diff --git a/DStarControl.cpp b/DStarControl.cpp
index 9181e1d..6846cfd 100644
--- a/DStarControl.cpp
+++ b/DStarControl.cpp
@@ -341,31 +341,20 @@ bool CDStarControl::writeModem(unsigned char *data, unsigned int len)
 			return false;
 		}
 
-		// Data signatures only appear at the beginning of the frame
-		if (m_rfState == RS_RF_AUDIO && m_rfFrames < 21U) {
-			if (CUtils::compare(data + 1U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Kenwood)");
-				m_rfState = RS_RF_DATA;
-			} else if (CUtils::compare(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Icom)");
-				m_rfState = RS_RF_DATA;
-			} else if (CUtils::compare(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Icom)");
+		// Fix any scrambled null data frames
+		if (CUtils::compare(data + 1U, DSTAR_NULL_FRAME_DATA_SRAMBLED_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
+			::memcpy(data + 1U, DSTAR_NULL_FRAME_DATA_SRAMBLED_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES);
+
+		// Check for the fast data signature
+		if (m_rfState == RS_RF_AUDIO) {
+			unsigned char slowDataType = data[DSTAR_VOICE_FRAME_LENGTH_BYTES + 1U] & DSTAR_SLOW_DATA_TYPE_MASK;
+			if (slowDataType == DSTAR_SLOW_DATA_TYPE_FAST_DATA1 || slowDataType == DSTAR_SLOW_DATA_TYPE_FAST_DATA2) {
+				LogMessage("D-Star, switching to fast data mode");
 				m_rfState = RS_RF_DATA;
 			}
 		}
 
 		if (m_rfState == RS_RF_DATA) {
-			// Regenerate the data mode markers
-			if (m_rfFrames < 21U) {
-				if (CUtils::compare(data + 1U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 1U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-				else if (CUtils::compare(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-				else if (CUtils::compare(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 1U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-			}
-
 			m_rfBits += 72U;
 			m_rfErrs  = 0U;
 			m_rfFrames++;
@@ -714,31 +703,20 @@ void CDStarControl::writeNetwork()
 			writeEndNet();
 		}
 	} else if (type == TAG_DATA) {
-		// Data signatures only appear at the beginning of the frame
-		if (m_netState == RS_NET_AUDIO && m_netFrames < 21U) {
-			if (CUtils::compare(data + 2U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Kenwood)");
-				m_netState = RS_NET_DATA;
-			} else if (CUtils::compare(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Icom)");
-				m_netState = RS_NET_DATA;
-			} else if (CUtils::compare(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U) {
-				LogMessage("D-Star, switching to data mode (Icom)");
+		// Fix any scrambled null data frames
+		if (CUtils::compare(data + 2U, DSTAR_NULL_FRAME_DATA_SRAMBLED_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
+			::memcpy(data + 2U, DSTAR_NULL_FRAME_DATA_SRAMBLED_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES);
+
+		// Check for the fast data signature
+		if (m_netState == RS_NET_AUDIO) {
+			unsigned char slowDataType = data[DSTAR_VOICE_FRAME_LENGTH_BYTES + 2U] & DSTAR_SLOW_DATA_TYPE_MASK;
+			if (slowDataType == DSTAR_SLOW_DATA_TYPE_FAST_DATA1 || slowDataType == DSTAR_SLOW_DATA_TYPE_FAST_DATA2) {
+				LogMessage("D-Star, switching to fast data mode");
 				m_netState = RS_NET_DATA;
 			}
 		}
 
 		if (m_netState == RS_NET_DATA) {
-			// Regenerate the data mode markers
-			if (m_netFrames < 21U) {
-				if (CUtils::compare(data + 2U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 2U, DSTAR_KENWOOD_DATA_MODE_BYTES, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-				else if (CUtils::compare(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES1, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-				else if (CUtils::compare(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES) < 5U)
-					::memcpy(data + 2U, DSTAR_ICOM_DATA_MODE_BYTES2, DSTAR_VOICE_FRAME_LENGTH_BYTES);
-			}
-
 			unsigned char n = data[1U];
 
 			data[1U] = TAG_DATA;
diff --git a/DStarDefines.h b/DStarDefines.h
index 697f57a..821a7e2 100644
--- a/DStarDefines.h
+++ b/DStarDefines.h
@@ -36,9 +36,7 @@ const unsigned char DSTAR_NULL_SLOW_DATA_BYTES[] = { 0x16, 0x29, 0xF5 };
 const unsigned char DSTAR_NULL_FRAME_SYNC_BYTES[] = { TAG_DATA, 0x9E, 0x8D, 0x32, 0x88, 0x26, 0x1A, 0x3F, 0x61, 0xE8, 0x55, 0x2D, 0x16 };
 const unsigned char DSTAR_NULL_FRAME_DATA_BYTES[] = { TAG_DATA, 0x9E, 0x8D, 0x32, 0x88, 0x26, 0x1A, 0x3F, 0x61, 0xE8, 0x16, 0x29, 0xF5 };
 
-const unsigned char DSTAR_KENWOOD_DATA_MODE_BYTES[] = { 0xEEU, 0xC2U, 0xA1U, 0xC8U, 0x42U, 0x6EU, 0x52U, 0x51U, 0xC3U };
-const unsigned char DSTAR_ICOM_DATA_MODE_BYTES1[]   = { 0xB2U, 0x4DU, 0x22U, 0x48U, 0xC0U, 0x16U, 0x28U, 0x26U, 0xC8U };
-const unsigned char DSTAR_ICOM_DATA_MODE_BYTES2[]   = { 0x70U, 0x4FU, 0x93U, 0x40U, 0x64U, 0x74U, 0x6DU, 0x30U, 0x2BU };
+const unsigned char DSTAR_NULL_FRAME_DATA_SRAMBLED_BYTES[] = { 0xEEU, 0xC2U, 0xA1U, 0xC8U, 0x42U, 0x6EU, 0x52U, 0x51U, 0xC3U };
 
 const unsigned int  DSTAR_VOICE_FRAME_LENGTH_BYTES = 9U;
 const unsigned int  DSTAR_DATA_FRAME_LENGTH_BYTES  = 3U;
@@ -46,12 +44,14 @@ const unsigned int  DSTAR_DATA_FRAME_LENGTH_BYTES  = 3U;
 const unsigned int  DSTAR_LONG_CALLSIGN_LENGTH  = 8U;
 const unsigned int  DSTAR_SHORT_CALLSIGN_LENGTH = 4U;
 
-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_SQUELCH = 0xC0U;
-const unsigned char DSTAR_SLOW_DATA_LENGTH_MASK  = 0x0FU;
+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_FAST_DATA1 = 0x80U;
+const unsigned char DSTAR_SLOW_DATA_TYPE_FAST_DATA2 = 0x90U;
+const unsigned char DSTAR_SLOW_DATA_TYPE_SQUELCH    = 0xC0U;
+const unsigned char DSTAR_SLOW_DATA_LENGTH_MASK     = 0x0FU;
 
 const unsigned char DSTAR_SCRAMBLER_BYTES[] = {0x70U, 0x4FU, 0x93U};