Difficulty: Medium
Correct Answer: None of the above
Explanation:
Introduction / Context:
Serial modem throughput depends on baud rate (symbols/s) and framing. In typical asynchronous links, each character is wrapped with start/stop bits. Calculating transfer time requires converting characters to bits, dividing by the effective bit rate, and comparing against the choices.
Given Data / Assumptions:
Concept / Approach:
Total bits = characters * bits/character. Time = total bits / bit rate. With 8-N-1, each character consumes 10 line bits. Therefore, 2000 chars require 20,000 bits. At 1,200 bit/s, time ≈ 16.67 s. None of the listed numeric options equals 16.67 exactly, so the correct choice among those presented is “None of the above.”
Step-by-Step Solution:
bits_per_char = 10 (8-N-1).total_bits = 2000 * 10 = 20,000 bits.time_seconds = 20,000 / 1,200 ≈ 16.67 s.Compare to options: 2, 12, 20, 120 → none matches ≈16.67 s.
Verification / Alternative check:
If parity were used (8-E-1 → 11 bits/char), time would be ≈ 18.33 s; if one incorrectly ignores start/stop (8 bits only), time ≈ 13.33 s. These also do not match the provided options, reinforcing “None of the above.”
Why Other Options Are Wrong:
12 s: Implies only 8 bits/char at 1,333 bit/s or similar incorrect assumptions.
Common Pitfalls:
Forgetting framing overhead in asynchronous links and equating baud to characters per second. Always multiply by bits per framed character.
Final Answer:
None of the above
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