diff --git a/config.example.yml b/config.example.yml
index a903345a..590a6f68 100644
--- a/config.example.yml
+++ b/config.example.yml
@@ -40,6 +40,9 @@ protocols:
         dumpDataPacket: false
         repeatDataPacket: true
         dumpCsbkData: false
+        verifyReg: false
+        nRandWait: 8
+        backOff: 1
         callHang: 5
         txHang: 8
         silenceThreshold: 21
diff --git a/dmr/Control.cpp b/dmr/Control.cpp
index fde2933e..70b57832 100644
--- a/dmr/Control.cpp
+++ b/dmr/Control.cpp
@@ -88,7 +88,7 @@ Control::Control(uint32_t colorCode, uint32_t callHang, uint32_t queueSize, bool
     assert(rssiMapper != NULL);
 
     acl::AccessControl::init(m_ridLookup, m_tidLookup);
-    Slot::init(colorCode, SiteData(), embeddedLCOnly, dumpTAData, callHang, modem, network, duplex, m_ridLookup, m_tidLookup, m_idenTable, rssiMapper, jitter);
+    Slot::init(this, colorCode, SiteData(), embeddedLCOnly, dumpTAData, callHang, modem, network, duplex, m_ridLookup, m_tidLookup, m_idenTable, rssiMapper, jitter, verbose);
     
     m_slot1 = new Slot(1U, timeout, tgHang, queueSize, dumpDataPacket, repeatDataPacket, dumpCSBKData, debug, verbose);
     m_slot2 = new Slot(2U, timeout, tgHang, queueSize, dumpDataPacket, repeatDataPacket, dumpCSBKData, debug, verbose);
@@ -117,6 +117,8 @@ void Control::setOptions(yaml::Node& conf, uint32_t netId, uint8_t siteId, uint8
     yaml::Node systemConf = conf["system"];
     yaml::Node dmrProtocol = conf["protocols"]["dmr"];
 
+    Slot::m_verifyReg = dmrProtocol["verifyReg"].as<bool>(false);
+
     uint8_t nRandWait = (uint8_t)dmrProtocol["nRandWait"].as<uint32_t>(dmr::DEFAULT_NRAND_WAIT);
     if (nRandWait > 15U)
         nRandWait = 15U;
@@ -165,7 +167,10 @@ void Control::setOptions(yaml::Node& conf, uint32_t netId, uint8_t siteId, uint8
             LogInfo("    TSCC Aloha Random Access Wait: %u", nRandWait);
             LogInfo("    TSCC Aloha Backoff: %u", backOff);
         }
+
         LogInfo("    Silence Threshold: %u (%.1f%%)", silenceThreshold, float(silenceThreshold) / 1.41F);
+
+        LogInfo("    Verify Registration: %s", Slot::m_verifyReg ? "yes" : "no");
     }
 }
 
@@ -383,3 +388,26 @@ void Control::setDebugVerbose(bool debug, bool verbose)
     m_slot1->setDebugVerbose(debug, verbose);
     m_slot2->setDebugVerbose(debug, verbose);
 }
+
+// ---------------------------------------------------------------------------
+//  Private Class Members
+// ---------------------------------------------------------------------------
+
+/// <summary>
+/// Helper to return the slot carrying the TSCC.
+/// </summary>
+/// <returns>Pointer to the TSCC slot instance.</returns>
+Slot* Control::getTSCCSlot() const
+{
+    switch (m_tsccSlotNo) {
+    case 1U:
+        return m_slot1;
+        break;
+    case 2U:
+        return m_slot2;
+        break;
+    default:
+        LogError(LOG_NET, "DMR, invalid slot, TSCC disabled, slotNo = %u", m_tsccSlotNo);
+        return NULL;
+    }
+}
diff --git a/dmr/Control.h b/dmr/Control.h
index e09a1ca7..e11c44a9 100644
--- a/dmr/Control.h
+++ b/dmr/Control.h
@@ -50,6 +50,7 @@ namespace dmr
     // ---------------------------------------------------------------------------
     
     class HOST_SW_API Slot;
+    namespace packet { class HOST_SW_API ControlSignaling; }
 
