AN IMPROVED THREE-CHANNEL CARRIER TELEPHONE SYSTEM 75 



few systems are involved, the engineering solution may be quite 

 different from that on a long line on which it is desired to operate 

 many systems. Several different plans for transposing wires have 

 been developed which can be applied with various pole line configura- 

 tions so as to meet the necessary requirements in any practical case. 

 The more recently constructed carrier lines have, in general, employed 

 a spacing of 8 inches between the wires of a pair, with from 16 to 

 26 inches between horizontally adjacent pairs. Besides contributing 

 to the crosstalk reduction, the closer spacing is also less susceptible 

 to interference from outside sources, which is an advantage from a 

 noise standpoint. 



Attenuation characteristics ^ for typical eight-inch spaced pairs 

 using the CS type of insulator are given in Fig. 18. Normal or dry 

 weather characteristics are shown, together with the losses that are 

 assumed for ordinary wet weather. Temperature changes also result 

 in sizable transmission changes. It is also important to note that the 

 losses when the wires are coated with sleet or frost may go far beyond 

 those indicated for the wet weather condition. 



Conclusion 

 The widespread use that has been made of the Type C system up 

 to this time is pictured in Fig. 19, which shows the routes in the Bell 

 System over which systems are now operating. The new design with 

 its lower costs, improved performance and greater flexibility should 

 find increased application not only on these routes but on shorter lines 

 on which the system has hitherto not been economical. 



References 



1. "Carrier Systems on Long Distance Telephone Lines," H. A. Affel, C. S. Demarest 



and C. W. Green, Bell Sys. Tech. Jour., volume 7, July 1928, pages 564-629; 

 A.I.E.E. Transactions, volume 47, October 1928, pages 1360-1386. 



2. "Cable Carrier Telephone Terminals," R. W. Chesnut, L. M. Ilgenfritz and 



A. Kenner, Bell Sys. Tech. Jour., volume 17, Jan. 1938, pages 106-124; 

 Electrical Engineering {A.I.E.E. Transactiotis) , volume 57, May 1938, pages 

 237-244. 



3. " Carrier Telephone System for Short Toll Circuits," H. S. Black, M. L. Almquist 



and L. M. Ilgenfritz, Electrical Engineering {A.I.E.E. Transactions), volume 

 48, January 1929, pages 117-140. 



4. "A New Single-Channel Carrier Telephone System," H. J. Fisher, M. L. Almquist 



and R. H. Mills, Bell Sys. Tech. Jour., volume 17, January 1938, pages 162- 

 183; Electrical Engineering {A.I.E.E. Transactions), volume 57, January 1938, 

 pages 25-33. 



5. "Copper-Oxide Modulators," R. S. Caruthers, Presented at Winter Convention 



of A.I.E.E., Januarv 1939. 



6. "Stabilized Feedback Amplifiers," H. S. Black, Bell Sys. Tech. Jour., volume 13, 



January 1934, pages 1-18; Electrical Engineering, volume 53, January 1934, 

 pages 114-120. 



7. "Open-Wire Crosstalk," A. G. Chapman, Bell Sys. Tech. Jour., volume 13, Janu- 



ary 1934, pages 19-58; April 1934, pages 195-238. 



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



Bell Sys. Tech. Jour., volume 9, October 1930, pages 730-759; Electrical 

 Engineering {A.I.E.E. Transactions), volume 49, October 1930, pages 1524- 

 1535. 



