diff --git a/src/ebusd/bushandler.cpp b/src/ebusd/bushandler.cpp
index 3d972038..1366ba90 100644
--- a/src/ebusd/bushandler.cpp
+++ b/src/ebusd/bushandler.cpp
@@ -46,13 +46,17 @@ const char* getStateCode(BusState state) {
   case bs_skip:       return "skip";
   case bs_ready:      return "ready";
   case bs_sendCmd:    return "send command";
+  case bs_recvCmdCrc: return "receive command CRC";
   case bs_recvCmdAck: return "receive command ACK";
   case bs_recvRes:    return "receive response";
+  case bs_recvResCrc: return "receive response CRC";
   case bs_sendResAck: return "send response ACK";
   case bs_recvCmd:    return "receive command";
   case bs_recvResAck: return "receive response ACK";
+  case bs_sendCmdCrc: return "send command CRC";
   case bs_sendCmdAck: return "send command ACK";
   case bs_sendRes:    return "send response";
+  case bs_sendResCrc: return "send response CRC";
   case bs_sendSyn:    return "send SYN";
   default:            return "unknown";
   }
@@ -181,22 +185,22 @@ bool ActiveBusRequest::notify(result_t result, SymbolString& slave) {
     logDebug(lf_bus, "read res: %s", slave.getDataStr().c_str());
   }
   m_result = result;
-  m_slave.addAll(slave, true);
+  m_slave = slave;
   return false;
 }
 
 void GrabbedMessage::setLastData(SymbolString& master, SymbolString& slave) {
-  m_lastMaster.clear(false);
-  m_lastMaster.addAll(master);
-  m_lastSlave.clear(false);
-  m_lastSlave.addAll(slave);
+  m_lastMaster.clear();
+  m_lastMaster = master;
+  m_lastSlave.clear();
+  m_lastSlave = slave;
   m_count++;
 }
 
 /**
  * Decode the input @a SymbolString with the specified @a DataType and length.
  * @param type the @a DataType.
- * @param input the unescaped @a SymbolString to read the binary value from.
+ * @param input the @a SymbolString to read the binary value from.
  * @param isMaster whether the @a SymbolString is the master part.
  * @param baseOffset the base offset in the @a SymbolString.
  * @param length the number of symbols to read.
@@ -208,7 +212,7 @@ void GrabbedMessage::setLastData(SymbolString& master, SymbolString& slave) {
 bool decodeType(DataType* type, SymbolString *input, bool isMaster, unsigned char baseOffset, unsigned char length,
     unsigned char offsets, ostringstream& output, bool firstOnly = false) {
   bool first = true;
-  string in = input->getDataStr(true, true, baseOffset);
+  string in = input->getDataStr(baseOffset);
   for (unsigned char offset = 0; offset <= offsets; offset++) {
     ostringstream out;
     result_t result = type->readSymbols(*input, isMaster, (unsigned char)(baseOffset+offset), (unsigned char)length,
@@ -352,7 +356,7 @@ result_t BusHandler::readFromBus(Message* message, string inputStr, const unsign
   unsigned char masterAddress = srcAddress == SYN ? m_ownMasterAddress : srcAddress;
   result_t ret = RESULT_EMPTY;
   SymbolString master(true);
-  SymbolString slave(false);
+  SymbolString slave;
   for (unsigned char index = 0; index < message->getCount(); index++) {
     istringstream input(inputStr);
     ret = message->prepareMaster(masterAddress, master, input, UI_FIELD_SEPARATOR, dstAddress, index);
@@ -463,11 +467,13 @@ result_t BusHandler::handleSymbol() {
     break;
 
   case bs_recvCmd:
+  case bs_recvCmdCrc:
   case bs_recvCmdAck:
     timeout = m_slaveRecvTimeout;
     break;
 
   case bs_recvRes:
+  case bs_recvResCrc:
     if (m_response.size() > 0 || m_slaveRecvTimeout > SYN_TIMEOUT) {
       timeout = m_slaveRecvTimeout;
     } else {
@@ -481,28 +487,42 @@ result_t BusHandler::handleSymbol() {
 
   case bs_sendCmd:
     if (m_currentRequest != NULL) {
-      sendSymbol = m_currentRequest->m_master[m_nextSendPos];  // escaped command
+      sendSymbol = m_currentRequest->m_master[m_nextSendPos];  // unescaped command
+      sending = true;
+    }
+    break;
+
+  case bs_sendCmdCrc:
+    if (m_currentRequest != NULL) {
+      sendSymbol = m_crc;
       sending = true;
     }
     break;
 
   case bs_sendResAck:
     if (m_currentRequest != NULL) {
-      sendSymbol = m_responseCrcValid ? ACK : NAK;
+      sendSymbol = m_crcValid ? ACK : NAK;
       sending = true;
     }
     break;
 
   case bs_sendCmdAck:
     if (m_answer) {
-      sendSymbol = m_commandCrcValid ? ACK : NAK;
+      sendSymbol = m_crcValid ? ACK : NAK;
       sending = true;
     }
     break;
 
   case bs_sendRes:
     if (m_answer) {
-      sendSymbol = m_response[m_nextSendPos];  // escaped response
+      sendSymbol = m_response[m_nextSendPos];  // unescaped response
+      sending = true;
+    }
+    break;
+
+  case bs_sendResCrc:
+    if (m_currentRequest != NULL) {
+      sendSymbol = m_crc;
       sending = true;
     }
     break;
@@ -516,6 +536,14 @@ result_t BusHandler::handleSymbol() {
   // send symbol if necessary
   result_t result;
   if (sending) {
+    if (m_state != bs_sendSyn && (sendSymbol == ESC || sendSymbol == SYN)) {
+      if (m_escape) {
+        sendSymbol = sendSymbol == ESC ? 0x00 : 0x01;
+      } else {
+        m_escape = sendSymbol;
+        sendSymbol = ESC;
+      }
+    }
     result = m_device->send(sendSymbol);
     if (result == RESULT_OK) {
       if (m_state == bs_ready) {
@@ -587,7 +615,39 @@ result_t BusHandler::handleSymbol() {
     return setState(bs_ready, m_state == bs_skip ? RESULT_OK : RESULT_ERR_SYN);
   }
 
-  unsigned int headerLen, crcPos;
+  switch (m_state) {
+  case bs_ready:
+  case bs_recvCmd:
+  case bs_recvRes:
+  case bs_sendCmd:
+  case bs_sendRes:
+    SymbolString::updateCrc(m_crc, recvSymbol);
+    break;
+  default:
+    break;
+  }
+
+  if (m_escape) {
+    // check escape/unescape state
+    if (sending) {
+      if (recvSymbol != sendSymbol) {
+        return setState(bs_skip, RESULT_ERR_SYMBOL);
+      }
+      if (sendSymbol == ESC) {
+        return RESULT_OK;
+      }
+      sendSymbol = recvSymbol = m_escape;
+    } else {
+      if (recvSymbol > 0x01) {
+        return setState(bs_skip, RESULT_ERR_ESC);
+      }
+      recvSymbol = recvSymbol == 0x00 ? ESC : SYN;
+    }
+    m_escape = 0;
+  } else if (!sending && recvSymbol == ESC) {
+    m_escape = ESC;
+    return RESULT_OK;
+  }
 
   switch (m_state) {
   case bs_noSignal:
@@ -617,59 +677,55 @@ result_t BusHandler::handleSymbol() {
       }
       setState(m_state, RESULT_ERR_BUS_LOST);  // try again later
     }
-    result = m_command.push_back(recvSymbol, false);  // expect no escaping for master address
-    if (result < RESULT_OK) {
-      return setState(bs_skip, result);
-    }
+    m_command.push_back(recvSymbol);
     m_repeat = false;
     return setState(bs_recvCmd, RESULT_OK);
 
   case bs_recvCmd:
-    headerLen = 4;
-    // header symbols are never escaped
-    crcPos = m_command.size() > headerLen ? headerLen + 1 + m_command[headerLen] : 0xff;
-    result = m_command.push_back(recvSymbol, true, m_command.size() < crcPos);
-    if (result < RESULT_OK) {
-      return setState(bs_skip, result);
-    }
-    if (result == RESULT_OK && crcPos != 0xff && m_command.size() == crcPos + 1) {  // CRC received
-      unsigned char dstAddress = m_command[1];
-      // header symbols are never escaped
-      m_commandCrcValid = m_command[headerLen + 1 + m_command[headerLen]] == m_command.getCRC();
-      if (m_commandCrcValid) {
-        if (dstAddress == BROADCAST) {
-          receiveCompleted();
-          return setState(bs_skip, RESULT_OK);
-        }
-        addSeenAddress(m_command[0]);
-        if (m_answer && (dstAddress == m_ownMasterAddress || dstAddress == m_ownSlaveAddress)) {
-          return setState(bs_sendCmdAck, RESULT_OK);
-        }
-        return setState(bs_recvCmdAck, RESULT_OK);
-      }
-      if (dstAddress == BROADCAST) {
-        return setState(bs_skip, RESULT_ERR_CRC);
-      }
-      if (m_answer && (dstAddress == m_ownMasterAddress || dstAddress == m_ownSlaveAddress)) {
-        return setState(bs_sendCmdAck, RESULT_ERR_CRC);
-      }
-      if (m_repeat) {
-        return setState(bs_skip, RESULT_ERR_CRC);
-      }
-      return setState(bs_recvCmdAck, RESULT_ERR_CRC);
+    m_command.push_back(recvSymbol);
+    if (m_command.isComplete()) {  // all data received
+      return setState(bs_recvCmdCrc, RESULT_OK);
     }
     return RESULT_OK;
 
