diff --git a/FM.cpp b/FM.cpp
index 907ad5e..5bed1f1 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -307,9 +307,27 @@ void CFM::simplexStateMachine(bool validRFSignal, bool validExtSignal)
     case FS_RELAYING_RF:
       relayingRFStateSimplex(validRFSignal);
       break;
+    case FS_RELAYING_WAIT_RF:
+      relayingRFWaitStateSimplex(validRFSignal);
+      break;
+    case FS_TIMEOUT_RF:
+      timeoutRFStateSimplex(validRFSignal);
+      break;
+    case FS_TIMEOUT_WAIT_RF:
+      timeoutRFStateSimplex(validRFSignal);
+      break;
     case FS_RELAYING_EXT:
       relayingExtStateSimplex(validExtSignal);
       break;
+    case FS_RELAYING_WAIT_EXT:
+      relayingExtWaitStateSimplex(validExtSignal);
+      break;
+    case FS_TIMEOUT_EXT:
+      timeoutExtStateSimplex(validExtSignal);
+      break;
+    case FS_TIMEOUT_WAIT_EXT:
+      timeoutExtWaitStateSimplex(validExtSignal);
+      break;
     default:
       break;
   }
@@ -451,12 +469,18 @@ void CFM::listeningStateSimplex(bool validRFSignal, bool validExtSignal)
     io.setDecode(true);
     io.setADCDetection(true);
 
+    m_timeoutTimer.start();
+
     m_statusTimer.start();
     serial.writeFMStatus(m_state);
   } else if (validExtSignal) {
     DEBUG1("State to RELAYING_EXT");
     m_state = FS_RELAYING_EXT;
 
+    insertSilence(50U);
+
+    m_timeoutTimer.start();
+
     m_statusTimer.start();
     serial.writeFMStatus(m_state);
   }
@@ -537,12 +561,22 @@ void CFM::relayingRFStateDuplex(bool validSignal)
 
 void CFM::relayingRFStateSimplex(bool validSignal)
 {
-  if (!validSignal) {
+  if (validSignal) {
+    if (m_timeoutTimer.isRunning() && m_timeoutTimer.hasExpired()) {
+      DEBUG1("State to TIMEOUT_RF");
+      m_state = FS_TIMEOUT_RF;
+
+      m_timeoutTimer.stop();
+
+      if (m_extEnabled)
+        serial.writeFMEOT();
+    }
+  } else {
     io.setDecode(false);
     io.setADCDetection(false);
 
-    DEBUG1("State to LISTENING");
-    m_state = FS_LISTENING;
+    DEBUG1("State to RELAYING_WAIT_RF");
+    m_state = FS_RELAYING_WAIT_RF;
     m_ackDelayTimer.start();
 
     if (m_extEnabled)
@@ -588,6 +622,26 @@ void CFM::relayingRFWaitStateDuplex(bool validSignal)
   }
 }
 
+void CFM::relayingRFWaitStateSimplex(bool validSignal)
+{
+  if (validSignal) {
+    io.setDecode(true);
+    io.setADCDetection(true);
+
+    DEBUG1("State to RELAYING_RF");
+    m_state = FS_RELAYING_RF;
+    m_ackDelayTimer.stop();
+  } else {
+    if (m_ackDelayTimer.isRunning() && m_ackDelayTimer.hasExpired()) {
+      DEBUG1("State to LISTENING");
+      m_state = FS_LISTENING;
+
+      m_ackDelayTimer.stop();
+      m_timeoutTimer.stop();
+    }
+  }
+}
+
 void CFM::kerchunkExtStateDuplex(bool validSignal)
 {
   if (validSignal) {
@@ -645,9 +699,17 @@ void CFM::relayingExtStateDuplex(bool validSignal)
 
 void CFM::relayingExtStateSimplex(bool validSignal)
 {
-  if (!validSignal) {
-    DEBUG1("State to LISTENING");
-    m_state = FS_LISTENING;
+  if (validSignal) {
+    if (m_timeoutTimer.isRunning() && m_timeoutTimer.hasExpired()) {
+      DEBUG1("State to TIMEOUT_EXT");
+      m_state = FS_TIMEOUT_EXT;
+
+      m_timeoutTimer.stop();
+    }
+  } else {
+    DEBUG1("State to RELAYING_WAIT_EXT");
+    m_state = FS_RELAYING_WAIT_EXT;
+    m_ackDelayTimer.start();
   }
 }
 
@@ -686,6 +748,23 @@ void CFM::relayingExtWaitStateDuplex(bool validSignal)
   }
 }
 
