Heavy equipment refers to heavy-duty vehicles, specially designed for executing construction tasks, most frequently, ones involving earth moving. They are also known as construction equipment, earth movers, engineering vehicles, or just plain equipment. They usually comprise five equipment systems: implement, traction, structure, power train, control and information. Through the mechanical advantage of a simple machine, the ratio between input force applied and force exerted is multiplied. Currently most equipment use hydraulics as a primary source of transferring power.