+  case bs_recvCmdCrc:
+    m_crcValid = recvSymbol == m_crc;
+    if (m_command[1] == BROADCAST) {
+      if (m_crcValid) {
+        receiveCompleted();
+        return setState(bs_skip, RESULT_OK);
+      }
+      return setState(bs_skip, RESULT_ERR_CRC);
+    }
+    if (m_answer) {
+      unsigned char dstAddress = m_command[1];
+      if (dstAddress == m_ownMasterAddress || dstAddress == m_ownSlaveAddress) {
+        if (m_crcValid) {
+          addSeenAddress(m_command[0]);
+          return setState(bs_sendCmdAck, RESULT_OK);
+        }
+        return setState(bs_sendCmdAck, RESULT_ERR_CRC);
+      }
+    }
+    if (m_crcValid) {
+      addSeenAddress(m_command[0]);
+      return setState(bs_recvCmdAck, RESULT_OK);
+    }
+    if (m_repeat) {
+      return setState(bs_skip, RESULT_ERR_CRC);
+    }
+    return setState(bs_recvCmdAck, RESULT_ERR_CRC);
+
   case bs_recvCmdAck:
     if (recvSymbol == ACK) {
-      if (!m_commandCrcValid) {
+      if (!m_crcValid) {
         return setState(bs_skip, RESULT_ERR_ACK);
       }
       if (m_currentRequest != NULL) {
         if (isMaster(m_currentRequest->m_master[1])) {
           return setState(bs_sendSyn, RESULT_OK);
         }
-      } else if (isMaster(m_command[1])) {  // header symbols are never escaped
+      } else if (isMaster(m_command[1])) {
         receiveCompleted();
         return setState(bs_skip, RESULT_OK);
       }
@@ -680,6 +736,7 @@ result_t BusHandler::handleSymbol() {
     if (recvSymbol == NAK) {
       if (!m_repeat) {
         m_repeat = true;
+        m_crc = 0;
         m_nextSendPos = 0;
         m_command.clear();
         if (m_currentRequest != NULL) {
@@ -692,36 +749,34 @@ result_t BusHandler::handleSymbol() {
     return setState(bs_skip, RESULT_ERR_ACK);
 
   case bs_recvRes:
-    headerLen = 0;
-    crcPos = m_response.size() > headerLen ? headerLen + 1 + m_response[headerLen] : 0xff;
-    result = m_response.push_back(recvSymbol, true, m_response.size() < crcPos);
-    if (result < RESULT_OK) {
-      return setState(bs_skip, result);
-    }
-    if (result == RESULT_OK && crcPos != 0xff && m_response.size() == crcPos + 1) {  // CRC received
-      m_responseCrcValid = m_response[headerLen + 1 + m_response[headerLen]] == m_response.getCRC();
-      if (m_responseCrcValid) {
-        if (m_currentRequest != NULL) {
-          return setState(bs_sendResAck, RESULT_OK);
-        }
-        return setState(bs_recvResAck, RESULT_OK);
-      }
-      if (m_repeat) {
-        if (m_currentRequest != NULL) {
-          return setState(bs_sendSyn, RESULT_ERR_CRC);
-        }
-        return setState(bs_skip, RESULT_ERR_CRC);
-      }
-      if (m_currentRequest != NULL) {
-        return setState(bs_sendResAck, RESULT_ERR_CRC);
-      }
-      return setState(bs_recvResAck, RESULT_ERR_CRC);
+    m_response.push_back(recvSymbol);
+    if (m_response.isComplete()) {  // all data received
+      return setState(bs_recvResCrc, RESULT_OK);
     }
     return RESULT_OK;
 
+  case bs_recvResCrc:
+    m_crcValid = recvSymbol == m_crc;
+    if (m_crcValid) {
+      if (m_currentRequest != NULL) {
+        return setState(bs_sendResAck, RESULT_OK);
+      }
+      return setState(bs_recvResAck, RESULT_OK);
+    }
+    if (m_repeat) {
+      if (m_currentRequest != NULL) {
+        return setState(bs_sendSyn, RESULT_ERR_CRC);
+      }
+      return setState(bs_skip, RESULT_ERR_CRC);
+    }
+    if (m_currentRequest != NULL) {
+      return setState(bs_sendResAck, RESULT_ERR_CRC);
+    }
+    return setState(bs_recvResAck, RESULT_ERR_CRC);
+
   case bs_recvResAck:
     if (recvSymbol == ACK) {
-      if (!m_responseCrcValid) {
+      if (!m_crcValid) {
         return setState(bs_skip, RESULT_ERR_ACK);
       }
       receiveCompleted();
@@ -738,54 +793,66 @@ result_t BusHandler::handleSymbol() {
     return setState(bs_skip, RESULT_ERR_ACK);
 
   case bs_sendCmd:
-    if (m_currentRequest != NULL && sending && recvSymbol == sendSymbol) {
-      // successfully sent
-      m_nextSendPos++;
-      if (m_nextSendPos >= m_currentRequest->m_master.size()) {
-        // master data completely sent
-        if (m_currentRequest->m_master[1] == BROADCAST) {
-          return setState(bs_sendSyn, RESULT_OK);
-        }
-        m_commandCrcValid = true;
-        return setState(bs_recvCmdAck, RESULT_OK);
-      }
-      return RESULT_OK;
+    if (!sending || m_currentRequest == NULL) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
     }
-    return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    m_nextSendPos++;
+    if (m_nextSendPos >= m_currentRequest->m_master.size()) {
+      return setState(bs_sendCmdCrc, RESULT_OK);
+    }
+    return RESULT_OK;
 
-  case bs_sendResAck:
-    if (m_currentRequest != NULL && sending && recvSymbol == sendSymbol) {
-      // successfully sent
-      if (!m_responseCrcValid) {
-        if (!m_repeat) {
-          m_repeat = true;
-          m_response.clear();
-          return setState(bs_recvRes, RESULT_ERR_NAK, true);
-        }
-        return setState(bs_sendSyn, RESULT_ERR_ACK);
-      }
+  case bs_sendCmdCrc:
+    if (m_currentRequest->m_master[1] == BROADCAST) {
       return setState(bs_sendSyn, RESULT_OK);
     }
-    return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    m_crcValid = true;
+    return setState(bs_recvCmdAck, RESULT_OK);
+
+  case bs_sendResAck:
+    if (!sending || m_currentRequest == NULL) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    }
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    if (!m_crcValid) {
+      if (!m_repeat) {
+        m_repeat = true;
+        m_response.clear();
+        return setState(bs_recvRes, RESULT_ERR_NAK, true);
+      }
+      return setState(bs_sendSyn, RESULT_ERR_ACK);
+    }
+    return setState(bs_sendSyn, RESULT_OK);
 
   case bs_sendCmdAck:
-    if (sending && m_answer && recvSymbol == sendSymbol) {
-      // successfully sent
-      if (!m_commandCrcValid) {
-        if (!m_repeat) {
-          m_repeat = true;
-          m_command.clear();
-          return setState(bs_recvCmd, RESULT_ERR_NAK, true);
-        }
-        return setState(bs_skip, RESULT_ERR_ACK);
-      }
-      if (isMaster(m_command[1])) {
-        receiveCompleted();  // decode command and store value
-        return setState(bs_skip, RESULT_OK);
+    if (!sending || !m_answer) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    }
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    if (!m_crcValid) {
+      if (!m_repeat) {
+        m_repeat = true;
+        m_crc = 0;
+        m_command.clear();
+        return setState(bs_recvCmd, RESULT_ERR_NAK, true);
       }
+      return setState(bs_skip, RESULT_ERR_ACK);
+    }
+    if (isMaster(m_command[1])) {
+      receiveCompleted();  // decode command and store value
+      return setState(bs_skip, RESULT_OK);
+    }
 
-      m_nextSendPos = 0;
-      m_repeat = false;
+    m_nextSendPos = 0;
+    m_repeat = false;
+    {
       Message* message;
       istringstream input;  // TODO create input from database of internal variables
       message = m_messages->find(m_command);
@@ -803,33 +870,45 @@ result_t BusHandler::handleSymbol() {
         input.str(SCAN_ANSWER);
       }
       // build response and store in m_response for sending back to requesting master
-      m_response.clear(true);  // escape while sending response
+      m_response.clear();
       result = message->prepareSlave(input, m_response);
       if (result != RESULT_OK) {
         return setState(bs_skip, result);
       }
-      return setState(bs_sendRes, RESULT_OK);
     }
-    return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    return setState(bs_sendRes, RESULT_OK);
 
   case bs_sendRes:
-    if (sending && m_answer && recvSymbol == sendSymbol) {
-      // successfully sent
-      m_nextSendPos++;
-      if (m_nextSendPos >= m_response.size()) {
-        // slave data completely sent
-        return setState(bs_recvResAck, RESULT_OK);
-      }
-      return RESULT_OK;
+    if (!sending || !m_answer) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
     }
-    return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    m_nextSendPos++;
+    if (m_nextSendPos >= m_response.size()) {
+      // slave data completely sent
+      return setState(bs_sendResCrc, RESULT_OK);
+    }
+    return RESULT_OK;
+
+  case bs_sendResCrc:
+    if (!sending || m_currentRequest == NULL) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    }
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    return setState(bs_recvResAck, RESULT_OK);
 
   case bs_sendSyn:
-    if (sending && recvSymbol == sendSymbol) {
-      // successfully sent
-      return setState(bs_skip, RESULT_OK);
+    if (!sending) {
+      return setState(bs_skip, RESULT_ERR_INVALID_ARG);
     }
-    return setState(bs_skip, RESULT_ERR_INVALID_ARG);
+    if (recvSymbol != sendSymbol) {
+      return setState(bs_skip, RESULT_ERR_SYMBOL);
+    }
+    return setState(bs_skip, RESULT_OK);
   }
   return RESULT_OK;
 }
@@ -863,7 +942,7 @@ result_t BusHandler::setState(BusState state, result_t result, bool firstRepetit
   }
 
   if (state == bs_noSignal) {  // notify all requests
-    m_response.clear(false);  // notify with empty response
+    m_response.clear();  // notify with empty response
     while ((m_currentRequest = m_nextRequests.pop()) != NULL) {
       bool restart = m_currentRequest->notify(RESULT_ERR_NO_SIGNAL, m_response);
       if (restart) {  // should not occur with no signal
@@ -877,6 +956,7 @@ result_t BusHandler::setState(BusState state, result_t result, bool firstRepetit
     }
   }
 
+  m_escape = 0;
   if (state == m_state) {
     return result;
   }
@@ -895,12 +975,13 @@ result_t BusHandler::setState(BusState state, result_t result, bool firstRepetit
 
   if (state == bs_ready || state == bs_skip) {
     m_command.clear();
-    m_commandCrcValid = false;
-    m_response.clear(false);  // unescape while receiving response
-    m_responseCrcValid = false;
+    m_crc = 0;
+    m_crcValid = false;
+    m_response.clear();
     m_nextSendPos = 0;
+  } else if (state == bs_recvRes || state == bs_sendRes) {
+    m_crc = 0;
   }
-
   return result;
 }
 
@@ -1182,7 +1263,7 @@ result_t BusHandler::scanAndWait(unsigned char dstAddress, SymbolString& slave)
     return RESULT_ERR_NOTFOUND;
   }
   istringstream input;
-  SymbolString master;
+  SymbolString master(true);
   result_t result = scanMessage->prepareMaster(m_ownMasterAddress, master, input, UI_FIELD_SEPARATOR, dstAddress);
   if (result == RESULT_OK) {
     result = sendAndWait(master, slave);
diff --git a/src/ebusd/bushandler.h b/src/ebusd/bushandler.h
index 95944c45..58d91c01 100644
--- a/src/ebusd/bushandler.h
+++ b/src/ebusd/bushandler.h
@@ -66,13 +66,17 @@ enum BusState {
   bs_skip,        //!< skip all symbols until next @a SYN
   bs_ready,       //!< ready for next master (after @a SYN symbol, send/receive QQ)
   bs_recvCmd,     //!< receive command (ZZ, PBSB, master data) [passive set]
+  bs_recvCmdCrc,  //!< receive command CRC [passive set]
   bs_recvCmdAck,  //!< receive command ACK/NACK [passive set + active set+get]
   bs_recvRes,     //!< receive response (slave data) [passive set + active get]
+  bs_recvResCrc,  //!< receive response CRC [passive set + active get]
   bs_recvResAck,  //!< receive response ACK/NACK [passive set]
   bs_sendCmd,     //!< send command (ZZ, PBSB, master data) [active set+get]
+  bs_sendCmdCrc,  //!< send command CRC [active set+get]
   bs_sendResAck,  //!< send response ACK/NACK [active get]
   bs_sendCmdAck,  //!< send command ACK/NACK [passive get]
   bs_sendRes,     //!< send response (slave data) [passive get]
+  bs_sendResCrc,  //!< send response CRC [passive get]
   bs_sendSyn,     //!< send SYN for completed transfer [active set+get]
 };
 
