TRANSATLANTIC COMMUNICATIONS 3 



laying gear without requiring the ship to be stopped each time a repeater 

 is laid. The advantages of this flexible housing have been apparent dur- 

 ing the laying operations of 1955 and 1956. They have made it possible 

 to continue laying cable and repeaters under weather conditions which 

 would have made it extremely difficult to handle rigid repeater housings 

 with the methods at present available. 



A single connecting cable has been used across Cabot Strait between 

 Newfoundland and Nova Scotia. The sixteen repeaters in this section 

 have been arranged electronically to give both-way amplification and 

 the single cable provides "go" and "return" channels for sixty circuits. 

 "Go" and "return" channels are disposed in separate frequency bands. 

 The design is based closely on that used by the British Post Office in 

 the North Sea. Use of a single cable for both-way transmission has 

 many attractions, including that of flexibility in providing repeatered 

 cable systems, but no means has yet been perfected of laying as part of 

 a continuous operation the rigid repeater housings that are required 

 because of the additional circuit elements. This is unimportant in rela- 

 tively shallow water, but any operation that necessitates stopping the 

 ship adds appreciably to the hazards of cable lajdng in very deep water. 



The electron tubes used in the repeaters between Newfoundland and 

 Scotland are relatively inefficient judged by present daj^ standards. 

 They have a mutual conductance of 1,000 micromhos. Proven reliability, 

 lower mechanical failure probability and long life were the criteria that 

 determined their choice. Electron tubes of much higher performance 

 with a mutual conductance of 6,000 micromhos are used in the New- 

 foundland-Nova Scotia cable, and it is to be expected that long re- 

 peatered cable systems of the future will use electron tubes of similar 

 performance. This will increase the amplification and enable a wider 

 frequency band to be transmitted; thus assisting provision of a greater 

 number of circuits. If every advantage is to be taken of the higher 

 performance tubes, it will be necessary to duplicate (or parallel) the 

 amplifier elements of each repeater, in the manner described in a later 

 paper, in order to assure adquately long trouble-free performance. This 

 has the disadvantage of requiring the use of a larger repeater housing. 



During the three years that have elapsed since the announcement in 

 December, 1953 by the American Telephone and Telegraph Company, 

 the British Post Office, and the Canadian Overseas Telecommunication 

 Corporation, of their intention to construct the first transatlantic 

 telephone cable system, considerable progress has been made in the 

 development and use of transistors. The low power drain and operating 

 voltage required will make practicable a cable with many more sub- 



