TM 55-1510-222-10 System circuits are protected by the UHF, VHF FM and BU VOW circuit breakers in the overhead circuit breaker panel (fig.  2-6). b. Controls/Indicators and Functions. (1) POWER ON switch.    Turns  set  on  or off. NOTE The   power   switch   must   be   in   ON position   for   FM   or   secure   mission operations in either the plain or cipher mode. (2) PLAIN-CIPHER.    Selects  unciphered or ciphered communications on FM set. (a) PLAIN.        Enables    unciphered communications on FM set. (b) CIPHER.        Enables     ciphered communications on FM set. (3) ZEROIZE    switch.        Normally    OFF. Place   in   ON   position   during   emergency   situations   to neutralize  and  make  inoperative  the  associated  cipher equipment. Illuminates    when    PLAIN-CIPHER    switch    is    in CIPHER position. c. VHF FM Set and Voice Security Operation. (1) Turn-on procedure:  Lower switch ON. NOTE The   power   switch   must   be   in   ON position, regardless of the mode of the operation, whenever the voice security (CIPHONY)   KY-58   is   installed   in   the aircraft. (2) Receiver operating procedure: 1. Squelch control As required. 2. Transmitter-interphone   selector switch  No.    2  position,  or  radio  monitor  control  No.    2 ON. 3. FM/AM select switch FM. 4. Mode selector switch TR. 5. Frequency selectors As required. 6. Plain-cipher switch As required. NOTE The   power   switch   must   be   in   ON position, regardless of the mode of the operation, whenever the voice security (CIPHONY)   KY-58   is   installed   in   the aircraft. (3) Transmitter operating procedure (PLAIN): 1. Transmitter-interphone   selector switch No.  2 position. 2. FM/AM select switch FM. 3. Plain-cipher switch PLAIN. 4. Microphone switch Press. (4) Transmitter operating procedure (CIPHER): 1. Transmitter-interphone   selector No.  2 position. 2. FM/AM select switch FM. 3. Microphone switch Press momentarily  (interrupted  tone  from  voice  security  unit should no longer be heard.  ) NOTE No     traffic     will     be     passed     if     the interrupted   tone   is   still   heard   after pressing and releasing the microphone switch. 4. Microphone    switch    Press    (do not  talk).    Wait  until  beep  is  heard,  then  speak  into microphone. (5) Shutdown procedure: 1. Mode selector switch OFF. 2. Power switch OFF. 3-9. BACK-UP   VOICE   ORDER    WIRE    (BU    VOW) (AN/ARC-164). A  radio  set  identical  in  type  and  performance  to the   UHF   command   set   (fig.      3-2)   is   located   in   the pedestal, to serve as voice order wire.  This set provides the pilot and copilot with secure 2-way voice communications. Complete provisions only are provided for a KY-58 voice security device.  The voice order   wire   set   is   protected   by   the   7   1/2-ampere   BU VOW   circuit   breaker   in   the   overhead   circuit   breaker panel   (fig.      2-6).      The   voice   order   wire   shares   an antenna    mounted    on    the    aircraft    belly,    with    the transponder (fig.  2-1). 3-7