What is signified by the term "over and out"?

The term "over and out" is used in radio communication to indicate that the speaker has finished their transmission and does not expect any response. This phrase combines two separate radio terminologies: "over," which signals that the speaker is finished speaking and is inviting a response, and "out," which indicates the end of the conversation, suggesting that the speaker will not be waiting for a reply.

Therefore, the choice stating "I'm done talking and do not expect a reply" accurately captures the meaning of "over and out." Understanding this is crucial for effective communication in contexts such as emergency response, aviation, or military operations, where clear signals of starting or finishing communication can save time and prevent misunderstandings.