356 



BELL SYSTEM TECHNICAL JOURNAL 



tioned twin coaxial cable and the measured interaction crosstalk 

 The curves in Fig. 3 are for equal lengths either of 3000 ft. or 12,000 ft. 

 In the case of the measured values, the junction point of the two sec- 

 tions was not the same for these two lengths. Although the agreement 

 between calculated and measured values is only fair, the spread in the 

 experimental results for these two cases, which for uniform cable would 

 be slight, is about the same as the spread between calculated and 

 measured values. 



105 



,V, 115 



_l 



< 120 



o 

 a. 

 o 



125 



50 



80 90 100 150 200 



FREQUENCY IN KILOCYCLES PER SECOND 



300 



Fig. 3 — Far-end far-end interaction crosstalk between two equal lengths. 



The two-tertiary formulas have so far been applied only to one type 

 of cable with four coaxial lines and a layer of paper-insulated pairs. 

 The longest length of this type of cable on which crosstalk measure- 

 ments have been made is 1900 ft. The various types of interaction 

 crosstalk with one tertiary short-circuited, as computed from the 

 formulas given above, agree roughly with the measured interaction 

 crosstalk under this same condition. However, the restriction that 

 the tertiary circuits involved are electrically long, as postulated in 

 deriving the interaction crosstalk formulas for this case, is not satisfied, 



