158 BELL SYSTEM TECHNICAL JOURNAL 



of this insulation has made it possible to increase greatly the number 

 of telephone circuits in a given cable by using finer wires and thinner 

 insulations. 



A General Radiation Formula} S. A. Schelkunoff. In this paper 

 a general formula is derived for the power radiated in non-dissipative 

 media by a given distribution of electric and magnetic currents. 

 Magnetic currents are included not only for the sake of greater gen- 

 erality but also because in problems involving diffraction through 

 apertures and radiation from electric horns, the radiation intensity 

 can be made to depend upon fictitious electric- and magnetic-current 

 sheets covering the apertures or horn openings. 



Part I consists of an introductory discussion, summary of the 

 formulas, and examples illustrating the convenience of the general 

 formulas. Part II contains a mathematical derivation of tlie radiation 

 formulas. 



A Transmission System of Narrow Band-Width for Animated Line 

 Images} A. M. Skellett. A new method of transmission and repro- 

 duction of line images, e.g., drawings, is described which utilizes a 

 cathode-ray tube for reproduction, the spot of which is made to trace 

 out the lines of the image 20 or more times a second. The steps of 

 the complete process are: first, the transcription of the line image into 

 two tracks similar to sound-tracks on movdng picture film; second, 

 the production from these tracks of two varying potentials by means 

 of photoelectric pick-up devices; third, the transmission of these 

 potentials; and fourth, their application to the cathode-ray deflector 

 plates to effect reproduction. Satisfactory transmission of fairly com- 

 plex images, e.g., animated cartoons, could be effected within a total 

 band-width of 10,000 cycles. 



^Proc. I. R. £., October 1939. 



« Jour. S. M. P. E., December 1939. 



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