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Data Transmission, Error Checking and Encryption: Question 10

Syllabus 2.1

Multiple choice 1 mark

Two employees use a video-calling app during a meeting. Their laptops are connected to the office network by Ethernet cables that support full-duplex transmission. Throughout the call, each laptop continuously sends its own webcam video and audio to the other laptop, while at the same time continuously receiving the other laptop's webcam video and audio, for the whole duration of the call.

Which duplex mode is being used for this video call?

Choose an answer to check it, then compare with the worked solution below.
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Worked solution

Step 1: Recall the duplex modes

  • Simplex: data can only travel in one direction, never the other.
  • Half-duplex: data can travel in both directions, but only one direction at a time.
  • Full-duplex: data can travel in both directions at the same time, continuously.

Step 2: Match the scenario to the correct mode

Each laptop in the video call continuously sends its own webcam video and audio while continuously receiving the other laptop’s webcam video and audio, for the entire call, with neither direction ever having to wait for the other. This simultaneous two-way flow is the defining feature of full-duplex transmission. It rules out simplex, since data clearly travels both ways, and it rules out half-duplex, since neither direction has to pause while the other is active.

Step 3: Confirm the match

Option D, serial transmission, describes how many bits travel at once along a connection, not the direction data can travel, so it does not answer the question being asked.

Final answer

The video call uses full-duplex transmission, option C.