TM  55-1510-221-10 b.   Controls   and   Functions   (ADF   Control Panel, fig. 3-18). (I.)   L-LOOP-R   control.  Operative   only when  the  function  switch  is  in  the  LOOP  or  ADF position.  Center  position  removes  rotation  signals from the loop antenna and the ADF pointer on the RMl's. L (left) or R (right) of center applies rotation signals to loop antenna and ADF pointer on RMI's for 360-degree rotation left or right. Center position holds antenna position. (2.)  BFO-OFF.  At  BFO  (on)  setting,  per- mits  line  tuning  with  Beat  Frequency  Oscillator (BFO).  Also  provides  audio  tone  when  receiving unmodulated CW. OFF position turns BFO off. (3.)  Tuning  meter.  Indicates   relative strength  of  received  signals. (4.)  TUNE  control.  Selects   operating   fre- quency. (5.)  Range  switch.  Selects  operating  fre- quency band. (6.)   FREQUENCY   indicator.   Indicates selected   frequency. (7.)  Mode  selector.  Selects  operating mode. (a.)  OFF.  Turns  set  off. (b.)  ADF.  Permits   automatic   direc- tion finding or homing operation. (c.)  ANT.  Permits  reception  using sense  antenna. (d.)  LOOP.  Permits   audio-null   hom- ing and manual direction finding operations. (8.)  GAIN  control.  Adjusts  volume  of received  signal. c.   Controls   and   Functions Panel, jig. 3-1). (1.)   NAV-B   switch.   O N ADF audio to respective headset. d.  Controls  and  Functions Audio  Panel,  fig.  3-2). (1.)   FILTER   V-OFF (Audio   Control position  applies (Marker  Beacon switch. Selects whether  voice  filter  will  be  used  with  ADF  audio. (2.)  FILTER  R-OFF  switch.  Selects whether range filter will be used with ADF audio. 3-34 NOTE Range  and  voice  filtering  are  cancelled when both FILTER R and FILTER V are ON. Range and voice audio will be heard. e.  ADF  Normal  Operation. (1.)    To 1. 2. 3. 4. 5. 6. 7. 8. 9. (2.)     To receiving  only. 1. 2. 3. 4. (3.)     To finding. 1. 2. 3. 4. 5. 6. operate the set as ADF. Mode selector - ADF. BFO-OFF switch - BFO. Range  switch  -  Select  frequency range. Audio  control  panel  (fig.  3-l) NAV B switch - On and adjusted. Gain control - As required. TUNE  control  -  Rotate  for  maxi- mum  reading  on  tuning  meter and zero BFO beat. BFO-OFF switch - OFF. Double  needle  switch  (RMI,  fig. 3-9) - ADF. Double  needle  pointer  (RMI,  fig. 3-9) - Read course to station. operate   set   for   sense   antenna Mode   selector   (ADF   control panel, fig. 3-18 - ANT. Range switch   -  Select  operating range. Tune  control  -  Rotate  for  maxi- mum reading on tuning meter. Gain control - As required. operate  set  for  aural-null  direction Mode   selector   (ADF   control panel, fig. 3-18) - ANT. BFO-OFF switch - BFO. Range switch   -  Select  operating range. Tune  control  -  Tune  desired  sta- tion. Gain  control   -  Adjust  for  mini- mum audio output. Double  needle  switches  (RMI,  fig. 3-9) - As required.