SOME APPLICATIONS OF TYPE "J" CARRIER SYSTEM 343 



and adverse weather conditions, location and availability of existing 

 telephone buildings, and availability of commercial power for new 

 buildings. Line attenuation is increased greatly by deposits of ice on 

 the wire during sleet conditions. Although data are available regarding 

 the frequency of large deposits of ice, there is very little information as 

 to the amounts or frequency of occurrence of small deposits. Under 

 normal wet weather conditions the maximum attenuation of six-inch 

 spaced 128-mil facilities at 140 kilocycles is 0.35 db per mile. 



On the Dallas-San Antonio line the facilities available consisted of 

 286 miles of six-inch spaced 128-mil copper wire and 42,000 feet of 

 16-gauge non-loaded paper insulated cable. Using repeaters having a 

 maximum amplification of 45 db in each direction of transmission, the 

 provision of two intermediate repeaters would provide sufficient gain 

 to take care of the wet weather conditions with no extra margin ; three 

 repeaters would provide 45 db margin and four would provide 90 db 

 margin for the overall system. Considering the location of this line 

 and the small probability of obtaining large deposits of ice in ac- 

 cordance with past experience, it was decided to select tentatively three 

 intermediate repeater stations which would provide sufficient gain to 

 take care of attenuation up to about 0.5 db per mile as compared to the 

 wet weather value of 0.35 db per mile. 



For type C operation over this line, only one type C carrier repeater 

 point is required, and it is at Austin. Considering the availability of 

 power equipment and operating personnel and the possibility of future 

 J carrier terminals being located at Austin, it is desirable that this be 

 one of the repeater points on the J system. A division of the attenu- 

 ation of the facilities north of Austin indicated that the other stations 

 should be in the vicinity of Temple and Milford. 



At these repeater stations amplification is needed only on the type J 

 system and the other circuits on the line pass through these stations 

 without amplification. Under these conditions energy may be 

 transferred from the output of one type J repeater to the input of the 

 same repeater or to the input of a repeater on another J system via 

 crosstalk paths involving the wires which are not used for type J 

 systems. The effect of this transfer of energy is accentuated by the 

 fact that there is a large difference in transmission level between the 

 output of one type J repeater and the input of the same or another 

 repeater. In order to minimize these effects it is necessary that all 

 wires on the line be given special treatment, including a gap in the toll 

 line, longitudinal choke coils in all wires at terminal poles and crosstalk 

 suppression filters in the non-J pairs in the repeater station itself. In 

 selecting locations for repeater stations, consideration must also be 



