diff --git a/src/modem/Modem.cpp b/src/modem/Modem.cpp
index bfd60a3a..e5ded669 100644
--- a/src/modem/Modem.cpp
+++ b/src/modem/Modem.cpp
@@ -1155,7 +1155,16 @@ bool Modem::hasError() const
 /// </summary>
 void Modem::clearDMRFrame1()
 {
-    // TODO -- implement modem side buffer clear
+    uint8_t buffer[3U];
+
+    buffer[0U] = DVM_FRAME_START;
+    buffer[1U] = 3U;
+    buffer[2U] = CMD_DMR_CLEAR1;
+#if DEBUG_MODEM
+    Utils::dump(1U, "Modem::clearDMRFrame1(), Written", buffer, 3U);
+#endif
+    write(buffer, 3U);
+    Thread::sleep(5); // 5ms delay
 }
 
 /// <summary>
@@ -1163,7 +1172,16 @@ void Modem::clearDMRFrame1()
 /// </summary>
 void Modem::clearDMRFrame2()
 {
-    // TODO -- implement modem side buffer clear
+    uint8_t buffer[3U];
+
+    buffer[0U] = DVM_FRAME_START;
+    buffer[1U] = 3U;
+    buffer[2U] = CMD_DMR_CLEAR2;
+#if DEBUG_MODEM
+    Utils::dump(1U, "Modem::clearDMRFrame2(), Written", buffer, 3U);
+#endif
+    write(buffer, 3U);
+    Thread::sleep(5); // 5ms delay
 }
 
 /// <summary>
@@ -1180,6 +1198,7 @@ void Modem::clearP25Frame()
     Utils::dump(1U, "Modem::clearP25Data(), Written", buffer, 3U);
 #endif
     write(buffer, 3U);
+    Thread::sleep(5); // 5ms delay
 }
 
 /// <summary>
@@ -1187,7 +1206,16 @@ void Modem::clearP25Frame()
 /// </summary>
 void Modem::clearNXDNFrame()
 {
-    // TODO -- implement modem side buffer clear
+    uint8_t buffer[3U];
+
+    buffer[0U] = DVM_FRAME_START;
+    buffer[1U] = 3U;
+    buffer[2U] = CMD_NXDN_CLEAR;
+#if DEBUG_MODEM
+    Utils::dump(1U, "Modem::clearNXDNFrame(), Written", buffer, 3U);
+#endif
+    write(buffer, 3U);
+    Thread::sleep(5); // 5ms delay
 }
 
 /// <summary>
@@ -2536,6 +2564,10 @@ std::string Modem::cmdToString(uint8_t opcode)
         return std::string("DMR_ABORT");
     case CMD_DMR_CACH_AT_CTRL:
         return std::string("DMR_CACH_AT_CTRL");
+    case CMD_DMR_CLEAR1:
+        return std::string("DMR_CLEAR1");
+    case CMD_DMR_CLEAR2:
+        return std::string("DMR_CLEAR2");
 
     case CMD_P25_DATA:
         return std::string("P25_DATA");
@@ -2548,6 +2580,8 @@ std::string Modem::cmdToString(uint8_t opcode)
         return std::string("NXDN_DATA");
     case CMD_NXDN_LOST:
         return std::string("NXDN_LOST");
+    case CMD_NXDN_CLEAR:
+        return std::string("NXDN_CLEAR");
 
     case CMD_ACK:
         return std::string("ACK");
diff --git a/src/modem/Modem.h b/src/modem/Modem.h
index 39e9d569..ee1c2621 100644
--- a/src/modem/Modem.h
+++ b/src/modem/Modem.h
@@ -148,6 +148,8 @@ namespace modem
         CMD_DMR_START = 0x1DU,
         CMD_DMR_ABORT = 0x1EU,
         CMD_DMR_CACH_AT_CTRL = 0x1FU,
+        CMD_DMR_CLEAR1 = 0x20U,
+        CMD_DMR_CLEAR2 = 0x21U,
 
         CMD_P25_DATA = 0x31U,
         CMD_P25_LOST = 0x32U,
@@ -155,6 +157,7 @@ namespace modem
 
