Data Communication and Transmission Modes is part of Information and Communication Technology. Below are notes on 163 sub-topics, followed by practice MCQs from State PSC and UPSC papers.
Analog Data
Continuous, infinite range of values. Examples: Human voice, music, temperature.
Digital Data
Discrete, finite set of values (e.g., 0s and 1s). Examples: Text, numbers, images, video files.
Analog Signals
Continuous electromagnetic waves, vary smoothly over time.
Digital Signals
Discrete voltage pulses, represent data as binary 0s and 1s. Less susceptible to noise.
- Fax and email communication primarily use
Digital Signals for transmission.
- Pulse Code Modulation (PCM) Standard technique to convert an analog signal into a digital bit stream. Involves sampling, quantization, and encoding.
MODEM (Modulator-Demodulator)
Converts digital signals to analog (modulation) for transmission over analog lines and converts analog signals back to digital (demodulation) for the receiving device. Performs both Analog-to-Digital (A/D) and Digital-to-Analog (D/A) conversion.
Scramblers (Line Coding Schemes)
Primary use is to make the data look random by preventing long sequences of identical bits (e.g., all 0s or all 1s). This aids timing recovery at the receiver and avoids DC wandering.
Delta Modulation (DM)
An analog-to-digital conversion technique that encodes the difference between the current sample and the previous sample's approximation into a single bit.
Demodulation of a Delta-modulated signal
Achieved primarily by an integration circuit (to reconstruct the staircase approximation) followed by a low-pass filter (to smooth the signal).
2G/2.5G
GPRS (General Packet Radio Service), EDGE (Enhanced Data rates for GSM Evolution).
3G
UMTS (Universal Mobile Telecommunications System). Enables faster voice, data, and video transfer.
4G
WiMAX, LTE (Long Term Evolution).
VoLTE (Voice over Long Term Evolution)
- Digital packet voice service delivered over IP via a 4G LTE access network.
- Transmits both voice and data through the 4G network simultaneously.
- Counts voice calls as per data usage (packet-switched), not minutes of usage (circuit-switched).
- Offers more efficient use of spectrum compared to traditional voice services.
- Eliminates the need for voice to be on 2G/3G networks while data is on 4G.
4G LTE in India
Active bands include Band-40 (2300-2400 MHz, TD-LTE) and 1800 MHz (FDD-LTE).
Modem (Modulator-Demodulator)
Converts digital signals to analog signals (modulation) and analog signals to digital signals (demodulation). Essential for data transfer over analog telephone lines.
Modulation
The process of superimposing information (message signal) onto a higher frequency carrier wave (e.g., radio waves). Converts digital signals to analog for transmission.
Demodulation
The process of extracting information from a modulated carrier wave. Converts analog signals back to digital signals for the receiver.
Amplitude Modulation (AM)
Used for AM radio broadcast and TV picture signals (specifically VSB).
Frequency Modulation (FM)
Used for FM radio broadcast (88-108 MHz band) and TV sound signals.
Phase Modulation (PM)
Often preferred for medium-speed digital communication (e.g., 1200-2400 bits per second).
Vestigial Sideband (VSB)
A variant of AM, used for TV picture signal transmission.
Ethernet
A common standard for wired Local Area Networks (LAN).
Internet Connection Types using Telephone Lines
DSL (Digital Subscriber Line) transmits digital data over local telephone networks.
Reliable byte stream
Movie download (requires full, ordered data).
Unreliable datagram
Voice over IP (VoIP) (prioritizes speed over guaranteed delivery of every packet).
Acknowledged datagram
Text messaging (SMS) (sends discrete packets and often confirms delivery).
Frequency Bands
Commercial FM radio broadcast operates in the 88-108 MHz range.
AM Envelope Detector Time Constant (RC)
For proper demodulation, the time constant must satisfy 1/f_c << RC << 1/f_m_max (where f_c is carrier frequency, f_m_max is maximum message frequency).
Sampling Theorem (Nyquist-Shannon)
To ideally sample a signal, the sampling frequency must be at least twice the highest frequency component present in the signal (f_s >= 2 * f_max). For DSB-SC with carrier f_c and max message frequency f_m_max, f_max = f_c + f_m_max.
IP Addressing (Classful)
Class C IP addresses have their first octet in the range 192-223 (e.g., 195.x.x.x).
CIDR Network Address Calculation
For an IP address X.Y.Z.W/N, the network address is found by setting the (32-N) host bits to zero. For /28, the last 4 bits of the last
00100111, setting last 4 bits to 0 gives 00100000, which is 32).
Asynchronous Transmission
- Transmits data byte-by-byte.
- Each byte framed by start bit (0) and stop bit(s) (1 or more).
- No common clock; timing relies on start/stop bits for synchronization.
- Allows irregular intervals between bytes.
- Lower efficiency due to overhead, simpler hardware.
Synchronous Transmission
- Transmits data in blocks (frames) of multiple bytes.
- Requires a common clock signal between sender and receiver for synchronization.
- No start/stop bits per byte; synchronization at block level (e.g., sync characters, flags).
- Higher efficiency due to less overhead, more complex hardware.
Stop-and-Wait ARQ (Automatic Repeat Request)
- A Data Link Layer flow and error control mechanism.
- Sender transmits one data frame/packet and waits for an Acknowledgment (ACK).
- Only after receiving ACK, the sender transmits the next frame.
- If ACK is not received within a timeout period, the frame is retransmitted.
For N data packets sent, N acknowledgments are required (e.g., 10 packets require 10 ACKs).
- TCP Three-Way Handshake
- A mechanism used by TCP (Transmission Control Protocol) to establish a connection.
- Purpose: To establish a reliable, connection-oriented session and synchronize initial sequence numbers.
- Steps: Client sends SYN (Synchronize 1. Sequence Number). Server responds with SYN2. ACK (Synchronize-Acknowledge). Client sends ACK (Acknow3. ledge).
- After the third step, the connection is established for data transfer.
Baseband Transmission
- Uses the entire bandwidth of a channel for a single digital signal.
- Transmits digital signals directly without modulation.
- Only one signal can be transmitted at a time; Time Division Multiplexing (TDM) can be used.
- Primarily used for Local Area Networks (LANs).
Example
Classic Ethernet (data rates typically 10 Mbps to 1000 Mbps, e.g., Fast Ethernet 100 Mbps, Gigabit Ethernet 1000 Mbps).
Broadband Transmission
- Divides the total bandwidth into multiple, independent frequency channels using Frequency Division Multiplexing (FDM).
- Transmits analog signals; digital data must be modulated onto analog carrier waves.
- Allows simultaneous transmission of multiple signals (e.g., voice, data, video) across different channels.
- Offers high-capacity communication bandwidth.
Cables
Utilized by coaxial cables and fiber optic cables.
Convergence Technology
Supports simultaneous transfer of voice, data, and video.
Examples
Cable television, DSL, fiber optic internet.
Circuit Switching
Establishes a dedicated, physical path/channel for the entire duration of communication.
Circuit Switching
Resources are reserved and unavailable to other users during the connection.
Circuit Switching
Operates at the Physical Layer (OSI Model).
Circuit Switching
Guarantees bandwidth and Quality of Service (QoS).
Circuit Switching
Used by Public Switched Telephone Network (PSTN).
Packet Switching
Data is divided into smaller units called packets.
Packet Switching
Packets include source/destination addresses and sequence numbers, travel independently, and can take different paths.
Packet Switching
Resources are shared dynamically, leading to more efficient bandwidth utilization.
- Message Switching Data (messages) are stored at intermediate nodes and forwarded (store-and-forward) in their entirety.
Router
Transfers data packets between different computer networks (operates at Network Layer).
Switch (Network Device)
Learns MAC addresses of connected devices and forwards data only to the correct intended port (operates at Data Link Layer).
Hub
Broadcasts incoming data to all connected ports (operates at Physical Layer).
Spanning Tree Protocol (STP)
Minimizes redundant packet transmission in broadcast communication by preventing network loops.
