diff --git a/SerialPort.cpp b/SerialPort.cpp
index e6ec9d2..9aa0954 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -228,7 +228,7 @@ void CSerialPort::getVersion()
 
 uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
 {
-  if (length < 16U)
+  if (length < 17U)
     return 4U;
 
   bool rxInvert  = (data[0U] & 0x01U) == 0x01U;
@@ -283,6 +283,8 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
 
   uint8_t nxdnTXLevel  = data[15U];
 
+  uint8_t ysfTXHang    = data[16U];
+
   m_modemState  = modemState;
 
   m_dstarEnable = dstarEnable;
@@ -304,7 +306,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint8_t length)
   dmrDMORX.setColorCode(colorCode);
   dmrIdleRX.setColorCode(colorCode);
 
-  ysfTX.setLoDev(ysfLoDev);
+  ysfTX.setParams(ysfLoDev, ysfTXHang);
 
   io.setParameters(rxInvert, txInvert, pttInvert, rxLevel, cwIdTXLevel, dstarTXLevel, dmrTXLevel, ysfTXLevel, p25TXLevel, nxdnTXLevel, txDCOffset, rxDCOffset);
 
diff --git a/YSFTX.cpp b/YSFTX.cpp
index 65ee21a..5790334 100644
--- a/YSFTX.cpp
+++ b/YSFTX.cpp
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2018 by Jonathan Naylor G4KLX
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
  *
  *   This program is free software; you can redistribute it and/or modify
@@ -41,6 +41,7 @@ const q15_t YSF_LEVELD_LO = -948;
 
 const uint8_t YSF_START_SYNC = 0x77U;
 const uint8_t YSF_END_SYNC   = 0xFFU;
+const uint8_t YSF_HANG       = 0x00U;
 
 CYSFTX::CYSFTX() :
 m_buffer(4000U),
@@ -50,7 +51,9 @@ m_poBuffer(),
 m_poLen(0U),
 m_poPtr(0U),
 m_txDelay(240U),      // 200ms
-m_loDev(false)
+m_loDev(false),
+m_txHang(4800U),      // 4s
+m_txCount(0U)
 {
   ::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
 
@@ -60,12 +63,14 @@ m_loDev(false)
   m_modFilter.pState      = m_modState;
 }
 
+
 void CYSFTX::process()
 {
-  if (m_buffer.getData() == 0U && m_poLen == 0U)
+  if (m_buffer.getData() == 0U && m_poLen == 0U && m_txCount == 0U)
     return;
 
-  if (m_poLen == 0U) {
+  // If we have YSF data to transmit, do so.
+  if (m_poLen == 0U && m_buffer.getData() > 0U) {
     if (!m_tx) {
       for (uint16_t i = 0U; i < m_txDelay; i++)
         m_poBuffer[m_poLen++] = YSF_START_SYNC;
@@ -80,20 +85,37 @@ void CYSFTX::process()
   }
 
   if (m_poLen > 0U) {
+    // Transmit YSF data.
     uint16_t space = io.getSpace();
-    
+
     while (space > (4U * YSF_RADIO_SYMBOL_LENGTH)) {
       uint8_t c = m_poBuffer[m_poPtr++];
       writeByte(c);
 
+      // Reduce space and reset the hang timer.
       space -= 4U * YSF_RADIO_SYMBOL_LENGTH;
-      
+      if (m_duplex)
+        m_txCount = m_txHang;
+
       if (m_poPtr >= m_poLen) {
         m_poPtr = 0U;
         m_poLen = 0U;
         return;
       }
     }
+  } else if (m_txCount > 0U) {
+    // Transmit silence until the hang timer has expired.
+    uint16_t space = io.getSpace();
+
+    while (space > (4U * YSF_RADIO_SYMBOL_LENGTH)) {
+      writeSilence();
+
+      space -= 4U * YSF_RADIO_SYMBOL_LENGTH;
+      m_txCount--;
+
+      if (m_txCount == 0U)
+        return;
+    }
   }
 }
 
@@ -141,6 +163,16 @@ void CYSFTX::writeByte(uint8_t c)
   io.write(STATE_YSF, outBuffer, YSF_RADIO_SYMBOL_LENGTH * 4U);
 }
 
+void CYSFTX::writeSilence()
+{
+  q15_t inBuffer[4U] = {0x00U, 0x00U, 0x00U, 0x00U};
+  q15_t outBuffer[YSF_RADIO_SYMBOL_LENGTH * 4U];
+
+  ::arm_fir_interpolate_q15(&m_modFilter, inBuffer, outBuffer, 4U);
+
+  io.write(STATE_YSF, outBuffer, YSF_RADIO_SYMBOL_LENGTH * 4U);
+}
+
 void CYSFTX::setTXDelay(uint8_t delay)
 {
   m_txDelay = 600U + uint16_t(delay) * 12U;        // 500ms + tx delay
@@ -154,8 +186,9 @@ uint8_t CYSFTX::getSpace() const
   return m_buffer.getSpace() / YSF_FRAME_LENGTH_BYTES;
 }
 
-void CYSFTX::setLoDev(bool on)
+void CYSFTX::setParams(bool on, uint8_t txHang)
 {
-  m_loDev = on;
+  m_loDev  = on;
+  m_txHang = txHang * 1200U;
 }
 
diff --git a/YSFTX.h b/YSFTX.h
index 01211a5..647767c 100644
--- a/YSFTX.h
+++ b/YSFTX.h
@@ -35,7 +35,7 @@ public:
 
   uint8_t getSpace() const;
 
-  void setLoDev(bool on);
+  void setParams(bool on, uint8_t txHang);
 
 private:
   CSerialRB                        m_buffer;
@@ -46,8 +46,11 @@ private:
   uint16_t                         m_poPtr;
   uint16_t                         m_txDelay;
   bool                             m_loDev;
+  uint32_t                         m_txHang;
+  uint32_t                         m_txCount;
 
   void writeByte(uint8_t c);
+  void writeSilence();
 };
 
 #endif