+void CFM::relayingExtWaitStateSimplex(bool validSignal)
+{
+  if (validSignal) {
+    DEBUG1("State to RELAYING_EXT");
+    m_state = FS_RELAYING_EXT;
+    m_ackDelayTimer.stop();
+  } else {
+    if (m_ackDelayTimer.isRunning() && m_ackDelayTimer.hasExpired()) {
+      DEBUG1("State to LISTENING");
+      m_state = FS_LISTENING;
+
+      m_ackDelayTimer.stop();
+      m_timeoutTimer.stop();
+    }
+  }
+}
+
 void CFM::hangStateDuplex(bool validRFSignal, bool validExtSignal)
 {
   if (validRFSignal) {
@@ -747,6 +826,19 @@ void CFM::timeoutRFStateDuplex(bool validSignal)
   }
 }
 
+void CFM::timeoutRFStateSimplex(bool validSignal)
+{
+  if (!validSignal) {
+    io.setDecode(false);
+    io.setADCDetection(false);
+
+    DEBUG1("State to TIMEOUT_WAIT_RF");
+    m_state = FS_TIMEOUT_WAIT_RF;
+
+    m_ackDelayTimer.start();
+  }
+}
+
 void CFM::timeoutRFWaitStateDuplex(bool validSignal)
 {
   if (validSignal) {
@@ -776,6 +868,25 @@ void CFM::timeoutRFWaitStateDuplex(bool validSignal)
   }
 }
 
+void CFM::timeoutRFWaitStateSimplex(bool validSignal)
+{
+  if (validSignal) {
+    io.setDecode(true);
+    io.setADCDetection(true);
+
+    DEBUG1("State to TIMEOUT_RF");
+    m_state = FS_TIMEOUT_RF;
+    m_ackDelayTimer.stop();
+  } else {
+    if (m_ackDelayTimer.isRunning() && m_ackDelayTimer.hasExpired()) {
+      DEBUG1("State to LISTENING");
+      m_state = FS_LISTENING;
+      m_ackDelayTimer.stop();
+      m_timeoutTimer.stop();
+    }
+  }
+}
+
 void CFM::timeoutExtStateDuplex(bool validSignal)
 {
   if (!validSignal) {
@@ -790,6 +901,15 @@ void CFM::timeoutExtStateDuplex(bool validSignal)
   }
 }
 
+void CFM::timeoutExtStateSimplex(bool validSignal)
+{
+  if (!validSignal) {
+    DEBUG1("State to TIMEOUT_WAIT_EXT");
+    m_state = FS_TIMEOUT_WAIT_EXT;
+    m_ackDelayTimer.start();
+  }
+}
+
 void CFM::timeoutExtWaitStateDuplex(bool validSignal)
 {
   if (validSignal) {
@@ -815,6 +935,23 @@ void CFM::timeoutExtWaitStateDuplex(bool validSignal)
     m_callsignTimer.start();
   }
 }
+
+void CFM::timeoutExtWaitStateSimplex(bool validSignal)
+{
+  if (validSignal) {
+    DEBUG1("State to TIMEOUT_EXT");
+    m_state = FS_TIMEOUT_EXT;
+    m_ackDelayTimer.stop();
+  } else {
+    if (m_ackDelayTimer.isRunning() && m_ackDelayTimer.hasExpired()) {
+      DEBUG1("State to LISTENING");
+      m_state = FS_LISTENING;
+      m_ackDelayTimer.stop();
+      m_timeoutTimer.stop();
+    }
+  }
+}
+
 void CFM::sendCallsign()
 {
   if (m_holdoffTimer.isRunning()) {
diff --git a/FM.h b/FM.h
index 58ca5a9..8dcaa4a 100644
--- a/FM.h
+++ b/FM.h
@@ -121,7 +121,13 @@ private:
   void simplexStateMachine(bool validRFSignal, bool validExtSignal);
   void listeningStateSimplex(bool validRFSignal, bool validExtSignal);
   void relayingRFStateSimplex(bool validSignal);
+  void relayingRFWaitStateSimplex(bool validSignal);
+  void timeoutRFStateSimplex(bool validSignal);
+  void timeoutRFWaitStateSimplex(bool validSignal);
   void relayingExtStateSimplex(bool validSignal);
+  void relayingExtWaitStateSimplex(bool validSignal);
+  void timeoutExtStateSimplex(bool validSignal);
+  void timeoutExtWaitStateSimplex(bool validSignal);
 
   void clock(uint8_t length);
 
diff --git a/SerialPort.cpp b/SerialPort.cpp
index 70df849..9e657e4 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -109,7 +109,7 @@ const uint8_t MMDVM_DEBUG5       = 0xF5U;
 #define	HW_TYPE	"MMDVM"
 #endif
 
-#define DESCRIPTION "20200701 (D-Star/DMR/System Fusion/P25/NXDN/POCSAG/FM/AX.25)"
+#define DESCRIPTION "20200706 (D-Star/DMR/System Fusion/P25/NXDN/POCSAG/FM/AX.25)"
 
 #if defined(GITVERSION)
 #define concat(h, a, b, c) h " " a " " b " GitID #" c ""