With the new series of ThinkPads IBM introduced the Active Protection System (APS) in 2003. The APS is a protection system for the ThinkPad's internal harddrive. A sensor inside the ThinkPad recognizes when the notebook is accelerated. A software applet then is triggered to park the harddisk. This way the risk of data loss in case of when the notebook is dropped is significantly reduced since the read/write head of the harddrive is parked and hence can't crash onto the platter when the notebook drops onto the floor.