Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Information and communication technology (ICT)
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Information and communication technology (ICT)
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Basic Electronics
Class: Senior Secondary 3
Term: 2nd Term
Week: 9
Theme: Communication System
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Explain the operations of telephone. Explain the operations of in ternet system. Explain the operations of Global System Mobile (GSM) phones.
This section provides detailed explanations of the core ICT systems, focusing on their operational principles and components. This section outlines practical activities for both teachers and students to facilitate understanding and engagement.
Teacher Activities: Introduction (10 minutes): Begin by asking students to name common communication devices they use daily. Lead a brief brainstorming session on "How do these devices work?" (e.g., how does my voice get from my phone to someone else's?). Introduce the topic of ICT and its relevance, emphasizing its impact on Nigerian lives (e.g., mobile banking, online market places, e-learning during strikes). Clearly state the learning objectives for the lesson. Explanation of Telephone Operations (20 minutes): Use an actual old landline telephone (if available) or clear diagrams to point out components like the microphone, speaker, and keypad. Explain the concept of transducers (sound to electrical, electrical to sound) in detail. Draw and explain the block diagram of a telephone system, tracing the path of a call from dialing to connection. Discuss the roles of the local loop, exchange, and trunk lines, relating them to existing infrastructure (even if diminished) in Nigerian towns. Explanation of Internet System Operations (25 minutes): Start by defining the Internet as a "network of networks." Explain key terms: client, server, IP address, DNS, packets. Use analogies (e.g., DNS as a phonebook, packets as letters with address labels). Describe the roles of Modems, Routers, and ISPs. Ask students to identify their own ISPs. Illustrate the data flow when accessing a website using a block diagram. Emphasize the journey of data packets. Discuss different types of internet access in Nigeria (e.g., mobile data, fibre optic where available). Explanation of GSM Phone Operations (30 minutes): Begin by asking students about their experience with GSM phones (e.g., "What happens when you switch on your phone?"). Introduce the main components of a GSM network (MS, BTS, BSC, MSC, HLR, VLR, AuC, EIR). Explain the function of each with clear examples. Use a detailed block diagram of the GSM network to visually represent the interconnectedness of components. Walk students through the step-by-step process of making a GSM call, including registration, dialing, call setup, and handoff. Discuss the importance of the SIM card and IME
I. Guided Practice and Assessment (15 minutes): Facilitate a question-and-answer session to check for understanding. Assign guided practice questions for students to attempt in class. Provide feedback and lead discussions on solutions.
Wrap-up and Homework (5 minutes): Summarize the key concepts covered. Assign independent practice questions as homework.
Student Activities: Brainstorming: Students will participate in brainstorming sessions about communication devices and their uses.
Note-taking: Students will take comprehensive notes during teacher explanations.
Active Participation: Students will ask questions, answer questions, and contribute to class discussions.
Diagram Drawing: Students will practice drawing simple block diagrams for the telephone system, internet system, and GSM network as the teacher explains and illustrates them.
Group Discussion: Students may be grouped to discuss the impact of each technology on their local community or to explain a specific component's function to their peers.
Problem Solving: Students will attempt guided practice questions and compare their answers with provided solutions.
Observation: If an old telephone is available, students will observe its physical components.
This translation is necessary because: Human Readability: Humans find it much easier to remember meaningful domain names (like `naijamarket.com`) than long numerical IP addresses (like `104.26.2.195`).
Network Routing: Computers and network devices (like routers) identify and locate resources on the internet using IP addresses, not domain names. Packets are routed across the internet based on their destination IP address. DNS acts as the "phonebook" that translates human-friendly names into machine-readable addresses, enabling efficient data routing.
Question 3 (GSM Phone Operations): Mrs. Ade needs to make an urgent call to her daughter in another state using her GSM phone. She presses the call button after dialing the number. a. Describe the initial steps the GSM network takes to locate and connect to her daughter's phone. b. If Mrs. Ade walks away from her current location during the call and connects to a different base station, explain what network process ensures her call is not dropped.
Solution 3: a.
Initial Steps for Call Connection: Dialing & Signal Transmission: When Mrs. Ade presses the call button, her mobile phone (Mobile Station, MS) sends the dialed number and her own identification (from her SIM card) as digital radio signals to the nearest Base Transceiver Station (BTS).
BSC Forwarding: The BTS forwards this information to its Base Station Controller (BSC).
MSC Processing: The BSC then sends the call request to the Mobile Switching Center (MSC), which is the core switching element.
Subscriber Verification: The MSC queries its Visitor Location Register (VLR) and Mrs. Ade's Home Location Register (HLR) to verify her subscription status, services, and current location.
Recipient Location: The MSC then determines the location of Mrs. Ade's daughter's phone. It queries the HLR to find out which MSC is currently serving the daughter. The daughter's serving MSC then sends a "paging" signal across the BTSs in the daughter's last known location area to find her phone.
Call Setup: Once the daughter's phone responds to the paging, a dedicated radio channel is established between her phone and her serving BTS, and a connection is then established between the two MSCs (or within the same MSC if they are in the same service area), linking Mrs. Ade's phone to her daughter's. b.
Handoff Process: The network process that ensures Mrs. Ade's call is not dropped when she moves and connects to a different base station is called Handoff (or Handover).
