518 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



of several transposition systems which have been widely used in the Bell 

 System. These include: 



Exposed Line — for voice frequency service. 



CI — for voice frequency and carrier service up to 30 kc. 



J5 — for voice frequency and carrier operation up to 143 kc. 



01 ■ — for voice frequency and compandored carrier operation up to 

 156 kc. 



RIC — suitable for exchange lines with a limited number of carrier 

 assignments. 



Altogether, the theory, explanatory material, formulas and compre- 

 hensive data included in the Monograph make it possible to estimate 

 open-wire crosstalk couplings and provide the necessary background for 

 the development of new transposition systems. 



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