@@ -102,7 +106,7 @@ class BusRequest {
  public:
   /**
    * Constructor.
-   * @param master the escaped master data @a SymbolString to send.
+   * @param master the master data @a SymbolString to send.
    * @param deleteOnFinish whether to automatically delete this @a BusRequest when finished.
    */
   BusRequest(SymbolString& master, const bool deleteOnFinish)
@@ -124,7 +128,7 @@ class BusRequest {
 
 
  protected:
-  /** the escaped master data @a SymbolString to send. */
+  /** the master data @a SymbolString to send. */
   SymbolString& m_master;
 
   /** the number of times a send is repeated due to lost arbitration. */
@@ -166,8 +170,8 @@ class PollRequest : public BusRequest {
 
 
  private:
-  /** the escaped master data @a SymbolString. */
-  SymbolString m_master;
+  /** the master data @a SymbolString. */
+  SymbolString m_master{true};
 
   /** the associated @a Message. */
   Message* m_message;
@@ -218,8 +222,8 @@ class ScanRequest : public BusRequest {
   /** the @a MessageMap instance. */
   MessageMap* m_messageMap;
 
-  /** the escaped master data @a SymbolString. */
-  SymbolString m_master;
+  /** the master data @a SymbolString. */
+  SymbolString m_master{true};
 
   /** the currently queried @a Message. */
   Message* m_message;
@@ -253,7 +257,7 @@ class ActiveBusRequest : public BusRequest {
  public:
   /**
    * Constructor.
-   * @param master the escaped master data @a SymbolString to send.
+   * @param master the master data @a SymbolString to send.
    * @param slave reference to @a SymbolString for filling in the received slave data.
    */
   ActiveBusRequest(SymbolString& master, SymbolString& slave)
@@ -292,8 +296,8 @@ class GrabbedMessage {
    * @param other the @a GrabbedMessage to copy from.
    */
   GrabbedMessage(const GrabbedMessage& other) : m_count(other.m_count) {
-    m_lastMaster.addAll(other.m_lastMaster);
-    m_lastSlave.addAll(other.m_lastSlave);
+    m_lastMaster = other.m_lastMaster;
+    m_lastSlave = other.m_lastSlave;
   }
 
   /**
@@ -364,8 +368,7 @@ class BusHandler : public WaitThread {
       m_pollInterval(pollInterval), m_lastReceive(0), m_lastPoll(0),
       m_currentRequest(NULL), m_runningScans(0), m_nextSendPos(0),
       m_symPerSec(0), m_maxSymPerSec(0),
-      m_state(bs_noSignal), m_repeat(false),
-      m_command(false), m_commandCrcValid(false), m_response(false), m_responseCrcValid(false),
+      m_state(bs_noSignal), m_escape(0), m_crc(0), m_crcValid(false), m_repeat(false),
       m_grabMessages(true) {
     memset(m_seenAddresses, 0, sizeof(m_seenAddresses));
   }
@@ -398,7 +401,7 @@ class BusHandler : public WaitThread {
 
   /**
    * Send a message on the bus and wait for the answer.
-   * @param master the escaped @a SymbolString with the master data to send.
+   * @param master the @a SymbolString with the master data to send.
    * @param slave the @a SymbolString that will be filled with retrieved slave data.
    * @return the result code.
    */
@@ -632,21 +635,24 @@ class BusHandler : public WaitThread {
   /** the current @a BusState. */
   BusState m_state;
 
+  /** 0 when not escaping/unescaping, or @a ESC when receiving, or the original value when sending. */
+  unsigned char m_escape;
+
+  /** the calculated CRC. */
+  unsigned char m_crc;
+
+  /** whether the CRC matched. */
+  bool m_crcValid;
+
   /** whether the current message part is being repeated. */
   bool m_repeat;
 
-  /** the unescaped received command. */
-  SymbolString m_command;
+  /** the received command. */
+  SymbolString m_command{true};
 
-  /** whether the command CRC is valid. */
-  bool m_commandCrcValid;
-
-  /** the unescaped received response or escaped response to send. */
+  /** the received response or response to send. */
   SymbolString m_response;
 
-  /** whether the response CRC is valid. */
-  bool m_responseCrcValid;
-
   /** the participating bus addresses seen so far (0 if not seen yet, or combination of @a SEEN bits). */
   unsigned char m_seenAddresses[256];
 
diff --git a/src/ebusd/mainloop.cpp b/src/ebusd/mainloop.cpp
index adead1ca..a4a02c51 100644
--- a/src/ebusd/mainloop.cpp
+++ b/src/ebusd/mainloop.cpp
@@ -233,7 +233,7 @@ void MainLoop::run() {
             result = m_busHandler->startScan(true, "*");
           } else {
             logNotice(lf_main, "starting initial scan for %2.2x", m_initialScan);
-            SymbolString slave(false);
+            SymbolString slave;
             result = m_busHandler->scanAndWait(m_initialScan, slave);
             Message* message = m_messages->getScanMessage(m_initialScan);
             if (result == RESULT_OK && message != NULL) {
@@ -257,7 +257,7 @@ void MainLoop::run() {
           taskDelay = 5;
           lastScanAddress = 0;
         } else {
-          SymbolString slave(false);
+          SymbolString slave;
           if (scanned) {
             Message* message = m_messages->getScanMessage(lastScanAddress);
             slave = message->getLastSlaveData();
@@ -486,13 +486,14 @@ result_t MainLoop::parseHexMaster(vector<string> &args, size_t argPos, SymbolStr
   }
   result_t ret;
   unsigned int length = parseInt(msg.str().substr(3*2, 2).c_str(), 16, 0, MAX_POS, ret);
-  if (ret == RESULT_OK && (4+length)*2 != msg.str().size()) {
+  if (ret != RESULT_OK) {
+    return ret;
+  }
+  if ((4+length)*2 != msg.str().size()) {
     return RESULT_ERR_INVALID_ARG;
   }
-  ret = master.push_back(srcAddress == SYN ? m_address : srcAddress, false);
-  if (ret == RESULT_OK) {
-    ret = master.parseHex(msg.str());
-  }
+  master.push_back(srcAddress == SYN ? m_address : srcAddress);
+  ret = master.parseHex(msg.str());
   if (ret == RESULT_OK && !isValidAddress(master[1])) {
     ret = RESULT_ERR_INVALID_ADDR;
   }
@@ -613,18 +614,18 @@ string MainLoop::executeRead(vector<string> &args, const string levels) {
   time(&now);
 
   if (hex && argPos > 0) {
-    SymbolString cacheMaster(false);
-    result_t ret = parseHexMaster(args, argPos, cacheMaster, srcAddress);
+    SymbolString master(true);
+    result_t ret = parseHexMaster(args, argPos, master, srcAddress);
     if (ret != RESULT_OK) {
       return getResultCode(ret);
     }
-    if (cacheMaster[1] == BROADCAST || isMaster(cacheMaster[1])) {
+    if (master[1] == BROADCAST || isMaster(master[1])) {
       return getResultCode(RESULT_ERR_INVALID_ARG);
     }
-    logNotice(lf_main, "read hex cmd: %s", cacheMaster.getDataStr(true, false).c_str());
+    logNotice(lf_main, "read hex cmd: %s", master.getDataStr().c_str());
 
     // find message
-    Message* message = m_messages->find(cacheMaster, false, true, false, false);
+    Message* message = m_messages->find(master, false, true, false, false);
 
     if (message == NULL) {
       return getResultCode(RESULT_ERR_NOTFOUND);
@@ -643,17 +644,15 @@ string MainLoop::executeRead(vector<string> &args, const string levels) {
             || (message->isPassive() && message->getLastUpdateTime() != 0))) {
       SymbolString& slave = message->getLastSlaveData();
       logNotice(lf_main, "hex read %s %s from cache", message->getCircuit().c_str(), message->getName().c_str());
-      return slave.getDataStr(true, false);
+      return slave.getDataStr();
     }
 
     // send message
-    SymbolString master(true);
-    master.addAll(cacheMaster);
-    SymbolString slave(false);
+    SymbolString slave;
     ret = m_busHandler->sendAndWait(master, slave);
 
     if (ret == RESULT_OK) {
-      ret = message->storeLastData(cacheMaster, slave);
+      ret = message->storeLastData(master, slave);
       ostringstream result;
       if (ret == RESULT_OK) {
         ret = message->decodeLastData(result);
@@ -665,7 +664,7 @@ string MainLoop::executeRead(vector<string> &args, const string levels) {
         logError(lf_main, "read hex %s %s cache update: %s", message->getCircuit().c_str(), message->getName().c_str(),
             getResultCode(ret));
       }
-      return slave.getDataStr(true, false);
+      return slave.getDataStr();
     }
     logError(lf_main, "read hex %s %s: %s", message->getCircuit().c_str(), message->getName().c_str(),
         getResultCode(ret));
@@ -822,15 +821,15 @@ string MainLoop::executeWrite(vector<string> &args, const string levels) {
   }
 
   if (hex && argPos > 0) {
-    SymbolString cacheMaster(false);
-    result_t ret = parseHexMaster(args, argPos, cacheMaster, srcAddress);
+    SymbolString master(true);
+    result_t ret = parseHexMaster(args, argPos, master, srcAddress);
     if (ret != RESULT_OK) {
       return getResultCode(ret);
     }
-    logNotice(lf_main, "write hex cmd: %s", cacheMaster.getDataStr(true, false).c_str());
+    logNotice(lf_main, "write hex cmd: %s", master.getDataStr().c_str());
 
     // find message
-    Message* message = m_messages->find(cacheMaster, false, false, true, false);
+    Message* message = m_messages->find(master, false, false, true, false);
 
     if (message == NULL) {
       return getResultCode(RESULT_ERR_NOTFOUND);
@@ -845,14 +844,12 @@ string MainLoop::executeWrite(vector<string> &args, const string levels) {
       return getResultCode(RESULT_ERR_INVALID_ARG);  // non-matching circuit
     }
     // send message
-    SymbolString master(true);
-    master.addAll(cacheMaster);
-    SymbolString slave(false);
+    SymbolString slave;
     ret = m_busHandler->sendAndWait(master, slave);
 
     if (ret == RESULT_OK) {
       // also update read messages
-      ret = message->storeLastData(cacheMaster, slave);
+      ret = message->storeLastData(master, slave);
       ostringstream result;
       if (ret == RESULT_OK) {
         ret = message->decodeLastData(result);
@@ -870,7 +867,7 @@ string MainLoop::executeWrite(vector<string> &args, const string levels) {
       if (isMaster(master[1])) {
         return getResultCode(RESULT_OK);
       }
-      return slave.getDataStr(true, false);
+      return slave.getDataStr();
     }
     logError(lf_main, "write hex %s %s: %s", message->getCircuit().c_str(), message->getName().c_str(),
         getResultCode(ret));
@@ -959,17 +956,15 @@ string MainLoop::executeHex(vector<string> &args) {
   }
 
   if (argPos > 0) {
-    SymbolString cacheMaster(false);
-    result_t ret = parseHexMaster(args, argPos, cacheMaster, srcAddress);
+    SymbolString master(true);
+    result_t ret = parseHexMaster(args, argPos, master, srcAddress);
     if (ret != RESULT_OK) {
       return getResultCode(ret);
     }
-    logNotice(lf_main, "hex cmd: %s", cacheMaster.getDataStr(true, false).c_str());
+    logNotice(lf_main, "hex cmd: %s", master.getDataStr().c_str());
 
