What must you say to end a transmission if you expect a response?

When ending a transmission and expecting a response, using "Over" is the correct approach. This term indicates to the listener that your transmission is complete, and you are awaiting their reply. It effectively communicates that the communication is not finished—instead, it invites the other party to respond.

In radio communication protocols, "Over" specifies the expectation of continuation in the dialogue, making it crucial for effective exchanges, especially in contexts like rail communications. Using "Over" helps ensure that both parties understand who will speak next, promoting clarity in the conversation.

This contrasts with other terms. "Goodbye" signals a complete end to the conversation without expecting further communication. "Clear" often indicates that a channel is free for use by others, and "Out" implies that the speaker is ending communication altogether, which does not expect a response. Therefore, choosing "Over" correctly aligns with the expectation of continued dialogue.