If a collision should occur, intelligent sensors trigger off the occupant restraint systems at the correct moment. The crash sensors must be able to detect a collision and convert it into corresponding signals within a matter of milliseconds. The nerve centre of this system is the airbag control unit, which decides whether to activate it and, depending on the nature and severity of the crash, deploys the airbags and belt tensioners. The control unit installed centrally in the vehicle contains sensors which determine the pattern and severity of a frontal or side impact at an early stage. Additional, remote crash sensors are also located on the vehicle to assist with crash detection