MEASUREMENT OF TELEGRAPH TRANSMISSION 189 



other terminal equipment. In the present state of the art, it is 

 difficult to make practical use of transfer admittances in predicting 

 the performance of a telegraph circuit. 



The significant point is that the satisfactory transmission of the 

 selected characters is an indication of the ability to transmit the de- 

 sired telegraph signals satisfactorily. Also, the measurement of the 

 distortion on the selected characters is particularly useful when it is 

 desired to equalize individual circuits of varying length and makeup 

 to secure a minimum of distortion. 



The testing procedures suggested by the considerations of the fore- 

 going have been incorporated into the testing instrumentalities dis- 

 cussed in the main paper. These methods have been used for several 

 years in the adjustment and maintenance of telegraph circuits and 

 found to be of considerable utility. 



Referenxes 



A. References Cited: 



1. "Measurement of Telegraph Transmission," Nyquist, Shanck and Corv, Trans. 



y4./.£.£., 1927, Vol. 46, p. 367. 



2. "Certain Topics in Telegraph Transmission Theory," H. Nyquist, Trans. 



^./.£.£., 1928, Vol. 47, p. 617. 



3. a. "Telephone Typewriters and Auxiliary Arrangements," R. D. Parker, Bell 



Telephone Quarterly, July, 1929, p. 181. 

 b. "Modern Practices in Private Wire Telegraph Service," R. E. Pierce, Trans. 

 A.I.E.E., Jan. 1931, Vol. 50, p. 45. 



4. "Fundamentals of Teletypewriters Used in the Bell System," E. F. Watson, 



Bell System Technical Journal, Oct., 1938, p. 620. 



5. "A Transmission Svstem for Teletypewriter Exchange Service," Pierce and 



Bemis, Bell Sys. Tech. Journal, Oct., 1936, p. 529; Elec. Engg., Sept., 1936, 

 p. 961. 



6. " Metallic Polar-duplex Telegraph System for Cables," Bell, Shanck and Branson, 



Trans. A.I.E.E., 1925, Vol. 44, p. 316. 



7. a. "Der Spielraum des Siemens-Springschreibers," M. J. deVries, Telegraphen 



und Fernsprech Technik, Jan., 1934, p. 7. 

 b. "Der Spielraum des Springschrieber," M. J. deVries, T. F. T., Sept., 1937, 

 p. 213. 



B. Additional References : 



8. "Ein Neues Mess- und Uberwachungsgerat fiir Springschreiberverbindungen," 



W. Schallerer, T. F. T., Feb., 1935, p. 40. 



9. "Versuche uber eine giinstige Verteilung der Tragerwellen in der Wechsel- 



stromtelegraphie," H. Stahl, T. F. T., Nov., 1930, p. 340. 



10. " Verzerrungsmesser fiir Telegraphie," A. Jipp and O. Romer, T. F. T., May, 



1932, p. 121. 



11. "Telegraph Transmission Testing Machine," F. B. Bramhall, Trans. A.I.E.E., 



June, 1931, p. 404. 



12. "A Telegraph Distortion Measuring Set," V. J. Terry and C. H. W. Brookes- 



Smith, Elec. Comm., July, 1933, p. 15. 



13. "The Measurement of Telegraph Distortion," V. J. Terry, Elec. Comm., April 



1933, p. 197. 



14. "Determining the Transmission Efficiency of Telegraph Circuits," E. H. Jolley, 



P.O.E.E. Jl., April, 1933, p. 1. 



