Diploma in electrical mod iii nov 2024 answers

SECTION A: MICROPROCESSOR SYSTEMS

1. (a) Define the following with respect to microprocessors:

• Bus
• Register

Answer:

• Bus: A communication pathway that transfers data, addresses, and control signals between different components of a microprocessor system.
• Register: A small storage location within the CPU used for temporarily holding data and instructions.

(b) State the function of each of the following microprocessor registers citing their size in bits:

• Program Counter (PC)
• Accumulator (A)

Answer:

• Program Counter (PC): Holds the address of the next instruction to be executed. Size: 16-bit (in 8085).
• Accumulator (A): A special register used to store intermediate arithmetic and logic operation results. Size: 8-bit.

2. (a) Define each of the following with respect to subroutines:

• Parameter Passing
• Nesting

Answer:

• Parameter Passing: The process of providing input values to a subroutine.
• Nesting: Calling a subroutine from within another subroutine.

3. (a) Describe each of the following Intel 8085 microprocessor instructions citing their addressing modes:

• DAD D
• DAA
• CNZ 4000H

Answer:

• DAD D: Adds the contents of the DE register pair to the HL register pair. Addressing mode: Register Pair Addressing.
• DAA: Adjusts the contents of the accumulator to a valid Binary-Coded Decimal (BCD) format. Addressing mode: Implicit.
• CNZ 4000H: Calls the subroutine at memory location 4000H if the Zero flag is not set. Addressing mode: Immediate.

 (c) Describe each of the following with respect to microprocessor programming:

• Label
• Assembler Directives
• Macros

Answer:

• Label: A name assigned to a memory location or instruction to improve readability in assembly language programs.
• Assembler Directives: Commands that instruct the assembler on how to process the source code but do not generate machine code.
• Macros: A group of instructions defined once and used multiple times in a program to simplify coding.

4. (a) State three CPU signals used in Direct Memory Access (DMA) data transfer.

Answer:

• Hold (HOLD): Request signal sent by the DMA controller to take control of the system bus.
• Hold Acknowledge (HLDA): Signal sent by the CPU to grant control of the bus to the DMA controller.
• DMA Request (DREQ): Signal from a peripheral device requesting the CPU to transfer data using DMA.

6. (a) Explain each of the following microprocessor assembly language programming tools:

• Compiler
• Cross Assembler
• Linker

Answer:

• Compiler: Translates high-level code into machine language.
• Cross Assembler: Converts assembly code from one platform to another.
• Linker: Combines multiple object files into a single executable program.

 

SECTION B: MICROCONTROLLER TECHNOLOGY

6(a) State three 8-bit registers used in Intel 8051 microcontroller.

Answer:

• Accumulator (A)
• B Register
• Register R0 to R7

7(a) Distinguish between each of the following with respect to process control:

• Process Variable and Manipulated Variable
• Process Load and Process Log

Answer:

• Process Variable: The measured value in a system (e.g., temperature, pressure).
• Manipulated Variable: The variable adjusted by the controller to maintain the desired process variable.
• Process Load: The external disturbances affecting the system.
• Process Log: A recorded history of process variables over time.

(b) State three advantages of programmable logic controllers (PLCs) over hard-wired relay logic.

Answer:

• Easier reprogramming and modification.
• More reliable operation with fewer mechanical failures.
• Less wiring and reduced complexity in large control systems.

ROBOTICS

8(a) Define each of the following with respect to robots:

• Work Space
• Work Volume
• Reach

Answer:

• Work Space: The entire area in which a robot can operate.
• Work Volume: The three-dimensional space within which a robot can perform tasks.
• Reach: The maximum distance a robot’s end-effector can extend from its base.

 (a) State two types of drive systems used in robotics.

Answer:

• Electric Drive System
• Hydraulic Drive System

 (b) Describe each of the following elements of a robot system:

• Actuator
• Degrees of Freedom
• Gripper

Answer:

• Actuator: A device that converts energy into motion, enabling the robot to move.
• Degrees of Freedom: The number of independent movements a robot can make.
• Gripper: A robotic component used to hold and manipulate objects.

