code: public static String getErrorMessage(final int errorCode)
  	{
  		if (errorCode < 0)
  			throw new KNXIllegalArgumentException("error code has to be >= 0");
  		if (errorCode > errors.length - 1)
  			return "unknown error code";
  		return errors[errorCode];
  	}
docs: Returns a descriptive error message for the supplied error code parameter.
  <p>
  If the error code is not known, the string "unknown error code" is returned.
  
  @param errorCode error code to get message for, <code>0 &le; errorCode</code>
  @return error status message as string