224 Prof. Perry on Long-Distance Telephony. 



The letters with dashes indicate that p' or 2irf must be taken 

 instead of p. It is easy to see that X and Y become infinite 



., I h 

 if - = -• 



r s 



I do not know what values of m and n would produce 

 confusion of sound in the telephone. But as an exercise we 

 have taken m=4 and n=6. We have also taken p = 6000, 

 2?'= 600. 



For the first French Atlantic Cable the capacity and 

 resistance were 0*43 microfarad and 2*93 ohms per nautical 

 mile, so that 



& = 2'3215x 10 -12 farads per centim. 



r = 1*582 x 10~ 5 ohms per centim. 



Mr. Beeston has calculated the distances X and Y, the 

 lesser of which may be taken as the limiting distance for good 

 telephony for various values of I and s. 



Table I. — Limiting distances X in millions of centimetres 

 for various amounts of leakage and self-induction. (One 

 million centimetres are equivalent to about six miles.) 



Values of 

 SX10 10 - 



Values of ^Xl0 10 . 







2-6373 



26-373 



79-118 



131-863 



184-61 



263-73 







0-983 



1-054 



1-963 



5-169 



10-178 



17*500 



33-839 



•01 







1-961 











•10 



... 





1-969 











1 







1-999 











5 



1-049 



1-130 



2-187 



6-339 



13-944 



41-532 



75-59 



10 



1-130 



1-224 



2-356 



8-462 



21-98 



59-03 



328-2 



20 



1-319 



1-444 



3-357 



18-009 



128-17 



very- 

 large 

 18-94 



131-65 



40 



1-754 



1-965 



6-250 



390-11 



67-95 



8-75 



70 



2-527 



2-935 



17-671 



39-73 



7-727 



4-161 



2-573 



100 



3-447 



4-134 



72-03 



10-00 



0-650 



2-111 



1-617 



150 



5-314 















200 



7-536 















250 



10-090 