4. (a) With the aid of diagrams, describe each of the following robotic joints:

• Rotational
• Linear
• Revolving

Answer:

• Rotational Joint: Allows movement around a fixed axis.
• Linear Joint: Enables straight-line motion.
• Revolving Joint: Combines rotation and translation motion.

 

SECTION A: INDUSTRIAL MANAGEMENT

1. (a) Describe three industrial disputes that may arise in a manufacturing organization.

Answer:

1. Wage disputes: Arise when employees demand higher wages or better benefits.
2. Working condition disputes: Occur when employees are dissatisfied with workplace safety, hours, or facilities.
3. Employment termination disputes: Result from unfair dismissals or contract breaches.

 (b) Explain three costs associated with plant maintenance.

Answer:

1. Preventive maintenance costs: Expenses for regular servicing and inspections.
2. Corrective maintenance costs: Costs incurred due to breakdowns and repairs.
3. Downtime costs: Losses due to production stoppages during maintenance.

 (c) Describe four challenges that may be faced by a production plant.

Answer:

1. Equipment failures leading to production delays.
2. High operational costs due to energy consumption and raw material expenses.
3. Labor shortages affecting productivity.
4. Regulatory compliance issues that may lead to fines or shutdowns.

2(a) State four obligations of a manufacturing organization to its competitors.

Answer:

1. Fair competition by avoiding monopolistic practices.
2. Respecting intellectual property rights of competitors.
3. Ethical business practices without false advertising.
4. Compliance with industry standards to ensure fair trade.

 (b) (i) Explain the concept of ‘administration’ as applied to management.

Answer:

• Administration in management refers to planning, organizing, directing, and controlling business activities to achieve organizational goals.

 (b) (ii) Highlight four situations when good leadership is required in an organization.

Answer:

1. During organizational change to ensure smooth transitions.
2. In crisis management to provide direction.
3. When resolving conflicts among employees.
4. For motivating employees to boost productivity.

 (c) List four advertising media used by industrial organizations.

Answer:

1. Television and radio advertisements.
2. Newspaper and magazine ads.
3. Online and social media marketing.
4. Billboards and posters.

 (d) Explain why performance contracting has become a popular concept in modern organizations.

Answer:

• It enhances efficiency, accountability, and goal setting while improving overall productivity and service delivery.

3 (a) Outline three duties performed by an office staff.

Answer:

1. Record keeping and documentation.
2. Customer service and communication.
3. Administrative support to management.

 (b) Describe three monetary policy instruments used by the Central Bank to control the money supply in an economy.

Answer:

1. Open market operations: Buying and selling government securities.
2. Reserve requirements: Setting minimum cash reserves for banks.
3. Discount rate: Adjusting interest rates to influence borrowing.

SECTION B: ESTIMATING, TENDERING, AND SERVICES CONTRACTS

4(a) Describe three acts of negligence that a contractor may commit at a project site.

Answer:

1. Failure to follow safety regulations leading to workplace accidents.
2. Use of substandard materials compromising structural integrity.
3. Delays in project completion due to poor planning.

 (b) Highlight three challenges of settling contractual disputes through the courts.

Answer:

1. Time-consuming process due to lengthy legal procedures.
2. High legal costs involved in hiring lawyers.
3. Uncertainty of outcomes as judgments may be unpredictable.

 (c) Describe four requirements that may be used to determine an individual’s capacity to contract.

Answer:

1. Legal age: Must be of legal age to enter contracts.
2. Mental competence: Should be of sound mind.
3. Free consent: Agreement must be voluntary.
4. Financial capability: Must have the means to fulfill contract terms.

 5(a) Outline six clauses that should be contained in the schedule of conditions of a construction contract.

Answer:

1. Scope of work.
2. Project timelines and milestones.
3. Payment terms and schedules.
4. Dispute resolution mechanisms.
5. Material specifications.
6. Health and safety requirements.

 (b) Explain three methods of discharging contracts.

