54 STAT.] MULTILATERAL-TELECOMMUNICATION-APIR . 8 . 1938 [604] (2) In radiotelephony the urgent signal shall consist of three transmissions of the expression PAN (corresponding to the French pronunciation of the word "panne"); it shall be transmitted before the call. [605] (3) The urgent signal shall indicate that the calling station has a very urgent message to transmit concerning the safety of a ship, an aircraft, or another vehicle, or concerning the safety of some person on board or sighted from on board. [606] (4) In the aeronautical service, the urgent signal PAN shall be used in radiotelegraphy and in radiotelephony to indicate that the aircraft transmitting it is in trouble and is forced to land, but that it is not in need of immediate help. This signal should, so far as possi- ble, be followed by a message giving additional information. [607] (5) The urgent signal shall have priority over all other commu- nications, except distress communications, and all mobile or land stations hearing it must take care not to interfere with the transmis- sion of the message which follows the urgent signal. [608] (6) In case the urgent signal is used by a mobile station, this signal must, as a general rule, subject to the provisions of paragraph (4) above [No. 606], be addressed to a definite station. [609] §23. When the urgent signal is used the messages which this signal precedes must, as a general rule, be written in plain language, except in the case of medical messages exchanged between ships or between a ship and a coast station. [610] §24. (1) Mobile stations hearing the urgent signal must listen for at least three minutes. After this interval, and if no urgent message has been heard, they may resume their normal service. [611] (2) However, land and on-board stations which are in com- munication on waves other than those used for the transmission of the urgent signal and the call following it, may continue their normal work without interruption, unless the message is addressed "to all" (CQ). [612] §25. (1) The urgent signal may be transmitted only with the authorization of the master or of the person responsible for the ship, aircraft, or any other vehicle carrying the mobile station. [613] (2) In the case of a land station, the urgent signal may be transmitted only with the approval of the responsible authority. [614] (3) When the urgent signal has been used before the trans- mission of a message intended for all stations and including measures to be taken by stations which have received this message, the station responsible for the transmission must cancel it as soon as it knows that there is no longer necessity of acting upon it. This message of cancelation must likewise be addressed "to all" (CQ). K. SAFETY SIGNAL [615] §26. (1) In radiotelegraphy, the safety signal shall consist of ws " 1 L the group TTT, transmitted three times, with the letters of each group, as well as the consecutive groups, well separated. This signal 1547
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