Question 1(a) [3 marks]

Give definition (Only) of Loudness, Fidelity and Reverberation

Answer:

Loudness: The subjective perception of sound intensity by the human ear, measured in decibels (dB).
Fidelity: The degree to which a system reproduces sound that is faithful to the original input signal.
Reverberation: The persistence of sound after the original sound source has stopped, caused by multiple reflections within an enclosed space.

Mnemonic: "LFR: Listen Faithfully to Room echoes"

Question 1(b) [4 marks]

Draw and explain block diagram of PA system

Answer:

Diagram:

graph LR
    A[Microphone] --> B[Preamplifier]
    B --> C[Mixer]
    C --> D[Power Amplifier]
    D --> E[Loudspeaker]
    F[Audio Input] --> C
    G[Equalizer] --> C

Microphone: Converts sound waves into electrical signals
Preamplifier: Boosts weak microphone signals to line level
Mixer: Combines multiple audio signals and adjusts levels
Power Amplifier: Increases signal power to drive loudspeakers
Loudspeaker: Converts electrical signals back into sound waves

Mnemonic: "MPMEL: Many People Make Excellent Listeners"

Question 1(c) [7 marks]

Discuss any two characteristic of Microphone and Explain wireless microphone

Answer:

Microphone Characteristics:

Characteristic	Description
Sensitivity	Measures how efficiently microphone converts acoustic pressure to electrical output (mV/Pa)
Directional Pattern	Defines pickup area (omnidirectional, cardioid, hypercardioid, bidirectional)

Wireless Microphone:

graph LR
    A[Microphone Element] --> B[Audio Processor]
    B --> C[RF Transmitter]
    C -->|Radio Waves| D[RF Receiver]
    D --> E[Audio Output]

Microphone Element: Captures sound and converts to electrical signals
RF Transmitter: Modulates audio onto radio frequency carrier
Transmission: Typical frequency bands are UHF (470-698 MHz) or VHF (174-216 MHz)
RF Receiver: Demodulates signal back to audio
Advantages: Mobility, no cable restrictions, reduces stage clutter

Mnemonic: "SMART: Sensitivity Measures Audio Response Truly"

Question 1(c) OR [7 marks]

Discuss any two characteristics of loudspeaker and explain permanent magnet loudspeaker.

Answer:

Loudspeaker Characteristics:

Characteristic	Description
Frequency Response	Range of frequencies (Hz) speaker can reproduce (typically 20Hz-20kHz)
Impedance	Electrical resistance (ohms) that affects power transfer from amplifier (typically 4-8Ω)

Permanent Magnet Loudspeaker:

graph LR
    A[Permanent Magnet] --> B[Voice Coil]
    B --> C[Cone/Diaphragm]
    D[Audio Input] --> B
    C --> E[Sound Waves]

Permanent Magnet: Creates fixed magnetic field (usually ferrite or neodymium)
Voice Coil: Wire coil that carries audio current, creating variable magnetic field
Cone/Diaphragm: Moves in response to voice coil movement
Working Principle: Interaction between fixed magnetic field and varying field from voice coil creates mechanical movement
Advantages: More efficient, no field coil power required, compact design

Mnemonic: "FIRM: Frequency Impedance Require Magnets"

Question 2(a) [3 marks]

Define only: Aspect ratio, Luminance and chrominance

Answer:

Aspect Ratio: The ratio of width to height of a television screen (commonly 16:9 for HDTV, 4:3 for older TVs).
Luminance: The brightness component of a video signal that carries intensity information (represented as Y).
Chrominance: The color component of a video signal that carries color information (represented as U and V or Cb and Cr).

Mnemonic: "ALC: All Light Contains color"

Question 2(b) [4 marks]

Draw PAL-D decoder only and explain separation of U and V component of chroma signal.