Answer:

1. Performance: Completion of contractual obligations.
2. Mutual agreement: Both parties agree to end the contract.
3. Breach of contract: One party fails to fulfill obligations.

(c) (i) Explain two circumstances when cost-reimbursement contracting can be applied.

Answer:

1. When project scope is uncertain.
2. For research and development contracts.

(c) (ii) State four limitations of cost-reimbursement contracts to the client.

Answer:

1. Higher financial risk.
2. Difficulty in cost control.
3. Potential for inefficiency.
4. Time-consuming audits.

6(a) State four reasons that may lead to rejection of a tender document.

Answer:

1. Incomplete documentation.
2. Failure to meet technical specifications.
3. Lack of financial capability.
4. Submission after the deadline.

(b) Explain four benefits of open tendering to an organization.

Answer:

1. Encourages fair competition.
2. Leads to better pricing.
3. Ensures transparency.
4. Allows access to a wider pool of contractors.

(c) Describe four methods of allocating overhead costs to a project estimate.

Answer:

1. Direct allocation method.
2. Activity-based costing.
3. Percentage of total project cost.
4. Unit-based costing.

7(a) Explain three ways through which a contractor may obtain quotations from potential material suppliers for a project.

Answer:

1. Request for Quotations (RFQs).
2. Inviting tenders.
3. Negotiation with preferred suppliers.

 (b) Describe three measures a contractor may take to avoid the purchase of defective materials.

Answer:

1. Conducting supplier evaluations.
2. Requesting material test reports.
3. Inspecting deliveries before acceptance.

 (c) Describe four methods of reporting work progress at a site.

Answer:

1. Daily site reports.
2. Weekly progress meetings.
3. Photographic documentation.
4. Gantt charts and project schedules.

8(a) List four office overheads for a project.

Answer:

1. Staff salaries.
2. Office rent and utilities.
3. Communication costs.
4. Stationery and supplies.

(b) Highlight six activities that should be performed when preparing for a construction site meeting.

Answer:

1. Reviewing the agenda.
2. Ensuring all relevant documents are available.
3. Confirming attendance of key stakeholders.
4. Setting up the meeting space.
5. Assigning roles and responsibilities.
6. Documenting action items from previous meetings.

(c) Describe five measures the project manager should take to resolve a wage conflict with technicians.

Answer:

1. Engaging in open dialogue.
2. Reviewing wage structures.
3. Negotiating a fair settlement.
4. Consulting labor laws and agreements.
5. Seeking mediation if necessary.

SECTION A: MACHINES AND UTILIZATION

1. (a) What are two merits of a three-phase induction motor?

• High efficiency and reliability.
• Self-starting capability without the need for external starting mechanisms.

 (b) Explain the following methods of speed control of a three-phase induction motor:

(i) Changing the applied frequency

• The speed of an induction motor is directly proportional to the supply frequency. Adjusting the frequency using a variable frequency drive (VFD) changes the motor speed.

(ii) Changing the number of stator poles

• The speed of an induction motor is inversely proportional to the number of poles. By reconnecting the windings differently, the effective number of poles can be changed, thus altering the speed.

 (c) (i) What are two reasons for carrying out a short circuit test on a three-phase induction motor?

• To determine the equivalent circuit parameters of the motor.
• To estimate the motor’s copper losses under running conditions.

2 (a) With reference to three-phase synchronous motors, explain the following terms:

(i) Starting torque

• A synchronous motor does not have starting torque when directly connected to the supply because it requires an external means to reach synchronous speed before it can operate efficiently.

(ii) Hunting

• This is the oscillation of the rotor about its final steady position due to sudden load changes.

3 (a) (i) What are two applications of D.C series motors?

• Used in electric trains and locomotives.
• Applied in cranes and hoists where high starting torque is required.

  (ii) What are two demerits of reluctance motors?

• They have low starting torque.
• Their power factor is generally poor.

4 (a) What are two merits of regenerative braking in electric traction systems?

• It improves energy efficiency by feeding excess energy back into the supply system.
• Reduces wear and tear on mechanical braking components.

