TM 1-1510-223-10 Change 3          3-59 NOTE When storing a frequency the second actuation of the STO switch must be done within 5 seconds after selecting the channel number or the first actuation of the STO switch. If more than 5 sec- onds elapse, the control will revert to the normal modes of operation and the second store com- mand will be interpreted as the first store com- mand. After a frequency has been stored in memory, it will re- main  there  until  changed  by  using  the  STO  switch. Memory is retained even when the unit is turned off for an extended period of time. d.   Self-Test.  During  self-test,  the  VIR-32  provides VOR, ILS, and marker beacon test outputs. The following paragraphs provide the procedures required and the re- sults to be expected when performing the self-test. (a)   VOR Self-Test 1. Tuning knobs (NAV control unit) - Select a VOR frequency. NOTE A specific frequency is not required for the test. Also, a signal on the frequency will not interfere with the self-test. 2. VOR/localizer pushbutton selector switch (display controller, fig. 3-8) -  Select  VOR1  or  VOR2,  as  re- quired. 3. Single-needle bearing pointer source    selector    switch    (display controller, fig. 3-8) - Select VOR1. 4. Double-needle bearing pointer source    selector    switch    (display controller, 3-8) - VOR2. 5. Course  knob  (HSI)  -  Rotate  until course  pointer  indicates  approxi- mately 0 degrees. 6. TEST  switch  (NAV  control  unit)  - Depress and hold. 7. NAV flag on the HSI will come into view.  After  approximately  2  sec- onds the flag will go out of view, the HSI    course    deviation    bar    will approximately center, and a TO in- dication  will  appear.  The  bearing pointers will indicate approximate- ly  a  0-degree  magnetic  bearing. The  VIR-32  will  return  to  normal operation  after  approximately  15 seconds, even if the TEST switch is held. (b)   ILS (Localizer and Glide Slope) Self-Test. 1. Tuning knobs (NAV control unit) - Select a localizer frequency. NOTE A specific frequency is not required for the test. Also, a signal on the frequency will not interfere with the self-test. 2. TEST  switch  (NAV  control  unit)  - Depress and hold. 3. HSI  -  NAV  and  GS  (glide  slope) flags   will   come   into   view.   After approximately 3 seconds, the flags will go out of view, the HSI course deviation    bar    will    deflect    right approximately 2/3 of full scale and the glide slope pointer will deflect down   approximately   2/3   of   full scale. 4. The  VIR-32  will  return  to  normal operation  after  approximately  15 seconds, even if the TEST switch is held. (c)   Marker   beacon   self-test. The   marker beacon assembly is tested automatically when the self- test is actuated and either a VOR or localizer frequency is selected. Proper operation of the marker beacon as- sembly is indicated when all three marker indicators are displayed on the EADI. A 30 Hz tone will also be present in the marker beacon audio output. (d)   Marker  beacon  audio. Marker  beacon audio generally associated with an ILS, must be source selected by the NAV A or B audio selector switches lo- cated on the audio control panel. Sensitivity selection for marker beacon audio is accomplished by a toggle switch placarded MKR BCN HI-LO, and audio volume is con- trolled by a knob placarded VOL (both are located on the pedestal extension, fig. 2-12). (e)   Diagnostic display. NOTE The diagnostic routines are intended as an ex- tension   of   the   self-test   capability.   The   pilot should first observe the deviation indicators and associated   flags   for   the   proper   self-test   re- sponses. If a fault condition exists, the problem may be verified in more detail by the diagnostics.