Which statement about SITOR (NBDP) ARQ mode is true?

In SITOR (Simplex Telex Over Radio), which operates using the Narrow Band Direct Printing mode (NBDP) and Automatic Repeat reQuest (ARQ), the correct statement is that each data block consists of three characters. This format is integral to the SITOR ARQ method, allowing for efficient handling and transmission of data.

In SITOR ARQ mode, the data is structured into blocks to facilitate the monitoring and retransmission of messages. Each block being three characters in length is designed to balance the efficiency of data transmission with the requirements for error checking and correction. This structure allows for the identification of individual blocks and aids in the acknowledgment process of received data, which is a key feature of ARQ systems. This makes the method robust for communication in maritime environments where message integrity is crucial.

Understanding this aspect of SITOR ARQ mode is essential for efficient communication and error management, as well as grasping the overall functionality of the system in a maritime context.