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===Impact on communication technologies===

====Impact on communication technologies====

What is the word that comes to your mind when you say communication?  The phone, precisely the cell phone.  We will now look at how the communication technologies evolved.

What is the word that comes to your mind when you say communication?  The phone, precisely the cell phone.  We will now look at how the communication technologies evolved.

===Radio communication===

=====Radio communication=====

The earliest electronic communication devices functioned using radio technology. Many communication devices we know today also function through radio waves. Radio waves are electromagnetic waves. They carry energy through repeated propagation of electric and magnetic fields. Radio waves carry a certain amount of energy and can travel over large distances. When the wave reaches the destination, the receiver gets the amount of information. We cannot see radio waves but we can detect them by building receivers that can detect them. These are called as antennae. They scan the environment for radio signals and respond when they find a signal. They detect the radio signal by the effect of the changing electrical and magnetic fields. Frequency gives a measure of how fast the radio wave is being produced and depends on the source from where the radio waves start. Different radio waves come at different frequencies and we need to build transmitters that detect them.  Sound is a pressure wave – when we produce a sound it travels by disturbing the air particles. If there is no medium, sound cannot travel. What happens when we hear something on a radio?  Originally sound is produced and then it converted into radio waves. These waves are sent and received through instruments called antennae. When your radio antennae receives this radio wave, this is converted back into sound and is played.  <br>

The earliest electronic communication devices functioned using radio technology. Many communication devices we know today also function through radio waves. Radio waves are electromagnetic waves. They carry energy through repeated propagation of electric and magnetic fields. Radio waves carry a certain amount of energy and can travel over large distances. When the wave reaches the destination, the receiver gets the amount of information. We cannot see radio waves but we can detect them by building receivers that can detect them. These are called as antennae. They scan the environment for radio signals and respond when they find a signal. They detect the radio signal by the effect of the changing electrical and magnetic fields. Frequency gives a measure of how fast the radio wave is being produced and depends on the source from where the radio waves start. Different radio waves come at different frequencies and we need to build transmitters that detect them.  Sound is a pressure wave – when we produce a sound it travels by disturbing the air particles. If there is no medium, sound cannot travel. What happens when we hear something on a radio?  Originally sound is produced and then it converted into radio waves. These waves are sent and received through instruments called antennae. When your radio antennae receives this radio wave, this is converted back into sound and is played.  <br>

'''Use of radio waves in astronomy''' : Radio waves are also produced by many celestial objects. By detecting the radio waves that travel through the atmosphere, it is possible to construct images of the astronomical objects. Radio waves can pass through dust and gas unlike light. Radio astronomy along with optical observation is allowing us to understand the universe better.

'''Use of radio waves in astronomy''' : Radio waves are also produced by many celestial objects. By detecting the radio waves that travel through the atmosphere, it is possible to construct images of the astronomical objects. Radio waves can pass through dust and gas unlike light. Radio astronomy along with optical observation is allowing us to understand the universe better.

===Telephone===

=====Telephone=====

Before the cell phone came, most of the long distance voice communication was through the regular telephone. This was based on the idea of travelling sound waves. They cause the mouthpiece to vibrate and this vibration is carried to the receiver at the other end. When a call came from one number, there will be an operator who sits at an office who will connect the call to another receiving number. Now this is different with automatic switches which connect the calls. The transmission of the signals has also become different now with voice being converted into electrical signals. All these transmissions used to happen through physical cables. These cables were either made of copper or optical fibres.   

Before the cell phone came, most of the long distance voice communication was through the regular telephone. This was based on the idea of travelling sound waves. They cause the mouthpiece to vibrate and this vibration is carried to the receiver at the other end. When a call came from one number, there will be an operator who sits at an office who will connect the call to another receiving number. Now this is different with automatic switches which connect the calls. The transmission of the signals has also become different now with voice being converted into electrical signals. All these transmissions used to happen through physical cables. These cables were either made of copper or optical fibres.   

When you make a phone call, the voice signals from your phone get transmitted through these fibres to the nearest telephone  exchange and through a series of switches sent to the receiver. Usually the first few numbers in our telephone number indicates the exchange information.  In the earlier days, long distance calls (outside of the local exchange) could only be made by booking a trunk call.  The users had to 'book' or rent the line through which the call can be made and this used to be done manually by the telephone operators in the exchange.  Now-a-days, with automatic switches, long distance calls can be made directly to any number, even outside the country.  

When you make a phone call, the voice signals from your phone get transmitted through these fibres to the nearest telephone  exchange and through a series of switches sent to the receiver. Usually the first few numbers in our telephone number indicates the exchange information.  In the earlier days, long distance calls (outside of the local exchange) could only be made by booking a trunk call.  The users had to 'book' or rent the line through which the call can be made and this used to be done manually by the telephone operators in the exchange.  Now-a-days, with automatic switches, long distance calls can be made directly to any number, even outside the country.  

===The cell phone===

=====The cell phone=====

The telephone and the radio came together - And we call that the cell phone! We saw how a telephone works.  We also saw what radio waves are and we have some idea of what frequencies mean. There are many frequencies available for the users to talk on. Any geographic area is divided into small plots, and in each area a fixed number of frequencies is used. Each of these areas are called cells. The cell phone is called a cell phone because it functions by dividing a geographical area into small plots or cells through which the transmission takes place. It is possible to make and receive calls when there is a cell phone tower near your area for receiving and sending that frequency. Now do you understand what we mean when we say 'my cell phone has no coverage here'?  It is because of this also that cell phones sometimes do not work inside buildings when the radio signals are disturbed. Just like an exchange for regular telephone calls, there is a mobile switching that allows you to make calls even when you move from one cell  to another!

The telephone and the radio came together - And we call that the cell phone! We saw how a telephone works.  We also saw what radio waves are and we have some idea of what frequencies mean. There are many frequencies available for the users to talk on. Any geographic area is divided into small plots, and in each area a fixed number of frequencies is used. Each of these areas are called cells. The cell phone is called a cell phone because it functions by dividing a geographical area into small plots or cells through which the transmission takes place. It is possible to make and receive calls when there is a cell phone tower near your area for receiving and sending that frequency. Now do you understand what we mean when we say 'my cell phone has no coverage here'?  It is because of this also that cell phones sometimes do not work inside buildings when the radio signals are disturbed. Just like an exchange for regular telephone calls, there is a mobile switching that allows you to make calls even when you move from one cell  to another!