388 



THE BELL SYSTEM TECHNICAL JOURXAL, MARCH 1957 



terminal section layouts of all channels using the stackable frequency 

 arrangement or repeater-to-terminal section layouts for channels using 

 grouped normal or staggered frequency arrangements. 



7.3 Pad Selection 



The Plant Engineer is given general ground rules for determining the 

 values of input and output pads used in the terminals and repeaters. 

 Charts are provided for use in determining the input and output pads, 

 and they are so arranged that the engineer can take values directly from 

 the length-loss charts and enter them into the appropriate slots to cal- 

 culate the proper pad values. 



7.4 Crosstalk Limitations 



The Plant Engineer must be given information showing how many 

 carrier channels can be applied to each circuit of open wire, cable or B- 

 rural wire on a rural route. Crosstalk studies and tests have indicated 

 that the stackable frequency arrangement or the grouped frequency 

 arrangements used singly or in combination can be used on cable or B 

 rural wire with a full system complement of channels applied to each 

 pair. However, in the case of open wire, the frequency arrangement and 

 number of channels which can be applied is very dependent on the type 

 of transposition system used. The Rl design is the most commonh^ used 

 transposition design on rural lines of the Bell System, and Fig. 30 gives 



CHANNEL NOS, 



(a) stackable: 



(b) GROUPED: 



POLE PAIR 

 NONE 



N,2N,3N,4N IN,2N,3N,4N 



(a) stackable: 



(b) grouped: 



FREQUENCY ARRANGEMENT: 

 N - NORMAL GROUPED 

 S = STAGGERED GROUPED 



Fig. 30 — Number of PI carrier channels on an Rl transposed line. 



