A KNX building function is a set of Group Objects virtually linked together. Each such virtual link is a called a Group Address.
Only Objects with the same data length can be grouped together via a Group Address. A collection of Group Objects connected via the same Group Address is called a Group.
Within one Group there has to be at least one output Object and one input Object.
An input Object:
- its value comes via a Telegram from the bus
- represents e.g. a relay of a switch actuator
An output Object:
- its value is via a Telegram sent to the bus
- represents e.g. a push button rocker