<Tr> <Td> 3rd </Td> <Td> September 1, 2015 </Td> </Tr> <Tr> <Td> </Td> <Td> August 31, 2017 </Td> </Tr> <P> Nest is compatible with most standard HVAC systems that use central heating and cooling and uses industry standard connections to facilitate the control of these appliances . </P> <P> Nest consists of two primary pieces of hardware . The display contains the main printed circuit board (PCB) and rotating ring, and the base (pictured) houses the connection terminals, bubble level, and holes for wall anchors . Neither can function independently; if separated, the display becomes inactive until reconnected to the base . </P>

When did the 3rd generation nest come out