DESIGN OF SYSTEM 



XORTH ATLAXTIC LINK 



43 



t The psophometer is the C.C.I.F. circuit noise meter. On message telephone 

 circuits, dbm (psophometer) + 84 = dba using C.C.I.F. 1951 weighting and Bell 

 System FIA weighting. 



Control of this misalignment required extensive consideration in the 

 equalization design of the system. 



Causes of Misalignment 



The basic causes of misalignment can be grouped as follows: those 

 producing unequal repeater levels when the system is first laid; those 

 resulting from changes in cable loss produced by changes in sea-bottom 

 temperature; and those from aging of the cable or repeaters. 



There are a large number of possible causes of initial misalignment. 

 While the cable and repeaters were manufactured within very close 

 tolerances to their design objectives, they covild not exactly meet those 

 objectives. In addition, the cable loss as determined in the factory must 

 be translated to the estimated loss on sea-bottom, and the length of each 

 repeater section must be tailored in the factory so that its expected sea- 

 bottom loss will best match the repeater gain. Possible sources of error 

 in this process include: uncertainty in temperature of the cable when it 

 is measured in the factory, and in its temperature on the sea-bottom; 

 uncertainty in temperature and pressure coefficients of attenuation; 

 changes in cable loss between factory and sea-bottom conditions, not 

 accounted for by pressure and temperature coefficients. 



These latter changes in cable loss were called "lajing effect". The 

 determination of the magnitude of laying effect, and its causes, are dis- 