Answer:

Diagram:

graph LR
    A[Composite Video Input] --> B[Comb Filter]
    B -->|Y Signal| C[Luminance Processing]
    B -->|Chroma Signal| D[Delay Line]
    D --> E[Phase Alternating Switch]
    E --> F[Synchronous Demodulator]
    F --> G[U Signal - Blue-Luminance]
    F --> H[V Signal - Red-Luminance]

Comb Filter: Separates luminance (Y) from chrominance signal
Delay Line: Delays chroma signal by one line period (64μs)
Phase Alternating Switch: Inverts V component on alternate lines
Synchronous Demodulator: Uses subcarrier reference to extract U and V components
U Component: Represents Blue-minus-Luminance (B-Y)
V Component: Represents Red-minus-Luminance (R-Y)

Mnemonic: "CODES: Chrominance Only Decodes Extracting Signals"

Question 2(c) [7 marks]

Explain in detail working of LCD television. Give any two technical specifications of it.

Answer:

LCD Television Working:

graph LR
    A[Backlight] --> B[Polarizing Filter 1]
    B --> C[Liquid Crystal Layer]
    C --> D[Color Filter]
    D --> E[Polarizing Filter 2]
    F[Video Signal] --> G[Control Circuit]
    G --> H[TFT Matrix]
    H --> C

Working Process:

Backlight: CCFL or LED provides white light source
TFT Matrix: Thin-film transistors control voltage to each pixel
Liquid Crystal Layer: Molecules twist based on applied voltage
Polarizers: First filter aligns light, second passes only rotated light
Color Filters: RGB filters create colored pixels
Image Formation: Varying voltage controls light passage through each pixel

Technical Specifications:

Resolution: 1920×1080 (Full HD) or 3840×2160 (4K UHD)
Refresh Rate: 60Hz, 120Hz, or 240Hz

Mnemonic: "BALTIC: Backlight Activates Liquid To Illuminate Colors"

Question 2(a) OR [3 marks]

State Grassmens law & explain it with concept of additive mixing.

Answer:

Grassmann's Law: Any color can be matched by a linear combination of three primary colors.

Additive Color Mixing Explanation:

graph TD
    A[Red Primary] --> D[Red + Green = Yellow]
    B[Green Primary] --> D
    B --> E[Green + Blue = Cyan]
    C[Blue Primary] --> E
    C --> F[Blue + Red = Magenta]
    A --> F
    D --> G[R + G + B = White]
    E --> G
    F --> G

Principle: Adding light of different colors creates new colors
Primary Colors: Red, Green, and Blue
Secondary Colors: Yellow (R+G), Cyan (G+B), Magenta (B+R)
Example: Equal intensities of RGB create white light

Mnemonic: "RGB-ACM: Red Green Blue - Additive Creates More"

Question 2(b) OR [4 marks]

Draw block diagram of DTH receiver and explain it.

Answer:

Diagram:

graph LR
    A[Satellite Dish] --> B[LNB]
    B --> C[Tuner]
    C --> D[Demodulator]
    D --> E[MPEG Decoder]
    E --> F[Video/Audio Processor]
    F --> G[TV Output]
    H[Conditional Access Module] --> E
    I[Smart Card] --> H

Satellite Dish: Collects weak satellite signals (10.7-12.75 GHz)
LNB (Low Noise Block): Amplifies and converts signal to lower frequency (950-2150 MHz)
Tuner: Selects desired transponder frequency
Demodulator: Extracts digital data from carrier signal
MPEG Decoder: Decompresses audio/video data
CAM & Smart Card: Provide decryption and subscription verification
Output: Processes signals for display on television

Mnemonic: "SLTD-MCS: Satellites Link Through Decoders Making Clear Signals"

Question 2(c) OR [7 marks]

State following frequency/standard (used in color TV system)

Answer:

Parameter	Frequency/Standard
VIF (Video Intermediate Frequency)	38.9 MHz (PAL-B/G)
SIF (Sound Intermediate Frequency)	33.4 MHz (PAL-B/G)
Color Sub-carrier Frequency	4.43361875 MHz (PAL)
Vertical Blanking Frequency	50 Hz (PAL)
Horizontal Synchronizing Frequency	15.625 kHz (PAL)
Inter Carrier Sound Signal Frequency	5.5 MHz (PAL-B/G)
One Channel Bandwidth	7 MHz (VHF), 8 MHz (UHF)

Mnemonic: "Very Special Colors Vertically Harmonize In One Channel"

Question 3(a) [3 marks]

What is fuzzy logic? Explain its usage in washing machine.