     // ---------------------------------------------------------------------------
     //  Class Declaration
@@ -101,6 +102,9 @@ namespace dmr
         void setDebugVerbose(bool debug, bool verbose);
 
     private:
+        friend class Slot;
+        friend class packet::ControlSignaling;
+
         uint32_t m_colorCode;
 
         modem::Modem* m_modem;
@@ -120,6 +124,9 @@ namespace dmr
         bool m_dumpCSBKData;
         bool m_verbose;
         bool m_debug;
+
+        /// <summary>Helper to return the slot carrying the TSCC.</summary>
+        Slot* getTSCCSlot() const;
     };
 } // namespace dmr
 
diff --git a/dmr/DMRDefines.h b/dmr/DMRDefines.h
index d53c7c95..c398b614 100644
--- a/dmr/DMRDefines.h
+++ b/dmr/DMRDefines.h
@@ -278,6 +278,7 @@ namespace dmr
     const uint8_t   CSBKO_UU_ANS_RSP = 0x05U;               // UU ANS RSP - Unit to Unit Answer Response
     const uint8_t   CSBKO_CTCSBK = 0x07U;                   // CT CSBK - Channel Timing CSBK
     const uint8_t   CSBKO_ALOHA = 0x19U;                    // ALOHA - Aloha PDUs for the random access protocol
+    const uint8_t   CSBKO_AHOY = 0x1CU;                     // AHOY - Enquiry from TSCC
     const uint8_t   CSBKO_RAND = 0x1FU;                     // (ETSI) RAND - Random Access / (DMRA) CALL ALRT - Call Alert
     const uint8_t   CSBKO_ACK_RSP = 0x20U;                  // ACK RSP - Acknowledge Response
     const uint8_t   CSBKO_EXT_FNCT = 0x24U;                 // (DMRA) EXT FNCT - Extended Function
diff --git a/dmr/Slot.cpp b/dmr/Slot.cpp
index 07c0b786..b3a172c2 100644
--- a/dmr/Slot.cpp
+++ b/dmr/Slot.cpp
@@ -54,6 +54,8 @@ const uint16_t TSCC_MAX_CNT = 511U;
 //  Static Class Members
 // ---------------------------------------------------------------------------
 
+Control* Slot::m_dmr = NULL;
+
 uint32_t Slot::m_colorCode = 0U;
 
 SiteData Slot::m_siteData = SiteData();
@@ -70,6 +72,7 @@ bool Slot::m_duplex = true;
 lookups::IdenTableLookup* Slot::m_idenTable = NULL;
 lookups::RadioIdLookup* Slot::m_ridLookup = NULL;
 lookups::TalkgroupIdLookup* Slot::m_tidLookup = NULL;
+lookups::AffiliationLookup *Slot::m_affiliations = NULL;
 
 lookups::IdenTable Slot::m_idenEntry = lookups::IdenTable();
 
@@ -89,6 +92,8 @@ uint8_t Slot::m_flco2;
 uint8_t Slot::m_id2 = 0U;
 bool Slot::m_voice2 = true;
 
+bool Slot::m_verifyReg = false;
+
 uint16_t Slot::m_tsccCnt = 0U;
 
 uint8_t Slot::m_alohaNRandWait = DEFAULT_NRAND_WAIT;
@@ -561,6 +566,7 @@ void Slot::setSilenceThreshold(uint32_t threshold)
 /// <summary>
 /// Helper to initialize the DMR slot processor.
 /// </summary>
+/// <param name="dmr">Instance of the Control class.</param>
 /// <param name="colorCode">DMR access color code.</param>
 /// <param name="siteData">DMR site data.</param>
 /// <param name="embeddedLCOnly"></param>
@@ -574,16 +580,20 @@ void Slot::setSilenceThreshold(uint32_t threshold)
 /// <param name="idenTable">Instance of the IdenTableLookup class.</param>
 /// <param name="rssi">Instance of the RSSIInterpolator class.</param>
 /// <param name="jitter"></param>
-void Slot::init(uint32_t colorCode, SiteData siteData, bool embeddedLCOnly, bool dumpTAData, uint32_t callHang, modem::Modem* modem,
+/// <param name="verbose"></param>
+void Slot::init(Control* dmr, uint32_t colorCode, SiteData siteData, bool embeddedLCOnly, bool dumpTAData, uint32_t callHang, modem::Modem* modem,
     network::BaseNetwork* network, bool duplex, lookups::RadioIdLookup* ridLookup, lookups::TalkgroupIdLookup* tidLookup,
-    lookups::IdenTableLookup* idenTable, lookups::RSSIInterpolator* rssiMapper, uint32_t jitter)
+    lookups::IdenTableLookup* idenTable, lookups::RSSIInterpolator* rssiMapper, uint32_t jitter, bool verbose)
 {
+    assert(dmr != NULL);
     assert(modem != NULL);
     assert(ridLookup != NULL);
     assert(tidLookup != NULL);
     assert(idenTable != NULL);
     assert(rssiMapper != NULL);
 
