54 STAT.] MULTILATERAL-TTELECOMMUNICATION-APR . 8 , 1938 [509] (d) Any other mobile service station transmitting public traffic on this or these waves and thereby causing interference with the said coast station must discontinue its work at the request of the latter. [510] (2) (a) When a mobile station wishes to establish communica- tion on one of these waves with another station of the mobile service, it must use the wave of 143 kc (2,100 m), unless otherwise indicated in the nomenclature. [511] (b) This wave, designated as a general calling-wave, must be used exclusively in the North Atlantic: [512] 1. For making individual calls and answering these calls; [5131 2. For transmitting signals preliminary to the transmission of traffic. [514] (3) A mobile station, after having established communica- tion with another station of the mobile service on the general calling- wave of 143 kc (2,100 m) must, so far as possible, transmit its traffic on some other wave of the authorized bands, provided it does not interfere with the work in progress of another station. [515] (4) As a general rule, any mobile station equipped for service on type-Al waves in the band 100 to 160 kc (3,000 to 1,875 m), which is not engaged in a communication on another wave, must, in order to permit the exchange of traffic with other stations of the mobile service, return each hour to the wave of 143 kc (2,100 m) for 5 minutes beginning at x:35 o'clock Greenwich mean time, during the specified hours, according to the category to which the station in question belongs. [516] (5) (a) Land stations must, to the extent possible, transmit the calls in the form of calling lists; in this case, the stations transmit their calling lists at definite hours published in the nomenclature, on the wave or waves which are allocated to them, in the bands of 100 to 160 kc (3,000 to 1,875 m), but not on the waves of 143 kc (2,100 m). [517] However, if the flow of its traffic is facilitated thereby, a land station may be authorized by the authority to which it is subject to begin its calling lists by the following brief preamble transmitted on 143 kc (2,100 m): CQ from. . . (land-station call signal). QSW . . . . followed by the indication of the priority wave- length of the station on which the calling list will be immediately afterward transmitted. Under no circumstances may this pre- amble be repeated. [518] (b) Land stations can, however, call individually mobile sta- tions at any time, outside the hours fixed for the trans- mission of calling lists, according to the circumstances or the work to be done. [519] (c) The wave of 143 kc (2,100 m) may be used for individual calls and will, preferably, be utilized to this end during the period indicated in §7 (4) [No. 5151. 1529
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