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BELL SYSTEM TECHNICAL JOURNAL 



stray fields from the numerous electric railway systems in the neighbor- 

 hood of New York. By means of an amplifier and a recording string 

 oscillograph records were obtained of the interference on the Western 

 Union Telegraph Company's non-loaded cables terminating at New 

 York. In taking these records a number of terminal networks were 

 employed, with various attenuation characteristics, in order to obtain 

 an idea of the distribution of interference with respect to frequency. 

 Another series of tests was made, on board the Western Union cable- 

 ship "Clowry," during wiiich a cable was raised from deep water, cut, 

 and interference studies made on the two parts of the cable. A study 

 of these results according to the method that has just been described 

 indicated that unless some means were employed for reducing the 

 terminal interference, a great sacrifice of signal speed would have to be 

 made, at least on westbound traffic. The remedy that was adopted 

 is a special type of earth connection 100 miles at sea, to which the 

 ground terminal of the receiving apparatus is connected. The theory 

 of this arrangement will now be developed. 



For the purpose of diminishing extraneous interference there is pro- 

 vided on most submarine cables an earthing arrangement, which, as 

 shown diagrammatically in Fig. 5, consists of a core C2 of the same 

 general type as that used in the main cable Ci, and which may be 



FIG 5 



"Xg 



armored either with the main cable or in an independent sheath. This 

 core usually extends for a distance of a few miles from the shore, to a 

 point G, where the conductor of the core is grounded on the armor of 

 the main cable. The receiving apparatus associated with the main 

 cable conductor is then connected to earth through the sea earth con- 

 ductor and the earth connection at its sea terminal. It is evident that 

 if the main core and the sea earth core are close together they will l)oth 

 be exposed to the disturbances encountered between the terminal and 

 the point where the sea earth conductor is grounded. If the two cores 



