Because a Roomba's circular shape prevents it from sitting flush against walls, the long bristles extend outward to push dirt into the main suction path.

Cliff sensors on the robot's underbelly continuously bounce infrared signals off the floor. If the signal fails to return quickly, the vacuum immediately stops.

These battery-powered towers shoot an invisible infrared line across a doorway. A sensor on top of the Roomba detects this barrier and forces the robot to turn away.