That topic doesn't really the wrc active diffs...
The system(s) has input from l/h & r/h wheel speed, front and rear prop speed, brake pressure and throttle position...it looks at pump pressure, and each diff pressure....
Centre diff controlller alters the characteristics the diff displays between the front and rear split, there are times when it is advantageous to lock and unlock the centre diff....handbraking, corner approach, corner exit etc...
Front diff...a little more interesting, we can alter the 'allowance' the amount the diff slips and the 'ramp' this alters the ramp angles in other words how the diff locks and unlock under acceleration and deacceleration.
The escort fully active car only has 2 active diffs, the front and centre. Only the suburu s11 had an active rear diff.
The system is fed by a two stage 100 bar pump, one stage does the power steering the other stage feeds the main valve block.
The main valve block controls the initial pressure bleeding back to the tank at 90 bar and distributing hyd fluid onto the 2 subs valve block...one for each diff.
The sub valve blocks house, pressure transducer, relief valve set at 15 bar and the control valve(generally called a rexroth valve), its these valves that are being controllled by its corresponding ecu (front & centre)
Thats it in a nutshell..most of the gear is in the pic on the bottom r/h side of the engine bay.
Ian