Page:United States Statutes at Large Volume 54 Part 2.djvu/207

 54 STAT.] MULTILATATER TELECOMMUNICATION-APR. 8, 1938 [53] §2. However, within limits compatible with economic require- ments, the choice of transmitting, receiving, and measuring apparatus must be guided by the most recent technical progress as shown, notably, in the Opinions of the C. C. I. R. ARTICLE 5 Classificationof Emissions [54] §1. Emissions shall be classified below according to the purpose eIsiation of for which they are used, assuming their modulation or their possible keying to be only in amplitude. [55] 1. Continuous waves: [56] Type AO. Waves the successive oscillations of which are identical under fixed conditions.' [57] Type Al. Telegraphy on pure continuous waves. A continuous wave which is keyed according to a telegraph code. [58] Type A2. Modulated telegraphy. A carrier wave modulated at one or more audible frequencies, the audible frequency or frequen- cies or their combination with the carrier wave being keyed according to a telegraph code. [59] Type A3. Telephony. Waves resulting from the modulation of a carrier wave by frequencies corresponding to the voice, to music, or to other sounds. [61] Type A4. Facsimile. Waves resulting from the modulation of a carrier wave by frequencies produced at the time of the scanning of a fixed image with a view to its reproduction in a permanent form. [62] Type A5. Television. Waves resulting from the modulation of a carrier wave by frequencies produced at the time of the scanning of fixed or moving objects.2 [63] (Note. - The band widths to which these emissions correspond are indicated in appendix 3.) [64] 2. Damped waves: [65] Type B. Waves composed of successive series of oscillations the amplitude of which, after attaining a maximum, decreases gradually, the wave trains being keyed according to a telegraph code. [66] §2. In the above classification, the presence of a carrier wave is assumed in all cases. However, such carrier wave may or may not be transmitted. [67] This classification does not contemplate exclusion of the use, by the administrations concerned, under specified conditions, of types of waves not included in the foregoing definitions. [68] §3. Waves shall be indicated first by their frequency in kilo- cycles per second (kc) or in megacycles per second (me). Following [60] 1 These waves are used only in special cases, such as standard frequency emissions. [70] 2 "Objects" is used here in the optical sense of the word. 1427

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