     // send message
-    SymbolString master(true);
-    master.addAll(cacheMaster);
-    SymbolString slave(false);
+    SymbolString slave;
     ret = m_busHandler->sendAndWait(master, slave);
 
     if (ret == RESULT_OK) {
@@ -979,7 +974,7 @@ string MainLoop::executeHex(vector<string> &args) {
       if (isMaster(master[1])) {
         return getResultCode(RESULT_OK);
       }
-      return slave.getDataStr(true, false);
+      return slave.getDataStr();
     }
     logError(lf_main, "hex: %s", getResultCode(ret));
     return getResultCode(ret);
@@ -1171,13 +1166,13 @@ string MainLoop::executeFind(vector<string> &args, string levels) {
         result << "no data stored";
       } else if (hexFormat) {
         result << message->getLastMasterData().getDataStr()
-             << " / " << message->getLastSlaveData().getDataStr(true, false);
+             << " / " << message->getLastSlaveData().getDataStr();
       } else {
         result_t ret = message->decodeLastData(result, verbosity);
         if (ret != RESULT_OK) {
           result << " (" << getResultCode(ret)
                << " for " << message->getLastMasterData().getDataStr()
-               << " / " << message->getLastSlaveData().getDataStr(true, false) << ")";
+               << " / " << message->getLastSlaveData().getDataStr() << ")";
         }
       }
       if (verbosity == (OF_NAMES|OF_UNITS|OF_COMMENTS)) {
@@ -1310,7 +1305,7 @@ string MainLoop::executeScan(vector<string> &args, string levels) {
     if (result != RESULT_OK) {
       return getResultCode(result);
     }
-    SymbolString slave(false);
+    SymbolString slave;
     result = m_busHandler->scanAndWait(dstAddress, slave);
     if (result != RESULT_OK) {
       return getResultCode(result);
diff --git a/src/ebusd/states.png b/src/ebusd/states.png
index 1a9cc6e7..e6f172a0 100644
Binary files a/src/ebusd/states.png and b/src/ebusd/states.png differ
diff --git a/src/lib/ebus/contrib/test/test_tem.cpp b/src/lib/ebus/contrib/test/test_tem.cpp
index 27217311..94031b88 100644
--- a/src/lib/ebus/contrib/test/test_tem.cpp
+++ b/src/lib/ebus/contrib/test/test_tem.cpp
@@ -77,14 +77,14 @@ int main() {
     string check[5] = checks[i];
     istringstream isstr(check[0]);
     string expectStr = check[1];
-    SymbolString mstr(false);
+    SymbolString mstr(true);
     result_t result = mstr.parseHex(check[2]);
     if (result != RESULT_OK) {
       cout << "\"" << check[0] << "\": parse \"" << check[2] << "\" error: " << getResultCode(result) << endl;
       error = true;
       continue;
     }
-    SymbolString sstr(false);
+    SymbolString sstr;
     result = sstr.parseHex(check[3]);
     if (result != RESULT_OK) {
       cout << "\"" << check[0] << "\": parse \"" << check[3] << "\" error: " << getResultCode(result) << endl;
@@ -130,17 +130,17 @@ int main() {
     cout << "\": create OK" << endl;
 
     ostringstream output;
-    SymbolString writeMstr(false);
-    result = writeMstr.parseHex(mstr.getDataStr(true, false).substr(0, 10));
+    SymbolString writeMstr(true);
+    result = writeMstr.parseHex(mstr.getDataStr().substr(0, 10));
     if (result != RESULT_OK) {
-      cout << "  parse \"" << mstr.getDataStr(true, false).substr(0, 10) << "\" error: " << getResultCode(result)
+      cout << "  parse \"" << mstr.getDataStr().substr(0, 10) << "\" error: " << getResultCode(result)
           << endl;
       error = true;
     }
-    SymbolString writeSstr(false);
-    result = writeSstr.parseHex(sstr.getDataStr(true, false).substr(0, 2));
+    SymbolString writeSstr;
+    result = writeSstr.parseHex(sstr.getDataStr().substr(0, 2));
     if (result != RESULT_OK) {
-      cout << "  parse \"" << sstr.getDataStr(true, false).substr(0, 2) << "\" error: " << getResultCode(result)
+      cout << "  parse \"" << sstr.getDataStr().substr(0, 2) << "\" error: " << getResultCode(result)
           << endl;
       error = true;
     }
@@ -186,8 +186,8 @@ int main() {
       error = true;
     } else {
       bool match = mstr == writeMstr && sstr == writeSstr;
-      verify(failedWriteMatch, "write", expectStr, match, mstr.getDataStr(true, false) + " "
-          + sstr.getDataStr(true, false), writeMstr.getDataStr(true, false) + " " + writeSstr.getDataStr(true, false));
+      verify(failedWriteMatch, "write", expectStr, match, mstr.getDataStr() + " "
+          + sstr.getDataStr(), writeMstr.getDataStr() + " " + writeSstr.getDataStr());
     }
     delete fields;
     fields = NULL;
diff --git a/src/lib/ebus/data.h b/src/lib/ebus/data.h
index ac94dbc6..d18ce16f 100644
--- a/src/lib/ebus/data.h
+++ b/src/lib/ebus/data.h
@@ -163,7 +163,7 @@ class DataField {
   /**
    * Reads the numeric value from the @a SymbolString.
    * @param partType the @a PartType of the data.
-   * @param data the unescaped data @a SymbolString for reading binary data.
+   * @param data the data @a SymbolString for reading binary data.
    * @param offset the additional offset to add for reading binary data.
    * @param output the variable in which to store the numeric value.
    * @param fieldName the name of the field to read, or NULL for the first field.
@@ -180,7 +180,7 @@ class DataField {
   /**
    * Reads the value from the @a SymbolString.
    * @param partType the @a PartType of the data.
-   * @param data the unescaped data @a SymbolString for reading binary data.
+   * @param data the data @a SymbolString for reading binary data.
    * @param offset the additional offset to add for reading binary data.
    * @param output the @a ostringstream to append the formatted value to.
    * @param outputFormat the @a OutputFormat options to use.
@@ -332,7 +332,7 @@ class SingleDataField : public DataField {
  protected:
   /**
    * Internal method for reading the field from a @a SymbolString.
-   * @param input the unescaped @a SymbolString to read the binary value from.
+   * @param input the @a SymbolString to read the binary value from.
    * @param isMaster whether the @a SymbolString is the master part.
    * @param offset the offset in the @a SymbolString.
    * @param output the ostringstream to append the formatted value to.
@@ -347,7 +347,7 @@ class SingleDataField : public DataField {
    * Internal method for writing the field to a @a SymbolString.
    * @param input the @a istringstream to parse the formatted value from.
    * @param offset the offset in the @a SymbolString.
-   * @param output the unescaped @a SymbolString to write the binary value to.
+   * @param output the @a SymbolString to write the binary value to.
    * @param isMaster whether the @a SymbolString is the master part.
    * @param usedLength the variable in which to store the used length in bytes, or NULL.
    * @return @a RESULT_OK on success, or an error code.
diff --git a/src/lib/ebus/datatype.cpp b/src/lib/ebus/datatype.cpp
index 91161ef5..73038e72 100644
--- a/src/lib/ebus/datatype.cpp
+++ b/src/lib/ebus/datatype.cpp
@@ -40,50 +40,6 @@ using std::setfill;
 using std::setprecision;
 using std::setw;
 
-unsigned int parseInt(const char* str, int base, const unsigned int minValue, const unsigned int maxValue,
-    result_t& result, unsigned int* length) {
-  char* strEnd = NULL;
-
-  unsigned long ret = strtoul(str, &strEnd, base);
-
-  if (strEnd == NULL || strEnd == str || *strEnd != 0) {
-    result = RESULT_ERR_INVALID_NUM;  // invalid value
-    return 0;
-  }
-
-  if (minValue > ret || ret > maxValue) {
-    result = RESULT_ERR_OUT_OF_RANGE;  // invalid value
-    return 0;
-  }
-  if (length != NULL) {
-    *length = (unsigned int)(strEnd - str);
-  }
-  result = RESULT_OK;
-  return (unsigned int)ret;
-}
-
-int parseSignedInt(const char* str, int base, const int minValue, const int maxValue, result_t& result,
-    unsigned int* length) {
-  char* strEnd = NULL;
-
-  long ret = strtol(str, &strEnd, base);
-
-  if (strEnd == NULL || *strEnd != 0) {
-    result = RESULT_ERR_INVALID_NUM;  // invalid value
-    return 0;
-  }
-
-  if (minValue > ret || ret > maxValue) {
-    result = RESULT_ERR_OUT_OF_RANGE;  // invalid value
-    return 0;
-  }
-  if (length != NULL) {
-    *length = (unsigned int)(strEnd - str);
-  }
-  result = RESULT_OK;
-  return static_cast<int>(ret);
-}
-
 void printErrorPos(ostream& out, vector<string>::iterator begin, const vector<string>::iterator end,
     vector<string>::iterator pos, string filename, size_t lineNo, result_t result) {
   if (pos > begin) {
diff --git a/src/lib/ebus/datatype.h b/src/lib/ebus/datatype.h
index 658d51c6..59e9e639 100644
--- a/src/lib/ebus/datatype.h
+++ b/src/lib/ebus/datatype.h
@@ -123,7 +123,8 @@ enum PartType {
 /** bit flag for @a DataType: value may not be NULL. */
 #define REQ 0x40
 
-/** bit flag for @a DataType: binary representation is hex converted to decimal and interpreted as 2 digits (also requires #BCD). */
+/** bit flag for @a DataType: binary representation is hex converted to decimal and interpreted as 2 digits
+ * (also requires #BCD). */
 #define HCD 0x80
 
 /** bit flag for @a DataType: exponential numeric representation. */
@@ -142,32 +143,6 @@ enum PartType {
 #define CON 0x1000
 
 
-/**
- * Parse an unsigned int value.
- * @param str the string to parse.
- * @param base the numerical base.
- * @param minValue the minimum resulting value.
- * @param maxValue the maximum resulting value.
- * @param result the variable in which to store an error code when parsing failed or the value is out of bounds.
- * @param length the optional variable in which to store the number of read characters.
- * @return the parsed value.
- */
-unsigned int parseInt(const char* str, int base, const unsigned int minValue, const unsigned int maxValue,
-    result_t& result, unsigned int* length = NULL);
-
-/**
- * Parse a signed int value.
- * @param str the string to parse.
- * @param base the numerical base.
- * @param minValue the minimum resulting value.
- * @param maxValue the maximum resulting value.
- * @param result the variable in which to store an error code when parsing failed or the value is out of bounds.
- * @param length the optional variable in which to store the number of read characters.
- * @return the parsed value.
- */
-int parseSignedInt(const char* str, int base, const int minValue, const int maxValue, result_t& result,
-    unsigned int* length = NULL);
-
 /**
  * Print the error position of the iterator.
  * @param out the @a ostream to print to.
@@ -253,7 +228,7 @@ class DataType {
 
