<P> Some higher - end 500, 700 and 800 series robots are compatible with Virtual Wall Lighthouses, which use radio signals to communicate . These more advanced accessories confine a Roomba to a fixed area to be cleaned, yet allow the robot to later proceed to the next space which needs to be cleaned . </P> <P> There are several types of dust and debris collection bins for the 500 series robots . The standard vacuum bin incorporates a squeegee vacuum . The high - capacity sweeper bin does not include a vacuum, but has greater debris capacity . The Aerovac Bin directs suction airflow through the main brushes instead of using a squeegee, which is thought to keep the brushes cleaner . </P> <P> All Roomba models can be operated by manually carrying them to the room to be cleaned and pressing a button . Later models introduced several additional operating modes . "Clean" mode is the normal cleaning program, starting in a spiral and then following a wall, until the room is determined to be clean . "Spot" mode cleans a small area using an outward - then - inward spiral . "Max" mode runs the standard cleaning algorithm until the battery is depleted . "Dock" mode, introduced with the third generation, instructs the robot to seek a charging base for recharging . The availability of the modes varies by model . </P> <P> The robot's bumper allows it to sense when it has bumped into an obstacle, after which it will reverse or change paths . The third - and fourth - generations, which move faster than previous models, have additional forward - looking infrared sensors to detect obstacles . These slow down the robot when nearing obstacles, to reduce its force of impact . This technology is also able to distinguish between soft and solid barriers . After enough time cleaning or as the battery runs down, the Roomba will either search for and dock with the base, or stop where it is . </P>

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