+    m_dmr = dmr;
+
     m_colorCode = colorCode;
 
     m_siteData = siteData;
@@ -599,6 +609,7 @@ void Slot::init(uint32_t colorCode, SiteData siteData, bool embeddedLCOnly, bool
     m_idenTable = idenTable;
     m_ridLookup = ridLookup;
     m_tidLookup = tidLookup;
+    m_affiliations = new lookups::AffiliationLookup("DMR Affiliations", verbose);
 
     m_hangCount = callHang * 17U;
 
diff --git a/dmr/Slot.h b/dmr/Slot.h
index 5b2f9176..d61a276a 100644
--- a/dmr/Slot.h
+++ b/dmr/Slot.h
@@ -43,6 +43,7 @@
 #include "lookups/IdenTableLookup.h"
 #include "lookups/RadioIdLookup.h"
 #include "lookups/TalkgroupIdLookup.h"
+#include "lookups/AffiliationLookup.h"
 #include "RingBuffer.h"
 #include "StopWatch.h"
 #include "Timer.h"
@@ -55,6 +56,7 @@ namespace dmr
     //  Class Prototypes
     // ---------------------------------------------------------------------------
     
+    class HOST_SW_API Control;
     namespace packet { class HOST_SW_API Voice; }
     namespace packet { class HOST_SW_API Data; }
     namespace packet { class HOST_SW_API ControlSignaling; }
@@ -104,9 +106,9 @@ namespace dmr
         void setSilenceThreshold(uint32_t threshold);
 
         /// <summary>Helper to initialize the slot processor.</summary>
-        static void init(uint32_t colorCode, SiteData siteData, bool embeddedLCOnly, bool dumpTAData, uint32_t callHang, modem::Modem* modem,
+        static void init(Control* dmr, uint32_t colorCode, SiteData siteData, bool embeddedLCOnly, bool dumpTAData, uint32_t callHang, modem::Modem* modem,
             network::BaseNetwork* network, bool duplex, lookups::RadioIdLookup* ridLookup, lookups::TalkgroupIdLookup* tidLookup,
-            lookups::IdenTableLookup* idenTable, lookups::RSSIInterpolator* rssiMapper, uint32_t jitter);
+            lookups::IdenTableLookup* idenTable, lookups::RSSIInterpolator* rssiMapper, uint32_t jitter, bool verbose);
         /// <summary>Sets local configured site data.</summary>
         static void setSiteData(uint32_t netId, uint8_t siteId, uint8_t channelId, uint32_t channelNo);
         /// <summary>Sets TSCC Aloha configuration.</summary>
@@ -184,6 +186,8 @@ namespace dmr
         bool m_verbose;
         bool m_debug;
 
+        static Control* m_dmr;
+
         static uint32_t m_colorCode;
 
         static SiteData m_siteData;
@@ -200,6 +204,7 @@ namespace dmr
         static lookups::IdenTableLookup* m_idenTable;
         static lookups::RadioIdLookup* m_ridLookup;
         static lookups::TalkgroupIdLookup* m_tidLookup;
+        static lookups::AffiliationLookup* m_affiliations;
 
         static lookups::IdenTable m_idenEntry;
 
@@ -220,6 +225,8 @@ namespace dmr
         static uint8_t m_id2;
         static bool m_voice2;
 
+        static bool m_verifyReg;
+
         static uint16_t m_tsccCnt;
 
         static uint8_t m_alohaNRandWait;
diff --git a/dmr/lc/CSBK.h b/dmr/lc/CSBK.h
index 8a6ac1c2..20a0f953 100644
--- a/dmr/lc/CSBK.h
+++ b/dmr/lc/CSBK.h
@@ -122,7 +122,7 @@ namespace dmr
             /// <summary>Response information.</summary>
             __PROPERTY(uint8_t, response, Response);
             /// <summary>Reason type.</summary>
-            __PROPERTY(uint8_t, reason, reason);
+            __PROPERTY(uint8_t, reason, Reason);
 
