diff --git a/DStarControl.cpp b/DStarControl.cpp
index 28cb4eb..e0c0533 100644
--- a/DStarControl.cpp
+++ b/DStarControl.cpp
@@ -85,7 +85,13 @@ m_minRSSI(0U),
 m_aveRSSI(0U),
 m_rssiCount(0U),
 m_enabled(true),
-m_fp(nullptr)
+m_fp(nullptr),
+m_RFdataLookBack(nullptr),
+m_RFdataLookBackLen(0U),
+m_RFdataLookBackIndex(0U),
+m_NetdataLookBack(nullptr),
+m_NetdataLookBackLen(0U),
+m_NetdataLookBackIndex(0U)
 {
 	assert(display != nullptr);
 	assert(rssiMapper != nullptr);
@@ -100,7 +106,7 @@ m_fp(nullptr)
 	std::string mod = module;
 	mod.resize(1U, ' ');
 	call.append(mod);
-	
+
 	std::string gate = callsign;
 	gate.resize(DSTAR_LONG_CALLSIGN_LENGTH - 1U, ' ');
 	gate.append("G");
@@ -269,6 +275,7 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 
 		m_rfFrames = 1U;
 		m_rfN = 0U;
+		m_RFdataLookBackIndex = 0U;
 
 		m_minRSSI = m_rssi;
 		m_maxRSSI = m_rssi;
@@ -350,6 +357,41 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 		if (m_rfState == RPT_RF_STATE::INVALID)
 			return true;
 
+		// The sync is regenerated by the modem so can do exact match
+		if (::memcmp(data + 1U + DSTAR_VOICE_FRAME_LENGTH_BYTES, DSTAR_SYNC_BYTES, DSTAR_DATA_FRAME_LENGTH_BYTES) == 0) {
+			m_rfSlowData.start();
+			m_rfN = 0U;
+		} else {
+			m_rfSlowData.add(data + 1U);
+		}
+
+		if(m_RFdataLookBackIndex == 0U) {
+			m_RFdataLookBack = new unsigned char[len];
+			::memcpy(m_RFdataLookBack, data, len);
+			m_RFdataLookBackLen = len;
+			m_RFdataLookBackIndex ++;
+			return true;
+		} else if (m_RFdataLookBackIndex == 1U) {
+			m_RFdataLookBackIndex ++;
+
+			if (m_rfState == RPT_RF_STATE::AUDIO){
+				unsigned char type = m_rfSlowData.getType(false);
+				// as per specs chapter 6.1.3, this could be any value bewtween 0x81 and 0x9C as one fast data block can only contain 28 bytes 0x80 + 28d = 0x9C 
+				if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA){
+					LogMessage("D-Star, starting fast data mode (RF)");
+					m_rfState = RPT_RF_STATE::DATA;
+				}
+			}
+
+			LogDebug("D-Star, processing lookback data (RF)");
+			bool res1 = writeModem(m_RFdataLookBack, m_RFdataLookBackLen);
+			bool res2 = writeModem(data, len);
+			delete[] m_RFdataLookBack;
+			m_RFdataLookBack = nullptr;
+			m_RFdataLookBackLen = 0U;
+			return res1 && res2;
+		}
+
 		if (m_rfState == RPT_RF_STATE::LISTENING) {
 			// The sync is regenerated by the modem so can do exact match
 			if (::memcmp(data + 1U + DSTAR_VOICE_FRAME_LENGTH_BYTES, DSTAR_SYNC_BYTES, DSTAR_DATA_FRAME_LENGTH_BYTES) == 0) {
@@ -369,20 +411,29 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 		}
 
 		if (m_rfState == RPT_RF_STATE::AUDIO) {
-			unsigned char type = m_rfSlowData.getType();
-
-			if (type == DSTAR_SLOW_DATA_TYPE_FASTDATA_BEGIN) {
-				LogMessage("D-Star, starting fast data mode");
+			unsigned char type = m_rfSlowData.getType(false);
+			//as per specs, this could be any value bewtween 0x80 and 0x9C
+			if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA) {
+				LogMessage("D-Star, starting fast data mode (RF)");
 				m_rfState = RPT_RF_STATE::DATA;
 			}
 		}
 
+		if (m_rfState == RPT_RF_STATE::DATA) {
+			unsigned char type = m_rfSlowData.getType(true);
+			// as per specs, this could be any value bewtween 0x80 and 0x9C as one fast data block can only contain 28 bytes 0x80 + 28d = 0x9C 
+			if(((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA) && type > 0x9CU) {
+				LogMessage("Invalid fast data type 0x%02X received, returning to audio mode (RF)", type);
+				m_rfState = RPT_RF_STATE::AUDIO;
+			}
+		}
+
 		if (m_rfState == RPT_RF_STATE::DATA) {
 			// Send the RSSI data to the display
 			if (m_rfN == 0U)
 				m_display->writeDStarRSSI(m_rssi);
 
