MEASURfXG SySTK.\f FOR VIDEO 



233 



d-c. ami)lirier which luis adjusluble gain to adjust scale factors on the 

 indicator. The phase detection circuit is energized from the output of the 

 phase bridge and the almost identical transmission detection circuit is 

 energized from the inputs to the phase bridge. Thus both phase and 

 transmission are measured simultaneously. 



Each indicator (Fig. 9) has three sca\es, fine ( — 5° to +5°; —1 db to +1 

 db), coarse (-90° to +90°; -10 db to +3 db), and null balance. The 

 fine and coarse scales are linear while the null balance scale has maximum 



Fig. 9 — Phase and transmission indicators. 



sensitivity in the neighborhood of the center zero and greatly reduced 

 sensitivity at each end. X'aristor shunts across the indicators compress 

 the null scale for large deflections. Colored {)ilot lights at the ends of the 

 indicator scales, operated by the scale switch, indicate the scale in use 

 directly. 



TiiK PiiASK Shifter 



The phase-shifter employs a four-quadrant variable sine condenser. 

 It has two linearly subdivided scales — coarse 0-360° on a cylinder and fine 



