diff --git a/src/fsfw/devicehandlers/AssemblyBase.cpp b/src/fsfw/devicehandlers/AssemblyBase.cpp
index c29022e5..45f62ba0 100644
--- a/src/fsfw/devicehandlers/AssemblyBase.cpp
+++ b/src/fsfw/devicehandlers/AssemblyBase.cpp
@@ -196,7 +196,7 @@ ReturnValue_t AssemblyBase::checkModeCommand(Mode_t mode, Submode_t submode,
   }
 
   if ((mode != MODE_ON) && (mode != DeviceHandlerIF::MODE_NORMAL)) {
-    return INVALID_MODE;
+    return INVALID_MODE_RETVAL;
   }
 
   if (internalState != STATE_NONE) {
diff --git a/src/fsfw/devicehandlers/AssemblyBase.h b/src/fsfw/devicehandlers/AssemblyBase.h
index 3e235928..f6192533 100644
--- a/src/fsfw/devicehandlers/AssemblyBase.h
+++ b/src/fsfw/devicehandlers/AssemblyBase.h
@@ -53,7 +53,7 @@ class AssemblyBase : public SubsystemBase {
    * @param mode
    * @param submode
    * @return
-   *    - @c RETURN_OK if ok
+   *    - @c RETURN_OK if OK
    *    - @c NEED_SECOND_STEP if children need to be commanded again
    */
   virtual ReturnValue_t commandChildren(Mode_t mode, Submode_t submode) = 0;
@@ -120,8 +120,19 @@ class AssemblyBase : public SubsystemBase {
 
   virtual ReturnValue_t handleHealthReply(CommandMessage *message);
 
-  virtual void performChildOperation();
+  /**
+   * @brief Default periodic handler
+   * @details
+   * This is the default periodic handler which will be called by the SubsystemBase
+   * performOperation. It performs the child transitions or reacts to changed health/mode states
+   * of children objects
+   */
+  virtual void performChildOperation() override;
 
+  /**
+   * This function handles changed mode or health states of children
+   * @return
+   */
   bool handleChildrenChanged();
 
   /**
@@ -134,12 +145,31 @@ class AssemblyBase : public SubsystemBase {
 
   bool handleChildrenChangedHealth();
 
+  /**
+   * Core transition handler. The default implementation will only do something if
+   * #commandsOutstanding is smaller or equal to zero, which means that all mode commands
+   * from the #doPerformTransition call were executed successfully.
+   *
+   * Unless a second step was requested, the function will then use #checkChildrenState to
+   * determine whether the target mode was reached.
+   *
+   * There is some special handling for certain (internal) modes:
+   *  - A second step is necessary. #commandChildren will be performed again
+   *  - The device health was overwritten. #commandChildren will be called
+   *  - A recovery is ongoing. #checkAndHandleRecovery will be called.
+   */
   virtual void handleChildrenTransition();
 
   ReturnValue_t checkModeCommand(Mode_t mode, Submode_t submode, uint32_t *msToReachTheMode);
 
   virtual void startTransition(Mode_t mode, Submode_t submode);
 
+  /**
+   * This function starts the transition by setting the internal #targetSubmode and #targetMode
+   * variables and then calling the #commandChildren function.
+   * @param mode
+   * @param submode
+   */
   virtual void doStartTransition(Mode_t mode, Submode_t submode);
 
   virtual bool isInTransition();
diff --git a/src/fsfw/devicehandlers/DeviceHandlerBase.cpp b/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
index 03f8da54..6213ea86 100644
--- a/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
+++ b/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
@@ -403,7 +403,7 @@ ReturnValue_t DeviceHandlerBase::isModeCombinationValid(Mode_t mode, Submode_t s
         return INVALID_SUBMODE;
       }
     default:
-      return HasModesIF::INVALID_MODE;
+      return HasModesIF::INVALID_MODE_RETVAL;
   }
 }
 
diff --git a/src/fsfw/modes/HasModesIF.h b/src/fsfw/modes/HasModesIF.h
index 850d4349..d59e0294 100644
--- a/src/fsfw/modes/HasModesIF.h
+++ b/src/fsfw/modes/HasModesIF.h
@@ -13,7 +13,7 @@ class HasModesIF {
 