             /// <summary>Broadcast Announcment Type.</summary>
             __PROPERTY(uint8_t, anncType, AnncType);
diff --git a/dmr/packet/ControlSignaling.cpp b/dmr/packet/ControlSignaling.cpp
index 3d3b8265..92063d66 100644
--- a/dmr/packet/ControlSignaling.cpp
+++ b/dmr/packet/ControlSignaling.cpp
@@ -66,6 +66,46 @@ using namespace dmr::packet;
         }                                                                               \
     }
 
+// Make sure control data is supported.
+#define IS_SUPPORT_CONTROL_CHECK(_PCKT_STR, _PCKT, _SRCID)                              \
+    if (!m_slot->m_dmr->getTSCCSlot()->m_enableTSCC) {                                  \
+        LogWarning(LOG_RF, "DMR Slot %u, " _PCKT_STR " denial, unsupported service, srcId = %u", m_slot->m_slotNo, _SRCID); \
+        writeRF_CSBK_ACK_RSP(TS_DENY_RSN_SYS_UNSUPPORTED_SVC, _PCKT);                   \
+        return false;                                                                   \
+    }
+
+// Validate the source RID.
+#define VALID_SRCID(_PCKT_STR, _PCKT, _SRCID, _RSN)                                     \
+    if (!acl::AccessControl::validateSrcId(_SRCID)) {                                   \
+        LogWarning(LOG_RF, "DMR Slot %u, " _PCKT_STR " denial, RID rejection, srcId = %u", m_slot->m_slotNo, _SRCID); \
+        writeRF_CSBK_ACK_RSP(_RSN, _PCKT);                                              \
+        return false;                                                                   \
+    }
+
+// Validate the target RID.
+#define VALID_DSTID(_PCKT_STR, _PCKT, _DSTID, _RSN)                                     \
+    if (!acl::AccessControl::validateSrcId(_DSTID)) {                                   \
+        LogWarning(LOG_RF, "DMR Slot %u, " _PCKT_STR " denial, RID rejection, dstId = %u", m_slot->m_slotNo, _DSTID); \
+        writeRF_CSBK_ACK_RSP(_RSN, _PCKT);                                              \
+        return false;                                                                   \
+    }
+
+// Validate the talkgroup ID.
+#define VALID_TGID(_PCKT_STR, _PCKT, _DSTID, _RSN)                                      \
+    if (!acl::AccessControl::validateTGId(_DSTID)) {                                    \
+        LogWarning(LOG_RF, "DMR Slot %u, " _PCKT_STR " denial, TGID rejection, dstId = %u", m_slot->m_slotNo, _DSTID); \
+        writeRF_CSBK_ACK_RSP(_RSN, _PCKT);                                              \
+        return false;                                                                   \
+    }
+
+// Verify the source RID is registered.
+#define VERIFY_SRCID_REG(_PCKT_STR, _PCKT, _SRCID, _RSN)                                \
+    if (!m_slot->m_affiliations->isUnitReg(_SRCID) && m_slot->m_verifyReg) {            \
+        LogWarning(LOG_RF, "DMR Slot %u, " _PCKT_STR " denial, RID not registered, srcId = %u", m_slot->m_slotNo, _SRCID); \
+        writeRF_CSBK_ACK_RSP(_RSN, _PCKT);                                              \
+        return false;                                                                   \
+    }
+
 // ---------------------------------------------------------------------------
 //  Public Class Members
 // ---------------------------------------------------------------------------
@@ -147,11 +187,38 @@ bool ControlSignaling::process(uint8_t* data, uint32_t len)
                 ::ActivityLog("DMR", true, "Slot %u call alert request from %u to %u", m_slot->m_slotNo, srcId, dstId);
             } else {
                 handled = true;
-                
+
                 if (m_verbose) {
                     LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_RAND (Random Access), emerg = %u, prio = %u, serviceType = %02X, serviceData = %02X, srcId = %u, dstId = %u",
                         m_slot->m_slotNo, csbk.getEmergency(), csbk.getPriority(), csbk.getServiceType(), csbk.getServiceData(), csbk.getSrcId(), csbk.getDstId());
                 }
+
+                switch (csbk.getServiceType()) {
+                case SVC_KIND_IND_VOICE_CALL:
+                    // TODO TODO TODO
+                    break;
+                case SVC_KIND_GRP_VOICE_CALL:
+                    // TODO TODO TODO
+                    break;
+                case SVC_KIND_IND_DATA_CALL:
+                case SVC_KIND_IND_UDT_DATA_CALL:
+                    // TODO TODO TODO
+                    break;
+                case SVC_KIND_GRP_DATA_CALL:
+                case SVC_KIND_GRP_UDT_DATA_CALL:
+                    // TODO TODO TODO
+                    break;
+                case SVC_KIND_REG_SVC:
+                    // make sure control data is supported
+                    IS_SUPPORT_CONTROL_CHECK("DT_CSBK, CSBKO_RAND (Random Access), SVC_KIND_REG_SVC (Registration Service)", SVC_KIND_REG_SVC, srcId);
+
+                    writeRF_CSBK_U_Reg_Rsp(srcId);
+                    break;
+                default:
+                    LogWarning(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_RAND (Random Access), unhandled service, serviceType = %02X", m_slot->m_slotNo, csbk.getServiceType());
+                    // should we drop the CSBK and not repeat it?
+                    break;
+                }
             }
             break;
         case CSBKO_ACK_RSP:
@@ -212,13 +279,13 @@ bool ControlSignaling::process(uint8_t* data, uint32_t len)
         }
 