5 (b) Explain the following modes of operation of an electric train:

(i) Coasting

• The train moves without power being supplied to the motor, relying on inertia to continue moving.

(ii) Free run

• The train operates under normal power conditions without additional acceleration or braking.

 (c) (i) What are two properties of refrigerants?

• Low boiling point to allow effective heat absorption.
• Non-corrosive and chemically stable to prevent system damage.

SECTION B: POWER ELECTRONICS

6(a) What are two application areas of a thyristor (SCR)?

• Used in controlled rectifiers for converting AC to DC.
• Applied in variable speed drives for electric motors.

7(a) What are the three types of cycloconverters?

• Step-up cycloconverter: Increases output frequency.
• Step-down cycloconverter: Reduces output frequency.
• Three-phase to single-phase cycloconverter: Converts three-phase power to single-phase at a different frequency.

 (d) Explain AC motor speed control by the voltage regulation method.

• The speed of an AC motor can be controlled by varying the supply voltage. Reducing the voltage decreases the torque, which in turn affects the speed. This method is mainly used for small applications where precise control is not required.

8(a) What are three merits of high-frequency electric heating?

• Provides uniform heating, reducing material damage.
• Increases efficiency due to reduced heat loss.
• Allows precise temperature control for industrial processes.

 (c) (i) What is the equivalent current method of determining motor rating?

• This method estimates the motor rating based on the expected current draw under different load conditions, ensuring the selected motor operates efficiently without overloading.

 

SECTION A: ELECTRICAL POWER SYSTEMS

1(a) Explain the following as applicable to overhead line conductors:

(i) Galloping
Galloping refers to the low-frequency, high-amplitude oscillations of overhead power lines due to wind forces. It is caused by the aerodynamic instability of ice-covered conductors, leading to mechanical damage and electrical faults.

(ii) High-Frequency Vibrations
High-frequency vibrations, also known as Aeolian vibrations, occur due to steady winds interacting with power lines. These cause small-amplitude oscillations, which over time can lead to fatigue damage in conductors and fittings.

 (b) Explain the effect of conductor surface on corona formation.

Corona formation occurs when the electric field around a conductor ionizes the surrounding air. A smooth and polished conductor surface reduces corona discharge by minimizing sharp edges and irregularities that intensify the electric field. Rough or stranded conductors promote corona discharge due to localized electric field enhancements.

2(a) With reference to overhead transmission lines, explain the effect of surges on open-circuited lines and arcing ground.

• Surges on Open-Circuited Lines: When a surge reaches an open circuit, it reflects back with the same magnitude but opposite polarity, potentially damaging insulation and equipment.
• Arcing Ground: In ungrounded or weakly grounded systems, arcing ground occurs when a transient overvoltage causes repeated breakdown and extinction of the insulation, leading to high-frequency oscillations and possible damage.

 (c) Explain the effect of power factor on the efficiency of an overhead transmission line.

A lower power factor increases the current flow in a transmission line for the same power delivery, leading to higher I²R losses and reduced efficiency. Improving the power factor (e.g., by using capacitors) reduces these losses, enhancing transmission efficiency.

3(a) State two merits of the valve-type arrester.

1. High Surge Absorption: The valve-type arrester efficiently absorbs high-energy surges, protecting electrical equipment from voltage spikes.
2. Self-Restoring Property: It returns to its normal insulating state after a surge, ensuring continuous protection without requiring replacement.

(c) State two merits of the symmetrical component method in fault analysis.

1. Simplifies Complex Fault Analysis: It breaks down unbalanced faults into symmetrical components (positive, negative, and zero sequence), making fault calculations easier.
2. Applicable to Different Fault Types: It can analyze various faults, including line-to-line, line-to-ground, and three-phase faults, providing a unified approach for power system analysis.

4(a) State two merits of solid-state relays.

1. Faster Switching: Solid-state relays operate much faster than electromechanical relays, reducing response time in fault conditions.
2. No Moving Parts: They have no mechanical components, leading to increased reliability, longer lifespan, and silent operation.

