Choose a transmission method for a scenario
Combine distance, direction and data flow to justify a suitable transmission arrangement.
This sequence follows Cambridge IGCSE Computer Science 0478, 2026–2028 syllabus Version 6. It covers subject content sections 2.1–2.3 only. The separately published 2029–2031 syllabus is not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding.
Before you begin
- No programming language is required. Be comfortable with place value and multiplication; each lesson introduces the computer-science notation it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which two independent properties can describe a data link?
What you will learn
- Select serial or parallel transmission from a context
- Select simplex, half-duplex or full-duplex from a communication need
- Support a choice with a benefit and limitation
Decide what the scenario requires
First ask how far the devices are apart and whether several bits must be sent simultaneously. A short internal bus can use parallel transmission; a longer link commonly favours serial transmission.
Apply and check the rule
Then ask whether data flows one way, both ways in turns, or both ways simultaneously. Use simplex, half-duplex or full-duplex to describe that direction. A complete answer names the method and links it to the scenario rather than listing a generic advantage.
Pause and explain
A one-way sensor signal is sent over a long cable. Which combination is most appropriate in a basic comparison?
Worked example
A remote sensor sends readings to a base station several kilometres away; the base station does not send commands back. Suggest the direction mode and a bit-transmission method.
Show the worked solution
- Only the sensor sends, so the direction is simplex.
- A long distance generally favours serial rather than many parallel data wires.
- State both choices and link each to a requirement.
Answer Simplex serial transmission is suitable: data travels one way over the long link, and serial uses fewer data lines.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A keyboard sends input to a computer. Give a likely direction mode and explain.
Give me a hint
Focus on whether the keyboard receives information back over that input path.
Compare my reasoning
- The keyboard sends key data to the computer.
- The input path is treated as one-way for this example.
- That is simplex communication.
Simplex, because the keyboard sends data to the computer in one direction.
Look for these in your work
- Direction identified
- One-way reason stated
A two-way radio lets users take turns transmitting. State the mode and one consequence.
Give me a hint
Two-way does not necessarily mean simultaneous.
Compare my reasoning
- The direction mode is half-duplex.
- Only one participant can transmit at a time, so users must take turns.
Half-duplex; users can communicate both ways but cannot transmit simultaneously.
Look for these in your work
- Mode correct
- Consequence stated
A short connection between processor and memory needs several data bits transferred together. Recommend serial/parallel and state one reason the choice may not suit a much longer cable.
Give me a hint
Use the short distance and multiple-bit requirement.
Compare my reasoning
- Parallel can transfer several bits at once over multiple lines.
- A short internal link can make the wiring and timing manageable.
- A longer cable can increase wire cost, interference and synchronisation problems.
Parallel may suit the short internal connection because it transfers a group of bits simultaneously. On a long cable, the extra wires and timing/interference issues can outweigh that benefit.
Look for these in your work
- Parallel method selected
- Context linked
- Distance limitation explained
Common mistakes
- Giving only 'serial' when the question also asks about direction
- Choosing full-duplex when the device never sends back
What can you explain now?
A device must send and receive at the same time. Which property should be full-duplex?
Compare with the explanation
The direction mode
Full-duplex describes simultaneous two-way communication, not serial versus parallel.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Why should an answer distinguish serial/parallel from simplex/duplex?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.