The AZIMUTH – RANGE indicator (Figure 1-11-5) is a Plan Position Indicator (PPI) which provides display of the following functions:

a. Radar returns oriented to true or relative heading, depending on selection made.
b. A heading marker which is illuminated by the PPI sweep.
c. A continuously displayed bearing cursor and range strobe which allows relative range and bearing measurements to be made with respect to the aircraft.

Mounted on the indicator front panel is a mechanically rotated protractor and five controls whose functions are as follows:

a. The HEADING control is a two-position rotary switch providing the following functions;

(1) TRUE. In this position the heading marker is referenced to true north.
(2) ACFT. In this position aircraft heading is at the top of the indicator and the display is relative to the fore and aft axis of the aircraft.

b. The HEADING IND control is a slotpotentiometer which varies the brightness of the heading marker.
c. The VIDEO GAIN control is a slotpotentiometer which varies the displayed video returns by varying the gain of the video circuits.
d. The BRIGHTNESS control is a dual-integral potentiometer providing the following functions;

(1) PPI. Rotation of the inner control varies the background intensity of the display.
(2) RNG/BRG. Rotation of the outer control varies the brightness of the range strobe and the bearing cursor.

e. The PROTRACTOR control is a dual-integral potentiometer providing the following functions;

(1) BRIGHTNESS. Rotation of the inner control varies the brightness of the edge lighting around the protractor.
(2) POSITION. Rotation of the outer control mechanically rotates the protractor.