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PHOTO-TELEGRAPHY 



The overhead wires of the Paris -London tele- 

 phone line are 600 Ibs. copper wire in France and 

 400 Ibs. (per mile) in England. Their capacities 

 and resistances are as follows : 



The total capacity is thus 5*30 microfarads, and the 

 resistance 1,380 li. 



In the lines from Manchester to London there 

 are lines of different weights, from 300 Ibs. to 

 600 Ibs. per mile. The " standard cable " 

 employed as a unit consists of an air-space paper 

 cable with a loop resistance of 88 ohms per mile, 

 and an average mutual electrostatic capacity of 

 054 microfarad per mile between wire and wire of 

 one pair. The 300 Ibs. overhead wire may be 

 said to be about eleven times as efficient per mile 

 for telephone work as the standard cable, the 

 600 Ibs. line about sixteen times. The wire to 

 wire capacity of the overhead lines (300 Ibs.) 



