TM 55-1510-220-10 b. Controls/Indicators and Functions. (1)      Frequency   indicator.      Indicates   set   operating frequency. (2)  Control frequency indicators.  Indicates frequency selected (left or right active). (3)      COMM   TEST   switch.      Overrides   automatic squelch circuit. (4)    Frequency  selectors.    Select  desired  set  operating frequency. (5)    TRANS  switch.    Selects  right  or  left  frequency control selectors. (6)    VOL-OFF  control.    Adjusts  volume  of  received audio, turns set ON or OFF. c. VHF-AM Set - Normal Operation. (1)        Turn-on    procedure:    Volume    control    -    Turn clockwise (ON). (2)  Receiver operating procedure: 1. Transmitter-interphone selector switch (audio control  panel,  fig.  3-1)  -  No.1  position,  or radio monitor control No.1 - ON. 2. Frequency selector - Set desired frequency. 3. Volume control - As required. (3)  Transmitter operating procedure: 1. Transmitter-interphone selector switch (audio control panel, fig. 3-1) - No.1 position. 2. Microphone switch - Press. (4)      Shutdown   procedure:   Volume   control   -   Turn counterclockwise (OFF). d. VHF-AM Set Emergency Operation. NOTE Transmission   on   emergency   frequency (121.500 MHz) is restricted to emergencies only.  Emergency frequency 243.000   MHz   (guard   channel)   is   also available on the UHF command radio. 1. Transmitter-interphone selector switch (audio control panel, fig. 3-1) - No.1 position. 2. Frequency selector (VHF control panel, fig. 3- 4) - 121.500 MHz (emergency frequency). 3. Microphone switch - Press. 3-12.  VHF AM-FM COMMAND SET (AN/ARC-186). a. Description.      The   VHF   AM-FM   Command   Set provides for normal and secure 2-way AM voice communication  in  the  very  high  frequency  range  of  116.000 to  151.975  MHz  and  FM  homing  in  the  30.000  to  87.975 MHz  band.    Twenty  channels  may  be  preset.    Audio  signals are   applied   through   the   No.2   position   of   the   transmitter- interphone  selector  switches  and  through  the  No.2  receiver audio   switches   on   the   pilot's   and   copilot's   audio   control panels (fig. 3-1).  Complete provisions only are installed for a TSEC/KY-58 voice security device.  Circuits are protected by a  10-ampere  VHF  AM-FM  circuit  breaker  on  the  overhead circuit  breaker  panel  (fig.  2-27).    Figure  3-5  illustrates  the VHF   AM-FM   control   panel.      The   associated   antenna   is shown in figure 2-1. 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)    1.0  MHz  indicator.    Indicates  manually  selected receiver-transmitter frequency in 1.0 MHz increments. (5)    0.1  MHz  selector.    Selects  receiver-transmitter frequency   in   0.1   MHz   increments.      Clockwise   rotation increases frequency. (6)    0.1  MHz  indicator.    Indicates  manually  selected receiver-transmitter frequency in 0.1 MHz increments. 3-10