   /**
    * Internal method for reading the numeric raw value from a @a SymbolString.
-   * @param input the unescaped @a SymbolString to read the binary value from.
+   * @param input the @a SymbolString to read the binary value from.
    * @param offset the offset in the @a SymbolString.
    * @param length the number of symbols to read.
    * @param value the variable in which to store the numeric raw value.
@@ -265,7 +240,7 @@ class DataType {
 
   /**
    * Internal method for reading the field from a @a SymbolString.
-   * @param input the unescaped @a SymbolString to read the binary value from.
+   * @param input the @a SymbolString to read the binary value from.
    * @param isMaster whether the @a SymbolString is the master part.
    * @param offset the offset in the @a SymbolString.
    * @param length the number of symbols to read.
@@ -282,7 +257,7 @@ class DataType {
    * @param input the @a istringstream to parse the formatted value from.
    * @param offset the offset in the @a SymbolString.
    * @param length the number of symbols to write, or @a REMAIN_LEN.
-   * @param output the unescaped @a SymbolString to write the binary value to.
+   * @param output the @a SymbolString to write the binary value to.
    * @param isMaster whether the @a SymbolString is the master part.
    * @param usedLength the variable in which to store the used length in bytes, or NULL.
    * @return @a RESULT_OK on success, or an error code.
@@ -369,7 +344,8 @@ class DateTimeDataType : public DataType {
    */
   DateTimeDataType(const string id, const unsigned char bitCount, const uint16_t flags, const unsigned int replacement,
       const bool hasDate, const bool hasTime, const int16_t resolution)
-    : DataType(id, bitCount, flags, replacement), m_hasDate(hasDate), m_hasTime(hasTime), m_resolution(resolution == 0 ? 1 : resolution) {}
+    : DataType(id, bitCount, flags, replacement), m_hasDate(hasDate), m_hasTime(hasTime),
+      m_resolution(resolution == 0 ? 1 : resolution) {}
 
   /**
    * Destructor.
@@ -521,7 +497,7 @@ class NumberDataType : public DataType {
    * @param value the numeric raw value to write.
    * @param offset the offset in the @a SymbolString.
    * @param length the number of symbols to write, or @a REMAIN_LEN.
-   * @param output the unescaped @a SymbolString to write the binary value to.
+   * @param output the @a SymbolString to write the binary value to.
    * @param usedLength the variable in which to store the used length in bytes,
    * or NULL.
    * @return @a RESULT_OK on success, or an error code.
diff --git a/src/lib/ebus/message.cpp b/src/lib/ebus/message.cpp
index 00c2155b..12103252 100644
--- a/src/lib/ebus/message.cpp
+++ b/src/lib/ebus/message.cpp
@@ -590,43 +590,29 @@ bool Message::hasField(const char* fieldName, bool numeric) {
   return m_data->hasField(fieldName, numeric);
 }
 
-result_t Message::prepareMaster(const unsigned char srcAddress, SymbolString& masterData,
+result_t Message::prepareMaster(const unsigned char srcAddress, SymbolString& master,
     istringstream& input, char separator,
     const unsigned char dstAddress, unsigned char index) {
   if (m_isPassive) {
     return RESULT_ERR_INVALID_ARG;  // prepare not possible
   }
-  SymbolString master(false);
-  result_t result = master.push_back(srcAddress, false, false);
-  if (result != RESULT_OK) {
-    return result;
-  }
+  master.clear();
+  master.push_back(srcAddress);
   if (dstAddress == SYN) {
     if (m_dstAddress == SYN) {
       return RESULT_ERR_INVALID_ADDR;
     }
-    result = master.push_back(m_dstAddress, false, false);
+    master.push_back(m_dstAddress);
   } else {
-    result = master.push_back(dstAddress, false, false);
+    master.push_back(dstAddress);
   }
+  master.push_back(m_id[0]);
+  master.push_back(m_id[1]);
+  result_t result = prepareMasterPart(master, input, separator, index);
   if (result != RESULT_OK) {
     return result;
   }
-  result = master.push_back(m_id[0], false, false);
-  if (result != RESULT_OK) {
-    return result;
-  }
-  result = master.push_back(m_id[1], false, false);
-  if (result != RESULT_OK) {
-    return result;
-  }
-  result = prepareMasterPart(master, input, separator, index);
-  if (result != RESULT_OK) {
-    return result;
-  }
-  masterData.clear();
-  masterData.addAll(master);
-  result = storeLastData(pt_masterData, masterData, index);
+  result = storeLastData(pt_masterData, master, index);
   if (result < RESULT_OK) {
     return result;
   }
@@ -638,17 +624,11 @@ result_t Message::prepareMasterPart(SymbolString& master, istringstream& input,
     return RESULT_ERR_NOTFOUND;
   }
   unsigned char pos = master.size();
-  result_t result = master.push_back(0, false, false);  // length, will be set later
-  if (result != RESULT_OK) {
-    return result;
-  }
+  master.push_back(0);  // length, will be set later
   for (size_t i = 2; i < m_id.size(); i++) {
-    result = master.push_back(m_id[i], false, false);
-    if (result != RESULT_OK) {
-      return result;
-    }
+    master.push_back(m_id[i]);
   }
-  result = m_data->write(input, pt_masterData, master, getIdLength(), separator);
+  result_t result = m_data->write(input, pt_masterData, master, getIdLength(), separator);
   if (result != RESULT_OK) {
     return result;
   }
@@ -656,16 +636,13 @@ result_t Message::prepareMasterPart(SymbolString& master, istringstream& input,
   return result;
 }
 
-result_t Message::prepareSlave(istringstream& input, SymbolString& slaveData) {
+result_t Message::prepareSlave(istringstream& input, SymbolString& slave) {
   if (m_isWrite) {
     return RESULT_ERR_INVALID_ARG;  // prepare not possible
   }
-  SymbolString slave(false);
-  result_t result = slave.push_back(0, false, false);  // length, will be set later
-  if (result != RESULT_OK) {
-    return result;
-  }
-  result = m_data->write(input, pt_slaveData, slave, 0);
+  slave.clear();
+  slave.push_back(0);  // length, will be set later
+  result_t result = m_data->write(input, pt_slaveData, slave, 0);
   if (result != RESULT_OK) {
     return result;
   }
@@ -675,8 +652,6 @@ result_t Message::prepareSlave(istringstream& input, SymbolString& slaveData) {
     m_lastChangeTime = m_lastUpdateTime;
     m_lastSlaveData = slave;
   }
-  slaveData.clear();
-  slaveData.addAll(slave);
   return result;
 }
 
@@ -695,7 +670,7 @@ result_t Message::storeLastData(const PartType partType, SymbolString& data, uns
     time(&m_lastUpdateTime);
   }
   if (partType == pt_masterData) {
-    switch (data.compareMaster(m_lastMasterData)) {
+    switch (data.compareTo(m_lastMasterData)) {
     case 1:  // completely different
       m_lastChangeTime = m_lastUpdateTime;
       m_lastMasterData = data;
@@ -903,7 +878,7 @@ ChainedMessage::ChainedMessage(const string circuit, const string level, const s
   m_lastMasterUpdateTimes = reinterpret_cast<time_t*>(calloc(cnt, sizeof(time_t)));
   m_lastSlaveUpdateTimes = reinterpret_cast<time_t*>(calloc(cnt, sizeof(time_t)));
   for (size_t index = 0; index < cnt; index++) {
-    m_lastMasterDatas[index] = new SymbolString();
+    m_lastMasterDatas[index] = new SymbolString(true);
     m_lastSlaveDatas[index] = new SymbolString();
   }
 }
@@ -1000,7 +975,7 @@ result_t ChainedMessage::prepareMasterPart(SymbolString& master, istringstream&
   if (index >= cnt) {
     return RESULT_ERR_NOTFOUND;
   }
-  SymbolString allData(false);
+  SymbolString allData(true);
   result_t result = m_data->write(input, pt_masterData, allData, 0, separator);
   if (result != RESULT_OK) {
     return result;
@@ -1017,21 +992,12 @@ result_t ChainedMessage::prepareMasterPart(SymbolString& master, istringstream&
     return RESULT_ERR_INVALID_POS;
   }
   vector<unsigned char> id = m_ids[index];
-  result = master.push_back((unsigned char)(id.size()-2+addData), false, false);  // NN
-  if (result != RESULT_OK) {
-    return result;
-  }
+  master.push_back((unsigned char)(id.size()-2+addData));  // NN
   for (size_t i = 2; i < id.size(); i++) {
-    result = master.push_back(id[i], false, false);
-    if (result != RESULT_OK) {
-      return result;
-    }
+    master.push_back(id[i]);
   }
   for (size_t i = 0; i < addData; i++) {
-    result = master.push_back(allData[pos+i], false, false);
-    if (result != RESULT_OK) {
-      return result;
-    }
+    master.push_back(allData[pos+i]);
   }
   if (index == 0) {
     for (size_t i = 0; i < cnt; i++) {
@@ -1059,7 +1025,7 @@ result_t ChainedMessage::storeLastData(const PartType partType, SymbolString& da
     return RESULT_ERR_INVALID_ARG;
   }
   if (partType == pt_masterData) {
-    switch (data.compareMaster(*m_lastMasterDatas[index])) {
+    switch (data.compareTo(*m_lastMasterDatas[index])) {
     case 1:  // completely different
       *m_lastMasterDatas[index] = data;
       break;
@@ -1098,19 +1064,19 @@ result_t ChainedMessage::storeLastData(const PartType partType, SymbolString& da
     }
   }
   // everything was completely retrieved in short time
-  SymbolString master(false);
-  SymbolString slave(false);
+  SymbolString master(true);
+  SymbolString slave;
   size_t offset = 5+(m_ids[0].size()-2);  // skip QQ, ZZ, PB, SB, NN
   for (index = 0; index < m_ids.size(); index++) {
     SymbolString* add = m_lastMasterDatas[index];
     size_t end = 5+(*add)[4];
     for (size_t pos = index == 0 ? 0 : offset; pos < end; pos++) {
-      master.push_back((*add)[pos], false, false);
+      master.push_back((*add)[pos]);
     }
     add = m_lastSlaveDatas[index];
     end = 1+(*add)[0];
     for (size_t pos = index == 0 ? 0 : 1; pos < end; pos++) {
-      slave.push_back((*add)[pos], false, false);
+      slave.push_back((*add)[pos]);
     }
   }
   // adjust NN
diff --git a/src/lib/ebus/message.h b/src/lib/ebus/message.h
index 297fd5f3..e54817bf 100644
--- a/src/lib/ebus/message.h
+++ b/src/lib/ebus/message.h
@@ -421,14 +421,14 @@ class Message {
   /**
    * Prepare the master @a SymbolString for sending a query or command to the bus.
    * @param srcAddress the source address to set.
-   * @param masterData the master data @a SymbolString for writing symbols to.
+   * @param master the master data @a SymbolString for writing symbols to.
    * @param input the @a istringstream to parse the formatted value(s) from.
    * @param separator the separator character between multiple fields.
    * @param dstAddress the destination address to set, or @a SYN to keep the address defined during construction.
    * @param index the index of the part to prepare.
    * @return @a RESULT_OK on success, or an error code.
    */
-  result_t prepareMaster(const unsigned char srcAddress, SymbolString& masterData,
+  result_t prepareMaster(const unsigned char srcAddress, SymbolString& master,
       istringstream& input, char separator = UI_FIELD_SEPARATOR,
       const unsigned char dstAddress = SYN, unsigned char index = 0);
 
