Sending 



Receiving 



Figure 45. — English lineman of the mid- 19th 

 century. His hat served both as protection 

 from the elements and as storage space for 

 extra tools. From Post Office Electrical Engineers 

 Journal, April 191 3, Vol. 6, opposite p. i. 



possibility of transmitting the sounds produced by the 

 human voice by means of an electric telephone. 

 Although it was in 1854 that Charles Borseul had 

 suggested a telephone for transmitting the human 

 voice by means of electricity, the term "telephone" 

 was not applied to an actual electrical instrument 

 until Philipp Reis devised his instrument in 1860.*" 

 In 1859, after becoming a teacher of science in a gym- 

 nasium near Frankfurt ain Main, Reis returned to the 

 studies on sound that he had begun previously. By 

 the following year he had completed his telephone, 

 and he exhibited several forms of it during the next 

 four years. (See figs. 54, 55.) Over 50 articles ap- 

 peared on the Reis telephone, and reproductions of it 

 produced by several instrument-makers appeared in 

 many physical laboratories of Europe and America. 



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lOT ip tp± ip tw 



Figure 46. — Schematic diagram of a pair of 

 multiplex distributors, by means of which one 

 transmitter-receiver after another is switched 

 to a common line. Reprinted (with permis- 

 sion) from A. Albert, Electrical Communication, 

 New York, 1940, p. 230. 



LINE 



Figure 47. — Stearns' duplex circuit. U.S. 

 patent 126847 (May 14, 1872). From W. H. 

 Preece and J. Sivewright, Telegraphy, New 

 York, 1876, p. 157. 



By 1869 the Reis instrument had been publicly dem- 

 onstrated in the United States.*' 



Reis' instrument was based on the principle that an 

 imperfect or intermittent contact in a circuit can 

 modulate (i.e., control) the current flowing through 

 that circuit. When a diaphragm in the transmitter of 

 the Reis telephone vibrated under the influence of 

 the human voice, a variation occurred in the pressure 

 of a metal point on a metal plate. This variation in 

 pressure modulated the current in the circuit. The 

 receiver of the Reis machine consisted of a knitting 

 needle placed inside an electromagnet which was 



*" Silvanus P. Thompson, Philipp Reis: Inventor of the Telephone, 

 London, 1883. 



" "The Telephone," Manufacturer and Builder, 1869, vol. 1, 

 pp. 129-130. 



312 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



