TM 55-1510-219-10 2.  VOL control (UHF panel) - Mid position. (3)  To use preset frequency (UHF panel). 1.  Mode  selector - PRESET  position. 2.    PRESET  channel  selector  -  Rotate  to channel desired. (4)  To use non-preset frequency (UHF panel). 1.  Mode selector - MANUAL  position. 2.  Manual frequency selectors (5) - Rotate each    knob    to    set    desired    frequency digits. NOTE The PRESET channel selector and manual   frequency   selectors   are inoperative when the mode selector is set to GUARD position. (5)  Volume - Adjust. NOTE To  adjust  volume  when  audio  is not  being  received,  turn  squelch switch    OFF,    adjust    volume    for comfortable noise level, then turn squelch switch ON. (6)  Squelch - As desired. (7)  Transmit. 1.    Transmitter-interphone      selector  (audio panel) - 3 position. 2.    UHF    panel  -  Set  required  frequency using   either   preset   channel   control   or manual frequency select controls. 3.  MIC  HEADSET/OXYGEN   MASK   switch (instrument panel) -As desired. 4.  MIC switch - Depress to transmit. (8)  Shutdown. 1.  Function selector (UHF panel) - OFF. d.    UHF  Command  and  Voice  Security  Operation (KY-28). NOTE Disregard    operating    procedures involving the voice security (CIPHONY) control-indicator, if unit is not installed. (1)  Turn-on. 1.      POWER   ON   switch   (Voice   Security panel, fig 3-6) -ON. 2.  Function switch (UHF panel) - BOTH. (2)  Receive (UHF panel). 1.  Mode selector - As required. 2.      Transmitter-interphone   selector   (audio panel, fig.  3-1) - #3 position.  or Audio monitor control #3 - ON. 3.      Set   required   frequency   using   preset channel   control   or   manual   frequency selector. 4.  Adjust volume. NOTE To  adjust  volume  when  radio  is not being received, turn SQUELCH     switch     OFF,     adjust volume     for     comfortable     noise level,   then   turn   squelch   disable switch ON. 5.  Squelch - As required. (3)  Transmit (PLAIN). 1.        Transmit-interphone    selector    (audio panel) - No.  3 position. 2.    PLAIN/CIPHER  switch  (Voice  Security panel) - PLAIN. 3.  Microphone switch - Press. (4) Transmit (CIPHER). 1.        Transmit-interphone    selector    (audio panel) - No.  3 position. 2.      PLAIN/CIPHER   switch   (Voice   security panel) -CIPHER.  (CIPHER indicator will be  on  as  long  as  switch  is  in  CIPHER position.) 3.  RE-X/REG switch (Voice security panel) - REG. 3-7