What is a Communication System?
The communication system is a system model that describes a communication exchange between two stations, transmitter, and receiver. Signals or information passes from source to destination through a channel. It represents a way in which the signal uses it to move from a source toward its destination. To transmit signals in a communication system, it should first be processed by beginning from signal representation, to signal shaping until encoding and modulation. After the transmitted signal is prepared, it is passed to the transmission line of the channel. Due to signal crossing this media, it is faced with many impairments like noise, attenuation, and distortion.
The process of transferring the information between two points is called communication. The main elements needed to communicate are the transmitter to send the information, the medium to send the information and the receiver to receive the information on the other end.
Types of Communication Systems
Based on physical infrastructure:
Based on physical infrastructure there are two types of communication systems:
Line communication systems: Uses the existing infrastructure of power lines to transfer data from one point to another point.
Radio Communication systems: uses the infrastructure of radio waves to transfer the information from one point to another point.
There is a physical link, called a hardwire channel between the transmitter and the receiver inline communication systems.
Based on Signal specifications:
Signal specifications that are used to decide the type of communication system are:
Nature of the baseband or information signal: Baseband signals is a technology which can access the signals with very low frequency and also near zero frequency and based on the nature of the transmitted signal, the baseband signal can either be transmitted as it is without modulation or through a carrier signal with modulation.
Further, communication systems are divided into:
Analog communication systems: The Analog system conveys the information from the audio, video and pictures between two points using the analogue signals. A sinusoidal signal is an example of an analogue communication system.
Digital communication systems: Digital communication has become very important in the age of the internet. It is a physical exchange of information between two points discreetly. The information exchange happens through digital signals.
Baseband communication system: Baseband communication is the transfer of signals that are not amplified to higher frequencies. They help in transferring signals with near-zero frequency.
Carrier communication system: Carrier communication systems transfer the information especially voice messages and calls by improving the frequency much higher than the actual rate.
Out of four, a minimum of two types is needed to specify any communication system. Thus, two groups are formed consisting of each of the two types such that at least one of the types from each group is necessarily required to specify a communication system. These groups can be formed as:
Analog/digital communication systems
Baseband/carrier communication systems
To completely define any communication system, four out of the eight types are required. If any type is missing, then the description of the communication system will be incomplete.
Wireless and Wired communication system
Wireless communication systems use radio waves, electromagnetic waves and infrared waves to communicate from one point to another point and the wire communication system uses wire, optical fibre which works on the phenomenon of total internal reflection to communicate from one point to another point.
Wireless communication is further divided into satellite communication, ground wave communication, skywave and space wave communication. The satellite communication receives the signals from the earth and resends them back to another point on the earth with the help of a transponder. Wired communication is further divided into parallel wire, twisted wire, optical fibre and coaxial wired communication.
Terms Used in Communication Systems
1. Signal
A signal is that information that has been converted into a digital format. Analog signals (such as human voice) or digital signals (binary data) are inputted to the system, processed within the electronic circuits for transmission, then decoded by the receiver. The system is claimed to be reliable and effective; only errors are minimized within the process.
2. Communication Channel
A communication channel is a medium by which a signal travels.
3. Transducer
The device used to convert one form of energy into another form is a transducer.
4. Receiver
A receiver is a device that receives the signals sent/ transmitted by the senders and decodes them into a form that is understandable by humans.
5. Attenuation
Attenuation is the reduction in the strength of analog or digital signal as it is transmitted over a communication medium.
6. Amplitude
An amplitude of the signal refers to the strength of the signal.
7. Amplification
Amplification is the process to strengthen the amplitude of the signals using an electronic circuit.
8. Bandwidth
Bandwidth explains the range of frequency over which a signal has been transmitted.
9. Modulation
As the original message signal can't be transmitted over an outsized distance due to their low frequency and amplitude, they're superimposed with high frequency and amplitude waves called carrier waves. This phenomenon of superimposing a message signal with a carrier wave is called modulation. And the resultant wave is a modulated wave which is to be transmitted.
Different Types of Modulation.
Amplitude Modulation (AM)
Frequency Modulation (FM)
Phase Modulation (PM)
10. Demodulation
Demodulation takes a modulated signal and then extracts the original message from it.
11. Repeater
The repeater extends the range of communication systems by amplifying the signals.
12. Noise
Any electrical signal which interferes with an information signal is called noise.
Did You Know?
Communication Is Related To Every Human Activity.
Communication in Organization Flows in Various Patterns.
Communication Is Media or Channel Based
There are around 250 billion emails sent every day. Around 80% of these are spam.
Around 20 hours of video are uploaded to YouTube every minute.
Fiber optics are good because they use less energy and are better for the environment than electrical wires. They are also very resistant to weather.
The first telephone pole was built in 1876.
There are over 4 billion cell phones within the world and phones that are thrown away every year are over 100 million.
The first cell phone was invented by a company called Motorola.
Over 3.8 billion people use the internet, which is 40% of the world's population.
The first smiley appeared in 1979, it first looked like this -) then three years later a colon was added to it and it took the form of :-) this.
FAQs on Communication Systems
1. What is a communication system and what are its three essential elements?
A communication system is a setup used to transmit information from a source to a destination. The three essential elements of any communication system as per the CBSE syllabus for 2025-26 are:
- Transmitter: This element processes the original message signal to make it suitable for transmission. For example, a microphone acts as a part of the transmitter by converting sound into an electrical signal.
