Subelement B: MF-HF-DSC-SITOR (NBDP) Equip. & Operations— Topic :
Question 20B2
Element 9 (GMDSS Maintainer)What statement is true regarding the exchange between two stations engaged in SITOR (NBDP) communications?
Explanation
SITOR ARQ (Automatic Repeat reQuest) is an error-correcting mode primarily used for point-to-point communications. In this mode, the Information Sending Station (ISS) transmits data in blocks, typically three characters at a time. The Information Receiving Station (IRS) checks each received block for errors, often using parity bits within the block. If the IRS detects an error, it automatically requests the ISS to retransmit that specific block. This process ensures extremely high data integrity.
Option A describes SITOR's FEC (Forward Error Correction) mode, where characters are sent twice for redundancy in one-way transmissions, not ARQ. Option B is partially correct but less precise and complete than C in describing the specific roles and error checking mechanism. Option D is incorrect because broadcasts, like Maritime Safety Information, are one-way and do not use ARQ, which requires a two-way link for retransmission requests; instead, they utilize FEC mode.
Related Questions
1A6 Using a frequency counter with an accuracy of 5 ppm — which of the following are within legal tolerance for the frequencies of 156.875 MHz and 157.200?20B1 Which of the following statements concerning SITOR (NBDP) communications is true?20B3 Which of the following is true of SITOR (NBDP) ARQ mode:20B4 Which of the following keystrokes or characters follows most commands in ARQ communications when working an automated Coast Station?20B5 Which characters are sent by the ship station to indicate a desire to send a message via a direct connection to a shoreside TELEX subscriber?