SYSTEM DESIGN' — XEWFOUXDLAXD-XOVA SCOTIA LIXK 221 



When the 36-circuit system between Aberdeen, Scotland, and Bergen, 

 Norway, was planned in 1952, the route length (300 nautical miles) 

 greatly exceeded that of any other submarine telephone sj^stem, and it 

 was decided to use a core diameter of 0.935 inch, first, to keep the number 

 of repeaters as low as seven, and second, because the system was in- 

 tended as a prototype of a possible Atlantic cable. The cable dielectric 

 is polyethylene (Grade 2) with 5 per cent polyisobutylene. 



For the Clarenville-Sydney Mines link it proved possible to design 

 for minimum annual charges. With increasing experience and confidence 

 in submerged repeaters, it was no longer considered necessary to restrict 

 the number of repeaters as for Aberdeen-Bergen, and the terminal volt- 

 age requirements were reasonable. At the current prices of cable and 

 repeaters in Great Britain the optimum core diameter for 60 both-way 

 circuits is about 0.55 inch, but the increased charge incurred by using 

 0.62-inch cable is less than 5 per cent (0.62-inch core is optimum for 120 

 both-way circuits). In order to facilitate manufacture and the provision 

 of spare cable, it was therefore logical to adopt the same design as that 

 proposed for the Atlantic crossing and described elsewhere.^' ^ 



After investigating various possible types of cable for the overland 

 section in Newfoundland, it was decided to use a design essentially the 

 same as the main cable but with additional screening against external 

 interference.* As far as the outer conductor and its copper binding tape, 

 the construction (Fig. 3) is identical with that of the main cable except 

 that the compounded cotton tape is overlapped. Outside this are five 

 layers of soft-iron tapes each 0.006-inch thick, the innermost being longi- 

 tudinal and the others having alternate right- and left-hand lays at 45° 

 to the axis of the cable. After another layer of compounded cotton tape 

 there is extruded a polyethjdene sheath 0.080 inch thick, and the whole is 

 jute served and wire armoured. As a check on the efficiency of the 

 screening, the maximum sheath-transfer impedance at 20 and 100 kc 

 was specified as 0.005 ohm per 1,000 j^ards. 



It was thus possible to treat the entire link from Clarenville to Syd- 

 ney Mines as a uniform whole, using the same type of repeater on land 

 as in the sea. A small hut at Terrenceville contains passive networks 

 only. 



Attenuation Characteristics 



When the system was designed, precision measurements of cable at- 

 tenuation were not available. The design of the Oban-Clarenville link 

 ^vas based on laboratorv measurements on earlier 0.62-inch cable of a 



