Multiple choice

The probability that a single bit will be in error on a typical public telephone line using 4, 800 bps modem is 10 to the power 3. If no error detection mechanism is used, residual error rate for a communication line using 9 bit frames is equal to

  1. 0.003

  2. 0.009

  3. 0.991

  4. 0.999
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a 9-bit frame with bit error probability 0.001, the probability of NO errors is (1-0.001)^9 ≈ 0.991. Therefore, residual error rate (probability of at least one error) is 1 - 0.991 = 0.009.

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