FCC Exam Question: 19B2

What type of code is used for DSC transmissions?

A. A 7 bit code with a constant ratio of 4/3 between the 1s and 0s.
B. A 7 bit code followed by an error check character at the end.
C. A 10 bit code followed by an error check character at the end.
D. A 10 bit code with 7 bits used for information and 3 bits used for error correction.
Correct Answer: D

Explanation: Digital Selective Calling (DSC) transmissions employ a robust Forward Error Correction (FEC) scheme to ensure reliable communication, especially in noisy marine environments. The specific method used is a (10,7) code. This means that for every 7 bits of actual information, 3 redundant bits are added. These 3 extra bits are used by the receiving station to detect and correct single-bit errors within each 10-bit symbol. This integral error correction dramatically increases the probability of successful message reception, which is critical for safety-related communications. Options A, B, and C are incorrect because they misrepresent the bit length or the specific mechanism of error handling in DSC, which fundamentally relies on this 10-bit symbol with its embedded error correction.

Pass Your FCC Exam!

Study offline, track your progress, and simulate real exams with the GMDSS Trainer app.


Includes Elements 1, 3, 6, 7R, 8, and 9.