CARRIER IN CABLE 



253 



Note: In a practical installation the one-way paths wouUl be shielded from each 

 other either by placing them in separate cables or by placing them in a 

 single cable divided into two electrical compartments by means of a 

 specially arranged shield. In the setup at Morristown the circuit was 

 necessarily arranged somewhat differently since only one cable was 

 available. Transmission over all loops in this cable went in the same 

 direction, half the loops then being connected in tandem to simulate one 

 direction' of transmission through a long circuit and the other half in 

 tandem to simulate the other direction of transmission. 



It will be noted that in this cable system the practical equivalent 

 of two electrical paths was provided, one for transmission in each 

 direction, the same range of frequencies being used in each direction. 

 This differed from common open-wire practice in which the frequency 

 range is split in two and used, one half for transmission in one direction, 

 the other half for transmission in the other. Fig. 2 compares the 



OPEN 

 WIRE 



TYPE 

 D 



TYPE 

 C-N 



TYPE 

 C-S 



TYPE 

 C-T 



MORRISTOWN 

 CABLE 



DOTTED ARROWS SHOW LOCATION 

 OF CARRIER FOR EACH BAND 



; EAST TO WEST | WEST TO EAST 



TNORTH TO SOUTH j SOUTH TO NORTH 



3 2 I 



'♦' '♦ 



15 20 25 



FREQUENCY IN KILOCYCLES 



Fig. 2 — Frequency allocations of carrier telephone systems. 



frequency allocation of the Morristown cable carrier system with 

 existing open-wire systems in this country. Except for this matter of 

 difference in frequency allocation, the fundamental carrier methods 

 used in this cable system did not differ in principle from those already 

 used on open wires. As will be noted in Fig. 2 all of these carrier 

 telephone systems use the single sideband method of transmission with 

 the carrier suppressed. 



Fig. 3 is a schematic diagram of the terminal apparatus used in 

 deriving one of the telephone circuits. Its general resemblance to 