- Channel: This is the physical medium through which the signal travels from the transmitter to the receiver. It can be wired (like optical fibre) or wireless (like free space).
- Receiver: This element receives the transmitted signal from the channel and reconstructs it back into the original message form for the user. A loudspeaker, for instance, converts the electrical signal back into sound.
2. Why is modulation necessary for transmitting low-frequency signals over long distances?
Modulation is crucial for long-distance transmission of low-frequency signals (like audio) for several key reasons:
- Practical Antenna Size: The height of an antenna needs to be comparable to the wavelength of the signal it transmits. Low-frequency signals have very long wavelengths, requiring impractically large antennas. Modulation superimposes the message onto a high-frequency carrier wave, which has a much shorter wavelength, allowing for reasonably sized antennas.
- Effective Power Radiation: The power radiated by an antenna is inversely proportional to the square of the wavelength. Therefore, low-frequency signals radiate very little power, while high-frequency modulated signals radiate power effectively.
- Prevents Signal Mixing: Without modulation, signals from different transmitters would operate in the same low-frequency range, causing them to interfere with each other. Modulation allows different signals to be assigned unique high-frequency carrier bands, preventing overlap.
3. What are some common examples of communication systems used in daily life?
We interact with various communication systems every day. Some common examples include:
- Mobile Phone Network: Allows for voice and data communication wirelessly over large geographical areas.
- Internet: A global system of interconnected computer networks for sharing information.
- Radio Broadcasting: Transmits audio signals (like music and news) from a central station to multiple receivers using radio waves.
- Television Broadcasting: Transmits audio and video signals to viewers, either through satellites, cables, or terrestrial antennas.
- GPS (Global Positioning System): A satellite-based system that provides location and time information anywhere on or near the Earth.
4. How do ground wave, sky wave, and space wave propagation differ?
These three modes of electromagnetic wave propagation are used for different types of communication and differ in their mechanism and frequency range:
- Ground Wave Propagation: The wave travels along the surface of the Earth. It is effective for low frequencies (up to 2 MHz), like in AM radio broadcasts, but its signal strength weakens rapidly with distance due to absorption by the Earth.
- Sky Wave Propagation: The wave is transmitted towards the sky and gets reflected back to Earth by the ionosphere. This mode is used for medium frequencies (3 MHz to 30 MHz) and enables long-distance communication, such as in shortwave radio.
- Space Wave Propagation: The wave travels in a straight line from the transmitting antenna to the receiving antenna (line-of-sight). It is used for very high frequencies (> 30 MHz), as these waves can penetrate the ionosphere. This is the primary mode for television broadcasting, satellite communication, and microwave links.
5. What is the difference between an analog and a digital signal in communication?
The key difference lies in how they represent information:
- An analog signal is a continuous wave where the value changes smoothly over time. It can have an infinite number of values within its range. A classic example is the human voice.
- A digital signal is discrete and non-continuous. It represents information as a sequence of distinct values, typically two levels: on/off, or 1/0 (binary). Computer data is an example of a digital signal. Digital signals are more resistant to noise than analog signals.
6. What is the specific role of a transducer in a communication system?
A transducer is a device that converts one form of energy into another. In a communication system, its primary role is to convert the original message into a suitable electrical signal for transmission, and vice-versa at the receiving end. For example, a microphone is a transducer that converts sound energy (the message) into electrical energy (the signal), while a loudspeaker is a transducer that converts the received electrical signal back into sound energy.
7. How does noise affect the quality of a transmitted signal?
Noise refers to any unwanted electrical disturbance that interferes with a signal during its transmission or reception. It gets added to the message signal, corrupting its original form. This degradation reduces the clarity and fidelity of the communication. For example, noise can manifest as static in a radio broadcast or errors in digital data transmission. Amplifying a noisy signal also amplifies the noise, so techniques like using repeaters (which regenerate the signal) are often preferred for long distances.
8. What is the difference between attenuation and amplification in a communication channel?
Attenuation and amplification are opposing processes related to signal strength:
- Attenuation is the natural weakening or loss of signal strength as it travels through the communication channel. This loss occurs due to energy absorption by the medium.
- Amplification is the process of artificially boosting the strength (amplitude) of a signal using an electronic circuit called an amplifier. It is done to compensate for the effects of attenuation, ensuring the signal is strong enough to be successfully received.
9. What is bandwidth and why is it important in a communication system?
Bandwidth refers to the range of frequencies over which a communication system can operate or that a signal contains. It is critically important because it determines the rate of information transmission. A wider bandwidth allows more information to be sent per second. For instance, a high-quality video signal contains much more information than a speech signal, and therefore requires a much larger bandwidth (around 6 MHz) compared to speech (around 2800 Hz).
10. How does a repeater improve long-distance communication?
A repeater is a device placed at an intermediate point in a long communication link to counteract signal degradation. It functions as both a receiver and a transmitter. It picks up the weakened and attenuated signal, amplifies it, reshapes it, and re-transmits it with renewed strength towards the destination. This process effectively extends the communication range far beyond what would be possible with just a single transmitter and receiver pair.
