On a hydraulic power steering the steering gear input shaft is connected to the drive pinion via a torsion bar. The torsion bar twists under the effect of the steering torque applied by the driver.
The twist of the torsion bar is measured by the electrical power steering (ES) torque sensor (A91b1) without contact and is converted into a voltage signal.
The voltage serves the electrical power steering (ES) control unit (N68) as an input signal.