•  The steering angle sensor has a sensor unit with a photo transistor positioned opposite an LED straddling a slitted disc that moves together with the steering wheel.

•  As the disc moves with the steering wheel, the LED light received by the photo transistor varies due to the slits on the disc. The photo transistor outputs an on signal when it receives light and an off signal when the light is blocked. The EHPAS control module calculates the steering angle and speed based on the phase difference between sensor A and B outputs.