The Remote Terminal Unit is initially interrogated with what DNP3 terms an "Integrity Poll" (a combined Read of Class 1, 2, 3 and 0 data). This causes the Remote Terminal Unit to send all buffered events and also all static point data to the Master station. Following this, the Master polls for the event data by reading Class 1, Class 2 or Class 3. The reading of the classes can all be performed together or each class can be read at a different rate, providing a mechanism to create different reporting priorities for the different classes. After an Integrity Poll, only significant data changes are sent. This can result in significantly more responsive data retrieval than polling everything, all the time, irrespective of whether it has changed significantly.