diff --git a/P25/lc/TSBKBase.cs b/P25/lc/TSBKBase.cs
new file mode 100644
index 0000000..ff7a9d2
--- /dev/null
+++ b/P25/lc/TSBKBase.cs
@@ -0,0 +1,130 @@
+using System;
+
+using fnecore.EDAC;
+
+namespace fnecore.P25.LC
+{
+    /// <summary>
+    /// Base TSBK Encode/Decode class
+    /// </summary>
+    public abstract class TSBKBase
+    {
+        protected bool LastBlock;
+        protected byte Lco;
+        protected byte MfId;
+
+        /// <summary>
+        /// Creates an instance of <see cref="TSBKBase"/>
+        /// </summary>
+        protected TSBKBase()
+        {
+            MfId = P25Defines.P25_MFG_STANDARD;
+        }
+
+        /// <summary>
+        /// Decode a TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="payload"></param>
+        /// <param name="rawTSBK"></param>
+        /// <returns></returns>
+        public virtual bool Decode(byte[] data, ref byte[] payload, bool rawTSBK)
+        {
+            byte[] tsbk = new byte[P25Defines.P25_TSBK_LENGTH_BYTES];
+            FneUtils.Memset(tsbk, 0x00, tsbk.Length);
+
+            if (rawTSBK)
+            {
+                Array.Copy(data, tsbk, P25Defines.P25_TSBK_LENGTH_BYTES);
+
+                if (!CRC.CheckCCITT162(tsbk, P25Defines.P25_TSBK_LENGTH_BYTES))
+                {
+                    if ((tsbk[P25Defines.P25_TSBK_LENGTH_BYTES - 2U] != 0x00U) && (tsbk[P25Defines.P25_TSBK_LENGTH_BYTES - 1U] != 0x00U))
+                    {
+                        Console.WriteLine("TSBK failed CRC CCITT-162 check");
+                        return false;
+                    }
+                }
+            }
+            else
+            {
+                byte[] raw = new byte[P25Defines.P25_TSBK_FEC_LENGTH_BYTES];
+                P25Interleaver.Decode(data, ref raw, 114, 318);
+
+                EDAC.Trellis trellis = new EDAC.Trellis();
+                if (!trellis.Decode12(raw, ref tsbk))
+                {
+                    Console.WriteLine("TSBK Failed Trellis decode");
+                    return false;
+                }
+
+                if (!CRC.CheckCCITT162(tsbk, P25Defines.P25_TSBK_LENGTH_BYTES))
+                {
+                    Console.WriteLine("TSBK Failed CRC check after Trellis");
+                    return false;
+                }
+            }
+
+            Lco = (byte)(tsbk[0] & 0x3F);                // LCO 
+            LastBlock = (tsbk[0] & 0x80) == 0x80;        // Last Block Marker
+            MfId = tsbk[1];                              // Manufacturer ID
+
+            Array.Copy(tsbk, 1, payload, 0, P25Defines.P25_TSBK_LENGTH_BYTES - 4);
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode a TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="payload"></param>
+        /// <param name="rawTSBK"></param>
+        /// <param name="noTrellis"></param>
+        public virtual void Encode(ref byte[] data, ref byte[] payload, bool rawTSBK, bool noTrellis)
+        {
+            byte[] tsbk = new byte[P25Defines.P25_TSBK_LENGTH_BYTES];
+
+            FneUtils.Memset(tsbk, 0x00, tsbk.Length);
+
+            Array.Copy(payload, 0, tsbk, 2, P25Defines.P25_TSBK_LENGTH_BYTES - 4);
+
+            tsbk[0] = Lco;                                      // LCO
+            tsbk[0] |= LastBlock ? (byte)0x80 : (byte)0x00;     // Last Block Marker
+            tsbk[1] = MfId;                                     // Manufacturer ID
+
+            CRC.AddCCITT162(ref tsbk, P25Defines.P25_TSBK_LENGTH_BYTES);
+
+            byte[] raw = new byte[P25Defines.P25_TSBK_FEC_LENGTH_BYTES];
+            FneUtils.Memset(raw, 0x00, raw.Length);
+
+            EDAC.Trellis trellis = new EDAC.Trellis();
+            trellis.Encode12(tsbk, ref raw);
+
+            if (rawTSBK)
+            {
+                if (noTrellis)
+                {
+                    Array.Copy(tsbk, 0, data, 0, P25Defines.P25_TSBK_LENGTH_BYTES);
+                }
+                else
+                {
+                    Array.Copy(raw, 0, data, 0, P25Defines.P25_TSBK_FEC_LENGTH_BYTES);
+                }
+            }
+            else
+            {
+                P25Interleaver.Encode(raw, ref data, 114, 318);
+            }
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <returns></returns>
+        public override string ToString()
+        {
+            return "UNKNOWN TSBK";
+        }
+    } // public abstract class TSBKBase
+} // namespace fnecore.P25.LC
diff --git a/P25/lc/tsbk/IOSP_ACK_RSP.cs b/P25/lc/tsbk/IOSP_ACK_RSP.cs
new file mode 100644
index 0000000..a35403a
--- /dev/null
+++ b/P25/lc/tsbk/IOSP_ACK_RSP.cs
@@ -0,0 +1,91 @@
+namespace fnecore.P25.LC.TSBK
+{
+    /// <summary>
+    /// IOSP_ACK_RSP TSBK
+    /// </summary>
+    public class IOSP_ACK_RSP : TSBKBase
+    {
+        public uint DstId;
+        public uint SrcId;
+        public uint SysId;
+        public uint Wacn;
+        public bool Aiv;
+        public bool ExtendedAddr;
+        public byte Service;
+
+        /// <summary>