TCP Protocol
Reduces its sending rate when network congestion is detected (congestion control mechanism).
Packets
Smaller chunks into which data is divided for transmission over a network.
Frame
A data unit at the Data Link Layer; encapsulates a network layer packet.
- Three-stage
Switch
Cross-points
Calculation For a switch with N input lines, divided into n-line groups, and k switches in the middle stage, the total cross-points can be calculated. For N=200, n=20, k=4, total cross-points = 2000.
IPv6 Address Size
128 bits.
L-root Server
Rajasthan became the first Indian state to host an L-root server.
Bandwidth
The maximum theoretical data transfer rate of a network medium or channel. It represents the capacity of a link and is measured in bits per second (bps, Kbps, Mbps, Gbps). Colloquially, it's the amount of data transmitted for a given amount of time.
Throughput
The actual data transfer rate achieved over a network link under real-world conditions. It is always less than or equal to bandwidth due to factors like latency, noise, and network congestion.
Latency (Propagation Delay)
The time taken for a signal or data packet to travel from the source to the destination.
- Calculation: `Latency = Distance / Speed of Signal` (e.g., speed of light in the medium).
- Example: For a distance of 12,000 km and a signal speed of 2.4 x 10^8 m/s, the propagation time is 50 ms.
Transmission Time
The time taken to push the entire message or data block onto the transmission medium.
- Calculation: `Transmission Time = Message Size (in bits) / Bandwidth (in bps)`.
- Example: For a 2.5 kbyte message (20480 bits) and a bandwidth of 1 Gbps (10^9 bps), the transmission time is approximately 0.02 ms.
Fibre Optic Cable
Supports the highest bandwidth and longest transmission distances among common wired media.
Coaxial Cable
Offers moderate bandwidth.
CAT-5 UTP Cable (Unshielded Twisted Pair)
Offers lower to moderate bandwidth compared to fiber and coaxial cables.
3G
Capable of handling data around 1-2 Megabits per second (Mbps), typically
frequency band.
4G (LTE)
Expected speeds typically range from 100 Mbps (for mobile devices) to 1 Gigabit per second (Gbps) (for stationary access), commonly utilizing frequency bands in the 2-8 GHz range.
- Voice/Telephonic
Communication
Bandwidth The bandwidth required for speech signals in telephonic communication is approximately 4 kHz (e.g., 2800 Hz to 4.2 kHz range).
Internet Speed Measurement
Commonly expressed in units of bits per unit time, such as bits per second (bps), Kilobits per second (Kbps), Megabits per second (Mbps or Mb/sec), or Gigabits per second (Gbps).
CIDR (Classless Inter-Domain Routing)
- The `/n` notation indicates that the first `n` bits of the IP address are used for the network portion.
- The remaining `32-n` bits are reserved for the host portion.
- The total number of available IP addresses within a CIDR block (network size) is `2^(32-n)`.
- Example: For `/27`, `32-27 = 5` host bits, so `2^5 = 32` addresses are in the network.
- Example: For `/24`, 24 bits are used for the network portion.
Network Address Calculation
To determine the network address of a subnet, perform a bitwise AND operation between the IP address and its subnet mask.
- Example: For IP
corresponds to `/28`), the network address is
Data Communication Components
Message, Sender, Receiver, Transmission Medium, Protocol.
Basic Communication System Sequence
Information Source → Transmitter → Channel → Receiver → User of information.
Modem (Modulator-Demodulator)
Converts digital signals to analog (modulation) and vice versa (demodulation); connects computers to telephone lines for internet.
Transmission Mediums
Telephone lines, Coaxial cable, Fibre optic, Microwave systems, Satellite systems.
Hub
Broadcasts data to all connected devices.
Switch
Forwards data to specific destination port based on MAC address (Layer 2).
Router
Connects different networks, forwards packets based on IP addresses (Network Layer/Layer 3), handles complex routing.
Repeater
Regenerates signals to extend network distance (Physical Layer/Layer 1).
Multiplexer
Combines multiple data streams into one for transmission.
- OSI
Model
(Open
Systems
Interconnection) A 7-layer conceptual model for network communication. 1.
Physical Layer (Layer 1)
Bit-by-bit delivery, hardware specifications (e.g., cables, repeaters). 2.
Data Link Layer (Layer 2)
Framing, MAC addressing (48 bits), error control, flow control. Associated with IEEE 802.3 (Ethernet). 3.
Network Layer (Layer 3)
Logical addressing (IP address), routing (e.g., routers), packet fragmentation. Protocols: IP, ICMP, ARP. 4.
Transport Layer (Layer 4)
Process-to-process delivery, port numbers (16-bit), reliable data transfer (TCP), flow control, congestion control. Protocols: TCP, UDP. 5.
Session Layer (Layer 5)
Manages sessions between applications. 6.
Presentation Layer (Layer 6)
Data translation, encryption, compression. 7.
Application Layer (Layer 7)
Provides network services to applications. Protocols: HTTP, HTTPS, FTP, SMTP, DNS, SNMP, DHCP, RPC.
TCP/IP Reference Model Layers
Application, Transport (Host-to-Host), Internet, Network Access.
Protocols
- HTTP
(Hypertext
Transfer
Protocol) Application-layer protocol for hypermedia documents; used by web browsers and servers.
HTTPS (Hypertext Transfer Protocol Secure)
Secure version of HTTP using SSL/ TLS for encrypted communication.
FTP (File Transfer Protocol)
Application-layer protocol for file transfer.
SMTP (Simple Mail Transfer Protocol)
Application-layer protocol for sending email (Port 25).
DNS (Domain Name System)
Application-layer protocol to map domain names to IP addresses; queries typically use UDP.
- SNMP
(Simple
Network
Management Protocol) Application-layer protocol for managing/monitoring network devices.
- DHCP
(Dynamic
Host
Configuration Protocol) Application-layer protocol for automatic IP address assignment to clients.
RPC (Remote Procedural Call)
Application-layer protocol for executing procedures on remote systems.
IP (Internet Protocol)
Network-layer protocol for addressing and routing.
ICMP (Internet Control Message Protocol)
Network-layer protocol for network diagnostics and error messages.
ARP (Address Resolution Protocol)
Network-layer protocol to resolve IP addresses to MAC addresses.
- TCP
(Transmission
Control
Protocol) Transport-layer, connection-oriented, reliable. Sockets comprise IP address and a 16-bit port number.
UDP (User Datagram Protocol)
Transport-layer, connectionless, unreliable. Used by NFS, DNS, SNMP. Does not provide inherent reliability.
- RTP
(Real-time
Transport
Protocol) Application/Transport layer protocol for real-time media.
- WAP
(Wireless
Application
Protocol) Protocol for mobile internet access.
IPv4
32-bit address. 'Total length' field is 16 bits. 'Fragment Offset' field is 13 bits. Fragmentation/reassembly uses 'More Fragments' flag and 'Fragment Offset' fields.
IPv6
128-bit address.
IPv4 Address Classes
Class A (1-126 first octet), Class B (128-191 first octet), Class C (192-223 first octet). Each octet 0-255.
CIDR (Classless Inter-Domain Routing)
Flexible IP address allocation.
Subnetting
Dividing a network into smaller subnets. To get 'N' subnets, need 's' bits where 2^s >= N. (e.g., 64 subnets for Class B requires 6 subnet bits, mask
= 2^host_bits - 2.
Bus
Devices share a single communication line.
Ring
Devices connect in a loop; data flows unidirectionally.
Star
All devices connect to a central hub/ switch.
Mesh
Every device connects to every other device (n-1 ports for n devices); highest reliability due to redundant paths. Number of connections in complete mesh (Kn) = n*(n-1)/2.
LAN (Local Area Network)
Wireless LAN (WLAN) or Wi-Fi (Wireless Fidelity). Limited geographic area, high data rates, low cabling cost, full-time local connectivity.
WAN (Wide Area Network)
Spans large geographic areas; hardware includes multiplexers and routers.
LTE (Long-Term Evolution)
4G wireless broadband standard, >100 Mbps peak downlink rate.
