A special transmission format limited to video signals
A system used to encrypt command signals to an amateur radio satellite
An error correction method in which the receiving station detects errors and sends a request for retransmission✓Correct answer
A method of compressing data using autonomous reiterative Q codes prior to final encoding
Explanation
ARQ stands for Automatic Repeat reQuest: the receiving station checks each block for errors and, when a block fails, asks the sender to transmit it again, so the data eventually arrives intact. It corrects errors by retransmission rather than by compression or encryption.