Answer:

Fuzzy Logic: A mathematical approach that deals with approximate reasoning rather than fixed, binary logic, allowing for degrees of truth values between 0 and 1.

Usage in Washing Machine:

graph LR
    A[Sensors] --> B[Fuzzy Controller]
    B --> C[Decision Making]
    C --> D[Control Actions]
    E[Load Size] --> A
    F[Fabric Type] --> A
    G[Dirt Level] --> A

Input Variables: Load weight, fabric type, water hardness, dirt level
Processing: Controller evaluates multiple conditions simultaneously
Output: Adjusts water level, wash time, rinse cycles, spin speed

Mnemonic: "FIND: Fuzzy Intelligence Navigates Decisions"

Question 3(b) [4 marks]

Define air conditioning. Explain working of fridge. State its technical specification.

Answer:

Air Conditioning: The process of removing heat and moisture from indoor air to improve comfort.

Refrigerator Working:

graph LR
    A[Compressor] -->|High Pressure Vapor| B[Condenser]
    B -->|High Pressure Liquid| C[Expansion Valve]
    C -->|Low Pressure Liquid| D[Evaporator]
    D -->|Low Pressure Vapor| A

Working Cycle:

Compressor: Compresses refrigerant gas, raising temperature
Condenser: Hot gas releases heat to outside, becomes liquid
Expansion Valve: Liquid expands, cools rapidly
Evaporator: Cold refrigerant absorbs heat from inside cabinet

Technical Specifications:

Capacity: 150-500 liters
Energy Rating: 3-5 Star
Power Consumption: 100-300 kWh/year

Mnemonic: "CEVA: Compress, Expel heat, Valve expands, Absorb heat"

Question 3(c) [7 marks]

Explain working principle of Microwave oven using functional block diagram. State its technical specifications.

Answer:

Microwave Oven Working:

graph LR
    A[Power Supply] --> B[Control Panel]
    B --> C[Timer & Controller]
    C --> D[Magnetron]
    D --> E[Waveguide]
    E --> F[Cooking Cavity]
    G[Turntable Motor] --> F
    C --> G
    H[Door Safety Interlocks] --> C

Working Principle:

Magnetron: Generates microwaves at 2.45 GHz frequency
Waveguide: Directs microwaves into cooking cavity
Water Molecules: Microwaves cause water molecules to vibrate
Heat Generation: Molecular vibration creates friction and heat
Turntable: Rotates food for even cooking
Safety Interlocks: Prevent operation when door is open

Technical Specifications:

Power Output: 700-1200 watts
Frequency: 2.45 GHz
Capacity: 20-40 liters
Cooking Modes: Microwave, Grill, Convection, Combination

Mnemonic: "MICRO: Magnetron Initiates Cooking by Rotating Oscillations"

Question 3(a) OR [3 marks]

Give technical specification of solar panel. State advantages and disadvantages of solar roof top system

Answer:

Solar Panel Technical Specifications:

Power Rating: 250-400 Wp (Watt peak)
Efficiency: 15-22%
Cell Type: Monocrystalline, Polycrystalline, or Thin Film

Advantages and Disadvantages:

Advantages	Disadvantages
Renewable Energy Source	High Initial Cost
Reduces Electricity Bills	Weather Dependent
Low Maintenance Cost	Requires Large Space
No Noise Pollution	Limited Nighttime Generation

Mnemonic: "SERLN: Solar Energy Reduces Long-term Numbers"

Question 3(b) OR [4 marks]

State various types of washing machine. Compare frontload and top load washing machine.

Answer:

Types of Washing Machines:

Top Load (Agitator & Impeller)
Front Load
Semi-Automatic
Fully Automatic

Comparison:

Parameter	Front Load	Top Load
Water Consumption	Lower (40-60 liters)	Higher (80-120 liters)
Energy Efficiency	Higher	Lower
Cleaning Performance	Better	Good
Space Requirement	Can be stacked	Needs top clearance
Cost	Higher	Lower
Cycle Duration	Longer (60-120 min)	Shorter (30-60 min)

Mnemonic: "FTEST: Front-loaders Take Extra Space but Triumph in efficiency"

Question 3(c) OR [7 marks]

Give classification of solar rooftop system. Explain working of solar rooftop system (Grid connected online) with suitable diagram. State steps to maintain solar roof top system.

