Chapter 13: Information and Communication Technology
Antenna-powered television has now largely been replaced by cable TV and Dish TV. Among the three (antenna, cable, and dish), antenna-connected TV has the poorest audio-visual quality because the waves lose energy as they travel through the air, generating a weaker signal on the antenna.
Three ways of receiving television: antenna TV, cable TV, and dish (satellite) TV.
The signal received through wires or antenna is converted into digital signals by the internal circuits of the television, and audio-visual content is transmitted using these digital signals. To use a computer as a television via cable, a cable modem is required. Dish TV directly broadcasts digital signals received from a satellite.
1. Digital Signal and Analogue Signal
Digital Signal
A signal is a physical quantity that changes with time. A digital signal is represented by only two digits — 0 and 1 — used in the binary system. It is created, for example, by turning a switch on and off: a high signal (1) when voltage is present, and a low signal (0) when voltage is zero.
The digital signal changes between any two fixed values continuously along with time, and is represented by a square wave.
Analogue Signal
An analogue signal is a signal that indicates a constantly changing physical quantity. It changes continuously with time and is represented by a sine wave (e.g. a signal ranging from -5V to +5V).
Comparison of an analogue signal (smooth sine wave) and a digital signal (square wave of 0s and 1s).
Difference Between Analogue Signal and Digital Signal
| Analogue Signal | Digital Signal |
|---|---|
| Indicates the constantly changing physical quantity. | Represents the physical quantity changing in segments. |
| Constantly changes with time. | Changes by any two fixed values continuously with time. |
| Represented by a sine wave (e.g. -5V to +5V). | Represented by a square wave (e.g. 0V or 5V). |
| ADC (Analogue to Digital Converter) changes it into a digital signal. Example: temperature sensor. | DAC (Digital to Analogue Converter) changes it into an analogue signal. Example: playing music on a computer. |
2. Binary System and Computer Memory
The digital signal is represented using only two binary digits, 0 and 1. A binary number is a combination of only these two digits. There are 4 possible combinations of two binary digits, and 8 possible combinations of three binary digits.
| Number of binary digits | Possible combinations |
|---|---|
| 1 | 0, 1 |
| 2 | 00, 01, 10, 11 |
| 3 | 000, 001, 010, 011, 100, 101, 110, 111 |
Very Important for SEE: This digital data is stored in the computer's memory. Users can store data in different formats such as text, graphics, audio, and video.
Units of Computer Memory
- Bit: A bit is the smallest form of data in a computer. It is short for binary digit, and can be either 0 or 1.
- Byte: A group of eight bits, which works as a single unit of data in a computer.
- 4 bits = 1 nibble.
- 8 bits = 2 nibbles = 1 byte.
- 1024 bytes = 1 kilobyte (KB).
- 1024 KB = 1 megabyte (MB).
- 1024 MB = 1 gigabyte (GB).
- 1024 GB = 1 terabyte (TB).
3. Signal Transmission
The process of transformation of a signal through a medium or channel is called signal transmission. In our daily life, sound is used as an analogue signal medium of communication — for example, landline phones send an analogue communication signal through a wire.
Communication can also be done using signals in the form of potential differences, electromagnetic waves, etc. In the traditional method, analogue signals are used for communication — for example, radio broadcasts using medium waves and short waves.
SEE Focus: In analogue transmission, external effects like mixing of other waves and atmospheric effects can make the signal unclear, and illegal recording of an analogue phone conversation is possible. To avoid signal distortion and for signal protection, analogue signals are digitalized. Digital systems store, transmit, and recreate data using groups of 0s and 1s, making data processing easier with a very low chance of error.
Components of a Digital Communication System
Block diagram of a digital communication system, from source to output signal.
| Component | Function |
|---|---|
| Source | The origin of the signal, e.g. an analogue signal such as sound waves. |
| Input Transducer | Converts the received signal into an electrical signal, e.g. a microphone converts sound into electricity. |
| Encoder | Compresses the data into a minimum number of bits, helping in effective use of the available bandwidth. |
| Modulator | Modulates the data to be transmitted by the carrier, converting it into analogue signals for the channel. |
| Channel | The medium that provides the way for analogue signals from the transmitter to reach the receiver. |
| Demodulator | The first step at the receiver side; demodulates the received signal. |
| Decoder | Re-digitizes the received demodulated signals, removing possible errors in the final output. |
| Output Transducer | Converts the decoded signals into the original physical signal, e.g. a loudspeaker converts current to sound. |
| Output Signal | The final result of the overall signal transmission process, e.g. sound waves recreated at the receiver. |
Difference Between Analogue Communication and Digital Communication
| Analogue Communication | Digital Communication |
|---|---|
| Data is transmitted between transmitter and receiver with the help of analogue signals. | Analogue signals are digitalized, transmitted, and then transformed again into analogue signals as output. |
| Signals are highly affected by external influences. | Signals are less affected by external influences. |
| Coding is not possible. | Coding is possible. |
| Needs small bandwidth. | Needs a large bandwidth. |
4. Baseband and Broadband Transmission
Comparison of baseband transmission (digital signal sent directly through a channel) and broadband transmission (signal converted to analogue for long-distance transmission).
