The airbags in the vehicle are controlled by a central airbag control unit. The ACU monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, side (door) pressure sensors,wheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors. The signals from the various sensors are fed into the airbag control unit, which determines from them the angle of impact, the severity, or force of the crash, along with other variables.