VoLTE (Voice over Long-Term Evolution)
Enables voice calls over 4G LTE data network.
Wi-Fi 6 (802.11ax)
Next-gen Wi-Fi standard. Nokia partnered with TATA Play Fiber for India's first WiFi6ready network.
Short-Range Devices
RFID (Radio Frequency Identification), Wireless Local Area Network (Wi-Fi).
Data Encapsulation Order (OSI)
Segment (Transport) → Packet (Network) → Frame (Data Link) → Bits (Physical).
ARQ (Automatic Repeat reQuest)
Achieves reliability; retransmits lost/corrupted frames. Stop-and-Wait ARQ uses modulo-2 sequence/acknowledgment numbers and timeout retransmission.
Slotted ALOHA Throughput
`G * e^(-G)`.
Probability (1 station transmits)
`n * p * (1-p)^(n-1)`.
- Carrier Sense protocols
(e.g.,
CSMA/CD, CSMA/CA for Wi-Fi)
enhance channel utilization by
sensing
before
transmitting,
reducing collisions.
- Ethernet Uses IEEE 802.3 standard. Broadcast destination MAC address: FF:FF:FF:FF:FF:FF.
NAV (Network Allocation Vector)
Associated with Wi-Fi (CSMA/CA).
EDI (Electronic Data Interchange)
Standardized electronic exchange of business documents.
HTTP 404 Error
Standard response code indicating the requested web page was not found on the server.
MPEG (Moving Picture Experts Group)
Develops standards for digital audio/video compression.
Decoding
Receiver interprets symbols from the source message.
STD (Subscriber Trunk Dialing)
First connected Kanpur and Lucknow (1960). STD barring code: "124 ABCD 0".
Arvi
Site of India's first OCS satellite earth station.
First Modern Telecommunication Device
Telegraph.
Video Conferencing
Primarily via IP Networks.
Spanning Trees (Complete Graph K_n)
Cayley's formula: n^(n-2). For K5, 125 spanning trees.
Data Flow Directions (Simplex, Half-Duplex, Full-Duplex)
- Simplex Mode: Data communication in one direction only (unidirectional). The sender can transmit, but the receiver cannot reply.
- Examples of Simplex: Television (TV) transmission, Radio broadcasting, Loudspeaker, Keyboard to computer input.
- Broadcasting (e.g., TV/Radio) refers to sending a packet/data to all destinations simultaneously, typically a simplex operation.
- Half-Duplex Mode: Data communication in both directions, but not simultaneously. Devices take turns sending and receiving.
- Examples of Half-Duplex: Walkie-talkie.
- Full-Duplex Mode: Data communication in both directions simultaneously (bidirectional). Both devices can send and receive at the same time.
- Examples of Full-Duplex: Mobile phone, Telephone conversation.
Guided Transmission Media
Physical medium through which signals are transmitted.
Twisted-Pair Cable
- Consists of two insulated copper wires twisted together to reduce electromagnetic interference.
- Types: Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP).
- Relatively lower data transfer speed and bandwidth compared to coaxial and optical fibre.
- More susceptible to noise and crosstalk than other guided media.
- Coaxial Cable
- Features a central copper conductor surrounded by an insulating layer, a braided metal shield, and an outer jacket.
- Uses electrical signals for data transmission.
- Offers higher data transfer speed and better noise immunity than twistedpair, but slower than optical fibre.
Optical Fibre Cable (OFC)
- Transmits data using light pulses (laser light or LED light) through thin strands of glass or plastic.
Fastest mode of transmission media with the highest data transfer speed and highest bandwidth.
transfer speed and highest
bandwidth.
- Immune to electromagnetic interference (EMI); thus, it is less noisy and experiences no electric or magnetic noise.
- Generally more expensive to install than copper cables (twisted-pair, coaxial).
- Possesses a longer life-time.
- Provides high connectivity, supporting a larger number of telephones or data streams.
- Narinder Kapany, an Indian-born American physicist, is widely credited as the "Father of Fiber Optics."
- It is a guided (wired) networking technology, unlike wireless technologies like Bluetooth, Wi-Fi, or WLAN.
- Major Optical Fibre Cable (OFC) Projects/ Details
Andaman & Nicobar Submarine OFC
Connected Andaman & Nicobar Islands to mainland (Chennai) in August 2020.
- Initially connected islands include Port Blair, Swaraj Dweep (Havelock), Shaheed Dweep (Neil), Little Andaman, Car Nicobar, Kamorta, Great Nicobar, Long Island, and Rangat.
MIST (Myanmar-India-Singapore Transit) Cable System
A proposed submarine cable system with a length of 8100 kilometers.
Multiplexing
Technique to combine multiple data streams into one signal over a shared medium to improve channel utilization.
1. Frequency Division Multiplexing (FDM)
- Analog multiplexing technique.
- Divides total bandwidth into non-overlapping frequency channels.
- Each signal assigned a unique frequency band.
- Guard bands separate channels to prevent interference.
- Applications: Analog radio/TV broadcasting, first-generation cellular telephony (AMPS).
- Frequency Modulation (FM) is a modulation technique used for high-fidelity audio signals (e.g., TV audio, radio) within FDM channels.
2. Time Division Multiplexing (TDM)
- Digital multiplexing technique (can carry digitized analog signals).
- Divides transmission time into fixedduration time slots.
- Each input signal assigned a unique, recurring time slot.
- More efficient for digital data than FDM.
- Applications: Digital telephony (Tcarrier, E-carrier systems), ISDN.
Time Division Multiple Access (TDMA)
A channel access method based on TDM.
- Allows multiple users to share a single frequency channel by dividing it into time slots.
- Users transmit in assigned time slots.
- Core technology in GSM (Global System for Mobile Communications).
- Primarily used in wireless communication systems.
3. Wavelength Division Multiplexing (WDM)
- Optical fibre equivalent of FDM.
- Multiplexes multiple optical carrier signals (different wavelengths/colors of light) onto a single optical fiber.
- Each wavelength carries a separate data channel.
- Applications: High-capacity fiberoptic communication systems for longhaul and metro networks.
Broadcast Network
A network where all connected machines share a single communication channel.
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance)
Multiple access protocol primarily used in wireless networks (e.g., Wi-Fi) as collision detection is difficult. Not suitable for wired networks.
- CSMA/CD
(Carrier
Sense
Multiple Access with Collision
Detection) Multiple access protocol used in wired Ethernet LANs.
Data Transmission Modes
Methods of transferring data between devices.
Serial Transmission
Bits sent sequentially over a single communication channel.
Characteristics
Simpler wiring, lower cost, suitable for long distances, generally slower.
Applications
USB, Ethernet, traditional telegraphy.
Parallel Transmission
Multiple bits sent simultaneously over multiple communication channels (e.g., 8 bits over 8 wires).
Characteristics
Complex wiring, higher cost, suitable for short distances, generally faster.
Applications
Internal computer buses, older printer ports.
Morse Code
A serial data encoding scheme using sequences of dots and dashes to represent text characters.
Primary Use
Telegraphy (e.g., Telegram service).
Murray Code (Baudot Code)
An early character set developed for teleprinter machines (teletypes).
Bit Representation
Uses a 5-bit code to represent characters.
Transmission Impairments (Attenuation, Distortion, Noise)
- Transmission Impairments: Factors degrading signal integrity during transmission.
- Attenuation:
- Loss of signal energy/strength over distance as it travels through a medium.
- Occurs due to medium's resistance, leading to energy dissipation.
- Effect: Signal weakens, becomes harder to interpret.
- Mitigated by: Amplifiers (analog signals), repeaters (digital signals).
- Distortion:
- Change in the signal's original waveform or shape.
- Delay Distortion: Different frequency components of a signal travel at different speeds, arriving at different times, causing phase shifts. Predominant in guided media.
- Effect: Alters signal waveform, leading to interpretation errors.
- Noise:
- Unwanted signals added to the original signal.
