Lesson Notes By Weeks and Term v4 - SHS 3

Lesson Video

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Performance objectives

• Define guided and unguided network systems.
• Describe common network devices like routers, modems, and switches.
• Compare the advantages of different network systems.
• Analyze the role of these systems and devices in Ghana.

Lesson summary

This lesson introduces the fundamental ways information travels across computer networks. We use the internet every day—for WhatsApp, TikTok, checking WASSCE results, or streaming music—but how does the data actually get from our phones or computers to the rest of the world? It travels through physical cables (guided systems) or through the air as invisible waves (unguided systems). Understanding this distinction, and the special devices that manage this traffic, is crucial for anyone living in our modern, connected Ghana.

Lesson notes

This topic can be broken down into two main parts: the "roads" the data travels on (the media), and the "junctions and traffic controllers" that manage the data's journey (the devices). Part A: The "Roads" - Transmission Media

Transmission media are the pathways that carry data from one point to another. They are broadly classified into two categories. Guided (Wired) Media These are physical cables that provide a contained path for data signals to travel. Think of them like water pipes that guide water directly to a specific tap. Twisted-Pair Cable: Description: This is the most common type of networking cable, made of pairs of copper wires twisted together to reduce electrical interference. The cable you plug into a desktop computer in an internet cafe or school ICT lab (often blue or grey with a clear plastic clip called an RJ-45 connector) is a twisted-pair cable. Ghanaian Context: Used extensively in offices, schools (like your ICT lab), and internet cafes for creating Local Area Networks (LANs). Coaxial Cable: Description: This cable has a single copper core, surrounded by insulation, a metallic shield, and a plastic jacket. It can carry more data than twisted-pair and is more resistant to interference. Ghanaian Context: You have likely seen this! It's the same type of cable used for DSTV or GoTV satellite dish connections. Some internet service providers (ISPs) also use it to deliver internet to homes. Fibre-Optic Cable: Description: This is the "superhighway" of data transmission. It consists of very thin strands of glass or plastic that transmit data as pulses of light. It is incredibly fast, can carry vast amounts of data, and is not affected by electrical interference. Ghanaian Context: This is the backbone of Ghana's internet. The huge undersea cables that land at beaches in Accra, connecting Ghana to Europe and the rest of the world, are fibre-optic. Telecommunication companies like MTN and Vodafone use fibre-optic cables to connect their main cell towers and offices across the country. Unguided (Wireless) Media These media transmit data through the air or space as electromagnetic waves. There is no physical path. Think of this like a radio broadcast—the signal goes everywhere, and any receiver can pick it up. Radio Waves (Wi-Fi, Bluetooth): Description: These are used for short-to-medium range communication. Wi-Fi uses radio waves to create a Wireless Local Area Network (WLAN), allowing you to connect your phone or laptop to the internet without a cable. Bluetooth uses radio waves for very short distances, like connecting your phone to a wireless earpiece or speaker. Ghanaian Context: Extremely common. Every time you connect to a Wi-Fi network at home, in a restaurant, or use a personal hotspot ("MiFi"), you are using radio waves. Microwaves: Description: These are high-frequency radio waves that travel in a straight line. They are used for long-distance communication where laying cables is difficult. It requires line-of-sight between the transmitter and receiver. Ghanaian Context: The large dish-like antennas you see on top of MTN, Vodafone, and AirtelTigo cell towers are often microwave antennas. They are used to link one tower to another, carrying thousands of calls and data connections across cities and between towns. Part B: The "Traffic Controllers" - Networking Devices

These are the hardware components that connect computers and other devices, allowing them to share information. Modem (Modulator-Demodulator) What it is: A device that connects your home or office network to your Internet Service Provider (ISP), like Vodafone, MTN, or Surfline. What it does: It acts as a translator. The internet signal that comes through the phone line, fibre, or coaxial cable is an *analogue* signal. Computers, however, only understand *digital* signals. The modem MOdulates outgoing digital signals from your computer into analogue signals for the ISP's line and DEModulates incoming analogue signals into digital signals your computer can understand. Analogy: Imagine the ISP speaks Twi and your computer speaks Ga. The modem is the perfect translator who can speak both languages, allowing them to communicate. Router What it is: A device that connects multiple networks together and directs traffic between them. Most home routers connect your private Local Area Network (LAN) to the public internet (WAN). What it does: It acts as a traffic director or postmaster. When you want to visit a website, your request is a data "packet." The router looks at the destination address on the packet and decides the best path to send it on its way to the internet. When data comes back, the router ensures it goes to the correct device (e.g., to your laptop and not your brother's phone). It also assigns local IP addresses to devices on your network. Analogy: The router is like the main junction at Kwame Nkrumah Circle. It looks at every car (data packet) and directs it onto the correct road to reach its destination, whether that's Kaneshie, Accra Central, or Ring Road. Switch What it is: A device used to connect multiple devices together *within the same network* (a LAN). What it does: It is an intelligent traffic manager for a local network. When a computer sends data to another computer on the same network, the switch receives the packet, reads the specific destination address (the MAC address), and sends the data *only* to the intended recipient's port. This is very efficient. Analogy: A switch is like the receptionist in a large office building. When you call and ask for Mr. Mensah, the receptionist connects you directly to Mr. Mensah's extension. The call is private and doesn't disturb anyone else. Hub What it is: An older, less intelligent device also used to connect multiple devices on a LAN. What it does: It acts as a simple repeater or broadcaster. When it receives a data packet from one device, it doesn't look at the destination address. It simply copies the packet and broadcasts it to *every other device* connected to it. All devices receive the data, but only the intended recipient accepts it. This creates a lot of unnecessary network traffic and can be slow. Analogy: A hub is like someone standing in the middle of a crowded market and shouting a message for "Kofi." Everyone in the market hears the shout, but only Kofi responds. It's noisy and inefficient. Wireless Access Point (WAP) What it is: A device that allows wireless-capable devices (like phones, tablets, laptops) to connect to a wired network. What it does: It creates a Wireless Local Area Network (WLAN), commonly known as a Wi-Fi network. The WAP is connected to a router or switch via a cable, and it then broadcasts a Wi-Fi signal. Note: Most modern home "Wi-Fi routers" are actually combination devices: they are a modem, a router, a switch (with a few ports at the back), and a WAP all in one box. Network Interface Card (NIC) What it is: A piece of hardware inside a computer, printer, or smartphone that allows it to connect to a network. What it does: It is the passport for your device. Each NIC has a unique physical address, called a MAC (Media Access Control) address, burned into it. This address identifies your specific device on the network. A NIC can be for a wired connection (with an RJ-45 port for a cable) or wireless (with an antenna to pick up Wi-Fi signals). Without a NIC, a device cannot join a network. Broadband What it is: This is not a device, but a term for a high-speed, always-on internet connection. It's a type of service, not a piece of hardware. Fibre-optic, DSL, and 4G/5G mobile data services are all types of broadband. How it relates: You use devices like a modem and a router to access a broadband internet service provided by an ISP like Vodafone or MTN.

Guided Practice (With Solutions)

Evaluation guide

• Demonstrate basic
• knowledge and
• understanding of guided and
• unguided network systems Describe Common ly used Devices (e.g., broadband, modems, wireless