  public:
   static const uint8_t INTERFACE_ID = CLASS_ID::HAS_MODES_IF;
-  static const ReturnValue_t INVALID_MODE = MAKE_RETURN_CODE(0x01);
+  static const ReturnValue_t INVALID_MODE_RETVAL = MAKE_RETURN_CODE(0x01);
   static const ReturnValue_t TRANS_NOT_ALLOWED = MAKE_RETURN_CODE(0x02);
   static const ReturnValue_t IN_TRANSITION = MAKE_RETURN_CODE(0x03);
   static const ReturnValue_t INVALID_SUBMODE = MAKE_RETURN_CODE(0x04);
@@ -37,9 +37,13 @@ class HasModesIF {
   //! The device is powered and ready to perform operations. In this mode, no commands are
   //! sent by the device handler itself, but direct commands van be commanded and will be
   //! interpreted
-  static const Mode_t MODE_ON = 1;
+  static constexpr Mode_t MODE_ON = 1;
   //! The device is powered off. The only command accepted in this mode is a mode change to on.
-  static const Mode_t MODE_OFF = 0;
+  static constexpr Mode_t MODE_OFF = 0;
+
+  static constexpr Mode_t INVALID_MODE = -1;
+  static constexpr Mode_t UNDEFINED_MODE = -2;
+
   //! To avoid checks against magic number "0".
   static const Submode_t SUBMODE_NONE = 0;
 
diff --git a/src/fsfw/parameters/HasParametersIF.h b/src/fsfw/parameters/HasParametersIF.h
index 48557b4a..e95b69ab 100644
--- a/src/fsfw/parameters/HasParametersIF.h
+++ b/src/fsfw/parameters/HasParametersIF.h
@@ -66,7 +66,7 @@ class HasParametersIF {
    * @param newValues
    * @param startAtIndex Linear index, runs left to right, top to bottom for
    * matrix indexes.
-   * @return
+   * @return RETURN_OK if parameter is valid and a set function of the parameter wrapper was called.
    */
   virtual ReturnValue_t getParameter(uint8_t domainId, uint8_t uniqueIdentifier,
                                      ParameterWrapper *parameterWrapper,
diff --git a/src/fsfw/parameters/ParameterWrapper.cpp b/src/fsfw/parameters/ParameterWrapper.cpp
index 27552290..e772f1b6 100644
--- a/src/fsfw/parameters/ParameterWrapper.cpp
+++ b/src/fsfw/parameters/ParameterWrapper.cpp
@@ -211,9 +211,13 @@ ReturnValue_t ParameterWrapper::copyFrom(const ParameterWrapper *from,
   if (data == nullptr) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-    sif::warning << "ParameterWrapper::copyFrom: Called on read-only variable!" << std::endl;
+    sif::warning << "ParameterWrapper::copyFrom: Called on read-only variable or "
+                    "data pointer not set"
+                 << std::endl;
 #else
-    sif::printWarning("ParameterWrapper::copyFrom: Called on read-only variable!\n");
+    sif::printWarning(
+        "ParameterWrapper::copyFrom: Called on read-only variable "
+        "or data pointer not set\n");
 #endif
 #endif /* FSFW_VERBOSE_LEVEL >= 1 */
     return READONLY;
@@ -222,9 +226,9 @@ ReturnValue_t ParameterWrapper::copyFrom(const ParameterWrapper *from,
   if (from->readonlyData == nullptr) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-    sif::warning << "ParameterWrapper::copyFrom: Source not set!" << std::endl;
+    sif::warning << "ParameterWrapper::copyFrom: Source not set" << std::endl;
 #else
-    sif::printWarning("ParameterWrapper::copyFrom: Source not set!\n");
+    sif::printWarning("ParameterWrapper::copyFrom: Source not set\n");
 #endif
 #endif /* FSFW_VERBOSE_LEVEL >= 1 */
     return SOURCE_NOT_SET;
@@ -233,9 +237,9 @@ ReturnValue_t ParameterWrapper::copyFrom(const ParameterWrapper *from,
   if (type != from->type) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-    sif::warning << "ParameterWrapper::copyFrom: Datatype missmatch!" << std::endl;
+    sif::warning << "ParameterWrapper::copyFrom: Datatype missmatch" << std::endl;
 #else
-    sif::printWarning("ParameterWrapper::copyFrom: Datatype missmatch!\n");
+    sif::printWarning("ParameterWrapper::copyFrom: Datatype missmatch\n");
 #endif
 #endif /* FSFW_VERBOSE_LEVEL >= 1 */
     return DATATYPE_MISSMATCH;
@@ -245,9 +249,9 @@ ReturnValue_t ParameterWrapper::copyFrom(const ParameterWrapper *from,
   if (rows == 0 or columns == 0) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-    sif::warning << "ParameterWrapper::copyFrom: Columns or rows zero!" << std::endl;
+    sif::warning << "ParameterWrapper::copyFrom: Columns or rows zero" << std::endl;
 #else
-    sif::printWarning("ParameterWrapper::copyFrom: Columns or rows zero!\n");
+    sif::printWarning("ParameterWrapper::copyFrom: Columns or rows zero\n");
 #endif
 #endif /* FSFW_VERBOSE_LEVEL >= 1 */
     return COLUMN_OR_ROWS_ZERO;
diff --git a/src/fsfw/subsystem/SubsystemBase.cpp b/src/fsfw/subsystem/SubsystemBase.cpp
index f177ecd4..71c47c5f 100644
--- a/src/fsfw/subsystem/SubsystemBase.cpp
+++ b/src/fsfw/subsystem/SubsystemBase.cpp
@@ -33,8 +33,9 @@ ReturnValue_t SubsystemBase::registerChild(object_id_t objectId) {
       info.mode = MODE_OFF;
     }
   } else {
+    // intentional to force an initial command during system startup
     info.commandQueue = child->getCommandQueue();
-    info.mode = -1;  // intentional to force an initial command during system startup
+    info.mode = HasModesIF::UNDEFINED_MODE;
   }
 
