TM 55-1510-219-10 Pilot's compass Selects desired source of magnet- No.  1/No.  2 ic heading data for display on switch HSI compass card. No.  1 Selects data from No.  1 com- pass. No.  2 Selects data from No.  2 com- pass. c.  Controls and Indicators - Copilot's HSI. NOTE A    PILOT    SELECT    annunciator, located  on  the  copilot  side  of  the instrument panel, illuminates whenever the setting of the copilot's COURSE INDICATOR switch  matches  that  of  the  pilot's COURSE  INDICATOR  switch.    In this condition the copilot's HSI is "slaved" to the pilot's HSI, and the copilot has no control over course    select    functions    of    the selected NAV receiver.  The PILOT SELECT    annunciator    does    not illuminate when INS is selected. (1)  Copilot's HSI (fig.  3-11). CONTROL/ FUNCTION INDICATOR Heading marker Indicates  heading  selected  by HDG knob. COMPASS flag Indicates that the heading infor- mation displayed is invalid and should not be used. Lubber line This pointed fixed index mark aligns with the aircraft symbol to indicate aircraft magnetic head- ing on the compass card. Course pointer Indicates  VOR/TACAN  radial course selected by COURSE knob. Rotating heading The rotating heading dial, which dial rotates with the aircraft through- out 360 degrees, displays gyro stabilized magnetic compass in- formation.  The azimuth ring is graduated in five-degree incre- ments. COURSE Provides a digital readout of the indicator selected course. VOR LOC flag Flag indicates that information derived from the selected navi- gational beacon is invalid and should not be used. COURSE The yellow course arrow is posi- control tioned on the heading dial by Figure 3-11.  Copilot's Horizontal Situation Indicator (331A-6P) 3-21