24 THE BELL SYSTEIVI TECHNICAL JOUKXAL, JANUARY 1957 



There was an understanding that there should be no deliberate attempt 

 to make the characteristics of one link compensate for those of another, 

 and so it would be incumbent on the administrations to produce the 

 best possible group characteristic on each link. 



The overall plan for the system, as finally developed, is shown in Fig. 2. 

 Except for the necessity to split one of the three transatlantic groups in 

 each direction to provide 6^ circuits to Montreal and 5| to New York, 

 which required specially designed crystal filters, no unusual circuit 

 facilities were required. 



Special equipment arrangements were called for at Sydney Mines and 

 Clarenville to provide security for the Montreal-London circuits where 

 they appeared in the same office with White Plains-London circuits. In 

 these cases, a special locked room was constructed to house the equipment 

 associated with the channel group containing the Canadian circuits. 



The details of how the two all-important submarine cable links were 

 designed and engineered to meet their indi\'idual objectives are given in 

 companion papers. The efficiency and integrity of these two links are 

 the highest that could be devised by engineers on both sides of the 

 Atlantic. 



Finally, each section of the connecting links was lined-up and tested 

 individually before bringing them all together as an integrated system. 



OVER-ALL PERFORMANCE OF THE SYSTEM 



The system went into service on September 25, 1956, so soon after 

 completion of some of the links that it was not possible to include all 

 the final equalizers. Nevertheless, after completion of the initial overall 

 line-up, the performance has been found to meet very closely the orig- 

 inal objectives. The system went into service without the use of com- 

 pandors on any of the telephone circuits, but compandors are included in 

 the program equipment. At the time of writing, onlj^ the 2-channel 

 program equipment is available for use. 



Frequency Characteristics of 12-channel groups 



Fig. 5 shows the frequency characteristic of one of the 12-channel 

 groups, link b}' link and over-all, measured at group frequencies corre- 

 sponding to 1,000 cycles on each channel. In both of the complete 

 London-New York groups the deviation from flat transmission is within 

 ±1.5 db, and some further improvement is to be expected when the 

 equalization is finalized. For the split group, the characteristics are 

 similar except for the effect of the splitting filters. 