         if (!handled) {
-            // Regenerate the CSBK data
+            // regenerate the CSBK data
             csbk.encode(data + 2U);
 
-            // Regenerate the Slot Type
+            // regenerate the Slot Type
             slotType.encode(data + 2U);
 
-            // Convert the Data Sync to be from the BS or MS as needed
+            // convert the Data Sync to be from the BS or MS as needed
             Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
 
             m_slot->m_rfSeqNo = 0U;
@@ -356,16 +423,16 @@ void ControlSignaling::processNetwork(const data::Data & dmrData)
         }
 
         if (!handled) {
-            // Regenerate the CSBK data
+            // regenerate the CSBK data
             csbk.encode(data + 2U);
 
-            // Regenerate the Slot Type
+            // regenerate the Slot Type
             SlotType slotType;
             slotType.decode(data + 2U);
             slotType.setColorCode(m_slot->m_colorCode);
             slotType.encode(data + 2U);
 
-            // Convert the Data Sync to be from the BS or MS as needed
+            // convert the Data Sync to be from the BS or MS as needed
             Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
 
             data[0U] = modem::TAG_DATA;
@@ -374,19 +441,19 @@ void ControlSignaling::processNetwork(const data::Data & dmrData)
             if (csbko == CSBKO_PRECCSBK && csbk.getDataContent()) {
                 uint32_t cbf = NO_PREAMBLE_CSBK + csbk.getCBF() - 1U;
                 for (uint32_t i = 0U; i < NO_PREAMBLE_CSBK; i++, cbf--) {
-                    // Change blocks to follow
+                    // change blocks to follow
                     csbk.setCBF(cbf);
 
-                    // Regenerate the CSBK data
+                    // regenerate the CSBK data
                     csbk.encode(data + 2U);
 
-                    // Regenerate the Slot Type
+                    // regenerate the Slot Type
                     SlotType slotType;
                     slotType.decode(data + 2U);
                     slotType.setColorCode(m_slot->m_colorCode);
                     slotType.encode(data + 2U);
 
-                    // Convert the Data Sync to be from the BS or MS as needed
+                    // convert the Data Sync to be from the BS or MS as needed
                     Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
 
                     m_slot->addFrame(data, true);
@@ -397,7 +464,7 @@ void ControlSignaling::processNetwork(const data::Data & dmrData)
         }
     }
     else {
-        // Unhandled data type
+        // unhandled data type
         LogWarning(LOG_NET, "DMR Slot %u, unhandled network data, type = $%02X", m_slot->m_slotNo, dataType);
     }
 }
@@ -426,13 +493,6 @@ void ControlSignaling::writeRF_Ext_Func(uint32_t func, uint32_t arg, uint32_t ds
         ::ActivityLog("DMR", true, "Slot %u radio uninhibit request from %u to %u", m_slot->m_slotNo, arg, dstId);
     }
 
-    uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
-    ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
-
-    SlotType slotType;
-    slotType.setColorCode(m_slot->m_colorCode);
-    slotType.setDataType(DT_CSBK);
-
     lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
     csbk.setVerbose(m_dumpCSBKData);
     csbk.setCSBKO(CSBKO_EXT_FNCT);
@@ -443,22 +503,7 @@ void ControlSignaling::writeRF_Ext_Func(uint32_t func, uint32_t arg, uint32_t ds
     csbk.setSrcId(arg);
     csbk.setDstId(dstId);
 