-			LogDebug("D-Star, fast data sequence no. %u", m_rfN);
+			LogDebug("D-Star, RF fast data sequence no. %u", m_rfN);
 
 			m_rfBits += 48U;
 			m_rfFrames++;
@@ -395,9 +446,9 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 
 			bool complete = m_rfSlowData.isComplete();
 			if (complete) {
-				unsigned char type = m_rfSlowData.getType();
-				if (type == DSTAR_SLOW_DATA_TYPE_FASTDATA_END) {
-					LogMessage("D-Star, leaving fast data mode");
+				unsigned char type = m_rfSlowData.getType(false);
+				if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) != DSTAR_SLOW_DATA_TYPE_FASTDATA) {
+					LogMessage("D-Star, leaving fast data mode (RF)");
 					m_rfState = RPT_RF_STATE::AUDIO;
 				}
 			}
@@ -410,10 +461,10 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 
 			unsigned int errors = 0U;
 			if (::memcmp(data + 1U, DSTAR_NULL_AMBE_DATA_BYTES_SCRAMBLED, DSTAR_VOICE_FRAME_LENGTH_BYTES) == 0) {
-				LogDebug("D-Star, audio sequence no. %u, null audio", m_rfN);
+				LogDebug("D-Star, RF audio sequence no. %u, null audio", m_rfN);
 			} else {
 				errors = m_fec.regenerateDStar(data + 1U);
-				LogDebug("D-Star, audio sequence no. %u, errs: %u/48 (%.1f%%)", m_rfN, errors, float(errors) / 0.48F);
+				LogDebug("D-Star, RF audio sequence no. %u, errs: %u/48 (%.1f%%)", m_rfN, errors, float(errors) / 0.48F);
 				m_display->writeDStarBER(float(errors) / 0.48F);
 			}
 
@@ -508,6 +559,7 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 
 			m_rfN = 0U;
 			m_rfFrames = 1U;
+			m_RFdataLookBackIndex = 0U;
 
 			m_minRSSI = m_rssi;
 			m_maxRSSI = m_rssi;
@@ -676,6 +728,7 @@ void CDStarControl::writeNetwork()
 
 		m_netFrames = 0U;
 		m_netLost   = 0U;
+		m_NetdataLookBackIndex = 0U;
 
 		m_netN      = 20U;
 
@@ -706,7 +759,7 @@ void CDStarControl::writeNetwork()
 		} else {
 			m_display->writeDStar((char*)my1, (char*)my2, (char*)your, "N", (char*) "        ");
 			LogMessage("D-Star, received network header from %8.8s/%4.4s to %8.8s", my1, my2, your);
-		}	
+		}
 
 		m_elapsed.start();
 	} else if (type == TAG_EOT) {
@@ -734,92 +787,145 @@ void CDStarControl::writeNetwork()
 
