Lever the power out, and the ratio of output to input force is given by the ratio of the distances from the fulcrum to the points of application of these forces. This is known as the "law of the lever." The mechanical advantage of a lever can be determined by considering the balance of moments or torque, "T", about the fulcrum. where F is the input force to the lever and F is the output force. The distances "a" and "b" are the perpendicular distances between the forces and the fulcrum. Since the moments of torque must be balanced, formula_3 .
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,