+        /// Creates an instance of <see cref="IOSP_ACK_RSP"/>
+        /// </summary>
+        /// <param name="dstId"></param>
+        /// <param name="srcId"></param>
+        /// <param name="aivFlag"></param>
+        /// <param name="service"></param>
+        public IOSP_ACK_RSP(uint dstId, uint srcId, bool aivFlag, byte service)
+        {
+            DstId = dstId;
+            SrcId = srcId;
+            Aiv = aivFlag;
+            Service = service;
+            Lco = P25Defines.TSBK_IOSP_ACK_RSP;
+        }
+
+        /// <summary>
+        /// Decode ACK_RSP TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="rawTSBK"></param>
+        /// <returns></returns>
+        public bool Decode(byte[] data, bool rawTSBK)
+        {
+            byte[] tsbk = new byte[P25Defines.P25_TSBK_LENGTH_BYTES];
+            FneUtils.Memset(tsbk, 0x00, tsbk.Length);
+
+            bool ret = base.Decode(data, ref tsbk, rawTSBK);
+            if (!ret)
+                return false;
+
+            ulong tsbkValue = FneUtils.ToUInt64(tsbk, 0);
+
+            Aiv = ((tsbkValue >> 56) & 0x80U) == 0x80U;     // Additional Info Flag
+            Service = (byte)((tsbkValue >> 56) & 0x3FU);    // Service Type
+
+            DstId = FneUtils.Bytes3ToUInt32(tsbk, 3);       // Target Radio Address
+            SrcId = FneUtils.Bytes3ToUInt32(tsbk, 0);       // Source Radio Address
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode ACK_RSP TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="payload"></param>
+        /// <param name="rawTSBK"></param>
+        /// <param name="noTrellis"></param>
+        public override void Encode(ref byte[] data, ref byte[] payload, bool rawTSBK, bool noTrellis)
+        {
+            ulong tsbkValue = 0;
+
+            tsbkValue = Service & 0x3FU;                    // Service Type
+            tsbkValue |= Aiv ? 0x80UL : 0x00UL;             // Additional Info Flag
+            tsbkValue |= ExtendedAddr ? 0x40UL : 0x00UL;    // Extended Addressing Flag
+
+            if (Aiv && ExtendedAddr)
+            {
+                tsbkValue = (tsbkValue << 20) + Wacn;       // Network ID
+                tsbkValue = (tsbkValue << 12) + SysId;      // System ID
+            }
+            else
+            {
+                tsbkValue = (tsbkValue << 32) + DstId;      // Target Radio Address
+            }
+
+            tsbkValue = (tsbkValue << 24) + SrcId;          // Source Radio Address
+
+            FneUtils.Memset(payload, 0x00, payload.Length);
+            FneUtils.WriteBytes(tsbkValue, ref payload, 0);
+
+            base.Encode(ref data, ref payload, rawTSBK, noTrellis);
+        }
+    } // public class IOSP_ACK_RSP
+} // namespace fnecore.P25.LC.TSBK
diff --git a/P25/lc/tsbk/IOSP_CALL_ALRT.cs b/P25/lc/tsbk/IOSP_CALL_ALRT.cs
new file mode 100644
index 0000000..36caa51
--- /dev/null
+++ b/P25/lc/tsbk/IOSP_CALL_ALRT.cs
@@ -0,0 +1,63 @@
+namespace fnecore.P25.LC.TSBK
+{
+    /// <summary>
+    /// IOSP_CALL_ALRT TSBK
+    /// </summary>
+    public class IOSP_CALL_ALRT : TSBKBase
+    {
+        public uint DstId;
+        public uint SrcId;
+
+        /// <summary>
+        /// Creates an instance of <see cref="IOSP_CALL_ALRT"/>
+        /// </summary>
+        /// <param name="dstId"></param>
+        /// <param name="srcId"></param>
+        public IOSP_CALL_ALRT(uint dstId, uint srcId)
+        {
+            DstId = dstId;
+            SrcId = srcId;
+            Lco = P25Defines.TSBK_IOSP_CALL_ALRT;
+        }
+
+        /// <summary>
+        /// Decode CALL_ALRT TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="rawTSBK"></param>
+        /// <returns></returns>
+        public bool Decode(byte[] data, bool rawTSBK)
+        {
+            byte[] tsbk = new byte[P25Defines.P25_TSBK_LENGTH_BYTES];
+            FneUtils.Memset(tsbk, 0x00, tsbk.Length);
+
+            bool ret = base.Decode(data, ref tsbk, rawTSBK);
+            if (!ret)
+                return false;
+
+            DstId = FneUtils.Bytes3ToUInt32(tsbk, 3);       // Target Radio Address
+            SrcId = FneUtils.Bytes3ToUInt32(tsbk, 0);       // Source Radio Address
+
+            return true;
+        }
+
+        /// <summary>
+        /// Encode CALL_ALRT TSBK
+        /// </summary>
+        /// <param name="data"></param>
+        /// <param name="payload"></param>
+        /// <param name="rawTSBK"></param>
+        /// <param name="noTrellis"></param>
+        public override void Encode(ref byte[] data, ref byte[] payload, bool rawTSBK, bool noTrellis)
+        {
+            ulong tsbkValue = 0;
+            tsbkValue = (tsbkValue << 40) + DstId;      // Target Radio Address
+            tsbkValue = (tsbkValue << 24) + SrcId;      // Source Radio Address
+
+            FneUtils.Memset(payload, 0x00, payload.Length);
+            FneUtils.WriteBytes(tsbkValue, ref payload, 0);
+
+            base.Encode(ref data, ref payload, rawTSBK, noTrellis);
+        }
+    } // public class IOSP_CALL_ALRT
+} // namespace fnecore.P25.LC.TSBK