Chapter 5 — CLOUDS AND VISIBILITY 



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Figure 5-21. — Converter-Indicator Group OA-7900A/GMQ-10. 



209.139 



They are based on a 500-foot baseline between 

 the transmissometer projector and receiver. 



The visibility system will convert pulse 

 rates from transmissometer sets of other 

 baselines provided the visibility values to be 

 displayed are properly related to the pulse 

 rates, and encoded on the encoder disc. 



The visibility values are displayed digitally 

 in increments of 200 feet ranging from 1,000 

 to 6,000 feet. Values less than 1,000 and greater 

 than 6,000 feet are displayed as 800 feet 

 and 6,200 feet respectively. Actually, the values 

 are displayed as two-digit numbers which should 

 be multiplied by a factor of 100 in order to 



obtain the correct reading. When the equip- 

 ment is tested or the runway lights are OFF 

 the red light indicator on the display panel 

 is ON. Consequently, the displayed values should 

 not be accepted as true values of RVR. 



SIGNAL DATA CONVERTER CV-3125/GMQ- 

 10. — The Signal Data Converter is designed 

 for rack mounting. Mounting slides are provided 

 with the unit to enable forward withdrawal 

 from the rack in order to gain easy access 

 to its interior. The chassis Is completely en- 

 closed to prevent foreign objects from falling 

 inside, which may cause shorts and general 

 damage. All switches are located on the front 

 panel and all connections are in the rear. 



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