PLANNING AND OVER-ALL PERFORMANCE 11 



cables carry 36 telephone circuits plus maintenance circuits and estab- 

 lish the present maximum capacity of the transatlantic system. 



At Clarenville, connection is made with Sydney Mines, Nova Scotia, 

 by a second cable system which goes 63 statute-miles over land to Ter- 

 renceville, Newfoundland, and thence about 270 nautical-miles in coastal 

 waters at a depth of about 250 fathoms. Although this system is partly 

 on land, it is basically a submarine system in design, the two portions 

 differing only in the protection of the cable. In this hnk, the two direc- 

 tions of transmission are carried by the same cable, a low-frequency band 

 being used from west-to-east and a high-frequency band in the opposite 

 direction. In addition to the necessary maintenance circuits, a total of 

 60 two-way circuits are provided, 36 being used for transatlantic service, 

 and the remainder being available for service between Newfoundland 

 and the Mainland. Sixteen two-way repeaters in rigid containers provide 

 close to 1,000 db gain at this system's top frequency of 552 kc. 



From Sydney Mines, transmission is by radio-relay to the United 

 States-Canada border and thence to Portland, Maine; this system 

 operates at about 4,000 mc and includes 17 intermediate stations. From 

 Portland, standard 12-circuit carrier and coaxial cable facilities are used 

 to connect with White Plains, New York, the American switching center 

 30 miles north of New York City, where connection is made to the Bell 

 System network. 



The Montreal circuits leave the radio-relay route at Spruce Lake, a 

 relay station near the Border, from which point a short radio spur con- 

 nects to St. John, New Brunswick, thence to Quebec on a 12-circuit 

 open-wire carrier system and thence to Montreal on a 12-circuit cable 

 carrier system. 



BACKGROUND TO THE SUBMARINE CABLE SYSTEMS 



The submarine cable sections have been built upon a long background 

 of experience. Some of the cable laying and design techniques go back to 

 the early telegraph cables of almost a century ago, and Lord Kelvin's 

 analysis of the laying process is still the standard mathematical treatise 

 on the subject. It is also interesting to note that the firm which provided 

 most of the cable is a subsidiary of the organization that manufactured 

 and laid the first successful transatlantic telegraph cable some 90 years 

 ago. 



In addition to the long experience in submarine telegraphy, the trans- 

 atlantic system has drawn on over a quarter of a century of experience 

 of telephone cable work in the British Post Office and the Bell System. 



