500 BELL SYSTEM TECHNICAL JOURNAL 



meeting both the mechanical and electrical requirements. With the 

 further development of intercontinental communications, it is proposed 

 to lay such a cable within a few years. With the materials now 

 available, such a cable will provide only one channel of communica- 

 tion, and two-way communication will be carried out by using it as a 

 one-way channel automatically switched in the direction of transmis- 

 sion by the voices of the users. Transatlantic cables providing several 

 telephone channels either by the use of separate conductors or by 

 carrier current methods are beyond the range of the present art. 



The direct submarine cable while relatively expensive, is expected 

 to provide a high grade circuit having a stability and a freedom from 

 interruption greater than that provided by the present radio circuits. 

 Proper combination of three different types of circuit, long and short- 

 w^ave radio and cable, in one circuit group, however, should provide a 

 large measure of assurance of continuous high grade service not 

 dependent on the troubles which may affect any one type of circuit, 

 and at an average expense not greatly above that required for radio 

 circuits alone. 



Other Wire Routes 



The technical possibilities of wire circuits on intercontinental routes 

 are evidently greatly increased where means can be found to avoid 

 long lengths of submarine cables by the use of intermediate repeater 

 stations. On the direct route between Europe and America, nature 

 has not been kind enough to supply a series of islands at convenient 

 distances and reasonably low latitudes to serve as repeater points. 

 By going north, long lengths of submarine could be avoided. For 

 example, a route through Greenland, Iceland and the Faroe Islands 

 could be laid out with a maximum length of submarine cable of 

 300 miles (500 kilometers). The obvious difficulties of the route are 

 the great extents of inaccessible and sparsely settled country, and the 

 placing and maintenance of submarine cable under very difficult fog, 

 storm and ice conditions. In the early days of submarine telegraphy 

 such a northern route was seriously considered before the cable art had 

 reached the point of permitting direct cables, but it was never used. 



An equally bold solution which has been proposed is to float the 

 desired repeater stations in the open sea. A good deal of ingenuity 

 has been exercised in considering the possibilities of both attended 

 and unattended floating repeater stations and of stations submerged 

 below the action of the waves. So far, however, it is by no means 

 clear that the mechanical difficulties and the problems of maintenance 

 can be dealt with satisfactorily. 



