Network Components and Social Media
Senior 2 · ICT
Network Components and Social Media
Lesson 2 of 4
22 min
Every message you send has to travel along something. Inside a school lab it moves as electrical signals along copper cables. Between Kigali and the districts it moves as flashes of light inside glass fibres: Rwanda's national fibre-optic backbone is more than 3,000 km long and was largely finished by 2011. Because Rwanda is landlocked, fibre links through Kenya and Tanzania connect the country to undersea cables in the Indian Ocean. Around your phone, data moves as invisible radio waves.
The path that data travels along is called the transmission medium (plural: media). The medium you choose decides the speed, the distance, the cost and how reliable the link is.
A twisted pair cable contains pairs of insulated copper wires twisted around each other; a network cable usually has four pairs. The twisting reduces interference (unwanted electrical noise from outside) and crosstalk (signal leaking from one pair into the pair next to it).
A network twisted pair cable ends in an RJ-45 plug. One Ethernet run of twisted pair should be no longer than about 100 metres.
A coaxial cable has four layers. From the centre outwards they are: a copper core that carries the signal, a plastic insulator, a braided metal shield that blocks interference, and an outer plastic jacket. Coaxial cable connects a satellite dish or TV antenna to a decoder, links CCTV cameras, and carries some cable-internet services. It is better shielded than UTP, but thicker and stiffer.
A fibre optic cable carries data as pulses of light through very thin strands of glass or plastic. Each strand has a core that carries the light and a cladding around it that reflects the light back into the core, so the light stays trapped inside the strand.
| Medium | How it works | Typical range | Everyday use |
|---|---|---|---|
| Infrared (IR) | Invisible light; needs a clear line of sight | A few metres; cannot pass through walls | TV remote control |
| Bluetooth | Short-range radio waves; devices are paired first | Up to about 10 metres in its most common mode | Wireless earphones, sending files between phones, wireless mouse |
| Wi-Fi | Radio waves between devices and an access point | Tens of metres indoors | Laptops and phones joining a school or home network |
Bluetooth links a few devices close to one person, forming a personal area network (PAN). Wi-Fi builds a wireless local area network (WLAN) covering a home, a classroom or a building. Mobile data (4G and 5G) from MTN and Airtel is another wireless medium; it covers whole regions from tall masts.
| Twisted pair (UTP) | Coaxial | Fibre optic | |
|---|---|---|---|
| Signal | Electricity | Electricity | Light |
| Cost | Low | Medium | High |
| Distance | About 100 m per run | A few hundred metres | Many kilometres |
| Interference | Some (reduced by twisting) | Low (shielded) | None from electricity |
Tip
Memory hook: twisted pair is twisted to fight noise; coax is one core inside a shield; fibre carries light. For wireless range, remember IR < Bluetooth < Wi-Fi: infrared needs you to point, Bluetooth fills a room, Wi-Fi fills a building.
Name the layer of a coaxial cable that blocks outside interference.
Solution: The braided metal shield. It wraps around the insulator and the core, and the outer jacket covers it.
A health centre in Rusizi needs a cable link to a district hospital 12 km away. Which medium should it use, and why?
Solution: Fibre optic. Only fibre carries data over many kilometres without the signal fading, and a link made of light is not disturbed by electrical interference from storms.
Gatete's TV remote works from the sofa but not from the kitchen, which is behind a wall. Explain why.
Solution: The remote uses infrared, which needs a clear line of sight. The wall blocks the infrared light, so the signal never reaches the TV.
Why are the copper wires in a network cable twisted in pairs?
Solution: Twisting means that outside noise affects both wires of a pair almost equally, so the noise cancels out at the receiver. It also reduces crosstalk between neighbouring pairs.
Umutoni wants to send a photo from her phone to a friend's phone right next to her, without using mobile data. Which wireless medium suits this?
Solution: Bluetooth. The phones are close together, they can pair directly, and no internet connection is needed.
Summary
Sources and credits
The comparison tables, worked examples and practice items were written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
