Compound lever sudden movement of the key. The earliest remaining writings regarding levers date from the 3rd century BC and were provided by Archimedes. ""Give me a place to stand, and I shall move the earth with a lever"" is a remark attributed to Archimedes, who formally stated the correct mathematical principle of levers (quoted by Pappus of Alexandria). The idea of the compound lever is attributed to the Birmingham inventor John Wyatt in 1743, when he designed a weighing machine that used four compound levers to transfer a load from a weighing platform to a central lever from which the weight
Lever frame Each lever is engaged with the interlocking logic such that movement of the lever is only possible when all necessary conditions are met. The interlocking may be mechanical, electric (via solenoids) or both with the apparatus being mounted horizontally behind the lever frame or vertically below it. To assist the operator in determining their functions, each lever in a frame will generally be uniquely labelled, one common method being to number the levers in order from left to right. A lever's identification may be painted on its side or engraved on a badge or plate fitted either to the lever