<P> The Roomba is not designed for deep - pile carpet . Also, the first - and second - generation Roombas can get stuck on rug tassels and electrical cords . The third - generation is able to reverse its brushes to escape entangled cords and tassels . Additionally, all models are designed to be low enough to go under a bed or most other items of furniture . If at any time the unit senses that it has become stuck, no longer senses the floor beneath it, or it decides that it has worked its way into a narrow area from which it is unable to escape, it stops and sounds an error to help someone find it . Early models use only flashing lights to indicate specific problems, while later models use a synthesized voice to announce a problem and a suggested solution . </P> <P> Battery reliability is a frequently mentioned complaint on customer review websites . Battery replacements from iRobot cost a significant fraction of the purchase price of a new Roomba, though compatible third - party batteries are available at a lower price . The iRobot customer support website offers advice on maximizing battery performance and longevity . </P> <P> Introduced in September 2002, the first - generation Roomba had three buttons for room size . The first - generation units comprised the original silver - colored Roomba, the blue Roomba Pro, and the maroon Roomba Pro Elite . The later two models included additional accessories, but all three used the same core robot and cleaning system . The second - generation Roombas ("Discovery", later called 400 series) replaced their predecessors in July 2004, added a larger dust bin, improved software that calculates room size, dirt detection, and fast charging in the home base . </P> <P> Roomba budget models (Dirt Dog and Model 401) used a simplified interface (a single button) and lacked some of the software - controlled flexibility of other versions . They were less expensive models intended for first - time purchasers . The Roomba Dirt Dog contained sweeping brushes and a larger dust bin, but lacked the vacuum motor, using the space that would be required for the vacuum for additional dust bin volume . It was designed for a home shop or garage environment . The Roomba Model 401 was similar but had a standard - size dust bin and vacuum system . The Dirt Dog was discontinued in 2010 . </P>

Where is the model number on a roomba