In APCO 10-codes, 10-3 means "Stop Transmitting" or "Cease Transmission."
It is used to instruct others to stop communicating temporarily, often because the radio frequency needs to be kept clear for important or emergency traffic. For example, in a situation where critical communication needs to occur without interference, a dispatcher or a commanding officer might issue a 10-3 to stop any non-essential transmissions:
- Dispatch: "All units, 10-3, emergency traffic only."
In this case, only critical communications should be transmitted until the situation is resolved.