AeroLab Reading room

CS / IGCSE

Data transmission and error detection

Serial and parallel transmission move bits using different channel arrangements. Simplex, half-duplex and full-duplex describe permitted directions, not the number of wires.

Learning objectives

The big idea

Serial and parallel transmission move bits using different channel arrangements. Simplex, half-duplex and full-duplex describe permitted directions, not the number of wires.

Packets include addressing and control information. Parity, checksums and echo checks detect particular errors; automatic repeat requests recover by retransmission. Detection is not the same as prevention or correction.

Worked example

With even parity, data 1011 needs which parity bit?

Follow the solution

The data has three 1s; adding 1 makes the total count even.

Investigate and explain

Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.

Use the prediction activity below; a local model appears only where it supports this topic.

Open the interactive investigation

Check your understanding

1. What does full-duplex communication allow?

  1. One direction only
  2. Both directions but never simultaneously
  3. Both directions at the same time
Check the answer and reasoning

Both directions at the same time

The defining feature is simultaneous bidirectional transmission.

2. With even parity, data 1011 needs which parity bit?

  1. 1
  2. 0
  3. No bit can work
Check the answer and reasoning

1

The data has three 1s; adding 1 makes the total count even.

3. Can a single parity bit detect every possible corruption?

  1. Yes
  2. No
  3. Only with serial transmission
Check the answer and reasoning

No

An even number of changed bits can leave the parity unchanged.