Explain data communication and discuss the transmission media used in computer networks.

1. 1 · Open in two lines. Data communication is the exchange of data between two devices through a transmission medium, following agreed rules.
2. 2 · Draw the model. [Diagram: Sender → encoder/modem → transmission medium → decoder/modem → Receiver]
3. 3 · Explain the elements. Sender, receiver, message, medium and protocol (agreed rules, e.g. TCP/IP).
4. 4 · Guided (wired) media.
   • Twisted pair: cheap, office LANs, limited distance.
   • Coaxial: shielded, cable TV.
   • Fibre optic: light pulses, very fast, long distance, no interference.
5. 5 · Unguided (wireless) media.
   • Radio: Wi-Fi, Bluetooth, 4G/5G.
   • Microwave: tower-to-tower links in line of sight.
   • Satellite: wide coverage, some delay.
   • Infrared: very short range.
6. 6 · Choosing a medium. Consider cost, speed, distance, security, interference and the need for mobility.
7. 7 · Sri Lankan business example. SLT-Mobitel fibre broadband, Dialog 4G wireless broadband, and undersea fibre cables linking Sri Lanka to the world.
8. 8 · Close in one line. Most business networks mix wired media for speed with wireless media for mobility.

Scoring tip: Name each medium with one advantage, one limitation and one use.