- Effect: Corrupts data, reduces Signalto-Noise Ratio (SNR).
- Thermal Noise (White Noise): Random motion of electrons; unavoidable, uniformly distributed across frequencies.
- Intermodulation Noise: Different frequencies sharing a medium create sum/difference frequencies that interfere with the signal.
- Crosstalk: Signal from one wire/circuit spills over into an adjacent wire/ circuit.
- Impulse Noise: Short-duration, highamplitude spikes (e.g., lightning, power surges, faulty equipment).
- Resilience: The ability of a computer network to recover from errors (e.g., connection failure, data loss) and maintain service.
- Cyclic Redundancy Check (CRC): An error detection method used to detect accidental changes to raw data. It appends a short checksum to a block of data.
- Network Congestion: Occurs when network traffic exceeds network capacity (traffic overloading), leading to delays, packet drops, and retransmissions.
Unguided Transmission Media (Radio Waves, Microwaves, Infrared)
- Unguided transmission media transmit electromagnetic waves without physical conductors.
- Wireless communication relies on radio signals or infrared signals for data transmission.
- Radio Waves:
- Used for various wireless communications, including Bluetooth and WiMAX.
- Bluetooth technology enables short-range wireless communication between devices using radio waves (IEEE 802.15).
- WiMAX technology is based on the IEEE 802.16 standard.
- FM broadcast services utilize the frequency range of 88-108 MHz.
- Sky waves are suitable for communication in the frequency range generally up to 40 MHz (e.g., 15 MHz), reflecting off the ionosphere.
- Space waves are used for line-of-sight (LOS) communication as well as satellite communication, penetrating the ionosphere (typically above 40 MHz).
- The 4th generation (4G) mobile telecommunication service, using TD-LTE, was first launched in India in Kolkata.
- Microwaves:
- Microwaves are a type of electromagnetic wave used in telecommunication, radar, and satellite communication.
- Microwaves used in artificial satellites for communication have a frequency range of 300 MHz to 300 GHz.
6. Internet, Intranet, and Extranet
Practice MCQs: Data Communication and Transmission Modes
Analog and Digital Data and Signals
The form of information signal used in sending fax and email is,
Asked in: JPSC CS Prelims 2021
- Analog signal
- Digital signal
- Analog and Digital signal both
- None of Analog and Digital signal
Show answer
Answer: B. Digital signal
- Email transmission uses digital signals exclusively. - Traditional fax used analog signals for transmission over phone lines. - Modern fax technologies use digital signals and methods, or digitize content before transmission. - Information processed by computers (like content of email/fax) is in digital form.
The primary use of scramblers in Line Coding Schemes is to - - (5) Question not attempted
Asked in: Programmer Exam 2024
- make the data look random
- compress transmission data
- decrease signal bandwidth
- increase signal bandwidth
Show answer
Answer: A. make the data look random
B. upgrading hardware components without reinstalling the operating system C. only one operating system to run on a single physical machine D. running multiple operating systems on a single physical machine simultaneously Ans: D GS CompOp 07 2024 1009-2024 Virtualization enables the consolidation of resources and the running of multiple operating systems on one physical server. The primary role of scramblers in line coding is to introduce randomness into the data stream, which is essential for synchronization and signal integrity.
A technique used by codes to convert an analog signal into a digital bit stream is known as
Asked in: Assistant Engineer (AE) Exam 2012
- Pulse code modulation
- Pulse stretcher
- Query processing
- Queue management
Show answer
Answer: A. Pulse code modulation
Pulse Code Modulation (PCM) is the most common method used to digitally represent sampled analog signals. It involves three main steps: sampling, quantization, and encoding.
'MODEM' is used for -
Asked in: Civil Judge 2022
- A/D conversion only
- D/A conversion only
- Both A/D & D/A conversion
- None of the above
Show answer
Answer: C. Both A/D & D/A conversion
The core function of a modem is to enable digital devices to communicate over analog communication channels by translating signals between digital and analog formats.
The demodulation of a delta-modulated signal is achieved by differentiation sampling integration band-pass filtering
Asked in: GS&EI ElectEngg 14 2024 1601 2025
- differentiation
- sampling
- integration
- band-pass filtering
Show answer
Answer: C. integration
Delta modulation works by transmitting the difference between consecutive samples. The transmitter quantizes this difference, and the receiver integrates these quantized differences to reconstruct the original signal. The process in the transmitter can be thought of as a form of differentiation (change in signal), and the process in the receiver is integration (summing the changes).
Analog and Digital Transmission
Which one of the following pairs is the third generation (3G) mobile telecommunication?
Asked in: APSC CCE Prelims Exam 2016
- WiMAX and UMTS
- GPRS and EDGE
- WiMAX and EDGE
- UMTS and GPRS
Show answer
Answer: D. UMTS and GPRS
- UMTS (Universal Mobile Telecommunications System) is the primary 3G standard based on W- CDMA technology, offering significantly higher data speeds than 2G. - WiMAX (Worldwide Interoperability for Microwave Access), based on the IEEE 802.16 standard, is often categorized as a 4G technology or a pre-4G technology, but early discussions and deployments sometimes overlapped or competed with 3G networks as alternative mobile broadband solutions.
Which of the following statements is/are correct regarding VoLTE technology used by mobile network? 1. It allows transmission of data through a 4G network while voice calls are routed through older 2G or 3G networks. 2. It counts voice calls as per data usage rather than minutes of usage.
Asked in: GPSC Prelims CSP 2 2019
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer
Answer: B. 2 only
- VoLTE transmits voice calls as data over the 4G LTE network. - It replaces older circuit-switched voice technology. - Voice in VoLTE is packetized data.
Which of the following statements is/are correct regarding 4G LTE telecom in India? (A) Currently in India, 4G LTE band-40 having 2300 to 2400 MHz (TD-LTE) frequency range is active (online) (B) LTE band in 1800 MHz (FDD-LTE) frequency is also auctioned by the government
Asked in: GPSC Prelims CSP 2 2022
- Currently in India, 4G LTE band-40 having 2300 to 2400 MHz (TD-LTE) frequency range is active (online)
- LTE band in 1800 MHz (FDD-LTE) frequency is also auctioned by the government
- Both (A) and (B)
- Neither (A) nor (B)
Show answer
Answer: C. Both (A) and (B)
- Statement (A) is correct. In India, 4G LTE services utilize different frequency bands. Band 40 (2300 MHz) is a prominent band, particularly used for TD-LTE (Time Division Duplex) technology, and is widely deployed by operators like Reliance Jio for providing 4G services. This band is indeed active and online across India. - Statement (B) is correct. The 1800 MHz band (Band 3) is another important frequency band used for FDD-LTE (Frequency Division Duplex) technology in India. This band has been regularly auctioned by the Department of Telecommunications (DoT), Government of India, and is used by various operators (like Airtel, Vodafone Idea) for their 4G services.
Which of the following statements are correct regarding VoLTE? 1. VOLTE stands for ‘Voice over Long Term Evolution’ 2. It is a digital packet voice service delivery over IP via an LTE access network. 3. Provides more efficient use of spectrum than traditional Voice 4. Eliminates the need to have Voice on one network and data on another
Asked in: GPSC Prelims CSP 2 2022
- 2, 3 and 4 only
- 1, 2 and 3 only
- 1, 3 and 4 only
- All of the above
Show answer
Answer: D. All of the above
VoLTE stands for Voice over Long Term Evolution. It delivers voice calls as data packets over an IP network using the LTE infrastructure (Statement 1 and 2). It is more spectrally efficient than traditional circuit-switched voice technologies used in 2G and 3G networks (Statement 3). By integrating voice into the LTE data network, it eliminates the need for devices to switch to older networks (like 2G or 3G) for voice calls, allowing simultaneous high-speed data and voice on the same network (Statement 4).
The process of superposition of any information on radiowaves is named as
Asked in: JPSC CS Prelims 2024
- transmission
- modulation
- demodulation
- reception
Show answer
Answer: B. modulation
Modulation is the process of varying one or more properties of a carrier wave (like amplitude, frequency, or phase) with a signal that carries information. This process is essential for transmitting signals over long distances via radio waves.
