MODE KNOB 
The sixteen-position knob on top of the APX portable radio is 
called the mode knob or “selector.”  It primarily functions to 
change back-and-forth between talk-groups within a 
particular zone.    
The white line running down the side of the mode knob tells 
you what particular number the knob is currently set to; the 
knob will click as you rotate it.  
Immediately underneath of the mode knob is the encryption 
on/off switch (see inset).  This switch is not programmed in 
the FC/CoMIRS radios as this is done in the Zone and talk-
group selection in those radios that are programmed with 
encryption capabilities. 
LED INDICATOR: 
Next to the mode knob is a small LED indicator.  This LED has three colors: red, 
green, and yellow. The LED indicator is     typically not illuminated.
COLOR  MEANING 
Solid Red  Radio is transmitting 
Blinking Red 
Burst transmission/data or low battery 
(constant) 
Blinking Yellow  Radio is receiving an encrypted transmission 
Solid Green  Radio is powering up 
Blinking Green  Radio is receiving a private call or page 
MODE KNOB