diff --git a/src/beeper.h b/src/beeper.h
index 310b316d9..b609a70a6 100644
--- a/src/beeper.h
+++ b/src/beeper.h
@@ -62,6 +62,7 @@ extern void beep(uint8_t val);
 #define AUDIO_MENUS()         beep(0)
 #define AUDIO_WARNING2()      beep(2)
 #define AUDIO_WARNING1()      beep(3)
+#define AUDIO_TX_BATTERY_LOW() beep(4)
 #define AUDIO_ERROR()         beep(4)
 #define AUDIO_TIMER_30()      { beepAgain=2; beep(2); }
 #define AUDIO_TIMER_20()      { beepAgain=1; beep(2); }
diff --git a/src/ersky9x/audio.h b/src/ersky9x/audio.h
index dd604ed8d..8f4b9406c 100644
--- a/src/ersky9x/audio.h
+++ b/src/ersky9x/audio.h
@@ -83,6 +83,7 @@ void audioEvent(uint8_t e, uint8_t f=BEEP_DEFAULT_FREQ);
 #define AUDIO_MENUS()       audioEvent(AU_MENUS)
 #define AUDIO_WARNING1()    audioEvent(AU_WARNING1)
 #define AUDIO_WARNING2()    audioEvent(AU_WARNING2)
+#define AUDIO_TX_BATTERY_LOW() audioEvent(AU_TX_BATTERY_LOW)
 #define AUDIO_ERROR()       audioEvent(AU_ERROR)
 #define AUDIO_TIMER_30()    audioEvent(AU_TIMER_30)
 #define AUDIO_TIMER_20()    audioEvent(AU_TIMER_20)
diff --git a/src/open9x.cpp b/src/open9x.cpp
index 24c8f8fad..0be86f308 100644
--- a/src/open9x.cpp
+++ b/src/open9x.cpp
@@ -2444,7 +2444,7 @@ void perMain()
           g_vbat100mV = s_batSum / 8;
           s_batSum = 0;
           if (g_vbat100mV<g_eeGeneral.vBatWarn && g_vbat100mV>50) {
-            AUDIO_ERROR(); // TODO AUDIO_TX_BATTERY_LOW()
+            AUDIO_TX_BATTERY_LOW();
           }
         }
 #if !defined(PCBARM)
diff --git a/src/open9x.h b/src/open9x.h
index f1cc1ed3a..e6a59be91 100644
--- a/src/open9x.h
+++ b/src/open9x.h
@@ -918,6 +918,7 @@ enum AUDIO_SOUNDS {
 
 #if defined(PCBV4)
 #include "rtc.h"
+extern uint8_t g_ms100; // global to allow time set function to reset to zero
 #endif
 
 // Re-useable byte array to save having multiple buffers
diff --git a/src/stock/audio.h b/src/stock/audio.h
index 135994b3b..79797413b 100644
--- a/src/stock/audio.h
+++ b/src/stock/audio.h
@@ -116,6 +116,7 @@ void audioDefevent(uint8_t e);
 #define AUDIO_MENUS()       audioDefevent(AU_MENUS)
 #define AUDIO_WARNING1()    audioDefevent(AU_WARNING1)
 #define AUDIO_WARNING2()    audioDefevent(AU_WARNING2)
+#define AUDIO_TX_BATTERY_LOW() audioDefevent(AU_TX_BATTERY_LOW)
 #define AUDIO_ERROR()       audioDefevent(AU_ERROR)
 #define AUDIO_TIMER_30()    audioDefevent(AU_TIMER_30)
 #define AUDIO_TIMER_20()    audioDefevent(AU_TIMER_20)