IXTERXATIOXAL RADIO CONVENTION. NOVEMBER 25,1927. attention of other mobile stations in the vicinity, which are working on waves not included in the band mentioned above. 2871 §18. Rep!:'tition?f t~e 1istress call or m.essage, by mohile stati(;)Us :id~~h~tition of dL,trc. 'l S other than the one ill dIstress, shall be permItted oply on authorizatIOn from the master (or his relief) of said stations, taking care not to cause interference by useless repetition. §19. A station repeating a distress call or message shall add to the end thereof the word DE followed by its own call signal transmitted three times. §20. In a case where a station receives a disk'ess call or message bnt is not in a position to render assistance and haH reason to believe that there has been no acknowledgment of receipt t,f the distress message, it must repeat the message on full power on the distress wave and take all the necessary steps to advise the authoriti.es who are capable of useful intervention. A utomatic alarm signal §21. The composition of the automatic alarm signal must comply with the following conditions: (a) It must be possible to send this signal by hand or by !tn auto- matic apparatus, without difficulty and with a precision as to the measure of time, which must not be greater than that V~ a watch or a clock indicating seconds. (b) Its composition must be clear, distinct, and easily recognized hy a person ignorant of the Morse Code; and it must be adaptable to the easy and cheap manufacture of an automatic receiving apparatus which: 1. Shall respond to the alarm signal even when numerous stations are working as well as when there is atmospheric interference; 2. Shall not be started by powerful signals or by atmospherics when these are not accompanied by the alarm signal; 3. Shall possess a sensitiveness equal to that of a crystal receiver- detector connected with the same antenna; 4. Shall give warning when its operation ceases to be normal. (c) The said composition must be different from the signal used for adjustment and functioning of the variometer. (d) Before an automat!c alarm receiver shall be approved for use in ships under theJ'urisdiction of an Administration, the Administration must be satisfie by practical tests made under suitable conditions of interference, that the apparatus complies with the provisions of these Regulations. (e) The following alarm signal shall hereafter be reco~nized: A series of twelve dashes sent in one minute, the duratIOn of each dash being four seconds and the duration of the interval between two dashes, one second. (f) This special signal must ha'Ve for its sole purpose, the operation of the apparatus used to give the alarm. It must be used solely to announce that the distress signal is about to follow. (q) The adopt.ion of the type of alarm signal mentioned in (e) shall not prevent an Administration from authorizing the use of an automatic apparatus which would comply with the conditions fixed above and would be operated by the regulation distress signal, (.. .---... ). Automatic ~Jarm sig. nal. Urgent signal Urgent signal. §22. (1) The urgent signal shall consist of several repetitions of the group XXX, sent by distinctly separating the letters of each group and the successive groupsiJt shall be sent before a. call. This signal shall indicate that the calling st8,tion has Ii very urgent messaga to transmit ccncerning the safety of the ship, aircraft, or other vehicle
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