THE TIME FACTOR IN TELEPHONE TRANSMISSION 65 



he may hold the suppressor operative so continuously that it is difficult 

 for the other party to break in on the conversation if he so desires. If 

 one subscriber started to reply almost simultaneously with the termin- 

 ation of the other's speech, part of his reply might be blocked at the 

 echo suppressor along with the last of the echo. 



Further difficulties arise if two circuits, each containing an echo 

 suppressor of this kind, are switched together in tandem. In this case 

 it would be possible for the subscribers to completely block each other's 

 speech if they started talking simultaneously. 



In the case of radio circuits operated as noted above, difficulties are 

 introduced somewhat similar to that of two echo suppressors in tandem. 



The above will sufficiently suggest the types of difficulties which 

 arise from delay in connection with voice-operated devices. Certain 

 of the papers in the accompanying bibliography consider these prob- 

 lems in more detail. 



In preparing the accompanying bibliography, no attempt has been 

 made to make it complete. It is believed, however, to contain most of 

 the important publications on the subject. 



Bibliography 

 General 



"Telephone Transmission over Long Cable Circuits," A. B. Clark. Bell System 

 Technical Journal, vol. 2, no. 1, Jan. 1923, p. 67-94; A. I. E. E. Trans., vol. 42, Feb. 

 1923, p. 86-96; Electrical Communication, vol. 1, no. 3, Feb. 1923, p. 26-40. 



"Development and Application of Loading for Telephone Circuits," Thomas Shaw 

 and William Fondiller. A. I. E. E. Trans., vol. 45, Feb. 1926, p. 268-292; Bell 

 System Technical Journal, vol. 5, no. 2, April 1926, p. 221-281; Electrical Communica- 

 tion, vol. 4, no. 4, April 1926, p. 258-276, and vol. 5, no. 1, July 1926, p. 38-53. 



"Extending the Range of Loaded Lines by Echo Suppression and Phase Equaliza- 

 tion," K. Kiipfmiiller. Elektrische Nachrichten-Technik, vol. 3, no. 3, Mar. 1926, p. 

 82-88. 



"Transmission Characteristics of Long Distance Telephone Cable Connections," 

 K. Kiipfmiiller. Europdischer Ferns prechdienst, no. 5, July 1927, p. 19-33. 



"Telephone Communication System of the United States," Bancroft Gherardi and 

 F. B. Jewett. Bell System Technical Journal, vol. 9, no. 1, Jan. 1930, p. 1-100. 



" Recent Developments in Toll Telephone Service," W. H. Harrison. A. I. E. E. 

 Trans., vol. 49, no. 1, Jan. 1930, p. 166-176. 



"Some Recent Developments in Long Distance Cables in the United States of 

 America," A. B. Clark. Bell System Technical Journal, vol. 9, no. 3, July 1930, p. 

 487-492. 



"Transmission Characteristics of Open-Wire Telephone Lines," E. I. Green. 

 Bell System Technical Journal, vol. 9, no. 4, Oct. 1930, p. 730-759. 



"Range and Economy of the Toll Cable Lines of System II of the C. C. I.," K. 

 Hopfner and F. Liischen. Europdischer Ferns prechdienst, no. 21, Jan. 1931, p. 3-16. 



Delay Distortion 



"Theory of the Transient Oscillations of Electrical Networks and Transmission 

 Systems," J. R. Carson. A. I. E. E. Trans., vol. 38, pt. 1, 1919, p. 345-427. 



"Transient Phenomena in Wave Filters," K. Kiipfmiiller. Elektrische Nachrich- 

 ten-Technik, vol. 1, no. 5, Nov. 1924, p. 141-152. 



"Measurement of Phase Distortion," Harry Nyquist and Smart Brand. Bell 

 System Technical Journal, vol. 9, no. 3, July 1930, p. 522-549. 



