47 CFR § 80.319 - Radiotelegraph distress call and message transmission procedure.
(a) The radiotelegraph distress procedure consists of the following six steps: however, when time is vital, the first and second steps may be omitted. These two steps of the distress procedure may also be omitted in circumstances when transmission of the alarm signal is considered unnecessary:
(1) The radiotelegraph alarm signal;
(2) The distress call and an interval of two minutes;
(3) The distress call;
(4) The distress message;
(5) Two dashes of ten to fifteen seconds each;
(6) The call sign of the mobile station in distress.
(b) The radiotelegraph distress transmissions must be sent by means of the international Morse code at a speed not exceeding 16 words per minute nor less than 8 words per minute.
(c) The distress message, preceded by the distress call, must be repeated at intervals until an answer is received. The radiotelegraph alarm signal may also be repeated, if necessary.
(d) The transmissions under paragraphs (a) (5) and (6) of this section, which are to permit direction finding stations to determine the position of the station in distress, may be repeated at frequent intervals if necessary.
(e) 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.