@@ -449,10 +449,10 @@ class Message {
   /**
    * Prepare the slave @a SymbolString for sending an answer to the bus.
    * @param input the @a istringstream to parse the formatted value(s) from.
-   * @param slaveData the slave data @a SymbolString for writing symbols to.
+   * @param slave the slave data @a SymbolString for writing symbols to.
    * @return @a RESULT_OK on success, or an error code.
    */
-  virtual result_t prepareSlave(istringstream& input, SymbolString& slaveData);
+  virtual result_t prepareSlave(istringstream& input, SymbolString& slave);
 
   /**
    * Store the last seen master and slave data.
@@ -631,7 +631,7 @@ class Message {
   Condition* m_condition;
 
   /** the last seen master data. */
-  SymbolString m_lastMasterData;
+  SymbolString m_lastMasterData{true};
 
   /** the last seen slave data. */
   SymbolString m_lastSlaveData;
diff --git a/src/lib/ebus/result.cpp b/src/lib/ebus/result.cpp
index 5acd5676..1489e23b 100644
--- a/src/lib/ebus/result.cpp
+++ b/src/lib/ebus/result.cpp
@@ -49,6 +49,7 @@ const char* getResultCode(result_t resultCode) {
   case RESULT_ERR_NAK:          return "ERR: NAK received";
   case RESULT_ERR_NO_SIGNAL:    return "ERR: no signal";
   case RESULT_ERR_SYN:          return "ERR: SYN received";
+  case RESULT_ERR_SYMBOL:       return "ERR: wrong symbol received";
   case RESULT_ERR_NOTAUTHORIZED: return "ERR: not authorized";
 
   default:
diff --git a/src/lib/ebus/result.h b/src/lib/ebus/result.h
index c28041ed..a54ef3fc 100644
--- a/src/lib/ebus/result.h
+++ b/src/lib/ebus/result.h
@@ -33,7 +33,7 @@ namespace ebusd {
 enum result_t {
   RESULT_OK = 0,                    //!< success
 
-  RESULT_CONTINUE = 1,              //!< more input data is needed (e.g. start of escape sequence received)
+  RESULT_CONTINUE = 1,              //!< more input data is needed
   RESULT_EMPTY = 2,                 //!< empty result
 
   RESULT_ERR_GENERIC_IO = -1,       //!< generic I/O error (usually fatal)
@@ -62,8 +62,9 @@ enum result_t {
 
   RESULT_ERR_NO_SIGNAL = -22,       //!< no signal found on the bus
   RESULT_ERR_SYN = -23,             //!< SYN received instead of answer
+  RESULT_ERR_SYMBOL = -24,          //!< wrong symbol received instead of sent symbol
 
-  RESULT_ERR_NOTAUTHORIZED = -24    //!< not authorized for this action
+  RESULT_ERR_NOTAUTHORIZED = -25    //!< not authorized for this action
 };
 
 
diff --git a/src/lib/ebus/symbol.cpp b/src/lib/ebus/symbol.cpp
index 28bd23f9..935b9edd 100644
--- a/src/lib/ebus/symbol.cpp
+++ b/src/lib/ebus/symbol.cpp
@@ -54,64 +54,103 @@ static const unsigned char CRC_LOOKUP_TABLE[] = {
 };
 
 
-void SymbolString::addAll(const SymbolString& str, bool skipLastSymbol) {
-  bool addCrc = m_unescapeState == 0;
-  bool isEscaped = str.m_unescapeState == 0;
-  vector<unsigned char> data = str.m_data;
-  size_t end = data.size();
-  if (end > 0 && skipLastSymbol) {
-    end--;
+unsigned int parseInt(const char* str, int base, const unsigned int minValue, const unsigned int maxValue,
+    result_t& result, unsigned int* length) {
+  char* strEnd = NULL;
+
+  unsigned long ret = strtoul(str, &strEnd, base);
+
+  if (strEnd == NULL || strEnd == str || *strEnd != 0) {
+    result = RESULT_ERR_INVALID_NUM;  // invalid value
+    return 0;
   }
-  for (size_t i = 0; i < end; i++) {
-    push_back(data[i], isEscaped, addCrc);
+
+  if (minValue > ret || ret > maxValue) {
+    result = RESULT_ERR_OUT_OF_RANGE;  // invalid value
+    return 0;
   }
-  if (addCrc) {
-    push_back(m_crc, false, false);  // add CRC
+  if (length != NULL) {
+    *length = (unsigned int)(strEnd - str);
   }
+  result = RESULT_OK;
+  return (unsigned int)ret;
 }
 
-result_t SymbolString::parseHex(const string& str, const bool isEscaped) {
-  bool addCrc = m_unescapeState == 0;
-  for (size_t i = 0; i < str.size(); i += 2) {
-    char* strEnd = NULL;
-    const char* strBegin = str.substr(i, 2).c_str();
-    unsigned long value = strtoul(strBegin, &strEnd, 16);
+int parseSignedInt(const char* str, int base, const int minValue, const int maxValue, result_t& result,
+    unsigned int* length) {
+  char* strEnd = NULL;
 
-    if (strEnd == NULL || strEnd != strBegin+2 || value > 0xff) {
-      return RESULT_ERR_INVALID_NUM;  // invalid value
-    }
-    push_back((unsigned char)value, isEscaped, addCrc);
+  long ret = strtol(str, &strEnd, base);
+
+  if (strEnd == NULL || *strEnd != 0) {
+    result = RESULT_ERR_INVALID_NUM;  // invalid value
+    return 0;
   }
-  if (addCrc) {
-    push_back(m_crc, false, false);  // add CRC
+
+  if (minValue > ret || ret > maxValue) {
+    result = RESULT_ERR_OUT_OF_RANGE;  // invalid value
+    return 0;
+  }
+  if (length != NULL) {
+    *length = (unsigned int)(strEnd - str);
+  }
+  result = RESULT_OK;
+  return static_cast<int>(ret);
+}
+
+
+void SymbolString::updateCrc(unsigned char& crc, const unsigned char value) {
+  crc = CRC_LOOKUP_TABLE[crc]^value;
+}
+
+result_t SymbolString::parseHex(const string& str) {
+  result_t result;
+  for (size_t i = 0; i < str.size(); i += 2) {
+    unsigned char value = (unsigned char)parseInt(str.substr(i, 2).c_str(), 16, 0, 0xff, result);
+    if (result != RESULT_OK) {
+      return result;
+    }
+    m_data.push_back(value);
   }
   return RESULT_OK;
 }
 
-const string SymbolString::getDataStr(const bool unescape, const bool skipLastSymbol,
-    unsigned char skipFirstSymbols) {
-  bool previousEscape = false;
+result_t SymbolString::parseHexEscaped(const string& str) {
+  result_t result;
+  bool inEscape = false;
+  for (size_t i = 0; i < str.size(); i += 2) {
+    unsigned char value = (unsigned char)parseInt(str.substr(i, 2).c_str(), 16, 0, 0xff, result);
+    if (result != RESULT_OK) {
+      return result;
+    }
+    if (inEscape) {
+      if (value == 0x00) {
+        m_data.push_back(ESC);
+        inEscape = false;
+      } else if (value == 0x01) {
+        m_data.push_back(SYN);
+        inEscape = false;
+      } else {
+        return RESULT_ERR_ESC;  // invalid escape sequence
+      }
+    } else if (value == ESC) {
+      inEscape = true;
+    } else if (value == SYN) {
+      return RESULT_ERR_ESC;  // invalid escape sequence
+    } else {
+      m_data.push_back(value);
+    }
+  }
+  return inEscape ? RESULT_ERR_ESC : RESULT_OK;
+}
+
+const string SymbolString::getDataStr(unsigned char skipFirstSymbols) {
   ostringstream sstr;
   for (size_t i = 0; i < m_data.size(); i++) {
-    unsigned char value = m_data[i];
-    if (m_unescapeState == 0 && unescape && previousEscape) {
-      if (skipFirstSymbols > 0) {
-        skipFirstSymbols--;
-      } else if (!skipLastSymbol || i+1 < m_data.size()) {
-        if (value == 0x00) {
-          sstr << "a9";  // ESC
-        } else if (value == 0x01) {
-          sstr << "aa";  // SYN
-        } else {
-          sstr << "XX";  // invalid escape sequence
-        }
-      }
-      previousEscape = false;
-    } else if (m_unescapeState == 0 && unescape && value == ESC) {
-      previousEscape = true;  // escape sequence not yet finished
-    } else if (skipFirstSymbols > 0) {
+    if (skipFirstSymbols > 0) {
       skipFirstSymbols--;
-    } else if (!skipLastSymbol || i+1 < m_data.size()) {
+    } else {
+      unsigned char value = m_data[i];
       sstr << nouppercase << setw(2) << hex
           << setfill('0') << static_cast<unsigned>(value);
     }
@@ -119,83 +158,23 @@ const string SymbolString::getDataStr(const bool unescape, const bool skipLastSy
   return sstr.str();
 }
 
-result_t SymbolString::push_back(const unsigned char value, const bool isEscaped, const bool updateCRC) {
-  if (m_unescapeState == 0) {  // store escaped data
-    if (!isEscaped && value == ESC) {
-      m_data.push_back(ESC);
-      m_data.push_back(0x00);
-      if (updateCRC) {
-        addCRC(ESC);
-        addCRC(0x00);
-      }
-    } else if (!isEscaped && value == SYN) {
-      m_data.push_back(ESC);
-      m_data.push_back(0x01);
-      if (updateCRC) {
-        addCRC(ESC);
-        addCRC(0x01);
-      }
+unsigned char SymbolString::calcCrc() const {
+  unsigned char crc = 0;
+  for (size_t i = 0; i < m_data.size(); i++) {
+    unsigned char value = m_data[i];
+    if (value == ESC) {
+      updateCrc(crc, ESC);
+      updateCrc(crc, 0x00);
+    } else if (value == SYN) {
+      updateCrc(crc, ESC);
+      updateCrc(crc, 0x01);
     } else {
-      m_data.push_back(value);
-      if (updateCRC) {
-        addCRC(value);
-      }
+      updateCrc(crc, value);
     }
-    return RESULT_OK;
   }
-  if (!isEscaped) {
-    if (m_unescapeState != 1) {
-      return RESULT_ERR_ESC;  // invalid unescape state
-    }
-    m_data.push_back(value);
-    if (updateCRC) {
-      if (value == ESC) {
-        addCRC(ESC);
-        addCRC(0x00);
-      } else if (value == SYN) {
-        addCRC(ESC);
-        addCRC(0x01);
-      } else {
-        addCRC(value);
-      }
-    }
-    return RESULT_OK;
-  }
-  if (m_unescapeState != 1) {
-    if (updateCRC) {
-      addCRC(value);
-    }
-    if (value == 0x00) {
-      m_data.push_back(ESC);
-      m_unescapeState = 1;
-      return RESULT_OK;
-    }
-    if (value == 0x01) {
-      m_data.push_back(SYN);
-      m_unescapeState = 1;
-      return RESULT_OK;
-    }
-    return RESULT_ERR_ESC;  // invalid escape sequence
-  }
-  if (value == ESC) {
-    if (updateCRC) {
-      addCRC(value);
-    }
-    m_unescapeState = 2;
-    return RESULT_CONTINUE;
-  }
-  if (updateCRC) {
-    addCRC(value);
-  }
-  m_data.push_back(value);
-  return RESULT_OK;
+  return crc;
 }
 
