Page:United States Statutes at Large Volume 45 Part 2.djvu/1202

 2878 Meteorological serv- Ices. Time Signals. Notices to navigators. Radlocompa88 stations service. INTERNATIONAL RADIO CONVENTION. NOVEMBER 25,1927. §3. When a radiotelegram. cannot be sent to a mobile station due tc the amvfll of the latter in a port near the land station, the latter station may, if necessary, forward the radiotelegram to the mobile station by other means of communication. ARTICLE 31 Special services A. Meteorological services. Time signals. Notices to navigators §1. Synoptic meteorological messages regarding forecasting and general surveys and time signals must, in principle, be transmitted in conformity with a fixed schedule. Radiotelegrams of this class intended for mobile stations must be sent, so far as practicable, at times which will make their reception possible to those stations having only one opera~r (see Appendix 5); speed of tranmission must be so chosen that reading of the signals will be possible to an operator possessing only a second-class certificate. §2. During transmissions "to all stations" of time signals and of meteorological messages intended for stations of the mobile service, all stations in that service the transmissions of which might interfere with the reception of the signals and messages in question, must keep silent in order to permit all stations so desiring to receive these sig- nals and messages. §3. Meteorological warning messages and notices concerning the safety of navigation of an urgent nature for the mobile services shall be transmitted immediately and must be repeated at the end of the first silent period which occurs (see Articla 17, section 2). These messages and advices must be sent on the frequencies assigned to the mobile service to which they are destined; thell' transmission must be preceded by the safety signal TTT. §4. In addition to the regular information services contemplated in the preceding paragraphs, the Administrations shall take the necessary measures so that certain stations shall be charged with sending, upon request, meteorological messages to stations in the mobile serrice. §5. In the interest of brevity and of proper usage by mobile sta.tions, the meteorological observations sent by stations in the mobile service must, in principle, be written in an international meteorological code. B. Service of radiocompass stations §6. The Administrations to the jurisdl.ctjon of which radiocompass stations are su~ject accept no responsibility for the consequences of an inexact beanng. §7. These Administrations shall report, for insertion in the nomen- clature of radiotelegraph stations, the eharacteristics of each radio- comJ?8.SS station by indicating, for each one, the sectors in which bearmgs are normally exact. All changes concerning this informa- tion must be published without delay; if the change is of a permanent nature it must be communicated to the International Bureau. §8. (1) In normal service, coast radiocompass stations must be capable of taking and furnishing bearings to ship stations either on the frequency of 500 kc/s (600 m.) only, or on the frequency of 375 kc/s (800 m.) only, or interchangeably on one or the other of these two frequencies. (2) An aircraft station desiring its bearings must, in order to request them, call on the 333 kc/s (900 m.) wave or on a wave assigned to the aerial route in which it is flying. In cases where an aircraft station, while in the vicinity of coast stations, calls them in order to obtain a bearing, it must use the frequency of these coast stations.

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