Page:United States Statutes at Large Volume 54 Part 2.djvu/1313

 2534 INTERNATIONAL AGREEMENTS OTHER THAN TREATIES [54 STAT. 10. The usual diathermy machine is essentially a radio transmitter of the self-excited oscillating type and generally uses self-rectifying plate power supply. Due to the inherent instability of the oscillator circuits, the wide variation in voltage during a plate supply cycle, and the different uses to which the output circuit is subject, the operat- ing frequency varies during normal operation over very wide bands, possibly one or two megacycles, when operating on a frequency of approximately 15 megacycles. 11. All diathermy machines designed for the same service could operate on the same frequency without impairing their usefulness, since their operation is not affected by radiation from other machines. To operate on a fixed frequency would require additional apparatus and cost in that automatic frequency control would be required- to maintain the operating frequency within at least %opercent to be effective. At 15 megacycles this would require a band width of 15 kilocycles, or virtually one communication channel. 12. From the best information available diathermy operation should be restricted until the art advances to the point where apparatus may be designed to completely suppress interfering radiations, to three fre- quencies, namely, approximately 12 megacycles, 25 megacycles, and 50 megacycles. 13. Such apparatus as carrier call systems and certain types of induction furnaces and similar apparatus using medium or low fre- quencies should be required to restrict the generation of harmonics and make the necessary test to determine that radiation of signal does not result beyond a prescribed level. 14. Each subscribing country should make the necessary regula- tions to require the complete shielding or operation on designated frequencies of all non-radio apparatus which generate radio frequency electric energy as an essential to its operation but does not engage in radio communication. 15. There is annexed hereto a report on "Radio Interference from Electro Therapeutic Apparatus" presented by Canada which is to be considered part of the material adopted on this subject. NOTE: See "Radio Interference from Electro Therapeutic Apparatus" report presented by Canada, contained in document C.I.R./Doc. 43. In witness whereof, the respective Delegates have signed various copies of this instrument in Spanish, English, Portuguese and French, to be deposited in the archives of the Government of Cuba, which shall forward an authenticated copy thereof in each language to the other contracting Governments. Done in the city of Havana, Republic of Cuba, on the 13th day of December, 1937. signatures. ARGENTINE REPUBLIC: BRAZIL: JosE ROBERTO DE MACEDO-SOARES.

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