TM  55-1510-221-10 NOTE It is presumed the AVIONICS MASTER POWER switch is ON, and that normally used avionics circuit breakers remain set. The circuit breakers of routinely used avi- onic systems are normally left set. (2.)  Receiver  operating  procedure: 1. Receiver   audio   switches   (audio control panel) - As required. 2.  Master  volume  control  (audio control  panel)  -  Do  not  use.  (Ad- just  volume  control  of  system being used.) NOTE Audio  select  switches  and  volume  con- trols are routinely left in positions of nor- mal use. 3.  Move  each  receiver  audio  switch ON then OFF, separately, to ver- ify audio presence in headphones for  each  system.  Adjust  volume. (3.)  Transmitter  operating  procedure: 1. Transmitter-interphone selector switch (audio control panel) - Set for  transceiver  desired. 2.  Microphone  jack  selector  switch (instrument panel, fig. 2-29) - As desired. 3.  Control  wheel  microphone  switch (control  wheel)  -  XMIT. 4.   Microphone   switch   (floorboard)   - Depress  to  transmit. (4.)   Intercommunication   procedure: 1.   Transmitter-interphone selector switch  (audio  control  panel)  -  ICS. 2.  Microphone  jack  selector  switch (instrument panel, fig. 2-29) - As desired. 3.   ICS   select   switch   (audio   control panel,   fig.   3-1)   -   As   desired (NORM-HOT  MIC-ICS  OFF). 4.  If  HOT  MIC  is  selected  -  Talk when  ready. 5. If  NORM  microphone  is  selected - Depress microphone switch and transmit. 6.  If  ICS  OFF  is  selected  intercom function is switched off. 7.  Volume  control  (selected  trans- ceiver) - Set for comfort. d.  Emergency  Operation.  Not  applicable. e.  Shutdown  Procedure. 1. AVIONICS  MASTER  POWER switch  (overhead  control  panel, fig. 2-12) - OFF. 2.  Leave  controls  and  circuit  break- ers  positioned  for  normal  opera- tion. 3-7.   MARKER   BEACON   AUDIO   CONTROL PANEL (FIG. 3-2). a. Description. The marker beacon audio con- trol  panel,  located  on  the  pedestal  extension  (fig. 2-7) allows the pilot or copilot to control the volume of the marker beacon (MKR BCN). It also has con- trols for the selection of ADF voice or range filters and MKR BCN HI-LO sensitivity. b.  Controls  and  Functions. (1.) ADF Filter Switches. Controls   selected ADF filter. (a.)  FILTER  V-OFF  switch.  Selects filter to block voice transmissions from ADF ground station. (b.)  FILTER  R-OFF  switch.  Selects filter  to  block  range  transmissions  from  ADF  ground station. (2.)  MKR  BCN  volume  control.  Adjusts volume of marker beacon radio signals received. (3.) MKR BCN HI-LO switch. Selects sen- sitivity of marker beacon receiver. 3-8. UHF COMMAND SET (AN/ARC-184). a.   Description.   The  UHF  command  set  is  a line-of-sight radio transceiver which provides trans- mission  and  reception  of  amplitude  modulated (AM)  signals  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  monitoring  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. 3-4