Baseband Transmission
Baseband transmission means transmitting digital signals through a channel without converting them into analogue signals. Sending and receiving happens simultaneously in the same channel. It is used for short-distance transmission, e.g. sending data from one computer to another using a direct cable connection.
Broadband Transmission
Broadband transmission means transmitting digital signals to a channel after converting them into analogue signals; this type of transmission requires modulation. Analogue signals can be sent as optical or electromagnetic waves at various frequencies. The channel is divided into two separate parts (or two separate cables are used) to send and receive signals. It is used for long-distance transmission. In common language, broadband internet is regarded as high-speed internet.
Digital signal modulation types include amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (PSK), which vary the amplitude, frequency, or phase of the carrier wave according to the binary digits being transmitted.
Advantages of Digital Transmission
- Deterioration and noise effects are very less in digital signals.
- Circuits used for digital transmission are much more reliable.
- Digital circuits are cheaper and easier to design than analogue circuits.
- There is less possibility of signal overlap and cross-talk in digital transmission.
- The properties of digital signals do not change in normal conditions.
- Information security can be maintained through encoding and compression.
- Codes for finding and correcting errors are used, so there is less chance of error during transmission.
5. Influence of Digital Technology on Information and Technology
(a) Digital Telecommunication
Fast communication has become possible due to digital communication. Similarly, through a single channel or bandwidth, many telephone calls can be transmitted at once.
(b) Digital Media
Electronic devices used for communication are digital media. Activities like creating new digital media, watching the news, and online information transmission can be done via electronic devices.
(c) Digital TV
Digital TVs come in different shapes with unique characteristics. High-definition TVs are made with the latest digital technology, and Dish TV has expanded television service to different parts of the country.
Four types of digital TV broadcasting: terrestrial, mobile/portable, satellite, and cable.
| Type of Digital TV | Description |
|---|---|
| Terrestrial | Broadcast from a ground-based transmitter to homes. |
| Mobile / Portable | Received on moving devices such as a car audio system or portable digital device (e.g. PDA). |
| Satellite | Broadcast from a satellite through a service provider (e.g. DirecTV) to a home dish. |
| Cable | Broadcast from a cable service operator through a headend to homes via cable lines. |
Digital Technologies Used in Daily Life
Digital devices, the product of the development of digital technology, have made human activities much easier and are applicable in fields such as education, health, entertainment, and finance.
Digital technologies used in daily life: digital thermometer, calculator, online newspaper, digital wallet, digital camera, and smartwatch.
- Infrared/digital thermometer, calculator, online newspaper, digital wallet.
- Online library, speedometer, digital camera, smartwatch, digital calendar.
6. Positive and Negative Effects of Digital Technology
Positive Effects
- Digital Library: Digital versions of textbooks and reading materials are available, developing book-reading habits (e.g. materials in the CDC library).
- Online Newspapers: With internet and smartphones, online newspapers can be read anywhere (e.g. www.gorkhapatraonline.com).
- Digital Payment: Solves the problem of carrying large amounts of cash; money can be sent to a seller's bank account by scanning a QR code, and used to pay taxes or book tickets.
- Online Business: Business materials can be promoted and sold through the Internet.
- Social Networks: Give people the opportunity to express opinions publicly and connect people digitally even when far apart physically.
- Entertainment: Various games and music applications are available for entertainment.
A QR code displayed at a market stall for scanning to make a digital payment.
Negative Effects
- Excessive online time changes social behaviour, i.e. the way people interact with others.
- Crimes committed through social media can affect personal, family, and social life, damaging reputation and creating mental stress.
- Excessive use of digital material reduces consumption of physical material, resulting in loss of business opportunities.
- Lack of physical exercise in children (due to excessive device use) creates problems like obesity and weakness.
