diff --git a/FM.cpp b/FM.cpp
index 9073649..d94c5a4 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -86,10 +86,14 @@ void CFM::samples(q15_t* samples, uint8_t length)
       currentSample = 0U;
 
     if (!m_callsign.isRunning())
-      currentSample += m_rfAck.getAudio();
+      currentSample += m_rfAck.getHighAudio();
     
-    if (!m_rfAck.isRunning())
-      currentSample += m_callsign.getAudio();
+    if (!m_rfAck.isRunning()) {
+      if (m_state == FS_LISTENING)
+        currentSample += m_callsign.getHighAudio();
+      else
+        currentSample += m_callsign.getLowAudio();
+    }
 
     if (!m_callsign.isRunning() && !m_rfAck.isRunning())
       currentSample += m_timeoutTone.getAudio();
@@ -114,7 +118,7 @@ void CFM::reset()
   m_ctcssRX.reset();
 }
 
-uint8_t CFM::setCallsign(const char* callsign, uint8_t speed, uint16_t frequency, uint8_t time, uint8_t holdoff, uint8_t level, bool callsignAtStart, bool callsignAtEnd)
+uint8_t CFM::setCallsign(const char* callsign, uint8_t speed, uint16_t frequency, uint8_t time, uint8_t holdoff, uint8_t highLevel, uint8_t lowLevel, bool callsignAtStart, bool callsignAtEnd)
 {
   m_callsignAtStart = callsignAtStart;
   m_callsignAtEnd   = callsignAtEnd;
@@ -127,7 +131,7 @@ uint8_t CFM::setCallsign(const char* callsign, uint8_t speed, uint16_t frequency
   m_holdoffTimer.setTimeout(holdoffTime, 0U);
   m_callsignTimer.setTimeout(callsignTime, 0U);
 
-  return m_callsign.setParams(callsign, speed, frequency, level);
+  return m_callsign.setParams(callsign, speed, frequency, highLevel, lowLevel);
 }
 
 uint8_t CFM::setAck(const char* rfAck, uint8_t speed, uint16_t frequency, uint8_t minTime, uint16_t delay, uint8_t level)
@@ -135,7 +139,7 @@ uint8_t CFM::setAck(const char* rfAck, uint8_t speed, uint16_t frequency, uint8_
   m_ackDelayTimer.setTimeout(0U, delay);
   m_ackMinTimer.setTimeout(minTime, 0U);
 
-  return m_rfAck.setParams(rfAck, speed, frequency, level);
+  return m_rfAck.setParams(rfAck, speed, frequency, level, level);
 }
 
 uint8_t CFM::setMisc(uint16_t timeout, uint8_t timeoutLevel, uint8_t ctcssFrequency, uint8_t ctcssThreshold, uint8_t ctcssLevel, uint8_t kerchunkTime, uint8_t hangTime)
diff --git a/FM.h b/FM.h
index b348ee9..d2f9419 100644
--- a/FM.h
+++ b/FM.h
@@ -47,7 +47,7 @@ public:
 
   void reset();
 
-  uint8_t setCallsign(const char* callsign, uint8_t speed, uint16_t frequency, uint8_t time, uint8_t holdoff, uint8_t level, bool callsignAtStart, bool callsignAtEnd);
+  uint8_t setCallsign(const char* callsign, uint8_t speed, uint16_t frequency, uint8_t time, uint8_t holdoff, uint8_t highLevel, uint8_t lowLevel, bool callsignAtStart, bool callsignAtEnd);
   uint8_t setAck(const char* rfAck, uint8_t speed, uint16_t frequency, uint8_t minTime, uint16_t delay, uint8_t level);
   uint8_t setMisc(uint16_t timeout, uint8_t timeoutLevel, uint8_t ctcssFrequency, uint8_t ctcssThreshold, uint8_t ctcssLevel, uint8_t kerchunkTime, uint8_t hangTime);
 
diff --git a/FMCTCSSTX.cpp b/FMCTCSSTX.cpp
index 5011ce5..fb5a997 100644
--- a/FMCTCSSTX.cpp
+++ b/FMCTCSSTX.cpp
@@ -115,17 +115,6 @@ uint8_t CFMCTCSSTX::setParams(uint8_t frequency, uint8_t level)
   return 0U;
 }
 
