Whilst an Intel support team member may be able to give you a more accurate figure for hardware sync cable distance, I would speculate that since the cable would not be carrying high volumes of data bandwidth like the USB cable does, distance should be less than an issue (though signal will degrade over distance with most cables unless the signal is refreshed by running it through a boosting device such as a 'repeater').
Again, I will have to defer to Intel on answering the question about pins. Good luck!
This message was posted on behalf of Intel Corporation
Thank you for your interest on Intel® RealSense™ Technology.
The multi-camera hardware sync feature of the D400 series cameras is not yet enabled in hardware or firmware. The requirement for the feature will be to support more than 10 feet between cameras and only one pin from Master to Slave(s). We do not have a schedule for when this feature will be available.
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