Ethernet is an example of
Asked in: MPPSC CS Prelims 2017
- MAN
- LAN
- WAN
- Wi-Fi
Show answer
Answer: B. LAN
LAN (Local Area Network) connects computers and devices within a limited area, such as a home, school, or office building. Ethernet provides the physical and data link layer specifications for wired connections within such a network.
A modem converts
Asked in: MPPSC CS Prelims 2017
- analog signals into digital signals
- digital signals into analog signals
- Both (A) and (B)
- None of the above
Show answer
Answer: C. Both (A) and (B)
Modulation is the process of converting digital signals (from a computer) into analog signals for transmission over analog communication lines (like telephone lines). Demodulation is the process of converting received analog signals back into digital signals for the computer.
Asynchronous vs. Synchronous Transmission Modes
For Stop-and-Wait ARQ, for 10 data packets sent, ....................acknowledgements are needed.
Asked in: Programmer Exam 2024
- 11
- 9
- 10
- 20
Show answer
Answer: A. 11
In the Stop-and-Wait ARQ protocol, acknowledgements are sent by the receiver for each data packet it successfully receives. - For every data packet sent and received, a corresponding acknowledgement is generated. - If 10 data packets are sent and successfully received, the receiver will generate 10 acknowledgements. - The option '11' suggests an additional acknowledgement is needed, often related to connection termination (e.g., acknowledging a FIN packet after data transfer is complete). If the question implies the entire sequence including termination, then 11 is plausible.
The three-way handshake mechanism in TCP aims to - - (5) Question not attempted
Asked in: Programmer Exam 2024
- secure the communication.
- send bits from one device to another over an optical fibre connection.
- perform error detection and correction.
- establish connection and synchronize sequence numbers.
Show answer
Answer: D. establish connection and synchronize sequence numbers.
The three-way handshake is primarily for connection establishment and sequence number synchronization. While it lays the groundwork for reliable communication, it doesn't directly provide security (encryption) or perform error detection and correction itself (though TCP segments have checksums for error detection).
Baseband vs. Broadband Transmission Modes
What are the data rates typically associated with classic Ethernet? - Question not attempted
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- 1 to 3 Mbps
- 100 to 1000 Mbps
- 10 to 1000 Mbps
- 3 to 10 Mbps
Show answer
Answer: C. 10 to 1000 Mbps
"Classic Ethernet" typically refers to the original implementations and common standards that evolved from the early days of Ethernet up to the widespread adoption of Gigabit Ethernet.- Original Ethernet (10BASE-T) Operated at 10 Mbps. - Fast Ethernet (100BASE-TX) Operated at 100 Mbps. - Gigabit Ethernet (1000BASE-T) Operates at 1000 Mbps (1 Gbps).While very early forms might have been lower, and modern Ethernet can go much higher (10 Gbps, 40 Gbps, 100 Gbps and beyond), the range that is commonly associated with "classic" Ethernet, encompassing the evolution from 10 Mbps to Gigabit speeds, is 10 to 1000 Mbps.
In..................., the entire bandwidth is used as one single dedicated channel.
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- (1) WAN
- (2) LAN
- (3) Satellite Network
- (4) Wireless Sensor Network
Show answer
Answer: C. (3) Satellite Network
- Satellite networks use a dedicated channel (transponder) for wide-area communication. - This dedicated channel utilizes the entire allocated bandwidth for its purpose. - Other network types (WAN, LAN, WSN) generally involve more distributed or shared resource usage.
High-capacity communications bandwidth that is used by coaxial cables and fiber optic cables is known as
Asked in: GS CompApp RA 09 2024 1009 2024
- hyperlink
- broadband
- bus width
- barrier wave
Show answer
Answer: B. broadband
Broadband refers to high-speed internet access that is always on and faster than traditional dial-up access. It is characterized by high bandwidth, which allows for the transmission of large amounts of data quickly.
Broadband convergence technology is used for ________ transfer.
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- Voice, data and video
- Only voice
- Only video
- Only data
Show answer
Answer: A. Voice, data and video
Broadband technology integrates different communication services onto a single network infrastructure, enabling the seamless transfer of various forms of digital information.
Basic Switching Techniques (Circuit, Packet, Message Switching)
A ____ is used to transfer data packets between two computer networks.
Asked in: MPPSC CS Prelims 2021
- Switch
- Router
- Brouter
- Gateway
Show answer
Answer: B. Router
Routers are network devices that operate at Layer 3 (Network Layer) of the OSI model. They analyze the destination IP address of incoming data packets and use routing tables to determine the best path to forward the packet to its destination network. This function is essential for connecting different networks, such as a home network to the internet, or different subnets within an organization.
What advantage does a spanning tree offer in broadcast communication? - Increases packet size - Minimizes the number of packets used in a broadcast - Decreases packet size - Maximizes the number of packets used in a broadcast - Question not attempted
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- (1) only
- (2) only
- (3) only
- (4) only
Show answer
Answer: B. (2) only
In broadcast communication, a spanning tree is a subgraph that connects all nodes in a network without creating any cycles. In the context of network protocols like spanning tree protocols (STP) used in Ethernet networks, a spanning tree is essential for preventing loops in networks with redundant paths.When a broadcast frame is sent, it needs to reach all connected devices. However, if there are multiple paths, the frame could loop indefinitely, leading to network congestion and instability. A spanning tree algorithm ensures that there is only one active path from any source to any destination, effectively creating a single, logical broadcast domain. By preventing redundant paths and thus avoiding multiple copies of the broadcast reaching the same node via different routes, a spanning tree minimizes the number of times a broadcast packet is processed and forwarded, ensuring it reaches all intended recipients exactly once and avoids loops.The other options are incorrect: - Increasing or decreasing packet size is not a primary function of a spanning tree. - Maximizing the number of packets used in a broadcast would be detrimental to network performance.
The TCP protocol............when it detects congestion in the network. - Question not attempted
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- aborts the connection
- repeats the packets from the current window
- encrypts the packets
- reduces the sending rate
Show answer
Answer: D. reduces the sending rate
TCP (Transmission Control Protocol) is designed to provide reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating over an IP network. Congestion control is a crucial mechanism within TCP. When TCP detects congestion in the network (e.g., through packet loss, increased round- trip times), its primary response is to reduce its sending rate. This is done to alleviate the congestion and prevent further packet loss.Common TCP congestion control algorithms like Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery are all designed to dynamically adjust the sending rate based on network conditions.
Circuit switching takes place at the ................................
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- (1) Network Layer
- (2) Application Layer
- (3) Physical Layer
- (4) Data Link Layer
Show answer
Answer: C. (3) Physical Layer
- Circuit switching establishes a dedicated end-to- end path. - This path is physical in nature. - The Physical Layer is responsible for bit transmission and physical connection establishment.
Consider a single-stage switch (200 x 200) with number of input lines (N) as 200, the number of crossbars (k) in the middle stage is 4 and the N input lines are divided into groups, each of n lines, consider n=20. The total number of cross points in a three-stage switch for the given data is -
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- 1000
- 10000
- 2000
- 20000
Show answer
Answer: C. 2000
The total number of cross points in a three-stage switch, with N input lines, divided into groups of n lines, and k crossbars in the middle stage, is typically calculated as 2Nk + k(N/n)^2.
Which of the following is true for Circuit Switching handling multiple simultaneous connections?
Asked in: Programmer Exam 2024
- A single path is used and shared for all data
- It encodes all data into a single channel
- Separate physical paths are allocated for each channel
- All connections are multiplexed into a single channel
Show answer
Answer: C. Separate physical paths are allocated for each channel
- Circuit Switching A connection-oriented switching technique where a dedicated communication path (circuit) is established between the source and destination before data transmission. Once established, this path remains dedicated to the connection. Examples include traditional telephone networks. - Packet Switching A connectionless or connection-oriented technique where data is broken into packets, and each packet is routed independently across the network. Paths are not dedicated and are shared among multiple users. Examples include the internet. - Simultaneous Connections In circuit switching, each connection requires its own dedicated path to ensure quality of service and prevent interference.
