The Hub is the nerve centre of the whole system.
The Hub box distributes power and communications to and from the servo axes, the camera, and the Pocket PC (PPC). It also interfaces to an ARRI RCU for speed ramping, and to an ARRI SFC (Single Frame Controller), for time-lapse shooting with an ARRI 435.
In addition to its role as the communication and power hub of the system, the hub also provides simulation of camera frame pulses. The system can either use the camera's frame pulses to synchronize all servo axes, or the hub will generate its own frame pulses at any speed (within the camera's range) set by the PPC. This allows moves to be recorded and or played back without running the camera.
When a move is played back in time-lapse mode, the Hub also generates the time lapse interval between frames, and fires the camera (SFC for a 435) to take the frame.
A bloop light is driven by the Hub to synchronize the first frame of a recording and playback.
Both recording and playback can be triggered by an external input, typically to allow synchronization with video playback systems. Moves are triggered accurately on the next frame pulse after the trigger input.