Answer:

Classification of Solar Rooftop Systems:

Grid-Connected (On-grid)
Off-Grid (Standalone)
Hybrid (With battery backup)

Grid-Connected Solar System:

graph LR
    A[Solar Panels] -->|DC Current| B[DC Junction Box]
    B --> C[Solar Inverter]
    C -->|AC Current| D[AC Distribution Box]
    D --> E[Home Loads]
    D --> F[Bi-directional Meter]
    F --> G[Grid Connection]
    G --> F

Working:

Solar Panels: Convert sunlight to DC electricity
Junction Box: Combines outputs, provides protection
Inverter: Converts DC to grid-compatible AC
Distribution Box: Distributes power to loads
Bi-directional Meter: Measures import/export of electricity
Excess Generation: Feeds back to grid (Net metering)

Maintenance Steps:

Regular cleaning of panels (dust, bird droppings)
Checking electrical connections for corrosion
Monitoring system performance via inverter data
Trimming nearby trees to prevent shading
Annual inspection by qualified technician

Mnemonic: "SPICED: Solar Panels Invert Current for Electrical Distribution"

Question 4(a) [3 marks]

Explain in brief working principle of photo copier machine with concept of latent image.

Answer:

Photocopier Working Principle:

graph LR
    A[Charging] --> B[Exposure]
    B --> C[Developing]
    C --> D[Transfer]
    D --> E[Fusing]
    E --> F[Cleaning]

Latent Image Concept:

Charging: Photosensitive drum receives uniform positive charge
Exposure: Light reflects from original document onto drum
Latent Image: Light areas discharge drum creating invisible electrostatic image
Development: Negatively charged toner particles attracted to positive areas
Transfer: Toner transferred to paper through electrical attraction
Fusing: Heat and pressure permanently bond toner to paper

Mnemonic: "CEDTFC: Charging Exposure Develops The Final Copy"

Question 4(b) [4 marks]

Explain working of Laser printer with suitable diagram

Answer:

Laser Printer Working:

graph LR
    A[Data Processing] --> B[Laser Scanning Unit]
    B --> C[Photosensitive Drum]
    D[Primary Corona] --> C
    C --> E[Developer Unit]
    E --> F[Transfer Unit]
    F --> G[Fusing Unit]
    G --> H[Paper Output]
    I[Cleaning Unit] --> C

Working Process:

Raster Image Processing: Computer data converted to bitmap
Charging: Corona wire gives drum uniform negative charge
Writing: Laser beam neutralizes charge in pattern of image
Developing: Toner attracted to neutralized areas
Transfer: Paper given positive charge to attract toner
Fusing: Heat rollers melt toner permanently onto paper
Cleaning: Excess toner removed from drum for next cycle

Mnemonic: "RASTER: Raster-image Attracts Static Toner, Electricity Releases"

Question 4(c) [7 marks]

Draw and explain block diagram of CCTV system using Digital IP camera connected with internet. List at least five different camera used in CCTV system. What is meaning of POE cable?

Answer:

IP CCTV System:

graph LR
    A[IP Cameras] -->|Ethernet/POE| B[Network Switch]
    B --> C[Network Video Recorder]
    C --> D[Storage]
    C --> E[Router/Internet Gateway]
    E -->|WAN| F[Remote Viewing Devices]
    G[Local Monitor] --> C

Working:

IP Cameras: Capture and digitize video
Network Infrastructure: Transmits data via TCP/IP protocols
NVR: Records, manages, and processes video streams
Storage: Hard drives store recorded footage
Router: Provides secure internet access for remote viewing

Camera Types:

Dome Cameras: Indoor ceiling-mounted, vandal-resistant
Bullet Cameras: Outdoor wall-mounted, long-range
PTZ Cameras: Pan, tilt, zoom capabilities for wide coverage
Fisheye Cameras: 360° panoramic view with single lens
Thermal Cameras: Detect heat signatures in darkness

POE Cable: Power Over Ethernet - A technology that carries both power and data over a single Ethernet cable, eliminating the need for separate power cables.

