What word(s) must be used at the end of a radio transmission to indicate that a response is expected?

The term "OVER" is used at the end of a radio transmission to signify that the speaker has finished their message and is expecting a response. This indicates to the listener that it is their turn to reply, creating a clear exchange of information. The use of "OVER" is a standard in radio communication protocol, ensuring that all parties understand when communication is complete and that dialogue can continue. This clarity is essential in ensuring effective communication, particularly in operations that demand quick and precise exchanges, such as train dispatching.