47 CFR § 80.320 - Radiotelephone distress call and message transmission procedure.
(a) The radiotelephone distress procedure consists of:
(1) The radiotelephone alarm signal (whenever possible);
(2) The distress call;
(3) The distress message.
(b) The DSC distress procedure consists of:
(1) Transmission by a mobile unit in distress;
(3) Acknowledgement of distress calls;
(4) Distress relays.
(c) Radiotelephone distress transmissions must be made slowly and distinctly, each word being clearly pronounced to facilitate transcription.
(d) After the transmission by radiotelephony of its distress message, the mobile station may be requested to transmit suitable signals followed by its call sign or name, to permit direction-finding stations to determine its position. This request may be repeated at frequent intervals if necessary.
(e) The distress message, preceded by the distress call, must be repeated at intervals until an answer is received. This repetition must be preceded by the radiotelephone alarm signal whenever possible.
(f) When the mobile station in distress receives no answer to a distress message transmitted on the distress frequency, the message may be repeated on any other available frequency on which attention might be attracted.