With the more extensive application of the cable developments 

 mentioned above to local circuits, it was natural that they should be 

 extended to the longer circuits used for toll business. In 1898 a 30- 

 pair 16-gauge cable insulated with paper was extended eight miles 

 from Boston toward Lynn, Massachusetts. Shortly after this a 30- 

 pair 14-gauge cable was placed between Boston and Wakefield, 

 Massachusetts, a distance of about 12 miles. It was found, however, 

 that with the increasing distance in cable, the loss in transmission 

 rapidly increased since cable circuits, because of the small size of the 

 wires and the large electrical capacitance, had inherently poorer 

 electrical characteristics for the transmission of telephone currents 

 than the larger open wires strung on poles. 



The Phantom Circuit 



The phantom circuit has grown out of a conception of Jacob in 

 1883 which is illustrated in principle in Fig. 4. He conceived that by 



aO 



L|, L2 = TELEPHONE LINES 



A = TELEPHONE INSTRUMENTS 

 R|, R2 = EQUAL RESISTANCES 



Oa 



Fig. 4 — Phantom circuit — conception of F. Jacob. 



bridging resistances across each end of two parallel telephone circuits, 

 a third circuit could be created as indicated by connecting telephones 

 at each end between the midpoints of these resistances. These three 

 telephone circuits could, therefore, use four wires without mutual 

 interference. While this scheme was not practicable, it led to a 

 proposal by Mr. Carty in 1886 to substitute balanced transformers 

 (called repeating coils) in place of the resistances as indicated in 

 Fig. 5. 



