Except when transmissions relate to switching operations, when a radio communication is complete and no response is expected, the transmitting employee on the train must say:

• A. The required identification followed by "Over"
• B. The required identification followed by "Out"
• C. The end of transmission
• D. Done

Answer: (B)

Closing a radio call is about signaling that you’re done and don’t expect a reply. When the transmission is finished and no answer is needed, you must give the required identification and then say “Out.” This makes it clear to everyone listening that the channel is closed for that call and no further response will follow. Using “Over” would suggest you’re asking for a reply, which isn’t the case here, so it would cause undue waiting or confusion. Phrases like “The end of transmission” or “Done” aren’t standard railroad radio terms and could be misinterpreted. The exception is during switching operations, where a response may be required to coordinate actions, but outside of switching you end with identification plus “Out.”