 		writeEndNet();
 	} else if (type == TAG_DATA) {
-		if ((m_netState == RPT_NET_STATE::AUDIO) || (m_netState == RPT_NET_STATE::DATA)) {
-			unsigned char n = data[1U];
-
-			if (n == 0U) {
-				CSync::addDStarSync(data + 2U);
-				m_netSlowData.start();
-			} else {
-				m_netSlowData.add(data + 2U);
-
-				if (m_netState == RPT_NET_STATE::AUDIO) {
-					unsigned char type = m_netSlowData.getType();
-					if (type == DSTAR_SLOW_DATA_TYPE_FASTDATA_BEGIN) {
-						LogMessage("D-Star, starting fast data mode");
-						m_netState = RPT_NET_STATE::DATA;
-					}
-				}
-			}
-		}
-
-		if (m_netState == RPT_NET_STATE::AUDIO) {
-			unsigned char n = data[1U];
-
-			unsigned int errors = 0U;
-			if (::memcmp(data + 2U, DSTAR_NULL_AMBE_DATA_BYTES_SCRAMBLED, DSTAR_VOICE_FRAME_LENGTH_BYTES) != 0) {
-				errors = m_fec.regenerateDStar(data + 2U);
-				blankDTMF(data + 2U);
-			}
-
-			data[1U] = TAG_DATA;
-
-			// Insert silence and reject if in the past
-			bool ret = insertSilence(data + 1U, n);
-			if (!ret)
-				return;
-
-			m_netErrs += errors;
-			m_netBits += 48U;
-
-			m_netN = n;
-
-			if (m_netN != 0U) {
-				const unsigned char* text = m_netSlowData.getText();
-				if (text != nullptr)
-					LogMessage("D-Star, network slow data text = \"%s\"", text);
-			}
-
-			m_packetTimer.start();
-			m_netFrames++;
-
-#if defined(DUMP_DSTAR)
-			writeFile(data + 1U, length - 1U);
-#endif
-			writeQueueDataNet(data + 1U);
-		}
-
-		if (m_netState == RPT_NET_STATE::DATA) {
-			m_netN = data[1U];
-
-			data[1U] = TAG_DATA;
-
-			m_netBits += 48U;
-
-			if (m_netN != 0U) {
-				bool complete = m_netSlowData.isComplete();
-				if (complete) {
-					unsigned char type = m_netSlowData.getType();
-					if (type == DSTAR_SLOW_DATA_TYPE_FASTDATA_END) {
-						LogMessage("D-Star, leaving fast data mode");
-						m_netState = RPT_NET_STATE::AUDIO;
-					}
-				}
-			}
-
-			m_packetTimer.start();
-			m_netFrames++;
-
-#if defined(DUMP_DSTAR)
-			writeFile(data + 1U, length - 1U);
-#endif
-			writeQueueDataNet(data + 1U);
-		}
+		writeNetworkData(data, length);
 	} else {
 		CUtils::dump("D-Star, unknown data from network", data, DSTAR_FRAME_LENGTH_BYTES + 1U);
 	}
 }
 