-    // Regenerate the CSBK data
-    csbk.encode(data + 2U);
-
-    // Regenerate the Slot Type
-    slotType.encode(data + 2U);
-
-    // Convert the Data Sync to be from the BS or MS as needed
-    Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
-
-    m_slot->m_rfSeqNo = 0U;
-
-    data[0U] = modem::TAG_DATA;
-    data[1U] = 0x00U;
-
-    if (m_slot->m_duplex)
-        m_slot->addFrame(data);
+    writeRF_CSBK(csbk);
 }
 
 /// <summary>
@@ -475,13 +520,6 @@ void ControlSignaling::writeRF_Call_Alrt(uint32_t srcId, uint32_t dstId)
 
     ::ActivityLog("DMR", true, "Slot %u call alert request from %u to %u", m_slot->m_slotNo, srcId, dstId);
 
-    uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
-    ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
-
-    SlotType slotType;
-    slotType.setColorCode(m_slot->m_colorCode);
-    slotType.setDataType(DT_CSBK);
-
     lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
     csbk.setVerbose(m_dumpCSBKData);
     csbk.setCSBKO(CSBKO_RAND);
@@ -491,22 +529,7 @@ void ControlSignaling::writeRF_Call_Alrt(uint32_t srcId, uint32_t dstId)
     csbk.setSrcId(srcId);
     csbk.setDstId(dstId);
 
-    // Regenerate the CSBK data
-    csbk.encode(data + 2U);
-
-    // Regenerate the Slot Type
-    slotType.encode(data + 2U);
-
-    // Convert the Data Sync to be from the BS or MS as needed
-    Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
-
-    m_slot->m_rfSeqNo = 0U;
-
-    data[0U] = modem::TAG_DATA;
-    data[1U] = 0x00U;
-
-    if (m_slot->m_duplex)
-        m_slot->addFrame(data);
+    writeRF_CSBK(csbk);
 }
 
 // ---------------------------------------------------------------------------
@@ -539,14 +562,12 @@ ControlSignaling::~ControlSignaling()
 }
 
 /// <summary>
-/// Helper to write a TSCC Aloha broadcast packet on the RF interface.
+/// Helper to write a CSBK packet.
 /// </summary>
-void ControlSignaling::writeRF_TSCC_Aloha()
+/// <param name="csbk"></param>
+/// <param name="clearBeforeWrite"></param>
+void ControlSignaling::writeRF_CSBK(lc::CSBK csbk, bool clearBeforeWrite)
 {
-    if (m_debug) {
-        LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_ALOHA (Aloha)", m_slot->m_slotNo);
-    }
-
     uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
     ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
 
@@ -554,14 +575,6 @@ void ControlSignaling::writeRF_TSCC_Aloha()
     slotType.setColorCode(m_slot->m_colorCode);
     slotType.setDataType(DT_CSBK);
 
-    lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
-    csbk.setVerbose(m_dumpCSBKData);
-    csbk.setCSBKO(CSBKO_ALOHA);
-    csbk.setFID(FID_ETSI);
-
-    csbk.setNRandWait(m_slot->m_alohaNRandWait);
-    csbk.setBackoffNo(m_slot->m_alohaBackOff);
-
     // Regenerate the CSBK data
     csbk.encode(data + 2U);
 
@@ -576,10 +589,94 @@ void ControlSignaling::writeRF_TSCC_Aloha()
     data[0U] = modem::TAG_DATA;
     data[1U] = 0x00U;
 
+    if (clearBeforeWrite) {
+        if (m_slot->m_slotNo == 1U)
+            m_slot->m_modem->clearDMRData1();
+        if (m_slot->m_slotNo == 2U)
+            m_slot->m_modem->clearDMRData2();
+        m_slot->m_queue.clear();
+    }
+
     if (m_slot->m_duplex)
         m_slot->addFrame(data);
 }
 
