Answer 7—Multiple bit errors in a Hamming code cause trouble. Two bit errors will always be detected as an error, but the correction logic will flip the wrong bit, resulting in gibberish. If there are more than 2 bits in error, the received codeword may appear to be a valid one (but different from the original), which means that the error may or may not be detected.

In any case, the error-correcting logic can’t tell the difference between single-bit errors and multiple-bit errors, so you can’t rely on the corrected output.

Contributor: David Tweed