ABS brakes
The antilock braking system is designed to prevent wheels locking or skidding, no matter how hard brakes are applied, or how slippery the road surface.
The primary components of the ABS braking system are:

The ECU is located inside the vehicle. It receives signals from the sensors in the circuit and controls the brake pressure at the road wheels according to the data analyzed by the Unit.
Hydraulic control unit or modulator

The location of the Hydraulic Control Unit, or Modulator, varies from manufacturer to manufacturer. Some locate it under the fender or hood.
It receives operating signals from the ECU to apply or release the brakes under ABS conditions.
Power booster & master cylinder assembly

The power booster and master cylinder assembly is mounted on the firewall and is activated when the driver pushes down on the brake pedal. It provides the power assistance required during braking.

The wheel sensor unit consists of a tooth rotor that rotates with the road wheels and a pick-up that is located in the wheel hub.