INTERNATIONAL RADIO CONVENTION. NOVEMBER 25,1927. wave of 500 kc/s (600 m.) must not be used for the transmission of long radiotelegrams in regions where the radio work is heavy. §2. During their hours of service, stations using for their work waves of Type A2, A3 or B, and open to the international service of public correspondence, must continue to listen on the wave of 500 kc/s (600 m.), except when they are exchanging traffic on other waves. §3. As a general rule, it is recommended that public correspondence traffic be transmitted on waves of Type AI, rather than on waves of Type A2 or B. §4. All stations in the mobile servicl;l are bound to exchange traffic with the minimum of radiated energy necessary to insure good com- munication. ARTICLE 29 Advice oj non-delivery §1. When {or any reason, a radiotell;lgram originating in a mobile station and destined to land can not be delivered to the addressee, a notice of nondelivery shall be addressed to the land station which received the telegram from 'the mobile station. This land station, after verification of the address, shall if possible, retransmit the notice to the mobile station, if need be through the intermediary of a land station of the same country or of a neighboring country, insofar as existing conditions or special agreements, if any, permit. §2. When a radiotelegram received at a mobile station cannot be delivered, that station shall so inform the office or mobile station of origin by a service advice. In the case of a radio telegram coming from land this service advice shall be sent, whenever possible, to the land station through which the radio telegram passed or, if necessary, to another land station of the same country or of a neighboring country, insofar as existing conditions or special agreements, if any, permit. ARTICLE 30 Period oj retention oj radiotehgrams at land stations §1. (1) When the mobile station to which a radio telegram is destined has not indicated its presence to the land station within the period of delay indicated by the sender1 or, in the absence of f. uch indi- cation, until the morning of the fifth oay following the dat J of filing, the land station shall so inform the office of origin which shall notify the sender. The latter may ask by telegraphic or postal paid service advice addressed to the land station that his telegram be held until the expiration of the fourteenth day, counting from the day of filing; in the absence of such an advice the radio telegram shall be cancelled after the seventh day. (2) The expiration of any of the periods mentioned above .shall, however, be Ignored if the land station is certain that the mobile station will soon come within its range. §2. On the other hand, the expiration of these periods shall not be awaited when the land station is certain that the mobile station has definitely gone out of range. If it presumes that no other land station of the administration or of the private enterprise to which it is subject is in communication with the mobile station, the land station shall cancel the radiotelegram insofar as concerns the routing between it and the mobile station, and shall so inform the office of origin which shall inform the sender. In the contrary case, the radiotehgram shall be directed to the land station which IS presumed to be in communication with the mobile station, provided, however, that no additional charge results therefrom. 54835°-29-PT 2 --76 2877 Advice of nondeliv- ery. Period of retention of radiote.legrams. at land stations.
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