Mnemonic: "INSPIRE: Internet Networking Secures Places In Remote Environments"

Question 4(a) OR [3 marks]

Discuss pros and cons of internet based Digital IP camera CCTV system

Answer:

Pros and Cons of IP Camera CCTV Systems:

Pros	Cons
Higher Resolution (1080p to 4K)	Higher Initial Cost
Remote Viewing via internet	Bandwidth Requirements
Scalability & easy expansion	Cybersecurity Risks
Power Over Ethernet (POE)	Network Dependency
Advanced Analytics capabilities	Complex Configuration

Mnemonic: "HIGHER: High-resolution Images Give Higher Evaluation Remotely"

Question 4(b) OR [4 marks]

Explain working of inkjet printer with suitable diagram

Answer:

Inkjet Printer Working:

graph LR
    A[Print Data] --> B[Controller]
    B --> C[Print Head Assembly]
    C --> D[Ink Cartridges]
    D --> E[Nozzles]
    E --> F[Paper]
    G[Paper Feed Mechanism] --> F
    B --> G

Working Process:

Data Processing: Controller converts digital data to nozzle instructions
Paper Loading: Feed rollers position paper correctly
Print Head Movement: Carriage moves printhead across paper
Ink Ejection: Two methods:
- Thermal: Tiny resistors heat ink to create bubbles, forcing droplets
- Piezoelectric: Crystal elements flex to push ink through nozzles
Drying: Ink adheres to paper surface

Mnemonic: "PRINT: Paper Receives Ink through Numerous Tiny-nozzles"

Question 4(c) OR [7 marks]

Draw and explain block diagram of CCTV system using simple analog camera and DVR. List types of cable used in CCTV system. Discuss at least four different categories of camera used in modern CCTV system.

Answer:

Analog CCTV System:

graph LR
    A[Analog Cameras] -->|Coaxial Cable| B[DVR]
    B --> C[Hard Disk Storage]
    B --> D[Monitor]
    B --> E[Router]
    E -->|Internet| F[Remote Viewing]
    G[Power Supply] --> A

Working:

Analog Cameras: Capture video as continuous analog signals
DVR: Converts analog signals to digital format for recording
Storage: Records footage on internal hard drives
Viewing: Local monitors and remote access options

Cable Types:

Coaxial Cable (RG59, RG6): Traditional analog camera connection
Twisted Pair (CAT5/6): For IP cameras or with baluns
Power Cable: Supplies electricity to cameras
Fiber Optic: For long-distance transmissions
Siamese Cable: Combined coaxial and power cable

Camera Categories:

Fixed Cameras: Constant view angle, no movement
Varifocal Cameras: Adjustable lens for different focal lengths
Night Vision Cameras: IR illuminators for low-light conditions
High Dynamic Range (HDR): Balanced exposure in mixed lighting

Mnemonic: "CARD: Coaxial Analog Recording Devices"

Question 5(a) [3 marks]

Define only: Maintenance, Preventive maintenance and Predictive maintenance.

Answer:

Maintenance: The process of preserving equipment in proper operating condition through regular inspection, cleaning, and repair.
Preventive Maintenance: Scheduled maintenance activities performed to prevent equipment failures before they occur.
Predictive Maintenance: Condition-based maintenance approach that uses data analysis and monitoring techniques to predict when equipment failure might occur.

Mnemonic: "MPP: Maintain Proactively, Predict problems"

Question 5(b) [4 marks]

Discuss maintenance of public address system.

Answer:

PA System Maintenance:

Component	Maintenance Tasks
Microphones	• Clean windscreens and grilles • Check cables for damage • Test for proper sensitivity
Amplifiers	• Clean cooling vents • Check power connections • Inspect for overheating
Speakers	• Inspect mounting brackets • Test for distortion • Check wiring connections
Cables & Connections	• Test continuity • Replace damaged cables • Secure loose connections

Periodic Maintenance:

Weekly: Basic operations check
Monthly: Signal path testing
Quarterly: Comprehensive inspection
Annually: Professional service

Mnemonic: "MACS: Microphones, Amplifiers, Connections, Speakers"

Question 5(c) [7 marks]

State any three faults of washing machine. Discuss in general maintenance of washing machine.