_____ is aware of the addresses assigned to each of its ports and sends the incoming data it receives only to the correct port.
Asked in: ae 2025
- Hub
- Switch
- Repeater
- Modem
Show answer
Answer: B. Switch
A network switch uses MAC addresses to forward data packets directly to the intended recipient port.
Channel Capacity and Bandwidth
3G and 4G are wireless technologies, which are supposedly faster, more secure and reliable. Present day 3G technology is capable of handling data around 2 Megabits per second (1.8 - 2.5 GHz frequency band). What speed is expected from new 4G technology ?
Asked in: UPSC CAPF 2014
- 10-30 Megabits per second (1-5 GHz frequency band)
- 10-100 Megabits per second (2-10 GHz frequency band)
- 100 Megabits—1 Gigabit per second (2-8 GHz frequency band)
- More than 10 Gigabits per second (10-20 GHz frequency band)
Show answer
Answer: C. 100 Megabits—1 Gigabit per second (2-8 GHz frequency band)
The question asks about the expected speed from new 4G technology compared to 3G (around 2 Mbps). 4G, specifically LTE (Long-Term Evolution), was designed to provide significantly higher data rates. While real-world speeds vary greatly depending on network conditions and load, the theoretical peak speeds and design targets for 4G are much higher than 3G. LTE (4G) typically aims for peak downlink speeds of 100 Mbps for high-mobility users and up to 1 Gbps for low-mobility users (in advanced versions like LTE-Advanced). Peak uplink speeds are lower, typically up to 50 Mbps. Comparing the options: A) 10-30 Mbps: Only slightly better than 3G, too low for 4G targets. B) 10-100 Mbps: Covers the lower end of 4G peak downlink but doesn't capture the higher potential. C) 100 Megabits—1 Gigabit per second: This range accurately reflects the peak theoretical speeds achievable by 4G and LTE-Advanced technologies, particularly the upper bound in ideal conditions. D) More than 10 Gigabits per second: This speed range is characteristic of 5G technology, not 4G. The frequency band mentioned (2-8 GHz) is also plausible for 4G deployments, although 4G uses various bands depending on the region and spectrum availability.
Which one of the following communication media supports higher bandwidth ?
Asked in: UPSC CISF AC EXE 2018
- Coaxial cable
- Fibre optic cable
- CAT-5 UTP cable
- Electrical cable
Show answer
Answer: B. Fibre optic cable
- Higher bandwidth means the medium can transmit more data per unit of time. - Fibre optic cables use light signals to transmit data along glass or plastic fibres, offering extremely high speeds and large bandwidths over long distances. - Coaxial and UTP (Unshielded Twisted Pair) cables use electrical signals over copper wires, with lower bandwidth limitations compared to fibre optics.
Data transmitted for a given amount of time is called _____.
Asked in: WBCS Main Paper 4 2019
- Noise
- Power
- Frequency
- Bandwidth
Show answer
Answer: D. Bandwidth
While the phrase "data transmitted for a given amount of time" directly describes data rate or throughput, among the given options, bandwidth is the term that quantifies the capacity of a communication channel, indicating the maximum amount of data that can be transmitted over a unit of time. A larger bandwidth allows for a higher data rate.
What is the propagation time and transmission time for a 2.5-kbyte message (an e-mail), if the bandwidth of the network is 1 Gbps? Assume that the distance between the sender and the receiver is 12,000 km and that light travels at $2.4 \times 10^8$ m/s.
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- 0.02 ms, 50 ms
- 50 ms, 0.02 ms
- 10 ms, 20 ms
- 30 ms, 0.40 ms
Show answer
Answer: B. 50 ms, 0.02 ms
- Propagation time depends on the physical distance and the speed of signal propagation. - Transmission time depends on the size of the data and the bandwidth of the link. - Units must be consistent for calculations (e.g., meters for distance, bits for data size, seconds for time).
Which of the following best describes the difference between bandwidth and throughput? - Bandwidth refers to packet size and throughput refers to latency. - Bandwidth is a theoretical maximum while throughput is the actual achieved data rate. - Throughput is measured in Hz while bandwidth is measured in bps. - Bandwidth is affected by latency while throughput is not.
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- Statement 1 and 2
- Statement 2 and 3
- Statement 2 and 4
- Statement 1 and 4
Show answer
Answer: B. Statement 2 and 3
Bandwidth is the theoretical maximum data transfer rate, whereas throughput is the actual achieved data transfer rate.
What does /24 denote in CIDR? - (5) Question not attempted
Asked in: Programmer Exam 2024
- 24 bits are used for network portion
- 24 addresses are available in the subnet
- 24 subnets are created
- 24 bits are used for host portion
Show answer
Answer: A. 24 bits are used for network portion
CIDR notation (e.g., /24) is used to represent IP address ranges and subnetting. The number after the slash indicates the length of the network prefix. residing on a sub-network with the following work address of this subnet? - (5) Question not attempted Ans: D - IP Address A unique identifier assigned to each device on a network. - Subnet Mask Used to divide an IP address into a network address and a host address. The bits set to 1 in the subnet mask correspond to the network portion, and bits set to 0 correspond to the host portion. - Network Address The first address in a subnet, which identifies the network itself. - Bitwise AND Operation To calculate the network address, a bitwise AND is performed between the IP address and the subnet mask. network, and the last 8 bits are for the host portion, with the first 4 bits of the last octet being network bits and the last 4 bits being host bits.
The bandwidth required for telephonic communication (speech signals) is -
Asked in: Protection Officer 2022
- 300 MHz
- 30 kHz
- 4.2 MHz
- 2800 Hz
Show answer
Answer: D. 2800 Hz
Speech signals occupy a specific range of frequencies in the audible spectrum. For telephonic communication, this range is typically from 300 Hz to 3400 Hz, resulting in a bandwidth of approximately 3.1 kHz. This narrow bandwidth is efficient for transmitting voice.
Components of Data Communication
Which of the following performs modulation and demodulation ?
Asked in: CGPSC Prelims Exam 2019
- Coaxial cable
- Fibre optic
- Modem
- Satellite
Show answer
Answer: C. Modem
A modem (Modulator-Demodulator) is a device that converts digital signals from a computer or other device into analog signals (modulation) for transmission over traditional analog telephone lines or cable infrastructure. It also converts incoming analog signals back into digital data (demodulation) that a computer can understand.
Which global technology leader partnered with TATA Play Fiber to launch India's first WiFi6-ready broadband network?
Asked in: GPSC Prelims CSP 2 2024
- Samsung
- Apple
- Nokia
- Huawei
Show answer
Answer: C. Nokia
Tata Play Fiber partnered with the global technology leader Nokia to launch India's first WiFi6- ready broadband network. Nokia provided its fiber- to-the-home (FTTH) and Wi-Fi 6 solutions to enable Tata Play Fiber to offer enhanced broadband experiences to its subscribers.
Consider the following statements regarding Hypertext Transfer Protocol (HTTP): Statement 1 : It is an application-layer protocol for transmitting hypermedia documents Statement 2 : It was designed for communication between web browsers and web servers
Asked in: GPSC Prelims CSP 2 2022
- Both Statements 1 and 2 are correct and state‐ ment 2 is the correct explanation for statement 1
- Both Statements 1 and 2 are correct but State‐ ment 2 is not the correct explanation for statement 1
- Statement 1 is correct but statement 2 is incor‐ rect
- Statement 1 is incorrect and statement 2 is cor‐ rect
Show answer
Answer: A. Both Statements 1 and 2 are correct and state‐ ment 2 is the correct explanation for statement 1
Statement 1 correctly defines HTTP as an application-layer protocol for transmitting hypermedia documents (like HTML pages). Statement 2 correctly states that HTTP was designed specifically for the interaction between web browsers and web servers.