 (c) State two merits of the Peterson coil earthing system.

1. Reduces Earth Fault Currents: The Peterson coil compensates for the capacitive charging current, minimizing ground fault currents and preventing damage.
2. Prevents Arcing Grounds: By neutralizing fault currents, it reduces the risk of transient overvoltages caused by arcing ground faults.

5(a) Explain the following terms as applied in power systems stability:

(i) Dynamic Stability
Dynamic stability refers to the power system’s ability to maintain synchronism following small disturbances over a short period (e.g., changes in load or generator output). It is assessed using transient stability analysis.

(ii) Steady-State Stability
Steady-state stability is the ability of the power system to return to its normal operating conditions after gradual load changes or minor disturbances. It ensures the system remains in synchronism under normal operating conditions.

 (b) Explain each of the following methods of improving power system stability:

(i) Braking Resistors
Braking resistors absorb excess energy during transient disturbances, preventing generators from accelerating too quickly and improving system stability.

(ii) Single Pole Switching
This method disconnects only the faulty phase during a fault, allowing the system to maintain operation and minimizing power disturbances.

(iii) Fast Acting Automatic Voltage Regulator (AVR)
An AVR quickly adjusts the generator’s excitation voltage, helping maintain system voltage and reactive power balance, thereby enhancing stability.

SECTION B: ELECTROMAGNETIC FIELD THEORY

6(a) State two properties of electromagnetic waves.

1. Transverse Nature: Electromagnetic waves consist of perpendicular electric and magnetic fields oscillating at right angles to each other and the direction of propagation.
2. Speed in Free Space: They travel at the speed of light (approximately 3 × 10⁸ m/s) in a vacuum.

7(a) Explain the following as applied in electrostatic fields:

(i) Electric Field Intensity (E)
Electric field intensity is the force per unit charge experienced by a small positive test charge in an electric field. It is measured in volts per meter (V/m).

(ii) Electric Flux Density (D)
Electric flux density represents the amount of electric field passing through a given area. It is related to permittivity and electric field intensity, measured in coulombs per square meter (C/m²).

 (b) State the Gauss Divergence Theorem in integral form and two methods of electromagnetic shielding.

• Gauss Divergence Theorem (Integral Form):

This states that the total electric flux leaving a closed surface is equal to the total charge enclosed within the surface.

• Two Methods of Electromagnetic Shielding:
  1. Faraday Cage: A conductive enclosure that blocks external electric fields.
  2. Shielding Materials: Use of materials with high conductivity (e.g., copper, aluminum) to block electromagnetic interference.

 (c) Explain ‘electric dipole’ as applied in electrodynamics.

An electric dipole consists of two equal and opposite charges separated by a small distance. It creates an electric field and experiences a torque when placed in an external electric field, aligning itself with the field.

8(a) State the characteristics of σ (conductivity), ε (permittivity), and µ (permeability) as applied in plane waves for each of the following materials:

(i) Lossy Media:

• Conductivity (σ): Moderate (finite)
• Permittivity (ε): High
• Permeability (µ): Variable depending on the material

(ii) Good Conductors:

• Conductivity (σ): Very high
• Permittivity (ε): Low (almost negligible displacement current)
• Permeability (µ): Usually close to free space unless it is a magnetic material

 

SECTION A: ELECTROMAGNETIC FIELDS THEORY

1. Stokes’ Theorem

Stokes’ theorem relates a surface integral of a curl of a vector field over a surface to a line integral of the field along the boundary of the surface. Mathematically,

∮CF⋅dr=∬S(∇×F)⋅dSoint_C mathbf{F} cdot dmathbf{r} = iint_S (nabla times mathbf{F}) cdot dmathbf{S}

This theorem is useful in electromagnetics for converting complex surface integrals into simpler line integrals.

2. Symmetrical Charge Distributions

• Line charge: A continuous distribution of charge along a line. The electric field lines extend radially outward from the line.
• Surface charge: A charge distribution over a two-dimensional surface. The electric field is perpendicular to the charged surface.