- Digital games containing murder and violence adversely affect mental health, social well-being, and can spread antisocial activities.
- Misuse of digital technology causes harm to others through activities such as cybercrime.
7. Digital Citizenship and Netizen
A person who actively uses and engages in the internet is known as a netizen (a citizen of the internet). Digital citizenship is the citizenship of a netizen in the virtual world of the internet. The development of digital technology has connected citizens across the world through channels like telephone, internet calls, and social networks, leading to the concept of a 'global village'.
Characteristics of a Good Netizen
- Use polite and civilized language in online dialogues and communication (email, public comments on social networks).
- Show personal respect and respect for others online, even without meeting them personally.
- Remember that anything posted online is permanent.
- Respect intellectual property — unauthorized use of others' online material is not permitted; the source must be cited if material is used.
Online Reputation
Reputation management is essential for netizens, just as it is in practical life. A person's real name, photo, and other publicly available details should be used on the online profile to show authenticity and reliability.
- All social media profiles should use the same username for consistency.
- Posts, comments, and shares made by the same person show their knowledge and expertise.
- Being careful about internet security (e.g. strong privacy settings) helps protect online reputation and prevents password theft.
- Online reputation applies to organizations too: follower counts and presence on major platforms indicate institutional credibility, and timely resolution of comments/complaints helps manage it.
8. Digital Wellbeing
Staying online for a long time without maintaining physical balance can be harmful to health, causing problems like obesity, insomnia, vision problems, and mental stress. Unregulated internet use can also cause depression, anxiety, dishonesty, low self-esteem, social isolation, loneliness, and aggressiveness.
Digital well-being is the state of being healthy mentally, physically, socially, and emotionally by balancing the time spent on online and offline activities.
Digital wellbeing: a balance wheel showing connecting time, sleep time, active time, focused time, down time, and work time, alongside mental, emotional, social, and physical wellbeing.
Cautions for Digital Wellbeing
- Separate screen time from other daily activities.
- Set time limits for social media use.
- Turn off mobile notifications while working.
- Use digital well-being applications (e.g. Digital Wellbeing, Action Dash, Digital Detox) to monitor and reduce screen time.
9. Making and Editing Audio-Visual Materials
Audio content can be created by recording sound with a computer or smartphone microphone. Audio-visual content can be created using a smartphone camera or a digital camera.
Video editing means removing unnecessary sections of a recorded video, or combining multiple video clips into a single file. Software such as Adobe Premiere Pro, Filmora, and the Windows built-in Video Editor can be used for this.
Audio editing works similarly, using software like Audacity, which can be downloaded from audacityteam.org.
Common Audio and Video File Formats
| File Type | Common Formats |
|---|---|
| Video | MP4, 3GP, SVI, MOV |
| Audio | MP3, WAV, WMA |
Common Mistakes in SEE
- Do not confuse digital signal (square wave, two fixed values) with analogue signal (sine wave, continuously changing).
- Remember the correct order of the digital communication system: Source → Input Transducer → Encoder → Modulator → Channel → Demodulator → Decoder → Output Transducer → Output Signal.
- Do not confuse baseband transmission (short distance, no conversion to analogue) with broadband transmission (long distance, requires modulation).
- Memory unit conversions are always by 1024, not 1000 — e.g. 1024 bytes = 1 KB.
- A byte is 8 bits, not 8 bytes; a nibble is 4 bits.
- Netizen ≠ digital citizenship: a netizen is a person who is active online; digital citizenship is that person's citizenship in the online world.
Quick Revision
- Digital signal = two fixed values (0,1), square wave; Analogue signal = continuously changing, sine wave.
- Bit = smallest unit of data (0 or 1); Byte = 8 bits; 1024 bytes = 1 KB; 1024 KB = 1 MB; 1024 MB = 1 GB; 1024 GB = 1 TB.
- Digital communication system order: Source → Input Transducer → Encoder → Modulator → Channel → Demodulator → Decoder → Output Transducer → Output Signal.
- Baseband transmission = short distance, no analogue conversion; Broadband transmission = long distance, needs modulation.
- Digital transmission advantages: less noise, more reliable, cheaper circuits, less cross-talk, better error correction.
- Netizen = active internet user; Digital citizenship = a netizen's citizenship in the virtual world.
- Digital wellbeing = balance between online and offline life for mental, physical, social, and emotional health.
- Video formats: MP4, 3GP, SVI, MOV; Audio formats: MP3, WAV, WMA.