47 C.F.R. § 80.328 Urgency message.
Title 47 - Telecommunication
(a) The urgency signal and call, and the message following it, must be sent on one of the international distress frequencies. Stations which cannot transmit on a distress frequency may use any other available frequency on which attention might be attracted. (b) Mobile stations which hear the urgency signal must continue to listen for at least three minutes. At the end of this period, if no urgency message has been heard, they may resume their normal service. However, land and mobile stations which are in communication on frequencies other than those used for the transmission of the urgency signal and of the call which follows it may continue their normal work without interruption provided the urgency message is not addressed “to all stations”. (c) When the urgency signal has been sent before transmitting a message “to all stations” which calls for action by the stations receiving the message, the station responsible for its transmission must cancel it as soon as it knows that action is no longer necessary. This message of cancellation must likewise be addressed “to all stations”.
Title 47: Telecommunication
PART 80—STATIONS IN THE MARITIME SERVICES
Subpart G—Safety Watch Requirements and Procedures
Distress, Alarm, Urgency and Safety Procedures
§ 80.328 Urgency message.
