Communicate means to exchange information between each other. There are lots of ways available through which we can communicate with each other. These are speech, gestures etc. Basically long distance communications are done with the help of electrical signals.
Electrical signals can reach to longer distances with extremely high speeds nearly about 3 x 108m/sec.
Communication basically means making contact with people. In this sending and receiving of signals took place. Sending and receiving is done by using some electric means. This communication process was started in 1840’s. Then triode tubes were discovered. Radio communication was made successful by using these tubes. After some passage of time IC’s, transistors etc were used to improve the radio communication.
Today we are using satellites and fiber optics as the most fast and efficient ways of communication for long distance communication.
The basic things which must be present in a modern communication system are:-
a) Processing of information, sorting and storage of information must be there.
b) After refining the disturbances actual transmission should take place.
c) A reception must be present. It is mainly used for storage, decoding, and interpretation of information.
Let’s discuss the above diagram:
1. Information: The message which is conveyed is known as Information. Information sent is measured in bits.
2. Transmitters: The main task of transmitter is to transform the incoming signals into suitable electrical signals.
First processing of the incoming signals took place. Then these are encoded for transmission over the communication media and appropriate reception.
For the proper propagation of signals, information carrier waves are used. In this process information signals are bounded up with a carrier wave having high frequency.
Any technique i.e. frequency modulation, amplitude modulation, pulse modulation etc can be used.
3. Receiver: Those signals which are modulated by the transmitter for transmissions are demodulated using the receiver. So, we can say that it has the reverse function as compared to the transmitter.
Receivers are of different types. Small size receivers are simple crystal receivers used along with the headphones. On the other hand, large and complex radar receivers are also present.
The signals that are received by a receiver can also put into a VDU (Video display unit), TV, a loudspeaker, a computer and much more.
One important thing to notice is that transmitters and receivers used must follow some standards. Suppose if non standard devices are used then there may be possibility that after modulation the information will reach to the receiver, then the receiver may or may not understand the format or it can display any error message. So, both devices must be compatible with each other.
Channel Noise: When the transmission of information is done then that transmission has a particular frequency. This frequency range is called channel.
Noise may be due to some other signal interference or due to some character present in the transmission signal. Noise can stop communication at any point. The effect of noise will increase if the transmission signal will be of low strength.
Some common methods used for communication are:
1. Mobiles
2. Emails
3. Telephone
4. Radio Broadcasting
5. Television Broadcasting
6. Fax
7. Telemarketing
The common communications which are based on medium, used between the sender and receiver end are:
1. Satellite Communication
2. Optical Communication
3. Sky wave Communication
4. Cable Communication
5. Ground wave Communication
Categories of communication on the basis of signal are:
A) Digital Communication
B) Analog Communication
Digital Communication: Communication in which digital signals are used. The voltage in digital communication consists of two levels. One level is denoted by 0 and other by 1. So, due to levels it is called as a discontinuous signal. It is shown in the figure given below:
In digital Communication binary number system is used. It consists of two digits 0 and 1. That’s why binary system is suitable with it. 0 and 1 are known as bits. The binary number has 2 digits. So, number of combinations that can be formed using these digits is 2n. In this case the no of digits are 2. So, the combination formed will be 22=4.
Formed combinations are:
00, 01, 10, 11.
Analog Communication: In this analog signals are used. In these signals the value of voltage changes continuously. So at different points analog signal will show distinct voltage values. This changing voltage has a maximum and minimum range. Its maximum voltage is represented by vmax and minimum one is denoted by vmin. The figure is shown below:
