TM 1-1510-223-10 on the EHSI between VOR1 or VOR2, or ILS1 or ILS2, depending  upon  whether  a  VOR  or  localizer  frequency has  been  selected  on  the  respective  VHF  navigation receiver control panel. The VOR/localizer switch may be used to activate the preview mode on the EHSI if: INS is displayed on the EHSI as the navigation source LNAV flight director mode annunciator is displayed on the EADI System is powered-up using the primary on-side VHF navigation receiver. The  preview  mode  may  be  cancelled  by  depressing the V/L switch (7) INS/TACAN      pushbutton   selector   switch. The     inertial     navigation     system/TACAN     pushbutton selector  switch,  placarded  INS/TCN,  is  used  to  select whether  the  INS  or  TACAN  will  provide  information  to the  EFIS.    Each  depression  of  the  switch  will  alternate the navigation source annunciator on the EHSI between INS and TCN. (8) Double-needle pointer bearing source selector   switch.      The   double-needle   pointer   bearing source selector switch, located on the lower right side of the display controller, is used to select which navigation information    sources    will    provide    information    to    the double-needle bearing pointer. (a) OFF. Removes double-needle pointer from the EHSI. (b) VOR2. Double-needle pointer receives  bearing  information  from  #2  VHF  navigation receiver. (c) ADF.  Double-needle pointer receives bearing information from ADF navigation receiver. (d) INS.    Double-needle  pointer  receives bearing information from the inertial navigation system. (e) TCN.  Double-needle pointer receives bearing information from TACAN navigation receiver. (9) Weather  radar  dim  control.  Control  of  the intensity  of  the  weather  radar  display  on  the  EHSI  is accomplished   by   a   control   knob   placarded   WX   DIM, which   is   an   inner   concentric   knob   with   the   HSI   DIM knob. The WX DIM control dims only the raster on the EHSI which   contains   the   weather   radar   information.   If   the EHSI is in the composite mode with the EADI, the WX DIM control is used to dim the attitude sphere. (10)  EHSI dim control.  Control of the intensity of the raster and stroke writing on the EISI is accomplished by a control knob placarded HSI DIM, which is an outer concentric  knob  with  the  WX  DIM  knob.  Turning  the knob  counterclockwise  to  the  OFF  position  will  cause the  EHSI  to  become  blank  and  the  composite  mode  to be displayed on the EADI. (11)  Decision height setting control and EFIS test switch (a) Decision  height  setting  control.    The decision height setting control, placarded DHIRET, is an inner  concentric  knob  with  the  ADI  DIM  knob.  Rotating the  DH  knob  allows  setting  the  decision  height  display on the EADI in 10-foot increments from 200 to 990 feet, and in 5 foot increments from 0 to 200 feet By rotating the  DH  knob  completely  counterclockwise  to  the  OFF position,  the  decision  height  display  may  be  removed from the EADL (b) EFIS   test   switch.      Depressing   the EFIS  test  switch,  placarded  TEST,  will  cause  the  EFIS displays  to  enter  a  test  mode.    In  the  test  mode,  flags and cautions are presented along with a test of the radio altimeter.    Observe  the  following  after  depressing  the TEST switch: NOTE A complete test of the EFIS is only functional on    the    ground.        Radio    altimeter    test    is functional at all times except during glideslope CAP/ TRK Course select, heading select, DH set, DME distance, and  GSPD/TTG  digital  displays  are  replaced  by  amber dashes. ATT and HDG displays are flagged. All pointers and scales are flagged. All heading related markers and pointers are removed. Flight control computer standby mode is activated. (12)   EADI dim control. Control of the intensity of the raster and stroke writing on the EADI is accomplished   by   a   control   knob   placarded   ADI   DIM, which    is    an    outer    concentric    knob    with    the    DH SETREST knob.  Turning the knob counterclockwise to the  OFF  position  will  cause  the  EADI  to  become  blank and the composite mode to be displayed on the EHSL (13)   Single-needle pointer bearing source selector    switch.    The    single-needle    pointer    bearing source selector switch, located on the lower left side of the display controller, is used to select which navigation information 3-24