1914] on Improvements in Long-Distance Telephony 103 



Then a word or two must be said on another type of loading 

 which is called continuous loading. It is really a reversion to 

 Heaviside's original idea of adding inductance all along the cable. 

 If a stranded copper cable has a soft iron wire uniformly and closely 

 wound on it as a spiral, this iron increases the inductance of the wire 

 to a certain extent. It also somewhat increases the capacity and the 

 resistance of the cable, but nevertheless reduces the attenuation 

 constant. This type of loaded cable is sometimes called a Krarup 

 cable after the Danish Engineer who first employed it for practical 

 telephony. A good deal of discussion has taken place amongst 

 telephonists as to the relative advantages of coil or Pupin loading 

 and uniform or Krarup loadmg 



To help to settle some of these questions the French Government 

 laid across the English Channel in 1912 a continuously loaded or 

 Krarup cable, which was manufactured by the Telegraph Construc- 

 tion and Maintenance Company. 



This Anglo-French uniformly loaded cable has an effective resist- 

 ance of <S 54 ohms at 1000 frequency, a wire-to-wire capacity of 

 0*176 mfds., an inductance of 0*0135 henry, and an attenuation 

 constant 0'0185. The total attenuation is 0*39, the value of S/C 

 is 109, and the conductor weighs 300 lb. to the nautical mile. 



The copper core in this uniformly loaded cable has twice the 

 weight per mile, viz. 300 lb., of either of the G.P.O. coil-loaded 

 cables, and it has an attenuation constant slightly greater than those 

 of the latter. 



The performance of these four cables and the resulting experience 

 as to the cost of maintenance and repairs, will furnish most valuable 

 data to guide the design for future loaded deep-sea telephone cables. 

 Important information has also been gained to enable telephonic 

 engineers to predict the performance of various types of coil-loaded 

 or continuously-loaded cables. 



With respect to uniformly -loaded cables it should also be men- 

 tioned that Messrs. Henley's Telegraph Works Company liave made 

 and laid several uniformly-loaded submarine cables. 



In 1907 they supplied 25 kilometres of such 4-core cable in- 

 sulated with guttapercha to the Royal Danish Administration made 

 to the specification of the late Mr. Krarup. The copper strand was 

 wound over uniformly with a single layer of soft iron wire 0*55 mm. 

 in diameter. This cable was laid in the Faroe Islands early in 1913 ; 

 they made and laid on the Pacific Coast a similarly uniformly loaded 

 cable 31 nautical miles in length. The loading is a single layer of 

 iron wire 0*3 mm. (0*012 in.) in diameter. This last cable is laid 

 from Xanainio in Vancouver's Island to the mainland in British 

 Columbia. 



It is said to be the longest uniformly loaded cable yet put down. 

 It is a two circuit cable and is arranged for phantom working. The 

 attenuation constant at 800 frequency is 0-019. 



