The electronic communication systems may be classified in to various categories as mention below .it shows that the electronic communication system may be basically categorized in to three groups based on:
1)Unidirectional / Bidirectional communication.
2) Nature of information signal.
3) Technique of transmission.
Now , the Unidirectional / Bidirectional communication systems are again classified into three categories .These are written as below:-
1.Simplex system.
2.Half duplex system.
3.Full duplex system.
1)Simplex system:-
In this the information communicated in only one direction.
For example , the radio and TV broadcasting system can only transmit. They can not receive.
Another example of simplex communications is the information transmitted by the telemetry system of a satellite to earth.
2)Half duplex systems:-
These systems are bidirectional. i.e. they can transmit as well as receive but not simultaneously.
At a time , these systems can either transmit or receive , for example , a walk talk set.
The direction of communication alternates. The radio communications such as those used in military , fire fighting , citizen band (CB) and amateur radio are half duplex system.
3)Full duplex system:-
These are truly bidirectional systems as they allow the communication to take place in both the directions simultaneously. These system can transmit as well as receive simultaneously.
For example , the telephone systems. However , the bulk of electronic communications is two - way. The best example of full duplex communications system is the telephone system.
Now the Nature of the communication signals are again classified into two types :-
1.Analog communication system.
2.Digital communication system.
1) Analog communication:-
If the carrier is sinusoidal, then it's amplitude , frequency or phase is changed in accordance with the modulating signal to obtain AM , FM , or PM respectively. There are continuous wave modulation systems. Analog modulation can be pulsed modulation as well. The carrier is in the form of rectangular pulses. The amplitude , width or position of the carrier pulses is varied in accordance with the modulating signal to obtain the PAM , PWM , or PPM outputs.
Examples of analog modulation:-
1.Amplitude modulation (AM).
2.Frequency modulation (FM).
3.Phase modulation (PM).
4.Pulse amplitude modulation (PAM).
5.Pulse width modulation (PWM).
6.Pulse position modulation (PPM).
2)Digital communication:-
The modulation system or technique in which the transmitted signal is in the form of digital pulses of constant amplitude , constant frequency and phase is called as digital modulation system.
For examples , Pulse code modulation (PCM) and Delta modulation (DM) are the examples of digital modulation.
1.In the PCM and DM , a train of digital pulses is transmitted by the transmitter.
2.All the pulses are of constant amplitude , width and position. The information is contained in the combination of the transmitted pulses.
Now the Technique of transmission is classified into two types:-
1) Baseband transmission.
2) Communication using modulation.
1)Baseband transmission:-
The information or the input signal to a communication system can be analog i.e. sound, picture or it can be digital e.g. the computer data. The electrical equivalent of this original information signal is known as the baseband signal.
In other words , we can defined a baseband signal as the one which is not modulated. All the voice, data and picture signals are called as the baseband signals.
2) Communication using modulation:-
1)Unidirectional / Bidirectional communication.
2) Nature of information signal.
3) Technique of transmission.
Now , the Unidirectional / Bidirectional communication systems are again classified into three categories .These are written as below:-
1.Simplex system.
2.Half duplex system.
3.Full duplex system.
1)Simplex system:-
In this the information communicated in only one direction.
For example , the radio and TV broadcasting system can only transmit. They can not receive.
Another example of simplex communications is the information transmitted by the telemetry system of a satellite to earth.
2)Half duplex systems:-
These systems are bidirectional. i.e. they can transmit as well as receive but not simultaneously.
At a time , these systems can either transmit or receive , for example , a walk talk set.
The direction of communication alternates. The radio communications such as those used in military , fire fighting , citizen band (CB) and amateur radio are half duplex system.
3)Full duplex system:-
These are truly bidirectional systems as they allow the communication to take place in both the directions simultaneously. These system can transmit as well as receive simultaneously.
For example , the telephone systems. However , the bulk of electronic communications is two - way. The best example of full duplex communications system is the telephone system.
Now the Nature of the communication signals are again classified into two types :-
1.Analog communication system.
2.Digital communication system.
1) Analog communication:-
If the carrier is sinusoidal, then it's amplitude , frequency or phase is changed in accordance with the modulating signal to obtain AM , FM , or PM respectively. There are continuous wave modulation systems. Analog modulation can be pulsed modulation as well. The carrier is in the form of rectangular pulses. The amplitude , width or position of the carrier pulses is varied in accordance with the modulating signal to obtain the PAM , PWM , or PPM outputs.
Examples of analog modulation:-
1.Amplitude modulation (AM).
2.Frequency modulation (FM).
3.Phase modulation (PM).
4.Pulse amplitude modulation (PAM).
5.Pulse width modulation (PWM).
6.Pulse position modulation (PPM).
2)Digital communication:-
The modulation system or technique in which the transmitted signal is in the form of digital pulses of constant amplitude , constant frequency and phase is called as digital modulation system.
For examples , Pulse code modulation (PCM) and Delta modulation (DM) are the examples of digital modulation.
1.In the PCM and DM , a train of digital pulses is transmitted by the transmitter.
2.All the pulses are of constant amplitude , width and position. The information is contained in the combination of the transmitted pulses.
Now the Technique of transmission is classified into two types:-
1) Baseband transmission.
2) Communication using modulation.
1)Baseband transmission:-
The information or the input signal to a communication system can be analog i.e. sound, picture or it can be digital e.g. the computer data. The electrical equivalent of this original information signal is known as the baseband signal.
In other words , we can defined a baseband signal as the one which is not modulated. All the voice, data and picture signals are called as the baseband signals.
2) Communication using modulation:-
In the modulation process , two signals are used manly in the modulation signal and the carrier. The
modulating signal is nothing but the baseband signal or information signal while carrier is a high frequency sinusoidal signal.
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