How is the anti-lock braking system (ABS) activated in a 1990 Audi 80?

I am curious to know the exact mechanism by which the anti-lock braking system (ABS) is activated in a 1990 Audi 80

To activate the ABS, the brake pedal must be depressed at a certain rate, triggering the wheel speed sensors to send signals to the ABS control unit. The unit then modulates the brake pressure to prevent the wheels from locking up.

The ABS is activated by the hydraulic control unit, which receives signals from the wheel speed sensors. It then uses valves to adjust the brake pressure and prevent wheel lock-up.

The ABS is activated through a complex system of sensors, valves, and electronic control units. If you want a more detailed explanation, I suggest checking out the Audi 80 owner's manual.