Lever fulcrum to where the output force is applied (point "B"), then the lever amplifies the input force. On the other hand, if the distance "a" from the fulcrum to the input force is less than the distance "b" from the fulcrum to the output force, then the lever reduces the input force. The use of velocity in the static analysis of a lever is an application of the principle of virtual work. A lever is modeled as a rigid bar connected to a ground frame by a hinged joint called a fulcrum. The lever is operated by applying an input
Lever frame or behind it. This may be accompanied by a description of the lever's function. Usually, a large track diagram is positioned within easy view of the operator, which clearly shows each lever number adjacent to symbols representing the items of equipment that they operate. Levers are commonly coloured according to the type of equipment they control, the code of colours varying between different railway administrations. For example, in British practice, the following code generally applies: a red lever controls a stop signal or shunt signal, a yellow lever controls a distant signal, a black lever controls a set of points,