3. Energy in a System of Point Charges

The energy in a system of point charges is calculated using Coulomb’s law:

W=14πϵ0∑i<jqiqjrijW = frac{1}{4piepsilon_0} sum_{i<j} frac{q_i q_j}{r_{ij}}

where qiq_i and qjq_j are charges, and rijr_{ij} is the distance between them.

4. Magnetic Flux Density and Magnetic Field Intensity

• Magnetic field intensity (H): A measure of magnetizing force, given in amperes per meter (A/m).
• Magnetic flux density (B): The total magnetic effect in a medium, measured in teslas (T), related by:

B=μHB = mu H

where μmu is the permeability of the medium.

5. Maxwell’s Equations (Differential Form)

1. Gauss’s Law for Electric Fields

∇⋅D=ρnabla cdot mathbf{D} = rho

States that the divergence of the electric flux density Dmathbf{D} equals the charge density ρrho.

1. Gauss’s Law for Magnetism

∇⋅B=0nabla cdot mathbf{B} = 0

Implies no magnetic monopoles exist; magnetic field lines form closed loops.

1. Faraday’s Law of Induction

∇×E=−∂B∂tnabla times mathbf{E} = -frac{partial mathbf{B}}{partial t}

A changing magnetic field induces an electric field.

1. Ampère’s Law with Maxwell’s Correction

∇×H=J+∂D∂tnabla times mathbf{H} = mathbf{J} + frac{partial mathbf{D}}{partial t}

Relates magnetic field intensity to current density and displacement current.

6. Poynting’s Theorem

Poynting’s theorem describes power flow in an electromagnetic field:

S=E×Hmathbf{S} = mathbf{E} times mathbf{H}

where Smathbf{S} is the Poynting vector, representing power per unit area.

SECTION B: COMMUNICATION SYSTEMS

1. Types of Analog Modulation Techniques

• Amplitude Modulation (AM): The amplitude of the carrier wave varies according to the message signal.
• Frequency Modulation (FM): The frequency of the carrier wave varies with the amplitude of the message signal.
• Phase Modulation (PM): The phase of the carrier wave changes according to the message signal.

2. Single Sideband (SSB) Generation

SSB reduces bandwidth usage by removing one sideband in AM transmission. The filter method uses a bandpass filter to remove the unwanted sideband.

3. Frequency Reuse, Handoff, and Roaming

• Frequency Reuse: The same frequency is used in different non-adjacent cells to improve efficiency.
• Handoff: The process of transferring an ongoing call from one cell tower to another as the user moves.
• Roaming: Allowing a mobile user to access network services outside their home network.

 

 

 

 

 

 

 

SECTION A: DATA COMMUNICATION

1(a)

(i) Distinguish between asynchronous and synchronous data transmission modes.

• Asynchronous transmission: Data is sent in individual units, each marked by a start and stop bit. It does not require synchronization between sender and receiver.
• Synchronous transmission: Data is sent as a continuous stream with timing synchronization between sender and receiver, eliminating the need for start and stop bits.

1. ii) Describe each of the following transmission impairments:

2. Attenuation distortion:

Attenuation refers to the gradual loss of signal strength over a transmission medium. It can result in weak signals at the receiving end.

1. Delay distortion:

This occurs when different frequency components of a signal travel at different speeds, causing parts of the signal to arrive at different times. It mainly affects high-speed data transmission.

III. Noise:

Noise is unwanted interference that distorts the transmitted signal. It can be caused by external sources like electrical devices or natural phenomena.

2(b)

(i) Distinguish between intrinsic and extrinsic losses in optical fibre cables.

• Intrinsic losses: These are signal losses due to the physical properties of the fibre itself, such as absorption and scattering.
• Extrinsic losses: These occur due to external factors like bending, splicing, or improper connections in the fibre.

 

 (c)(i) State two merits of using scrambling in data encoding schemes.

1. Prevents long sequences of zeros or ones, which helps maintain synchronization in data transmission.
2. Reduces signal interference, improving the overall quality of transmission.

