mainly by cable television and it provide hundreds of video channels to subscribers.Most of these content which are transmitted by these coaxial cable of cable television systems is usually sent by a satellite to a central location, which known as the headend.

Coaxial cables flow from the headend throughout a community and then to individual residences and reach individual television sets in the residents.The coaxial cable network includes amplifiers that process and retransmit the television signals,because the signals get weaken as distance from the headend increases.

ii)Fiber-Optic Cables:

Fiber-optic cables use nothing but specially treated glass which can transmit signals in the form of pulsed beams of laser light. These cables carry many times more information than that of copper wires can,the main advantage of this is that it can transmit several television channels or thousands of telephone conversations at the same time.

For most transoceanic routes,this fiber-optic technology has replaced copper wires and also in areas where the requirement pf large amounts of data is to be sent.This type technology uses laser transmitters at  the transmitter side to send pulses of light via hair-thin strands of specially prepared glass fibers.

At present new improvements has promised that the cables can transmit millions of telephone calls over a single fiber and it is more efficient.These fiber optic cables provide the high capacity,and these forms the backbone links whenever it is necessary to carry the enormous and growing volume of telecommunications and Internet traffic.

iii)Radio Waves:

In the case of the wireless telecommunications, they use radio waves,which are sent through space from one antenna to another,and this forms the medium for communication. These radio waves are mainly used for receiving AM and FM radio and for receiving television.Apart from these, devices such as cordless telephones and wireless radio telephone services,like cellular radio telephones and pagers, also use radio waves.

Usually the telephone companies use microwaves, to send signals over a very long distances.These microwaves use higher frequencies than that of the radio waves, which was used for AM, FM, or cellular telephone transmissions, and these microwaves are used generally when they are required to transmit larger amounts of data and in an efficient manner.

The important characteristics of the microwaves is that it is(its characteristics) similar to those of visible light waves and they transmit pencil like thin beams, which can be received using dish-shaped antennas at the receiver end.These narrow beams, can be focused to a particular destination and it provides a reliable transmissions over short distances on Earth.Usually the higher frequencies are easily able penetrate the ionosphere and they can provide a high-quality signal.

iv)Communications satellites

For the telecommunications to take place all over the globe, communications satellites will provides the necessary requirement for the process of transmitting the signals and this process takes place without any need of a network of wires and cables.

These satellites will orbit the Earth, at a particular speed that enables them to stay above the same place on Earth at all times.These type of orbit is known as the geostationary or geosynchronous orbit where the orbital speed of satellite is in synchronous with that of the Earth’s rotation.Usually these kind of satellites will receive transmissions from Earth and they transmit them back to numerous Earth station receivers which are scattered but within the receiving coverage area of the satellite.

This type of relay function makes it possible for satellites to operate as “bent pipes”, i.e., wireless transfer stations for point-to-point and point-to-multipoint transmissions.These satellites are also used by telephone and television companies to transmit signals across greater distances.This is very useful for Ship, airplane, and land navigators as they receive signals from the satellites so as to determine their geographic positions.The use of satellite, for different applications like dish TV,etc., can be explained from the image below

• Written by Raaghavan Krishnamurthy.
• In category Engineering.
• 15 years ago.

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