THE L3 SYSTEM EQUALIZATION AND REGULATION 857 



-2 



-3 



1000 2000 3000 4000 5000 6000 7000 8000 9000 

 FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 11 — Shapes introduced by the first three cosine harmonics. 



are individual measures of equalizer control-setting errors. By the ad- 

 justment process these audio harmonics are removed thus yielding a 

 gain characteristic describable in terms of only the higher cosine com- 

 ponents not available to the equalization operator. 



The operation can be explained using the block diagram shown on 

 Fig. 14. The sweep oscillator sends a constant level, variable frequency, 

 over the line and through the cosine equalizer to the detector. The output 

 of the detector on terminals x-x at any instant is a measure of the trans- 

 mission of the line and equalizer at the frequency being sent by the 

 sweep oscillator at that instant. The sweep frequency starts at zero 

 and sweeps to 8.5 mc in a period ^i. As shown on Fig. 15 the frequency- 

 time relationship is warped to correct for the warping of the equalizer 



