diff --git a/NmraDcc.cpp b/NmraDcc.cpp
index e1dbf3d..9844b90 100644
--- a/NmraDcc.cpp
+++ b/NmraDcc.cpp
@@ -597,17 +597,11 @@ void ExternalInterruptHandler(void)
 }
 
 void ackCV(void)
-{
-  if( notifyCVAck )
+{  // create the ack pulse only in service mode
+  if( notifyCVAck && DccProcState.inServiceMode )
     notifyCVAck() ;
 }
 
-void ackAdvancedCV(void)
-{
-  if( notifyAdvancedCVAck && (DccProcState.cv29Value & CV29_ADV_ACK) )
-    notifyAdvancedCVAck() ;
-}
-
 
 uint8_t readEEPROM( unsigned int CV ) {
     return EEPROM.read(CV) ;
@@ -668,6 +662,8 @@ uint8_t writeCV( unsigned int CV, uint8_t Value)
   {
     case CV_29_CONFIG:
       // copy addressmode Bit to Flags
+      Value = Value &  ~CV29_RailCom_ENABLE;   // Bidi (RailCom) Bit must not be enabled, 
+                                            // because you cannot build a Bidi decoder with this lib.
       DccProcState.cv29Value = Value;
       DccProcState.Flags = ( DccProcState.Flags & ~FLAGS_CV29_BITS) | (Value & FLAGS_CV29_BITS);
       // no break, because myDccAdress must also be reset
@@ -730,7 +726,7 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
       if( validCV( CVAddr, 1 ) )
       {
         if( writeCV( CVAddr, Value ) == Value )
-          ackAdvancedCV();
+          ackCV();
       }
     }
 
@@ -739,7 +735,7 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
       if( validCV( CVAddr, 0 ) )
       {
         if( readCV( CVAddr ) == Value )
-          ackAdvancedCV();
+          ackCV();
       }
     }
   }
@@ -764,7 +760,7 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
           tempValue &= ~BitMask ;  // Turn the Bit Off
 
         if( writeCV( CVAddr, tempValue ) == tempValue )
-          ackAdvancedCV() ;
+          ackCV() ;
       }
     }
 
@@ -776,12 +772,12 @@ void processDirectOpsOperation( uint8_t Cmd, uint16_t CVAddr, uint8_t Value )
         if( BitValue ) 
         {
           if( tempValue & BitMask )
-            ackAdvancedCV() ;
+            ackCV() ;
         }
         else
         {
           if( !( tempValue & BitMask)  )
-            ackAdvancedCV() ;
+            ackCV() ;
         }
       }
     }
diff --git a/NmraDcc.h b/NmraDcc.h
index 0ed764f..3e89ea0 100644
--- a/NmraDcc.h
+++ b/NmraDcc.h
@@ -49,7 +49,7 @@
 #ifndef NMRADCC_IS_IN
 #define NMRADCC_IS_IN
 
-#define NMRADCC_VERSION     201     // Version 2.0.1
+#define NMRADCC_VERSION     202     // Version 2.0.2
 
 #define MAX_DCC_MESSAGE_LEN 6    // including XOR-Byte
 
@@ -118,7 +118,7 @@ typedef enum {
     CV29_LOCO_DIR            = 0b00000001,	/** bit 0: Locomotive Direction: "0" = normal, "1" = reversed */
     CV29_F0_LOCATION         = 0b00000010,	/** bit 1: F0 location: "0" = bit 4 in Speed and Direction instructions, "1" = bit 4 in function group one instruction */
     CV29_APS                 = 0b00000100,	/** bit 2: Alternate Power Source (APS) "0" = NMRA Digital only, "1" = Alternate power source set by CV12 */
-    CV29_ADV_ACK             = 0b00001000, 	/** bit 3: ACK, Advanced Acknowledge mode enabled if 1, disabled if 0 */
+    CV29_RailCom_ENABLE      = 0b00001000, 	/** bit 3: BiDi ( RailCom ) is active */
     CV29_SPEED_TABLE_ENABLE  = 0b00010000, 	/** bit 4: STE, Speed Table Enable, "0" = values in CVs 2, 4 and 6, "1" = Custom table selected by CV 25 */
     CV29_EXT_ADDRESSING      = 0b00100000,	/** bit 5: "0" = one byte addressing, "1" = two byte addressing */
     CV29_OUTPUT_ADDRESS_MODE = 0b01000000,	/** bit 6: "0" = Decoder Address Mode "1" = Output Address Mode */
@@ -703,17 +703,8 @@ extern void    notifyCVResetFactoryDefault(void) __attribute__ ((weak));
  *    None
  */
 extern void    notifyCVAck(void) __attribute__ ((weak));
-/*+
- *  notifyAdvancedCVAck() Called when a CV write must be acknowledged via Advanced Acknowledgement.
- *                This callback must send the Advanced Acknowledgement via RailComm.
- *
- *  Inputs:
- *    None
- *                                                                                                        *
- *  Returns:
- *    None
- */
-extern void    notifyAdvancedCVAck(void) __attribute__ ((weak));
+
+
 /*+
  *  notifyServiceMode(bool) Called when state of 'inServiceMode' changes
  *