-void CFMCTCSSTX::getAudio(q15_t* samples, uint8_t length)
-{
-  for (uint8_t i = 0U; i < length; i++) {
-    samples[i] += m_values[m_n];
-
-    m_n++;
-    if (m_n >= m_length)
-      m_n = 0U;
-  }
-}
-
 q15_t CFMCTCSSTX::getAudio()
 {
   q15_t sample = m_values[m_n++];
diff --git a/FMCTCSSTX.h b/FMCTCSSTX.h
index a8dfd37..0c3e6e5 100644
--- a/FMCTCSSTX.h
+++ b/FMCTCSSTX.h
@@ -27,7 +27,6 @@ public:
 
   uint8_t setParams(uint8_t frequency, uint8_t level);
 
-  void getAudio(q15_t* samples, uint8_t length);
   q15_t getAudio();
 
 private:
diff --git a/FMKeyer.cpp b/FMKeyer.cpp
index f16ebc0..70beea4 100644
--- a/FMKeyer.cpp
+++ b/FMKeyer.cpp
@@ -84,11 +84,13 @@ m_dotLen(0U),
 m_dotPos(0U),
 m_audio(NULL),
 m_audioLen(0U),
-m_audioPos(0U)
+m_audioPos(0U),
+m_highLevel(0U),
+m_lowLevel(0)
 {
 }
 
-uint8_t CFMKeyer::setParams(const char* text, uint8_t speed, uint16_t frequency, uint8_t level)
+uint8_t CFMKeyer::setParams(const char* text, uint8_t speed, uint16_t frequency, uint8_t highLevel, uint8_t lowLevel)
 {
   for (uint8_t i = 0U; text[i] != '\0'; i++) {
     for (uint8_t j = 0U; SYMBOL_LIST[j].c != 0U; j++) {
@@ -109,58 +111,60 @@ uint8_t CFMKeyer::setParams(const char* text, uint8_t speed, uint16_t frequency,
     }
   }
 
-  q15_t value = q15_t(level * 128);
+  m_highLevel = q15_t(highLevel * 128);
+  m_lowLevel  = q15_t(lowLevel * 128);
 
   m_dotLen = 24000U / speed;   // In samples
 
   m_audioLen = 24000U / frequency; // In samples
 
-  m_audio = new q15_t[m_audioLen];
+  m_audio = new bool[m_audioLen];
 
   for (uint16_t i = 0U; i < m_audioLen; i++) {
     if (i < (m_audioLen / 2U))
-      m_audio[i] = value;
+      m_audio[i] = true;
     else
-      m_audio[i] = -value;
+      m_audio[i] = false;
   }
 
   return 0U;
 }
 
-void CFMKeyer::getAudio(q15_t* samples, uint8_t length)
-{
-  if (!m_wanted)
-    return;
-
-  for (uint8_t i = 0U; i < length; i++) {
-    bool b = READ_BIT(m_poBuffer, m_poPos);
-    if (b)
-      samples[i] += m_audio[m_audioPos];
-
-    m_audioPos++;
-    if (m_audioPos >= m_audioLen)
-      m_audioPos = 0U;
-    m_dotPos++;
-    if (m_dotPos >= m_dotLen) {
-      m_dotPos = 0U;
-      m_poPos++;
-      if (m_poPos >= m_poLen) {
-        stop();
-        return;
-      }
-    }
-  }
-}
-
-q15_t CFMKeyer::getAudio()
+q15_t CFMKeyer::getHighAudio()
 {
   q15_t output = 0U;
   if (!m_wanted)
-    return 0U; 
-    
+    return 0U;
+
   bool b = READ_BIT(m_poBuffer, m_poPos);
   if (b)
-    output = m_audio[m_audioPos];
+    output = m_audio[m_audioPos] ? m_highLevel : -m_highLevel;
+
+  m_audioPos++;
+  if (m_audioPos >= m_audioLen)
+    m_audioPos = 0U;
+  m_dotPos++;
+  if (m_dotPos >= m_dotLen) {
+    m_dotPos = 0U;
+    m_poPos++;
+    if (m_poPos >= m_poLen) {
+      stop();
+      return output;
+    }
+  }
+
+  return output;
+}
+
+q15_t CFMKeyer::getLowAudio()
+{
+  q15_t output = 0U;
+  if (!m_wanted)
+    return 0U;
+
+  bool b = READ_BIT(m_poBuffer, m_poPos);
+  if (b)
+    output = m_audio[m_audioPos] ? m_lowLevel : -m_lowLevel;
 
   m_audioPos++;
   if (m_audioPos >= m_audioLen)
diff --git a/FMKeyer.h b/FMKeyer.h
index 2d85499..799e85c 100644
--- a/FMKeyer.h
+++ b/FMKeyer.h
@@ -25,10 +25,10 @@ class CFMKeyer {
 public:
   CFMKeyer();
 