2(a)(i) State three merits of spread-spectrum communication techniques.

1. Resistant to interference and jamming, making it more reliable in noisy environments.
2. Provides better security, as the transmitted signal is spread over a wide frequency range.
3. Allows multiple users to share the same bandwidth without significant interference (e.g., in CDMA).

(b)(ii) Explain the operation of a delta modulation transmitter.

Delta modulation is a method of encoding analog signals into digital form. It works by sending only the difference between the current and previous signal values. A comparator checks whether the signal has increased or decreased and transmits a corresponding binary value (1 or 0). This reduces data transmission requirements while maintaining signal integrity.

 (b)(ii) State one merit and one demerit of delta modulation.

• Merit: Requires lower bandwidth compared to other modulation schemes.
• Demerit: Suffers from slope overload distortion when signal changes rapidly.

 

3 (a)(i) Define cyclic redundancy check (CRC) with respect to error control schemes.

CRC is an error-detection technique that adds a sequence of redundant bits (checksum) to a transmitted message. The receiver performs a division operation to check for errors; if the remainder is zero, the data is considered error-free.

 (c)(i) State the three types of frames supported by the High-Level Data Link Control (HDLC).

1. Information (I-frames): Used for carrying data between devices.
2. Supervisory (S-frames): Used for error control and flow control.
3. Unnumbered (U-frames): Used for control and management functions.

4(c) State three phases in a circuit-switched network.

1. Call setup: A dedicated path is established between sender and receiver before communication begins.
2. Data transfer: The actual transmission of data takes place over the dedicated circuit.
3. Call termination: The connection is released once communication ends.

SECTION B: NETWORKING

5(a) Describe each of the following networking devices, citing the OSI layer of operations:

(i) Router:

• Operates at Layer 3 (Network Layer) of the OSI model.
• Routes packets between different networks using IP addresses.

(ii) Gateway:

• Operates at multiple layers (often at Layer 4 or higher).
• Converts protocols to enable communication between different network types (e.g., connecting an Ethernet network to a mainframe system).

 (b)(i) Define backbone as used in networking.

A backbone is the central part of a network that connects different segments, ensuring efficient communication between devices and networks. It typically has high bandwidth to support large amounts of traffic.

6 (a)(i) Define firewall with respect to network security.

A firewall is a security system that monitors and controls incoming and outgoing network traffic based on predefined rules. It protects networks from unauthorized access and cyber threats.

(ii) Describe each of the following types of firewalls:

1. Packet-filter firewall:

• Analyzes individual packets based on IP addresses, ports, and protocols.
• Allows or blocks traffic based on predefined rules.

1. Proxy firewall:

• Acts as an intermediary between users and the internet.
• Filters requests and hides internal network details for better security.

7(a)(i) Define frequency reuse with respect to cellular networks.

Frequency reuse is a technique where the same frequencies are assigned to different cells in a cellular network, separated by a sufficient distance to prevent interference. This allows for efficient spectrum usage and increased network capacity.

 (d) Describe each of the following techniques with respect to cellular wireless networks stating one merit of each:

(i) Soft handoff:

• A mobile device can connect to multiple base stations simultaneously during a call transition.
• Merit: Provides seamless call switching with minimal signal loss.

(ii) Cell-splitting:

• A large cell is divided into smaller cells to handle increased network traffic.
• Merit: Improves network capacity and coverage in densely populated areas.

8(a) Describe each of the following IEEE 802 protocol layers:

(i) Logical Link Layer:

• Responsible for error detection and flow control.

(ii) Medium Access Layer:

• Manages how devices access and share the network medium (e.g., CSMA/CD in Ethernet).

(iii) Physical Layer:

• Deals with the actual transmission of data over cables or wireless signals.

 (b) Describe Transmission Control Protocol (TCP) in data networks.

TCP is a connection-oriented protocol that ensures reliable data transmission between devices. It breaks messages into packets, ensures they arrive in order, and reassembles them at the destination. It also handles error correction and retransmission of lost packets.