   }
   
   // check AOA value and set tone and pauses between tones according to 
-  if(AOA >= 90) {
-    // play 20 pps 1600hz tone
+  if(AOA >= HIGH_TONE_AOA_STALL) {
+    // play 20 pps HIGH tone
     highTone = true;
-    setPPSTone(20);
+    setPPSTone(HIGH_TONE_STALL_PPS);
     toneMode = PULSE_TONE;
-  } else if(AOA >= 70) {
-    // play 1600hz tone at Pulse Rate 1.5 PPS to 6.2 PPS (depending on AOA value)
+  } else if(AOA >= HIGH_TONE_AOA_START) {
+    // play HIGH tone at Pulse Rate 1.5 PPS to 6.2 PPS (depending on AOA value)
     highTone = true;
     OldValue = AOA-69;
     toneMode = PULSE_TONE;

// This is useful because if your on the ground you don't need a beeping in your ear.
#define MUTE_AUDIO_UNDER_IAS  5

// dynon expected string length
#define DYNON_SERIAL_LEN      53

// Tone Pulse Per Sec (PPS) for high and low tones.
#define HIGH_TONE_PPS_MAX     6.5
#define HIGH_TONE_PPS_MIN     1.5
#define LOW_TONE_PPS_MAX      8.5
#define LOW_TONE_PPS_MIN      1.5

#define TONE_PIN          2     // TIOA0
#define PIN_LED1          13    // internal LED for showing AOA status.
#define PIN_LED2          54    // aka A0. external LED for showing serial input.
#define TONE1600hz        1600 
#define TONE400hz         400
#define PULSE_TONE        1
#define SOLID_TONE        2
#define TONE_OFF          3

uint8_t toneState = false;
unsigned char toneMode = PULSE_TONE;  // current mode of tone.  PULSE_TONE, SOLID_TONE, or TONE_OFF

     digitalWrite(PIN_LED1, digitalRead(PIN_LED1)^1);  // cycle led on/off
     //sprintf(tempBuf, "handler() AOA:%i ASI:%i tone: %i PPS:%f handlerFreq: %i",AOA,ASI,toneFreq,pps, handlerFreq);
     //Serial.println(tempBuf);
     if(highTone) {
// check if we want 2 different tones for the high tone mode.      
#ifdef HIGH_TONE2_HZ
        Tone2FlipFlop = Tone2FlipFlop ^ 1; 
        if(Tone2FlipFlop)
          setFrequencytone(HIGH_TONE_HZ);
        else
          setFrequencytone(HIGH_TONE2_HZ);
#else
        setFrequencytone(HIGH_TONE_HZ);
#endif
     } else {
        setFrequencytone(LOW_TONE_HZ);
     }

  } else {
    setFrequencytone(0);
  }
}

void checkAOA() {
  if(ASI <= MUTE_AUDIO_UNDER_IAS) {
#ifdef SHOW_SERIAL_DEBUG    
  // show audio muted and debug info.