-void SymbolString::addCRC(const unsigned char value) {
-  m_crc = CRC_LOOKUP_TABLE[m_crc]^value;
-}
-
-
 
 /**
  * Return the index of the upper or lower 4 bits of a master address.
diff --git a/src/lib/ebus/symbol.h b/src/lib/ebus/symbol.h
index ecb39162..88436cf7 100644
--- a/src/lib/ebus/symbol.h
+++ b/src/lib/ebus/symbol.h
@@ -32,9 +32,9 @@ namespace ebusd {
 /** @file lib/ebus/symbol.h
  * Classes, functions, and constants related to symbols on the eBUS.
  *
- * The @a SymbolString class is used for escaping or unescaping a sequence of
- * bytes in preparation for sending to the bus or after reception of bytes from
- * the bus, as well as calculating and verifying the CRC of a message part.
+ * The @a SymbolString class is used for holding a sequence of bytes received
+ * from or sent to the bus, as well as calculating and verifying the CRC of a
+ * message part.
  *
  * A message on the bus always consists of a command part, i.e. the data sent
  * from a master to the bus. The command part starts with the sending master
@@ -70,51 +70,83 @@ using std::vector;
 
 /** escape symbol, either followed by 0x00 for the value 0xA9, or 0x01 for the value 0xAA. */
 #define ESC 0xA9
+
 /** synchronization symbol. */
 #define SYN 0xAA
+
 /** positive acknowledge symbol. */
 #define ACK 0x00
+
 /** negative acknowledge symbol. */
 #define NAK 0xFF
+
 /** the broadcast destination address. */
 #define BROADCAST 0xFE
 
+/**
+ * Parse an unsigned int value.
+ * @param str the string to parse.
+ * @param base the numerical base.
+ * @param minValue the minimum resulting value.
+ * @param maxValue the maximum resulting value.
+ * @param result the variable in which to store an error code when parsing failed or the value is out of bounds.
+ * @param length the optional variable in which to store the number of read characters.
+ * @return the parsed value.
+ */
+unsigned int parseInt(const char* str, int base, const unsigned int minValue, const unsigned int maxValue,
+    result_t& result, unsigned int* length = NULL);
 
 /**
- * A string of escaped or unescaped bus symbols.
+ * Parse a signed int value.
+ * @param str the string to parse.
+ * @param base the numerical base.
+ * @param minValue the minimum resulting value.
+ * @param maxValue the maximum resulting value.
+ * @param result the variable in which to store an error code when parsing failed or the value is out of bounds.
+ * @param length the optional variable in which to store the number of read characters.
+ * @return the parsed value.
+ */
+int parseSignedInt(const char* str, int base, const int minValue, const int maxValue, result_t& result,
+    unsigned int* length = NULL);
+
+/**
+ * A string of unescaped bus symbols.
  */
 class SymbolString {
  public:
   /**
-   * Creates a new empty escaped or unescaped instance.
-   * @param escaped whether to create an escaped instance.
+   * Creates a new empty instance.
+   * @param isMaster whether this instance if for the master part.
    */
-  explicit SymbolString(const bool escaped = true) : m_unescapeState(escaped ? 0 : 1), m_crc(0) {}
+  explicit SymbolString(const bool isMaster = false) { m_isMaster = isMaster; }
 
   /**
-   * Add all symbols from the other @a SymbolString and the calculated CRC if escaped.
-   * @param str the @a SymbolString to copy from.
-   * @param skipLastSymbol whether to skip the last symbol (probably the CRC).
+   * Update the CRC by adding a value.
+   * @param crc the current CRC to update.
+   * @param value the escaped value to add to the current CRC.
    */
-  void addAll(const SymbolString& str, const bool skipLastSymbol = false);
+  static void updateCrc(unsigned char& crc, const unsigned char value);
 
   /**
-   * Parse the escaped or unescaped hex @a string, add all symbols, and add the calculated CRC if escaped.
+   * Parse the hex @a string and add all symbols.
    * @param str the hex @a string.
-   * @param isEscaped whether the hex string is escaped.
    * @return @a RESULT_OK on success, or an error code.
    */
-  result_t parseHex(const string& str, const bool isEscaped = false);
+  result_t parseHex(const string& str);
+
+  /**
+   * Parse the escaped hex @a string and add all symbols.
+   * @param str the hex @a string.
+   * @return @a RESULT_OK on success, or an error code.
+   */
+  result_t parseHexEscaped(const string& str);
 
   /**
    * Return the symbols as hex string.
-   * @param unescape whether to unescape an escaped instance.
-   * @param skipLastSymbol whether to skip the last symbol (probably the CRC).
    * @param skipFirstSymbols the number of first symbols to skip.
    * @return the symbols as hex string.
    */
-  const string getDataStr(const bool unescape = true, const bool skipLastSymbol = true,
-      unsigned char skipFirstSymbols = 0);
+  const string getDataStr(unsigned char skipFirstSymbols = 0);
 
   /**
    * Return a reference to the symbol at the specified index.
@@ -131,11 +163,10 @@ class SymbolString {
   /**
    * Return whether this instance is equal to the other instance.
    * @param other the other instance.
-   * @return true if this instance is equal to the other instance (i.e. both escaped or both unescaped and same
-   * symbols).
+   * @return true if this instance is equal to the other instance.
    */
   bool operator == (SymbolString& other) {
-    return m_unescapeState == other.m_unescapeState && m_data == other.m_data;
+    return m_isMaster == other.m_isMaster && m_data == other.m_data;
   }
 
   /**
@@ -144,24 +175,26 @@ class SymbolString {
    * @return true if this instance is different from the other instance.
    */
   bool operator != (SymbolString& other) {
-    return m_unescapeState != other.m_unescapeState || m_data != other.m_data;
+    return m_isMaster != other.m_isMaster || m_data != other.m_data;
   }
 
   /**
-   * Compares this instance to the other instance while treating both as master data (i.e. starting with the master
-   * address and ending with the CRC).
+   * Compare the data in this instance to that of the other instance.
    * @param other the other instance.
-   * @return 0 if this instance is equal to the other instance (i.e. both escaped or both unescaped and same symbols),
-   * 1 if this instance is completely different to the other instance,
-   * 2 if this instance only differs from the other instance in the first byte (the master address).
+   * @return 0 if the data is equal,
+   * 1 if the data is completely different,
+   * 2 if both instances are a master part and the data only differs in the first byte (the master address).
    */
-  int compareMaster(SymbolString& other) {
-    if (m_unescapeState != other.m_unescapeState || m_data.size() != other.m_data.size()) {
+  int compareTo(SymbolString& other) {
+    if (m_data.size() != other.m_data.size()) {
       return 1;
     }
     if (m_data == other.m_data) {
       return 0;
     }
+    if (!m_isMaster) {
+      return 1;
+    }
     if (m_data.size() == 1) {
       return 2;
     }
@@ -172,15 +205,10 @@ class SymbolString {
   }
 
   /**
-   * Appends a the symbol to the end of the symbol string and escapes/unescapes it if necessary.
+   * Append a symbol to the end of the symbol string.
    * @param value the symbol to append.
-   * @param isEscaped whether the symbol is escaped.
-   * @param updateCRC whether to update the calculated CRC in @a m_crc.
-   * @return RESULT_OK if another symbol was appended,
-   * RESULT_IN_ESC if this is an unescaped instance and the symbol is escaped and the start of the escape sequence was
-   * received, RESULT_ERR_ESC if this is an unescaped instance and an invalid escaped sequence was detected.
    */
-  result_t push_back(const unsigned char value, const bool isEscaped = true, const bool updateCRC = true);
+  void push_back(const unsigned char value) { m_data.push_back(value); }
 
   /**
    * Return the number of symbols in this symbol string.
@@ -189,21 +217,39 @@ class SymbolString {
   unsigned char size() const { return (unsigned char)m_data.size(); }
 
   /**
-   * Return the calculated CRC.
+   * Return the offset to the first data byte DD.
+   * @return the offset to the first data byte DD.
+   */
+  unsigned char getDataOffset() const { return m_isMaster ? 5 : 1; }
+
+  /**
+   * Return the number of data bytes DD.
+   * @return the number of data bytes DD.
+   */
+  unsigned char getDataSize() const { return m_data.size() > (m_isMaster ? 4 : 0) ? m_data[m_isMaster ? 4 : 0] : 0; }
+
+  /**
+   * Return whether the byte sequence is complete with regard to the header and length field.
+   * @return true if the sequence is complete.
+   */
+  bool isComplete() {
+    size_t lengthOffset = (m_isMaster ? 4 : 0);
+    if (m_data.size() < lengthOffset + 1) {
+      return false;
+    }
+    return m_data.size() >= lengthOffset + 1 + m_data[lengthOffset];
+  }
+
+  /**
+   * Calculate the CRC.
    * @return the calculated CRC.
    */
-  unsigned char getCRC() const { return m_crc; }
+  unsigned char calcCrc() const;
 
   /**
    * Clear the symbols.
    */
-  void clear() { m_data.clear(); m_unescapeState = m_unescapeState == 0 ? 0 : 1; m_crc = 0; }
-
-  /**
-   * Clear the symbols and adjust the escape mode.
-   * @param escape true to set to an escaped instance, false to set to an unescaped instance.
-   */
-  void clear(const bool escape) { m_data.clear(); m_unescapeState = escape ? 0 : 1; m_crc = 0; }
+  void clear() { m_data.clear(); }
 
 
  private:
@@ -212,26 +258,13 @@ class SymbolString {
    * @param str the @a SymbolString to copy from.
    */
   SymbolString(const SymbolString& str)
-    : m_data(str.m_data), m_unescapeState(str.m_unescapeState), m_crc(str.m_crc) {}
+    : m_data(str.m_data), m_isMaster(str.m_isMaster) {}
 
-  /**
-   * Update the calculated CRC in @a m_crc by adding a value.
-   * @param value the (escaped) value to add to the calculated CRC in @a m_crc.
-   */
-  void addCRC(const unsigned char value);
-
-  /** the string of bus symbols. */
+  /** the string of unescaped symbols. */
   vector<unsigned char> m_data;
 
