Which command signifies the end of a TELEX transmission in ARQ communications?

In ARQ (Automatic Repeat reQuest) communications, the command that signifies the end of a TELEX transmission is "KKKK." This command serves a specific purpose within the context of signaling and communication protocols for maritime radio communication systems, particularly in the GMDSS (Global Maritime Distress and Safety System).

The "KKKK" command is utilized to indicate the conclusion of a message or a series of messages. It acts as an acknowledgment that the transmission has been completed and that the receiver can now process the information that was sent. This is crucial in preventing any ambiguity about whether additional information is still forthcoming or if transmission has fully concluded.

Other commands listed, such as "AAB," "WRU," and "BRK+," serve different functions in the communication protocol. "AAB," for example, is often related to specific signal requests or acknowledgments, "WRU" is used to request the identity of the other station, and "BRK+" can represent break signals in text transmission but does not signify the end of transmission. The clarification provided by the "KKKK" command helps streamline communication and ensures that all parties clearly understand when a transmission has ended, facilitating a more efficient exchange of information.