+void CDStarControl::writeNetworkData(unsigned char* data, unsigned int length)
+{
+	assert(data != nullptr);
+
+	unsigned char type = data[0U];
+	assert(type == TAG_DATA);
+
+	if (m_network == nullptr)
+		return;
+
+	if ((m_netState == RPT_NET_STATE::AUDIO) || (m_netState == RPT_NET_STATE::DATA)) {
+		unsigned char n = data[1U];
+
+		if (n == 0U) {
+			CSync::addDStarSync(data + 2U);
+			m_netSlowData.start();
+		} else {
+			m_netSlowData.add(data + 2U);
+		}
+
+		if(m_NetdataLookBackIndex == 0U) {
+			m_NetdataLookBack = new unsigned char[length];
+			::memcpy(m_NetdataLookBack, data, length);
+			m_NetdataLookBackLen = length;
+			m_NetdataLookBackIndex ++;
+			return;
+		} else if (m_NetdataLookBackIndex == 1U) {
+			m_NetdataLookBackIndex ++;
+
+			if (m_netState == RPT_NET_STATE::AUDIO){
+				unsigned char type = m_netSlowData.getType(false);
+				LogMessage("A D-Star, slow data type: 0x%02X 0x%02X %i", type, type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK, m_netN);
+				// as per specs, this could be any value bewtween 0x80 and 0x9C
+				if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA){
+					LogMessage("D-Star, starting fast data mode (Net)");
+					m_netState = RPT_NET_STATE::DATA;
+				}
+			}
+			LogDebug("D-Star, processing lookback data (Net)");
+			writeNetworkData(m_NetdataLookBack, m_NetdataLookBackLen);
+			writeNetworkData(data, length);
+			delete[] m_NetdataLookBack;
+			m_NetdataLookBack = nullptr;
+			m_NetdataLookBackLen = 0U;
+			return;
+		}
+	}
+
+	if (m_netState == RPT_NET_STATE::AUDIO) {
+	    unsigned char type = m_netSlowData.getType(false);
+		LogMessage("A D-Star, slow data type: 0x%02X 0x%02X %i", type, type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK, m_netN);
+		// as per specs chapter 6.1.3, this could be any value bewtween 0x81 and 0x9C as one fast data block can only contain 28 bytes 0x80 + 28d = 0x9C 
+		if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA){
+			LogMessage("D-Star, starting fast data mode (Net)");
+			m_netState = RPT_NET_STATE::DATA;
+		}
+	}
+
+	if (m_netState == RPT_NET_STATE::DATA) {
+		unsigned char type = m_netSlowData.getType(true);
+		// as per specs chapter 6.1.3, this could be any value bewtween 0x81 and 0x9C as one fast data block can only contain 28 bytes 0x80 + 28d = 0x9C 
+		if(((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) == DSTAR_SLOW_DATA_TYPE_FASTDATA) && type > 0x9CU) {
+			LogMessage("Invalid fast data type 0x%02X received, returning to audio mode (Net)", type);
+			m_netState = RPT_NET_STATE::AUDIO;
+		}
+	}
+
+	if (m_netState == RPT_NET_STATE::AUDIO) {
+		unsigned char n = data[1U];
+
+		unsigned int errors = 0U;
+		if (::memcmp(data + 2U, DSTAR_NULL_AMBE_DATA_BYTES_SCRAMBLED, DSTAR_VOICE_FRAME_LENGTH_BYTES) != 0) {
+			errors = m_fec.regenerateDStar(data + 2U);
+			LogDebug("D-Star, Net audio sequence no. %u, errs: %u/48 (%.1f%%)", n, errors, float(errors) / 0.48F);
+			blankDTMF(data + 2U);
+		}
+
+		data[1U] = TAG_DATA;
+
+		// Insert silence and reject if in the past
+		bool ret = insertSilence(data + 1U, n);
+		if (!ret)
+			return;
+
+		m_netErrs += errors;
+		m_netBits += 48U;
+
+		m_netN = n;
+
+		if (m_netN != 0U) {
+			const unsigned char* text = m_netSlowData.getText();
+			if (text != nullptr)
+				LogMessage("D-Star, network slow data text = \"%s\"", text);
+		}
+			
+		m_packetTimer.start();
+		m_netFrames++;
+
+#if defined(DUMP_DSTAR)
+		writeFile(data + 1U, length - 1U);
+#endif
+		writeQueueDataNet(data + 1U);
+	}
+
+	if (m_netState == RPT_NET_STATE::DATA) {
+		m_netN = data[1U];
+		LogDebug("D-Star, Net fast data sequence no. %u", m_netN);
+
+		data[1U] = TAG_DATA;
+
+		m_netBits += 48U;
+
+		if (m_netN != 0U) {
+			bool complete = m_netSlowData.isComplete();
+			if (complete) {
+				unsigned char type = m_netSlowData.getType();
+				if ((type & DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK) != DSTAR_SLOW_DATA_TYPE_FASTDATA) {
+					LogMessage("D-Star, leaving fast data mode (Net)");
+					m_netState = RPT_NET_STATE::AUDIO;
+				}
+			}
+		}
+
+		m_packetTimer.start();
+		m_netFrames++;
+
+#if defined(DUMP_DSTAR)
+		writeFile(data + 1U, length - 1U);
+#endif
+		writeQueueDataNet(data + 1U);
+	}
+}
+
 void CDStarControl::clock()
 {
 	unsigned int ms = m_interval.elapsed();
diff --git a/DStarControl.h b/DStarControl.h
index 1916e75..17ab58a 100644
--- a/DStarControl.h
+++ b/DStarControl.h
@@ -99,8 +99,15 @@ private:
 	unsigned int               m_rssiCount;
 	bool                       m_enabled;
 	FILE*                      m_fp;
+	unsigned char *            m_RFdataLookBack;
+	unsigned int               m_RFdataLookBackLen;
+	unsigned int               m_RFdataLookBackIndex;
+	unsigned char *            m_NetdataLookBack;
+	unsigned int               m_NetdataLookBackLen;
+	unsigned int               m_NetdataLookBackIndex;
 
 	void writeNetwork();
+	void writeNetworkData(unsigned char* data, unsigned int length);
 
 	void writeQueueHeaderRF(const unsigned char* data);
 	void writeQueueDataRF(const unsigned char* data);
diff --git a/DStarDefines.h b/DStarDefines.h
index 0098f9e..3df93d8 100644
--- a/DStarDefines.h
+++ b/DStarDefines.h
@@ -48,8 +48,8 @@ const unsigned char DSTAR_SLOW_DATA_TYPE_MASK           = 0xF0U;
 const unsigned char DSTAR_SLOW_DATA_TYPE_GPSDATA        = 0x30U;
 const unsigned char DSTAR_SLOW_DATA_TYPE_TEXT           = 0x40U;
 const unsigned char DSTAR_SLOW_DATA_TYPE_HEADER         = 0x50U;
-const unsigned char DSTAR_SLOW_DATA_TYPE_FASTDATA_END   = 0x80U;
-const unsigned char DSTAR_SLOW_DATA_TYPE_FASTDATA_BEGIN = 0x90U;
+const unsigned char DSTAR_SLOW_DATA_TYPE_FASTDATA       = 0x80U;
+const unsigned char DSTAR_SLOW_DATA_TYPE_FASTDATA_MASK  = 0xE0U;
 const unsigned char DSTAR_SLOW_DATA_TYPE_SQUELCH        = 0xC0U;
 const unsigned char DSTAR_SLOW_DATA_LENGTH_MASK         = 0x0FU;
 
