2854 INTERNATIONAL RADIO CONVENTION. NOVEMBER 25,1927. of one of the interested countries has given notice of its opposition to this exchange. §2. When this exchange is permitted the communications must, unless the interested countries have entered into other agreements among themselves, be carried on in plain language and be limited to messages bearing upon the experiments and to remarks of a private nature for which, by reason of their unimportance, recourse to the public telegraph service might not be warranted. §3. In a private experimental station authorized to carry on trans- mission any person operating the apparatus, either on his own account or for another, must have proved his ability to transmit text in International Morse Code signals and to read by ear texts thus transmitted. He can be replaced only by authorized persons possessing the same qualifications. §4. .A:dministrations shall take such measures as they deem neces- sary to verify the qualifications, from a technical point of view, of all persons handling the apparatus. ARTICLE 7 Operators' certlll· Operators' certtificates cates. Requirements. §1. (1) The service of every mobile radiotelegraph of radiotele- phone station must be carried on by a radiotelegraph operator holding a certificate issued by the government to which the station is subject. However, in mobile stations equipped with a low-power radio- telephone installation (of a power not exceeding 300 watts input) capable of being used only for telephony, the service may be carried on by an operator holding only a radiotelephone operator's certificate. (2) In case of the absolute unavailability of the operator in the course of a crossing, flight, or voyage, the master or the person respon- sible for the mobile may authorize, but only temporarily, an operator holding a certificate issued by another contracting Government to carry on the radio service. When it becomes necessary to employ as temporary operator a person not holding the prescribed certificate, his service must be limited to emergency cases. In any case, the operator or the above-mentioned person must be replaced so soon as practicable by an operator holding the certificate prescribed in the preceding paragraph. §2. There are two classes of certificates and of special certificates for radiotelegraph operators and one class of certificates for radio- telephone operators. Certificates (or radio- Oerttificates jor radiotelegraph operators telegraph operators. Qualifications. First class. §3. (1) Each Government shall be free to fix the number of exam- inations deemed necessary to obtain a first-class certificate. (2) The first-class certificate must state that the operator possesses the requisite qualification for obtaining the radiotelephone operator's . ce rtificate. Each government shall be free to require or not the same qualifications in the case of the second-class certificate. (3) The minimum qualifications for obtaining these certificates shall be the following: A. First class The first-class cer'tificate shall state the professional and technical qualifications of the operator with regard to: (a) Knowledge of the general principles of electricity, of the theory of radiotelegraphy and radiotelephony, and of the practical operation of all apparatus used in the mobile service;
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