TechTayari

S6 · Computer Studies I · Grade 10 · ages 15–16

Data Communication

How data travels

Grade 10 · 2.1 Data communication · 2.2 Data Transmission MediaCBE strandFree · works offline

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The full lesson adds narration, an interactive mission and a 10-question bank, and the quiz explains any mistakes.

The five parts of communication

Every data communication has five parts: a sender, a receiver, the message (the data), a transmission medium that carries it (cable or radio waves), and a protocol: the agreed rules both sides follow so they understand each other. An M-Pesa message from one phone to another uses all five.

Direction: simplex, half-duplex, full-duplex

Simplex sends one way only, like a radio broadcast. Half-duplex sends both ways but one at a time, like a walkie-talkie ("over!"). Full-duplex sends both ways at once, like a phone call.

Protocols and layered models

Protocols are rules for formatting, addressing and checking data. The internet uses the TCP/IP suite: IP addresses and routes packets; TCP makes sure they all arrive in order. The OSI model describes networking in seven layers, from the physical cable up to the application you use.

Guided media: cables

Guided media send signals along a physical path. Twisted-pair copper cable (as in Ethernet) is cheap and common. Coaxial cable is used for TV and some internet connections. Fibre-optic cable carries light, so it is very fast, crosses long distances and is not disturbed by electrical interference. It links Kenya to the world under the sea.

Unguided media and bandwidth

Unguided (wireless) media use radio waves, microwaves, infrared or satellite links: Wi-Fi, Bluetooth and mobile data. Bandwidth is how much data a link can carry per second (for example 100 Mbps). A modem modulates digital data into a signal for the medium and demodulates it back at the other end.

Key points

  • Communication needs a sender, a receiver, a message, a medium and a protocol.
  • Simplex is one way, half-duplex takes turns, and full-duplex goes both ways at once.
  • Protocols are the agreed rules; the internet uses TCP/IP.
  • Twisted pair is cheap, coaxial carries TV, and fibre carries light very fast.
  • Wireless media include Wi-Fi, Bluetooth, mobile data and satellite.
  • Bandwidth is how much data a link carries per second.
  • A modem modulates and demodulates signals between devices.

Try it for real: Trace a message

  • Look at your home or school internet: is it fibre, mobile data, or another kind? Ask a teacher or parent.
  • Run a speed test on a phone or computer and note the download speed in Mbps.
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