14 BELL SYSTEM TECHNICAL JOURNAL 



insulating materials a somewhat more favorable design would have been 

 obtained. On this cable 47 repeaters spaced 42 miles apart would provide 

 for the transmission of a band 48,000 cycles wide. 



r The repeater is a one-way device and to provide two-way conversations 

 two cables have been assumed, one directed eastward and the other west- 

 ward. This is the simplest solution of the two-way problem but it is not 

 inconceivable that the problem could be solved with a single cable. Using 

 two cables, each transmitting 48,000 cycles, the number of telephone cir- 

 cuits will depend on the band assigned per channel. If we adhere to the 

 present best land-line practice, and assign 4000 cycles per channel there 

 would be room for 12 telephone circuits. For a small sacrifice of quality 

 the number could be materially increased. Even as many as 24 fairly 

 satisfactory circuits could be provided by assigning only 2000 cycles per 

 channel. 



Although in Bell Laboratories we have gone a considerable distance in 

 the design of a broad-band repeatered submarine telephone cable, and have 

 developed many of the essential parts, I would not wish to give the impres- 

 sion that all the problems of such a cable have been solved, or that the time 

 has come to proceed with its construction and installation. Indeed, it is 

 only by building trial sections of such a cable and subjecting them to re- 

 peated punishment more severe than a cable is likely to encounter, that the 

 problems can be fully recognized. Extensive electrical tests will also have 

 to be made on a complete assembly of repeaters with artificial lines simu- 

 lating sections of cable. These steps have yet to be taken. 



A submarine cable requires a degree of care and precaution in engineering 

 such as is required in few other situations. It is usually not possible to 

 provide large factors of safety, and yet failure of a single part such as a 

 break in the conductor or a leak in the insulation completely destroys the 

 operation of the whole system. Experiences of over eighty years since the 

 failure of the first attempt at an Atlantic cable have led to the development 

 of practices which give good assurance of the reliability of cables of simple 

 construction, but when a device such as the proposed repeater is made a 

 part of the structure a new set of hazards is introduced. Whether these 

 hazards can be guarded against well enough to justify the risks of such a 

 cable project remains to be seen, but I am optimistic that by a sufficiently 

 thorough job of cable manufacture and a well planned program of trials, 

 the hazards can be reduced to an acceptable degree. It will take some 

 years to reach this point, and at best it must be expected that some degree 

 of hazard will still remain.' Submarine cables, like all things that go to 

 sea, can never be completely dissociated from some chance of disaster. 



As to the costs of such a cable project for establishment of broad-band 

 wire telephony to England via Newfoundland, only the roughest sort of 



