THE L3 SYSTEM — EQUALIZATION AND REGULATION 



861 



satisfactory. Also the power method is usable with sawtooth as well as 

 triangular scanning and, further, works on any set of orthogonal gain 

 or delay shapes. Thus the basic equipment is readily adaptable to the 

 adjustment of D equalizers if their gain and delay shapes are orthogonal. 



FIELD PERFORMANCE 



In the L3 system the function of the dynamic equalizers is solely to 

 prevent excessive deterioration of the transmission characteristic from 

 one manual line-up to the next. During the manual adjustment the 

 dynamic networks are held at that point in their range which minimizes 

 the probability of running out of range in either direction before the 



/SECOND HARMONIC 



THIRD HARMONIC 



ti 



2t, 



3t, 



Fig. 16 — Detector output produced by scanning the first three cosine shapes. 



next manual line-up. This is done to hold the dynamic ranges to a mini- 

 mum. Thus the transmission errors remaining at the completion of a 

 manual line-up are chiefly due to the fixed and manual equalizers. It 

 should be noted however that, when the dynamic regulators are re- 

 stored to operation after the manual adjustment, any residues will be 

 seized by the dynamics and regulated. 



As yet the field experience with the regulation system and the dynamic 

 shape performance is quite limited. However, the stability of the regu- 

 lation system and the action of the computer have been well established. 

 It would appear that the major remaining regulation system problem 

 will be the determination of the cause shapes to the accuracy required 

 for long television systems. 



Somewhat more experience has been gained with the cosine equalizers. 

 Using a fixed equalizer design based on ten line amplifiers from initial 

 production, a 100-mile circuit equalized using 15-cosine terms yields 

 the residues plotted on Fig. 17. The ripple at the extreme high end of 



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