   info.submode = SUBMODE_NONE;
diff --git a/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp b/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
index a0313f96..8e79bbc6 100644
--- a/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
+++ b/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
@@ -125,7 +125,7 @@ ReturnValue_t TestAssembly::isModeCombinationValid(Mode_t mode, Submode_t submod
         return INVALID_SUBMODE;
       }
   }
-  return INVALID_MODE;
+  return INVALID_MODE_RETVAL;
 }
 
 ReturnValue_t TestAssembly::initialize() {
diff --git a/tests/src/fsfw_tests/integration/devices/TestDeviceHandler.cpp b/tests/src/fsfw_tests/integration/devices/TestDeviceHandler.cpp
index 41098723..cd15d6e0 100644
--- a/tests/src/fsfw_tests/integration/devices/TestDeviceHandler.cpp
+++ b/tests/src/fsfw_tests/integration/devices/TestDeviceHandler.cpp
@@ -208,7 +208,7 @@ ReturnValue_t TestDevice::buildNormalModeCommand(DeviceCommandId_t deviceCommand
                                                  const uint8_t* commandData,
                                                  size_t commandDataLen) {
   if (fullInfoPrintout) {
-#if OBSW_VERBOSE_LEVEL >= 3
+#if FSFW_VERBOSE_LEVEL >= 3
 #if FSFW_CPP_OSTREAM_ENABLED == 1
     sif::info << "TestDevice::buildTestCommand1: Building normal command" << std::endl;
 #else
@@ -351,7 +351,7 @@ ReturnValue_t TestDevice::scanForReply(const uint8_t* start, size_t len, DeviceC
   switch (pendingCmd) {
     case (TEST_NORMAL_MODE_CMD): {
       if (fullInfoPrintout) {
-#if OBSW_VERBOSE_LEVEL >= 3
+#if FSFW_VERBOSE_LEVEL >= 3
 #if FSFW_CPP_OSTREAM_ENABLED == 1
         sif::info << "TestDevice::scanForReply: Reply for normal commnand (ID "
                   << TEST_NORMAL_MODE_CMD << ") received!" << std::endl;
@@ -678,7 +678,6 @@ ReturnValue_t TestDevice::getParameter(uint8_t domainId, uint8_t uniqueId,
         int32_t newValue = 0;
         ReturnValue_t result = newValues->getElement<int32_t>(&newValue, 0, 0);
         if (result == HasReturnvaluesIF::RETURN_OK) {
-#if OBSW_DEVICE_HANDLER_PRINTOUT == 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
           sif::info << "TestDevice" << deviceIdx
                     << "::getParameter: Setting parameter 1 to "
@@ -688,7 +687,6 @@ ReturnValue_t TestDevice::getParameter(uint8_t domainId, uint8_t uniqueId,
           sif::printInfo("TestDevice%d::getParameter: Setting parameter 1 to new value %lu\n",
                          deviceIdx, static_cast<unsigned long>(newValue));
 #endif /* FSFW_CPP_OSTREAM_ENABLED == 1 */
-#endif /* OBSW_DEVICE_HANDLER_PRINTOUT == 1 */
         }
       }
       parameterWrapper->set(testParameter1);
@@ -702,7 +700,6 @@ ReturnValue_t TestDevice::getParameter(uint8_t domainId, uint8_t uniqueId,
             newValues->getElement<float>(newVector + 2, 0, 2) != RETURN_OK) {
           return HasReturnvaluesIF::RETURN_FAILED;
         }
-#if OBSW_DEVICE_HANDLER_PRINTOUT == 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
         sif::info << "TestDevice" << deviceIdx
                   << "::getParameter: Setting parameter 3 to "
@@ -715,7 +712,6 @@ ReturnValue_t TestDevice::getParameter(uint8_t domainId, uint8_t uniqueId,
             "[%f, %f, %f]\n",
             deviceIdx, newVector[0], newVector[1], newVector[2]);
 #endif /* FSFW_CPP_OSTREAM_ENABLED == 1 */
-#endif /* OBSW_DEVICE_HANDLER_PRINTOUT == 1 */
       }
       parameterWrapper->setVector(vectorFloatParams2);
       break;