* Built-in or central vacuum cleaners move the suction motor and bag to a central location in the building and provide vacuum inlets at strategic places throughout the building: only the hose and pickup head need be carried from room to room; and the hose is commonly 8 m (25 ft) long, allowing a large range of movement without changing vacuum inlets. Plastic piping connects the vacuum outlets to the central unit. The vacuum head may either be unpowered or have beaters operated by an electric motor or air-driven motor. The dirt bag in a central vacuum system is usually so large that emptying or changing needs to be done less often, perhaps once per year. The central unit usually stays in "stand-by", and is turned on by a flick on the handle of the hose. Such a unit also produces greater suction than common vacuum cleaners, because a larger fan and more powerful engine can be used when they are not required to be portable.