Monitoring Signal Strength: As Mrs. Ade moves, her phone continuously monitors the signal strength from her current serving BTS and also from neighbouring BTSs. It reports this information back to the BS
C. Decision and Execution: When the signal strength from the current BTS weakens significantly, and a stronger signal from an adjacent BTS is detected, the BSC (or sometimes the MSC for inter-BSC handovers) initiates a handoff. It allocates a new radio channel on the new, stronger BTS to Mrs. Ade's phone. * Seamless Transfer: The network intelligently and quickly transfers the call's connection from the old BTS to the new BTS, often within milliseconds. This process is designed to be seamless, ensuring that Mrs. Ade's conversation with her daughter continues uninterrupted, and she is unaware of the switch between base stations. These questions directly target the performance objectives and are designed to be worked through in class with teacher guidance.
Question 1 (Telephone Operation): A rural community in Nigeria still relies on a single landline telephone at the community centre. When a community member picks up the handset to make a call, they hear a dial tone. a. Explain the electronic process that generates this dial tone from the telephone exchange. b. Describe what happens electronically when the person speaks into the phone, explaining the role of the microphone.
Solution 1: a.
Dial Tone Generation: When the community member picks up the handset, the local loop circuit (the copper wire connecting the phone to the telephone exchange) is completed. This "off-hook" condition is detected by the line card in the telephone exchange (central office). The exchange then sends a specific audio frequency signal (the dial tone) back to the phone through the local loop, indicating that the line is ready for dialing. This is typically a steady tone, often a combination of 350 Hz and 440 Hz tones. b.
Microphone Operation: When the person speaks into the phone, the sound waves from their voice strike a diaphragm within the phone's microphone. The diaphragm vibrates according to the pattern of the sound waves. In many older telephones, behind this diaphragm is a chamber filled with carbon granules. The vibrations of the diaphragm cause the carbon granules to be alternately compressed and decompressed. This compression and decompression change the electrical resistance of the carbon granules. A steady DC current flows through these granules from the telephone line. As the resistance changes, the current flowing through the circuit varies in amplitude, creating an electrical signal that is an analog representation of the speaker's voice. This electrical signal is then transmitted through the telephone network.
Question 2 (Internet System): Mr. Emeka, a trader in Aba, wants to use his laptop to access an online market (`www.naijamarket.com`) to check prices. He connects his laptop to a modem, which is then connected to his ISP. a. Explain the primary role of the modem in this setup. b. Describe how `www.naijamarket.com` is translated into an IP address, and why this translation is necessary.
Solution 2: a.
Role of the Modem: The modem (Modulator-Demodulator) is crucial because it acts as a bridge between Mr. Emeka's laptop (which uses digital signals) and the Internet Service Provider's (ISP) network (which often uses analog signals, particularly over traditional phone lines or cable, or specific digital line coding).
Modulation: When Mr. Emeka's laptop sends digital data (e.g., the request to access `www.naijamarket.com`), the modem converts these digital signals into analog signals suitable for transmission over the physical transmission medium (e.g., telephone line, cable line).
Demodulation: Conversely, when analog signals containing the website's data arrive from the ISP's network, the modem converts these analog signals back into digital signals that the laptop can understand and process. Without the modem, the digital data from the laptop could not be transmitted over the analog infrastructure of the ISP, and vice-versa. b.
DNS Translation: The translation of `www.naijamarket.com` into an IP address is performed by the Domain Name System (DNS).
Process: When Mr. Emeka types `www.naijamarket.com` into his browser, his laptop first checks its local cache. If not found, it sends a request to a DNS server (typically provided by his ISP). This DNS server then queries other DNS servers in a hierarchical manner until it finds the authoritative DNS server for `naijamarket.com`, which stores the corresponding IP address (e.g., 104.26.2.195). The IP address is then sent back to Mr. Emeka's laptop.
Necessity: This translation is necessary because: Human Readability: Humans find it much easier to remember meaningful domain names (like `naijamarket.com`) than long numerical IP addresses (like `104.26.2.195`).
Network Routing: Computers and network devices (like routers) identify and locate resources on the internet using IP addresses, not domain names. Packets are routed across the internet based on their destination IP address. DNS acts as the "phonebook" that translates human-friendly names into machine-readable addresses, enabling efficient data routing.
Question 3 (GSM Phone Operations): Mrs. Ade needs to make an urgent call to her
Mobile Banking and Digital Payments (Economy): GSM phones and the internet are foundational for mobile banking services (USSD codes, banking apps) prevalent across Nigeria. Students can learn how these technologies facilitate financial inclusion, allowing remote communities to access banking services, make payments, and transfer money, significantly boosting local economies by reducing the need for physical branches and cash. E.g., a farmer in rural Katsina can receive payment for produce via a mobile transfer. E-commerce and Online Entrepreneurship (Economy/Social): The internet enables platforms like Jumia, Konga, and smaller social media businesses (Instagram, WhatsApp shops) where Nigerians buy and sell goods and services. Understanding internet operations helps students appreciate how data security, reliable connections, and server infrastructure support these burgeoning businesses, providing employment and consumer convenience. E.g., a fashion designer in Lagos can sell their designs to customers across Nigeria and even abroad via an online store. Educational Access and Remote Learning (Education/Social): During periods of school closures or for distance learning initiatives (e.g., National Open University of Nigeria - NOUN), the internet provides access to educational resources, online courses, and collaborative tools. GSM networks facilitate this through mobile data access, enabling students in areas with limited broadband infrastructure to learn. E.g., students in a remote village can access educational videos or participate in online classes using their smartphones. Emergency Communication and Disaster Management (Social/Community): Telephones (especially GSM) are critical during emergencies for reporting incidents (fire, accident, crime) to authorities (e.g., 112 emergency number). The underlying network infrastructure ensures these vital calls can connect, aiding rapid response and community safety. Internet-based platforms (social media, news sites) also disseminate crucial information during crises.