diff --git a/DStarSlowData.cpp b/DStarSlowData.cpp
index c3d75f3..b14d4b2 100644
--- a/DStarSlowData.cpp
+++ b/DStarSlowData.cpp
@@ -67,7 +67,7 @@ void CDStarSlowData::add(const unsigned char* data)
 		m_buffer[5U] = data[11U] ^ DSTAR_SCRAMBLER_BYTES[2U];
 		m_state = SDD_STATE::FIRST;
 		m_complete = true;
-		CUtils::dump(1U, "D-Star slow data element", m_buffer, 6U);
+		////CUtils::dump(1U, "D-Star slow data element", m_buffer, 6U);
 		loadHeader();
 		loadText();
 		break;
@@ -111,7 +111,7 @@ void CDStarSlowData::loadText()
 {
 	switch (m_buffer[0U]) {
 	case DSTAR_SLOW_DATA_TYPE_TEXT | 0U:
-		CUtils::dump(1U, "D-Star slow data text fragment 0", m_buffer, 6U);
+		//CUtils::dump(1U, "D-Star slow data text fragment 0", m_buffer, 6U);
 		m_text[0U] = m_buffer[1U] & 0x7FU;
 		m_text[1U] = m_buffer[2U] & 0x7FU;
 		m_text[2U] = m_buffer[3U] & 0x7FU;
@@ -121,7 +121,7 @@ void CDStarSlowData::loadText()
 		break;
 
 	case DSTAR_SLOW_DATA_TYPE_TEXT | 1U:
-		CUtils::dump(1U, "D-Star slow data text fragment 1", m_buffer, 6U);
+		//CUtils::dump(1U, "D-Star slow data text fragment 1", m_buffer, 6U);
 		m_text[5U] = m_buffer[1U] & 0x7FU;
 		m_text[6U] = m_buffer[2U] & 0x7FU;
 		m_text[7U] = m_buffer[3U] & 0x7FU;
@@ -131,7 +131,7 @@ void CDStarSlowData::loadText()
 		break;
 
 	case DSTAR_SLOW_DATA_TYPE_TEXT | 2U:
-		CUtils::dump(1U, "D-Star slow data text fragment 2", m_buffer, 6U);
+		//CUtils::dump(1U, "D-Star slow data text fragment 2", m_buffer, 6U);
 		m_text[10U] = m_buffer[1U] & 0x7FU;
 		m_text[11U] = m_buffer[2U] & 0x7FU;
 		m_text[12U] = m_buffer[3U] & 0x7FU;
@@ -141,7 +141,7 @@ void CDStarSlowData::loadText()
 		break;
 
 	case DSTAR_SLOW_DATA_TYPE_TEXT | 3U:
-		CUtils::dump(1U, "D-Star slow data text fragment 3", m_buffer, 6U);
+		//CUtils::dump(1U, "D-Star slow data text fragment 3", m_buffer, 6U);
 		m_text[15U] = m_buffer[1U] & 0x7FU;
 		m_text[16U] = m_buffer[2U] & 0x7FU;
 		m_text[17U] = m_buffer[3U] & 0x7FU;
@@ -161,7 +161,7 @@ const unsigned char* CDStarSlowData::getText()
 	if (m_textBits != 0x0FU)
 		return nullptr;
 
-	CUtils::dump(1U, "D-Star slow data text", m_text, 20U);
+	//CUtils::dump(1U, "D-Star slow data text", m_text, 20U);
 
 	m_textBits = 0x00U;
 
@@ -237,9 +237,9 @@ void CDStarSlowData::getSlowData(unsigned char* data)
 	}
 }
 
-unsigned char CDStarSlowData::getType() const
+unsigned char CDStarSlowData::getType(bool unmasked) const
 {
-	return m_buffer[0U] & DSTAR_SLOW_DATA_TYPE_MASK;
+	return unmasked ? m_buffer[0U] : m_buffer[0U] & DSTAR_SLOW_DATA_TYPE_MASK ;
 }
 
 bool CDStarSlowData::isComplete() const
diff --git a/DStarSlowData.h b/DStarSlowData.h
index 5b8b737..4353bf9 100644
--- a/DStarSlowData.h
+++ b/DStarSlowData.h
@@ -30,7 +30,7 @@ public:
 
 	CDStarHeader*        getHeader();
 	const unsigned char* getText();
-	unsigned char        getType() const;
+	unsigned char        getType(bool unmasked = false) const;
 
 	bool isComplete() const;