IPv6 protocol defines an IP address of
Asked in: MPPSC CS Prelims 2020
- 32 bit
- 64 bit
- 128 bit
- 256 bit
Show answer
Answer: C. 128 bit
Internet Protocol version 6 (IPv6) is the latest version of the Internet Protocol, designed to replace IPv4. The main reason for the development of IPv6 was the impending exhaustion of IPv4 addresses. IPv6 addresses are significantly longer than IPv4 addresses. An IPv6 address is 128 bits long, providing a vastly larger address space compared to IPv4's 32 bits.
IP addresses are used on which layer of OSI reference model?
Asked in: UKPSC CS Prelims 2021
- Network Layer
- Application Layer
- Transport Layer
- Datalink Layer
Show answer
Answer: A. Network Layer
The Network Layer is responsible for logical addressing and routing. IP (Internet Protocol) addresses provide a unique logical identifier for each device on a network, enabling data packets to be routed across different networks from source to destination.
Wi-Fi in a computer implies
Asked in: UPSC CAPF 2012
- wired local area network
- wireless local area network
- high fidelity
- high efficiency
Show answer
Answer: B. wireless local area network
- Wi-Fi stands for Wireless Fidelity (though this is not a formally recognized term by the Wi-Fi Alliance). - It creates a Wireless Local Area Network (WLAN). - Used for connecting devices to a network wirelessly over short to medium distances.
Which one of the following protocols is not an application layer of the TCP/IP model?
Asked in: UPSC CAPF 2022
- FTP
- HTTP
- DNS
- IP
Show answer
Answer: D. IP
The TCP/IP model is a conceptual framework used to describe the functions of the networking system. It typically consists of four layers: Application Layer, Transport Layer, Internet Layer (or Network Layer), and Link Layer (or Network Interface Layer). FTP (File Transfer Protocol), HTTP (Hypertext Transfer Protocol), and DNS (Domain Name System) are all protocols that operate at the Application Layer, providing services to applications. IP (Internet Protocol) operates at the Internet Layer, responsible for addressing and routing packets across networks.
Data Flow Directions (Simplex, Half-Duplex, Full-Duplex)
Television transmission is an example of which of the following ?
Asked in: UKPSC CS Prelims 2016
- Simplex Communication
- Half-duplex Communication
- Full-duplex Communication
- None of the above
Show answer
Answer: A. Simplex Communication
GS JE PHE 29 2023 2407-2024 Television transmission is a form of communication where data flows in only one direction, from the broadcaster to the viewer. There is no return channel for the viewer to send information back through the same medium for communication purposes.
A television (TV) transmission is an example of which type of transmission?
Asked in: WBCS Main Paper 4 2023
- Simplex
- Half-duplex
- Full-duplex
- Bidirectional
Show answer
Answer: A. Simplex
Simplex transmission is a type of communication where data can only flow in one direction. In a television broadcast, the signal is transmitted from the broadcasting station to the television receiver, but no signal is sent back from the receiver to the station via the same channel.
What is broadcasting in the context of networking? - Question not attempted
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- Sending a packet based on the DNS server
- Sending a packet to a single host only
- Sending a packet to all destinations simultan‐ eously
- Sending encrypted messages to selected hosts
Show answer
Answer: C. Sending a packet to all destinations simultan‐ eously
Broadcasting is a one-to-all communication method. It is distinct from unicasting (one-to-one) and multicasting (one-to-many).
In a method of communication, if transmission happens in both directions but not simultaneously, then it is called .....................................
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- twisted pair
- simplex
- half duplex
- full duplex
Show answer
Answer: C. half duplex
Half-duplex communication allows for two-way data flow but not at the same time.
Which of the following devices is fully duplex?
Asked in: ASSISTANT SECTION OFFICER 2019
- Mobile phone
- Walky-talky
- Loudspeaker
- Radio
Show answer
Answer: A. Mobile phone
Duplex communication can be either half-duplex (communication in both directions, but only one at a time) or full-duplex (communication in both directions simultaneously).
Which communication channel is used in walkie-talkie ?
Asked in: Animal Husbandry and Veterinary Science
- Double duplex
- Full-duplex
- Half-duplex
- Simplex
Show answer
Answer: C. Half-duplex
Half-duplex communication allows for two-way communication but not simultaneously.
What do you mean by full-duplex mode ?
Asked in: Computer Programmer Examination 2021
- Sender can send message to receiver but re‐ ceiver can't send message to sender.
- Sender can message to receiver and receiver can send message to sender, but not simultan‐ eously.
- Sender can send message to receiver and re‐ ceiver can send message to sender simultan‐ eously.
- Neither sender nor receiver can exchange information with each other.
Show answer
Answer: C. Sender can send message to receiver and re‐ ceiver can send message to sender simultan‐ eously.
Full-duplex mode allows simultaneous two-way communication.
Guided Transmission Media (Twisted-Pair, Coaxial Cable, Fiber Optics)
Recently, islands of Andaman and Nicobar were connected with mainland by Submarine Optical Fibre Cable. Which one of the following islands was not connected initially?
Asked in: UPSC CDS 2 2020
- Shaheed Island
- Swaraj Island
- Little Andaman
- Port Blair
Show answer
Answer: C. Little Andaman
The project involved a main cable from Chennai to Port Blair, with branches extending from Port Blair to other islands.
Which one of the following communication media uses light pulses for carrying information?
Asked in: UPSC CISF AC EXE 2019
- Coaxial cable
- Optic fibre
- Microwave
- Satellite
Show answer
Answer: B. Optic fibre
Communication media carry information in various forms. Coaxial cables use electrical signals transmitted through copper wires. Microwave and satellite communication use electromagnetic waves (radio waves) transmitted through the air or space. Optic fibre cables, however, use light pulses transmitted through thin strands of glass or plastic. This method allows for very high bandwidth and long- distance transmission with minimal signal loss.
Which one among the following is the fastest mode of transmission media ?
Asked in: UPSC CISF AC EXE 2023
- Coaxial cables
- Twisted-pair cables
- Infrared rays
- Optical fibers
Show answer
Answer: D. Optical fibers
- Transmission media speed varies greatly depending on technology. - Optical fiber is the fastest among the options listed for data communication over distance.
Which of the following cable has highest data transfer speed?
Asked in: Head Master Praveshika School (Sanskrit Edu.) 2021
- Coaxial Cable
- Twisted Pair Cable
- Optical Fibre Cable
- Cat 6 Cable
Show answer
Answer: C. Optical Fibre Cable
This question compares the data transfer capabilities of different types of communication cables.
Which of the following is not a wireless networking technology? - (1) Optical Fibre - (2) Bluetooth - (3) Wi-Fi Hotspot - (4) WLAN
Asked in: Head Master Praveshika School (Sanskrit Edu.) 2021
- 1 only
- 2 and 4 only
- 1 and 3 only
- 1, 2, 3 and 4
Show answer
Answer: A. 1 only
Optical Fibre is a wired communication technology, unlike Bluetooth, Wi-Fi Hotspot, and WLAN which are wireless.
What is the length of the proposed MIST cable system?
Asked in: acf 2019
- 8100 kilometers
- 7100 kilometers
- 6100 kilometers
- 5100 kilometers
Show answer
Answer: B. 7100 kilometers
This is a factual question about the length of a specific undersea cable system.
Which communication method uses light signals to transfer data ?
Asked in: Assistant Conservator of Forest 2025
- Radio wave communication method
- Infrared waves communication method
- Bluetooth communication method
- Optical fiber communication method
Show answer
Answer: D. Optical fiber communication method
Optical fiber communication uses light pulses to transmit data over long distances through thin strands of glass or plastic. This method offers very high bandwidth and is less susceptible to electromagnetic interference compared to other communication methods.
Multiplexing Techniques (FDM, TDM, WDM)
The technique used to transmit audio signals in television broadcasts is
Asked in: UPPSC Upper Mains 2007
- Amplitude Modulation
- Pulse Code Modulation
- Frequency Modulation
- Time Division Multi flexing
Show answer
Answer: C. Frequency Modulation
In television broadcasting, the video signal is transmitted using Amplitude Modulation (AM), while the audio signal is transmitted using Frequency Modulation (FM). This separation of modulation techniques helps in reducing interference between the video and audio signals.
