Preston digital follow focus camera run function incompatibility with Arri SR2

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2006Follow Focus forum

20 years old. Gear and prices may have changed since.

DisputedParticipants disagreed and reached no conclusion. Read the findings as positions, not as an answer.

The Preston digital 2 follow focus system's camera run function failed to work with an Arri SR2 camera but functioned properly with an Arri SR3 and other camera models.
The SR2 and SR3 differ in their start-stop connector types: the SR2 uses an 11-pin connector with a permanent contact switch, while the SR3 uses a more modern 3-pin momentary switch design.
Different camera models have varying wiring configurations on their 11-pin connectors, and the Preston's electronic switch may require reversed polarity to function correctly depending on which pin carries positive and negative voltage.
Some SR2 cameras have multiple 11-pin ports, and not all ports may be wired identically for start-stop functionality.
Splitter boxes for connecting multiple devices to a single port may not function properly unless all pins are fully wired by the manufacturer.

The issue was observed on SR2 units from at least one rental house but specifics about camera serial numbers or modification history were not documented.
Testing was limited to three camera models mentioned: SR2, SR3, Arri 3, and one 35BL unit.
The root cause was not definitively identified during the discussion; the user planned further testing but no resolution was confirmed in the thread.
Power supply voltage variations (12V versus 24V) and cable rewiring did not resolve the problem, but the exact wiring configuration of the problematic SR2 unit was not fully investigated.