63 STAT.] MULTILATERAL-TELECOMMUNICATIONS-OCT. 2, 1947 (Chapter XIII, art. 28 RR) (592-598) working frequencies in addition to one frequency in the calling band; 592 b) changes of frequency in transmitting apparatus must be effected within 5 (five) seconds if the frequencies are in the same band and within 15 (fifteen) seconds if the frequencies are in differ- ent bands; 593 c) receiving apparatus must be capable of a per- formance equal to that of the transmitting ap- paratus in the matter of frequency changing and must be designed in such a manner so as to ensure a satisfactory performance; 594 d) the provisions of 592 and 593 above shall become effective on the same dates as the tolerance re- quirements of column 3 of appendix 3 as applied to ship and aircraft stations. 595 § 13. (1) Stations in ships compulsorily equipped with radio- telegraph apparatus must be able to receive, in addition to 500 kc/s, all the frequencies necessary for their service. 596 (2) Such stations must be able to receive easily and effi- ciently on the same frequencies class Al and A2 emissions. 597 (3) Ship radiotelegraph stations shall be equipped as soon as possible with devices permitting change-over from transmission to reception and vice-versa without manual switching. Section III. Aircraft Stations 598 § 14. (1) Any aircraft station following a maritime course and required by national or international regulations to com- municate, for safety purposes, with stations of the maritime mobile service, must be capable of transmitting and receiv- ing on the frequency 500 kc/s, preferably class A2 emission. 1823
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