Which of the following Multiple Access Protocols is not suitable for wired networks?
Asked in: Programmer Exam 2024
- CSMA/CA
- CSMA/CD
- TGMA
- TDMA
Show answer
Answer: A. CSMA/CA
Multiple Access Protocols (MAPs) manage access to a shared network medium. - CSMA/CD (Carrier Sense Multiple Access with Collision Detection) Standard for wired Ethernet. Listens for traffic, transmits if clear, detects collisions, and retransmits. Highly suitable for wired networks. - CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Standard for wireless networks (Wi-Fi). Attempts to avoid collisions because detection is difficult in wireless. It is less efficient and not optimally designed for wired networks where collision detection is feasible. - TDMA (Time Division Multiple Access) Divides time into slots for devices. Suitable for both wired and wireless networks. - TGMA Likely a less common or obscure protocol. Without specific information, its suitability is unknown, but it's less likely to be the intended answer in a general networking question compared to the distinction between CSMA/CD and CSMA/CA.The question asks which is not suitable for wired networks. CSMA/CA is primarily a wireless protocol, making it less suitable and efficient for wired networks compared to CSMA/CD.
Which type of network shares the communication channel among all the machines?
Asked in: JUNIOR laboratory assistant 2025
- Multicast network
- Unicast network
- Broadcast network
- More than one of the above
Show answer
Answer: C. Broadcast network
In a broadcast network, data is sent to all devices on the network, utilizing a shared communication channel.
The core technology used in GSM is
Asked in: Deputy Superintendent of Police (Police Telecom) Exam 2024
- MDMA
- CDMA
- TDMA
- KDMA
Show answer
Answer: C. TDMA
TDMA is a channel access method used in digital cellular systems like GSM to allow multiple users to share a single radio frequency channel.
Serial vs. Parallel Transmission Modes
Where is Morse Code used?
Asked in: Assistant Auditor(LDCE) 2021
- Telephone
- Telegram
- Satellite Navigation
- Computers
Show answer
Answer: B. Telegram
Morse code was developed by Samuel Morse in the 1830s. It represents letters, numbers, and punctuation marks as sequences of dots (short signals) and dashes (long signals).
A total of how many bit codes are used for teleprinter machines by the 'Murray code'?
Asked in: Asst Mana APDCL GS 06 2023
- 25
- 9
- 5
- 4
Show answer
Answer: C. 5
The 5-bit Baudot code was a significant advancement in teleprinter technology, enabling more efficient transmission of text compared to earlier methods.
Transmission Impairments (Attenuation, Distortion, Noise)
The ability of a computer network to recover from any kind of error like connection failure, loss of data, etc. is known as :
Asked in: MPPSC CS Prelims 2025
- Routing
- Bandwidth
- Contention
- Resilience
Show answer
Answer: D. Resilience
mppsc 2025-2025 In the context of computer networks (and systems in general), resilience refers to the ability of the network to maintain a certain level of operational performance and recover quickly from failures, errors, attacks, or other disruptive events. This includes handling connection failures, data loss, and other issues.
What is attenuation in the context of signal transmission?
Asked in: Analyst Cum Programmer (Deputy Director) 2024
- The process of encoding a signal for secure transmission.
- The increase in signal strength due to amplific‐ ation.
- The loss of signal energy as it travels through a medium.
- The conversion of a digital signal into an analog signal.
Show answer
Answer: C. The loss of signal energy as it travels through a medium.
Attenuation is the natural degradation of a signal's power or amplitude over distance. It is an inherent characteristic of signal transmission in any medium.
The message 1001 is to be transmitted using the CRC polynomial x³ + x + 1 to protect it from errors. The message that should be transmitted is - - (5) Question not attempted
Asked in: Programmer Exam 2024
- 1001000
- 1001100
- 1001110
- 1001011
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Answer: A. 1001000
When transmitting a message using CRC, the original message is appended with a number of zero bits equal to the degree of the generator polynomial. This padded message is then divided by the generator polynomial using binary division (XOR operations) to find the remainder (CRC checksum). The final transmitted codeword is the original message with the calculated CRC remainder appended. However, in some question contexts, "the message that should be transmitted" might refer to the padded message before the final remainder is attached, especially if the correct codeword is not an option.
Network congestion occurs
Asked in: State Forest Service Main Examination paper2 2019
- In case of traffic overloading
- When a system terminates
- When connection between two nodes termin‐ ate
- None of the mentioned
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Answer: A. In case of traffic overloading
Network congestion is caused by traffic overloading on a network.
Unguided Transmission Media (Radio Waves, Microwaves, Infrared)
The 4th generation (4G) mobile telecommunication service, using TD-LTE technology, was started for the first time in India in;
Asked in: KPSC KAS Prelims 2014
- Kolkata
- Chennai
- New-Delhi
- Mumbai
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Answer: A. Kolkata
Airtel launched its 4G services based on TD-LTE technology in Kolkata on April 10, 2012, making it the first city in India to get commercial 4G service.
TV programmes can be transmitted all over the world, with the help of _______. a. geostationary satellites b. space wave propagation c. ground wave propagation d. longitudinal waves
Asked in: MPSC CS Prelims 2015
- a only
- a, b and c
- a and c only
- d only
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Answer: A. a only
- Geostationary satellites provide the necessary coverage area and fixed position for continuous global broadcasting. - Terrestrial methods like ground wave or limited space wave propagation cannot achieve worldwide reach for TV signals. - A network of geostationary satellites is key to international TV transmission.
‘Bluetooth’ technology is
Asked in: TNPSC CS Prelims 2015
- Satellite communication
- Wired communication between devices
- Wireless communication between devices
- Communication between landline to mobile phone
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Answer: C. Wireless communication between devices
- Bluetooth operates over short distances (typically up to 10 meters for standard Bluetooth, more with Class 1). - It uses radio waves in the 2.4 GHz ISM band. - It allows devices like smartphones, computers, keyboards, headphones, speakers, etc., to connect and exchange data wirelessly.
Remote Sensing uses which of the following in its applications ?
Asked in: UKPSC CS Prelims 2021
- Electric waves
- Sonar waves
- Gamma rays
- Electromagnetic waves
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Answer: D. Electromagnetic waves
- Remote sensing involves data acquisition from a distance without physical contact. - It primarily relies on the interaction of electromagnetic radiation with matter. - Different wavelengths within the electromagnetic spectrum provide different types of information.
TV remote control uses
Asked in: WBPSC CS Prelims 2020
- Infrared frequency
- Radio frequency
- Visible frequency
- Ultraviolet frequency
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Answer: A. Infrared frequency
Infrared radiation is commonly used for short-range wireless communication, such as in remote controls for electronic devices.
"Blue tooth" technology allows
Asked in: UPPSC Upper Mains 2011
- Signal transmission on mobile phones only
- Landline phone to mobile phone communica‐ tion
- Satellite television communication
- Wireless communication between equipments
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Answer: D. Wireless communication between equipments
Bluetooth is a short-range wireless technology standard used for exchanging data between fixed and mobile devices, creating personal area networks (PANs). It enables devices like smartphones, laptops, headphones, speakers, keyboards, mice, and other peripherals to communicate wirelessly over distances typically up to 10 meters (Class 2) or 100 meters (Class 1).
Waves used for telecommunication are
Asked in: UPPSC Upper Mains 2013
- Visible light
- Infrared
- Ultraviolet
- Microwave
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Answer: D. Microwave
Microwaves are part of the electromagnetic spectrum with wavelengths ranging from about one meter to one millimeter, corresponding to frequencies between 300 MHz (0.3 GHz) and 300 GHz. These frequencies are suitable for transmitting large amounts of data and can penetrate the atmosphere, making them ideal for point-to-point communication, satellite communication, cellular networks, Wi-Fi, and radar.