TM 55-1510-221-10 b. Controls/Indicators and Functions. (1.)  10  MHz  selector.  Selects   receiver- transmitter  frequency  in  increments  of  10  MHz from  30  to  150  MHz.  Clockwise  rotation  increases frequency. (2.) 10 MHz indicator. Indicates  manually selected  receiver-transmitter  frequency  in  10  MHz increments from 30 to 150 MHz. (3.)  1.0  MHz  selector.  Selects   receiver- transmitter  frequency  in  1.0  MHz  increments. Clockwise  rotation  increases  frequency. (4.)  I.0  MHz  indicator.  Indicates   manu- ally  selected  receiver-transmitter  frequency  in  1.0 MHz  increments. (5.)  0.1  MHz  indicator.  Indicates   manu- ally  selected  receiver-transmitter  frequency  in  0.1 MHz  increments. (6.)  0.1  MHz  selector.  Selects   receiver- transmitter  frequency  in  0.1  MHz  increments. Clockwise  rotation  increases  frequency. (7.) 0.025  MHz  indicator.  Indicates  manu- ally  selected  receiver-transmitter  frequency  in  0.025 MHz   increments, (8.)  0.025  MHz  selector.  Selects   receiver- transmitter  frequency  in  0.025  MHz  increments. Clockwise  rotation  increases  frequency. (9.)   Preset   CHAN   indicator.  Indicates selected  preset  channel. (10.)  Preset  CHAN  selector.  Selects   preset channel from 1 to 20. Clockwise rotation increases number  selected. (11.) Preset channels freq. list.  Writing  area to keep track of preset channels, (12.)  LOCKOUT  FM-AM  switch.  Screw- driver   adjustable   three-position   switch.   Warning tone announces lockout. (a.) Center. Selects AM or FM band. (b.) AM. Shuts off AM band. (c.) FM. Shuts off FM band. (13.)  FM  SQUELCH  control.  Screwdriver adjustable potentiometer. Squelch fully overdriven at full counterclockwise position. Clockwise rotation increases input signal required to open squelch. (14.)  WB-NB-MEM  LOAD  switch.  Three- position   switch. (a.) NB. Limits  selectivity  to  narrow- band  intermediate  frequency. (b.)  WB.  Limits   selectivity   to   wide- band intermediate frequency of FM band. ( c . )   M E M   L O A D. Momentary switch.  If  pressed,  loads  manually  selected  frequency in preset channel memory. (15.)  AM  SQUELCH  control.  Screwdriver adjustable potentiometer. Squelch fully overridden at  full  counterclockwise  position.  Clockwise  rotation increases input signal required to open squelch. (16.)  Mode  selector  switch.  Three-position rotary  switch. (a.)    OFF.    Shuts off receiver- transmitter. modes. (b.)  TR.  Selects   transmit/receive (c.)  DF.  Not  operational. (I  7.)  SQ-DIS-TONE  select  switch.  Three- position switch. tion. (a.) Center. Selects  squelch  function. (b.)  SQ-DIS.  Shuts  off  squelch  func- (c.)  TONE.  T r a n s m i t s   t o n e   of approximately 1000 Hz. (18.)   Frequency   control/emergency   select switch. Three-position   switch. selection. (a.)  PRE.  Enables  preset  channel selection. (b.) MAN. Enables  manual  frequency (c.)   EMER-AM-FM.   Selects   a   pre- stored  guard  channel. (19.)  VOL  control.  Clockwise   rotation increases  volume. c.  Normal  Operation. (1.)   Turn-on   procedure:   Mode   selector switch  (VHF  AM-FM  control  panel,  fig.  3-5)  -TR. (2.) Receiver  operating  procedure: 1. Frequency   control   emergency selector switch (fig. 3-5) -MAN or PRE,  as  desired. 2.   Transmitter-interphone   selector switch  (audio  control  panel,  fig. 3-11