TWELVE-CHANNEL OPEN-WIRE CARRIER SYSTEM 387 



B, which was obtained with the open-wire Hne replaced by its nominal 

 impedance, a 575-ohm resistance. The reflection between the open- 

 wire and toll entrance and repeater equipment is well under 5 per cent 

 over nearly all of the transmitted range. 



Conclusion 



The successful transmission of frequencies up to 140 kilocycles over 

 open-wire pairs as compared with earlier operation up to 30 kilocycles 

 has involved modification of the construction of the open-wire lines, 

 new transposition designs, new toll entrance arrangements, including 

 new types of cable, the improvement of impedance matches in various 

 parts of the circuits, closer repeater spacings and, where ice is en- 

 countered, provision for much greater gain margins with more flexible 

 regulation. 



The first system was placed in commercial service in September 

 1938. By the first part of this year about 60,000 channel miles were 

 in service over type J systems. 



References 



1. "A Twelve-Channel Carrier Telephone System for Open-Wire Lines," B. W. 



Kendall and H. A. Affel, A. I. E. E. Winter Convention, January 1939. 

 Bell System Technical Journal, January 1939. 



2. "Open-Wire Line Losses," L. T. Wilson, Bell Laboratories Record, Vol. XVI, 



November 1937, Pages 95-98. 



3. "High Frequency Attenuation on Open-Wire Lines," H. E. Curtis, Bell Labora- 



tories Record, Vol. XVII, December 1938, Pages 121-124. 



4. "Open-Wire Crosstalk," A. G. Chapman, Bell System Technical Journal, Vol. 13, 



January and April 1934, Pages 19-58, 195-238. 



5. "Transcontinental Telephone Lines," J. J. Pilliod, Electrical Engineering, Vol. 57, 



October 1938, Pages 418-419 and 423. Bell System Technical Journal, Janu- 

 ary 1939. 



6. "Some Applications of the Type J Carrier System," L. C. Starbird and J. D. 



Mathis, A. I. E. E., Southwestern District Convention, April 1939. This 

 issue of the Bell System Technical Journal. 



