What must be used at the end of a radio transmission to indicate no response is expected?

The phrase "OUT" followed by required identification is used at the end of a radio transmission to indicate that the transmission is complete and no response is expected. This standard practice in radio communication helps clarify that the sender has finished their communication and is not awaiting a reply.

Using "OUT" is particularly important because it signals to the receiver that they can now respond or take action without feeling the need to respond back to the initial communication. This helps to maintain clarity and efficiency in radio operations, especially in busy environments where multiple transmissions may occur simultaneously.

Proper identification enhances communication effectiveness, ensuring that the parties involved in the transmission are clearly identified, which is vital for operational safety and awareness.