+/**
+ * @brief Registers a callback function to detect the engine change.
+ * @since_tizen @if MOBILE 3.0 @elseif WEARABLE 2.3.2 @endif
+ * @privlevel public
+ * @privilege %http://tizen.org/privilege/recorder
+ *
+ * @param[in] stt The STT handle
+ * @param]in] callback The callback function to register
+ * @param[in] user_data The user data to be passed to the callback function
+ *
+ * @return 0 on success, otherwise a negative error value
+ * @retval #STT_ERROR_NONE Successful
+ * @retval #STT_ERROR_INVALID_PARAMETER Invalid parameter
+ * @retval #STT_ERROR_INVALID_STATE Invalid state
+ * @retval #STT_ERROR_NOT_SUPPORTED STT NOT supported
+ * @retval #STT_ERROR_PERMISSION_DENIED Permission denied
+ *
+ * @pre The state should be #STT_STATE_CREATED.
+ *
+ * @see stt_engine_changed_cb()
+ * @see stt_unset_engine_changed_cb()
+*/
+int stt_set_engine_changed_cb(stt_h stt, stt_engine_changed_cb callback, void* user_data);
+
+/**
+ * @brief Unregisters the callback function.
+ * @since_tizen @if MOBILE 3.0 @elseif WEARABLE 2.3.2 @endif
+ * @privlevel public
+ * @privilege %http://tizen.org/privilege/recorder
+ *
+ * @param[in] stt The STT handle
+ *
+ * @return 0 on success, otherwise a negative error value
+ * @retval #STT_ERROR_NONE Successful
+ * @retval #STT_ERROR_INVALID_PARAMETER Invalid parameter
+ * @retval #STT_ERROR_INVALID_STATE Invalid state
+ * @retval #STT_ERROR_NOT_SUPPORTED STT NOT supported
+ * @retval #STT_ERROR_PERMISSION_DENIED Permission denied
+ *
+ * @pre The state should be #STT_STATE_CREATED.
+ *
+ * @see stt_set_engine_changed_cb()
+*/
+int stt_unset_engine_changed_cb(stt_h stt);
+
+