-  uint8_t setParams(const char* text, uint8_t speed, uint16_t frequency, uint8_t level);
+  uint8_t setParams(const char* text, uint8_t speed, uint16_t frequency, uint8_t highLevel, uint8_t lowLevel);
 
-  void getAudio(q15_t* samples, uint8_t length);
-  q15_t getAudio();
+  q15_t getHighAudio();
+  q15_t getLowAudio();
 
   void start();
   void stop();
@@ -42,9 +42,11 @@ private:
   uint16_t m_poPos;
   uint16_t m_dotLen;
   uint16_t m_dotPos;
-  q15_t*   m_audio;
+  bool*    m_audio;
   uint16_t m_audioLen;
   uint16_t m_audioPos;
+  q15_t    m_highLevel;
+  q15_t    m_lowLevel;
 };
 
 #endif
diff --git a/FMTimeout.cpp b/FMTimeout.cpp
index c64aada..893e53b 100644
--- a/FMTimeout.cpp
+++ b/FMTimeout.cpp
@@ -39,29 +39,6 @@ void CFMTimeout::setParams(uint8_t level)
   m_level = q15_t(level * 128);
 }
 
-void CFMTimeout::getAudio(q15_t* samples, uint8_t length)
-{
-  if (!m_running)
-    return;
-
-  for (uint8_t i = 0U; i < length; i++) {
-    if (m_pos > 12000U) {
-      q31_t sample = BUSY_AUDIO[m_n] * m_level;
-      samples[i] = q15_t(__SSAT((sample >> 15), 16));
-
-      m_n++;
-      if (m_n >= BUSY_AUDIO_LEN)
-        m_n = 0U;
-    } else {
-      samples[i] = 0;
-    }
-
-    m_pos++;
-    if (m_pos >= 24000U)
-      m_pos = 0U;
-  }
-}
-
 q15_t CFMTimeout::getAudio()
 {
   q15_t sample = 0U;
diff --git a/FMTimeout.h b/FMTimeout.h
index 8b8a415..b2f747c 100644
--- a/FMTimeout.h
+++ b/FMTimeout.h
@@ -30,8 +30,6 @@ public:
   void start();
   void stop();
 
-  void getAudio(q15_t* samples, uint8_t length);
-
   q15_t getAudio();
 
 private:
diff --git a/SerialPort.cpp b/SerialPort.cpp
index 0d9be11..121ee68 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -365,25 +365,26 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
 
 uint8_t CSerialPort::setFMParams1(const uint8_t* data, uint8_t length)
 {
-  if (length < 7U)
+  if (length < 8U)
     return 4U;
 
   uint8_t  speed     = data[0U];;
   uint16_t frequency = data[1U] * 10U;
   uint8_t  time      = data[2U];
   uint8_t  holdoff   = data[3U];
-  uint8_t  level     = data[4U];
+  uint8_t  highLevel = data[4U];
+  uint8_t  lowLevel  = data[5U];
 
-  bool callAtStart = (data[5U] & 0x01U) == 0x01U;
-  bool callAtEnd   = (data[5U] & 0x02U) == 0x02U;
+  bool callAtStart = (data[6U] & 0x01U) == 0x01U;
+  bool callAtEnd   = (data[6U] & 0x02U) == 0x02U;
 
   char callsign[50U];
   uint8_t n = 0U;
-  for (uint8_t i = 6U; i < length; i++, n++)
+  for (uint8_t i = 7U; i < length; i++, n++)
     callsign[n] = data[i];
   callsign[n] = '\0';
 
-  return fm.setCallsign(callsign, speed, frequency, time, holdoff, level, callAtStart, callAtEnd);
+  return fm.setCallsign(callsign, speed, frequency, time, holdoff, highLevel, lowLevel, callAtStart, callAtEnd);
 }
 
 uint8_t CSerialPort::setFMParams2(const uint8_t* data, uint8_t length)