Which statement about ARQ transmissions is true in SITOR (NBDP) communications?

In SITOR (Single-Interleaved Telex Over Radio) communications, which is a mode of the Narrow Band Digital Radio (NBDP), the process of Automatic Repeat reQuest (ARQ) involves the transmission of data in specific blocks. The true statement regarding ARQ transmissions is that they are made in data groups of three-character blocks. This method allows the system to manage data efficiently and ensures that each block of information can be acknowledged individually.

When the receiver identifies that a block has been received correctly, it sends back an acknowledgment for that specific block, allowing the sender to release that part of the message. If the block is not acknowledged, the sender will retransmit that three-character group, facilitating a more reliable communication process.

The other statements do not accurately represent the principles of ARQ in SITOR communications, where block sizes and acknowledgment processes are specifically structured to enhance the efficiency and integrity of data transfer.