         CMD_NXDN_DATA = 0x41U,
         CMD_NXDN_LOST = 0x42U,
+        CMD_NXDN_CLEAR = 0x43U,
 
         CMD_ACK = 0x70U,
         CMD_NAK = 0x7FU,
diff --git a/src/p25/Control.cpp b/src/p25/Control.cpp
index f8d810d7..04ec6979 100644
--- a/src/p25/Control.cpp
+++ b/src/p25/Control.cpp
@@ -127,7 +127,7 @@ Control::Control(bool authoritative, uint32_t nac, uint32_t callHang, uint32_t q
     m_rfTGHang(1000U, tgHang),
     m_netTimeout(1000U, timeout),
     m_networkWatchdog(1000U, 0U, 1500U),
-    m_ccPacketInterval(1000U, 0U, 5U),
+    m_ccPacketInterval(1000U, 0U, 10U),
     m_hangCount(3U * 8U),
     m_tduPreambleCount(8U),
     m_ccFrameCnt(0U),
@@ -646,6 +646,8 @@ uint32_t Control::getFrame(uint8_t* data)
 
     // tx immediate queue takes priority
     if (!m_txImmQueue.isEmpty()) {
+        m_modem->clearP25Frame();
+
         m_txImmQueue.getData(&len, 1U);
         m_txImmQueue.getData(data, len);
     }
diff --git a/src/p25/lc/tsbk/OSP_QUE_RSP.cpp b/src/p25/lc/tsbk/OSP_QUE_RSP.cpp
index b6d427b5..95f9e929 100644
--- a/src/p25/lc/tsbk/OSP_QUE_RSP.cpp
+++ b/src/p25/lc/tsbk/OSP_QUE_RSP.cpp
@@ -93,7 +93,7 @@ void OSP_QUE_RSP::encode(uint8_t* data, bool rawTSBK, bool noTrellis)
     }
 
     tsbkValue = (m_aivFlag) ? 0x80U : 0x00U;                                        // Additional Info Flag
-    tsbkValue = (tsbkValue << 6) + m_service;                                       // Service Type
+    tsbkValue = (tsbkValue << 6) + (m_service & 0x3FU);                             // Service Type
     tsbkValue = (tsbkValue << 8) + m_response;                                      // Deny/Queue Reason
 
     if (m_group) {
diff --git a/src/p25/packet/Trunk.cpp b/src/p25/packet/Trunk.cpp
index 473f9378..9549961c 100644
--- a/src/p25/packet/Trunk.cpp
+++ b/src/p25/packet/Trunk.cpp
@@ -37,6 +37,7 @@
 #include "edac/CRC.h"
 #include "remote/RESTClient.h"
 #include "Log.h"
+#include "Thread.h"
 #include "Utils.h"
 
 using namespace p25;
@@ -302,7 +303,7 @@ bool Trunk::process(uint8_t* data, uint32_t len, std::unique_ptr<lc::TSBK> preDe
 
                 if (iosp->getResponse() == P25_ANS_RSP_PROCEED) {
                     if (m_p25->m_ackTSBKRequests) {
-                        writeRF_TSDU_ACK_FNE(dstId, TSBK_IOSP_UU_ANS, false, true);
+                        writeRF_TSDU_ACK_FNE(dstId, TSBK_IOSP_UU_VCH, false, true);
                     }
 
                     if (m_p25->m_authoritative) {
@@ -316,10 +317,12 @@ bool Trunk::process(uint8_t* data, uint32_t len, std::unique_ptr<lc::TSBK> preDe
                     }
                 }
                 else if (iosp->getResponse() == P25_ANS_RSP_DENY) {
-                    writeRF_TSDU_Deny(P25_WUID_FNE, srcId, P25_DENY_RSN_TGT_UNIT_REFUSED, TSBK_IOSP_UU_ANS);
+                    writeRF_TSDU_ACK_FNE(dstId, TSBK_IOSP_UU_VCH, false, true);
+                    writeRF_TSDU_Deny(P25_WUID_FNE, dstId, P25_DENY_RSN_TGT_UNIT_REFUSED, TSBK_IOSP_UU_VCH);
                 }
                 else if (iosp->getResponse() == P25_ANS_RSP_WAIT) {
-                    writeRF_TSDU_Queue(P25_WUID_FNE, srcId, P25_QUE_RSN_TGT_UNIT_QUEUED, TSBK_IOSP_UU_ANS);
+                    writeRF_TSDU_ACK_FNE(dstId, TSBK_IOSP_UU_VCH, false, true);
+                    writeRF_TSDU_Queue(P25_WUID_FNE, dstId, P25_QUE_RSN_TGT_UNIT_QUEUED, TSBK_IOSP_UU_VCH, false, false);
                 }
             }
             break;
@@ -2264,6 +2267,10 @@ bool Trunk::writeRF_TSDU_Grant(uint32_t srcId, uint32_t dstId, uint8_t serviceOp
 
