MULTIPLEX TELEPHONY AND TELEGEAPHY BY MEANS 

 OF ELECTRIC WAVES GUIDED BY WIRES. 1 



[With 1 plate.] 



Dr. George O. Squier, 

 Major Signal Corps, United States Army. 



I.— INTRODUCTION. 



Electrical transmission of intelligence, so vital to the progress of 

 civilization, has taken a development at present into telephony and 

 telegraphy over metallic wires; and telegraphy, and, to a limited 

 extent, telephony, through the medium of the ether by means of 

 electric waves. 



During the past 12 years the achievements of wireless teleg- 

 raphy have been truly marvelous. From an engineering viewpoint, 

 the wonder of it 'all is, that, with the transmitting energy being 

 radiated out over the surface of the earth in all directions, enough 

 of this energy is delivered at a single point on the circumference of a 

 circle, of which the transmitting antenna is approximately the cen- 

 ter, to operate successfully suitable receiving devices by which the 

 electromagnetic waves are translated into intelligence. 



The "plant efficiency" for electrical energy in the best types of 

 wireless stations yet produced is so low that there can be no com- 

 parison between it and the least efficient transmission of energy by 

 conducting wires. 



The limits of audibility, being physiological functions, are well 

 known to vary considerably, but they may be taken to be in the 

 neighborhood of 16 complete cycles per second as the lower limit 

 and 15,000 to 20,000 cycles per second as the upper limit. If, there- 

 fore, there are impressed upon a wire circuit for transmitting intelli- 

 gence harmonic electromotive forces of frequencies between and 16 

 cycles per second, or, again, above 15,000 to 20,000 cycles per second, 

 it would seem certain that whatever effects such electric-wave fre- 

 quencies produced upon metallic lines, the present apparatus em- 

 ployed in operating them could not translate these effects into audible 

 signals. 



1 A paper presented at the twenty-eighth annual convention of the American Institute of Electrical 

 Engineers, Chicago, 111., June 26-30, 1911. Copyright, 1911, by A. I. E. E. Reprinted by permission 

 from Proceedings of the Institute for May, 1911, pp. 857-905. 



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