PLANNING AND OVER-ALL PERFORMANCE 9 



Telecommunication Corporation. It is thus the joint effort of three 

 nations. 



In planning the system, the main centres of interest were, naturally, 

 the two submarine cable sections, Scotland to Newfoundland, and New- 

 foundland to Nova Scotia, each of which had to meet a unique combina- 

 tion of requirements imposed by water depth, cable length and trans- 

 mitted bandwidth. 



OVER-ALL VIEW OF THE SYSTEM 



The transatlantic system provides 29 telephone circuits between Lon- 

 don and New York, six telephone circuits between London and Mont- 

 real, and a single circuit split between London — New York and Lon- 

 don — Montreal ; this split circuit is available for telegraph and other 

 narrow band uses. There are also 24 telephone circuits available for local 

 service between Newfoundland and the Mainland of Canada, and there 

 is considerable excess capacity over the radio-relay link that crosses the 

 Maritime Provinces of Canada. 



A map of the system is shown in Fig. 1 ; the facilities used, together 

 with the approximate route distances are shown in Fig. 2. It will be 

 seen that the over-all lengths of the London to New York and London to 

 ]\Iontreal circuits are 4,078 and 4,157 statute miles respectively. Seven 

 of the New York to London circuits are permanently extended to Euro- 

 pean Continental centres — Paris, Frankfurt (2), Amsterdam, Brussels, 

 Copenhagen and Berne. The longest circuit is thus New York to Copen- 

 hagen, 4,948 miles. 



Starting at London, which is the switching centre for United Kingdom 

 and Continental points, 24-circuit carrier cables provide two alternative 

 routes to Glasgow and thence to Oban by a new coaxial cable. Between 

 London and Oban the two routes are fed in parallel at the sending ends, 

 so a changeover can be effected at the receiving ends only. At a later 

 date, an alternative route out of Oban will be provided by a new coaxial 

 cable to Inverness. 



From Oban a deep-sea submarine link connects to Clarenville, New- 

 foundland. This link is in fact two parallel submarine cables, one vised 

 for east-to-west transmission, the other for transmission in the reverse 

 direction. Each cable is roughly 1,950 nautical-miles in length and lies 

 at depths varying between a few hundred fathoms on the continental 

 shelf and about 2,300 fathoms at the deepest point. Each cable incorpo- 

 rates 51 repeaters in flexible housings which compensate for the cable 

 attenuation of about 3,200 db at the top frequency of 164 kc. These 