+/// <summary>
+/// Helper to write a deny packet.
+/// </summary>
+/// <param name="reason"></param>
+/// <param name="service"></param>
+void ControlSignaling::writeRF_CSBK_ACK_RSP(uint8_t reason, uint8_t service)
+{
+    lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
+    csbk.setVerbose(m_dumpCSBKData);
+    csbk.setCSBKO(CSBKO_ACK_RSP);
+    csbk.setFID(FID_ETSI);
+
+    csbk.setReason(reason);
+
+    writeRF_CSBK(csbk);
+}
+
+/// <summary>
+/// Helper to write a unit registration response packet.
+/// </summary>
+/// <param name="srcId"></param>
+void ControlSignaling::writeRF_CSBK_U_Reg_Rsp(uint32_t srcId)
+{
+    lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
+    csbk.setVerbose(m_dumpCSBKData);
+    csbk.setCSBKO(CSBKO_ACK_RSP);
+    csbk.setFID(FID_ETSI);
+
+    csbk.setReason(TS_ACK_RSN_REG);
+
+    // validate the source RID
+    if (!acl::AccessControl::validateSrcId(srcId)) {
+        LogWarning(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_RAND (Random Access), SVC_KIND_REG_SVC (Registration Service), denial, RID rejection, srcId = %u", m_slot->m_slotNo, srcId);
+        ::ActivityLog("DMR", true, "unit registration request from %u denied", srcId);
+        csbk.setReason(TS_DENY_RSN_REG_DENIED);
+    }
+
+    if (csbk.getReason() == TS_ACK_RSN_REG) {
+        if (m_verbose) {
+            LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_RAND (Random Access), SVC_KIND_REG_SVC (Registration Service), srcId = %u", m_slot->m_slotNo, srcId);
+        }
+
+        ::ActivityLog("DMR", true, "unit registration request from %u", srcId);
+
+        // update dynamic unit registration table
+        if (!m_slot->m_affiliations->isUnitReg(srcId)) {
+            m_slot->m_affiliations->unitReg(srcId);
+        }
+    }
+
+    csbk.setSrcId(srcId);
+    csbk.setDstId(srcId);
+
+    writeRF_CSBK(csbk);
+}
+
+/// <summary>
+/// Helper to write a TSCC Aloha broadcast packet on the RF interface.
+/// </summary>
+void ControlSignaling::writeRF_TSCC_Aloha()
+{
+    if (m_debug) {
+        LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_ALOHA (Aloha)", m_slot->m_slotNo);
+    }
+
+    lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
+    csbk.setVerbose(m_dumpCSBKData);
+    csbk.setCSBKO(CSBKO_ALOHA);
+    csbk.setFID(FID_ETSI);
+
+    csbk.setNRandWait(m_slot->m_alohaNRandWait);
+    csbk.setBackoffNo(m_slot->m_alohaBackOff);
+
+    writeRF_CSBK(csbk);
+}
+
 /// <summary>
 /// Helper to write a TSCC Ann-Wd broadcast packet on the RF interface.
 /// </summary>
@@ -594,10 +691,6 @@ void ControlSignaling::writeRF_TSCC_Bcast_Ann_Wd(uint32_t channelNo, bool annWd)
 
     m_slot->m_rfSeqNo = 0U;
 
-    SlotType slotType;
-    slotType.setColorCode(m_slot->m_colorCode);
-    slotType.setDataType(DT_CSBK);
-
     lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
     csbk.setCdef(false);
     csbk.setVerbose(m_dumpCSBKData);
@@ -608,23 +701,7 @@ void ControlSignaling::writeRF_TSCC_Bcast_Ann_Wd(uint32_t channelNo, bool annWd)
     csbk.setLogicalCh1(channelNo);
     csbk.setAnnWdCh1(annWd);
 
-    uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
-    ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
-
-    // Regenerate the CSBK data
-    csbk.encode(data + 2U);
-
-    // Regenerate the Slot Type
-    slotType.encode(data + 2U);
-
-    // Convert the Data Sync to be from the BS or MS as needed
-    Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
-
-    data[0U] = modem::TAG_DATA;
-    data[1U] = 0x00U;
-
-    if (m_slot->m_duplex)
-        m_slot->addFrame(data);
+    writeRF_CSBK(csbk);
 }
 
 /// <summary>
@@ -636,13 +713,6 @@ void ControlSignaling::writeRF_TSCC_Bcast_Sys_Parm()
         LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_BROADCAST (Broadcast), BCAST_ANNC_SITE_PARMS (Announce Site Parms)", m_slot->m_slotNo);
     }
 
-    uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
-    ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
-
-    SlotType slotType;
-    slotType.setColorCode(m_slot->m_colorCode);
-    slotType.setDataType(DT_CSBK);
-
     lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
     csbk.setVerbose(m_dumpCSBKData);
     csbk.setCSBKO(CSBKO_BROADCAST);
@@ -650,22 +720,7 @@ void ControlSignaling::writeRF_TSCC_Bcast_Sys_Parm()
 
     csbk.setAnncType(BCAST_ANNC_SITE_PARMS);
 