-  /**
-   * 0 if the symbols in @a m_data are escaped,
-   * 1 if the symbols in @a m_data are unescaped and the last symbol passed to @a push_back was a normal symbol,
-   * 2 if the symbols in @a m_data are unescaped and the last symbol passed to @a push_back was the escape symbol.
-   */
-  int m_unescapeState;
-
-  /** the calculated CRC. */
-  unsigned char m_crc;
+  /** whether this instance if for the master part. */
+  bool m_isMaster;
 };
 
 
diff --git a/src/lib/ebus/test/test_data.cpp b/src/lib/ebus/test/test_data.cpp
index d9fbe216..361d3e52 100644
--- a/src/lib/ebus/test/test_data.cpp
+++ b/src/lib/ebus/test/test_data.cpp
@@ -473,14 +473,14 @@ int main() {
     string check[5] = checks[i];
     istringstream isstr(check[0]);
     string expectStr = check[1];
-    SymbolString mstr(false);
+    SymbolString mstr(true);
     result_t result = mstr.parseHex(check[2]);
     if (result != RESULT_OK) {
       cout << "\"" << check[0] << "\": parse \"" << check[2] << "\" error: " << getResultCode(result) << endl;
       error = true;
       continue;
     }
-    SymbolString sstr(false);
+    SymbolString sstr;
     result = sstr.parseHex(check[3]);
     if (result != RESULT_OK) {
       cout << "\"" << check[0] << "\": parse \"" << check[3] << "\" error: " << getResultCode(result) << endl;
@@ -563,17 +563,17 @@ int main() {
     }
 
     ostringstream output;
-    SymbolString writeMstr(false);
-    result = writeMstr.parseHex(mstr.getDataStr(true, false).substr(0, 10));
+    SymbolString writeMstr(true);
+    result = writeMstr.parseHex(mstr.getDataStr().substr(0, 10));
     if (result != RESULT_OK) {
-      cout << "  parse \"" << mstr.getDataStr(true, false).substr(0, 10) << "\" error: " << getResultCode(result)
+      cout << "  parse \"" << mstr.getDataStr().substr(0, 10) << "\" error: " << getResultCode(result)
           << endl;
       error = true;
     }
-    SymbolString writeSstr(false);
-    result = writeSstr.parseHex(sstr.getDataStr(true, false).substr(0, 2));
+    SymbolString writeSstr;
+    result = writeSstr.parseHex(sstr.getDataStr().substr(0, 2));
     if (result != RESULT_OK) {
-      cout << "  parse \"" << sstr.getDataStr(true, false).substr(0, 2) << "\" error: " << getResultCode(result)
+      cout << "  parse \"" << sstr.getDataStr().substr(0, 2) << "\" error: " << getResultCode(result)
           << endl;
       error = true;
     }
@@ -621,9 +621,9 @@ int main() {
         error = true;
       } else {
         bool match = mstr == writeMstr && sstr == writeSstr;
-        verify(failedWriteMatch, "write", expectStr, match, mstr.getDataStr(true, false) + " "
-            + sstr.getDataStr(true, false), writeMstr.getDataStr(true, false) + " "
-            + writeSstr.getDataStr(true, false));
+        verify(failedWriteMatch, "write", expectStr, match, mstr.getDataStr() + " "
+            + sstr.getDataStr(), writeMstr.getDataStr() + " "
+            + writeSstr.getDataStr());
       }
     }
     delete fields;
diff --git a/src/lib/ebus/test/test_message.cpp b/src/lib/ebus/test/test_message.cpp
index 95e3ee6e..107a3772 100644
--- a/src/lib/ebus/test/test_message.cpp
+++ b/src/lib/ebus/test/test_message.cpp
@@ -260,7 +260,7 @@ int main() {
         } else if (mstrs[pos] != NULL) {
           delete mstrs[pos];
         }
-        mstrs[pos] = new SymbolString(false);
+        mstrs[pos] = new SymbolString(true);
         result = mstrs[pos]->parseHex(token);
         if (result != RESULT_OK) {
           cout << "\"" << check[0] << "\": parse \"" << token << "\" error: " << getResultCode(result) << endl;
@@ -277,7 +277,7 @@ int main() {
         } else if (sstrs[pos] != NULL) {
           delete sstrs[pos];
         }
-        sstrs[pos] = new SymbolString(false);
+        sstrs[pos] = new SymbolString();
         result = sstrs[pos]->parseHex(token);
         if (result != RESULT_OK) {
           cout << "\"" << check[0] << "\": parse \"" << token << "\" error: " << getResultCode(result) << endl;
@@ -292,7 +292,7 @@ int main() {
       if (mstrs[0] != NULL) {
         delete mstrs[0];
       }
-      mstrs[0] = new SymbolString(false);
+      mstrs[0] = new SymbolString(true);
       result = mstrs[0]->parseHex(check[2]);
       if (result != RESULT_OK) {
         cout << "\"" << check[0] << "\": parse \"" << check[2] << "\" error: " << getResultCode(result) << endl;
@@ -301,7 +301,7 @@ int main() {
       if (sstrs[0] != NULL) {
         delete sstrs[0];
       }
-      sstrs[0] = new SymbolString(false);
+      sstrs[0] = new SymbolString();
       result = sstrs[0]->parseHex(check[3]);
       if (result != RESULT_OK) {
         cout << "\"" << check[0] << "\": parse \"" << check[3] << "\" error: " << getResultCode(result) << endl;
@@ -419,7 +419,7 @@ int main() {
     }
     if (!message->isPassive() && (withInput || !decode)) {
       istringstream input(inputStr);
-      SymbolString writeMstr(false);
+      SymbolString writeMstr(true);
       result = message->prepareMaster(0xff, writeMstr, input);
       if (failedPrepare) {
         if (result == RESULT_OK) {
@@ -438,8 +438,8 @@ int main() {
       cout << "  \"" << inputStr << "\": prepare OK" << endl;
 
       bool match = writeMstr == *mstrs[0];
-      verify(failedPrepareMatch, "prepare", inputStr, match, mstrs[0]->getDataStr(true, false),
-          writeMstr.getDataStr(true, false));
+      verify(failedPrepareMatch, "prepare", inputStr, match, mstrs[0]->getDataStr(),
+          writeMstr.getDataStr());
     }
   }
 
diff --git a/src/lib/ebus/test/test_symbol.cpp b/src/lib/ebus/test/test_symbol.cpp
index 0ee67f63..2ae51aac 100644
--- a/src/lib/ebus/test/test_symbol.cpp
+++ b/src/lib/ebus/test/test_symbol.cpp
@@ -50,26 +50,32 @@ int main(int argc, char** argv) {
   SymbolString sstr(true);
 
   if (argc > 1) {
-    result_t result = sstr.parseHex(argv[1], true);
+    result_t result;
+    if (argc > 2 && strcmp("escaped", argv[1]) == 0) {
+      result = sstr.parseHexEscaped(argv[2]);
+    } else {
+      result = sstr.parseHex(argv[1]);
+    }
     if (result != RESULT_OK) {
       cout << "parse escaped error: " << getResultCode(result) << endl;
     } else {
-      unsigned char gotCrc = sstr.getCRC();
+      unsigned char gotCrc = sstr.calcCrc();
       cout << "calculated CRC: 0x"
           << nouppercase << setw(2) << hex << setfill('0')
               << static_cast<unsigned>(gotCrc) << endl;
     }
     return 0;
   }
+
   string gotStr, expectStr;
-  result_t result = sstr.parseHex("10feb5050427a915aa", false);
+  result_t result = sstr.parseHex("10feb5050427a915aa");
   if (result != RESULT_OK) {
-    cout << "parse escaped error: " << getResultCode(result) << endl;
+    cout << "parse unescaped error: " << getResultCode(result) << endl;
     error = true;
   } else {
-    gotStr = sstr.getDataStr(false, false), expectStr = "10feb5050427a90015a90177";
-    verify(false, "parse escaped", "10feb5050427a915aa", true, expectStr, gotStr);
-    unsigned char gotCrc = sstr.getCRC(), expectCrc = 0x77;
+    gotStr = sstr.getDataStr(), expectStr = "10feb5050427a915aa";
+    verify(false, "parse unescaped", "10feb5050427a915aa", true, expectStr, gotStr);
+    unsigned char gotCrc = sstr.calcCrc(), expectCrc = 0x77;
     ostringstream ostr;
     ostr << nouppercase << setw(2) << hex << setfill('0') << static_cast<unsigned>(expectCrc);
     expectStr = ostr.str();
@@ -77,19 +83,40 @@ int main(int argc, char** argv) {
     ostr << nouppercase << setw(2) << hex << setfill('0') << static_cast<unsigned>(gotCrc);
     gotStr = ostr.str();
     verify(false, "CRC", "10feb5050427a915aa", gotCrc == expectCrc, expectStr, gotStr);
-
-    gotStr = sstr.getDataStr(true, false), expectStr = "10feb5050427a915aa77";
-    verify(false, "unescape", "10feb5050427a915aa", true, expectStr, gotStr);
   }
 
-  sstr = SymbolString(false);
-  result = sstr.parseHex("10feb5050427a90015a90177", true);
+  sstr.clear();
+  result = sstr.parseHexEscaped("10feb5050427a90015a901");
   if (result != RESULT_OK) {
-    cout << "parse unescaped error: " << getResultCode(result) << endl;
+    cout << "parse escaped error: " << getResultCode(result) << endl;
     error = true;
   } else {
-    gotStr = sstr.getDataStr(true, false), expectStr = "10feb5050427a915aa77";
-    verify(false, "parse unescaped", "10feb5050427a90015a90177", true, expectStr, gotStr);
+    gotStr = sstr.getDataStr(), expectStr = "10feb5050427a915aa";
+    verify(false, "parse escaped", "10feb5050427a90015a901", true, expectStr, gotStr);
+    ostringstream ostr;
+    ostr << dec << static_cast<unsigned>(4);
+    expectStr = ostr.str();
+    ostr.str("");
+    ostr << dec << static_cast<unsigned>(sstr.getDataSize());
+    gotStr = ostr.str();
+    verify(false, "data size", "10feb5050427a90015a901", sstr.getDataSize() == 4, expectStr, gotStr);
+  }
+
+  sstr = SymbolString(); // slave
+  result = sstr.parseHexEscaped("0427a90015a901");
+  if (result != RESULT_OK) {
+    cout << "parse escaped error: " << getResultCode(result) << endl;
+    error = true;
+  } else {
+    gotStr = sstr.getDataStr(), expectStr = "0427a915aa";
+    verify(false, "parse escaped", "0427a90015a901", true, expectStr, gotStr);
+    ostringstream ostr;
+    ostr << dec << static_cast<unsigned>(4);
+    expectStr = ostr.str();
+    ostr.str("");
+    ostr << dec << static_cast<unsigned>(sstr.getDataSize());
+    gotStr = ostr.str();
+    verify(false, "data size", "0427a90015a901", sstr.getDataSize() == 4, expectStr, gotStr);
   }
 
   return error ? 1 : 0;