TM  55-1510-221-10 2. Plain/cipher  switch  (voice  security control panel) -PLAIN. 3. Microphone switch - Press. (4.)  Transmitter  operating  procedure  (CI- PHER): 1. Transmitter-interphone selector switch  (audio  control  panel)  - No.3 position. 2. Plain/cipher  switch  (voice  security control panel, fig. 3-6) - CIPHER. (CIPHER indicator will be illumi- nated  as  long  as  switch  is  in CIPHER position.) 3.  RE-X/REG  switch  (voice  security control panel) - REG. 4.  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. 5. Microphone  switch  -  Press  (do  not talk).  Wait  until  beep  is  heard then speak into microphone. (5.)  Shutdown  procedure: 1. Function   selector   switch   (UHF control panel)- OFF. 2. Power switch (Voice security con- trol panel) - OFF. tion: e. UHF  Command  Set  -  Emergency  Opera- NOTE Transmission  on  emergency  frequencies (guard  channels)  is  restricted  to  emergen- cies  only.  An  emergency  frequency  of  121. 500  MHz  is  also  available  on  the  VHF command radio set. 1.  Transmitter-interphone  selector  switch (audio  control  panel)  -  No.3  position. 2.   Mode   selector   switch   (UHF   control panel)  -  GUARD. 3.  Microphone  switch  -  Press. 3-8A. UHF COMMAND SET (AN/ARC-164). a.  Description.  The UHF command set is a line- of-sight radio transceiver which provides transmis- sion  and  reception  of  amplitude  modulated  (AM)  sig- nals in the ultra high frequency range of 225.000 to 399.975 MHz for a distance range of approximately 50  miles.  Channel  selection  is  spaced  at  0.025  MHz. A  separate  receiver  is  incorporated  to  provide  moni- toring capability for the UHF guard frequency (243.0 MHz).  UHF  audio  output  is  applied  to  the  audio panel where it is routed to the headsets. NOTE The PRESET channel selector and manual frequency selectors are inoperative when the mode selector is set to GUARD posi- tion. The receiver-transmitter will be set to  the  emergency  frequency  only. Existing capabilities of the HAVE QUICK modi- tied radio are preserved to the maximum extent pos- sible when it is operated in the normal (non-hopping) mode. No new procedures are required for normal radio  operation. To operate in the AJ mode, the radio must first be initialized.  This  initialization  requires  the  setting  of two  control  entries  into  the  radio,  Word-of-Day (WOD) and Time-of-Day (TOD). The WOD defines the choice of frequency hopping pattern for the day. The WOD choice is a managerial function and the same WOD may be used for one or more days. The TOD  must  be  loaded  into  the  clock  contained  within the radio. The  transmitter  and  receiver  sections  of  the  UHF unit  operate  independently,  but  share  the  same power supply and frequency control circuits. Sepa- rate cables, route transmit and receive signals to their respective  receiver/transmitter. The UHF command set is protected by the 7 1/2- ampere UHF circuit breaker in the overhead circuit breaker  panel  (fig.  2-6).  Figure  3-2  illustrates  the UHF  command  set.  The  associated  blade  type antenna is shown in figure 2-1. b. Controls and Functions. UHF control panel (fig.  3-2): (1)   Manual   frequency   selector/indicator (hundreds). Selects and indicates hundreds digit of frequency (2 or 3) in MHz. 3-8 Change 4