             // transmit group grant
             writeRF_TSDU_SBF_Imm(iosp.get(), net);
+            if (m_p25->m_voiceOnControl) {
+                for (int i = 0; i < 3; i++)
+                    writeRF_TSDU_SBF(iosp.get(), net);
+            }
         }
         else {
             if (!net) {
@@ -2314,6 +2321,10 @@ bool Trunk::writeRF_TSDU_Grant(uint32_t srcId, uint32_t dstId, uint8_t serviceOp
 
             // transmit private grant
             writeRF_TSDU_SBF_Imm(iosp.get(), net);
+            if (m_p25->m_voiceOnControl) {
+                for (int i = 0; i < 3; i++)
+                    writeRF_TSDU_SBF(iosp.get(), net);
+            }
         }
     }
 
@@ -2603,7 +2614,8 @@ void Trunk::writeRF_TSDU_U_Dereg_Ack(uint32_t srcId)
 /// <param name="reason"></param>
 /// <param name="service"></param>
 /// <param name="aiv"></param>
-void Trunk::writeRF_TSDU_Queue(uint32_t srcId, uint32_t dstId, uint8_t reason, uint8_t service, bool aiv)
+/// <param name="grp"></param>
+void Trunk::writeRF_TSDU_Queue(uint32_t srcId, uint32_t dstId, uint8_t reason, uint8_t service, bool aiv, bool grp)
 {
     std::unique_ptr<OSP_QUE_RSP> osp = new_unique(OSP_QUE_RSP);
     osp->setAIV(aiv);
@@ -2611,6 +2623,7 @@ void Trunk::writeRF_TSDU_Queue(uint32_t srcId, uint32_t dstId, uint8_t reason, u
     osp->setDstId(dstId);
     osp->setService(service);
     osp->setResponse(reason);
+    osp->setGroup(grp);
 
     if (m_verbose) {
         LogMessage(LOG_RF, P25_TSDU_STR ", %s, AIV = %u, reason = $%02X, srcId = %u, dstId = %u",
diff --git a/src/p25/packet/Trunk.h b/src/p25/packet/Trunk.h
index 43aad598..2101ae5c 100644
--- a/src/p25/packet/Trunk.h
+++ b/src/p25/packet/Trunk.h
@@ -208,7 +208,7 @@ namespace p25
             /// <summary>Helper to write a unit de-registration acknowledge packet.</summary>
             void writeRF_TSDU_U_Dereg_Ack(uint32_t srcId);
             /// <summary>Helper to write a queue packet.</summary>
-            void writeRF_TSDU_Queue(uint32_t srcId, uint32_t dstId, uint8_t reason, uint8_t service, bool aiv = false);
+            void writeRF_TSDU_Queue(uint32_t srcId, uint32_t dstId, uint8_t reason, uint8_t service, bool aiv = false, bool group = true);
             /// <summary>Helper to write a location registration response packet.</summary>
             bool writeRF_TSDU_Loc_Reg_Rsp(uint32_t srcId, uint32_t dstId, bool grp);
 
diff --git a/src/p25/packet/Voice.cpp b/src/p25/packet/Voice.cpp
index 60f49505..022307b9 100644
--- a/src/p25/packet/Voice.cpp
+++ b/src/p25/packet/Voice.cpp
@@ -389,7 +389,13 @@ bool Voice::process(uint8_t* data, uint32_t len)
 
             m_p25->m_rfState = RS_RF_AUDIO;
 
-            m_p25->m_rfTGHang.start();
+            if (group) {
+                m_p25->m_rfTGHang.start();
+            }
+            else {
+                m_p25->m_rfTGHang.stop();
+            }
+            
             m_p25->m_rfLastDstId = dstId;
 
             // make sure we actually got a HDU -- otherwise treat the call as a late entry