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 (f)  
During the raster mode, the raster directives are sent to the raster generation circuitry. The raster directives instruct the raster generation circuitry to generate the EADI sky/ground ball in the EADI mode or weather radar display in the EHSI mode.

 (g)  
The outputs from the stroke and raster generation circuits are transmitted to the display driver. The display driver performs the following functions: 1) Converts the digital stroke data to analog deflection

 signals. The analog deflection signals are then
 transmitted to a display unit.
 2)  Converts the digital raster sweep data to analog sweep signals. The analog sweep signals are then transmitted to a display unit.
 3)  Selects either stroke deflection or raster sweep signals to be sent to each display unit 4) Generates a dither signal (slight movement of the display beams) to protect the phosphorus coating on the CRT.
 (h)  
The directives contained in the display tables also determine the color in which a certain symbol is to be displayed on the EADIs and EHSIs. Three color guns (red, green, blue) within each display unit provide for the display of symbols on the CRT. The colors red, green, and blue can be produced by the color guns. These colors can also be combined to produce cyan, magenta, yellow, or white. The color signals are transmitted to the color guns through video amplifiers. The display brightness is controlled by controlling the gain of the video amplifiers.

 (i)  
Raster and stroke data are each updated 80 times per second. Raster is written on the EHSI while stroke is written on the EADI, and vice versa. Hence, the total display on each EADI and EHSI is updated 40 times per second.

 (5)  System Monitoring
 (a)  The EFIS symbol generator monitors the integrity of the system, as well as checking its own operation. Failures detected by the symbol generator are recorded in its BITE memory. After a failure has been recorded in the BITE memory, the symbol generator will take appropriate action to either halt the raster operation, thus blanking the raster portion of the display, or display fault messages on the CRT. In the event of a major malfunction, or extreme overtemperature, the CRT displays will blank.
 B.  Control
 (1)  Power is applied to the EFIS by closing the following circuit breakers on the P6 and P18 circuit breaker panels:
 (a)  EFIS SYM GEN (L and R)
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

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737-300/400/500MAINTENANCE MANUAL
 (b)  EFIS CONT PNL (L and R)
 (c)  EHSI (CAPT and F/O)
 (d)  EADI (CAPT and F/O)
 (2)  The data to be displayed on the display units are controlled by the
 switch settings on the EFIS control panels.
 (3)  During normal operation, there is only one basic display mode on the
 EADIs.  However, the EHSI is capable of displaying in several modes,
 depending upon the position selected by the mode selector switch.

 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

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 ELECTRONIC FLIGHT INSTRUMENT SYSTEM (EFIS) - TROUBLE SHOOTING
_____________________________________________________________
 1.  General_______
 A.  Malfunctions or failures of the EFIS can be identified with the FMS BITE (Built-In Test Equipment) procedures, which are in Chapter 22. The FMS BITE includes procedures for the FMCS, DFCS, A/T, IRS, and EFIS.
 B.  The FMS BITE is started and controlled through the FMCS CDU. The CDU is used for control and display to actuate and make an analysis of the FMCS, DFCS, A/T, IRS, and EFIS BITE (Ref 22-01-10, FMS BITE - D&O). When the test has been started from the CDU, the system which is tested will transmit text messages to show on the CDU. In response to the messages, the operator can set flight deck controls, and/or put data entries into the CDU. Test pass or failure is shown on the CDU display.
　
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