-    // Regenerate the CSBK data
-    csbk.encode(data + 2U);
-
-    // Regenerate the Slot Type
-    slotType.encode(data + 2U);
-
-    // Convert the Data Sync to be from the BS or MS as needed
-    Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
-
-    m_slot->m_rfSeqNo = 0U;
-
-    data[0U] = modem::TAG_DATA;
-    data[1U] = 0x00U;
-
-    if (m_slot->m_duplex)
-        m_slot->addFrame(data);
+    writeRF_CSBK(csbk);
 }
 
 /// <summary>
@@ -677,32 +732,10 @@ void ControlSignaling::writeRF_TSCC_Git_Hash()
         LogMessage(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_DVM_GIT_HASH (DVM Git Hash)", m_slot->m_slotNo);
     }
 
-    uint8_t data[DMR_FRAME_LENGTH_BYTES + 2U];
-    ::memset(data + 2U, 0x00U, DMR_FRAME_LENGTH_BYTES);
-
-    SlotType slotType;
-    slotType.setColorCode(m_slot->m_colorCode);
-    slotType.setDataType(DT_CSBK);
-
     lc::CSBK csbk = lc::CSBK(m_slot->m_siteData, m_slot->m_idenEntry, m_slot->m_dumpCSBKData);
     csbk.setVerbose(m_dumpCSBKData);
     csbk.setCSBKO(CSBKO_DVM_GIT_HASH);
     csbk.setFID(FID_DVM);
 
-    // Regenerate the CSBK data
-    csbk.encode(data + 2U);
-
-    // Regenerate the Slot Type
-    slotType.encode(data + 2U);
-
-    // Convert the Data Sync to be from the BS or MS as needed
-    Sync::addDMRDataSync(data + 2U, m_slot->m_duplex);
-
-    m_slot->m_rfSeqNo = 0U;
-
-    data[0U] = modem::TAG_DATA;
-    data[1U] = 0x00U;
-
-    if (m_slot->m_duplex)
-        m_slot->addFrame(data);
+    writeRF_CSBK(csbk);
 }
diff --git a/dmr/packet/ControlSignaling.h b/dmr/packet/ControlSignaling.h
index 3b2f7a0b..44c35d6c 100644
--- a/dmr/packet/ControlSignaling.h
+++ b/dmr/packet/ControlSignaling.h
@@ -35,6 +35,7 @@
 #include "dmr/data/Data.h"
 #include "dmr/data/EmbeddedData.h"
 #include "dmr/lc/LC.h"
+#include "dmr/lc/CSBK.h"
 #include "modem/Modem.h"
 #include "network/BaseNetwork.h"
 #include "RingBuffer.h"
@@ -86,6 +87,14 @@ namespace dmr
             /// <summary>Finalizes a instance of the ControlSignaling class.</summary>
             ~ControlSignaling();
 
+            /// <summary>Helper to write a CSBK packet.</summary>
+            void writeRF_CSBK(lc::CSBK csbk, bool clearBeforeWrite = false);
+
+            /// <summary>Helper to write a ACK RSP packet.</summary>
+            void writeRF_CSBK_ACK_RSP(uint8_t reason, uint8_t service);
+            /// <summary>Helper to write a unit registration response packet.</summary>
+            void writeRF_CSBK_U_Reg_Rsp(uint32_t srcId);
+
             /// <summary>Helper to write a TSCC Aloha broadcast packet on the RF interface.</summary>
             void writeRF_TSCC_Aloha();
             /// <summary>Helper to write a TSCC Ann-Wd broadcast packet on the RF interface.</summary>
diff --git a/nxdn/packet/Trunk.cpp b/nxdn/packet/Trunk.cpp
index 5487f2fe..498a772d 100644
--- a/nxdn/packet/Trunk.cpp
+++ b/nxdn/packet/Trunk.cpp
@@ -415,7 +415,7 @@ void Trunk::writeRF_Message(bool noNetwork, bool clearBeforeWrite)
         writeNetwork(data, NXDN_FRAME_LENGTH_BYTES + 2U);
 
     if (clearBeforeWrite) {
-        m_nxdn->m_modem->clearP25Data();
+        m_nxdn->m_modem->clearNXDNData();
         m_nxdn->m_queue.clear();
     }