Sec. 80.328  Urgency message.

    (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''.