Exam-style question
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A timing diagram shows two channels X and Y sharing a medium. The diagram consists of a repeating cycle of four equal time slots. In slots 1–2, channel X transmits; in slots 3–4, channel Y transmits. A sync pulse is shown at the start of each cycle. Interpret the diagram and explain the purpose of the sync pulse.
Model answer
What a good answer should say
- The diagram shows a two‑channel TDM system where channel X occupies the first two slots and channel Y the last two.
- The sync pulse marks the start of each cycle, allowing receivers to reset their timing and know when a new cycle begins.
- This ensures that the data from each channel is sampled at the correct times and prevents overlap.
- Thus the sync pulse is essential for maintaining the timing structure of the multiplexed signal.
Explanation
Why this works
evidence: a timing diagram with four equal slots, X transmitting in slots 1–2, Y in slots 3–4, and a sync pulse at the start of each cycle; interpretation: the diagram demonstrates a two‑channel TDM scheme with unequal slot allocation; implication: the sync pulse provides a reference point for receivers to align their sampling windows and avoid data overlap; conclusion: the question tests the student’s understanding of how timing diagrams represent TDM and the function of sync pulses.
Common mistake
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