TELEPHONE EQUIPMENT FOR LONG CABLE CIRCUITS 125 



such as those associated with the composite sets and phantom sets, 

 thus simplifying the equipment for terminating the toll lines. Fig. 11 

 shows the typical open-wire arrangement for a terminating phantom 

 group circuit in which the maximum number of jacks is furnished. 

 This requires a total of 46 jacks. Fig. 12 shows the arrangement of a 

 terminating phantom group circuit as planned for a cable installation. 

 In this case a total of but 30 jacks is required. 



Another important development expected in the test board ar- 

 rangements to suit them to cable use is the grouping together of the 

 jacks serving similar functions. Considerable improvement in 



Fig. 12 — Typical Phantom Group Circuit for Cable Installations 



operation is thought to be possible with the jacks having different 

 functions located at different test board positions. In this way all 

 of the line conductor jacks, for example, may be assembled together 

 in consecutive order, and since several hundred of these may be in- 

 volved in a single installation, this should greatly facilitate the identi- 

 fication of the desired circuits by the attendant in the process of 

 patching and testing. This grouping of the jacks will also effect a 

 saving in testing equipment, since it will eliminate the need of the line 

 testing apparatus, such as the Wheatstone bridge, at positions where 

 the line conductors will not appear. 