Answer:

Common Washing Machine Faults:

Water Not Filling: Faulty inlet valve, clogged filter, water pressure issues
Not Spinning: Belt issues, motor problems, unbalanced load
Excessive Vibration: Uneven feet, suspension issues, drum damage

General Maintenance:

Component	Maintenance Procedure
Drum/Tub	• Clean monthly to remove residue • Check for foreign objects • Run cleaning cycle with white vinegar
Filters	• Clean lint filter after each use • Clean pump filter monthly • Check water inlet filters quarterly
Hoses	• Inspect for cracks or leaks • Replace every 3-5 years • Ensure proper connection
Door Seal	• Wipe after use to prevent mold • Check for tears • Keep door ajar when not in use
Dispensers	• Remove and clean monthly • Check for blockages • Remove detergent buildup

Mnemonic: "WATCH: Water And Tub Cleaning Helps"

Question 5(a) OR [3 marks]

Compare predictive and preventive maintenance.

Answer:

Comparison of Predictive vs. Preventive Maintenance:

Parameter	Predictive Maintenance	Preventive Maintenance
Approach	Condition-based	Time-based
Timing	When needed based on data	Fixed schedule regardless of condition
Techniques	Vibration analysis, thermal imaging, oil analysis	Visual inspection, cleaning, lubrication
Cost	Higher initial setup, lower long-term	Lower initial cost, potentially higher long-term
Downtime	Minimized, planned ahead	Regular scheduled downtime
Equipment Usage	Maximized lifespan	Some components replaced prematurely

Mnemonic: "TIMED: Testing Identifies Maintenance Exactly when Due"

Question 5(b) OR [4 marks]

Discuss maintenance and troubleshooting of LCD TV.

Answer:

LCD TV Maintenance:

Component	Maintenance Tasks
Screen	• Clean with microfiber cloth • Avoid liquid cleaners • Check for dead pixels
Ventilation	• Remove dust from vents • Ensure proper airflow • Check fan operation
Connections	• Verify cable connections • Check for corrosion • Test HDMI ports
Software	• Update firmware regularly • Reset settings if needed

Common Troubleshooting Issues:

Problem	Possible Solutions
No Power	Check power cord, outlet, internal fuse
No Picture	Verify input source, backlight failure, T-Con board
Lines on Screen	Check ribbon cables, screen damage, T-Con board
Audio Issues	Speaker connections, audio settings, amplifier board

Mnemonic: "PVCS: Pixels, Ventilation, Connections, Software"

Question 5(c) OR [7 marks]

Explain installation of laser printers in your computer system. Discuss its maintenance and troubleshooting procedure.

Answer:

Laser Printer Installation:

graph LR
    A[Unpacking] --> B[Hardware Setup]
    B --> C[Cartridge Installation]
    C --> D[Power Connection]
    D --> E[Interface Connection]
    E --> F[Driver Installation]
    F --> G[Test Print]

Installation Steps:

Setup Location: Flat, stable surface with proper ventilation
Remove Packaging: Remove tape, protective films, shipping locks
Install Consumables: Toner cartridge, imaging drum if separate
Connect Power: Plug into grounded outlet
Connect Interface: USB, Ethernet, or Wi-Fi setup
Install Driver: From included CD or manufacturer website
Configure Settings: Network parameters, paper size, default tray

Maintenance:

Component	Maintenance Task
Paper Path	Clean with compressed air monthly
Toner Area	Vacuum carefully when replacing toner
Rollers	Clean with isopropyl alcohol quarterly
Exterior	Wipe with damp cloth as needed

Troubleshooting:

Problem	Solution
Paper Jams	Check paper path, clean rollers, verify paper specifications
Streaking	Clean corona wire, replace drum if worn
Light Printing	Adjust density settings, replace toner
Connection Issues	Check cables, reinstall drivers, reset printer

Mnemonic: "SECURE: Setup, Execute drivers, Clean Regularly, Update, Replace consumables, Examine problems"