Which code is used to indicate a need to repeat a message?

The code that indicates a need to repeat a message is known to be 10-9. This code is a part of the ten-codes (or ten signals) used in radio communication, which are widely adopted to streamline communication and ensure clarity, especially in noisy or high-pressure environments.

When a radio operator calls for 10-9, it clearly communicates to the other party that the previous message was not understood or was missed, and it needs to be repeated. Using standardized codes like this helps avoid confusion, as everyone familiar with the communication protocols will know precisely what is being requested.

The other codes have different meanings and are used for other situations: 10-4 indicates acknowledgment, 10-6 refers to a request to remain silent, and 10-19 is used to convey a message to return to a specific location. Each code serves its own purpose, but in this instance, when a message needs repeating, 10-9 is the appropriate choice.