684 



Prof. J. Perry on Telephone Circuits. 



Practical men will now see their way to easy calculation 

 of the effect of placing any kind of contrivance in a circuit, 

 and I need not give any more examples. It is to be remem- 

 bered that condensers suitable for telephonic purposes are 

 very cheap, a few shillings per microfarad, whereas induct- 

 ances are expensive. Also, it has to be remembered that 

 when the whole telephonic current passes through an induction 

 coil, its resistance becomes of very serious importance, for 

 the cost of coils of similar construction is proportional to the 

 3/2 power of L/R if L is the inductance and R the resistance 

 of the coil. 



With the permission of the Society I here append a table 

 of the values of sink r (45°) and cosh r (45°) to supplement 

 that published by Kennelly. His r is 0, O'l, 0'2, &c, and we 

 need closer entries for the above kind of calculation. My 

 table has been computed by Mr. J. J. Brookes. 





r. 



sinh i 



• (45°). 



cosh 1 



• (45°). 



•01 



•oioooo 



(45° -00) 



100000 



(00°) 



•02 



•020000 



(45° -00) 



100000 



(-00°) 



•03 



•030000 



(45° -00) 



1-00000 



(•02 c ) 



•04 



•040000 



(45°-01) 



rooooo 



(-04°) 



•05 



•050000 



(45° -02) 



1-00000 



(-07°) 



•06 



•060000 



(45°-04) 



1-00000 



(-10°) 



•07 



•070000 



(45°-05) 



1-00000 



(-14°) 



•08 



•080000 



(45° 06) 



1000UO 



(-18°) 



•09 



•090000 



(45° -08) 



1-00000 



(-22°) 



•10 



•10000 



(45°-09) 



1-00001 



(-29°) 



•15 



•15000 



(45°-2l) 



1-00004 



(-64°) 



•20 



•20000 



(45°-o8) 



100013 



(1°-15) 



•25 



•25000 



(45°-60) 



100032 



(l°-79) 



•30 



•30001 



(45°-86) 



1-00067 



(2°5H) . 



•35 



•35003 



(46°-17) 



100125 



(3° -50) 



•40 



•40005 



(46°-53) 



1 0021 



(4° -58) 



•45 



•45010 



(46° 93) 



1 0034 



(5°-79) 



•50 



•50016 



(47°-39) 



1-0052 



(7°44) 



•55 



•55027 



(47° -89) 



1-0076 



(8°-63) 



•60 



•60042 



(48°-44) 



1-0107 



(10°-25) 



•65 



•65063 



(49°-03) 



10148 



(12°01) 



•70 



•70093 



(49°-68) 



10200 



(13°-S9) 



•75 



•75131 



(50°-37) 



1-0263 



(15°-89) 



•80 



•80181 



(51°-10) 



1-0336 



(18°-01) 



•85 



•85245 



(51°-89) 



10426 



(20°-24) 



•DO 



•90327 



(52°-72) 



1 -0533 



(22°-57) 



•95 



•95428 



(53° -60) 



10659 



(24° 99) 



1-00 



100553 



(54° -53) 



1-0803 



(27°'49) 



